Assessing the role of tree mortality in shaping ecosystem functional properties

Tree mortality is increasing globally due to climate extremes, disturbances, and biotic stressors, with profound consequences for ecosystem carbon cycling. However, the extent to which spatial patterns and temporal dynamics of tree mortality influence the functioning of ecosystems as a whole remains poorly quantified. 

In this study, we investigate how tree mortality impacts  key ecosystem functional properties, focusing on light-saturated gross primary productivity (GPP_sat) and maximum net ecosystem production (NEP_max). Ecosystem functional properties were derived from long-term, half-hourly eddy covariance measurements across a range of forest ecosystems. Spatially explicit information on forest cover and tree mortality was obtained from satellite-based predictions of the deadtrees.earth initiative, which integrates drone-based observations with Earth observation data to produce multitemporal mortality and forest cover estimates at global  scale.

We assessed whether including tree mortality information in addition to environmental drives improves the explanation and prediction of global and site-level variability in the flux-derived ecosystem functional properties; GPP_sat and NEP_max. Model performance and variable importance patterns were compared between scenarios with and without forest cover and mortality dynamics to quantify the added explanatory power.

This study aims to provide the first systematic assessment of how spatially explicit tree mortality information contributes to ecosystem functional properties derived from eddy covariance data, and to evaluate whether integrating tree mortality observations can improve our understanding of the controls of ecosystem productivity and carbon balance under ongoing climate change.