van Mantgem Phillip J, Stephenson Nathan L
U.S. Geological Survey, Western Ecological Research Center, Sequoia and Kings Canyon Field Station, 47050 Generals Highway #4, Three Rivers, CA 93271, USA.
Ecol Lett. 2007 Oct;10(10):909-16. doi: 10.1111/j.1461-0248.2007.01080.x.
We provide a first detailed analysis of long-term, annual-resolution demographic trends in a temperate forest. After tracking the fates of 21,338 trees in a network of old-growth forest plots in the Sierra Nevada of California, we found that mortality rate, but not the recruitment rate, increased significantly over the 22 years of measurement (1983-2004). Mortality rates increased in both of two dominant taxonomic groups (Abies and Pinus) and in different forest types (different elevational zones). The increase in overall mortality rate resulted from an increase in tree deaths attributed to stress and biotic causes, and coincided with a temperature-driven increase in an index of drought. Our findings suggest that these forests (and by implication, other water-limited forests) may be sensitive to temperature-driven drought stress, and may be poised for die-back if future climates continue to feature rising temperatures without compensating increases in precipitation.
我们首次对温带森林长期、年度分辨率的人口统计学趋势进行了详细分析。在追踪了加利福尼亚内华达山脉老龄林地块网络中21338棵树木的命运后，我们发现，在22年的测量期（1983 - 2004年）内，死亡率显著上升，而补充率未显著变化。两个主要分类群（冷杉属和松属）以及不同森林类型（不同海拔区域）的死亡率均有所上升。总体死亡率的增加是由于由压力和生物因素导致的树木死亡增加，并且与温度驱动的干旱指数增加同时出现。我们的研究结果表明，这些森林（以及由此推断的其他水分受限森林）可能对温度驱动的干旱胁迫敏感，如果未来气候继续呈现气温上升而降水没有相应增加的特征，可能会面临衰退。
