This session will cover aspects ranging from observed and projected climate change to consequences for forest ecosystems and their assessment, spanning a range of scales, biomes and conditions. In particular, we welcome submissions on the following subjects:
• Evaluation of the effects of natural and anthropogenic disturbances on forest productivity, health and growth.
• Multidisciplinary approaches for monitoring tree vulnerability at the local, regional and global scales.
• Mapping and forecasting forest mortality and dieback phenomena under different climate and land-use scenarios.
• Modelling climate and environmental influences on forest and tree vigor and growth at different scales and considering different methods or processes (e.g., wood formation, leaf phenology, shoot growth, canopy greenness).
• Vulnerability of old-growth and mountain forests and also old trees to climate change.
• Assessing forest resilience to drought and other extreme climate events (e.g., frosts).
• Using adaptive management to buffer forest vulnerability.
• Methods and tools for decision support and adaptation support in the forestry sector considering multiple stakeholders and multifunctional perspectives.
Orals: Thu, 1 May | Room N1
The stability of forest ecosystems depends on their capacity to withstand and recover from natural and anthropogenic perturbations, i.e., their resilience. Experimental evidence of sudden increases in tree mortality is raising concerns about variation in forest resilience, yet little is known about how it is evolving in response to climate change. Here, we integrate satellite-based vegetation indices with machine learning to show how forest resilience, quantified in terms of critical slowing down indicators, has changed over the period 2000-2020. We show that tropical, arid and temperate forests are experiencing a significant decline in resilience, likely related to the increasing water limitations and climate variability. In contrast, boreal forests show an increasing trend in resilience, likely benefitting from warming and CO2 fertilization, which may outweigh the adverse effects of climate change. These patterns emerge consistently in both managed and intact forests corroborating the existence of common large-scale climate drivers. Reductions in resilience are statistically linked to abrupt declines in forest productivity, occurring in response to a slow drifting toward a critical resilience threshold. Approximately 23% of intact undisturbed forests, corresponding to 3.32 Pg C of gross primary productivity, have already reached a critical threshold and are experiencing a further degradation in resilience. Together, these signals reveal a widespread decline in forests’ capacity to withstand perturbation that should be accounted for in the design of land-based mitigation and adaptation plans.
How to cite: Forzieri, G., Dakos, V., McDowell, N., Alkama, R., and Cescatti, A.: Emerging signals of declining forest resilience under climate change, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12937, https://doi.org/10.5194/egusphere-egu25-12937, 2025.
Recently, several studies provided model-based insights on how climate change may alter European tree-species distributions. Yet, none of those have considered the implications of a collapse of the Atlantic Meriodional Overturning Circulation (AMOC), even though recent research indicates an already declining AMOC and a significant chance of a complete shutdown within the 21st century. Since an AMOC collapse results in cooler and drier climatic conditions across Europe that differ significantly from current climate model projections we need to increase our understanding of the impacts of an AMOC collapse on European forests.
Under this framework, we projected future tree-species distributions across Europe for various CMIP6 scenarios, emphasizing on differences between scenarios with an active vs. an inactive AMOC. In particular, we trained climate envelope models for the 24 most abundant European tree species and performed model simulations with quantile-mapped climate projections at a very high spatial resolution of 1 km². To quantify the effects of an AMOC collapse, we compared projections based on regular CMIP6 scenarios (SSPs 1-2.6, 2-4.5, 5-8.5, 10 different models) with such resembling an AMOC collapse. In our statistical evaluation, we emphasized on relative changes in abundance probability, redistribution of species-specific core areas, and the diversity of forest’s tree-species portfolios.
Our results show a stark contrast between the scenarios that account for an AMOC collapse and the control scenarios across all considered SSPs. Specifically, we observed an increase in abundance probabilities of selected tree species in Central Europe and the Mediterranean, while abundance probabilities in Scandinavia decreased substantially, indicating local extinction of the dominant tree species Norway spruce and Scots pine. Taken together, our study highlights a diverse picture of an AMOC collapse with catastrophic impacts on Europe’s boreal forests.
How to cite: Buras, A., Rammig, A., and Heubel, S.: Projecting the impact of a collapsing Atlantic Meridional Overturning Circulation on European tree-species distributions , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3275, https://doi.org/10.5194/egusphere-egu25-3275, 2025.
European forests are increasingly vulnerable to climate change, with mortality rates rising across major tree species. Using data from the French National Forest Inventory (NFI), we examined mortality trends between 2014 and 2023 for over 600,000 trees spanning 52 species and major climate zones. Mortality rates significantly increased, particularly in northeastern France matching spatial patterns of warming temperatures and declining precipitation. Employing explainable machine learning, we identified forest demography (e.g., tree size, competition) and climate anomaly variables as the primary contributors to a tree’s probability of dying. In addition to warmer, drier summers being associated with higher mortality through intensified drought stress, an unexpected contributor to mortality was the occurrence of warmer and wetter springs. This result is consistent with the ‘structural overshoot’ hypothesis that rapid canopy growth during favorable warmer, wetter springs predisposes trees to hydraulic failure during subsequent droughts. Species-specific analysis revealed diverse responses, with drought-adapted Mediterranean tree species showing a lower risk of structural overshoot than temperate trees. Different drought stress mechanisms revealed by our empirical data appear to play compounding roles, with emerging drivers of mortality being chronic dryness (possibly depleting tree reserves and weakening them), acute droughts (causing hydraulic failure), and insufficient post-drought rainfall (hindering recovery). Milder winters and springs also contributed to increased mortality, likely because they enhanced pest survival and disrupted winter dormancy, further exerting stress. With rainfall projected to shift from summer to winter and rising temperatures, future droughts are expected to become increasingly harmful. These findings underscore the urgent need for adaptive policies to safeguard forest ecosystems and their essential functions.
How to cite: Schneider, P., Pellissier-Tanon, A., Zhou, C., Ciais, P., Piedallu, C., Viana-Soto, A., Lever, J., and Gessler, A.: Flush to Crush: The Paradox of Favourable Springs Leading to Tree Mortality, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7913, https://doi.org/10.5194/egusphere-egu25-7913, 2025.
The increasing frequency and intensity of droughts and heat waves driven by climate change have led to a significant increase in tree mortality worldwide. However, the lack of accurate and consistent data on the location, timing, species, and structure of dead trees across vast geographical areas limits our understanding of climate-induced tree mortality. Furthermore, standing dead and dying trees are crucial indicators of forest health and biodiversity but are often overlooked in existing forest resource mapping systems.
To address this, we present novel advancements in mapping individual tree mortality events using high-resolution (≤ 0.5 m) multi-temporal Earth Observation data, including both satellite and aerial imagery, combined with deep learning techniques. Our approach represents the first steps towards building an open large-scale database of individual tree mortality events across time. We have trained several U-Net-based deep learning models for detecting individual dead and dying trees from a wide array of imagery, including high-resolution aerial and satellite imagery from boreal, temperate, and Mediterranean forest biomes, enabling the creation of wall-to-wall datasets on tree mortality at national scales. We show results from the first nationwide individual tree mortality mapping, demonstrating the accuracy of sub-meter resolution satellite imagery in providing annual tree mortality data. We also discuss the challenges and limitations associated with detecting and characterizing detected dead trees across entire countries.
Currently, our database already includes tree mortality data for 10 years in boreal, temperate, and Mediterranean forest biomes for several countries. We welcome scientists from around the globe to contribute to creating a database on individual tree mortality events to support a wide range of tree mortality data needs in different scientific disciplines.
How to cite: Junttila, S., Rahman, A., Heinaro, E., Polvivaara, A., Ahishali, M., Blomqvist, M., Yrttimaa, T., Rehush, N., Holopainen, M., Honkavaara, E., Hyyppä, J., Laukkanen, V., Vastaranta, M., Peltola, H., Mosig, C., Kattenborn, T., Ait, K., Svoboda, M., Cheng, Y., and Horion, S.: Mapping individual tree mortality using sub-meter Earth observation data: Advances toward a large-scale global database, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18669, https://doi.org/10.5194/egusphere-egu25-18669, 2025.
Japan has several long-term forest monitoring datasets from publications and national programmes such as the Monitoring 1000 sites and the JaLTER network. These various datasets were recently collected and organised for ease of access, resulting in observations from almost 200 plots. We analysed these data to observe long-term forest changes and assess the major factors affecting the functional composition of species over time. Tree species were classified into four plant functional groups (PFTs): boreal conifer species (BC), temperate conifer species (TC), deciduous broadleaf species (DB), and evergreen broadleaf species (EB). These PFTs can be ordered based on their latitudinal range and corresponding climatic preferences, so that from the north to the south dominance is shifting from the cold-tolerant BCs to DBs, then to warm-favouring TCs, and finally to warm-climate EBs. However, the traditional species composition might be affected by the changing climate, causing a disalignment between the functional composition of mature trees and saplings. We hypothesised that the sapling composition might shift towards warmer PFTs than those found among the mature trees, i.e.: DB saplings appearing in traditionally BC forests, and TC and EB saplings appearing in traditionally DB forests. To test this hypothesis, we analaysed species-level data from long-term forest plots with at least 20 years of observation, covering the northern-southern latitudinal range of Japan. We found that while not all plots displayed a change in PFT composition, there were many that did show a characteristic change. These changes could be seen in the increased overlap of PFTs among saplings from originally distinct forest plots, and also in the different trends of relative abundance among PFTs. However, the change could not be clearly contributed to the impact of climate change, as anthropogenic and other factors of natural disturbance had also a pronounced role in shaping the species composition of the forests. In addition to slow changes caused directly by climate change, sudden changes, attributed to herbivory, pest outbreaks, and other extreme disturbances indirectly related to climate change, were also common among the plots. Our results indicate that climate change affects forest ecosystems both directly and indirectly, with relatively quick changes once a tipping point is reached. These findings can aid future management practices to preserve the diversity and ecosystem services of the forests across a wide latitudinal range in Japan.
