Consistent growth of black cottonwoods despite temperature variation across elevational ecoregions in the Rocky Mountains
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- 作者：Kevan J. Berg ; Glenda M. Samuelson ; Chad R. Willms ; David W. Pearce and Stewart B. Rood
- 关键词：Climate change ; Elevation ; Growth ; Poplars ; Temperature
- 刊名：Trees - Structure and Function
- 出版年：2007
- 出版时间：March, 2007
- 年：2007
- 卷：21
- 期：2
- 页码：161-169
- 全文大小：417 KB
- 刊物类别：Biomedical and Life Sciences
- 刊物主题：Life Sciences
Forestry
Plant Sciences
Agriculture
Plant Anatomy and Development
Plant Pathology
Plant Physiology - 出版者：Springer Berlin / Heidelberg
- ISSN：1432-2285
文摘
Globally, water and temperature provide the dominant environmental determinants of tree distribution and growth. In riparian or streamside zones, groundwater is abundant, and we consequently predicted that temperature would limit the growth of riparian cottonwoods in a cool climate northern mountain region. To investigate this association, we analyzed tree rings of 167 black cottonwoods, Populus trichocarpa, along two adjacent Rocky Mountain creeks in Alberta. Cottonwoods were sampled from 1700 m, near their upper elevational limit, down 500 m through three progressively warmer ecoregions, the montane, aspen parkland, and fescue prairie. Across these zones, June through September mean temperatures rose from 12.4 to 16.2°C (lapse rate = 0.67°C/100 m), and there was subsequently a 42% increase in growing degree days (base 5°C, GDD5) from 900 GDD5 at the trees’ upper limit. Despite this variation, growth rate of most trees was fairly consistent across the ecoregions; trunk diameter versus age associations were relatively similar (r 2 = 0.85) with an estimated 14% increase in trunk sizes of 50 year-old trees with decreasing elevation. In all ecoregions, developmental patterns were prominent as annual radial increments increased up to about 20 years, and then progressively declined to an apparent lethal threshold of about 0.4 mm/year at about 100 years. Basal area increments also increased through the juvenile phase, but remained fairly constant thereafter. The weak association between growth and temperature suggests that other environmental factors limited growth rates or there were differences in temperature adaptation across these elevational ecoregions. The results suggest that predicted regional climate warming may not substantially promote the growth rates of these Rocky Mountain trees.