1998—2020年若尔盖地区植被NDVI变化特征及驱动因子分析

Analysis of driving factors and variation characteristics of vegetation NDVI in Zoige region from 1998 to 2020

【目的】植被是陆地碳汇的主体,利用归一化植被指数(Normalized difference vegetation index,NDVI)分析时空变化特征与驱动因子的关系在区域生态稳定研究中具有重要意义。【方法】基于若尔盖地区植被NDVI、气候、土壤、植被类型和地形数据,运用一元线性回归分析、变异系数和地理探测器方法,分析了1998—2020年若尔盖地区植被NDVI时空变化特征及其驱动因子。【结果】结果表明:(1)1998—2020年若尔盖地区植被总体呈波动上升趋势,多年平均植被NDVI为0.79,年均增速为0.004 3,植被改善趋势明显;空间分布整体呈东南高西北低的格局,多年平均植被NDVI在0.7以上的区域面积比例为96%。(2)1998—2020年若尔盖地区植被NDVI年际变化率较低,平均值为0.001 0,表现为稳定区域的面积比例为99.5%;23年平均变异系数为16.50%,植被状态总体较平稳,变异系数低于20%的面积比例为85%。(3)海拔和气温是若尔盖地区植被NDVI变化的主导自然地理因子,坡度和坡向对植被NDVI影响较小;各自然地理因子之间对植被NDVI的相互作用主要为双因子增强(11.11%)和非线性增强(88.89%)。【结论】若尔盖地区植被在近23年来整体得到了改善,其植被保护和恢复的措施及模式选择应充分考虑海拔、气温等自然地理因子的影响。

Objectives Vegetation is the main body of terrestrial carbon sink.The relationship between the temporal and spatial variation characteristics of Normalized Difference Vegetation Index(NDVI)and the driving factors are of great significance in the research of regional ecological stability.Methods Based on the datasets of vegetation NDVI,climate,soil,vegetation type,and topographic,the driving factors and temporal and spatial variation characteristics of vegetation NDVI in Zoige region from 1998 to 2020 were analyzed by using linear regression analysis,coefficient of variation and geographic detector model.Results The results showed that:1)Vegetation in Zoige region showed a fluctuating upward trend from 1998 to 2020,with an average annual growth rate of 0.0043 and an average annual vegetation NDVI of 0.79,showing an obvious trend of vegetation improvement.The overall spatial distribution was high in the southeast and low in the northwest.The proportion of area with annual average vegetation NDVI above 0.7 was 96%.2)The inter-annual variation rate of vegetation NDVI in Zoige region was low from 1998 to 2020,with an average value of 0.00018,and the area ratio of the stable area was 99.5%.The vegetation status was generally stable in the past 23 years,the average variation coefficient of vegetation NDVI was 16.50%,and the proportion of the area with variation coefficient lower than 20%was 85%.3)Altitude and annual mean temperature were the dominant natural geographic factors for vegetation NDVI variation in Zoige region,slope and aspect had little effect on vegetation NDVI.There were interactions among the physiographic factors on vegetation NDVI,which were two-factor enhancement(11.11%)and nonlinear enhancement(88.89%)effects.Conclusions The vegetation of Zoige region has improved in the past 23 years.The changes in natural geographical factors such as elevation and temperature should be fully considered in the selection of vegetation protection and restoration measures and models.