BG1.8 | Tropical forests in transition - ecosystems of global significance
EDI
Tropical forests in transition - ecosystems of global significance
Convener: Eliane Gomes Alves | Co-conveners: Laynara F. Lugli, Erin Swails, Santiago Botía, Tin Satriawan, Flavia Durgante, Sung Ching Lee
Orals
| Tue, 16 Apr, 16:15–17:45 (CEST)
 
Room 2.23
Posters on site
| Attendance Tue, 16 Apr, 10:45–12:30 (CEST) | Display Tue, 16 Apr, 08:30–12:30
 
Hall X1
Posters virtual
| Attendance Tue, 16 Apr, 14:00–15:45 (CEST) | Display Tue, 16 Apr, 08:30–18:00
 
vHall X1
Orals |
Tue, 16:15
Tue, 10:45
Tue, 14:00
Tropical ecosystems are biomes of global significance due to their large biodiversity, carbon storage capacity, and their role in the hydrological cycle. Historic and recent human activities have, however, resulted in an intensive transformation of the tropical ecosystems in the Amazon, Central America, Central Africa and South East Asia impacting the cycling of nutrients, carbon, water, and energy. Understanding their current functioning at process up to biome level in its pristine and transformed state is elemental for predicting their response to changing climate and land use, and the impact this will have on local up to global scale.
The purpose of this session is to unite scientists investigating the dynamics of tropical ecosystems, employing a range of remote and on-site observational, experimental, modelling, and theoretical approaches. We are particularly interested in studies evidencing/documenting how tropical biomes, at the local or regional scale, respond to human-induced disturbances and climate change. In particular, spatial gradients and temporal scales that mirror global changes. Moreover, we encourage the presentation of innovative interdisciplinary methodologies and techniques that have the potential to reshape existing paradigms, thereby paving the way for exciting new avenues of exploration.

Orals: Tue, 16 Apr | Room 2.23

Chairpersons: Laynara F. Lugli, Erin Swails, Eliane Gomes Alves
Introduction
16:15–16:25
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EGU24-14707
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Highlight
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On-site presentation
Scott Saleska, Natalia Restrepo-Coupe, Kleber Silva Campos, Luciana Alves, Valeriy Ivanov, Marcos Longo, Raimundo de Oliveira Jr., Rodrigo Silva, Marielle Smith, Raphael Tapajos, and Tyeen Taylor

The risk of a tipping point for Amazon forests — a perturbation threshold beyond which abrupt, irreversible (or difficult to reverse) changes in forest function and large-scale tree die-off occur — motivates much recent Amazon forest science and policy work to understand and reduce the risk. However, virtually all the science to date focuses on tipping points as a basin-wide phenomenon. To understand how large-scale tipping points may be triggered, we urgently need to study mechanisms of tipping point onsets at local-scales in pivotal forests.

 Here, we used 12+ years of observations (spread over two decades from 2001-2020) of water and energy fluxes from eddy covariance measurements, and associated ecological and meteorological observations in the eastern Amazon basin, to investigate the potential for hydrological extremes to induce a “local scale” tipping point.  We focused on forest transpiration capacity (the capacity of vegetation to convert available energy into latent heat, quantified as the ratio of transpiration to incoming radiation, T/R) because transpiration in eastern Amazon forests is the basis for precipitation recycling on which forests to the west depend.

Our observations encompassed two strong El Niño droughts, in 2002-2003 and in 2015-2016. Both events were characterized by similarly reduced rainfall; however, the 2015 El Nino was further amplified by an ongoing warming trend, which made for a hotter drought with higher atmospheric vapor demand, exacerbating the drought effects on the forest. 

This amplification of drought by warming was apparently sufficient to cause widely divergent responses to the two droughts.  The forest responded positively to the 2002 drought, with increases in canopy conductance (Gs) and in evapotranspiration, consistent with a stable forest transpiration capacity (T/R) that saw proportional increases in T in response to higher R. By contrast, the transpiration capacity (sustained through two decades of previous dry seasons and the 2002 El Nino drought) collapsed during the 2015 drought.  Notably, the forest’s ability to transpire did not return with the rain as the drought ended, but remained low for several years. Thus, we concluded that the difference between the 2002 and 2015 El Nino’s was sufficient to push the forest past a “tipping point” threshold in forest transpiration function, into an alternate state of reduced function in which it remained trapped until the forest could regenerate the canopy with new leaves.  

This discovery of the phenomenon of local-scale short-term tipping point dynamics in forest canopy function opens the door to investigating and understanding how basin-scale tipping points may emerge from local phenomena, and how careful local observations may provide early warnings of impending larger-scale forest vulnerability.

How to cite: Saleska, S., Restrepo-Coupe, N., Silva Campos, K., Alves, L., Ivanov, V., Longo, M., de Oliveira Jr., R., Silva, R., Smith, M., Tapajos, R., and Taylor, T.: Do local-scale climate tipping points exist in Amazon forests, and can they warn of impending basin-scale tipping point vulnerability?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14707, https://doi.org/10.5194/egusphere-egu24-14707, 2024.

16:25–16:35
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EGU24-14471
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On-site presentation
Elsa Ordway, Gregory Asner, David Burslem, Stuart Davies, Simon Lewis, Mohamad Mohiza, Nilus Reuben, O'Brien Michael, Phillips Oliver, Qie Lan, Sabrina Russo, Xiangtao Xu, Marcos Longo, and Paul Moorcroft

Spatial heterogeneity in tropical forest productivity and resulting rates of carbon uptake and storage emerge from variation in ecosystem structure and functional traits reflecting differences in climate, edaphic conditions, evolutionary history, and natural and anthropogenic disturbance histories. Yet, models poorly represent this heterogeneity. Remote sensing data provide landscape-scale measures of tropical forest heterogeneity in structure and functional traits that can be used to advance terrestrial biosphere models. To examine whether forest functional traits related to photosynthetic capacity can be used to improve predictions of tropical biomass dynamics and carbon fluxes, we parameterized the Ecosystem Demography model version 2.2 (ED2.2) using canopy traits derived from visible to shortwave infrared (VSWIR) airborne imaging spectroscopy data across an edaphic gradient in Borneo. We find significant site-level differences in relationships between SLA and foliar nutrient concentrations, suggesting that remotely sensed foliar traits can be used to capture variation in photosynthetic capacity at large, edaphically varying spatial scales. We further show that plant functional types parameterized with site-constrained trait values yield more accurate predictions of canopy demography, forest productivity and above-ground biomass dynamics than simulations that depend solely on parameterization of edaphic conditions. However, the most substantial improvements result from allowing for site-level variation in background disturbance rates in the model. Our study reveals the importance of capturing tropical forest heterogeneity in terrestrial biosphere models, particularly as it relates to nutrient availability and disturbance processes. 

