Water potential is a key driver of fluxes within natural ecosystems, governing water flow and its direction. Understanding plant hydraulics is essential in the context of climate change, as it helps evaluate the suitability of plant species for specific locations. Plant water potential, and its response to environmental changes, plays a pivotal role in this assessment.
Traditionally, the measurement of plant water potentials has been conducted destructively and intermittently, often employing time-consuming techniques e.g. using a pressure chamber. This has resulted in low temporal resolution of water potential data for individual plants. In contrast, meteorological forcing and topsoil moisture often exhibit much greater variability. This mismatch hinders our understanding of plant responses to changing environmental conditions. This study evaluated the performance of a novel microtensiometer for continuous stem water potential monitoring. Using soil matric potential data at multiple depths, meteorological variables, and the Standardised Precipitation Evapotranspiration Index (SPEI), we analysed stem water potential drivers across three German forest sites via boosted regression trees.
The microtensiometer demonstrated reliability across environmental conditions and for several deciduous tree species (i.e., Fagus sylvatica, Fraxinus excelsior, Carpinus betulus), provided the installation depth was appropriately adjusted for ring-porous species.
Boosted regression analysis revealed soil matric potential at varying soil depths as the primary influence on hourly stem water potential. Uppermost soil layers predominantly influenced stem water potential during the day, while deeper soil layers became more important towards the late evening. This research underscores the microtensiometer's potential to advance plant hydraulics research, offering a continuous, cheaper and minimal-destructive tool to monitor water potential dynamics in forest ecosystems, particularly in the context of a changing climate.
How to cite: Magh, R.-K., Paligi, S. S., Papastefanou, P., Klosterhalfen, A., Rohde, C., Dubbert, M., Beyer, M., Haberstroh, S., Werner, C., Pohl, F., and Hildebrandt, A.: Continuous Observations Highlight Depth-Dependent Soil Matric Potential as Drivers of Stem Water Potential in Temperate Forests under non-drought conditions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8878, https://doi.org/10.5194/egusphere-egu25-8878, 2025.
Both facilitative and competitive interactions between trees affect water relations and fluxes in temperate forests. During drought, hydraulic redistribution (HR) by deep-rooting species such as oak (Quercus robur L.) can provide water from deeper soil layers to shallow-rooted understorey plants. Assuming that shallow-rooted plants take up HR water from mature oaks during drought, we tested two hypotheses: (1) mature oaks share more HR water with oak seedlings than with other understorey plants, and (2) seedlings accumulate most HR water in their roots at sunrise because HR occurs over night. We also quantified how much HR water seedlings used in daily transpiration.
These hypotheses were tested in two experiments. 1) Over a period of six days in July 2023, a total of 7.2 L of ²H-labelled water (5 atom%) was added to a depth of 50-70 cm around mature oak trees in a forest in Brandenburg, Germany. We sampled soils, stem xylem of mature oaks, and roots of two tree species seedlings (oak and black cherry, Prunus serotina EHRH.) and a herbaceous plant (small balsam, Impatiens parviflora DC.) near the labelled trees. From all samples in the water was extracted via cryogenic water extraction and the isotopic composition of the water was analysed. After six days, recovery of δ²H in 0-10 cm soil depths indicated HR via oak roots. Also, seedling roots were enriched in δ²H, confirming HR water uptake with 16 ± 8 % (oak), 13 ± 7 % (black cherry) and 8 ± 4 % (small balsam) of root water originating from HR. Oak seedlings initially had more HR water in root tissues than other species, suggesting faster transport of HR water to oak seedlings, possibly due to shared mycorrhizae or root contact. However, after 60 days, the HR water content of all shallow-rooted understorey plants equalised (~20 %), rejecting our hypothesis 1 that HR water is preferentially found in seedlings of the same species (here: oak).
2) In August 2024, in a Bavarian forest (Germany), soil and stem xylem samples of mature oaks were collected together with root samples from oak seedlings at five daily intervals. Water was again extracted from all samples as in experiment 1. Following the natural gradient of stable water isotope composition in the soil profile, we considered HR water uptake by seedlings, if δ18O values in seedlings did not match δ18O in the surrounding soil, but reflected deeper soil values. At each time interval, seedling transpiration was measured before root excavation. The highest HR water content was found at midday, not at sunrise, in seedlings’ root water, rejecting hypothesis 2. Nevertheless, 29 ± 6 % of the oak seedlings’ daily transpired water originated from HR, emphasising the importance of HR for shallow-rooted understorey plants during drought. Future research should focus on the transport pathways of HR water from mature trees to shallow-rooted understorey plants to improve mechanistic understanding.
How to cite: Dluhosch, D., Gebhardt, T., Grams, T. E. E., Annighöfer, P., and Hafner, B. D.: Shallow rooted understory plants of different species use hydraulically redistributed water by mature oak trees during natural drought periods , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6687, https://doi.org/10.5194/egusphere-egu25-6687, 2025.
Terrestrial ecosystems’ response to atmospheric changes (e.g., CO₂ levels, vapor pressure deficit) and the redistribution of water on land has drawn significant attention in recent years. Understanding the sources of water that trees utilize is critical for elucidating their adaptation strategies and resilience as precipitation patterns and seasonality shift in a changing climate.
Recent studies suggest that trees primarily rely on winter precipitation during summer (e.g., Allen et al., 2019; Goldsmith et al., 2022; Floriancic et al., 2024). However, the intercomparison of xylem water extraction methods for stable isotope analysis reveals substantial isotopic variation depending on the method employed.
In this study, we used cryogenic vacuum distillation (CVD), the Scholander pressure bomb (SPB), and in situ vapor equilibrium methods to determine the stable isotopic composition (²H and ¹⁸O) of xylem water in Scots pine trees. Our research was conducted under a long-term (20-year) irrigation experiment at the Pfynwald, Switzerland. Sampling included plots with trees growing under naturally dry conditions (control), irrigated conditions (since 2003), and previously irrigated conditions (irrigation ceased in 2014 after 10 years).
Our analysis demonstrates that SPB measurements align closely with in situ vapor equilibrium measurements, while the CVD method exhibits a significant offset in ²H and ¹⁸O isotopic values. Furthermore, we show that conclusions regarding the seasonal origin of xylem water—whether winter or summer precipitation—are highly dependent on the extraction method used. If the choice of extraction method significantly influences conclusions about the seasonal orientation of tree water uptake, our predictions of tree responses to future shifts in precipitation patterns could be fundamentally flawed. These findings highlight the urgent need for methodological standardization to enhance the reliability of isotopic interpretations in tree water uptake studies.
