Climatic limits on foliar growth during major droughts in the Southwestern U.S.A.

Journal of Geophysical Research G: Biogeosciences
By: , and 



Pronounced droughts during the 1950s and 2000s in the Southwestern U.S.A. (SW) provide an opportunity to compare mesoscale ecosystem responses to anomalously dry conditions before and during the regional warming that started in the late 1970s. This year-round warming has produced fewer cool season freezes, losses in regional snowpack, an 8-10 day advance in spring onset, and hotter summers, all of which should affect vegetation differently across seasons and elevations. Here, we examine indices that represent climatic limits on foliar growth for both drought periods, and evaluate these indices for areas that experienced tree mortality during the 2000s drought. Relative to the 1950s drought, warmer conditions during the 2000s drought decreased the occurrence of temperatures too low for foliar growth at lower elevations in winter and higher elevations in summer. Higher vapor pressure deficits (VPDs) largely driven by warmer temperatures in the more recent drought were more limiting to foliar growth from spring through summer at lower and middle elevations. At many locations where tree mortality occurred during the 2000s drought, low-temperature constraints on foliar growth were extremely unlimiting, whereas VPD constraints were extremely limiting from early spring through late autumn. Our analysis shows that in physiographically complex regions like the SW, seasonality and elevational gradients are important for understanding vegetative responses to warming. It also suggests that continued warming will increase the degree to which VPD limits foliar growth during future droughts, and expand its reach to higher elevations and other seasons.
Publication type Article
Publication Subtype Journal Article
Title Climatic limits on foliar growth during major droughts in the Southwestern U.S.A.
Series title Journal of Geophysical Research G: Biogeosciences
DOI 10.1029/2012JG001993
Volume 117
Year Published 2012
Language English
Publisher American Geophysical Union
Publisher location Washington, D.C.
Contributing office(s) Branch of Regional Research-Western Region
Description 15 p.; G03031
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Journal of Geophysical Research G: Biogeosciences
Country United States
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