How to cite: Ordway, E., Asner, G., Burslem, D., Davies, S., Lewis, S., Mohiza, M., Reuben, N., Michael, O., Oliver, P., Lan, Q., Russo, S., Xu, X., Longo, M., and Moorcroft, P.: Constraining uncertainty in terrestrial tropical carbon flux dynamics requires capturing local biogeochemical influences on structure and function, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14471, https://doi.org/10.5194/egusphere-egu24-14471, 2024.

16:35–16:45
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EGU24-8693
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ECS
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On-site presentation
Raquel González Armas, Daniël Rikkers, Hugo de Boer, Vincent de Feiter, Sebastiaan de Haas, Oscar Hartogensis, Wouter Mol, Martin Janssens, Bert Heusinkveld, Chiel van Heerwaarden, Hella van Asperen, Luiz Machado, Cléo Quaresma, Eric Bastos Görgens, and Jordi Vilà Guerau de Arellano

Land-surface representations in weather and climate models simplify the characterization of vegetation as a single layer with bulk environmental conditions. This approach overlooks the vertical variability in leaf traits and environmental conditions within the canopy. This research explores the vertical variability of plant ecophysiology and environmental measurements within the Amazon tropical rainforest during daytime, specifically at the ATTO site, during the late dry season.

To characterize the canopy and its vertical variability, we categorized the canopy into three layers: the top layer (approximately the upper third of the canopy, 18-27 m), the medium layer (approximately the medium third of the canopy, 9-18 m), and the low layer (approximately the lower third of the canopy, 0-9 m) where leaf gas exchange measurements were conducted. Utilizing these layers, we developed a multi-layer model representation that calculates water and CO2 fluxes based on within canopy on-site observations. We conducted sensitivity analyses of the rainforest multi-layer representation to discern the significance of capturing vertical variability in leaf traits and environmental conditions for deriving net fluxes of water and CO2 of the forest.

Current results show that measured leaf traits exhibit vertical variation within the canopy, indicating larger productivity in the top layer compared to the medium and low layers. Environmental conditions, such as incoming radiation in the top layer, fluctuate due to cloud presence. Temperature peaks in the top layer and reaches a minimum at mid-canopy. This results in a non-uniform mixing of the canopy air, maintaining a stable layer within the forest canopy that can potentially affect the distribution of scalars within the canopy. Ongoing analyses explore the similarities and differences between the CO2 exchange between the multi-layer representation and CO2 fluxes from eddy covariance systems, as well as the sensitivity of the former to vertical variability in leaf traits and environmental conditions. By doing so, we aim to gain knowledge on the relevance (or irrelevance) of characterizing vertical variability in land-surface representations and on important processes that may not be well captured yet by land-surface representations.

How to cite: González Armas, R., Rikkers, D., de Boer, H., de Feiter, V., de Haas, S., Hartogensis, O., Mol, W., Janssens, M., Heusinkveld, B., van Heerwaarden, C., van Asperen, H., Machado, L., Quaresma, C., Bastos Görgens, E., and Vilà Guerau de Arellano, J.: Vertical Variability in Leaf Traits and Environmental Conditions: Implications for Evapotranspiration and Net Ecosystem Exchange above the Amazon Rainforest, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8693, https://doi.org/10.5194/egusphere-egu24-8693, 2024.

16:45–16:55
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EGU24-5418
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On-site presentation
Anja Rammig and David Lapola and the AmazonFACE Team

Tropical rainforests play an important role in the global carbon cycle. They store massive amounts of biomass in their trees and soils, and contribute to climate mitigation by removing carbon from the atmosphere through photosynthesis. It is assumed that plant responses to rising atmospheric CO2 concentrations may have induced an increase in biomass and thus, increased the carbon sink in forests worldwide. Rising CO2 directly stimulates photosynthesis (the so-called CO2-fertilization effect) and tends to reduce stomatal conductance, leading to enhanced water-use efficiency, which may provide an important buffering effect for plants during adverse climate conditions and also have implications for water resources by reducing the loss of soil moisture through transpiration. For these reasons, current global climate simulations consistently predict that undisturbed tropical forests will continue to sequester more carbon in aboveground biomass. However, several lines of evidence point towards a decreasing carbon sink strength of the Amazon rainforest in the coming decades, potentially driven by nutrient limitation, droughts or other factors. Mechanistically modelling the effects of rising CO2 in the Amazon rainforest are hindered by a lack of direct observations from ecosystem scale CO2 experiments. To address these critical issues, we are currently building a free-air CO2 enrichment (FACE) experiment in an old-growth, highly diverse, tropical forest in the Brazilian Amazon and we here present our main hypotheses that underpin the AmazonFACE experiment.  We focus on possible effects of rising CO2 on carbon uptake and allocation, phosphorus cycling, water-use and plant-herbivore interactions, and discuss relevant ecophysiological processes, which need to be implemented in dynamic vegetation models to estimate future changes of the Amazon carbon sink. We give an update on the state of the experiment construction, present the sampling strategy and discuss our approach to upscale tree-level responses to stand scale. 

How to cite: Rammig, A. and Lapola, D. and the AmazonFACE Team: AmazonFACE – A large-scale Free Air CO2 Enrichment Experiment in the Amazon rainforest , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5418, https://doi.org/10.5194/egusphere-egu24-5418, 2024.

16:55–17:05
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EGU24-19868
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ECS
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On-site presentation
Renaud Koukoui, Ossénatou Mamadou, Djideme Franck Houénou, Bernard Heinesch, Jean-Martial Cohard, Mamadou Bousso, Christophe Peugeot, and Basile Kounouhéwa

In the context of global warming and rapid increase of population particularly in West Africa where forest ecosystems are threatened by land use conversion, understanding the biophysical variables influencing the ecosystem respiration (Reco) becomes vital for predicting the carbon balance in response to climate change. Using the Eddy Covariance method, and without an automatic chamber system, a key step to determine Reco is to use nighttime Net Ecosystem Exchange (NEE) data to establish a functional relationship using Reco main driver’s as an input.  However, to ensure that the input variable(s) used in this relationship is the most relevant governing this process, especially in tropical regions where both data and studies are scarce, it remains therefore an important prerequisite to examine the relative importance of potential drivers. This prior analysis is especially needed because: (1) the main driver may differ according to the climate and locations; (2) collinearity between some potential drivers could be a complex issue in identifying the main one; (3) the scale of influence of these drivers on the nighttime CO2 emission at some sites is still unknown. In our study, we therefore investigated the relative importance and scale of influence of soil moisture (Hsoil) and temperature (Tsoil) at different depths on the nighttime NEE. Since variations of the net CO2 flux exchanged can differ from one site to another, in this study we used data acquired from 2008 to 2017 above two contrasted ecosystems: a mixed culture (Nalohou, lat. 9.74°N, long. 1.60°E) and an open clear forest (Bellefoungou, lat. 9.79°N, long.1.72°E) located in Sudanian climate, Northern Benin. Both sites belong to the AMMA-CATCH (African Monsoon Multidisciplinary Analysis-Coupling of the Tropical Atmosphere and Hydrological Cycle) observatory. Two methods have been then deployed: the first one which is the Mutual Information, was used to identify the relative importance of Hsoil and Tsoil in controlling the nighttime NEE; the second one, the wavelet transform allows determining the scales of influence of these variables on nighttime NEE. We found that periodicity of nighttime NEE response to the two variables differs according to the season.  Soil moisture appears as the most important variable in the nighttime NEE variation whatever ecosystems and seasons analyzed. During wet seasons, nighttime NEE response to soil moisture exhibits a periodicity lower than 64 nights with synchronization every 07 nights, while this synchronization can extend from 12 to 14 nights during the dry season. This fast response of nighttime CO2 emissions to soil moisture during the wet season results from a significant increase in precipitation. During the dry seasons, without precipitation, soil moisture decreases, and this reduces the water available to plant growth and microorganism activity, thus reducing the amount of CO2 emitted. Moreover, sporadic rainfall events rewet the soil, leading to spontaneous CO2 emissions. Soil temperature is secondary in importance, but its impact can vary; it is less relevant during the dry season, or more redundant in the wet season, for both sites. It is also out of phase with nighttime CO2 emissions regardless of the season.

