Response of tree-line populations of foxtail pine (Pinus balfouriana) to climate variation over the last 1000 years
1997
Lloyd, A.H.
Stand density, recruitment rate, and mortality rate in tree-line forests of foxtail pine (Pinus balfouriana Grev. &: Balf) were reconstructed for the last 1000 years. Mortality and recruitment were uncorrelated over the 1000-year period of the reconstruction. At the majority of sites, variance in recruitment was not significantly greater than variance in mortality. Recruitment and stand density were significantly and inversely correlated with summer temperature during the last 1000 years. Mortality rates were uncorrelated with climate. The inverse correlation between recruitment and climate suggests that water balance may mediate the effects of temperature on tree-line forests, a hypothesis that is supported by a significant positive correlation between seedling establishment and winter snowpack during the last 50 years. Despite large changes in the elevation of tree line at these sites during the time period of the reconstruction, populations near tree line were largely unaffected by climate variation, suggesting that steep gradients in vulnerability to climate change may exist at tree line in the Sierra Nevada.
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