How to cite: Végh, L., Takeuchi, Y., and Yoshikawa, T.: Changes in the functional species composition of forests across a wide latitudinal range in Japan, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8407, https://doi.org/10.5194/egusphere-egu25-8407, 2025.
As a result of climate change, disturbances regimes are changing around the globe. This is challenging the sustainable provisioning of ecosystem services to society. Understanding the disturbance resilience of forest ecosystems is crucial for forest management, yet estimating resilience in the field remains difficult. A rapid assessment of important indicators associated with failing tree regeneration post disturbance would help managers to prioritize efforts on disturbed areas.
Here, we propose an innovative approach for resilience assessment leveraging recent advancements in computer vision and deep neural networks (DNNs) to estimate post disturbance resilience based on indicators derived from GoPro-photos taken in the field. We build on an extensive empirical dataset of post-disturbance development pathways (resilience, restructuring, replacement or reassembly) derived across four forest types (spruce, beech, pine, oak) in Bavaria. We use these empirical data in combination with computer vision models trained on images collected from disturbed plots and their surroundings (N=1240 images) to predict indicators related to ground cover (e.g., percent covered by grass) and forest structure (e.g., deadwood, structural complexity). These computer-vision derived indicators were subsequently related to field-based assessments to test their suitability of detecting disturbances and disturbance strength as well as their ability of predicting post-disturbance pathways. Preliminary results demonstrate a medium to strong ability of computer vision-derived indicators to correctly detect disturbances and predict post-disturbance forest development.
Our findings suggest that computer-vision methods offer a low-cost, low-threshold tool to support forest managers in prioritizing post-disturbance management decisions.
How to cite: Hochholzer, K., Potterf, M., Seidl, R., and Rammer, W.: Computer-vision based automated assessment of post-disturbance forest resilience, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4276, https://doi.org/10.5194/egusphere-egu25-4276, 2025.
Drought is increasingly recognized as a critical driver of forest dynamics, altering tree species' dominance, growth, and survival. To better understand these dynamics, we tested a recently developed predisposing-inciting (PI) framework for drought-related tree mortality within the forest gap model ForClim v4.1, focusing on two key European species: European beech (Fagus sylvatica) and Norway spruce (Picea abies). To better capture contributing factors of drought-related stress, we also developed a bark beetle module for Norway spruce to better account for interactions between abiotic and biotic stress factors.
Our study addressed three hypotheses:
- The PI framework remains effective across broader ecological and climatic ranges beyond its initial application.
- Soil water holding capacity (AWC) exerts a significant influence on drought-induced mortality, complementing climatic drivers.
- Reduced soil heterogeneity amplifies mortality risks by limiting microsite variability, thereby exacerbating drought stress.
We conducted simulations across hundreds of ICP-Level II sites in Germany, spanning diverse climate and soil gradients.
Results indicate that ForClim can reproduce general patterns of drought-induced mortality, though mismatches in magnitude and trends highlight areas for improvement. Discrepancies were attributed to sparse mortality data, the drought sensitivity of the bark beetle submodule, and limited regional calibration.
Soil water availability emerged as a critical driver of drought resilience. Sites with low AWC experienced significantly elevated mortality rates, while high AWC provided a buffering effect, bringing modeled outcomes closer to observed data. Furthermore, soil heterogeneity played a mitigating role: sites with uniform soils exhibited higher mortality risks, thus emphasizing the importance of spatial variability in dampening drought impacts.
This study underscores the value of process-based models like ForClim in disentangling the mechanisms underlying forest vulnerability and drought-induced mortality. However, improvements such as finer-resolution mortality and crown condition data, as well as regional model calibration, are essential to enhance predictive accuracy. By advancing our understanding of drought-induced mortality, these findings contribute to better forecasting and management of forest resilience under current and future climate scenarios.
How to cite: Marano, G., Hiltner, U., Knapp, N., and Bugmann, H.: Simulating drought-driven mortality of European Beech and Norway Spruce in German forests:insights on predisposing, inciting and contributing factors, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20770, https://doi.org/10.5194/egusphere-egu25-20770, 2025.
The Amazon forest has traditionally served as an important carbon sink, but mounting evidence suggests that it is transitioning into a carbon source. This shift is driven by both local and regional disturbances, including extreme drought events. To anticipate how the Amazon may respond to climate change, we analysed its response to recurrent extreme drought events using satellite data.
Our study explored the concept of stability through multiple lenses. We first examined how the Amazon forest responded to individual droughts, considering the legacy effects of preceding droughts and wet periods. Then, we also quantified the stability of the Amazon in response to cumulative drought impacts, assessing its potential transition to a degraded ecosystem when a critical precipitation threshold is crossed.
We found that more severe droughts caused a more pronounced decrease in canopy vitality within a year following the event. Moreover, the response of the Amazon was influenced by legacy effects: recent dry periods reduced the forest’s stability, while preceding wet events mitigated the drought impact. Increased drought frequency also led to signs of critical slowing down in the Amazon forest vegetation. Regions experiencing more intense and prolonged droughts were more vulnerable to this phenomenon, although the severity of impacts varied regionally.
In summary, while the Amazon forest has shown resilience to past extreme drought events, the predicted increase in drought intensity and duration is likely to amplify critical slowing down across the forest, particularly in the more seasonal southern regions. The intricate connection between the Amazon forest vegetation and its water sources could trigger cascading effects, leading to further stability loss with global repercussions.
How to cite: Van Passel, J., Somers, B., Van Meerbeek, K., De Keersmaecker, W., and Bernardino, P.: How repeated droughts impact the stability of the Amazon forest, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16154, https://doi.org/10.5194/egusphere-egu25-16154, 2025.
One of the most pervasive drought impacts on tropical forests is increased tree mortality. While satellite imagery can detect large-scale drought-induced tree mortality events, it cannot detect individual tree mortality that is scattered in space and lagged in time. To estimate the latter mortality drought-induced growth anomalies from tree-ring data can be combined with plot-based growth-mortality associations. Here we combine data from 158 globally distributed tree-ring chronologies with plot-based growth-mortality associations to present a first pantropical estimate of drought-associated mortality.
For the 10% driest years, our pantropical estimate of angiosperm lowland tree mortality is 0.1% y-1 (confidence interval: 0.08-0.15%) on top of 1% y-1 background mortality. This value is slightly higher for the 5% driest years.
Direct empirical associations between growth and mortality for tree-ring forming species are needed to refine this estimate. Tree mortality likely increases under ongoing climate change, leading to reduced carbon residence time in tropical forests.
How to cite: Zuidema, P., Babst, F., Groenendijk, P., Trouet, V., and Rahman, M. and the Tropical Tree-ring Network: Pantropical drought-induced tree mortality: a first estimate using tree-ring and plot data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9282, https://doi.org/10.5194/egusphere-egu25-9282, 2025.
Climate change impacts European forests both directly, through shifts in temperature and precipitation, and indirectly, by increasing the frequency and intensity of extreme weather events such as droughts. As a result, understanding forests’ capacity to sustain their functions under stress has become a critical research area. This capacity is often represented by the variability of ecosystem functional properties (EFP), derived from eddy covariance flux measurements, with lower variability indicating higher resistance to stress and greater resilience to drought. EFP variability is hypothesized to be influenced by meteorology, soil conditions, and forest structure. Unravelling the specific role of forest structure in this variability could inform forest management strategies to enhance future resilience.
Previous studies have focused either on individual ecosystem functions or few site samples, not allowing to fully understand the drivers of EFP. Within the EU Horizon project CLIMB-FOREST, we collected data on CO₂, H₂O, and energy fluxes from 59 European forests to calculate key EFPs: underlying water use efficiency (uWUE), photosynthetic capacity (GPPsat), Bowen ratio (β), canopy conductance (Gs), and albedo (α). These were analyzed for their distribution and variability, then correlated with forest structure metrics such as forest type, management regime, stand age, canopy height, and species diversity.
Our analysis revealed that deciduous broadleaf forests (DBF) exhibited higher uWUE, GPPsat, and Gs compared to evergreen needleleaf forests (ENF) and mixed forests (MF), but also displayed the greatest variability in uWUE, GPPsat, and β. Variability in GPPsat decreased with increasing canopy height, with a slight upswing in stands exceeding 30 meters. Albedo variability was highest in young forests (0–49 years) and lowest in forests with an age between 100–149 years. However, no significant correlations emerged between forest structure variables and EFP variability. The limited availability of structural data likely constrained our correlation analysis, potentially masking significant trends.
To address these limitations, we aim to expand the dataset and apply advanced correlation techniques to better identify the drivers of EFP variability.
How to cite: Schacherl, T., Kelly, J., Kljun, N., Klosterhalfen, A., and Knohl, A.: Interrelation of Forest Structure and Variability of Ecosystem Functional Properties Derived from Eddy Covariance Flux Measurements, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-472, https://doi.org/10.5194/egusphere-egu25-472, 2025.
