Periodic Reporting for period 1 - LEAF-2-TBM (From LEAF to Terrestrial Biosphere Model: Integrating multi-scale observations of highly diverse tropical ecosystems for global scale simulations)
Période du rapport: 2020-06-01 au 2022-05-31
The representation of terrestrial ecosystems is a key source of uncertainty in future projections of the coupled carbon cycle/ climatic system. Current Terrestrial Biosphere Models (TBMs) represent the worldwide vegetation by a dozen of rigid Plant Functional Types (PFT), with empirical mechanisms calibrated on discrete observations. As a result, TBMs represent highly diverse ecosystems such as tropical forests with only one clone of the same plant. This over-simplified representation arises from the lack of observations in some regions such as over Africa, which leads to widely diverging results for C cycling and nutrient/water limitations under future scenarios. Simulating plant diversity is crucial for assessing global change impact on ecosystems and their feedback on climate.
LEAF2TBM targets the unresolved challenge for TBMs to simulate the effects of plant diversity on tropical forest ecosystem functioning and associated global biogeochemical cycles based on an integrated assessment of processes across different scales. This will be achieve by collecting unique concomitant field observations of carbon dioxide and water vapor exchanges measured at multiple scales (from individuals to ecosystem) and state-of-the-art modelling approaches to:
1) accurately quantify the effect of the functional diversity on ecosystems fluxes for two forests located in the Congo Basin and Amazon;
2) disentangle the roles of species composition and environment on ecosystems fluxes;
3) and provide a robust estimate of the global C budget uncertainty for tropical forests in TBMs.
The main objective of LEAF2TBM is to clearly define the effect of local functional diversity on ecosystem carbon and water fluxes in order to improve the robustness of TBMs based on ecological theories that link plant traits, local environment and ecosystem functioning.
LEAF2TBM targets the unresolved challenge for TBMs to simulate the effects of plant diversity on tropical forest ecosystem functioning and associated global biogeochemical cycles based on an integrated assessment of processes across different scales. This will be achieve by collecting unique concomitant field observations of carbon dioxide and water vapor exchanges measured at multiple scales (from individuals to ecosystem) and state-of-the-art modelling approaches to:
1) accurately quantify the effect of the functional diversity on ecosystems fluxes for two forests located in the Congo Basin and Amazon;
2) disentangle the roles of species composition and environment on ecosystems fluxes;
3) and provide a robust estimate of the global C budget uncertainty for tropical forests in TBMs.
The main objective of LEAF2TBM is to clearly define the effect of local functional diversity on ecosystem carbon and water fluxes in order to improve the robustness of TBMs based on ecological theories that link plant traits, local environment and ecosystem functioning.
In June and October 2021, two 1-month campaigns were organized at Yangambi in DR. Congo to select and instrumentalize 25 permanent trees with climbing ropes, dendrometers and sapflow sensors, to train local climbers, technicians and students and to perform leaf traits and leaf gas exchange measurements. This resulted in the first dataset with concomitant observations of plant traits (e.g. nutrients, structure), leaf gas exchange measurements (e.g. photosynthesis, transpiration), tree growth (e.g. dendrometers), sapflow and ecosystem level exchanges of carbon and water (e.g. flux tower) for two seasons (dry/wet) in a tropical rainforest in Africa. During the second campaign we also quantified the temperature response of photosynthesis for 5 dominants species representative of the different strategies (e.g. light tolerant, etc.) at site. We identified clear differences in the temperature response of species, suggesting potential shifts in forest composition with climate warming.
We evaluated the performances of current state-of-the art Terrestrial Biosphere Models in reproducing carbon stocks and fluxes of pantropical forests. None of the models are able to capture the spatial and temporal variability of carbon stocks. This work led a to clear review of the known sources of heterogeneity in tropical forests and what are the priorities to improve TBMs.
Current results are in preparation for publication and dissemination, and have only been disseminated so far between partner institutes.
Most analyses, model developments and simulations based on fieldwork data (delayed by COVID19) are still ongoing.
We evaluated the performances of current state-of-the art Terrestrial Biosphere Models in reproducing carbon stocks and fluxes of pantropical forests. None of the models are able to capture the spatial and temporal variability of carbon stocks. This work led a to clear review of the known sources of heterogeneity in tropical forests and what are the priorities to improve TBMs.
Current results are in preparation for publication and dissemination, and have only been disseminated so far between partner institutes.
Most analyses, model developments and simulations based on fieldwork data (delayed by COVID19) are still ongoing.
To date, LEAF2TBM generated the first and unique concomitant observations of plant traits, photosynthetic capacity, tree growth and fluxes of carbon and water for an African rainforest in DR. COngo. In addition to the improved knowledge gained on African rainforests, LEAF2TBM was a unique opportunity to involve the local population of Yangambi by training technicians and students and to promote science in DR. Congo. Field work in close collaboration with the local universities, the population and involving multiple villagers was a real vector of communication about science and climate change to rise awareness about the central role of the African forest both at the local and global scale.
Even if delayed, once completed, this project will provide a robust assessment on the role of forest diversity on carbon and water fluxes of tropical rainforest, better calibration of Terrestrial Biosphere Models as well as reduced uncertainties on the global carbon budget through a better representation of tropical forest heterogeneity in TBMs.
Even if delayed, once completed, this project will provide a robust assessment on the role of forest diversity on carbon and water fluxes of tropical rainforest, better calibration of Terrestrial Biosphere Models as well as reduced uncertainties on the global carbon budget through a better representation of tropical forest heterogeneity in TBMs.