How to cite: R. Freund, E., Villiger, M., Lehmann, M. M., Hu, Z., Meusburger, K., and Gessler, A.: Do Trees Truly Take Up Winter Precipitation During Summer?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17859, https://doi.org/10.5194/egusphere-egu25-17859, 2025.
The exchange of fluxes between surface and subsurface water pools and vegetation is highly complex due to the dynamic - in space and time- interactions among several biotic (physiological) and abiotic (hydrometeorological, geological, geomorphological, pedological) factors. Efforts that go beyond the analysis of individual processes and aim at capturing how different processes and factors are strictly connected are essential to achieve a wider understanding of how forest ecosystems work and respond to climate stress. In this work, I capitalize and build on an increasing knowledge deriving from field observations in the mountain forested Re della Pietra experimental catchment (2 km2) in Italy, to investigate the main ecohydrological linkages governing the functioning of this ecosystem, specifically focusing on the role of hillslope topography.
Field measurements and statistical modelling analyses carried out through wavelet and machine learning applications revealed that the high slope of a 120m-long monitored hillslope in the headwater of the catchment controlled the spatial distribution of water in the vadose zone and affected the occurrence of subsurface preferential flow.
Higher soil water contents in the lower part of the hillslope promoted a faster and more efficient growth of trees that had larger diameters compared to trees in the upper part of the hillslope, although being of the same age, clearly reflecting local differences in water availability that impacted on growth rates. This behaviour was confirmed by sapflow measurements and isotope data that showed more reduced sapflow velocity of trees in the upper part of the hillslope during dry conditions compared to trees at the hillslope bottom, despite soil water in the first 40-cm was the main source for all trees. In turn, these differences in tree size and canopy expansion along the hillslope affected canopy interception, with larger and temporally stable patterns of throughfall in the upper hillslope, characterized by less dense canopies, than the hillslope bottom. Moreover, the relation between sap flow velocity and vapour pressure deficit varied along the hillslope as well, with larger hysteresis loops as a function of increased solar radiation, temperature, and soil moisture in the upper and middle part of the hillslope but erratic and more complex patterns at the hillslope bottom.
In the headwater, preferential flow occurred preferably in the middle hillslope position and more frequently during wet antecedent conditions, revealing a feedback relation between preferential flow and soil moisture. The initiation of preferential flow contributed to developing subsurface hillslope-stream connectivity that promoted sustained streamflow during large events. However, in the lower part of the catchment, where the hillslope slope is gentler, preferential flow was mainly controlled by soil properties (particularly, bulk density) and occurred more frequently than in the headwaters indicating that other factors interact with topography.
These results contribute to a more thorough understanding of ecohydrological linkages in mountain forested catchments and pave the way for further analyses aimed at disentangling the combined role of different but complementary factors driving the ecological and hydrological response of forest ecosystems.
How to cite: Penna, D.: Ecohydrological linkages in forest ecosystems: the case of the Re della Pietra catchment, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16320, https://doi.org/10.5194/egusphere-egu25-16320, 2025.
Global warming has led to an accelerated dry-wet transition, causing forests to experience more water stress and water use strategy alterations. This could take a great effect on trees in karst region due to tremendous spatial and temporal variability of soil and rock moistures. In this study, we monitored and compared transpiration (sap flow) responses to meteorological variables, soil moisture content and rock moisture content at five sites with a variety of plant-soil-rock compositions in the karst region of southwest China. Results show that the soil-rock composition generally controlled tree growth and transpiration amount, and over 80% transpiration was concentrated in wet growing period. The thin soils can only offer a limited soil moisture and rock moisture dominated transpiration variability and physiological strategies of tree water-use. High and steady rock moisture in appropriate rock fractures enabled tree to exhibit isohydric behavior that can substantially reduce transpiration and seasonal variability. Conversely, low rock moisture made tree tend to anisohydric behavior that increased transpiration in the wet period for resisting drought stress in the dry period. The transition from isohydric to anisohydric behavior for tracking varying environment could reduce tree transpiration response to meteorological variations, such as vapor pressure deficit, and even results in alteration of tree size dominant transpiration. Since tree physiological behavior is extremely sensitive to climate variations and soil-rock compositions, the future acceleration of wet-dry transition is highly possible to increase vulnerability of ecosystems in the region.
How to cite: Liu, X., Chen, X., Zhang, Z., Liu, W., Peng, T., and McDonnell, J.: The role of rock fractures as a water source for trees growing in karst, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-164, https://doi.org/10.5194/egusphere-egu25-164, 2025.
Forests cover almost one third of the Earth's land area and are central in the carbon and water cycles. Soil water availability is one of the most important factors regulating transpiration, biomass production and plant species distribution in ecosystems. The carbon and water cycles are closely linked and so understanding the functioning and evolution of forest environments and their relation to subsurface structure and water availability is essential to improve understanding of the water cycle under a changing climate. Studying the forest subsurface is a challenge because of its heterogeneous nature and difficult accessibility. Traditional approaches used by ecologists are also often point measurements that have a low spatial representativity. Near-surface geophysics offers a wide range of methods to characterize the spatial and temporal variability of subsurface properties and associated processes in a non-destructive and integrative way. Geophysical methods allow us to obtain new information that complements ecophysiological methods to better understand ecosystem functioning, and in particular processes linked to ecohydrology. The use of geophysical methods in forests is growing, both by geophysicists seeking to apply their tools to more complex environments, and by ecologists seeking to better characterize their experimental sites. One of the major applications and assets of geophysics in forests is to quantify and monitor water stocks and dynamics. For example, geoelectrical monitoring can be used to assess the distribution and spatial variations of water content in the subsoil. In this work, we show the example of a recently developed ensemble approach to quantitatively relate electrical conductivity monitoring and the distribution and dynamic of water in forest soils. We believe that such interdisciplinary advances can help us improving the quantitative assessment of forest responses to the environment and their adaptation to climate change.
How to cite: Jougnot, D., Loiseau, B., Chaffaut, Q., Singha, K., Delpierre, N., Guérin, R., Clément, R., Champollion, C., Doussan, C., Martin-StPaul, N., and Carrière, S.: Unveiling the forest subsurface and its invisible water, what can geophysics bring to forest ecohydrology, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11195, https://doi.org/10.5194/egusphere-egu25-11195, 2025.