Norway spruce, which is sensitive to drought, and Scots pine, which is drought-resistant, are two of the most significant conifer species in Europe. In mixed stands, they can utilize resources more efficiently than in pure stands, leading to higher yields and reduced risk. Tree ring research is often used to study their growth in response to complex environmental factors. Machine learning, though rarely applied to tree ring analysis, might be well suited for modelling these complex relations. Data from 22 triplets (1 mixed and two pure plots of Norway spruce and Scots pine) covering a temperature and precipitation gradient of 3.2-9.2°C and 613 to 1075 mm respectively, were used in this study. On each plot, trees were mapped and measured for dbh, height and height to the crown base. 4490 increment cores were collected and synchronized in the lab. A random forest model with relative DBH, age, competition, mixture and climate variables explained 76.4% of the variation and proved effective in describing ecological relationships.
How to cite: Vospernik, S., Bielak, K., Brazaitis, G., Granhus, A., Holm, S.-O., Löf, M., Jansons, A., Metslaid, M., Nord-Larsen, T., Nothdurft, A., Pretzsch, H., Ruiz-Peinado, R., and Sitko, R.: A random forest model for Norway spruce and Scots pine tree rings in Europe, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15559, https://doi.org/10.5194/egusphere-egu25-15559, 2025.
In Europe, forest disturbances increased in scale and severity over the past 70 years producing large amounts of disturbed timber volume [1]. Projections show a further increase of natural disturbances in severity and frequency under a changing climate [2]. In addition, climate change also causes shifts in forest biome distribution due to changes in growing conditions [3] and disturbance patterns [4].
As different disturbance types are interconnected and effects of these interactions have been identified [5], investigating them is especially relevant as they can cause amplification of disturbance effects.
Current ground-based monitoring programs, such as national forest inventories, cannot provide comprehensive and continuous coverage of large areas over time. Therefore, remote sensing applications improve existing data gathering and availability of spatially explicit records for the monitoring of affected areas [6].
For European forests, several different databases collect spatially explicit data on different types of forest disturbances, such as windthrow, fire, and pathogen or insect infections [1]. Across Europe, data from these databases indicate several hotspots, where disturbance interactions can be investigated.
In this study, we investigate several different areas affected by natural disturbances along a gradient in Europe by combining climate data and data on drought occurrence to identify and assess spatio-temporal combinations of predisposing large-scale climate conditions preceding disturbance events. In addition to assessing current interactions between climate and natural disturbance occurrences, our goal is to relate those to projected climate change scenarios in order to investigate the impacts of disturbances on future forest ecosystems.
References:
[1] Patacca, M., Lindner, M., Lucas-Borja, M. E., Cordonnier, T., Fidej, G., Gardiner, B., Hauf, Y., Jasinevičius, G., Labonne, S., Linkevičius, E., Mahnken, M., Milanovic, S., Nabuurs, G.-J., Nagel, T. A., Nikinmaa, L., Panyatov, M., Bercak, R., Seidl, R., Ostrogović Sever, M. Z., Socha, J., Thom, D., Vuletic, D., Zudin, S., and Schelhaas, M.-J.: Significant increase in natural disturbance impacts on European forests since 1950, Global change biology, 29, 1359–1376, https://doi.org/10.1111/gcb.16531, 2023.
[2] Machado Nunes Romeiro, J., Eid, T., Antón-Fernández, C., Kangas, A., and Trømborg, E.: Natural disturbances risks in European Boreal and Temperate forests and their links to climate change – A review of modelling approaches, Forest Ecology and Management, 509, 120071, https://doi.org/10.1016/j.foreco.2022.120071, 2022.
[3] Kirschbaum, M. U. F.: Forest growth and species distribution in a changing climate, Tree physiology, 20, 309–322, https://doi.org/10.1093/treephys/20.5-6.309, 2000.
[4] Altman, J., Fibich, P., Trotsiuk, V., and Altmanova, N.: Global pattern of forest disturbances and its shift under climate change, The Science of the total environment, 915, 170117, https://doi.org/10.1016/j.scitotenv.2024.170117, 2024.
[5] Burton, P. J., Jentsch, A., and Walker, L. R.: The Ecology of Disturbance Interactions, BioScience, 70, 854–870, https://doi.org/10.1093/biosci/biaa088, 2020.
[6] Gnilke, A. and Sanders, T. G. M.: Distinguishing Abrupt and Gradual Forest Disturbances With MODIS-Based Phenological Anomaly Series, Frontiers in plant science, 13, 863116, https://doi.org/10.3389/fpls.2022.863116, 2022.
How to cite: Stadelmann, C., Gnilke, A., and Sanders, T. G.: Exploring European forest disturbance interaction effects in a changing climate, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6297, https://doi.org/10.5194/egusphere-egu25-6297, 2025.
Climate change scenarios foresee a drastic increase in atmospheric and soil droughts, driven by elevated vapor pressure deficit (VPD), in the future. However, the impact of coupled high VPD and soil water deficit on tree physiology is mainly untested, especially in the field. To disentangle VPD and soil moisture effects on mature trees, we installed a unique experimental setup in a 130-year-old natural pine tree forest. By misting water vapor towards tree canopies and excluding precipitation, we decreased VPD by 20-30% and/or precipitation by 50%. We continuously measured sap flow and trunk growth with punctual dial dynamics of gas exchange and leaf water potential for one growing season. We found that high VPD under well-watered (WW) soil conditions increased tree water loss and reduced secondary growth compared to WW trees at reduced VPD. Oppositely, high VPD at dry soil water conditions (WD) reduced whole-plant transpiration by earlier stomatal closure, and increased secondary growth compared to WD trees at lower VPD. Consequently, high VPD can mitigate the adverse effects of soil drought through its impact on stomatal sensitivity, with significant consequences on tree growth. These results highlight the complexity of the physiological response of mature trees under (un-)coupled stresses.
How to cite: Bortolami, G., Gisler, J., Milano, A., Schaub, M., Peters, R., and Grossiord, C.: High VPD mitigates the impact of soil drought in Pinus sylvestris L. through earlier stomatal closure, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5661, https://doi.org/10.5194/egusphere-egu25-5661, 2025.
Forest ecosystems are increasingly affected by intensified disturbance regimes driven both localized and larger scaled climate variation, with impacts on tree growth, physiological processes, and ecosystem productivity. This study utilizes an IoT-enabled sensor network to monitor forest dynamics in a Quercus cerris L. stand, aiming to assess tree responses to climatic variability over two consecutive years, 2021 and 2022.
High-frequency data on radial growth, sap flux density, spectrometric observations, rainfall, stem saturation percentage, temperature and humidity, were collected, providing a comprehensive view of tree-level responses to environmental drivers. Preliminary results suggest a notable reduction in radial growth in 2022 compared to 2021, alongside variations in sap flow and differences in leaf out periods across both years. Furthermore, noticeable differences in both seasonal patterns of RH and Temperature collected by the network of sensors are evident. These changes appear to align with shifts in climatic conditions, particularly precipitation patterns across each year, though the precise mechanisms remain to be fully explored.
The study highlights the potential of IoT-enabled monitoring systems to uncover complex interactions between climate drivers and forest dynamics, offering valuable insights into tree vulnerability. By analyzing diverse datasets, this research contributes to understanding forest sensitivity to climatic stressors and informs the development of adaptive management strategies for sustaining forest health and productivity under changing environmental conditions.
How to cite: Yates, J., Renzi, F., Asgharinia, S., and Valentini, R.: Assessing Tree Response to Climatic Stressors: Insights from IoT-Driven Forest Monitoring, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20026, https://doi.org/10.5194/egusphere-egu25-20026, 2025.
This contribution reports on the effects of drought legacies on mature trees after five years of experimental summer drought in a mixed forest in southern Germany. The study objects are c. 70-80 year old European beech (Fagus sylvatica) and Norway spruce (Picea abies) trees growing in either monospecific or mixed species interactions; a total of about 100 trees in 12 plots under experimental drought (Kranzberg Forest Roof Project: KROOF). For five consecutive years, trees were subjected to complete throughfall exclusion during the growing season. This resulted in up to 80% reduction in physiological and morphological parameters such as reduced photosynthesis, growth and leaf area development. In general, the drought effect was much stronger in the more isohydric spruce compared to the more anisohydric beech. After 5 years of throughfall exclusion, drought release was initiated in the early summer of 2019, resulting in faster recovery in beech compared to spruce.
This presentation will focus on the response of previously drought-stressed trees to a natural summer drought in 2022, three years after the start of drought release, with significant legacy effects under the renewed drought. Previously drought-stressed trees showed increased resistance to renewed drought, with higher stomatal conductance, pre-dawn twig water potential and soil water availability, resulting from lower water use of spruce. We interpret this as a positive legacy effect resulting from leaf area acclimation to the preceding drought. At the end of the five years of experimental drought, spruce reduced its leaf area by more than 60%. After three years of drought recovery, spruce leaf area was still reduced by 1/3 compared to unstressed spruce.
Interestingly, drought stress was also reduced in neighboring beech trees in the absence of leaf area reduction. A 2H-labeling experiment of soil water on the experimental plots showed that beech root water uptake reaches far into the spruce-dominated soil area. These results are supported by analyses of the distribution of beech and spruce roots in the plots. We conclude that during drought, the more anisohydric beech effectively accesses water in the soil under the more isohydric spruce, and thus benefits from the water-saving strategy of spruce even years after previous drought events.
How to cite: Grams, T.: Positive legacy effects after experimental drought in a beech-spruce forest, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6200, https://doi.org/10.5194/egusphere-egu25-6200, 2025.
