柳州市植被生态质量时空特征及其与气候因子的关系

Spatial and Temporal Characteristics of Vegetation Ecological Quality and Its Relationships with Climate Factors in Liuzhou

为客观监测与评价地市尺度植被生态质量和探讨其与主要驱动气候因子的关系,采用2000—2022年MODIS NDVI数据,基于植被净初级生产力(NPP)和植被覆盖度(FVC)构建植被生态质量指数(EQI),采用转移矩阵和线性回归趋势方法,分析柳州市不同县区及不同土地利用类型和植被类型EQI的时空分布和变化特征;采用相关性分析法,分析EQI与气候的相关性。结果表明,2000—2022年柳州市平均EQI总体偏好,其中融水苗族自治县EQI均值最高,城中区最低;土地利用类型中,林地EQI均值最高,城乡、工矿和居民用地最低;植被类型中,阔叶林EQI均值最高,栽培植被最低。2000—2022年柳州市显著变绿,EQI显著上升面积占比为84.72%,上升速率为0.15~1.79/a,柳江区东部和南部、鱼峰区南部及鹿寨县南部上升速率较快。EQI与年均气温、年总降水量呈显著和极显著正相关面积占比分别为63.81%和28.16%,与年均气温呈极显著正相关的区域主要分布在鹿寨县东北部、融水苗族自治县东北部、融安县北部和三江侗族自治县,与年总降水量呈显著和极显著正相关的区域主要分布在融水苗族自治县、融安县、柳城县及柳南区和柳北区北部。气温对EQI的影响范围比降水更广。

In order to objectively monitor and evaluate ecological quality of vegetation at city scales and to explore its relationships with main driving climate factors,ecological quality index(EQI)of vegetation was constructed based on vegetation net primary productivity(NPP)and fractional vegetation cover(FVC)using MODIS NDVI data from 2000 to 2022.Transfer matrix and linear regression trend methods were used to analyze spatial and temporal distributions and change characteristics of EQI in different counties and districts,different land use types and vegetation types in Liuzhou,and correlation analysis method was used to analyze correlations among EQI and climate.Results showed that average EQI in Liuzhou was generally good from 2000 to 2022,with Miao autonomous county of Rongshui having the highest mean of EQI and Chengzhong district having the lowest;among land use types,mean of EQI for woodlands was the highest,and that for urban and rural,industrial and mining,and residential lands was the lowest;and among vegetation types,mean of EQI for broad-leaved forests was the highest and that for cultivated vegetation was the lowest.From 2000 to 2022,Liuzhou became significantly greener,and proportion of areas with significant increase in EQI was 84.72%,with increase rate of 0.15~1.79/a.Faster increase rates were found in southern and eastern parts of Liujiang district,southern part of Yufeng district,and southern part of Luzhai county.Proportions of areas with significant and extremely significant positive correlations among EQI and mean annual temperature and total annual precipitation were 63.81% and 28.16% respectively.Areas with extremely significant positive correlations with mean annual temperature were mainly distributed in northeastern part of Luzhai county,northeastern part of Miao autonomous county of Rongshui,northern part of Rong'an county and Dong autonomous county of Sanjiang,while areas with significant and extremely significant positive correlations with total annual precipitation were mainly distributed in Miao autonomous county of Rongshui,Rong'an county,Liucheng county,northern part of Liunan district and northern part of Liubei district.Influence of temperature on EQI was more extensive than that of precipitation.