How to cite: Koukoui, R., Mamadou, O., Houénou, D. F., Heinesch, B., Cohard, J.-M., Bousso, M., Peugeot, C., and Kounouhéwa, B.: Assessing the relative importance of soil moisture and temperature on the nighttime CO2 flux: two contrasted ecosystems study cases in West Africa, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19868, https://doi.org/10.5194/egusphere-egu24-19868, 2024.

Discussion
17:05–17:15
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EGU24-20160
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Highlight
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On-site presentation
Hans Verbeeck, Sruthi Moorthy Krishna Moorthy, Kim Calders, and Félicien Meunier

Lianas (woody vines) are an iconic feature of tropical forests as they represent on average 25% of all woody stems. Lianas are structural parasites that use the stems of self-supporting plants to reach the top of the canopy. From there, they strongly compete with trees for above- (light) and below-ground (water nutrients) resources. Despite their importance, lianas are completely neglected by terrestrial models. To fill this gap, we developed the first mechanistic representation of lianas in a state-of-the-art vegetation model, the Ecosystem Demography model version 2 (ED2.2). Model simulations revealed the critical role of liana for forest biogeochemical cycles (e.g., tree gross and net productivity decreases when lianas are present with the magnitude of the reduction varying with liana abundance) but also for the energy balance (e.g., lianas increase forest albedo and buffer the microclimate of forest understorey). 

 

In addition, we used a combination of terrestrial lidar scanning and a meta-analysis of field and drone observations of tree shape and structure to evaluate the impacts of lianas on tree allometries. In total, we gathered 45,000+ observations of individual tree height, 1.000+ observations of tree crown areas and 150+ tree quantitative structure models over more than 40 sites spread over the tropics, together with liana infestation levels. Those datasets converged to identify a key role of lianas on the shape and structure of tree in tropical forests, independently of the tree species. Liana heavy infestation was responsible for a strong reduction of tree height (-10.7%), crown area (-12.6%), branch length (-45.9%), and overall aboveground carbon stocks (-19.6%). We estimated the global potential liana impact on aboveground tree carbon stocks to be 13.5 Tg over the tropics, or about 7% of the total tropical forest biomass.

 

How to cite: Verbeeck, H., Krishna Moorthy, S. M., Calders, K., and Meunier, F.: Investigating the impact of lianas on global tropical forests, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20160, https://doi.org/10.5194/egusphere-egu24-20160, 2024.

17:15–17:25
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EGU24-14880
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Highlight
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On-site presentation
Maria J. Santos and Diego Villamaina

The megadiverse system of the Amazon contributes to many local and global ecosystem processes with potential to trigger an irreversible shift in the functioning of our planet. Yet, Amazon’s biodiversity is complex and remains mostly understudied. Biodiversity distribution patterns likely affect the functioning of this crucial system, yet large scale systematic assessments are still lacking. Herein we examine how can optical remote sensing contribute to understanding biodiversity patterns in the Amazon. We use the spectral diversity approach to map the heterogeneity of spectral signatures as a proxy for heterogeneity in canopy composition using Sentinel-2 imagery over the entire basin. Our map is able to reproduce patterns of primary, secondary and deforested areas, and within the forest areas, the patterns of spectral richness and spectral turnover resemble those expected for the Amazon system, with rapid turnover in species composition closer to the waterways and more stable plant community compositions away from the waterways. We then examine whether the locations with higher or lower spectral variability correspond to different community and trait compositions. We examine the relationship between spectral richness and turnover and the presence of hyperdominant trees in the Amazon. We also examine the multivariate trait space including Specific leaf area (SLA), Leaf dry matter content (LDMC), Leaf nitrogen content (LNC), and Leaf Phosphorous content (LPC) along the gradient of spectral variability to find that trait syndromes vary along the gradient of spectral diversity. These results show that biodiversity biodiversity gradients among the Amazon may explain differences in ecosystem functioning and that approaches such as the spectral heterogeneity may start to shed some light into such relationships, especially over entire and important ecosystems like the Amazon. Further examinations of these processes and relationships are therefore required and will contribute to our better understanding of the feedbacks between biodiversity and earth system processes.

How to cite: Santos, M. J. and Villamaina, D.: Biodiversity-mediated ecosystem functioning in the Amazon: a remote sensing approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14880, https://doi.org/10.5194/egusphere-egu24-14880, 2024.

17:25–17:35
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EGU24-11089
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ECS
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On-site presentation
Jessica Finck, Dan Frederik Lange, Beto Quesada, Bruno Takeshi Tanaka Portela, Sávio José Filgueira Ferreira, Fernando Dini Andreote, Erika Kothe, and Gerd Gleixner

Tropical rainforests such as the Amazon are of high importance as a global carbon sink. Due to its well-known nutrient limitation, the Amazon rainforest relies heavily on rapid microbial decomposition of biomass to release freshly available nutrients for plant growth. Despite the fundamental importance of decomposers for this ecosystem, little is known about the biodiversity of such microbiomes, their functional activity, and spatial and seasonal variability. We used 16S rDNA and ITS rDNA sequencing to analyze the microbial communities of the Amazon’s terra firme and the much drier white-sand ecosystems during the dry and wet seasons in 2022. Bacterial microbiomes differed significantly between seasons, displaying lower bacterial species richness and diversity in response to seasonal drought. In contrast, fungal richness and diversity differed strongly between sites, but were less affected by seasonal variation, suggesting their hyphae network and associations with plants as potential protectors against drought effects. Fungal and bacterial communities alike showed lower abundance of taxa involved in organic matter decomposition following seasonal drought. These changes were also reflected at the functional level, with samples collected during the dry season and at white-sand sites featuring lower abundances of decomposition and denitrification pathways. Soil hydro-chemical data also emphasizes how prolonged drought may limit soil nutrient supply via local microbiomes. Our results suggest that the reduced nutrient availability and soil connectivity during drought and within the white-sand ecosystem lower microbial activity and functional redundancy, henceforth demonstrating a strong impact of ecosystem type and drought on tropical microbiomes and their functional capacities. Our results further highlight that the observed increase in droughts in the Amazon rainforest may additionally limit nutrient supply through the microbial community, limiting carbon sequestration in the ecosystem with negative consequences for the global climate system.

