甘南藏族自治州植被净初级生产力时空变化及驱动力

Spatio-temporal changes and driving force analysis of vegetation net primary productivity in Gannan Tibetan Autonomous Prefecture

自2003年开始甘南藏族自治州推行了“退耕还草”等一系列生态保护政策,对区域植被状态产生了一定的影响。目前针对甘南州不同植被类型下植被净初级生产力(NPP)与归一化植被指数(NDVI)、太阳辐射、气温、降水间响应机制的研究尚不明晰,且关于该区域植被NPP时空特征变化及重心迁移的探讨尚少。本研究基于MODIS遥感数据、气象数据、植被类型数据,利用Carnegie-Ames-Stanford Approach(CASA)模型估算了甘南州2000-2019年植被NPP,分析了NPP时空变化特征,探讨了不同植被类型下植被NPP与NDVI、气温、降水以及太阳辐射之间的响应关系。结果表明:1)2000-2019年植被NPP年均值为621.79 g·m^(−2),96.63%区域呈现为增长趋势。2)2000-2019年植被NPP重心整体呈现西北向东南迁移,东南部植被NPP增速高于西北部。3)植被NPP与气温、降水、太阳辐射间整体上呈明显的正相关关系,北部边缘及东部中心地带呈负相关关系。4)林地、灌丛、草地的NPP均呈稳定增长,湿地类型下除NPP外气温亦呈明显增长。本研究可为评价生态质量及生态工程的实施效果提供理论支撑。

Since 2003,the Gannan Tibetan Autonomous Prefecture has implemented a series of regional ecological protection policies,including“returning farmland to grass”.The response mechanisms between net primary productivity(NPP)and the normalized difference vegetation index(NDVI),solar radiation,temperature,and precipitation in different vegetation types in Gannan are still unclear.Furthermore,the spatial and temporal characteristics of vegetation NPP and the migration of the center of gravity in the region have not been investigated.In this study,based on MODIS remote sensing,meteorological,and vegetation type data,the Carnegie-Ames-Stanford Approach(CASA)model was used to estimate vegetation NPP in Gannan from 2000 to 2019,analyze the spatial and temporal variation characteristics of NPP,and explore the response relationships between vegetation NPP and NDVI,temperature,precipitation,and solar radiation under different vegetation types.The annual average value of vegetation NPP from 2000 to 2019 was 621.79 g·m^(−2),and 96.63%of the area showed an increasing trend.The center of gravity of vegetation NPP from 2000 to 2019 showed an overall northwest to southeast migration,and the growth rate of vegetation NPP in the southeast was higher than that in the northwest.The overall positive relationship between vegetation NPP and temperature,precipitation,and solar radiation was obvious,and the northern edge and the eastern center showed a negative relationship.Finally,the NPP of woodland,scrub,and grassland showed a stable increase,and the temperature of the wetland type also showed a significant increase in addition to NPP.The findings provide theoretical support for the evaluation of ecological quality and implementation of ecological projects.