Crown condition is considered as one of the most important indicators of a tree’s vitality. As part of the monitoring program Long-term Forest Ecosystem Research, the defoliation of tree crowns in Swiss forests has been monitored on an annual time scale since 1985. This long-term data set makes it possible to track the progress of defoliation until the trees die and to take into account a variety of stress factors that may have played a role in this process.
In Swiss forests, the average defoliation of trees and tree mortality has increased in the past decades. However, this only occurred in areas at lower altitude, where climate change has particularly intensified the atmospheric water demand. The importance of water stress as a driver for this development is also confirmed by some of the highest annual increases of defoliation that directly followed exceptionally dry and hot summers.
The probability that individual trees die within a few years starts to increase when the crown defoliation exceeds about 30%. Around 75-85%, most trees seem to reach a point of no return, from which they cannot recover, and which leads to death within a few years, even if no further stress occurs. In the needles of such strongly defoliated Scots pines (Pinus sylvestris L.), we found elevated levels of many stress-related metabolites (particularly osmoprotectants, defense compounds and antioxidants), whereas the levels of these metabolites were homeostatic in the needles of trees in lower defoliation classes. In contrast to the needles, these metabolites were reduced in fine roots of the strongly defoliated trees, suggesting that mainly belowground carbon starvation may impair key functions for tree survival, consequently leading to early death.
How to cite: Hunziker, S. and Gessler, A.: Tree crown defoliation as an early warning signal of increased mortality risk, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8453, https://doi.org/10.5194/egusphere-egu25-8453, 2025.
Mediterranean oak and pine forests support a large diversity of plants and animals, and provide multiple ecosystem services to the benefit of people. Many of these forests are threatened by climate change-induced drought, especially in marginal habitats and at the dry edge of their distribution. Livestock grazing is widespread in drylands, but research on the impact of grazing focuses mainly on the herbaceous vegetation and much less is known on the consequences for woody vegetation, including trees. The overarching objective of this series of studies was to evaluate the impact of livestock grazing on trees in natural oak woodlands and planted pine forests in the drylands of the eastern Mediterranean region that are affected by climate change.
Our results showed that mortality of oak trees (Quercus calliprinos) in a marginal habitat for this species increased non-linearly with decreasing annual precipitation in a 10-year monitoring study. Cattle grazing in a semi-arid woodland consistently improved the water status, storage and use of oaks, and led to enhanced tree growth. The presence of cattle under the tree canopy led to increased soil moisture, microbial activity, and nutrient availability, and raised the trophic level of the soil detritivore community. Pine mortality (Pinus halepensis) in an arid forest was particularly pronounced in extreme drought years and in soils with a low stone content, thus accelerating seasonal soil desiccation. Sheep grazing tended to improve the water status and increased the growth response to precipitation of these trees. In semi-arid regions, goat grazing in a P. pinea forest led to increased soil nutrient cycling and availability (nitrogen, phosphorus), while cattle grazing in a P. brutia forest reduced drought stress in trees.
These studies showed that grazing can be applied as an adaptive land management tool to mitigate some of the negative impacts of extreme drought on oak and pine trees. Grazing might advance the conservation of natural oak woodlands and the sustainability of planted pine forests in drylands. This mitigation potential of livestock grazing might be key for survival of forest trees in a future warmer and drier climate.
How to cite: Grünzweig, J., Hasson, O., Burrows, L., Pinchevsky, D., Navon, Y., Preisler, Y., and Osem, Y.: Grazing can alleviate drought stress in trees of Mediterranean forests at the edge of the desert, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8952, https://doi.org/10.5194/egusphere-egu25-8952, 2025.
Monitoring forest drought stress requires indicators able to explain tree water relations across different species, scales, and functional types. While changes detected by remote sensing indicators of vegetation greenness often represent drought legacies, i.e., lagged responses of trees occurring in the years following a severe drought, measurements of tree function can capture drought signals in real-time. Among these is the photochemical reflectance index (PRI) which detects changes in xanthophyll cycle pigment dynamics. This process reflects increases in photoprotective non-photochemical quenching activity resulting from drought-induced photosynthesis downregulation. However, the complexity of species-specific light and water resource use strategies over short and long timescales, challenges interpretation of this index across species and raises the need for a more mechanistic understanding of remote sensing signals under water limitations.
We combined drone-based multispectral imagery with measurements of tree water relations, pigments, and environmental parameters over one summer in an old-growth mixed forest subject to precipitation manipulation. Our goal was to assess the potential of remote sensing indicators of greenness (Normalized Difference Vegetation Index; NDVI) and photoprotection dynamics (PRI) to track variations in tree hydraulic traits (predawn leaf water potential, Ψleaf_pd; minimum tree water deficit, TWDmin) for seven common European tree species (Abies alba, Picea abies, Pinus sylvestris, Acer pseudoplatanus, Fagus sylvatica, Carpinus betulus, Quercus sp.).
We found NDVI-greenness captured irreversible crown defoliation and browning for the two most drought-stressed deciduous species. In contrast, PRI revealed a strengthening of xanthophyll-cycle induced thermal dissipation during drought, followed by the downregulation of photoprotection activity upon soil water replenishment, for all species and functional types and in agreement with dynamics of measured tree hydraulic traits. The combination of both remote sensing indices and tree height performed best in explaining tree water relations at our site, evidencing the importance of legacy effects captured by greenness in addition to short-term light utilization requirements revealed by PRI. Species-specific diurnal PRI-light response curves, obtained from drone flights conducted at various times of the day, were further analysed to derive metrics aimed at isolating the xanthophyll cycle response (facultative PRI response) from pigment pool size effects (constitutive response), enhancing the comparability across different species and functional types. We found species experiencing greater drought stress mostly exhibited higher photoprotection rates early in the day and a broader operational range of photoprotective systems throughout the day.
This study demonstrates the potential of PRI for drought stress monitoring in mixed forest sites, yet it also underscored the need for further investigations of the combined impact of water and light stress to develop robust cross-species drought monitoring approaches based on remote sensing signals.
How to cite: D'Odorico, P., Fawcett, D., Eisenring, M., Gessler, A., Hoch, G., Kahmen, A., Peters, R. L., Steger, D. N., Zhorzel, T., Zweifel, R., and Ginzler, C.: Remotely sensed photoprotection reveals drought stress across contrasting mature temperate tree species and functional types subjected to precipitation manipulation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9457, https://doi.org/10.5194/egusphere-egu25-9457, 2025.
Strategic long-term planning of mountain forests in the European Alps requires a balancing act between sustaining forest biodiversity and ecosystem services (BES) and mitigating disturbance risks, particularly under climate change. In this context, close-to-nature forestry (CNF) is considered an effective strategy to adapt mountain forests to climate change while sustaining BES. However, it remains unclear for forest management whether current CNF strategies sufficiently reduce forests’ predisposition to climate-change-induced shifts in disturbance regimes.
Decision support systems (DSSs) can help address this challenge by integrating climate-sensitive forest modelling with indicator frameworks for evaluating BES provision and disturbance predisposition, including risks from bark beetle infestations and windthrow. These DSS frameworks have proven a flexible applicability across various forest models, spatial scales, forest types, and environmental conditions. However, climate-change-induced changes of disturbance regimes require adaptations of existing DSS frameworks by accounting for emerging disturbance agents, such as forest fires.
To address this complexity, we integrated the forest gap model ForClim with a disturbance predisposition assessment system (PAS) and assessments of BES provision. Specifically, we integrate a novel forest fire predisposition indicator with an established PAS for bark beetle and windthrow disturbances, along with an indicator framework for evaluating BES. Simulations were conducted for a forest enterprise in the Central Swiss Alps, covering a large elevation gradient, under three climate scenarios (historical, SSP2-4.5, and SSP5-8.5) and six management strategies, including CNF variants with different management intensities and climate-adapted approaches.
Our results indicate that climate change will dynamically alter disturbance predisposition across elevation gradients. Site-related predisposition to fire and bark beetle infestation generally increased under climate change, while stand-related predisposition varied with climate scenario and elevation. Under moderate warming (SSP2-4.5), stand-related predisposition to fire and windthrow increased across all elevations. In contrast, under severe warming (SSP5-8.5), long-term reductions in stand-related predisposition to fire, bark beetle infestation, and windthrow occurred at lower elevations due to declining forest productivity, while predisposition increased at higher elevations with improved growing conditions. CNF emerged as a balanced approach for reducing predisposition to bark beetle infestation and windthrow while maintaining BES. However, CNF promoted stand characteristics that increase stand-related predisposition to forest fires. Our results further show that increasing management intensity generally reduces stand-related disturbance predisposition but can also lead to trade-offs, such as reduced BES provision.
We conclude that climate-adapted forest management must account for both stand-related and site-related predisposition to prioritize disturbance-prone ‘hotspots’, especially in areas of high BES value. Proactively reducing disturbance predisposition may involve short-term trade-offs regarding BES provision but may be crucial to avoid larger, long-term BES losses from severe disturbances. Our study underscores the need for decision support systems to support informed decision-making in mountain forest management.
How to cite: Mutterer, S., Blattert, C., Bont, L., Griess, V., and Schweier, J.: Beetles, wind, and fire: integrating disturbance predisposition assessments into decision support systems for climate-adapted management of mountain forests, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5742, https://doi.org/10.5194/egusphere-egu25-5742, 2025.