How to cite: Finck, J., Lange, D. F., Quesada, B., Portela, B. T. T., Ferreira, S. J. F., Andreote, F. D., Kothe, E., and Gleixner, G.: Seasonal drought reduces microbial diversity and functional richness in the Amazon, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11089, https://doi.org/10.5194/egusphere-egu24-11089, 2024.

17:35–17:45
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EGU24-10409
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ECS
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Highlight
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On-site presentation
Nadine Keller, Andrea Jilling, Jun Ying Lim, Lian Pin Koh, Elia Godoong, and Mark A. Anthony

Restoring formerly degraded ecosystems is a promising nature-based solution to mitigate climate change and ensure the provisioning of ecosystem services. Consequently, ecosystem restoration is prominent on both governmental and private agendas (e.g., the Bonn Challenge, airline carbon off-sets by planting trees). Two opposing strategies are employed to promote forest restoration: active versus passive (e.g. natural regeneration) restoration. Assessing how these two approaches influence biodiversity hot spots such as tropical rainforests is uniquely important, but the benefits and limitations of these two techniques have not been thoroughly compared.

Among all tropical moist forests globally, forests of Asia-Oceania have experienced the highest disturbance rates in the past three decades, among which Sabah, Malaysian Borneo, contains forests with past managements to strategically assess long-term forest recovery following active and passive restoration strategies.

How overall forest carbon balance, including carbon storage in the soil, is affected by active versus passive restoration, remains a blind spot not only at this site, but also globally. Given that up to half of the total carbon stored in secondary tropical rainforests can be stored belowground, and that this carbon has slower turn-over rates than above-ground vegetation, Sabah is a perfect testing ground to examine how common forest restoration influences below-ground carbon dynamics and total forest carbon balance.

To address this, we collected soil samples in 15 actively restored and 15 naturally regenerating forest plots in INFAPRO, a restoration project in Sabah. This site was severely, selectively logged for two decades and then actively restored by planting (mainly) Dipterocarpacaea (i.e., diptertocarps) seedlings more than 20 years ago. These trees associate with ectomycorrhizal fungi that mediate important soil biochemical cycles as root-inhabiting tree symbionts.

At this restoration site, active restoration enhanced tree diversity, promoted rare species, and increased above-ground carbon density in living vegetation in comparison to natural regeneration. We hypothesize that active restoration, including the planting of diptertocarps, further enhances the presence of ectomycorrhizal fungi, leading to a suppression of free-living microbial decomposition of plant litter inputs (i.e., the Gadgil effect), and an increase in total soil carbon storage. While this may increase total soil carbon storage, the more persistent fraction that is mineral-associated may decrease. This is due to slowed plant litter decomposition and thus less production of compounds that absorb onto mineral surfaces in addition to less microbial necromass inputs sticking to minerals due to the lower growth efficiency by ectomycorrhizal fungi compared to free-living microbes.

This knowledge on soil carbon storage and its persistence is a much needed contribution to holistic assessments of active restoration compared to natural regeneration. Empirical results on soil carbon analyses will be generated by the time of the EGU conference.

How to cite: Keller, N., Jilling, A., Lim, J. Y., Koh, L. P., Godoong, E., and Anthony, M. A.: The Blind Spot in active tropical forest restoration: unknown impacts on soil carbon, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10409, https://doi.org/10.5194/egusphere-egu24-10409, 2024.

Final Discussion

Posters on site: Tue, 16 Apr, 10:45–12:30 | Hall X1

Display time: Tue, 16 Apr, 08:30–Tue, 16 Apr, 12:30
Chairpersons: Eliane Gomes Alves, Sung Ching Lee, Santiago Botía
X1.36
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EGU24-5862
Florian Hofhansl, Peter Hietz, Werner Huber, Anton Weissenhofer, and Wolfgang Wanek

Tropical vegetation dynamics and ecosystem carbon (C) stocks typically vary with local topography and forest disturbance history. Yet, neither remote sensing nor vegetation modeling captures the underlying mechanistic processes determining ecosystem functioning and therefore the resulting estimates often do not match field observations of vegetation C stocks, especially so in hyperdiverse tropical forest ecosystems. This mismatch is further aggravated by the fact that multiple interacting factors, such as climatic drivers (i.e., temperature, precipitation, climate seasonality), edaphic factors (i.e., soil fertility, topographic diversity) and diversity-related parameters (i.e., species composition and associated plant functional traits) in concert determine ecosystem functioning and therefore affect tropical forest C sink-strength.

Here, we propose a novel framework designed for integrating in-situ observations of local plant species diversity with remotely sensed estimates of plant functional traits, with the goal to deduce parameters for a recently developed trait- and size-structured demographic vegetation model. Plant-FATE (Plant Functional Acclimation and Trait Evolution) captures the acclimation of plastic traits within individual plants in response to the local environment and simulates shifts in species composition through demographic changes between coexisting species, in association with differences in their life-history strategies.

Our framework may be used to project the functional response of tropical forest ecosystems under present and future climate change scenarios and thus should have crucial implications for assisted restoration and management of tropical plant species threatened by extinction.

How to cite: Hofhansl, F., Hietz, P., Huber, W., Weissenhofer, A., and Wanek, W.: Landscape-scale And Spatially Explicit Representation of vegetation dynamics and ecosystem carbon stocks in a hyperdiverse tropical forest ecosystem (LASER), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5862, https://doi.org/10.5194/egusphere-egu24-5862, 2024.

X1.37
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EGU24-10719
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ECS
Nathielly Martins and the AmazonFACE team

The impact of elevated atmospheric CO2 concentrations on forest productivity depends on the capacity of plants to balance the additional CO2 with the demand for additional nutrients. One hypothesis states that plants may allocate the extra carbon belowground in producing and maintaining fine roots to alleviate nutrient limitation. In the Amazon basin, where approximately 60% of the forest is on old and weathered soil, the litter layer is an important nutrient source. In some regions, root mats growing in the litter layer can be observed, where the roots intercept the newly mineralized nutrients before they reach the soil and may bind to the mineral matrix. To improve their nutrient uptake capacity, trees can either modify their root morphology to a ‘do-it-yourself” strategy, increasing root length and branching intensity or alternatively, they can outsource the same function by investing in symbioses with mycorrhizal fungi. Additionally, fine roots can stimulate microbial decomposition of recalcitrant substrates (e.g., wood debris) by exuding low molecular weight organic compounds (LMWO) and increasing P mobilization by phosphatase activity without changing decomposition. These strategies could also vary depending on the growing depth of roots due to the different physical conditions between the organic upper and mineral layers. However, little is known about the role of trait differences in roots under higher CO2 concentrations.