Recent studies show that incorporating leaf water potential and plant hydraulics into land surface models can significantly improve evapotranspiration (ET) prediction. However, direct measurements of leaf water potential are destructive and very sparse. This largely limits their use to constrain large-scale plant hydraulics modeling. Meanwhile, vegetation optical depth (VOD), derived from microwave remote sensing, is often seen as a proxy for vegetation water content. Despite its wide applications for understanding water stress impacts on ecosystems, the relationships between VOD, leaf water potential and biomass still remain unclear. This gap has hindered our ability to use VOD to constrain large-scale land surface models. In this study, we develop a physics-informed machine learning model to predict VOD from water potential, leaf area index (LAI), temperature, and ecosystem attributes. The model is constrained by soil constitutive relations that convert soil moisture into water potential. Global remote sensing datasets of VOD (VODCA V2.0 and SMAP MT-DCA) and soil moisture (ESA CCI V8.1) are used to train the neural networks. We further apply the Explainable AI (XAI) technique, SHAP, to interpret how different input features (e.g. LAI, temperature, and water potential) contribute to VOD variability, and reveal how ecosystem attributes impact the water potential-VOD relations. This approach enables us to systematically examine the spatial variations of VOD-biomass-water potential relationships and the critical roles of ecosystem attributes in modulating these patterns. The results can enhance the applicability of VOD assimilation into land surface models, and thereby further improve the representation of plant hydraulics and ecosystem functions in large-scale models.
How to cite: Feng, D. and Konings, A.: Determining the Relative Influence of Water Potential, Biomass, and Temperature on Vegetation Optical Depth Using Physics-informed Machine Learning, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20703, https://doi.org/10.5194/egusphere-egu25-20703, 2025.
Mediterranean dryland forests are defined by intricate relationships between vegetation, soil, and water. This study explores the long-term effects of thinning on soil moisture dynamics and canopy's rain and light interception in the Kedoshim Forest, Judean Mountains, Israel. This mature Pinus halepensis forest receives approximately 550 mm of annual precipitation.
The research, conducted within a Long-Term Ecological Research (LTER) framework, compared two heavily thinned plots (100 trees ha⁻¹, thinned 15 years ago) with two non-thinned control plots (550 trees ha⁻¹). Soil moisture was monitored continuously using Time-Domain Reflectometry (TDR) sensors at depths of 0.5 m, 1.0 m, and 1.5 m. Annual measurements of overstory and understory leaf area indexes (LAI) were conducted to evaluate vegetation structure. Rain interception by a dense Jerusalem pine canopy and meteorological data from local stations were recorded.
Results
Vegetation Dynamics: Control plots maintained 50% higher overstory LAI (2.06 ± 0.2) than thinned plots (1.34 ± 0.1). However, understory LAI was greater in thinned plots (1.24 ± 0.2) and comprised 48% of total LAI versus (0.82 ± 0.2) in control plots with 28% of total LAI, reflecting enhanced understory growth following 15 years post-thinning.
Abiotic effects: No significant differences were observed in air temperature and humidity, but wind speed and radiation reaching the understory were higher in the thinning compared to the control plots. Forest thinning caused a reduction in both light interception and water consumption by the forest overstory trees. The understory vegetation utilized these released resources.
Soil Moisture Dynamics: Thinned plots had higher annual mean soil moisture at shallow depths (0.5 m) (19.3% ± 1.9%) compared to control plots (17.7% ± 1.8%, P < 0.0001) due to reduced rain interception by overstory canopy. This difference was significant during the rainy season. However, at 1.5 m, control plots exhibited higher mean soil moisture (29.3% ± 2.7%) than thinned plots (25.5% ± 2.1%, P < 0.0001), likely due to greater understory water consumption in the thinned plots during the all hydrological season. No significant differences were observed at 1.0 m depth.
Discussion and Implications
Thinning has lasting impacts on forest hydrology. Reduced rain interception in thinned plots increases shallow soil moisture during the rainy season, while light interception enhances undergrowth and water consumption by understory vegetation. These findings highlight the complex interplay between overstory and understory vegetation structure and characteristics in driving hydrological outcomes.
Observing soil moisture along root-zone depth levels offers insight into the soil water variability dynamics, adding to better dryland forest management.
Conclusion
This study underscores the importance of integrated ecohydrological strategies for resilient dryland forest management under varying climatic and management conditions.
How to cite: Muklada, H., Moshe, Y., Cohen, Z., Zavalishin, K., and Osem, Y.: Soil Moisture Dynamics Under Long-Term Thinning and Dryland Forest Management Using TDR Sensors, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12208, https://doi.org/10.5194/egusphere-egu25-12208, 2025.
Ecohydrological studies frequently use the stable isotopic composition of precipitation as a natural tracer. In wooded areas, understanding how the precipitation isotopic composition is modified as it passes through the canopy is therefore key to accurate ecohydrological assessments. This work presents a model to estimate the isotopic composition of throughfall at a detailed time-step, based on the dynamics of rainfall isotopic composition and meteorological conditions during rainfall events. The model couples the Rutter (1971) rainfall interception model with the Gonfiantini (1986) equation, the latter is used to estimate the stable isotopic composition of open water bodies subject to evaporation.
The model was tested and validated using intra-event volumes (5 min intervals) and isotopic compositions (131 samples, sampled each 5-mm of rainfall) from 25 rainfall/throughfall events in a Scots pine forest at the Vallcebre Research Catchments (South-Eastern Pyrenees, Spain).
The results demonstrate the model's ability to predict both throughfall volumes and the isotopic compositions across a range of precipitation events with marked differences in precipitation volumes (9 to 72 mm), mean intensities (0.6 to 29 mmh-1), meteorological conditions, and different intra-event dynamics of the rainfall isotopic composition. An excellent correlation was found between observed and predicted throughfall volumes, with 84% of the events having a Kling-Gupta efficiency greater than 0.65. In addition, the model accurately predicted the observed throughfall isotopic signature (for δ18O, r2=0.98, p<0.05). At the intra-event scale, observed and predicted throughfall isotopic signatures were not statistically different. However, the isotopic shift between throughfall and rainfall was somewhat higher for the observed throughfall compared to model results, with 84% and 76% of the throughfall observed and predicted samples, respectively, more enriched than rainfall.