Posters on site: Thu, 1 May, 14:00–15:45 | Hall X1
Climate change presents an unmatched challenge to global forest ecosystems and tropical forests serve as important sentinels of ecological transformation. Forest phenology is recognized as an important indicator of ecosystem health and nuanced understandings into the complicated interactions between biological systems and climate variability are offered by it. This study aimed to assess the responses of forest ecosystems using high-resolution PhenoCam images and multi-scale geospatial analysis. We used an integrated method, combining ground-based PhenoCam observations with satellite imagery from AVHRR and Sentinel-2, using ERA-5 Land climate reanalysis data. To produce comprehensive ecological assessments at various geographical and temporal scales, we integrated Normalized Difference Vegetation Index (NDVI) observations with Green Chromatic Coordinate (GCC) analysis. Our finding reveals that the Gir Forest's growth season lasts 203 days and shows a notable upward trend (R² = 0.78, p < 0.01), which is explained by warming temperatures. Interannual variations in Season Start (SOS) and Season End (EOS) were noted, with EOS delaying by 4.2 days each decade and SOS advancing by an average of 3.5 days per decade. This pattern demonstrated the impact of climatic factors by extending the growing season length by roughly 7.7 days every decade. Species-specific responses demonstrated varying susceptibilities to climate variables. Temperature had the strongest correlation with SOS shifts (R² = 0.82), followed by precipitation (R² = 0.68) and soil moisture (R² = 0.55). These findings emphasize the complex interactions between phenological shifts and environmental gradients. By bridging observational scales and methodological techniques, this research offers an important framework for comprehending the dynamics of forest ecosystems. The results highlight the need of using high-resolution remote sensing and sophisticated ecological modelling to track phenological changes and provide crucial information about how climate variability affects tropical dry deciduous forests.
Keywords: Climate change, Phenology, Phenometrics, Remote Sensing, Near surface sensor
How to cite: Sedha, D., Singh, C. P., Solanki, H., and Mathew, J. R.: Deciphering Phenological Dynamics: Multiscale Geospatial Synthesis of Climate Interactions in the Tropical Dry Deciduous Forest Ecosystem of India, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-314, https://doi.org/10.5194/egusphere-egu25-314, 2025.
Tree growth responses to climate depend on factors including species, site-specific conditions, and stand structure, which can be amended by the implementation of forest management practices. Among silvicultural techniques, thinning is known to proficiently enhance forest growth and physiology in seasonally dry environments, influencing tree functional and structural attributes over time. However, its impact on wood hydraulic vulnerability to drought remains unclear. To address this gap, we examined how thinning alters radial growth (BAI), wood anatomy, non-structural carbohydrates (NSC), hydraulic traits and drought resilience in two managed pine plantations (P. sylvestris (PS) and P. nigra (PN)) in a thinning trial along an altitudinal gradient with the following specific objectives: i) to assess the impact of contrasting growth dynamics by the implementation of thinning operations on xylem anatomy, NSC pools (SS and S), and hydraulic traits; and ii) to determine the extent to which thinning-induced growth patterns impacted xylem hydraulic vulnerability and stem variation-derived indices related to water stress for the two study species We found a significant relationship between tree-ring growth and NSC in needles (R2 = 0.83, p < 0.001), weakening from fine roots to sapwood pools. Increased growth induced wood anatomical changes (cell number and lumen area), affecting the wood hydraulic diameter (HD). Consequently, a greater potential hydraulic conductivity was observed for both thinned treatments, with 80.55% and 13.81% increase in PS and PN as compared to control plots, respectively. However, the percent loss of hydraulic conductivity (P50) increased by up to 43.35% (PST) and 38.31% (PNT), supporting that growth follows the safety-efficiency trade-off, i.e., growth-patterns promoted hydraulic efficiency (HD; R2 = 0.79) over hydraulic safety (P50; R2 = 0.84). Water-stress indices derived from trunk variations showed greater sensitivity to water-shortage in thinned plots, with treatment differences of 68.67% for PS and 8.75% for PN. These insights represent the next critical step towards elevating forest management risks to a level that can contribute to our understanding of species-specific responses to thinning and the trade-offs inherent in tree physiology between growth and hydraulic vulnerability in water-scarce environments.
How to cite: Cachinero-Vivar, A. M., Camarero, J. J., and Perez-Priego, O.: Increased tree growth by thinning promotes hydraulic vulnerability and drought stress in pine plantations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2785, https://doi.org/10.5194/egusphere-egu25-2785, 2025.
Tree and branch fall is a risk to traffic infrastructure, forestry, buildings and the energy system. Next to biological and ecological factors like tree species, tree size or soil type, meteorological factors influence tree fall and branch fall risk. While both these types of tree damage are caused by high wind speed tree fall is also connected to storm lengths and changes in root anchorage caused by soil moisture and soil frost. Branch fall is reported to increase with high temperatures.
We aim to identify meteorological factors influencing branch and tree fall, analyse potential most extreme events and estimate future changes in weather-related risks.
In a first step we developed a logistic regression model predicting tree fall risk in winter based on a dataset of tree and branch fall events provided by Germany's national railway company (Deutsche Bahn) and meteorological data derived from ERA5. Here, we used a stepwise model selection process and 10-fold cross validation. Our findings suggest that high wind speeds, a low gust factor, and prolonged duration of strong winds, especially in combination with wet conditions (high precipitation and high soil moisture) and high air density, increase tree fall risk. While severe winter wind storms cause the highest daily numbers in tree fall events, we found that a quarter of all trees fall on days when ERA5 wind speeds are below 11 m/s.
In a second step we are currently extending this existing model for tree fall to the summer season. Furthermore, we are developing a model for branch fall. We will test if additional predictor variables based on tree species and biomass data, convective events and the drought index SPEI will improve these models.
In the near future we will use these models to investigate potential most extreme tree fall hazards and the changes in tree and branch fall risks in future climate scenarios based on climate model output data from CMIP6.
How to cite: Lorenz, R., Becker, N., and Ulbrich, U.: Risk of weather-related tree and branch fall – now and in the future, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3665, https://doi.org/10.5194/egusphere-egu25-3665, 2025.
With the intensification of climate change and anthropogenic activities, water scarcity and drought have become critical challenges around the world, threatening various ecosystems, particularly forests. Forests are social-ecological systems that provide numerous services to humans, who, in return, alter them. While it is impossible to prevent droughts, understanding the attributes of forests, particularly their resilience, may facilitate the mitigation of drought-related adverse consequences. Resilience is a multifaceted concept that has been interpreted through various lenses in the literature, with engineering resilience emphasizing system recovery, ecological resilience investigating the adaptive capacity of forests, and social-ecological resilience highlighting the interconnectedness of human and natural systems in resilience assessment.
Building on these conceptual foundations, seven principles of resilience, maintaining diversity and redundancy (P1), managing connectivity (P2), managing slow variables and feedback (P3), fostering complex adaptive system thinking (P4), encouraging learning and experimentation (P5), broadening participation (P6), and promoting polycentric governance (P7) offer a comprehensive approach to building, evaluating, and enhancing resilience. This review aims to investigate the extent to which resilience principles have been integrated into the discourse of forest resilience to drought in the literature.
Searching the Web of Science database for studies on forest resilience from 1998 to 2024 resulted in 47 papers. Among the reviewed studies, 51% investigated resilience through the lens of ecological resilience, 30% utilized the social-ecological concept, and 19% employed engineering resilience. P4 is frequently examined using tree ring data and drought severity indices (e.g., SPEI). Species richness and composition have often been considered to evaluate P1. A close examination of the methodologies of the reviewed studies revealed that 34% are evidence-based or conceptual studies aimed at understanding the mechanisms contributing to resilience, and 21% are experimental and field studies, which often involve the use of collected field data, such as tree ring width, vegetation growth rate, to explore the response of forest systems to natural or experimentally induced drought events.
The limited use of modeling, specifically landscape or ecosystem services models, in studying forest resilience to drought is evident, with only three studies conducted on this topic. Furthermore, the case studies are nearly evenly distributed across Africa, Europe, North America, and Asia, with 7, 10, 10, and 8 studies, respectively. Four studies investigated the resilience of forests in South America, and another four focused on a global scale. A closer exploration of the reviewed studies revealed that no studies have attempted to consider all seven resilience principles jointly, highlighting a significant research gap in this area and emphasizing the need for more studies to tackle the intricate relationships between ecosystems and human communities and societies.
How to cite: Anamaghi, S., Behboudian, M., and Kalantari, Z.: Understanding Forest Resilience to Drought through Resilience Principles, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4160, https://doi.org/10.5194/egusphere-egu25-4160, 2025.
Drought stress causes widespread forest mortality globally, for instance recently in temperate forests of Central Europe during and after the extremely dry summers in 2018, 2019 and 2022. Trees may die in consequence of hydraulic damage from xylem embolism, but also due to long-term effects caused by allocation into repair and adaptation that may deplete carbon (C) reserves, reduce competition strength and lower resistance to subsequent insect and pathogen infestations. We review implementations of drought-induced tree and forest mortality in ecosystem models and test different implementations in LandscapeDNDC, a terrestrial ecosystem model designed for simulations of the C and nitrogen cycles at site and regional scales. Based on tree hydraulic processes recently integrated into the model, we simulate tree mortality either a) when a threshold in xylem hydraulic conductivity loss is exceeded, or b) when tree water storage is depleted. In addition, we consider c) tree mortality as a result of depleted C reserves and low growth efficiency caused by drought legacy effects. Direct and legacy effects of drought stress on tree mortality rates are parameterized for common European temperate tree species (Fagus sylvatica, Picea abies, Pinus sylvestris, Quercus robur). We evaluate our simulations of drought-related tree mortality rates by comparing them to estimates from forest inventory and remote sensing approaches covering recent drought events. An improved modelling of direct and lagged drought-induced forest mortality is essential to understand the response of the vegetation C cycle to climate change and the options of forest management to increase the resistance of European temperate forests to drought.
