Publication Date:
2016-05-05
Description:
Increasing temperatures have resulted in reduced growth and increased tree mortality across large areas of western North American forests. Here we use tree-ring isotope chronologies (δ 13 C & δ 18 O) from live and dead trees from four locations in south-central Alaska to test whether white spruce trees killed by recent spruce beetle ( Dendroctonus rufipennis Kirby) outbreaks showed evidence of drought stress prior to death. Trees that were killed were more sensitive to spring/summer temperature and/or precipitation than trees that survived. At two of our sites we found greater correlations between the δ 13 C and δ 18 O chronologies and spring/summer temperatures in dead trees than in live trees, suggesting that trees that are more sensitive to temperature-induced drought stress are more likely to be killed. At one site, the difference between δ 13 C in live and dead trees was related to winter/spring precipitation, with dead trees showing stronger correlations between δ 13 C and precipitation, again suggesting increased water stress in dead trees. At all sites where δ 18 O was measured, δ 18 O chronologies showed the greatest difference in climate response between live and dead groups, with δ 18 O in live trees correlating more strongly with late winter precipitation than dead trees. Our results indicate that sites where trees are already sensitive to warm or dry early growing-season conditions experienced the most beetle-kill, which has important implications for forecasting future mortality events in Alaska. This article is protected by copyright. All rights reserved.
Print ISSN:
1051-0761
Electronic ISSN:
1939-5582
Topics:
Biology
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