How to cite: Llorens, P., Cayuela, C., Pinos, J., Latron, J., and Gallart, F.: Modelling the changes in the isotopic composition of water routing through the forest canopy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8408, https://doi.org/10.5194/egusphere-egu25-8408, 2025.
The study investigates different post-fire forest restoration methods, including varying postfire structure densities, as well as mulching and physical barriers typology with a particular focus on field sites with high ecological values located in Castilla-La Mancha region (Spain). To date, there is limited empirical support for the efficacy of these management strategies in reinstating the water cycle to promote vegetation health and erosion prevention, despite substantial financial investment. The presentation will discuss the limitations of interpreting data from current point sensors and will cover development strategies for an effective survey technique, incorporating automatic geophysics (permanent Electrical Resistivity Tomography), to improve data collection for monitoring subsurface water dynamics. The prospection strategy is informed by preliminary modeling results derived from energy and water balance models, which predict evapotranspiration (ET) and plant water availability as well as groundwater recharge and flow.
How to cite: Mary, B., Burchard-Levine, V., Herrezuelo, M. Á., Nieto, H., Lucas Borja, M. E., and García, M.: Modeling and geophysical monitoring to uncover surface and subsurface water flows in post-fire management, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3785, https://doi.org/10.5194/egusphere-egu25-3785, 2025.
Evapotranspiration (ET) is a key process of the water cycle in general and in ecohydrology in particular. Measuring ET in forest eco-hydrosystems allows us to gain a better understanding of the response of forests to drought events, and to better anticipate the effects of climate change. Punctual (e.g. lysimeters or sapflow measurements) or integrative measurement methods (e.g. eddy covariance tower) can be used to estimate ET at the forest stand scale but these methods are not without limitations (e.g., resolution issues, representativeness, not adapted to mountainous areas).
Superconducting gravimeters can be used to study ET. These gravimeters can be deployed in both flat and mountainous environments. In this work, we studied the hydrological residuals (i.e., hydrologically induced gravity variations) of 5 superconducting gravimeters located in different contexts. We interpreted the daily decreases in the stacked hydrological residual as the loss of water mass due to evapotranspiration. These results were compared with those of the SimpKcET water balance model.
The results underline that the detectability of the ET signal depends strongly on the configuration of the gravimetric station, the topography and the type of ecosystem. We show that gravimeters located on summit area and in a forested context can detect the seasonality of ET. Conversely, gravimeters located in flat or underground areas and with a significant masking effect are unable to detect ET.
Gravimetry therefore has a strong complementarity with conventional methods used to study ET and could contribute to a better understanding of water fluxes in forested ecosystems.
How to cite: Chaffaut, Q., Loiseau, B., Ginoux, M., Lesparre, N., Olioso, A., Ollivier, C., Belfort, B., Pierret, M.-C., Merlet, S., Cotel, S., Champollion, C., Le Moigne, N., Chalikakis, K., Mazzilli, N., Demarty, J., Jougnot, D., and Carrière, S. D.: Detectability of the daily evapotranspiration cycle in superconducting gravimeter timeseries according to the measurement configuration, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16741, https://doi.org/10.5194/egusphere-egu25-16741, 2025.
Water storage and flow in soils play a key role in forest growth by controlling the availability of water and, thus, controlling plants' physiological needs. Water circulation processes in the subsurface-plant-atmosphere continuum, however, remain difficult to observe and quantify. While punctual sensors presently provide information on local (centimetre scale) dynamics, integrative measurements capturing the dynamic of water exchanges at the tree scale are lacking. The electrical Self-Potential (SP) method is strongly impacted by water flow as ions transported by the water flux can induce an electrical signal as manifested by previous investigations on trees. Continuous SP measurements can be acquired with a relatively fine temporal resolution and autonomously. Moreover, the method is mildly invasive as it only requires the introduction of electrodes in the soil or in the sapwood. We hypothesised that SP measurements simultaneously acquired both in the soil and in the trees would show distinctive characteristics that could inform, in a complementary manner, about water exchange processes occurring in the soil-vegetation-atmosphere continuum.
We monitored SP in a young spruce forest in the Vosges mountains, France (OHGE - OZCAR). We repeated the measurements (1) in the soil at different distances from a tree trunk; (2) on tree trunks by positioning close electrode dipoles; (3) on several trees from a same plot. The measured signals showed strong discrepancies among trees. We then analysed the characteristics of the signal frequencies by computing the wavelet spectrum, applying the variational mode decomposition method and performing a singular spectrum analysis... Indeed, variations of the meteorological conditions seemed to impact the occurrence of oscillation at given frequencies. For instance, daily oscillations disappear in the soil during rainy events.
How to cite: Lesparre, N., Bonal, D., Matthey, P.-D., Hernandez, A., Carrière, S. D., Ackerer, P., Jouniaux, L., Jougnot, D., Linde, N., and Belfort, B.: Electrical self-potential signals in a temperate forest: seeking similarities between trees, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18789, https://doi.org/10.5194/egusphere-egu25-18789, 2025.
Large-scale ecological restoration has gained recognition as a promising nature-based solution for addressing global environmental and societal challenges. The Three-North Shelterbelt Forest Program (TNSFP), the world's largest ecological restoration project in China, has achieved considerable ecological and social benefits. However, its long-term resilience and sustainability remain subjects of scientific debate and public concern. Here, we explored vegetation resilience trajectories and their relationships with water budgets across the program region from 2001 to 2022, and projected future vegetation suitability through 2050 (i.e., the end of the TNSFP) by integrating meteorological observations, remote sensing data, and outputs from global circulation models. We found that 48.2% of the vegetation exhibited declining resilience, particularly in forested areas, despite widespread greening across the TNSFP region. Vegetation resilience strengthened against the increase in productivity within the water resource carrying capacity, but the relationship reversed once productivity surpassed water availability limits. Notably, forest resilience peaked under conditions of full precipitation utilization, whereas grassland resilience reached its lowest point when water supply and demand were balanced. By 2050, approximately 6.5% of the study area is projected to face degradation risk, with an additional 22.2% potentially at risk. Our findings emphasize the importance of water resource availability for vegetation resilience and stability, laying a scientific foundation for sustainable ecological restoration strategies.
How to cite: Xu, H., Pang, J., Chen, J., Wei, X., Cao, W., Sun, G., Xu, Y., and Zhang, Z.: Resilience of the large-scale ecological restoration: How water matters?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5012, https://doi.org/10.5194/egusphere-egu25-5012, 2025.
