科研之友
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摘要
Pion pines (Pinus edulis Engelm.) are a widely distributed species across the western United States (U.S.) providing habitat for wildlife species in addition to forest products for humans. Thus, understanding factors that promote the productivity of this species is important to predict future responses to environmental change. We examined pion pine growth from tree-ring records and evaluated whether growth responses to climate may be explained by local site characteristics such as geologic substrate from the late 1900s through the early 2000s. Cluster analysis revealed two distinct clusters that differed in their growth response (i.e., tree-ring width) to July temperature of the current growing season (cluster 1, r = -0.45; cluster 2, r = -0.31). Clusters 1 and 2 displayed synchronous growth throughout the early to mid-twentieth century but growth patterns diverged in the 1970s. Ring widths in cluster 1, which were most sensitive to average July temperature, showed a downward trend in the 1970s through the 2000s. By contrast, cluster 2 growth showed positive growth responses during the 1980s followed by growth declines during the multi-year drought of the 1990s. There was evidence that these growth patterns may be partially explained by geologic substrate (i.e., shale, sandstone, alluvial fan). Pearson's r values of tree growth over time were strongly negative on shales and sandstones (r = -0.30, P = 0.009; r = -0.34, P = 0.003), whereas those on alluvial fans were not significant (r = 0.13, P = 0.23). Reported values of soil available water capacity on the shale and sandstone substrates are low relative to the alluvial fans, which may partially explain the differential growth responses. Our findings suggest that consideration of increasing summer temperatures on low availability water capacity geologic substrates may be important in predicting future pion pine growth declines.
- 出版日期2015-7
