一份报告说，20世纪温度的上升可能在全世界的一种最古老的树的近来空前的生长中起到了作用。Matthew Salzer及其同事说，狐尾松自很可能从1950年开始在其生长线的边缘加速生长。狐尾松在美国西部干燥、风吹的高海拔山坡上能生存数千年。
这组科学家说，尽管在山上高海拔地区的这种松树的年生长受到寒冷温度的限制，在低海拔地区的这种树的生长通常受到水气的限制。这组作者发现在生长线约150米内的这种树从1951年到2000年期间的年轮比此前的3700年更宽。这组作者说，生长率的这种差异可能是把20世纪晚期变暖的温度与高海拔生态系统不寻常的行为联系起来的又一件证据。（生物谷Bioon.com）
推荐专题：聚焦全球变暖 关注你我家园
生物谷推荐原始出处：
PNAS November 16, 2009, doi: 10.1073/pnas.0903029106
Recent unprecedented tree-ring growth in bristlecone pine at the highest elevations and possible causes
Matthew W. Salzera,1, Malcolm K. Hughesa, Andrew G. Bunnb and Kurt F. Kipfmuellerc
aLaboratory of Tree-Ring Research, University of Arizona, Tucson, AZ 85721;
bDepartment of Environmental Sciences, Western Washington University, Bellingham, WA 98225; and
cDepartment of Geography, University of Minnesota, Minneapolis, MN 55455
Great Basin bristlecone pine (Pinus longaeva) at 3 sites in western North America near the upper elevation limit of tree growth showed ring growth in the second half of the 20th century that was greater than during any other 50-year period in the last 3,700 years. The accelerated growth is suggestive of an environmental change unprecedented in millennia. The high growth is not overestimated because of standardization techniques, and it is unlikely that it is a result of a change in tree growth form or that it is predominantly caused by CO2 fertilization. The growth surge has occurred only in a limited elevational band within ≈150 m of upper treeline, regardless of treeline elevation. Both an independent proxy record of temperature and high-elevation meteorological temperature data are positively and significantly correlated with upper-treeline ring width both before and during the high-growth interval. Increasing temperature at high elevations is likely a prominent factor in the modern unprecedented level of growth for Pinus longaeva at these sites.