In mediterranean-type climate conditions, fog contributes significantly to the water balance of the ecosystem, since precipitation rates are lower than evapotranspiration rates. However, it remains unclear whether fog contribution is a direct input of water to the system through canopy dripping or if it limits evapotranspiration by limiting radiation and vapor pressure deficit. Focusing on the former, in this study we aim to understand the fog water as a input to the water balance in mediterranean coastal forests. Using the water balance principle (ΔS = ET - (P + F)), we characterize the key elements of water storage (ΔS), evapotranspiration (ET), precipitation (P), and fog (F) over different vegetation units that compose the mediterranean forest. The data used for this characterization is gathered from in-situ measurements (meteorological stations and standard fog collectors) and remote sensing sources (GOES and MODIS products). To quantify fog interception by vegetation unit canopies, a numerical model (AMARU; Lobos-Roco et al., 2025) is used, which estimates the fog inflow from routine meteorological data. By solving the water balance equation for the forest areas, we are able to determine the fog collection efficiency, which allows us to estimate the amount of water collected by the forest. Finally, to evaluate the modeling outputs, we conduct an in-situ experiment to measure water collection from the forest canopy using analog rain gauges. Our preliminary results show that fog contributes as water input in forests located in south and west facing slopes, reaching ET requirements. Moreover, our estimates of forest fog collection efficiency round 10%, meaning that only 1/10 of fog inflow is captured by forest canopy. We expect that this study contributes to advance our understanding of forest dynamics in coastal mediterranean ecosystems and their responses to fog water input.
How to cite: Herrera, J., Lobos-Roco, F., Pliscoff, P., and del Río, C.: The role of fog in the water balance of coastal mediterranean forest in Chile, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7210, https://doi.org/10.5194/egusphere-egu25-7210, 2025.
In forested environments, precipitation is intercepted and redistributed within the tree canopy, thereby generating spatially heterogeneous water fluxes to the forest floor. Water from the forest soil is taken up by roots and subsequently released back into the atmosphere through the process of transpiration. However, the effect of either of these processes on spatial variation of soil water content and water fluxes remains to be elucidated.
In this study, we examined the temporal variability in soil water content, measured along a canopy cover gradient of three distinct tree species over two years. Our analysis focused on two phases of soil drying following precipitation events during the growing season. Specifically, we evaluated the immediate effect of precipitation on soil wetting and the subsequent root water uptake during longer dry periods. To identify the factors significantly influencing the soil water response to precipitation, we employed a linear mixed effects modeling approach.
The results indicate that spatial patterns of throughfall had a weak yet significant influence on the soil water response. The effect of position along the canopy cover gradient depended on event gross precipitation, which suggests that the canopy cover gradient only reflected the spatial patterns of water input when gross precipitation was low. Soil wetting was less pronounced under Fagus sylvatica than under Picea abies and Pinus sylvestris. The soil water response to precipitation was found to be influenced by the spatial patterns of the pre-event soil moisture, with soil profiles that were locally wetter responding more strongly to precipitation, as has previously been observed for other sites and vegetation covers. This effect was more pronounced in overall dry soils and higher event gross precipitation, hence indicating preferential flow. Furthermore, root water uptake was found to be considerably higher under F. sylvatica and P. sylvestris than under P. abies. The root water uptake depth profiles of F. sylvatica and P. sylvestris exhibited substantial uptake from soil layers as deep as one meter below the soil surface, whereas root water uptake of P. abies was more confined to the topsoil, despite occasional observations of deeper root water uptake.
The findings of this work emphasize the influence of the tree canopy on belowground water fluxes and illustrate pronounced species-specific differences in soil wetting and root water uptake.
How to cite: Hildebrandt, A., Lukas, N., and Magh, R.-K.: Species-Specific Interactions Between Canopy Cover, Soil Water Dynamics, and Root Water Uptake in Temperate Forest Ecosystems, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8222, https://doi.org/10.5194/egusphere-egu25-8222, 2025.
Earth’s Critical Zone exhibits remarkable heterogeneity and complexity. Hence, further investigation is required to examine the composition of Earth’s Critical Zone as well as the diverse eco-hydrological patterns they exhibit under varying climatic and geological circumstances. This exploration should primarily be conducted through the investigation and experiments of the hillslope unit, where the topography and weathered bedrock are representative, with particular emphasis on semi-arid regions where water resources serve as the primary limiting factor. Here, we have determined that the structure of the weathering profile displays systematic variation across the topography and heterogeneous landscape on uninterrupted slopes. Differences in the structure of the subsurface critical zone led to differencesin its water storage capacity at the same time.Runoff in alpine shrubs and forests was dominated by subsurface runoff, and grassland was dominated by surface runoff. In the alpine shrub immediately adjacent to the watershed, an estimated quantity of 129 mm of water is stored within the unsaturated zone of the soil, serving as exchange water to replenish moisture in the underlying bedrock. In contrast to alpine shrubs, an estimated quantity of 62.7 mm of water originates from the unsaturated zone of soil and weathered bedrock in the forest. However, approximately 21.1 mm of moisture is unavailable to plants. The soil water storage in grasslands exhibits a decline throughout the growing season, with a subsequent augmentation occurring solely after substantial precipitation events exceeding 20 mm. In wet years, dynamic storage predominantly manifests as groundwater saturation throughout the entire ground and high subsurface runoff. In dry years, the limited runoff response indicates that the catchment’s dynamic water storage primarily comprises“indirect”water storage, which predominantly resides within the soil, saprolite, and weathered rock below the“field capacity”, subsequently being released into the atmosphere through evapotranspiration.
How to cite: Lin, P., He, Z., Zhu, X., and Tian, Q.: Modulation of evapotranspiration and stream runoff by weathered bedrock in arid and semi-arid mountains , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13849, https://doi.org/10.5194/egusphere-egu25-13849, 2025.