To increase our understanding of belowground responses of understory plants to elevated CO2 concentrations, we set up an Open-Top Chamber experiment in a lowland forest in the Central Amazon. We observed that under eCO2, root productivity did not change in the litter layer but showed a decreased pattern in the soil layer. Moreover, plants intensified root foraging in the litter layer by increasing their specific root length more than threefold under elevated CO2. In contrast, roots in the soil mineral layer followed an “outsourcing” strategy by increasing arbuscular mycorrhizal colonization by 117%. In addition, our results showed a decrease in the organic P in litter without a change in C decomposition under higher CO2 concentrations, suggesting a direct P mobilization.

Our results suggest that plants may plastically adjust resource acquisition strategies to increase nutrient uptake efficiency and be able to directly affect P mobilization from the litter layer. We conclude that this ability of plants to adapt their P acquisition strategies in response to eCO2 by tackling different sources within the litter-soil continuum and maximizing nutrient acquisition represents an important mechanism to support the CO2 fertilization effect and might affect the resilience of the Amazonian rainforest to climate change, and thus global carbon balance.

How to cite: Martins, N. and the AmazonFACE team: Multiple plant root strategies improve phosphorus acquisition under elevated CO2 in the Amazon rainforest, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10719, https://doi.org/10.5194/egusphere-egu24-10719, 2024.

X1.38
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EGU24-10823
Flavia Durgante, Jochen Schöngart, Maria Teresa Fernandez Piedade, Susan Trumbore, Sam P. Jones, Didier Gastmans, Shujiro Komiya, Rafael Oliveira, Gerd Gleixner, Jost Lavric, Heiko Moossen, Heike Geilmann, Bianca Weiss, Maira Macedo, Lorena Maniguage Rincon, Priscila Amaral de Sá, and Florian Wittmann

The Central Amazon comprises mosaics of forest ecosystems with different water dynamics and soil characteristics. The water dynamics from each ecosystem affect the evaporation signal seasonally expressed in the water isotopes (δ18O and δD). The recognition of the evaporative signal from different forest segments is essential for the development of hydrological and eco-hydrological studies in the complex Amazon biome. In this study, we used stable isotopes to evaluate how the water dynamics of different forest ecosystems affect seasonal water evaporative signals in each environment. We monitored water isotope signals from 2018-2020 in different compartments (precipitation, soil, stream, groundwater, river, lake, and flooded areas) of two non-flooded forests (clay soils - “plato” and sandy soils – “campinarana”) and three flooded forests (pristine igapó, disturbed igapó and várzea). We found that the soil water sampled by lysimeters in the upland forest seasonally expresses the isotope signal from the rainwater (Local Meteorical Water Line-LMWL) without a strong evaporative overprint. The water isotope signal from flooded forests is more variable. The isotopic composition of pristine rivers has an overlapping signal from the rain isotope signal (LMWL). However, water from the river downstream from the very large hydropower dam (Balbina) has a strong evaporative signal. During the flooded period, the water within the flooded forests has a more evaporated signal than the signal from the source (such as the river or lakes). During the non-flooded period, the water isotope signal from the soil inside the flooded forest corresponds to the rainwater signal. To the best of our knowledge, these represent the first description of the water isotope signals from the compartments in different Central Amazonian forest ecosystems. They illustrate and identify the high variation of the evaporative signal from the complex Amazon biome, knowledge that is essential to understanding how different forest ecosystems influence water recycling in the Amazon hydrological cycle.

How to cite: Durgante, F., Schöngart, J., Piedade, M. T. F., Trumbore, S., Jones, S. P., Gastmans, D., Komiya, S., Oliveira, R., Gleixner, G., Lavric, J., Moossen, H., Geilmann, H., Weiss, B., Macedo, M., Rincon, L. M., Sá, P. A. D., and Wittmann, F.: Seasonal variation of water isotopes in different forest ecosystems in the Central Amazon , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10823, https://doi.org/10.5194/egusphere-egu24-10823, 2024.

X1.39
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EGU24-11932
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ECS
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Highlight
Selma Bultan, Sebastian Bathiany, Niklas Boers, Raphael Ganzenmueller, Gergana Gyuleva, Yiannis Moustakis, and Julia Pongratz

The Amazon rainforest is of vital importance for biodiversity, regional climate, as well as global water and carbon cycling. However, over the past decades, ecosystem functions of the Amazon rainforest have diminished through a combination of increasing anthropogenic pressure in form of land-use change and intensifying natural disturbances. Recent studies suggest that unabated deforestation and climate change could tip large parts of the Amazon towards a different, savanna-like vegetation state. Although such a scenario could lead to severe impacts on the climate system from regional to global scales, a holistic assessment of the risk of large-scale Amazon forest loss due to land-use change and climate change in the 21st century is currently lacking. 

Here, we use data from multiple CMIP6 Earth System Models under two low climate mitigation scenarios to attribute Amazon forest loss until 2100 to land-use change and climate change, applying a novel ensemble member approach. We find that around 1 mio. km2 of forest will diminish by 2100, corresponding to a loss of around one fifth of the pre-industrial forest area. Historically and over the first half of the 21st century, land-use change is the main driver of forest loss, whereas forest loss due to climate change increases non-linearly beyond 2°C global warming and even exceeds forest loss caused by land-use change by the end of the century in some models. We further find a consistent increase in the probability of abrupt (rather than gradual) forest loss with progressing deforestation and climate change. 

Overall, our results highlight that under plausible low mitigation socio-economic pathways 1) the Amazon rainforest will substantially diminish due to anthropogenic climate and land-use change and 2) the risk of forest loss due to climate change increases significantly beyond 2°C global warming. This stresses the urgent need for increased efforts to reduce deforestation and forest degradation through forest protection, conservation and sustainable land-use practices and for climate mitigation efforts in line with the Paris Agreement.

How to cite: Bultan, S., Bathiany, S., Boers, N., Ganzenmueller, R., Gyuleva, G., Moustakis, Y., and Pongratz, J.: Attributing future Amazon forest loss to land-use change and climate change, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11932, https://doi.org/10.5194/egusphere-egu24-11932, 2024.

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EGU24-13403
Skye Hellenkamp, Paulo Brando, and Bela Starinchak

Land surface temperature (LST) is a dominant influence on the health and productivity of ecosystems. Deforestation in the Brazilian Amazon has led to extensive land-use transitions from forests to pastures and industrialized agriculture. This has resulted in elevated land surface temperatures, with impacts on the energy, water, and carbon cycles. Forest fragmentation increases the area of forest edges, where exposure to sunlight, wind, and bordering land-uses alters the forest microclimate. While the changes in forest edge temperature due to bordering land-use transitions is acknowledged, the magnitude of these changes between specific agricultural land management practices has yet to be determined. This case study uses a remote sensing approach to investigate forest edge temperatures in Mato Grosso, Brazil, with a primary goal of discerning how distinct agricultural practices, such as cover cropping or double cropping, can potentially mitigate adverse temperature impacts on forest edges. These findings will strengthen the understanding of forest edge temperatures, with a focus on the potential of sustainable land management, contributing to broader conservation efforts in the Amazon Rainforest. 

