近20年来西藏地区NPP时空变化及影响因素

Spatial-temporal Variation of Net Primary Productivity and Its Influencing Factors in Tibet Over Past 20 Years

[目的]探究西藏地区植被净初级生产力(net primary productivity,NPP)时空变化规律以及与影响因素之间的关联,为该区绿色生态建设和国土资源开发提供科学依据。[方法]利用MOD17A3 NPP数据、气象数据和植被类型空间分布等数据,采用趋势分析、偏离分析、相关性分析法和地理探测器等方法,对西藏地区2000—2020年的NPP时空格局及影响因素进行分析。[结果]①西藏地区2000—2020年NPP总体呈增长趋势,均值为137.36 g/(m^(2)·a),波动范围为128.04~148.06 g/(m^(2)·a),总体分布具有明显的空间异质性,呈东南高西北低的趋势;②不同植被类型的年均NPP差异明显,其中阔叶林最高,为1107.09 g/(m^(2)·a),荒漠最低,为29.76 g/(m^(2)·a),按NPP均值大小顺序排列为:阔叶林>栽培植被>针叶林>灌丛>草甸>高山植被>草原>荒漠;③NPP与气温和降雨均存在明显相关性,其中NPP与降雨多呈负相关,与气温多呈正相关;④各影响因子对NPP空间分异性解释力依次排列为:降雨量>海拔>气温>坡度>植被类型>土地利用类型,自然因子对NPP的影响力强于人为因子,双因子交互作用影响力强于单因子。[结论]西藏地区水热条件分布不均,NPP空间分布差异较大,整体生态系统呈改善趋势,局部生态系统较脆弱。

[Objective]The temporal and spatial variation of net primary productivity(NPP)of vegetation in Tibet and its relationship with influencing factors were determined in order to provide a scientific basis for green ecological construction and the development of national land resources in the region.[Methods]We used MOD17A3 NPP data,meteorological data,and spatial distribution data of vegetation types with the methods of trend analysis,bias analysis,correlation analysis,and geodetector to analyze the spatial-temporal patterns and influencing factors of NPP in Tibet from 2000 to 2020.[Results]①NPP in most areas of Tibet showed an increasing trend from 2000 to 2020.The average annual NPP was 137.36 g/(m^(2)·a),ranging from 128.04 g/(m^(2)·a)to 148.06 g/(m^(2)·a).The overall distribution of NPP exhibited obvious spatial heterogeneity,with high values in the southeast and low values in the northwest.②There were significant differences in annual NPP among different vegetation types,with broadleaf forest having the highest NPP of 1107.09 g/(m^(2)·a)and desert having the lowest NPP of 29.76 g/(m^(2)·a).The mean values followed the order of broadleaf forest>cultivated vegetation>coniferous forest>shrub>meadow>alpine vegetation>grassland>desert.③NPP was significantly correlated with both temperature and precipitation.NPP was mostly negatively correlated with precipitation and positively correlated with temperature.④The explanatory power of each influencing factor on the spatial variability of NPP followed the order of rainfall>altitude>temperature>slope>vegetation type>land use type.Natural factors had a stronger influence on NPP than anthropogenic factors.[Conclusion]The interaction of double factor was stronger than that of single factor.The distribution of water and heat conditions in Tibet was uneven,and the spatial distribution of NPP varied greatly.The overall condition of ecosystems in Tibet has generally improved over time,but local ecosystems were found to be relatively fragile.