2000~2019嘉陵江流域植被覆盖时空变化特征及气候响应分析

Spatio-temporal Variation Characteristics and Climate Response Analysis of Vegetation Coverage in Jialing River Basin from 2000 to 2019

嘉陵江是长江水系流域面积最大的一条支流,近年来嘉陵江流域出现严重水土流失,在生态保护工程的实施和气候变化的共同作用下植被覆盖发生了明显变化,研究植被覆盖时空变化特征、未来趋势和影响因素,可为嘉陵江流域生态环境治理提供参考依据。基于MODIS-NDVI时序数据和地面气象数据,借助3S技术和线性趋势分析、Hurst指数、变异系数等方法多角度分析了嘉陵江流域植被覆盖的时空演变特征及未来趋势,并结合Mann-Kendall(M-K)检验与偏相关系数研究气候因子对植被覆盖的影响。结果表明:(1)近20年来嘉陵江流域植被覆盖总体呈上升趋势,增加速率为2.9%/10a,且空间分布上具有显著差异,表现为上中游偏高,下游偏低;(2)嘉陵江流域植被覆盖呈增加趋势和减少趋势的面积分别占88.68%和11.32%,具体表现为陇南陕南地区及中下游东部地区显著增加,流域西北部与南部各市县城区减少;(3)流域北部地区植被覆盖变化的波动性强于南部地区,中东部地区波动最小。(4)嘉陵江流域植被覆盖变化反向持续性较强,植被变化呈持续退化趋势的主要在碌曲县南部与流域南部各市县城区,呈持续改善趋势的主要在广元市剑阁县与苍溪县,其余区域呈由退化到改善的趋势;(5)气温对嘉陵江流域植被覆盖变化的影响最大,且植被NDVI对气温和降水的响应均存在一定的滞后现象,人类活动对植被覆盖变化的影响具有两面性。

The Jialing River is the largest tributary of the Yangtze River Basin. In recent years,serious soil erosion has occurred in the Jialing River Basin. The vegetation in the Jialing River Basin has had a relatively large variance in spatial and temporal patterns,affected by the implementation of ecological protection projects and changes in climate. Studying the spatial-temporal change of vegetation coverage and its driving factors in the Jialing River Basin can provide reference for the ecological environment management. This study,based on MODIS-NDVI and climate data,aims to analyze the spatial-temporal change of vegetation coverage and its driving factors in the Jialing River Basin between 2000 and 2019 from multiple angles. Linear regression,Hurst index,coefficient of variation and were employed. AND Mann-Kendall test with partial correlation are both used to investigate the spatiotemporal change of vegetation coverage and its relationship with climate change. The results show that:(1) In the past 20 years,the NDVI of the study area are increased,with a linear tendency being 2. 9%/10 a,and there is a significant difference in the spatial distribution,showing that the upper and middle reaches are higher and the lower reaches are lower;(2) The vegetation coverage improved area was larger than the degraded area,being 88. 68% and 11. 32% respectively in the 20 years,The specific manifestation is a significant increase in the southern part of Longnan and southern Shanxi and the eastern part of the middle and lower reaches,and a decrease in the northwest and southern cities,counties and urban areas of the basin;(3) The fluctuation of vegetation coverage in the northern part of the basin is stronger than that in the southern part,and the fluctuation in the central and eastern part is the smallest;(4) The reverse characteristic of vegetation coverage change is significant. In future,the vegetation change showed a continuous degradation trend mainly in southern Luqu County and the southern cities of the basin,and the continuous improvement trend was mainly in Jiange County and Cangxi County of Guangyuan City. The rest of the area showed a trend from degradation to improvement;(5) Temperature has the greatest impact on the change of vegetation coverage in the Jialing River Basin,and there is a time lag effect on the response of vegetation NDVI to temperature and precipitation. The impact of human activities on the change of vegetation coverage is two-sided.