Evidence of widespread topoclimatic limitation for lower treelines of the Intermountain West, United States.

Autor: Urza AK; USDA Forest Service, Rocky Mountain Research Station, 920 Valley Road, Reno, Nevada, 89512, USA.; Program in Ecology, Evolution and Conservation Biology, University of Nevada-Reno, 1664 North Virginia Street, Reno, Nevada, 89557, USA., Weisberg PJ; Program in Ecology, Evolution and Conservation Biology, University of Nevada-Reno, 1664 North Virginia Street, Reno, Nevada, 89557, USA.; Department of Natural Resources and Environmental Science, University of Nevada-Reno, 1664 North Virginia Street, Reno, Nevada, 89557, USA., Dilts T; Department of Natural Resources and Environmental Science, University of Nevada-Reno, 1664 North Virginia Street, Reno, Nevada, 89557, USA.
Jazyk: angličtina
Zdroj: Ecological applications : a publication of the Ecological Society of America [Ecol Appl] 2020 Oct; Vol. 30 (7), pp. e02158. Date of Electronic Publication: 2020 Jun 01.
DOI: 10.1002/eap.2158
Abstrakt: Many forests in dry mountain regions are characterized by a lower elevational treeline. Understanding the controls on the position of lower treeline is important for predicting future forest distributional shifts in response to global environmental change. Lower treelines currently at their climate limit are expected to be more sensitive to changing climate, whereas lower treelines constrained by non-climatic factors are less likely to respond directly to climate change but may be sensitive to other global change agents. In this study, we used existing vegetation classifications to map lower treelines for our 1.7 million km 2 study region in the U. S. Intermountain West. We modeled topoclimatic drivers of lower treeline position for each of three dominant forest types to identify topoclimatically limited treelines. We then used spatial data of edaphic properties, recent fire, and land use to identify lower treelines potentially constrained above their ecophysiological limits by non-climatic processes. We found that the lower treeline ecotone of pinyon-juniper woodlands is largely limited by topoclimate and is likely to be sensitive to increasing temperatures and associated droughts, though these effects may be heterogeneously distributed across the landscape. In contrast, dry mixed-conifer lower treelines in the northern portion of the study area rarely reached their modeled topoclimatic limit, suggesting that non-climatic processes, including fire and land use, constrain the lower treeline above its ecophysiological limits in this forest type. Our results suggest that much of the lower treeline in the Intermountain West is currently climate limited and will thus be sensitive to ongoing climate changes. Lower treelines in other arid or semi-arid mountainous regions around the globe may also be strongly sensitive to climate, though treeline response to climate change will be mediated at the local scale by soil properties, biotic interactions, and natural or anthropogenic disturbances. Our regional study of lower treeline provides a framework for identifying the drivers of lower treeline formation and allows for more robust projections of future treeline dynamics, which are needed to anticipate shifting global distributions of the forest biome.
(© 2020 by the Ecological Society of America.)
Databáze: MEDLINE
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