Transpiration, a major water flux of the hydrological cycle, is limited by plant’s control on stomatal conductance. Plants increase stomatal conductance to take up carbon from the atmosphere for photosynthesis, i.e., during periods of high radiation, and decrease stomatal conductance to limit water loss, i.e., during periods of high vapor pressure deficit. At the same time, stomatal conductance is thightly linked to leaf water potential, which in turn is affected by the water availability for the plant through its root distribution across the gradient of water potentials in the soil. This soil-plant hydraulic system differs across species depending on the species-specific hydraulic traits, such as the stomatal sensitivity to changing leaf water potentials or the distribution of roots in the soil. Furthermore, the ability to store and release water from its tissues, here referred to as hydraulic capacitance, directly affects soil-plant hydraulics by enabling plants to source water from their internal water storage instead of the soil. Thereby, hydraulic capacitance can act as a hydraulic buffer during periods of low water availability in the root zone or high water demand from the atmosphere, particularly when plant internal water storage is high. Because plant water storage and hydraulic capacitance are rarely considered in soil-plant hydraulic models and can not directly be measured in the field, we still lack a comprehensive mechanistic understanding on how capacitance potentially affects stomatal regulation across species and environmental conditions.
In this study, we extended a soil-plant hydraulic model that simulates water fluxes across the soil-plant system utilizing well-constrained concepts of water flow in porous media, to include plant water storage and hydraulic capacitance. The model serves to better understand the sensitivity of soil-plant hydraulics towards plant water storage and capacitance. Soil-plant hydraulic simulations were validated with data from the ‘WaldLab forest experimental site’ in Zürich, Switzerland, where we have been measuring water fluxes and potentials in soils, roots, stems and stomata of beech (Fagus sylvatica) and spruce (Picea abies) trees for the past four growing seasons, including periods of limited water availability. The measurements together with the hydraulic simulations yield novel insights into species-specific water use strategies and hydraulic traits.
Our results show the different stomatal behaviour of beech and spruce, with beech generally allowing leaf water potentials to drop further than spruce. Both species showed shifts to deep root water uptake during soil drying, but the higher uptake from deeper and wetter soils was not enough to compensate for the lower water availability in the shallower, drier soils. We observed higher water storage capacity and hydraulic capacitance in spruce. However, despite higher capacitance, spruce were more conservative in their water use and did typically not allow high transpiration rates and low leaf water potentials.
How to cite: Martinetti, S., Carminati, A., Molnar, P., and Floriancic, M.: Linking root water uptake, plant-hydraulic traits and transpiration dynamics of beech and spruce, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16286, https://doi.org/10.5194/egusphere-egu25-16286, 2025.
To gain a better understanding of tree vulnerability to drought stress, we need to observe when and where stress occurs. Established techniques tend to be limited by technical shortcomings in monitoring environmental and plant conditions at appropriate temporal and spatial scales. New techniques to overcome limitations are becoming available, but they must be benchmarked and tested in a range of conditions.
Thermal infrared (TIR) remote sensing allows drought stress detection because down-regulated transpiration due to water shortage also reduces evaporative cooling of the foliage. The TIR-based crop water stress index (CWSI), which compares canopy temperature to expected temperatures in a well-watered and un-watered canopy, has been used to quantify drought stress in crops for many decades, but its utility in forests remains uncertain due to complex canopy thermal structure and narrow temperature ranges in humid environments. We used a combination of ground-based and drone-based data to detect drought stress in a young beech stand in Luxembourg, comparing continuous TIR data for individual trees using tower-based IR thermometers with dendrometer and sap flux measurements on the same trees. Our comparison reveals strong correspondence between dendrometer-derived tree water deficit (TWD) and the TIR-based CWSI computed for the same tree, confirming the utility of the CWSI as a stress detection tool.
We also put into perspective the CWSI computed based on continuous measurements with values obtained from two drone flights, in order to answer the following questions:
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At what spatial resolution (leaf, crown, stand) can meaningful CWSI values be derived?
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How to derive a suitable (unstressed) base line, either based on continuous data or the ensemble of data points in a set of images?
High resolution drone data captured substantial within-canopy variation and noise, but also non-physical results, compared to expectations derived from other data, established theoretical basis for crops, and a new theoretical basis for forests. Our analysis takes us another step towards the ability to quantify tree drought stress when and where it first occurs.
How to cite: Schymanski, S. J., Keim, R. F., Schlerf, M., Iffly, J.-F., Bossung, C., and Ronellenfitsch, F.: Quantifying Drought Stress in a Temperate Beech Forest Using the CropWater Stress Index derived from Thermal-Infrared Remote Sensing, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20582, https://doi.org/10.5194/egusphere-egu25-20582, 2025.
The environment constantly changes due to natural factors and human activity. Defining mechanisms of its functioning and tendencies of the changes has a significant theoretical and practical value. Plants substantially affect water cycle in the moderate climate zone. The role of canopy in transforming precipitation is connected to the process of interception. Moreover, tree crowns accumulating snow, especially in mountains, form excellent water reservoirs in winter.
Mountain areas gain additional water also due to cloud water deposition. This process is particularly effective in coniferous trees, with greater receptive area and better conditions for brushing out water droplets from clouds. The phenomenon can be observed in the central part of the Świętokrzyskie Mountains (SE Poland) mainly from October till April, with maximum intensity in November, when low level clouds are often present in the area elevated above the sea level. Additionally, the values of relative air humidity noted in January – March frequently reach 100%. Conifers, with greater receptive area and assimilation organs present throughout the year, caused an increase in mineralisation of water passing through their crowns. The values were from 1.9x (Scots pine) to 2.8x (silver fir) higher than the concentrations noted in precipitation. Increased mineralisation resulted from “brushing out” air pollutants by tree crowns and the “leaching effect” – washing off mineral and organic substances from plant organs by acidified rainwater. The load of majority of analysed substances reaching coniferous forest floor was higher than that in precipitation, and the values were reflected in the enrichment factor.
Research conducted in the Świętokrzyskie Mountains since 1994 indicates that the changing human pressure, including elevated deposition of acidifying substances, caused deterioration of forest health condition and acidification of soils.
How to cite: Kozłowski, R., Przybylska, J., Szwed, M., and Kozłowska, A.: The role of tree stands in transforming precipitation in the conditions of climate change and multi-directional human pressure, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17093, https://doi.org/10.5194/egusphere-egu25-17093, 2025.