How to cite: Hellenkamp, S., Brando, P., and Starinchak, B.: Understanding the role of temperature in forest edges: a remote sensing approach in the Brazilian Amazon, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13403, https://doi.org/10.5194/egusphere-egu24-13403, 2024.

X1.41
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EGU24-15363
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ECS
Gisela Dajti, David Urquiza, Hella van Asperen, Sam Jones, Shujiro Komiya, Jost Lavric, Stijn Hantson, and Santiago Botía

The Amazon Tall Tower Observatory is located in the central Amazon (S 02 08.9°, W 059 00.2°) inside the Uatumã Sustainable Development Reserve and has been monitoring continuously the atmospheric composition since 2013. The site is set up with two measurement towers of 80 meters and a tall tower of 325 meters for continuous monitoring of trace gases and aerosols. The surface influence (hereafter footprint) of the research station covers a large area to the east and northeast with the fetch extending for hundreds of kilometres, overlapping with the main branch of the Amazon River reaching the city of Belém (during the dry season) and large swaths of primary forest over the Amapá state (during the wet season).  We have analysed trends in fire counts (using MODIS thermal anomalies) and burned area (GFED4 and GFED5, Global Fire Emission Database 4th and 5th version) over the last two decades (2000-2023) inside the ATTO footprint and found that both show increasing and significant trends for the months of June (14,68 fire counts/year) July (42,23 fire counts/year), August (59,6 fire counts/year) and September (148,6 fire counts/year). Spatially, fires are located on easternmost part of the footprint and there is no evidence of a spatial trend approaching ATTO. Interestingly, in October the mean longitude of the fire counts over the period of interest shows a trend migrating from -56°W to -54°W, but with no significant trend in fire counts. We complement these results by analysing mole fractions of carbon monoxide (a proxy for biomass burning) at ATTO for an overlapping period (2013-2023). In addition, we provide links to the environmental drivers explaining these trends and spatial patterns. Observing biogenic greenhouse gases enhances our understanding of the Amazonian rainforest’s carbon budget, influenced by climatic conditions, land use alteration and other anthropogenic impacts.  

How to cite: Dajti, G., Urquiza, D., van Asperen, H., Jones, S., Komiya, S., Lavric, J., Hantson, S., and Botía, S.: Fire trends on ATTO footprint over the last two decades, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15363, https://doi.org/10.5194/egusphere-egu24-15363, 2024.

X1.42
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EGU24-16203
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ECS
Forest resilience after Windthrows in the amazon.
(withdrawn after no-show)
Jose David Urquiza-Munoz, Susan Trumbore, Robinson Negrón-Juárez, Alexander Brenning, Waldemar Alegria-Munoz, Rodil Tello-Espinoza, Richer Rios, and Daniel Magnabosco
X1.43
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EGU24-16499
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ECS
Carolina Monteiro, Anywhere Tsokankunku, Hartwig Harder, and Stefan Wolff

Nitrogen oxides (NOx = NO and NO2) are chemical compounds that affect and control the abundance of ozone (O3) and hydroxyl radicals (OHx = OH and HO2), the main oxidizing agents in the atmosphere. In pristine environments, these oxidizers react with biogenic volatile organic compounds (BVOCs), such as isoprenes, to produce oxidized secondary organic products. Further reaction with NOx leads to the formation of nitrates. Nitrates deposit on surfaces and grow aerosol particles which eventually act as cloud condensation nuclei. This makes NOx an important atmospheric component, even in low concentrations. Therefore, NOx measurements are being made at the Amazon Tall Tower Observatory (ATTO) research site in the central Amazon forest basin, a pristine region.

Here we present the measurements of NO, O3 and meteorological parameters collected at the Walk-up tower, at a height of approximately 40 m, just above the canopy.  

How to cite: Monteiro, C., Tsokankunku, A., Harder, H., and Wolff, S.: NO and O3 mixing ratios above the canopy in the rainforest, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16499, https://doi.org/10.5194/egusphere-egu24-16499, 2024.

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EGU24-18326
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ECS
Joao Paulo Darela-Filho, Anja Rammig, Katrin Fleischer, Tatiana Reichert, Laynara F. Lugli, Carlos A. Quesada, Luis Carlos C. Hurtarte, Mateus D. de Paula, and David M. Lapola

Phosphorus (P) is a key driver of terrestrial productivity. However, the lack of spatial data on various P forms in soils hinders the large-scale application of process-based vegetation models. To address this, we used a model selection approach based on Random Forest regression models to predict different P forms (total, available, organic, inorganic, and occluded P) in the pan-Amazon region. Our models were trained and tested using data from 108 sites of the RAINFOR network, including soil group and textural properties, geolocation, nitrogen (N) and carbon (C) contents, terrain elevation and slope, soil pH, and mean annual precipitation and temperature. The models were then applied to several spatially explicit datasets to predict the target P forms. The resulting maps depict the distribution of total, available, organic, inorganic, and occluded P forms in the topsoil profile (0 - 30 cm) at a spatial resolution of 5 arcminutes. Our models achieved a good level of mean accuracy (77.37 %, 76,86 %, 75.14 %, 68.23 %, and 64.62% for the total, available, organic, inorganic, and occluded P forms, respectively). Our results reveal a clear gradient of soil development and nutrient content, with the mapped area generally exhibiting very low total P concentration status. Total N was the most important variable for predicting all target P forms. Despite some gaps in the training and testing data, most of the area could be mapped with a good level of accuracy. Our maps can aid in the parametrization and evaluation of process-based terrestrial ecosystem models and promote the testing of new hypotheses about P availability and soil-vegetation feedbacks in the pan-Amazon region.

How to cite: Darela-Filho, J. P., Rammig, A., Fleischer, K., Reichert, T., Lugli, L. F., Quesada, C. A., Hurtarte, L. C. C., de Paula, M. D., and Lapola, D. M.: Mapping Phosphorus Forms in the Pan-Amazon Region: A Machine Learning Approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18326, https://doi.org/10.5194/egusphere-egu24-18326, 2024.

X1.45
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EGU24-19990
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ECS
Thomas Sibret, Marc Peaucelle, Felicien Meunier, Marijn Bauters, David Ellsworth, Kristine Crous, Pascal Boeckx, and Hans Verbeeck

The Congo basin is home to the second largest tropical forest in the world Therefore, it plays a crucial role in the global carbon cycle. Yet very few field based data on related processes exist. Gaining knowledge on a species level is also crucial for understanding these ecosystems. Leaf chamber measurements allow to measure photosynthetic capacity on a leaf level and by so, quantify the photosynthetic capacity of individual species. Moreover, they allow to quantify a plant´s reaction to environmental parameters such as light, atmospheric CO2 concentration and temperature. Such data is crucial to improve the calibration and robustness of global vegetation models. These models are key tools to estimate the global carbon budget and ecosystem responses to climate change as a part of the Intergovernmental Panel on Climate Change exercises.