How to cite: Thurner, M., Grote, R., Labenski, P., Nadal-Sala, D., Ziegler, Y., and Ruehr, N. K.: Simulation of drought-induced forest mortality with the LandscapeDNDC ecosystem model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6130, https://doi.org/10.5194/egusphere-egu25-6130, 2025.
Climate change poses substantial challenges to forest ecosystems, with increasing temperatures and prolonged droughts driving tree mortality and pest outbreaks across Europe. In Austria, such events threaten the productivity, the forest carbon sink capacity and other forest ecosystem services, necessitating evidence-based strategies to enhance forest resilience. This study addresses this challenge by identifying climate-analogous regions and selecting suitable tree species for Austrian forest ecoregions under changing climatic conditions.
We utilize the CHELSA V2.1 climate data set to identify target regions across the Northern hemisphere where current climatic conditions mirror those projected for the Austrian forest ecoregions by 2100 using three different climate scenarios (SSP1.26, SSP3.70 and SSP5.85). This specifically involves the analysis of a comprehensive set of climate indicators reflecting drivers causing heat stress and drought events, to ensure a precise match with expected conditions. Having tested different metrics, we employ Euclidian distance as measure for climatic similarity. The resulting climate analogues serve as reference areas for identifying tree species that thrive under comparable environmental conditions
The selection of putative tree species from across the northern hemisphere is based on species distribution maps from in total 832 tree species, from which about 15–25 tree species are being selected for each of the nine forest ecoregions. The climatic analysis of putative origins of future tree species or seed provenances is accompanied by a literature analysis of wood characteristics, ecological risks (i.e. invasive potential) and legal constraints for the utilization of the candidate tree species.
By focusing on both the ecological and practical dimensions of species selection, the study provides actionable insights for forest managers. The findings will be integrated into tools such as the "tree species traffic light (https://www.klimafitterwald.at/baumarten/)" facilitating the implementation of forest adaptation strategies with climate-resilient trees in Austrian forests. This research offers a transferable methodology for regions globally, addressing the critical intersection of climate change adaptation and sustainable forest management.
How to cite: Enigl, K., Mayer, K., Schlögl, M., Heiling, C., Aspalter, S., and Schüler, S.: Identifying Climate Analogues and Selecting Resilient Tree Species for Future Austrian Forests, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9902, https://doi.org/10.5194/egusphere-egu25-9902, 2025.
Forest fires are becoming more frequent and intense due to climate change, leading to serious impacts on forest ecosystems. Beyond the immediate damage, they can trigger complex and long-lasting effects on forest health, leading to episodes of tree mortality that can occur even years after the fire event. Understanding these long-term processes and identifying early warning signs of post-fire mortality is a major challenge for forest management in the context of global warming. Multidisciplinary approaches, such as dendro-anatomy and high-resolution sap flow monitoring, have emerged as key tools for studying these processes. Dendro-anatomy provides data on growth and structural changes in xylem, while sap flow monitoring offers insights into water and carbon use dynamics in trees. In our study, we focused on a Pinus piaster Aiton forest in the Vesuvio National Park, southern Italy, which was impacted by a fire in 2017. Since 2021, we have been monitoring dominant trees in both a burned area and an adjacent control site using Tree Talker devices that measure daily sap flow and microenvironmental variables. Our goal is to follow the post-fire dynamics of tree sap flow and integrate these data with dendro-anatomical analyses of wood cores to assess the effects of fire on tree growth and xylem function in the years. This approach aims to allow the identification of potential signals of decline that could precede tree mortality. Preliminary results of sap flow monitoring showed different eco-physiological responses between burned and control trees. In the years immediately following the fire, burned trees exhibited increased sap flow, suggesting a strategy of increased stomatal opening to counteract carbon starvation caused by severe defoliation. However, in the last years, sap flow has decreased, falling below control site levels, indicating a progressive physiological decline, that could suggest these trees have entered a critical phase, approaching a tipping point. Although dendro-anatomy analyses are ongoing, we expect to observe reduced growth and alterations in xylem functionality in burned trees that could corroborate the observed eco-physiological trends and provide further insights into carbon reserve depletion and mortality thresholds. This case study aims to provide an integrated view of the long-term eco-physiological processes in tree species hit by fire, offering valuable tools for adaptive forest management in the face of climate change.
How to cite: Battipaglia, G., kabala, J. P., and Niccoli, F.: Long-term monitoring of sap flow and dendro-anatomy indicate increase mortality risk in fire-damaged Pinus pinaster Aiton forests of southern Italy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10063, https://doi.org/10.5194/egusphere-egu25-10063, 2025.
Cork oak forests play a crucial role in the Mediterranean region, providing ecological, social, and economic benefits. Factors such as wildfires, pests, diseases, and climate change have led to a decline in cork oak ecosystems. This study evaluates the effectiveness of kaolin treatment in mitigating multiple stress factors following cork removal, including water stress while maintaining the canopy’s photochemical efficiency and the long-term vigor of the trees. The research, conducted in a Spanish cork oak forest, assessed physiological parameters such as stomatal conductance, chlorophyll fluorescence, and leaf chlorophyll concentration. Additionally, TreeTalker® devices were employed to monitor sap flow, tree stability, and climatic conditions, offering a comprehensive view of the trees’ physiological responses. Proximal vegetation indices (NDVI and NDRE) were analyzed to evaluate vegetative growth, with no significant differences observed in the short term. Results demonstrated that kaolin application positively impacted photosynthetic performance and water dynamics, as treated trees maintained higher efficiency and resilience than untreated ones. These findings suggest that kaolin treatments could enhance tree resilience to environmental stressors. Further research on the long-term implications for cork production and tree health is recommended to optimize this management strategy.
How to cite: Riggi, S., Brunori, E., Maesano, M., Contarini, M., Guidoni, L., Vannini, A., and Valentini, R.: Assessing the impact of Kaolin treatment on the development and overall health of cork oak trees after cork stripping., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10830, https://doi.org/10.5194/egusphere-egu25-10830, 2025.
Climate-induced forest mortality is an increasing global phenomenon occurring at both regional and local scales, with implications for ecosystem functioning and the provision of essential ecosystem services. In recent years, the Italian peninsula has experienced widespread oak forest decline, with forests showing increased susceptibility to severe heat waves and prolonged droughts. Our study examined a drought-induced tree mortality episode in the Mediterranea region (Pollino National Park, Southern Italy) focusing on deciduous oak forest stands (Quercus frainetto Ten.). We employed a comprehensive approach, combining ecophysiological and dendro-ecological analyses to compare non-decaying (ND) and decaying (D) coexisting trees. Recent advancements in understanding the relationship between petiole xylem anatomy and leaf form and function have revealed a positive correlation between petiole vessel diameter and leaf size, both within and across species. Leaf petioles, serving as the singular entry point for water into the leaf venation system, offer a standardized basis for comparing xylem investment with downstream transpirational demands. To quantify this relationship, we employed a novel index derived from quantitative wood anatomy of petioles. This integrative trait characterizes leaf water transport function by measuring the ratio of cross-sectional xylem area (XA) at the petiole to the downstream leaf area, termed the XLA petiole Index. Our assessment of XLA petiole variation can provide evidence supporting a safety-efficiency trade-off in oak leaves, a crucial aspect of plant hydraulic strategy.
How to cite: Colangelo, M., Guadagno, C., Maria, C., Francesco, R., and Marco, B.: XLA Petiole Index: A Novel Hydraulic Function Metric for Interpreting Drought-Induced Dieback in Mediterranean Ring-Porous Oak Forests, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18995, https://doi.org/10.5194/egusphere-egu25-18995, 2025.
Forests are important natural carbon sinks and can help mitigate climate change. The drought and heat waves of recent years have severely affected forests in Germany, resulting in reduced net CO2 uptake. How forest management, age and species composition moderate the negative impacts of weather extremes on net CO2 uptake or its recovery is still unknown.
For around 25 years, gross primary production, ecosystem respiration and net ecosystem exchange as well as evapotranspiration have been studied in a unmanaged, uneven-aged and mixed beech stand in the Hainich National Park (DE-Hai) and a managed, even-aged and pure beech stand near Leinefelde (DE-Lnf) in Thuringia, Germany.
Both forest stands were and are a substantial CO2 sink (DE-Hai: 512±89 gC m-2 a-1; DE-Lnf: 590±190 gC m-2 a-1), whereby the annual CO2 uptake of the managed stand varied significantly more than that of the unmanaged stand. The CO2 sink function of both stands persisted even in the extremely dry and hot year 2018, though the annual CO2 uptake was reduced by 27% (DE-Hai) and 64% (DE-Lnf) compared to the long-term average from 2002-2017. A reduction in CO2 uptake was also evident in the following year, which can mainly be attributed to persistently low soil water availability. In addition, a loss of tree vitality was observed, which affected the CO2 balance in the following years. In contrast to the unmanaged stand, however, the managed stand already reached higher uptake rates again in 2020. The differences between the stands can mainly be explained by differences in tree age and stand structure. With a mean age of about 130 years, the managed stand consists almost exclusively of vigorous beech trees (optimal phase), whereas the unmanaged stand comprises all age classes and developmental stages, in particular a high proportion of very old trees (> 180 years), which were particularly badly damaged by the drought.