It is of great significance to assess and project the respective impacts of land use change (dQ_Landuse) and climate change (dQ_Climate) on streamflow (Q) for water resources management. In this study, we used elasticity differential analysis approach and physical processes based distributed parameter watershed hydrological model to quantify the relative contributions that land use change and climate variability have on the decadal streamflow dynamics of the Chaohe watershed with the area of 4854km2 located in the northern China. Furthermore, the watershed hydrological model was applied to investigate the future hydrographic characteristics driven by downscaled precipitation and temperature projected by General Circulation Models (GCMs) under three emissions scenarios. The result suggested that watershed streamflow, compared with the reference period from 1963-1979, greatly decreased during 1980–1989 and 2000–2008, whilst it slightly changed during 1990–1999. The insignificant streamflow change for 1990–1999 was due to the effects of lower soil water storage capacity than that of other periods on the hydrological impact of land use change. In addition, dQ_Climate for 1980–1989 and 2000–2008 were different between the approaches: dQ_Climate were almost similar to dQ_Landuse for these two periods according to eco-hydrological approach, whilst dQ_Climate from the differential elasticity-based analysis only 33% and 45% and from modelling 51% and 78% for 1980–1989 and 2000–2008, respectively. The future climate exhibits a drier and warmer trend in the summer monsoon period contrasting with other seasons in the watershed. Precipitation will decrease by 47.5–57.2 mm during the summer monsoon period while increasing annually. Future summer streamflow will decrease accordingly driven by increased evapotranspiration due to the rising temperature. An increased dispersion coefficient of streamflow also indicates more dramatic variations in summer than that of other seasons. The annual streamflow magnitude with a 5-year return period increases significantly (p < 0.01), indicating a reduced risk for future water shortages. However, the magnitude of streamflow will decrease with the prolonged return periods (p<0.01). Our study highlights the critical importance to interpret the hydrological impacts by different approaches with great care and to predict the seasonal variability of streamflow characteristics for developing adaptive resource management and hazard relief strategies as the hydrological impacts of land use change and climate change are temporally varied.
How to cite: Zhang, Z., Wang, S., and Cao, W.: Streamflow responses of land use and climate change in a watershed of Northern China: implications for adaptive watershed management, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17989, https://doi.org/10.5194/egusphere-egu25-17989, 2025.
Climate changes and biotic responses are increasingly undermining forest health worldwide. One such impact includes the intensification of infestations by semiparasitic plants like mistletoe (Viscum album L.). Mistletoe infestations can significantly disrupt the water balance of forest ecosystems, particularly in commercial forests. In 2023, mistletoe damaged 133.7 thousand hectares of forests in Poland, primarily affecting Scots pine (Pinus sylvestris L.). This study examined the water-holding capacity of tree canopies in mistletoe-infested and healthy stands of Scots pine and silver fir (Abies alba Mill.) in southeastern Poland, where air pollution is minimal, and mistletoe presence was rare before 2019. Using specialized imaging software (WinRhizo® Regular 2021 and WinSeedle® Pro 2022), we quantified the surface area of conifer shoots, needles, and mistletoe foliage, while laboratory simulations under controlled conditions measured water retention capacity.
Results indicate that healthy Scots pine canopies store 2.6 mm of water (20.3% of simulated rainfall), while silver fir retains 1.5 mm (14.8%). Mistletoe on pine and fir canopies stores substantially more water, 3.8 mm (24.9%) and 3.3 mm (29.5%), respectively. These findings suggest that mistletoe infestation increases canopy water retention capacity by up to 15%. The dynamic filling and emptying of this additional 1.5 mm of water storage capacity by mistletoe-infested canopies could result in an additional 5-10 % reduction in water reaching the forest floor, emphasizing the ecological significance of mistletoe in altering interception and infiltration processes.
These findings highlight the need to integrate mistletoe infestation into forest water balance models, especially as drought conditions intensify. A deeper understanding of Viscum album’s role in exacerbating drought stress will enhance predictions of forest resilience and support the development of forest management strategies that safeguard water resources and the economic sustainability of affected stands
How to cite: Klamerus-Iwan, A., Van Stan, J., Kozłowski, R., Netzel, P., Banach, J., Stopyra, M., Słowik-Opoka, E., and Urban, J.: Mistletoe Infestation in Conifer Stands: Implications for Forest Water Balance, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18171, https://doi.org/10.5194/egusphere-egu25-18171, 2025.
Snow algae (SA) significantly influence snowmelt dynamics and biogeochemical cycles by reducing snow albedo and modulating concentration of some ions, thereby accelerating snow melt. Conversely, SA proliferate during snowmelt when sufficient liquid water is present in the snowpack, and adequate solar radiation fuels photosynthesis. This study investigates the diversity of SA with focus on forest species and their role in hydrological regimes within forested high mountain regions and examines their connection to climate change impacts.
We analysed a historical database of SA bloom occurrences (since 1976) in the Krkonoše Mountains (NE Czechia), correlating these events with meteorological conditions – such as daily temperature sums over 3 to 5 days, snow depth, and solar radiation – to identify the predictors of SA bloom onset and development. Our findings suggest that SA blooms require prolonged melting periods to develop, and ongoing climate change, characterized by shorter winters and earlier, more frequent melting periods, may significantly affect their occurrence.
To further explore the relationship between snowmelt timing and SA occurrence, we established a study plot in the Labský důl Valley in the Krkonoše Mountains. Beginning in early March 2024, earlier than in previous seasons due to warm and rainy weather, we conducted weekly to bi-weekly sampling. Analyses included snow chemistry (pH, conductivity, major ions, total phosphorus and nitrogen, dissolved organic carbon) and ITS2 rDNA metabarcoding combined with light microscopy to monitor seasonal development of SA taxonomic composition and life cycle stages.
The overall objectives of this project are to evaluate the relationships between SA blooms, snow cover dynamics, and microclimate data; correlate SA occurrence with microclimatic conditions across a broader geographical scale; and develop models to predict SA distribution below the timberline in Central Europe. Our findings will enhance the understanding of the interplay between SA and snowmelt, contributing to predictive models of SA distribution. This knowledge will inform conservation strategies and improve hydrological forecasting in mountainous environments.
How to cite: Juras, R., Hejduková, E., Procházková, L., Man, M., Kociánová, M., and Nedbalová, L.: The role of snow algae in snowmelt dynamics in mountain forests, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17570, https://doi.org/10.5194/egusphere-egu25-17570, 2025.
