Differential declines in Alaskan boreal forest vitality related to climate and competition. (15th November 2017)

• Record Type: Journal Article
• Authors: Trugman, Anna T.; Medvigy, David; Anderegg, William R. L.; Pacala, Stephen W.
• Is Part Of: Global change biology. Volume 24:Number 3(2018)
• Page Start: 1097
• Page End: 1107
• Publication Date: 2017-11-15
• Subjects: Alaska -- boreal forest -- climate change -- drought -- forest inventory -- growth decline -- insect‐induced mortality -- terrestrial carbon cycle -- vapor pressure deficit; Climatic changes -- Environmental aspects -- Periodicals; Troposphere -- Environmental aspects -- Periodicals; Biodiversity conservation -- Periodicals; Eutrophication -- Periodicals; 551.5
• DOI: 10.1111/gcb.13952
• Languages: English
• ISSNs: 1354-1013

Abstract

Abstract: Rapid warming and changes in water availability at high latitudes alter resource abundance, tree competition, and disturbance regimes. While these changes are expected to disrupt the functioning of boreal forests, their ultimate implications for forest composition are uncertain. In particular, recent site‐level studies of the Alaskan boreal forest have reported both increases and decreases in productivity over the past few decades. Here, we test the idea that variations in Alaskan forest growth and mortality rates are contingent on species composition. Using forest inventory measurements and climate data from plots located throughout interior and south‐central Alaska, we show significant growth and mortality responses associated with competition, midsummer vapor pressure deficit, and increased growing season length. The governing climate and competition processes differed substantially across species. Surprisingly, the most dramatic climate response occurred in the drought tolerant angiosperm species, trembling aspen, and linked high midsummer vapor pressure deficits to decreased growth and increased insect‐related mortality. Given that species composition in the Alaskan and western Canadian boreal forests is projected to shift toward early‐successional angiosperm species due to fire regime, these results underscore the potential for a reduction in boreal productivity stemming from increases in midsummer evaporative demand. Abstract : Rapid warming and changes in water availability at high latitudes alter resource abundance, tree competition, and disturbance, and are expected to disrupt the functioning of boreal forests. Here, we test the idea that variations in Alaskan forest growth and mortality rates are contingent on species composition. We find that the governing climate and competition processes differ substantially across species, and that the most dramatic response occurs in trembling aspen in association with high midsummer vapor pressure deficits. Given projected fire‐driven shifts toward early‐successional angiosperm species, these results underscore potential for reduced boreal productivity stemming from increases in midsummer evaporative demand.