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Spatial And Temporal Variation And Drivers Of NPP In Southwest China

Posted on:2024-03-16Degree:MasterType:Thesis
Country:ChinaCandidate:B X MaFull Text:PDF
GTID:2530307139974959Subject:Surveying and mapping engineering
Abstract/Summary:PDF Full Text Request
Net primary productivity(NPP)is an important component of the terrestrial carbon cycle,which not only reflects the recovery and degradation of vegetation in the natural environment,but also is the main factor to determine the carbon cycle process in the ecosystem,reflecting the carbon sequestration capacity in the natural environment,and plays an important role in global climate change.With the development of human society,the impact of human activities on the vegetation ecosystem in southwest China has been strengthened,and the systematic study of NPP change characteristics and its driving forces in southwest China can provide theoretical basis and scientific suggestions for the ecological civilization construction in China.This paper estimates NPP in southwest China from 2001 to 2019 based on CASA model,combines meteorological station data,land use data,DEM and other data,and analyzes the spatial and temporal distribution and change characteristics of NPP in southwest China at different scales using Theil-Sen Median trend analysis,M-K test,R/S analysis,Geodetector,Partial correlation analysis and Residual trend analysis,and explored the response of NPP to changes in meteorological factors in Southwest China at different scales,used multi-temporal land use data to separate regions of climate change and human activities,and explored the effects of climate change and human activities on NPP in Southwest China.The main conclusions are as follows:(1)The overall spatial distribution of NPP in Southwest China at different time scales from2001 to 2019 showed the distribution characteristics of high in the south and low in the north,with obvious seasonal changes,and the highest proportion of interannual NPP in summer;the highest NPP in forest-like vegetation and the lowest in bare land;the distribution of NPP was greatly influenced by topographic factors,and the NPP showed a trend of increasing and then decreasing with the increase of elevation and slope;except for summer,the NPP showed an increasing trend at different time scales,with the highest increase in interannual variation in broadleaf forest,crop and wetland NPP,and the highest decrease in coniferous forest and scrub;there is a risk of future degradation of NPP in southwest China,with obvious spatial variation at seasonal scales and large differences.(2)The dominant factors of NPP changes in different years in Southwest China are different.Temperature,biological cold index and precipitation can best explain the distribution state of NPP;NPP is closely related to temperature,and NPP always shows positive correlation with temperature under different time scales,while the correlation with precipitation is more complicated;the time lag between NPP and temperature and precipitation has significant spatial variability in different regions.The majority of regions had shorter time lags of NPP to temperature and precipitation,and fewer regions had longer time lags;the time lags of NPP to temperature changes were shorter in interannual,growing season,spring and summer,while in autumn and winter,the time lags of NPP to precipitation changes were shorter;except for autumn,the time lags of crops to temperature and precipitation were lower than those of other vegetation,and the time lags of bare ground to temperature and precipitation were higher than those of other vegetation.In general,the time lag of NPP to temperature is lower than that to precipitation,indicating that NPP is more sensitive to temperature changes during the growing season.(3)The effects of human activities and climate change on NPP were mainly positive,but the degree of influence was low;whether climate change and human activities acted together or alone to cause an increase in NPP,the area of image elements was much higher than that of image elements causing a decrease in NPP,and the combined effect of climate change and human activities was the main reason for the increase in NPP in Southwest China;the relative effects of climate change and human activities on NPP in Southwest China were higher than those of other vegetation.The relative contributions of climate change and human activities to NPP in Southwest China were 49% and 51%,respectively.
Keywords/Search Tags:NPP, Southwest China, Climate Change, Human Activities, Multi-Scale
PDF Full Text Request
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