六盘山地区油松树轮宽度年表与多尺度标准化降水指数的关系

研究利用在六盘山地区采集的油松树轮样芯建立树轮宽度标准年表(STD),分别与不同长度时间单元(月、半月、旬)和多时间尺度的标准化降水指数(SPIn)序列进行相关性分析。油松标准年表与不同长度时间单元SPI的相关结果显示,较小的时间单元会使相关性表达更加精确,而时间单元过小则会因为数据波动性增大而导致相关关系弱化。因此,相较于月和旬,半月是相关性分析更为合适的时间单元长度。油松标准年表与多时间尺度SPI的相关结果显示,SPI多时间尺度的特性有助于揭示油松径向生长对不同时间尺度水分状况的响应特征,且油松在不同生长时期对于不同时间尺度水分状况具有相异的响应机制。在温度较低(0℃)的冬季,短时间内的降水并不利于树木生长,而长时间良好的水分储备会为树木生长季需水提供保障;在生长季前期,长时间良好的水分状况比短期内的降水更有利于树木的生长;在生长季,补给性水分和土壤水分都对树木生长起着至关重要的作用。

Response of tree-ring width chronology of Pinus tabulaeformis to multi-scale standardized precipitation index (SPIn) in the Liupan Mountain Area

This study generated a standard tree-ring width chronology by using Pinus tabulaeformis samples collected in the Liupan Mountain area and calculated the correlativity between standard chronology and SPI series, which covers three time units of different sizes (i.e., monthly, semi-monthly, and 10 day) and eight time scales. The result of correlation analysis between STD and SPI in different time units showed that semi-monthly was more suitable than monthly and 10 day units for correlation analysis because the shorter units lead a more accurate correlation expression, whereas very short units diluted the significant correlations. In addition, the correlation analysis between STD and SPI with multiple time scales showed that the multi-time scale characteristics of SPI revealed different responses of the radial growth of Pinus tabulaeformis to multi-scales water conditions. Trees exhibited response mechanisms to different water conditions in different growth units: 1) under the situation of low temperature, precipitation undermined the trees'' growth in the short term, but promoted it in the long term; 2) in the pre-growing season, water conditions in long term were more beneficial than in the short term; and 3) in the growing season, sufficient precipitation at all time scales was crucial to the radial growth of Pinus tabulaeformis.