| Aming at the deficiency of quantitative analysis and the multi-scale comparative study of driving force to biocapacity in river basin,this study,taking Shiyang River basin which located in northwestern China and have typical characteristics as example,by using long time series fundamental data from 1991 to 2013,including socio-economic statistical data,topography,natural meteorological,ecology,hydrological data and 18 high resolution Landsat satellite images.On the basis of RS/GIS technology,ecological footprint(EF)model,trend analysis,partial least squares method and CA-Markov model,the driving forces of biocapacity at basin,county,township-scale in Shiyang River Basin was explored for the first time,.Furthermore,prediction simulation on biocapacity was studied.The main conclusions are as follows:1.Spatio-temporal dynamics of biocapacity(1)Temporal Variation①At the basin-scale,per capita biocapacity increased from 1.24gha to 1.28gha in Shiyang River Basin,which showed a growing trend as a whole,and the average annual growth of per capita biocapacity was 0.002gha.②At the county-scale,the trend of per capita biocapacity were different.the per capita biocapacity in Minqin county and Sunan county were relatively high,and the per capita biocapacity in Jinchuan district and Liangzhou district were relatively low,per capita biocapacity in Minqin county and Sunan county were increased and varied in a larger range,however,Liangzhou presented a decreasing trend in per capita biocapacity,an increasing trend with a small fluctuation was found in Gulang,Tianzhu,Yongchang and Jinchuan.③At the township-scale,there was a remarkable spatial heterogeneity in per capita biocapacity of Qilian township and Huangcheng town,which had an increasing trend and vary in a larger range,was higher than other townships,Jinta town and Xuebai town showed a decreasing tendency,which had a growth trend year by year(2)Spatial variation:In Shiyang River basin as a whole,the distribution pattern of the absolute valueof biocapacity have no great change,however,there was a remarkable spatial heterogeneity within the basin.high value areas are mainly located at the middle and lower reaches of oases area of Shiyang River basin,low-value areas were mainly distributed at the desert area in the middle and lower reaches of Shiyang River basin,especially in the east and west of Minqin County.But regional change over time also showed different trend.The distribution of the absolute value of biocapacity changes most obviously in mountain area at the upper reaches of Shiyang River basin,the low value of the absolute value of biocapacity in 2002 increased 638.18km2 compared to 1992,since then to 2012 remained stable.The absolute value of biocapacityof a small number of areas in Minqin oases decreased,and showings a fragmentation trend.the low value of the absolute value of biocapacity was widely distributed at the lower reaches of Shiyang River basin,and from the year 1992,sporadic patches with higher absolute value of biocapacity had appeared.2.Driving force to biocapacity in Shiyang River basinBy Collecting and constructing quantitative human and natural index system,andconducting a preliminary correlation analysis between every specific indicator and biocapacity,24 major indicators as driving force were selected.Quantitative analysis of the contribution-rate of each factor to biocapacity in recent 23 years(1991-2013)revealed the cause of biocapacity change in Shiyang River basin.The results showed that the main drivers of biocapacity change in shiyang River basin and its contribution at different spatial scales were of obvious heterogeneity,indicating obvious scale effect,and the finer the scale,the bigger difference the drivers.①At the basin-scale,the number of the most important driving forces was 11,and the number of more important driving forces was 7.the top three most important driving forces were runoff,precipitation and annual accumulated temperature in Shiyang River basin,and the contribution rates were 37.02%,36.32%and 25.07%,respectively,which exerted positive effects on biocapacity changes.while the contribution of primary industry share,natural growth rate of population and rural population had negative effects,and the contribution rates were-16.38%、-14.01%and-12.32%,respectively.②At the county-scale,the main important driving forces and its contribution rates of biocapacity were different.County-scale driving forces were sorted by contribution rates in absolute terms,that is,the main driving forces of biocapacity.For instance,precipitation,secondary industry share,primary industry share,above high school education population proportion,relative humidity and reclamation rate were the main driving forces in Liangzhou district;precipitation,annual accumulated temperature,average temperature,per capita arable land and water supply quantity of sensitive ecological index were the main driving forces in Minqin county;reclamation,effective irrigation area,per capita GDP,tertiary industry share,meat production volume,per capita arable land and precipitation were the main driving forces in Gulang County;tertiary industry share,above high school education population proportion,per capita arable land,precipitation and population density were the main driving forces in Tianzhu County;precipitation,per capita arable land and population density were the main driving forces in Yongchang County;Engel coefficient of rural family,meat productio,tertiary industry share and precipitation were the main driving forces in Jinchuan District;precipitation,average temperature,above high school education population proportion and natural growth rate of population were the main driving forces in Sunan County.While precipitation was the common driving factor in almost every country,which indicated that the mainly restriction factors of ecological environmental change in arid areas was precipitation.③At the township-scale,the main driving forcesof biocapacity were also different in each administrative town,and the gap between regions was much larger,township-scale driving forces were sorted by contribution rates in absolute terms,that is,the main driving forces of biocapacity.Reclamation,precipitation,Annual accumulated temperature and net income per capita were the main driving forces in Jinta township;average temperature,precipitation,annual accumulated temperature and above high school education population proportion were the main driving forces in Xuebai township,tertiary industry share,reclamation and secondary industry share were the main driving forces in Dajing town,above high school education population proportion and meat production volume were the main driving forces in Qilian township;population density,natural growth rate of population,average temperature and relative humidityp were the main driving forces in Jiaojiahzuang township,natural growth rate of population,the population of rural residents,net income per capita and population density were the main driving forces in Ningyuanbao town,irrigation area;effective irrigation area,average temperature and annual accumulated temperature were the main driving forces in Huangcheng town.3.Simulation and prediction of biocapacityBy choosing the biocapacity of spatial data in 1992,2002 and 2012,and setting 10 years as the step size of simulation,this paper assumed that in the following 10 years,the Grain for Green policy and the land-use trends of past 10 years in Shiyang River Basin would continue to be preserved,the spatial pattern of biocapacity in 2022 was predicted.The result showed that the total biocapacity in 2022 in shiyang River basin would increase 87729.84gha compared to 2012,of which the biocapacity of building-up land increase most significantly,contributing an increase by 52031.99gha,biocapacity of cropland,forest land and fishing land would also increase by 6259.97gha,35402.93gha and 2633.Olgha,respectively.While the biocapacity of cropland and grassland biocapacity would reduce by 8598.06gha.The distribution pattern of the absolute value of biocapacity in 2022 would have no great change,but there was some change in some regions,such as in the upper reaches,the area with low value of absolute value of biocapacity would reduce by 635.86km2,on the contrary,areas with high value would increase by 465.44km2.According to the conclusions of this study,this paper put forward appropriate countermeasures and suggestions,which can provide scientific bases for the management of Shiyang River’s econogical environment and the constitution of forward-looking policies of sustainable development.Therefore,it is of great practical significance for gradually restoring and improving ecological environment in Shiyang River basin. |
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