CEROBI · Constraining forEst Responses to drOughts with carBon Isotopes

Constraining forEst Responses to drOughts with carBon Isotopes

The project, CEROBI: Constraining forEst Responses to droughts with carBon Isotopes, aims to address the need for reliable climate projections amidst the escalating crisis of drought-induced tree mortality in the mid-latitudes. Overall Objectives The core problem addressed by CEROBI is rooted in climate change, which is driving droughts to become more frequent and intense, thereby threatening the ability of forests to function as vital carbon sinks and producewood, fiber and biomass . Currently, Earth System Models (ESMs)—the most advanced tools for predicting future climate—rely on Land Surface Models (LSMs) that are demonstrably biased as they underestimate the severity of drought impacts on ecosystems. Context and Core Problem The scientific challenge lies in describing and parameterizing the complex physiological responses of trees to drought, which often leads to mortality through dual pathways: carbon starvation and hydraulic failure. The ORCHIDEE Land Surface Model (LSM) is particularly advanced in this regard: (1) . trees are categorized in different diameter classes to better capture effects related to tree demography and the long-term, delayed impacts of drought ("drought legacy effect») ;(2) Plant water stress calculations are based on the formalism of the hydraulic architecture. This allows the model to compute water availability by considering resistance along the water transport path (roots, sapwood, leaves), which is crucial for simulating hydraulic failure; and (3) Recent developments focused on refining the model's representation of the dynamics of non-structural carbohydrate (NSC) pools, to better simulate the coupled effects of hydraulic failure and carbon starvation. Despite these advanced mechanistic process representations, the model’s large-scale output still comes with substantial uncertainty. This is because LSMs have over 200 internal parameters many of which are poorly constrained. This results in the insidious problem of equifinality: multiple parameter sets can match current observations but produce widely divergent and unreliable predictions for the future. The CEROBI project is designed to reduce the issue of parameter uncertainty. By introducing carbon isotopes which is a tracer of plant water-use efficiency, the project will circumvent the equifinality problem. This allows the model to reduce the uncertainty of future projections not by redesigning the existing processes (like the hydraulic architecture), but by rigorously calibrating the internal parameters that govern them. Pathway to Impact The ultimate pathway to impact involves using the newly constrained model to perform long-term global simulations under various climate scenarios, finally enabling the identification of regions that are currently well watered but will in the future experience frequent droughts. Such regions should be prioritized for adaptation measures.

Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз