title: Effects of thinning on drought vulnerability and climate response in north temperate forest ecosystems.
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.
authors.affiliation: Department of Forest Resources, University of Minnesota, St. Paul, Minnesota 55108, USA. damato@umn.edu
authors.forename: Anthony W
authors.initials: AW
authors.lastname: D'Amato
authors.affiliation: U.S. Geological Survey, Southwest Biological Science Center, Flagstaff, Arizona 86001, USA.
authors.forename: John B
authors.initials: JB
authors.lastname: Bradford
authors.affiliation: Department of Forest Resources, University of Minnesota, St. Paul, Minnesota 55108, USA.
authors.forename: Shawn
authors.initials: S
authors.lastname: Fraver
authors.affiliation: Northern Research Station, USDA Forest Service, Grand Rapids, Minnesota 55744, USA.
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Palik
mesh_terms: D002980:Climate; D055864:Droughts; D017753:Ecosystem; D016468:Forestry; D008910:Minnesota; D028223:Pinus; D011156:Population Density; D013997:Time Factors; D014197:Trees; D014867:Water
chemical_list: D014867:Water