三江源草地GNDVI年际波动及其沿海拔梯度敏感性分析

Interannual Variability of GNDVI and It's Relationship with Altitudinal in the Three-River Headwater Region

掌握三江源草地植被变化对草地恢复和生态建设工程具有重要的指导意义。以三江源草地生长季平均NDVI(GNDVI)为研究对象,基于趋势分析和偏相关分析方法,分析了三江源区2000—2015年高寒草地生长季GNDVI年际波动及其对海拔变化的敏感性,旨在阐明三江源高寒草地年际波动及其在不同水热组合环境下的响应规律。研究结果表明:自2000年以来,三江源地区暖湿化和各类生态工程的实施使得三江源区高寒草地GNDVI表现出上升的趋势,由于气候、植被生理生态过程等因素的影响,三江源区高寒草地GNDVI存在较大的年际波动,其中草甸区的年际波动对三江源全区草地GNDVI年际波动贡献度达75.4%,草原区仅有24.6%;三江源草地GNDVI多年均值随海拔的升高而降低,而GNDVI的变化趋势随海拔的升高而升高。低海拔地区的草地占比虽小,但其GNDVI的年际波动对三江源全区高寒草地年际波动的贡献度远大于高海拔地区;无论三江源全区、草甸区还是草原区,低海拔地区GNDVI的年际波动受降雨主导,而温度的变化是高海拔地区GNDVI年际波动的主导因子。

Mastering the change of grassland vegetation in Three-River Headwater Region has important guiding significance for grassland restoration and ecological construction project.This study analyzed the linear trend and inter-annual variation of GNDVI with altitudinal gradient in the Three-River Headwater(TRH)Region from 2000 to 2015,the purpose of which is to clarify the interannual fluctuation of alpine grassland in TRH Region and its responses to different hydrothermal combination.The GNDVI showed an increasing trend with large inter-annual variation(IAV)due to climate factors and biological processes of vegetation.The meadow determined the IAV of TRH GNDVI rather than the steppe,and the relative contribution of meadow and steppe to the IAV of TRH GNDVI was 75.4%and 24.6%,respectively.The annual mean value of GNDVI in TRH Region decreased with elevation,while the trend of GNDVI increased with elevation.Different elevations in the TRH region,meadow area and steppe area had differential relative contributions to the IAV of GNDVI,The relative contribution of GNDVI inter-annual variations in the low-altitudinal area was much greater than that in the high-altitudinal area.The IAV of GNDVI in low-altitude areas was dominated by precipitation,while that in high-altitude areas was dominated by temperature in the TRH region.