Long-term flux measurement covering 25 years revealed divergent responses of the two differently managed and structured forest stands to drought. In a next step, more sites covering a range of management strategies, species and ages need to be included.
How to cite: Klosterhalfen, A., Markwitz, C., Koebsch, F., Mund, M., Tiedemann, F., Tunsch, E., and Knohl, A.: Long-term dynamics of CO2 fluxes over a managed and an unmanaged beech forest, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11617, https://doi.org/10.5194/egusphere-egu25-11617, 2025.
The increasing frequency and intensity of severe droughts linked to climate change has recently led to significant regional dieback of certain forest species, even at the core of their geographical distribution. The introduction of non-native species, i.e. by assisted migration, from regions with climatic conditions similar to those expected for the target area, could complement other management strategies to maintain sustainable ecosystem services in the future. However, not only drought but also frost is a key physiological stressor shaping trees species distribution. It is therefore essential to assess to what extent the introduced species can withstand cold temperatures and potential extreme frost events. Buds which comprise the leaf primordia are the most vulnerable part of the tree to winter frost damage and different species have evolved contrasting morphological and biochemical strategies to achieve varying degrees of cold-hardiness in winter.
To assess whether, and to what degree, buds from non-native species can withstand severe frosts compared to the phylogenetically related native-species, we sampled branches from five non-native species (Tilia tomentosa, Fagus orientalis, Abies bornmuelleriana, Cedar libani, and Tsuga heterophylla) planted in Switzerland in 2012 and, when present, branches from native species phylogentenically close (Tilia cordata, Fagus sylvatica, Abies alba, and Quercus petraea) growing in the close proximity of the experimental stand. Since cell tolerance to cold temperature is a dynamic trait, reaching a minimum value in deep winter and increasing in spring, we repeated the sampling in January and February 2025 and combined it with an artifical hardening and dehardening treatment (3 days at -4°C and +15°C, respectively). Shortly after sampling, or after the hardening/dehardening treatment, we exposed the buds to different freezing temperatures (-8, -15, -2, -25, -30, and -35°C) and measured cold hardiness of each species using the electrolyte leakage method. The hardening and dehardening treatments aimed to determine the species-specific maximum frost resistance as well their capacity to loose freezing resistance when exposed to a warm spell, which can be critical in the study climate. Additionally, to assess the depth of winter dormancy across all studied species, we placed twigs from each species in a growth chamber set at +20°C, and monitored the time to budbreak and the subsequent phenological development.
We hypothesize that (i) native species are better adapted to withstand extreme frost events compared to the non-native counterparts, and that (ii) non-native species will exhibit higher phenological plasticity by tracking earlier warming at the start of the season, allowing them to take advantage of the favourable growing conditions but potentially exposing them to frost. In contrast, native species, being adapted to the local climate, may escape the frost damage through a later phenological development (temporal frost exclusion) but might be less responsive to take advantage of extended favourable growing season induced by climate warming.
How to cite: Fabiani, G., Vitasse, Y., and D'Odorico, P.: Are drought-resistant non-native species adapted to Central European cold winter? , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6686, https://doi.org/10.5194/egusphere-egu25-6686, 2025.
Europe’s forests are under threat from rising air temperatures and increasingly severe and frequent drought. Yet the carbon storage capacity of these forests is a vital part of the European Green Deal and efforts to mitigate climate change. Due to the multiple demands placed on forests, it is essential to develop accurate methods to monitor their carbon sink strength over large spatial extents, for example by using satellite data. However, capturing drought effects on forest gross primary productivity (GPP) using remote sensing is not straight forward. Drought causes multiple changes to tree physiology and structure over varying timescales that are not always reflected in the optical vegetation indices most commonly used by the remote sensing community.
As part of the EU Horizon project CLIMB-FOREST, we tested the ability of fifteen indices derived from MODIS to detect the negative impact of severe drought on forest GPP. These included indices that respond to changes in leaf pigments, canopy structure, canopy water content and land surface temperature. The analysis compared GPP during drought and non-drought periods at 14 flux tower sites across Europe between 2003-2023. We found that drought during the mid- to late-growing season led to a decline in GPP compared to non-drought years whereas drought during the early growing season was associated with increased GPP. The only MODIS indices that showed significant changes during drought compared to non-drought conditions were NDVI, CCI, PRI and LST. However, several other indices were significantly lower in the year after a drought event, despite GPP returning to average values, which may be evidence of drought legacy effects on forests. Further work will examine how remote sensing indices are linked to changes in ecosystem functional properties during and after drought. By disentangling the relationship between remote sensing indices and drought-related changes to forest carbon fluxes and function, our findings will help improve the accuracy of remote-sensing based models of forest GPP.
How to cite: Kelly, J., Schacherl, T., Eklundh, L., Klosterhalfen, A., and Kljun, N.: Capturing drought and post-drought impacts on forest GPP using a range of satellite indices, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11245, https://doi.org/10.5194/egusphere-egu25-11245, 2025.
While global climate change is a critical concern, its regional impacts on terrestrial ecosystems remain poorly understood. Primary abiotic drivers like temperature and soil moisture are key in shaping vegetation response and distribution, but global warming is expected to amplify their variability, alter frequencies, and disrupt interactions. This creates significant uncertainty regarding their effects on ecosystems. It is unclear whether vegetation responses will be uniform or exhibit contrasting patterns, potentially shifting mean values, distribution, variability, and ecosystem resilience. Understanding these dynamics is vital for predicting ecological outcomes and informing effective mitigation and adaptation strategies.
In this study, satellite observations of vegetation health from 2004 to 2022 are used to assess ecosystem sensitivity to climate stressors across forest ecosystems in Peninsular India, focusing on Deciduous and Evergreen Plant Functional Types (PFTs) in the Eastern and Western Ghats. Our analysis highlights soil moisture (SM) as a primary driver of vegetation productivity, while temperature anomalies, especially during the critical pre-monsoon months (February to May), play a significant role in explaining productivity anomalies, exerting distinct and variable influences across these months. Consequently, these months should be prioritized when assessing temperature-related risks. Regional and PFT-specific interactions with Temperature and Soil Moisture are crucial, with temperature anomalies having a more significant impact in the Eastern Ghats (EG) compared to the Western Ghats (WG), and the influence of SM being greater for deciduous than evergreen PFTs. Additionally, the strength of the response varies across different quantiles, revealing unequal sensitivity and variation in vegetation response throughout the distribution.
Our findings suggest that increased extreme weather events will likely enhance heterogeneous vegetation response and underscores the need for region-specific, adaptive strategies to mitigate the complex and uneven impacts of climate variability on ecosystem productivity.
How to cite: Sen, D., Monteiro, J., and Barua, D.: Regional Climate Stressors and Their Differential Impact on Vegetation Response in Peninsular India’s Forest Ecosystems, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14853, https://doi.org/10.5194/egusphere-egu25-14853, 2025.
Managing forests for resilience has become an important research area in response to escalating climate change and intensifying disturbances. However, it remains unclear whether emphasizing resilience influences the provision of ecosystem services and the overall degree of forest multifunctionality. We hypothesized that forests with higher multifunctionality are also more resilient to natural disturbances—namely, they can better withstand the disturbance and recover—given that factors like species diversity and structural complexity may support both resilience and multifunctionality. We studied this trade-off in a Central European forest landscape using forest landscape and disturbance model iLand. We simulated multidecadal forest development under five management narratives ranging from the emphasis on biomass production through the low-intensity management promoting natural dynamics to unmanaged development. Individual narratives differed in terms of the proportion of species planted after harvest, rotation period, retention of mature trees after harvests, level of control of ungulate populations and sanitary removal of dead and infested trees to prevent bark beetle outbreaks. This experiment was driven by historical climate data and eight climate projections of four climate models and two RCP scenarios. Forest multifunctionality encompassed wood production (represented by annual wood increment and harvested wood volume), biodiversity (Shannon-index and deadwood amount), water protection function (leaf area index and standing volume) and climate regulation function (net ecosystem production and carbon stock). Forest resilience was evaluated through the overall level of disturbed growing stock and the recovery time from a singular disturbance impact. To assess the potential trade-offs, we confronted the newly proposed multifunctionality score with individual resilience indicators.
How to cite: Dobor, L., Baldo, M., Merganičová, K., Kumar Das, A., Bílek, L., and Hlásny, T.: Is a multifunctional forest more resilient to disturbances? , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15552, https://doi.org/10.5194/egusphere-egu25-15552, 2025.
Over the last years several forest dieback and mortality phenomena were reported across the Italian Peninsula underline an enhanced forest vulnerability due to the occurrence of extreme climate events, such as heat waves and severe droughts. During summer 2024 acute and extensive impacts, with severe defoliation, dieback and mortality, on Mediterranean forests (Quercus ilex, Quercus suber, Phillyrea spp. and several other sclerophyllous shrubs) were detected in various regions of Italy predominantly in Apulia, Sardinia and Sicily. Currently, in Italy as well as in other Mediterranean countries is lacking a clear picture of this emerging phenomenon, of the forest species more sensitive and the quantification of the affected forest surfaces. It is, therefore, necessary to improve the monitoring network within the regional territories to assess environmental drivers and dynamics of impacts with a multidisciplinary approach that includes ecophysiological and phytopathological aspects. In this contest, the SilvaCuore application, the first App designed in Italy by the University of Basilicata and Effetreseizero S.r.l., as a part of a Citizen Science project, can play a key role to survey declining forest stands within the Italian territory. The support of an active users’ community can not only allow researchers to survey declining forest sites, but also to better plan research activities and management measures. Specifically, SilvaCuore is a Web-application that can be used directly from smartphone, tablet or PC, and drives the user in reporting information step by step with few simple clicks thanks to a user-friendly interface. The data to be provided are the tree species, symptom detected (i.e. defoliation, drying crown, bark necrosis etc.), the uploading of some descriptive photos and the geo-localization on the map. In this context, the App allowed to identify most of the affected areas by mapping the extension and contributing to the development of a valuable scientific database in Italy. Monitoring of forest health is crucial for implementing appropriate adaptive management strategies and for improving the resilience of declining stands. Indeed, the selection approach may drive the existing legislation and forest management still ill-suited to the current conditions of forest stands affected by climate change.