Extensive afforestation since the mid-19th century has contributed to the desiccation of former wetland and mire ecosystems in Europe. Restoration of wet conditions is expected from transformation of evergreen coniferous forest characterized by high interception and transpiration to deciduous forest and low vegetation. The quantification of the spatial effects of such forest transformation on groundwater levels is difficult because evapotranspiration is usually calculated from atmospheric parameters only, while transpiration by plants and trees is partly determined by available soil moisture and groundwater. The aim was to develop a transient 3-D model that can calculate the effects of land use changes on groundwater levels and fluxes in time and space. For this purpose, a transient 3-D groundwater model (Modflow) per time step was linked to a 1-D top Model for Recharge (TMR). Recharge was calculated here from precipitation and reference evaporation, interception and evaporation related to vegetation (season LAI), transpiration depending on available soil moisture in the root zone and groundwater level per time step. Negative recharges were calculated at water levels just below or above ground level partly due to water losses by overland flow. The TMR model has been validated with time series (> 30 years) of groundwater level observations at various locations. A Modflow model of 5 model layers, cell size 10 x 10 m, time step 1 day, during 10 years has been built of a 55 km2 large pilot area in Niedersachsen (DE) using Python and the PCRaster-Modflow (https://pcraster.geo.uu.nl/) platform. The LAI is classified from available forest stand data and land use maps. Soil parameters are based on the soil map of Germany (1:50k). The developed TMR-MF model has been validated for the period 2007-2016 by comparing calculated groundwater levels with measured levels at 86 locations. Mean deviation was 0.038 m. (Stdev.: 0.309 m., R2=0.9929). This model was used to quantitatively spatially analyse the effectiveness of forest conversion scenarios on eco-hydrological restoration of a dried-up stream valley lowland bog.
Acknowledgments: This project was created in collaboration with Niedersächsische Landesforsten (NLF) Fachbereich Entwicklung & Innovation and the Abteilung Wasserbewirtschaftung und Wasserrechte Oldenburgisch-Ostfriesischer Wasserverband (OOWV). Meteorological data were obtained from the Deutscher Wetterdienst.
How to cite: Bleuten, W. and Schmitz, O.: Top Model for calculating groundwater Recharge (TMR) based on vegetation LAI, soil properties and groundwater depth coupled with 3-D dynamic groundwater modeling using PCRaster-Modflow, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11454, https://doi.org/10.5194/egusphere-egu25-11454, 2025.
Forest ecosystems play a crucial role in regulating large-scale hydrological and biological cycles on the land surface. They currently store approximately 45% of the total carbon on land, sequester around 80 Pg of carbon annually, responsible to 70–80% of total terrestrial evapotranspiration. Modeling the coupled carbon and water dynamics of forests remains a significant challenge due to their structural complexity. Approximately 25% of forests are rejuvenating, short-stature forests recovering from recent disturbances, while older forests are typically highly diverse, with multiple species competing for resources. To effectively model these dynamics, advancements in representing structural complexity are essential. These models need to adopt parsimonious approaches that account for the limited availability of data while maintaining accuracy and scalability.
Among the various simulation approaches, we have selected the Tethys-Chloris (T&C) model in this study. The T&C model offers several advantages, such as highly customizable parameters for representing multiple species and detailed soil carbon pools to simulate soil carbon dynamics and soil biogeochemistry. These features make the T&C model a promising tool for accurately simulating and predicting forest ecosystem behaviour. However, its forest demography component is currently simplified, assuming uniform tree heights and properties within the same plant functional type (PFT). While this assumption works well for fully mature forests, it is inadequate for forests undergoing large-scale recruitment, growth, or mortality. These dynamic forests are increasingly common due to anthropogenic activities and climate change.
To address this limitation, we propose changing the original cohort-based forest demography in the T&C model. We plan to develop a new parsimonious forest demography scheme to represent the dynamics of forest ecosystems transportable to other land surface models. This scheme will utilize a tiling approach to represent species in the forest. In this scheme, we will redistribute research forests to a cohort-based allocation of tree species to represent the ecosystem's diversity and dynamics. The perfect plasticity approximation will represent the canopy's movement and closure. The interspecies competition for light, water and nutrients between cohorts of different heights and densities will be used to make simulations closer to reality.
To validate these enhancements to the T&C model, we are utilizing regional forest data from diverse climates, including flux data collected from observatories in North American, European and Amazon forests. Incorporating more diverse and precise datasets will further enhance the accuracy of forest ecosystem simulations and predictions.
How to cite: Yan, J., Mijic, A., and Paschalis, A.: Forest Demography and Ecohydrological Dynamics Incorporating in the T&C (Tethys-Chloris) model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16340, https://doi.org/10.5194/egusphere-egu25-16340, 2025.
Posters virtual: Thu, 1 May, 14:00–15:45 | vPoster spot A
EGU25-1681 | Posters virtual | VPS10
Deep soil water use can compensate drought effect on gas exchange in dry years than in wet years for dryland tree plantationsThu, 01 May, 14:00–15:45 (CEST) | vPA.12
Analyzing deep soil water use (DSWU) response to precipitation change and its impact on tree physiology is necessary to disentangle tree mortality mechanisms, especially in drylands. In this study, a process-based model parameterized with in-situ measured fine root distribution data for 0-2000 cm and a root-cutting (below 200 cm) numerical experiment were used to explore DSWU strategies across different precipitation years and its contribution to total water consumption, as well as its relationship to tree gas exchange traits in mature apple (Malus pumila Mill) and black locust (Robinia pseudoacacia L.) plantations in both a wetter (Changwu, 583 mm) and a drier (Yan’an, 534 mm) sites on China’s Loess Plateau. Results showed that DSWU at 200-2000 cm depth in different precipitation years of both species mainly occurred during the early growing seasons. On average, DSWU contributed 22.9% and 25.1% to the total water consumption of apple trees and black locust, respectively, and its contribution increased to 26.0% and 36.7% in extremely dry years. Moreover, the lack of DSWU significantly decreased (p<0.05) stomatal conductance (by 16.9%, 16.9%, 47.4% and 11.4%, respectively) and photosynthetic rates (by 37.1%, 20.1%, 28.5% and 16.4%, respectively) of Changwu apple trees, Yan’an apple trees, Changwu black locust and Yan’an black locust in extremely dry years. Similar reductions occurred only in Yan’an for both tree species in normal years. In contrast, no significant differences were found in gas exchange traits in extremely wet years. Our results highlight that DSWU is an important strategy for plantations in deep vadose zone region to resist extreme drought.
How to cite: Zhao, X., Shao, X., and Gao, X.: Deep soil water use can compensate drought effect on gas exchange in dry years than in wet years for dryland tree plantations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1681, https://doi.org/10.5194/egusphere-egu25-1681, 2025.
