| NPP is an important indicator of terrestrial ecosystem health as an important component of material cycling and energy flow in terrestrial ecosystems and the measurement of terrestrial vegetation growth or production activities.Xinghai Basin is located in the core area of Sanjiangyuan Nature Reserve.The natural grassland with alpine meadow and alpine grassland is the largest ecological system in this area.It is of great value in the development of animal husbandry,the maintenance of biodiversity and the maintenance of ecological balance.NPP can reflect the plant community in the natural environment conditions of production capacity.There were significant differences in NPP at the regional scale,and there were significant differences in the NPP of different soil erosion units.Based on the data of remote sense(MOD17A3,DEM,Landsat OLI),meteorological data,soil nutrient data,socio-economic statistics and other auxiliary data in Xinghai basin,the authors analyzed the relationship between Xinghai basin and its different soil erosion types from 2000 to 2014 the temporal and spatial dynamics of vegetation NPP,the relationship between the change of NPP and the type of soil erosion.The relationship between climatic factors,soil nutrients and vegetation NPP in Xinghai basin was analyzed from the whole scale using Pearson correlation coefficient method.The study draws the following conclusions:(1)From 2000 to 2014,the average NPP of the study area fluctuated with time in a certain range,and the fluctuation range was 127.23-174.69 g C / m~2 · a,the average of 15 years NPP was 150.45 g C / m~2 · a,with NPP of 127.23 g C / m~2 · a in 2001,the highest NPP in 2010,reaching 174.69 g C / m~2 · a.The annual NPP distribution in the study area in the period from 2000 to 2014 showed that the distribution of NPP in the southern part of the study area was greater than that in the north and east than in the west.The overall performance was gradually increasing from northwest to southeast,and this trend was better than that in the plateau region consistency.The NPP of this area is mainly between 120-220 g C / m~2 · a,about 50% of the area,followed by NPP less than 120 g C / m~2 · a,which accounts for less than 35% of the area;NPP> 220 g C / m~2 · a minimum,generally less than 15%.The change trend of NPP in 15 years in Xinghai basin showed spatial heterogeneity,and the trend of moderate reduction and the basic change was significant,and the local area showed an increasing trend.(2)There were significant differences in NPP among different types of soil erosion.The average NPP of wind erosion zone increased with time in 2000-2000,and the average NPP was 173.33 g C / m~2 · a in 15 years.The NPP of the area was mainly between 120-220 g C / m~2 · a,The percentage of the area occupied by the area in about 60%.In the western region of the study area,the average NPP of freeze-thaw erosion zone increased with time in 2000 to 2014,and the average NPP of 15 years was 135.63 g C / m~2 · a.The NPP of this area was mainly concentrated Between 70-170 g C / m~2 · a,the percentage of the area occupied by the area is about 50%,and the annual average NPP in the freeze-thaw zone is increasing from northwest to southeast.The average NPP of the hydraulic erosion area increased with time in the period from 2000 to 2014,and the average NPP of 15 years was increasing in the ridge area and the surrounding area along the Daheba River and Qu Shi'an River.And the vegetation NPP in the area is mainly between 120-220 g C / m~2 · a,and the percentage of the area occupied is about 60%.(3)The changes of NPP mean values in different soil erosion types in Xinghai basin from 2000 to 2014 were analyzed.The mean NPP of Xinghai basin in the study period was 150.45 g C / m~2 · a.The annual variation curve of NPP is 135.63 g C / m~2 · a,and the interannual variation curve is lower than that of the whole Xinghai basin due to its high altitude,low temperature and large temperature difference.The NPP of the hydraulic erosion zone and the wind erosion area are 175.13 g C / m~2 · a and 173.33 g C / m~2 · a,respectively,which are consistent with the trend of interannual variability curve,which is higher than the average NPP of vegetation in Xinghai basin.This is mainly related to its relatively low elevation,good hydrothermal conditions,higher vegetation coverage.(4)The change of NPP was positively correlated with annual mean temperature and there was a significant positive correlation with total nitrogen,alkali-hydrolyzable nitrogen,available phosphoeus and organic matter in soil nutrients. |
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