To date, no such data exists for the forests of the Congo Basin which prevents us to properly understand forest dynamics and resilience to global changes.In this research, we quantify leaf level carbon uptake and its response to light, CO2 and Temperature for dominant tree species within the footprint of the CongoFlux tower in Yangambi (DR Congo).

As such, we deliver the first in-field leaf-level photosynthetic parameters dataset for a lowland tropical forest of the Congo Basin. Doing this, we explore the controls of interspecific variation in photosynthetic capacity including plant guild, species and vertical canopy position. Our study takes place at the research site of CongoFlux, Yangambi (DR Congo).

How to cite: Sibret, T., Peaucelle, M., Meunier, F., Bauters, M., Ellsworth, D., Crous, K., Boeckx, P., and Verbeeck, H.: Quantifying the photosynthetic capacity of dominant tree species in a humid lowland tropical forest of the Congo Basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19990, https://doi.org/10.5194/egusphere-egu24-19990, 2024.

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EGU24-12352
Hella van Asperen, Thorsten Warneke, Alessandro Carioca de Araújo, Bruce Forsberg, Sávio José Filgueiras Ferreira, Thomas Röckmann, Carina van der Veen, Sipko Bulthuis, Shujiro Komiya, Sam P Jones, Santiago Botía, Leonardo Ramos de Oliveira, Thiago de Lima Xavier, Jailson da Mata, Marta de Oliveira Sá, Paulo Ricardo Teixeira, Julie Andrews de França e Silva, Justus Notholt, and Susan Trumbore

CO is an indirect greenhouse gas because it reacts with OH, therefore increasing the lifetime of methane: its possible indirect radiative forcing has been estimated as larger than that of N2O. Previous studies have indicated that temperate and boreal forests act as a net sink for CO, but the role of tropical rain forest ecosystems has not been investigated. We present the first CO flux measurements from tropical forest and forest soils, and can show that tropical rain forests are a net source of CO to the atmosphere.

During two intensive field campaigns at tropical rain forest fieldsite ZF2 (Manaus, Brazil), soil CO fluxes were determined by use of flux chambers. In addition, nighttime vertical CO concentration profiles were measured and different micro-meteorological techniques were applied to estimate ecosystem CO fluxes. Furthermore, we performed nocturnal CO concentration measurements in a seasonally inundated valley, which was hypothesized as a potential hotspot for ecosystem CO emissions.

Soil CO fluxes ranged from -0.19 (net soil uptake) to 3.36 (net soil emission) nmol m-2 s-1, averaging ∼1 nmol CO m-2 s-1. Fluxes varied with season and topographic location, with highest fluxes measured in the dry season in a seasonally inundated valley. Nocturnal canopy air profiles show consistent decreases in CO mixing ratios with height, which requires positive surface fluxes between 0.3 and 2.0 nmol CO m-2 s-1. Similar fluxes are derived using a canopy layer budget method, which considered the nocturnal increase in CO over time (1.1 to 2.3 nmol CO m-2 s-1). Using wet season concentration profiles of CO, the estimated valley ecosystem CO production exceeded the measured soil valley CO fluxes, indicating a potential contribution of the valley stream to overall CO emissions.

Based on our field observations, we expect that tropical rain forest ecosystems are a net source of CO. Extrapolating our first observation-based tropical rain forest soil emission estimate of ∼1 nmol m-2 s-1, a global tropical rain forest soil emission of ∼16.0 Tg CO yr-1 is suggested. Total ecosystem CO emissions might surpass this estimate, considering that valley streams and inundated areas could serve as local CO emission hotspots. To further improve tropical forest ecosystem CO emission estimates, more in-situ tropical forest soil and ecosystem CO flux measurements are essential.

How to cite: van Asperen, H., Warneke, T., Carioca de Araújo, A., Forsberg, B., José Filgueiras Ferreira, S., Röckmann, T., van der Veen, C., Bulthuis, S., Komiya, S., P Jones, S., Botía, S., Ramos de Oliveira, L., de Lima Xavier, T., da Mata, J., de Oliveira Sá, M., Ricardo Teixeira, P., Andrews de França e Silva, J., Notholt, J., and Trumbore, S.: Tropical forests: a source of CO!, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12352, https://doi.org/10.5194/egusphere-egu24-12352, 2024.

X1.47
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EGU24-18954
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Highlight
Tomas Domingues, Amanda Damasceno, Sabrina Garcia, Izabela Aleixo, Juliane Menezes, Iokanam Pereira, Martin De Kauwe, Vanessa Ferrer, Katrin Fleischer, Thorsten Grams, Flávia Santana, Iain Hartley, Bart Kruijt, Laynara Lugli, Nathielly Martins, Richard Norby, Bruno Portela, Anja Rammig, Carlos Quesada, and David Lapola and the AmazonFACE team

The response of plants to increasing atmospheric CO2 concentration depends on several factors such as life history of specific species, availability of water, nutrients and light, and the ecological context that the plants are found. Although several experiments with elevated CO2 (eCO2) have been done worldwide, none was performed in the Amazon forest understory focusing in a community growing naturally. The understory of the central Amazon is limited by both light and phosphorus. Understanding how such ecosystem responds to eCO2 is important to foresee how the forest will function in the future. Also, quantifying the response of this forest compartment helps to constrain Ecosystem Models that compute carbon and water fluxes.

For this study, we used the open-top chamber (OTC) approach, with a CO2 enrichment of +250 ppm above the ambient concentration. Eight OTC were installed (4 with ambient CO2 and another 4 with eCO2) in the understory of a natural forest in the Central Amazon, approximately 70 km from Manaus city. The eCO2 experiment started in November 2019 and, after 120 days, we quantified the average community response of the following photosynthetic parameters: light saturated carbon assimilation rate (Asat), stomatal conductance (gs), transpiration rate (E), intrinsic water use efficiency (iWUE), apparent quantum yield (Φ), light compensation point (LCP), maximum carboxylation capacity (Vcmax), maximum electron transport rate (Jmax). After 240 days of treatment, we quantified mean individual leaf production and accumulated leaf production, leaf area (Lfarea). After 300 days, we quantified the increment in base diameter (BD), height (Ht) and relative growth rate (RGR).

Under eCO2, we observed increases in Asat (67%), Jmax (19%), Φ (56%), and iWUE (78%), in agreement with the hypothesis that plants near the light compensation point respond strongly to eCO2. We also detected an increase in Lfarea (51%) and BD (65%), indicating that the extra primary productivity was not allocated to growth in height, but to supporting more light intercepting organs (leaf and conducting tissues). No detectable changes were observed for the other variables.

Apart from the expected increase in assimilation rates, understory plants in Central Amazon responded positively to eCO2 by increasing their ability to capture and use light (leaf size, Φ, and Jmax). The increment in leaf area while maintaining E rates signifies that this forest compartment will increase its contribution to the whole forest water fluxes to the atmosphere. That might be related to the prevailing acquisitive strategy necessary for competing for phosphorus brought by water flow through plants. As a possible consequence, this forest might be less resistant to extreme drought associated with El Niño years.

