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The University of Massachusetts Amherst

Effects of thinning on drought vulnerability and climate response in north temperate forest ecosystems

Authors:

Anthony D'Amato

John Bradford

Shawn Fraver

Brian Palik

Publication Type:
Journal Article
Year of Publication:
2013
Secondary Title:
Ecological Applications
ISSN:
1051-0761
DOI:
10.1890/13-0677.1
Pages:
1735-1742
Volume:
23
Year:
2013
Date:
12/2013
URL:
http://www.esajournals.org/doi/abs/10.1890/13-0677.1

Abstract

Reducing tree densities through silvicultural thinning has been widely advocated as a strategy for enhancing resistance and resilience to drought, yet few empirical evaluations of this approach exist. We examined detailed dendrochronological data from a long-term (>50 years) replicated thinning experiment to determine if density reductions conferred greater resistance and/or resilience to droughts, assessed by the magnitude of stand-level growth reductions. Our results suggest that thinning generally enhanced drought resistance and resilience; however, this relationship showed a pronounced reversal over time in stands maintained at lower tree densities. Specifically, lower-density stands exhibited greater resistance and resilience at younger ages (49 years), yet exhibited lower resistance and resilience at older ages (76 years), relative to higher-density stands. We attribute this reversal to significantly greater tree sizes attained within the lower-density stands through stand development, which in turn increased tree-level water demand during the later droughts. Results from response–function analyses indicate that thinning altered growth–climate relationships, such that higher-density stands were more sensitive to growing-season precipitation relative to lower-density stands. These results confirm the potential of density management to moderate drought impacts on growth, and they highlight the importance of accounting for stand structure when predicting climate-change impacts to forests.