太白山地区7月NDVI多尺度周期变化及其对气候因子的响应

Multi-scale periodic variation of NDVI in July and its response to climatic factors in the Taibai Mountain area

多尺度周期变化是植被研究的重要前沿问题之一,对揭示植被系统变化规律及其复杂性具有重要意义.本文基于太白山地区树轮宽度年表重建的近172年的7月NDVI资料数据,采用集合经验模态分解法(EEMD)对其在不同时间尺度上的变化特征及其对气候因子的响应进行了分析,结果表明:①太白山地区南北坡7月NDVI呈微弱的非线性上升趋势,北坡/南坡NDVI分别具有3.3 a/3.5 a、8.1 a/8.8 a的年际尺度周期,以及18 a/19.1 a、36a/34.4 a和64.8 a/68.8 a的年代际尺度周期.②重构的年际尺度变化较好地呈现了NDVI原始序列的波动细节,而年代际尺度变化则揭示了不同时期内NDVI的增减交替变化.北坡NDVI的年际尺度波动较大,而南坡NDVI的年代际尺度波动略强.③在年际尺度上影响NDVI的主要因素是降水,年代际尺度上影响NDVI的主要因素是气温.④北坡NDVI变化主要受水分因素控制,而南坡NDVI则受热量因素影响更为明显.分析太白山地区NDVI的多尺度变化及其影响因素对研究太白山地区植被生长的变化特征具有重要意义.

Multi-scale periodic variation is one of the important frontier issues of vegetation research.It is of great significance to revealing the pattern and complexity of vegetation system changes.Based on the NDVI in July data of recent 172 years reconstructed by using the tree-ring width chronology of the Taibai Mountain area,ensemble empirical mode decomposition(EEMD)was used in this study to analyze the response of NDVI to climatic factors and to analyze the variation characteristics of NDVI’s time series at different temporal scales.The results indicates that the NDVI in July showed a weak nonlinear upward trend for the north and south slopes of the Taibai Mountain area.The NDVI on the north slope/south slope showed interannual scale periods of 3.3 a/3.5 a,8.1 a/8.8 a,and interdecadal scale periods of 18 a/19.1 a,36 a/34.4 a,and 64.8 a/68.8 a,respectively.The interannual scale changes reveal the details of the fluctuations of the original sequence of NDVI,while the interdecadal scale changes reveal the alternation of increase and decrease in different periods.The interannual scale of NDVI on the north slope fluctuated greatly,while the interdecadal scale of NDVI on the south slope fluctuated strongly.The main factor affecting NDVI on the interannual scale is precipitation,while the main factor affecting NDVI on the interannual scale is temperature.The NDVI on the north slope is controlled by hydrolic factors and the NDVI on the south slope is more affected by heat factors.The analysis of the multi-scale period of NDVI is of great significance for studying the variation characteristics of vegetation growth in the Taibai Mountain area.