We are very pleased to welcome Nate McDowell (Pacific Northwest National Laboratory, USA) as our guest speaker. McDowell is a renowned expert in the field of tree mortality, particularly under climatically induced drought stress, and focuses on the underlying physiological mechanisms and their impact on global carbon and forest dynamics. His research ranges from models of vegetation mortality in the USA to global forest developments.
Abstract
Global ecosystems are increasingly crossing critical transitions (CTs) in their structure and function and, in parallel, are exhibiting decreasing resilience. The mechanisms underlying decreasing resilience and it’s potential association with CTs are largely unexplored, limiting our predictions of these abrupt transitions and possibly promoting underestimates of future atmospheric CO2. We examine and develop hypotheses to explain decreasing resilience and links to CTs. Climate variability exhibits a weak impact on resilience in tropical forests and none in temperate and boreal forests. Theory, observations, experiments, and process modeling support the emergent hypothesis that decreasing resilience results in part from structural overshoot (SO), wherein anomalous canopy growth from CO2-fertilization causes anomalously high water use that is unsustainable during droughts, leading to severe hydraulic impacts. Decreasing resilience is associated with SO (canopy-greenness) across biomes. Resilience has increased, remained stable, and decreased in the boreal, temperate, and tropical regions since 2005. In contrast, canopy GPP exhibited large resilience declines across all biomes, whereas wood growth did not exhibit shifts in resilience or SO. There is a high likelihood of globally decreasing resilience and increasing CTs with rising CO2 and vapor pressure deficit, the latter exacerbating hydraulic constraints.
Die Veranstaltung findet auf Englisch und in hybrider Form statt. Für alle, die online teilnehmen möchten, steht folgender Link zur Verfügung: https://jki.webex.com/jki/j.php?MTID=m33a1c066bf83bc2bc117a82a4ef1865d