Funding: Coordination for the Improvement of Higher Education Personnel - CAPES (grants 312589/2022-0) and São Paulo Research Foundation-FAPESP processes numbers (2022/07735-5) and (2015/02537-7). 

How to cite: Domingues, T., Damasceno, A., Garcia, S., Aleixo, I., Menezes, J., Pereira, I., De Kauwe, M., Ferrer, V., Fleischer, K., Grams, T., Santana, F., Hartley, I., Kruijt, B., Lugli, L., Martins, N., Norby, R., Portela, B., Rammig, A., Quesada, C., and Lapola, D. and the AmazonFACE team: Amazonian understory response to elevated CO2, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18954, https://doi.org/10.5194/egusphere-egu24-18954, 2024.

X1.48
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EGU24-7786
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ECS
Rajit Gupta, Kalle Ruokolainen, and Hanna Tuomisto

Deforestation of the Amazon rainforest biome has been of considerable international concern, as extensive forest loss has negative impacts on global carbon storage, hydrological cycles and biodiversity. Ongoing climatic change is predicted to make these effects worse, as climatic models suggest that increasing temperatures will often be accompanied by decreasing precipitation. Such change would put the continued existence of the rainforest biome at risk, as moisture-demanding species would be replaced by more drought-resistant ones. Field observations already indicate that even those Amazonian forests that are not directly affected by deforestation have started to change, and that they grow faster, store less carbon and contain more lianas than before. However, field measurements can only be carried out in a limited number of sites, and these only cover a minute part of the entire Amazon biome. To get a more complete understanding of the changes within the remaining Amazonian forests, we are carrying out broad-scale analyses using Landsat imagery. We first did pixel-based compositing using all image acquisitions within a 10-year time window in order to obtain a clean cloud-free reflectance surface. Two such composites were produced for different time periods (2000-2009 and 2013-2022) in order to identify potential changes across the forested landscape. The results are expected to identify areas where significant but non-obvious changes in the structure and/or function of the forest could be happening, and thereby to facilitate in assessing the degree of threat to the ecosystem

How to cite: Gupta, R., Ruokolainen, K., and Tuomisto, H.: Using Landsat composites to document temporal change within Amazonian forest vegetation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7786, https://doi.org/10.5194/egusphere-egu24-7786, 2024.

Posters virtual: Tue, 16 Apr, 14:00–15:45 | vHall X1

Display time: Tue, 16 Apr, 08:30–Tue, 16 Apr, 18:00
Chairpersons: Flavia Durgante, Tin Satriawan
vX1.5
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EGU24-12275
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ECS
Julyane Santos, Sabrina Garcia, Laynara Lugli Lugli, Izabela Aleixo, Tomas Domingues, Bruno Takeshi, Ana Oliveira, Juliane Menezes, David Lapola, and Carlos Quesada

Nutrient resorption efficiency (RE) occurs before leaf abscission, with nutrients being actively transported via phloem through abscission zones from senescent leaves to be used in other parts of the plant. It is an essential nutrient conservation strategy for tropical plants growing on soils depleted of P (phosphorus) and other rock-derived elements (K; potassium, Ca; calcium, and Mg; magnesium), influencing nutrient cycling in these ecosystems. The environment heavily influences resorption; therefore, a better understanding of nutrient resorption processes in tropical trees, which act as a carbon sink, is important when facing the rapid climatic changes. Thus, our objective was to investigate the resorption of five macro elements (C; carbon, N; nitrogen, P, K, Ca, and Mg) and three micronutrients (Fe; iron, Zn; zinc, and Mn; manganese), and the effects of leaf longevity, foliar nutrient concentration, and canopy position in RE in a lowland forest tree community in Central Amazon. The study was conducted in two experimental plots at the AmazonFACE Program (Free-Air CO2 Enrichment) in Manaus, Amazonas, Brazil. Two 40 m scaffolding towers in the center of the plot granting access to the canopy of the twelve tree species studied. Young, mature, and senesced leaves were collected, totaling 188 leaves, from 2018 to 2019 for nutrient laboratory analysis. We found that K, P, and N were the most resorbed nutrients (42%, 33%, and 7%, respectively), while Zn, Fe, and Ca were the most accumulated (-65%, -27%, and -21%, respectively). Additionally, we found that C, N, P, Fe, and Zn resorption positively correlated with their concentration in leaves. Likewise, P, N, Mg, K, and C resorption positively correlated with leaf longevity. On the other hand, canopy position influenced the resorption of three elements: C, K, and Zn resorption. Our results suggest that P was the scarcest nutrient stored in leaves; the higher resorption efficiencies for K and P than for N suggest higher plant internal nutrient recycling of K and P, likely due to their scarcity in the soil during leaf senescence, species with longer leaf life span are often assumed to have higher nutrient resorption efficiency than species with short leaf life span to reduce nutrient loss, species in the community studied can optimize leaf anatomy and physiology to make the best use of the variable light encountered regarding of its position on the forest vertical profile. These trends suggest that nutrient resorption from senescent leaves may be a general adaptive strategy for conserving nutrients by plants in tropical forests growing on nutrient-poor soils, which should be considered when predicting future scenarios.

How to cite: Santos, J., Garcia, S., Lugli, L. L., Aleixo, I., Domingues, T., Takeshi, B., Oliveira, A., Menezes, J., Lapola, D., and Quesada, C.: Plant nutrient resorption efficiency in a Central Amazon rainforest, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12275, https://doi.org/10.5194/egusphere-egu24-12275, 2024.

vX1.6
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EGU24-20858
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Highlight
Frederick Otu-Larbi, Caleb Mensah, Nana Agyemang Prempeh, Naomi Kumi, and Richard Kyere-Boateng

A new carbon flux tower has been established in the tropical rainforest of Ghana to measure carbon fluxes as well as emissions of biogenic volatile organic compounds. African tropical forests constitute about 20% of Global Tropical Forest cover but have been understudied due to a lack of in-situ observations. The establishment of GhanaFLUX in the Bia-Tano forest reserve in western Ghana will help to fill this gap, allowing in-depth assessments of carbon sequestration and storage in African forests. Here, we present a snapshot of the facilities available at GhanaFLUX, and measurements taken in the first year of operation. We show time series analysis of carbon dioxide and meteorological datasets obtained from GhanaFLUX, highlighting the seasonal variations in these observations. We also share some of our experiences and challenges during the establishment and operation of the flux site to guide researchers who are planning to set up new sites in challenging environments like rainforests. 

How to cite: Otu-Larbi, F., Mensah, C., Agyemang Prempeh, N., Kumi, N., and Kyere-Boateng, R.: GhanaFLUX: Meauring carbon fluxes in an African Rainforest, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20858, https://doi.org/10.5194/egusphere-egu24-20858, 2024.