How to cite: Castellaneta, M., Borghetti, M., Colangelo, M., Rita, A., Colle, G., Pollastrini, M., Bussotti, F., Iacopetti, G., Seddaiu, S., Ruiu, P. A., Scanu, B., Piras, G., Lentini, A., La Mela Veca, D. S., Tarasco, E., Sidoti, A., and Ripullone, F.: Monitoring forest dieback phenomenon in Italy: the key role of the SilvaCuore application, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16479, https://doi.org/10.5194/egusphere-egu25-16479, 2025.
Recent drought events in the Nordic have led to an uptick in drought damage and forest mortality particularly in Norway spruce, either as consequence of the drought itself or caused by subsequent bark beetle attacks. In Norway, this has sparked a debate about existing spruce plantations on unsuitable sites, i.e. sites with insufficient moisture supply, and the need for alternative management strategies. However, identifying those sites at highest risk necessitates a high-resolution, national-scale map of soil water retention characteristics which does not exist. In order to overcome the paucity of mapped soil information relevant for forest management decisions and particularly species selection, we combine registrations from the national forestry inventory (NFI), machine learning and various landscape covariates to qualitatively map soil moisture and nutrient regimes of forest soils at national scale.
In detail, we used registrations of vegetation type from the NFI to classify all plots along seven soil moisture classes (wet to dry) and five soil nutrient classes (poor to rich) placing each plot on an edaphic grid showing relative moisture and nutrient regimes. We employed machine learning, i.e. boosted regression tress, to develop models that predict the probability of belonging to a certain class based on an extensive set of potential predictor variables. These include high-resolution maps and data products covering climate, land cover, terrain characteristics and soil parent material as well as remotely sensed information on forest structure (airborne laser scanning) and spectral vegetation properties (Sentinel-2).
Results showed on overall good agreement between field registrations and predicted soil moisture and nutrient class. We found that models utilizing remotely sensed information on vegetation structure and spectral properties performed significantly better than those that solely relied on climatic and physiographic information.
How to cite: Eisner, S., Antón Fernández, C., McLean, P., and Astrup, R.: National-scale mapping of soil moisture and nutrient regimes in Norwegian forests, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16445, https://doi.org/10.5194/egusphere-egu25-16445, 2025.
Fagus sylvatica L. is one of the most widespread tree species in temperate forests of Western Europe which plays an important role in both ecological and economic terms. European beech stands were especially adapted to the past climate but have suffered a decline in last recent years. Climate change and the increased frequency of extreme events (droughts, heatwaves but also extreme rainfall) seem to be impacting their vitality even if the exact description of this phenomenon is still unclear.
In this context, we have monitored around 97 plots in southern Belgium in which we have evaluated the state of health of ten to fifteen dominant or co-dominant beech trees during the growing season (2022). To describe the state of health, we used the French method DEPERIS and a simplified version of the European ICP-Forests protocol. The aim of this study is to understand the decline phenomenon in its globality and how local and regional factors can influence it. For each plot, topographic, pedological, past and present climate, local tree environment and sylvicultural data were collected (raster layers or in the field) and considered explanatory variables for beech decline. Stand decline, described as the mean defoliation of trees on the plot, and individual tree defoliation are both considered in the analyses. A Random Forest model combined to an analysis of Shapley values allow to explain more than 40% of the variability in beech decline. The results show that (i) climatic factors, such as the rise of mean temperatures compared with the long-term climate of the past and the change in rainfall distribution, and (ii) abiotic factors, such as available water capacity and the trees’ direct local environment, are the most relevant explanatory factors. This research confirms the complexity and interactions between climate change and abiotic conditions in the decline of European beech.
How to cite: Tasseroul, M.-P., Lejeune, P., Claessens, H., Titeux, H., and Brostaux, Y.: Decline of European beech (Fagus sylvatica L.): impact of the local environment and climate change on beech forests in southern Belgium, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13552, https://doi.org/10.5194/egusphere-egu25-13552, 2025.
Boreal forests play a critical role in the global carbon cycle due to their vast coverage and ability to consistently absorb significant amounts of atmospheric carbon. In contrast, hemiboreal forests, which serve as a transitional zone between southern boreal and northern temperate forests, remain relatively understudied. Given their unique position and the rapidly changing climatic conditions in the Northern Hemisphere, hemiboreal forests are increasingly vulnerable to extreme weather events. To improve scientific understanding of long-term carbon dynamics in hemiboreal forests, we investigated annual and seasonal carbon fluxes, their connections to environmental factors, and the forest's response to an extreme weather event—the 2018 heatwave. Using the eddy covariance method, we studied an old upland coniferous hemiboreal forest in Estonia over an eight-year period (2016–2023). This forest is representative of coniferous forests in the hemiboreal zone, and our study provides one of the few long-term datasets available for this region. Our multiyear study reveals that the forest shifted between being a carbon sink and a carbon-neutral state, becoming carbon-neutral in 2020 due to Estonia's warmest autumn in 19 years and atypical weather events in June of the same year. In the following years, the forest's sink strength recovered. Moreover, air temperature was confirmed as the most significant driver of the forest's carbon dynamics. During the 2018 heatwave from mid-July to early August, we observed reductions in ecosystem respiration and gross ecosystem productivity, but by autumn, they had returned to their usual multi-year ranges with no legacy effect in 2019. While our results raise some concerns about the forest’s carbon sink stability, the absence of a legacy effect highlights its resilience to extreme weather events. This underscores the need for long-term monitoring of carbon dynamics in the hemiboreal forest zone to better understand their responses to both rapid and gradual temperature changes.
How to cite: Rogozin, S., Krasnova, A., Mander, Ü., Uri, V., and Soosaar, K.: Long-term carbon sequestration and heatwave resilience in an old hemiboreal upland coniferous forest, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6656, https://doi.org/10.5194/egusphere-egu25-6656, 2025.
Posters virtual: Wed, 30 Apr, 14:00–15:45 | vPoster spot A
EGU25-18429 | ECS | Posters virtual | VPS4
Quantifying Carbon and Water Use Efficiencies of Forest Ecosystems in Wallonia, Belgium: Insights from Species-Specific Responses to Thinning and Climate ChangeWed, 30 Apr, 14:00–15:45 (CEST) | vPA.14
Optimizing carbon use efficiency (CUE) and water use efficiency (WUE) is a critical challenge for temperate forests worldwide, particularly under changing climatic conditions. CUE refers to the proportion of carbon assimilated during photosynthesis that contributes to biomass, while WUE quantifies the carbon gained per unit of water lost through transpiration. The region of Wallonia, Belgium, with temperate forests covering 33% of its land, serves as an exemplary case for analyzing the relationship between CUE and WUE under varying ecological and climatic conditions. Globally, the coupling of CUE and WUE remains insufficiently understood, especially at the species level. This study investigates the dynamics of CUE and WUE across several dominant tree species in Wallonia. It utilizes outputs from the CARAIB dynamic vegetation model to evaluate species-specific responses to thinning practices and climate scenarios (RCP 8.5 and RCP 2.6) over the period 1980 to 2070.
Our analysis distinguishes between the isohydric and anisohydric behaviors of tree species, emphasizing their contrasting long-term responses to climatic changes and their influence on ecosystem efficiency. Trees such as Abies and Picea tend to be isohydric. They conserve water by closing their stomata early during drought. They benefit from thinning practices initiated at 40 years, with intervals of 3–9 years designed to manage competition as they mature. Conversely, trees like Quercus and Populus tend to be anisohydric. They maintain photosynthesis under stress by keeping their stomata open. Populus requires earlier thinning interventions, typically starting at 30 years, with shorter regrowth periods of 15 years to optimize light penetration and nutrient availability. In contrast, Quercus thinning is initiated at 40 years, with regrowth periods of 30 years, to support their growth and optimize resource utilization. Thinning reduces competition and reallocates resources, modulating trade-offs between WUE and CUE while supporting species-specific growth under varying climatic stressors. Tailored thinning practices enhance resource availability for both isohydric and anisohydric species. Isohydric species gain from improved water availability, complementing their inherent drought resilience, while anisohydric species benefit from increased carbon assimilation through enhanced access to light and nutrients.
These findings underscore the importance of aligning species composition and management strategies with localized environmental conditions to bolster forest resilience. With this study, we investigate species-specific management strategies to support sustainable forestry, identifying species that are better adapted to changing climatic conditions and capable of maintaining vital ecosystem services.
How to cite: Verma, A., Lanssens, B., Tölle, M., Chaudhari, T., Hambuckers, A., and Francois, L.: Quantifying Carbon and Water Use Efficiencies of Forest Ecosystems in Wallonia, Belgium: Insights from Species-Specific Responses to Thinning and Climate Change , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18429, https://doi.org/10.5194/egusphere-egu25-18429, 2025.
