1988—2018年间洱海流域植被覆盖度时空变换特征探究

Spatial and temporal change characteristics of vegetation coverage in Erhai Lake basin during 1988—2018

植被覆盖度作为反映地表生态环境的重要指标,被广泛应用于区域生态状况与生态地质问题的调查与研究工作中。以洱海流域为研究区,基于谷歌地球引擎(Google Earth Engine,GEE)云计算平台,利用455景30 m空间分辨率Landsat系列影像获取了1988—2018年间流域尺度的年最大归一化植被指数(normalized difference vegetation index,NDVI)值,采用像元二分模型定量估算了洱海流域的植被覆盖度,通过线性回归模型分析植被覆盖度的时空变化特征,进一步探讨了植被覆盖度与岩石类型的内在关系。研究结果表明:①1988—2018年间洱海流域植被覆盖度整体上呈现持续波动增长的趋势,增速为0.38%/a;②流域内分布以高植被覆盖为主,其中82.54%的区域植被覆盖状况持续改善,而持续退化的区域仅占3.27%,主要分布在城镇化显著的区域;③流域内不同岩性单元上的植被覆盖度存在明显差异,平均植被覆盖度最高的是变质岩区域,最低的是白云岩和火山岩。

As an important indicator reflecting the surface ecological environment,vegetation is widely used in the study of regional resources and environmental carrying capacity.Taking Erhai Lake basin as an example and based on the Google Earth Engine remote sensing big data cloud computing platform,the authors obtained the annual maximum normalized difference vegetation index(NDVI)value of Erhai Lake basin in 1988—2018 by using nearly 455 Landsat series images with 30 m resolution.The pixel binary model was used for quantitative estimation of fractional vegetation cover(FVC),and the spatial-temporal change characteristics of FVC in Erhai Lake basin were comprehensively analyzed through the linear regression model.Additionally,the internal relationship between FVC and geological lithology was investigated.The results are as follows:(1)From 1988 to 2018,the vegetation coverage of Erhai Lake basin showed a trend of continuous fluctuation growth,with a growth rate of 0.38%/a.(2)The basin was dominated by high vegetation coverage,of which 82.54%of the regional vegetation coverage continued to be improved,whereas the area of continuous degradation accounted for only 3.27%,which was mainly distributed in the area with significant urbanization.(3)the FVC varied in different types of lithological areas,among which the highest was metamorphic rock,and the lowest was dolomite and volcanic rock.