| 摘 要： |
As climate changes, understanding tree responses to climate is important to predict tree growth, and plant competition as a nonnegligible biotic factor plays a key role in such responses. However, few studies have investigated how competition affects the response of Pinus tabulaeformis plantations to climate. In our study, we investigated nine 29-year-old P. tabulaeformis plantation plots (three density gradients: 1208 N/ha, 2275 N/ha, 2989 N/ha). The dendroecological method was used to analyze the impact of competition on tree responses to drought and interannual climate variation. The stand density index was used to indicate the intensity of competition. The results showed that competition modified the climate-growth relationship. Competition increased tree sensitivity to drought but the relationship between competition and sensitivity to drought was nonlinear, which suggested that the competition effect slightly increased under intense competition conditions. Additionally, competition reduced trees growth sensitivity to interannual climate variation. After 1999, the effect of competition was obvious. The sensitivity of small-diameter trees, especially those in middle- and high-density stands, declined. Thus, in future, these trees presumably may exhibit a reduced sensitivity to interannual climate variation and a greater sensitivity to drought. |
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