近20年来西南地区植被净初级生产力时空变化与影响因素及其对生态工程响应

植被净初级生产力（NPP）是研究陆地生态系统中物质和能量转换的重要指标,NPP的空间分布与区域气候、植被生长以及人类活动等因素息息相关,其变化能反映植被群落的生产能力,是生态系统功能和结构变化的重要表征。近20年来,中国西南地区植被NPP呈现增长趋势。然而,目前对NPP时空变化格局及潜在原因尚不清楚。因此,利用2001-2018年间MODIS-NPP、岩性、气候、土地利用、造林面积和石漠化治理情况等数据,对西南地区植被NPP的时空变化趋势及其成因进行了分析。结果发现：（1）2001-2018年间,中国西南地区植被NPP总体呈增长趋势,突变分析结果显示,2012-2018年间NPP的增长速度（5.13 gC m^-2a^-1）比2001-2011年更快（1.78 gC m^-2a^-1）,在两个时段,岩溶区NPP增长速度都高于非岩溶区;（2）对西南地区植被NPP变化与气候因子的相关分析结果显示,2001-2011年与2012-2018年两个时间段内NPP与温度的平均相关性（R=0.19,0.26）要高于NPP与降水的平均相关性（R=0.07,0.05）,表明西南地区植被NPP更容易受到温度的影响;（3）对两个时期土地利用变化下NPP总量的变化情况的研究结果显示,2001-2011年期间城市用地面积增加使得NPP总量下降,而2012-2018年未利用地面积增长造成了NPP总量下降;（4）2001-2018年西南地区累计造林面积与NPP存在显著正相关性（R=0.7,P<0.05）,说明"退耕还林"工程实施促进了西南地区NPP增长。对石漠化面积统计结果表明,2011年后石漠化面积显著减少,这与NPP的突变点一致,表明石漠化治理对西南地区NPP增长有重要促进作用。

Spatio-temporal changes and influencing factors of vegetation net primary productivity in southwest China in the past 20 years and its response to ecological engineering

Vegetation net primary productivity (NPP) is an important indicator for studying material and energy flows in terrestrial ecosystems. The spatial distribution of NPP is closely related to factors such as regional climate, vegetation growth, and human activities. Its changes can reflect the productivity of vegetation communities and arean important characterization of the function and structure change of ecosystem. In the past two decades, vegetation NPP in the Southwest China has shown an increasing trend. However, it is still unclear about the temporal and spatial patterns of the NPP and the underlying reasons. Therefore, this paper uses MODIS-NPP, lithology, climate, land use, afforestation area, and rocky desertification control data from 2001 to 2018 to analyze the spatiotemporal trends and causes of vegetation NPP in the Southwest China. The results found that:(1) during 2001-2018, vegetation NPP in the Southwest China showed an overall increasing trend. The results of mann-kendall test indicated that the growth rate of NPP (5.13 gC m^-2a^-1) during 2012-2018 was faster than that in 2001-2011 (1.78 gC m^-2a^-1). During 2001-2011 and 2012-2018 the growth rate of NPP in karst areas was higher than that in non-karst areas; (2) The correlation analysis results of vegetation NPP changes and climatic factors in the Southwest China showed that the correlation between NPP changes and temperature(R=0.19,0.26) is higher than that between NPP changes and precipitation(R=0.07,0.05) in both the period of 2001-2011 and 2012-2018, indicating that vegetation NPP in the Southwest China is more susceptible to temperature;(3) The changes of the total amount of NPP under land use changes in 2001-2011 and 2012-2018 showed that the increase in urban land area during 2001-2011 caused the total amount of NPP to decrease, while the area of unused land increase in 2012-2018 resulted in the decrease of the total amount of NPP; (4) The cumulative afforestation area in the Southwest China from 2001 to 2018 was significantly positively correlated with NPP (R=0.7, P<0.05), indicating that the implementation of the"Grain for Green Project" promoted the growth of NPP in the Southwest China. The statistical results show that the rocky desertification area has decreased significantly after 2011, which is consistent with the mutation point of NPP, indicating that the control of rocky desertification plays an important role in the growth of NPP in the Southwest China.