Using a water-use framework to explain species-specific radial growth drought response in Eastern U.S. hardwood forests

Authors: Justin Maxwell*, Indiana University, Neil Pederson, Harvard Forest, Tsun Fung Au, Indiana University, Benjamin Lockwood, Indiana University, Grant Harley, University of Idaho, Rich Phillips, Indiana University, Kimberly Novick, Indiana University
Topics: Biogeography, Paleoenvironmental Change, Climatology and Meteorology
Keywords: Tree-rings, eastern deciduous forests, SPEI, drought
Session Type: Paper
Day: 4/6/2019
Start / End Time: 5:00 PM / 6:40 PM
Room: Marshall East, Marriott, Mezzanine Level
Presentation File: No File Uploaded

While ongoing climate change affects a number of meteorological drivers relevant to plant functioning, an increase in the frequency and severity of drought events may ultimately have the largest impact on ecosystem carbon cycling. Much of what we know about tree response to drought comes from the relatively dry western U.S., where droughts are prolonged and often lead to tree mortality. Less attention has been focused on the humid eastern US, where drought-induced mortality is rarer but drought-related declines in carbon uptake and growth are nonetheless profound. Using a well replicated network of tree rings, we determine if a water use strategy (isohydric/anisohydric) explains species-specific response to drought. We find mixed results showing that some species that are extremely isohydric (e.g. L. tulipifera) are very responsive to drought. However, extremely anisohydric species such as oaks are also sensitive to extreme drought. We find the isohydric/anisohydric framework better explains species-specific responses to mild droughts or dry conditions. Our findings suggest that during extreme drought conditions all species will respond by reducing radial growth. However, during times of mild drought, species that have shallow rooting depth that exhibit an isohydric behavior of water-use will respond with growth reduction while anisohydric behaving species with deeper roots do not reduce growth. Thus, understanding the mechanistic determinants of different water-use strategies advances our understanding of how changing eastern forest demographics interact with and respond to drought, allowing a better understanding of how eastern forest may respond to future climate.

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