2000-2021年桂西南峰丛洼地流域植被净初级生产力演变特征及其归因

Evolution and attribution of net primary productivity of vegetation in the peakcluster depression basin of Southwest Guangxi from 2000 to 2021

监测植被净初级生产力的演变特征及其驱动力机制,对于深入了解陆地碳循环机制和促进生态环境可持续发展有着及其重要的作用。文章基于MOD17A3数据集植被净初级生产力(NPP)产品评估了2000−2021年桂西南典型喀斯特峰丛洼地流域植被净初级生产力的时空演变,并借助Theil-Sen Median趋势分析、Mann-Kendall检验方法、Hurst指数以及地理探测器等,研究区域内植被净初级生产力的空间分布、未来趋势、可持续性及驱动机制。结果表明:(1)2000−2021年研究区植被NPP均值为945.23 gC∙m^(−2)∙a^(−1),呈现出上升趋势,增加速率为3.5596 gC∙m^(−2)∙a^(−1)。喀斯特区域(4.5148 gC∙m^(−2)∙a^(−1))>研究区域(3.5596 gC∙m^(−2)∙a^(−1))>非喀斯特区域(2.7219 gC∙m^(−2)∙a^(−1));(2)植被NPP高值区域在防城港市周边,值皆大于1200 gC∙m^(−2)∙a^(−1);低值区散布于水文线附近;(3)Sen变化趋势显示,研究区22年间植被NPP增加区域面积(77.98%)显著大于减少区域面积(22.02%)。Hurst指数显示,区域植被NPP介于0~1之间,平均值为0.65,呈现出向负偏态分布;(4)土地利用/覆被、植被覆盖度与高程因子是本研究区植被NPP的显著控制因子,其次为坡度及土壤类型。

China has about 3.44×10^(6) km^(2) of karst area,and the most typical karst landscape−one of the largest in the world−is distributed in Southwest China,covering an area of 4.26×10^(5) km^(2).The karst area in Southwest China has a total population of more than 100 million in 48 ethnic minorities.Meanwhile,it is the major poverty-stricken area in China,with nearly half of the country's poor population.The peak-cluster depression basin in Guangxi is located in the southwest of Guangxi Zhuang Autonomous Region,including most parts of 3 prefecture-level cities−Baise,Wenshan and Chongzuo,as well as some areas of Nanning City and Fangchenggang City.The peak-cluster depression basin in southwest Guangxi is an old revolutionary base area and autonomous region for ethnic minorities along China's land boundary.It is not only an essential ecological barrier of the Pearl river basin,but also an important area for water conservation and biodiversity protection in China.However,this peak-cluster depression basin is subject to severe rock desertification and the scarcity of vegetation,because this basin is extensively developed with karst landscape,characterized by unique double-layer hydrogeological structures and shallow soil layer with severe soil erosion.This basin falls under the zone of southern subtropical climate,which is subdivided into the central subtropical climate zone(southern Guangxi climate zone),including Fangchenggang and Nanning,and the western subtropical climate zone(southwestern Guangxi climate zone),mainly including Baise,Pingxiang and Chongzuo.Due to the unique geography and fragile ecological environment of this basin,monitoring and analyzing the evolution and driving mechanism of the net primary productivity(NPP)of vegetation plays an important role in insight into the terrestrial carbon cycle mechanism and in sustainable development of the ecological environment.This study assessed the spatial and temporal evolution of NPP in the typical karst peak-cluster depression basin in southwestern Guangxi from 2000 to 2021,based on the MOD17A3 dataset NPP products,and investigated the spatial distribution,future trends,sustainability and driving mechanisms of NPP in this region with Theil-Sen Median trend analysis,Mann-Kendall test method,Hurst index and geodetector.The results show:(1)From 2000 to 2021,the average value of NPP in the study area was 945.23 gC∙m^(−2)∙a^(−1),with an increase rate of 3.5596 gC∙m^(−2)∙a^(−1).The increase rate can be ranked as:4.5148 gC∙m^(−2)∙a^(−1)in the karst area>3.5596 gC∙m^(−2)∙a^(−1)in the study area>2.7219 gC∙m^(−2)∙a^(−1)in the non-karst area.(2)The areas with high NPP values(all greater than 1,200 gC∙m^(−2)∙a^(−1))were situated around Fangchenggang City;the areas with low values were scattered along the hydrological line.(3)The trend of Sen showed that the area with an increase of vegetation NPP(77.98%)was significantly larger than the area with a decrease of NPP(22.02%)during 22 years in the study area.Hurst index showed that the regional vegetation NPP values ranged from 0 to 1,averaging 0.65,with a negative skew distribution.(4)The quantitative attribution results of geodetector showed that land use/cover,vegetation coverage and elevation factors were the significant control factors of NPP in the study area,followed by slope and soil type.