基于改进CASA模型的云南省植被NPP时空格局分析

Spatio-Temporal Pattern Analysis of Vegetation NPP in Yunnan Province Based on Improved CASA Model

植被净初级生产力(NPP)是衡量生态系统生产力水平的指标之一,利用生态遥感相结合的手段对其估算具有重要意义。运用改进的CASA模型,基于MODIS植被指数产品、气象数据、土地覆被数据,对云南省2000年、2005年、2010年、2015年、2020年的植被NPP进行估算,采用Moran′s I指数、Getis-Ord Gi*热点分析探讨其空间分布特征,并与我国生态功能保护区进行叠加分析。研究表明:1)云南省近20年植被NPP呈先减少再增加的趋势,平均值为822.98 gc/(m^(2)·a);月度植被NPP夏季达到最高,冬季最低;不同植被类型中,常绿阔叶林的NPP值最高。2)各年份植被NPP空间分布均由南向北减少,全局空间自相关Moran′s I指数均大于0.7,NPP热点区主要位于滇西南边境一带,冷点区位于滇西北、滇中城市化地区。3)植被净初级生产力热点区与生态功能保护区叠加相交于西双版纳生态功能保护区、西南喀斯特生态功能保护区,各年叠加面积占热点区域总面积的23%~26%。可见,云南省近20年NPP呈波动上升趋势,空间分布异质性明显。研究该结果可为云南植被监测、生态环境保护提供科学参考。

Vegetation net primary productivity(NPP)is one of the indicators to measure the level of ecosystem productivity,it is of great significance to estimate it by using the combination of ecology and remote sensing.In this study,we applied the improved CASA model;based on the MODIS vegetation index product,meteorological data,and land cover data;estimated the vegetation NPP in Yunnan Province in 2000,2005,2010,2015,and 2020,and explored its spatial distribution characteristics using the Moran′s I index,Getis-Ord Gi*hotspot analysis,and overlaying analysis with China′s ecologically Functional Protected Areas in China were superimposed and analyzed.The results showed that:1)the vegetation NPP in Yunnan Province in the past 20 years showed a trend of decreasing and then increasing trend,with an average value of 822.98 gc/(m^(2) a);the monthly vegetation NPP reached the highest in summer and the lowest in winter;and among the different vegetation types,the evergreen broadleaf forests had the highest NPP values.2)The spatial distribution of vegetation NPP decreased from south to north in each year,and the global spatial autocorrelation Moran′s I index was greater than 0.7.The NPP hot spots were mainly located in the southwestern border of Yunnan,and the cold spots were located in the northwestern and central urbanization areas of Yunnan.3)NPP hotspot areas superimposed with ecological function reserve intersected in Xishuangbanna Ecological Function Reserve and Southwest Karst Ecological Function Reserve,and the superimposed area accounted for 23%~26%of the total area of hotspot areas in each year.The study shows that NPP in Yunnan Province has shown a fluctuating upward trend in the past 20 years,and the results can provide scientific references for vegetation monitoring and ecological environmental protection in Yunnan Province.