Montane forest productivity across a semiarid climatic gradient.

Autor: Knowles JF; Southwest Watershed Research Center, USDA Agricultural Research Service, Tucson, AZ, USA.; School of Geography, Development & Environment, University of Arizona, Tucson, AZ, USA., Scott RL; Southwest Watershed Research Center, USDA Agricultural Research Service, Tucson, AZ, USA., Biederman JA; Southwest Watershed Research Center, USDA Agricultural Research Service, Tucson, AZ, USA., Blanken PD; Department of Geography, University of Colorado Boulder, Boulder, CO, USA., Burns SP; Department of Geography, University of Colorado Boulder, Boulder, CO, USA.; National Center for Atmospheric Research, Boulder, CO, USA., Dore S; School of Forestry, Northern Arizona University, Flagstaff, AZ, USA., Kolb TE; School of Forestry, Northern Arizona University, Flagstaff, AZ, USA., Litvak ME; Department of Biology, University of New Mexico, Albuquerque, NM, USA., Barron-Gafford GA; School of Geography, Development & Environment, University of Arizona, Tucson, AZ, USA.
Jazyk: angličtina
Zdroj: Global change biology [Glob Chang Biol] 2020 Dec; Vol. 26 (12), pp. 6945-6958. Date of Electronic Publication: 2020 Oct 01.
DOI: 10.1111/gcb.15335
Abstrakt: High-elevation montane forests are disproportionately important to carbon sequestration in semiarid climates where low elevations are dry and characterized by low carbon density ecosystems. However, these ecosystems are increasingly threatened by climate change with seasonal implications for photosynthesis and forest growth. As a result, we leveraged eddy covariance data from six evergreen conifer forest sites in the semiarid western United States to extrapolate the status of carbon sequestration within a framework of projected warming and drying. At colder locations, the seasonal evolution of gross primary productivity (GPP) was characterized by a single broad maximum during the summer that corresponded to snow melt-derived moisture and a transition from winter dormancy to spring activity. Conversely, winter dormancy was transient at warmer locations, and GPP was responsive to both winter and summer precipitation such that two distinct GPP maxima were separated by a period of foresummer drought. This resulted in a predictable sequence of primary limiting factors to GPP beginning with air temperature in winter and proceeding to moisture and leaf area during the summer. Due to counteracting winter (positive) and summer (negative) GPP responses to warming, leaf area index and moisture availability were the best predictors of annual GPP differences across sites. Overall, mean annual GPP was greatest at the warmest site due to persistent vegetation photosynthetic activity throughout the winter. These results indicate that the trajectory of this region's carbon sequestration will be sensitive to reduced or delayed summer precipitation, especially if coupled to snow drought and earlier soil moisture recession, but summer precipitation changes remain highly uncertain. Given the demonstrated potential for seasonally offsetting responses to warming, we project that decadal semiarid montane forest carbon sequestration will remain relatively stable in the absence of severe disturbance.
(© 2020 John Wiley & Sons Ltd. This article has been contributed to by US Government employees and their work is in the public domain in the USA.)
Databáze: MEDLINE
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