The perplexing drought response strategy of Eastern oak species, evaluated in the context of their ongoing decline.
Abstract
Oak species were once prolific in Eastern U.S. forests, but their abundance has decreased considerably in recent decades. Multiple factors are likely contributing to their decline, including fire exclusion, "mesophication" of forest microclimates, herbivory, and disease. Regardless of the cause, the continued loss of oaks from Eastern US forests could have significant functional and ecological consequences. Here, we focus specifically on the functional implications of oak loss during periods of hydrologic stress. Oak species have a unique and surprising drought response strategy. By synthesizing leaf- and tree-level observations across multiple sites, we demonstrate that oaks are very anisohydric. This means they allow their leaf water potential to fall rapidly during drought - a strategy which can sustain high rates of carbon uptake and water use, but which incurs a greater risk of xylem failure. Importantly, however, unlike most other anisohydric species, white oaks have xylem that are exceptionally vulnerable to cavitation. This means that the drought response strategy of oaks repeatedly exposes them to the risk of highly damaging hydraulic failure. In this talk, we will evaluate the consequences of this risky drought response strategy for the carbon uptake, water use, and mortality likelihood of oak species. We will also extrapolate these results to understand how the continued loss of oaks from the landscape might affect ecosystem-scale carbon and water cycling in Eastern US forests, now and in the future.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.B21B..02N
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCESDE: 0428 Carbon cycling;
- BIOGEOSCIENCESDE: 0439 Ecosystems;
- structure and dynamics;
- BIOGEOSCIENCESDE: 1630 Impacts of global change;
- GLOBAL CHANGE