Forest Vegetation Changes And Ecological Functions In The Bashang Plateau And The Mountainous Area Of Northern North China

The Bashang Plateau and the mountainous area of northern North China are located in the important area of agriculture and animal husbandry.The ecological environment is fragile and soil erosion is serious.The region has implemented ecological governance since 1999,and the ecosystem has been improved to some extent,but the threat factors such as forest vegetation degradation and grassland reduction in the region are still significant.Therefore,three factors,Net Primary Productivity(NPP),Fraction Vegetation Cover(FVC)and Leaf Area Index(LAI),were selected to analyze the changes of forest vegetation in the region,explore and climate the relevance of factors,to assess the changes in the main ecological functions of the region,and provide a scientific basis for ecological environment restoration and resource management optimization.The CASA model,univariate linear regression,Hurst index,partial correlation analysis and other methods were used to analyze the spatial and temporal distribution characteristics and response to climate change of each factor from 2000 to 2018,and the main ecological functions were evaluated through the In VEST(Integrated Valuation of Ecosystem Services and Tradeoffs)model.Changes,the main conclusions reached are as follows:(1)From 1990 to 2018,the average precipitation was 462.28mm,with a general downward trend of fluctuations,with a rate of change of 10.8mm/10yr;the annual average temperature was 8.97?,with an overall upward trend of fluctuations,with an increase rate of 0.16?/10yr;the average wind speed was2.38 m/s,the overall trend is declining fluctuation,the rate of decline is 0.01m/s.(2)The interannual annual average of FVC is 57.65%,rising at a rate of 0.89%/yr;FVC is unevenly distributed during the year,reaching a maximum of 57.52%in July,with the fastest growth in summer;the spatial distribution gradually increases from west to east.The interannual increase rate is 0.01/yr,the area with an increasing trend is 38.79%,and the area with a decreasing trend is 23.03%;the FVC coefficient of variation is 0.32,and the interannual change is small;the future FVC will continue to increase the area accounting for 24.70%;and precipitation The partial correlation coefficient with temperature is 0.21-0.10,and the area of positive correlation accounts for 92.07%and 32.84%respectively.The complex correlation coefficients of precipitation,temperature and wind speed explain50%of FVC changes;the area of human activities for promotion accounts for 62.19%,The change trend of the residual value is 0.004,indicating that human activities are beneficial to the increase of forest vegetation.(3)The interannual average value of LAI is 2.63,with the largest LAI value in July and August of the year,accounting for 44.12%of the year's LAI,and the fastest growth in summer;the spatial distribution of LAI gradually increases from west to east,with an average increase rate of 0.06/yr,showing a decrease The trend area accounts for 8.59%,and the increasing trend area accounts for 56.63%;the average LAI coefficient of variation is 0.59,and the interannual change is large;the future LAI continues to increase the area of 39.32%;the partial correlation coefficients with precipitation and temperature are0.38,0.08,The area of positive correlation area accounted for 94.83%and 66.12%,and the complex correlation coefficients of precipitation,temperature and wind speed explained 58%of LAI change.(4)By comparing the simulation results of the CASA model with MODIS data,it is found that the model simulates NPP data with good results and reliability;the annual average NPP is 367.99 g C/m~2�yr,which fluctuates at a rate of 10.74 g C/m~2�yr;during the year The distribution of NPP is uneven,accounting for 89.91%of the total NPP from May to September,and the changes during the year are mainly in summer.Its spatial distribution gradually increases from west to east,with an interannual increase rate of9.04g C/m~2�yr,with an increasing area accounting for 95.98%;the average value of the interannual NPP coefficient of variation is 0.20,and the interannual change is small;the future The area of NPP that continues to increase accounts for 32.14%;the correlation coefficients with precipitation and temperature are 0.47 and 0.11,respectively,and the complex correlation coefficients of precipitation,temperature and wind speed explain 67%of NPP changes.(5)The Habitat Quality Index increased by 0.04.The areas with high and high Habitat Quality Index in the past four years mainly changed,increasing by 14.81%and decreasing by 13.36%.The four-year water conservation is 35.90mm,44.49mm,61.94mm,58.58mm,an increase of 22.68mm,and the total increase is 34.06�108m~3.The average soil erosion modulus is 32.15t/hm~2,22.91 t/hm~2,22.58 t/hm~2,26.11 t/hm~2,the soil erosion amount is 4.96�10~8t,3.53�10~8t,3.48�10~8t,4.03�10~8t,soil erosion amount reduced by 18.75%.The soil retention was 4.18�10~8t,7.16�10~8t,10.09�10~8t,13.50�10~8t,the soil retention increased by 9.32�10~8t,and the average soil retention per unit was 56.60t/hm~2.