2001~2020年嘉陵江流域植被覆盖度时空变化特征

Spatial-temporal variations of fractional vegetation coverage in Jialing River Basin from 2001 to 2020

植被覆盖度是反映一个地区生态系统健康程度的重要指标,掌握植被覆盖度变化特征有助于了解地区生态环境演变,对于指导地区可持续发展具有重要意义。基于MODIS-NDVI数据,应用像元二分模型进行植被覆盖度提取,采用一元线性回归分析、稳定性分析和GIS空间分析等方法分析了2001~2020年嘉陵江流域植被覆盖度时空变化特征。结果表明:①2001~2020年嘉陵江流域的植被覆盖度总体上呈现上升趋势,植被覆盖率较好,位于0.70~0.81之间。②流域内38.05%的区域植被保持稳定不变,呈现改善状态的区域占44.69%,主要为东南部低海拔地区和陇南地区,呈现退化的区域占17.26%,主要为高海拔地区和城市周边区域。流域内植被稳定性大部分为弱变异,中等变异区与河流相关性较高,强变异区分布于城市地区和高山雪线附近。③在500~1000 m海拔范围内,植被改善比例达到最大,在3000~4000 m海拔范围内,植被的退化比例最大。植被改善主要的坡度范围为0°~18°,但在0°~5°范围内植被退化的比例较大。随着坡度的不断升高,植被的退化比例逐渐升高,改善比例逐渐下降。植被覆盖度变化的坡向差异不大,各个坡向基本一致,以稳定和改善为主。④矿产开发、城市扩张、农业种植等人类活动是导致植被破坏的重要原因。研究表明,近20 a来嘉陵江流域生态环境逐渐向着良性的方向发展。研究成果可帮助相关部门构建嘉陵江流域生态保护屏障,为流域生态环境综合监测和治理提供科学依据。

Fractional Vegetation Cover(FVC)is an important indicator of ecosystem health in a certain area.Knowing the change characteristics of FVC is helpful to understanding the evolution of regional ecological environment and is of great significance for guiding the sustainable development of a region.Based on MODIS-NDVI data,the dimidiate pixel model was used to extract FVC.Then,the FVC of Jialing River Basin from 2001 to 2020 was analyzed by using univariate linear regression analysis,stability analysis and GIS spatial analysis.The results showed that:①From 2001 to 2020,the FVC of the Jialing River Basin has shown an upward trend as a whole,with a good FVC ranging from 0.70 to 0.81.②38.05%of the region in the basin remained stable,44.69%of the region showed an improving status,mainly in the southeast low-altitude areas and southern Gansu area,and the degraded area accounted for 17.26%,mainly in high-altitude areas and surrounding areas of cities.The stability of vegetation in the basin was mostly weak variation.The medium variation area had a high correlation with the river.The strong variation area was distributed in the urban area and near the alpine snow line.③In the range of 500~1000 m altitude,the vegetation improvement ratio reached the maximum,but in the range of 3000~4000 m altitude,the vegetation degradation ratio decreased to the maximum.The vegetation improvement mainly happened in slope range of was 0~18°.However,the proportion of vegetation degradation in the slope of 0~5°was relatively large.With the continuous rise of slope gradient,the proportion of vegetation degradation gradually increased,and the improvement ratio gradually decreased.There was little difference in the aspect of FVC change,and each aspect was basically the same,which was mainly stable and improved.④Mineral exploitation,urban expansion,agricultural planting and other human activities were important causes of vegetation destruction.The research showed that the ecological environment of the Jialing River Basin gradually developed in a positive direction in the past 20 years.And it can help relevant departments build an ecological protection barrier of the Jialing River Basin,provide scientific basis for the comprehensive monitoring and management of the ecological environment of the basin,and promote the green and healthy development of the basin.