Spatio-Temporal Distribution And Influencing Factors Of Grassland Net Primary Productivity And Grazing Livestocks Of Typical Pastoral Area In Northwest Sichuan

Rangeland resources and grazing livestocks are the substantial materials for the development of animal husbandry in the northwestern Sichuan province.Yaks and Tibetan sheep of the local unique animal breeds,whose population,grazing intensity,and population structure directly affect the health of grassland.It is an important scientific proposition to coordinate the relationship between livestock economic development and grassland protection.Firstly,the spatial distribution patterns of grazing livestocks and grassland net primary productivity were established using the the grassland NPP from 2006 to 2016 was estimated by CASA model and the livestock population,grazing intensity,proportion of female livestock in 2016,which were based on the grassland productivity and grazing livestocks about five typical pastoral area including Aba,Zoige,Hongyuan,Rangtang and Songpan in the northwestern Sichuan,and then the factors for the spatial distribution differences of grazing livestock and grassland NPP were analyzed.Finally,based on the spatial distribution of herd structure and the grazing livestock population in northwest Sichuan.We performed comprehensive analyses on the livestock population characteristics,composition of herdsman families,and management indices of livestock slaughtering in August 2018 in four typical animal husbandry area of northwest Sichuan,including Zoige,Hongyuan,Aba,and Rangtang,based on 20townships and 124 pastoral.The main results are as follows:1.Spatio-temporal variation analysis of grassland NPP and its influencing factors in typical pastoral area of northwestern Sichuan from 2006 to 2016The spatial distribution of NPP in typical pastoral areas in northwest Sichuan from 2006 to 2016 showed obvious heterogeneity,presenting a state of high north and low south.The average annual value was 470.46g C·m^-2·a^-1,which of larger than500g C·m^-2·a^-1was mainly distributed in the middle areas of five typical animal husbandry counties,including the east of Zoige County and Hongyuan County,and the northeast of Aba County and Rangtang County.The annual fluctuation range is428.25～515.88g C·m^-2·a^-1,and the overall variation is relatively stable.Hydrothermal conditions are closely related to the distribution of grassland NPP.In typical pastoral areas in northwest Sichuan,grassland NPP is mostly positively correlated with average annual temperature,and its correlation with rainfall has obvious zonal characteristics.The area with negative correlation accounts for 50.77%,which was mainly located in the west of Rantang County and Aba County,and the positive correlation areas are mainly distributed in the east of Zoige and Songpan.In addition,the increase of population and livestock also has a negative effect on the increase of NPP.2.Spatial distribution characteristics of livestock population and structure of typical pastoral area in northwestern Sichuan province in 2016The livestock population of Zoige and Hongyuan counties enjoyed the highest proportion in the typical pastoral area of northwestern Sichuan with a decreasing tendency from north to south,In the west of Zoige county,the total stock of yaks and sheep was the largest.However,the number of yaks and sheep in Yantang and Songpan counties was relatively small.The correlation between livestock population and grazing intensity was not obvious in space.The grazing intensity was higher mainly in Zoige and Aba counties,and the Waerma Town of Aba County had the largest grazing intensity,with a value of 8.55 sheep/hm2（0.57 sheep/area）,followed by Rangtang and Hongyuan counties,whereas Songpan County had the lowest grazing intensity.In terms of the livestock breed structure,the sheep of the northern parts of Zoige County accounted for the highest proportion in typical pastoral area,while Yak was mainly distributed in most parts of Hongyuan County,the northeast parts of Aba County,and the southern parts of Zoige County.Regarding the livestock population restructuring,the counties with the highest average ratio of female yak and sheep were Hongyuan and Rangtang with an average value above 62.5%.3.Analysis of factors affecting the livestock spatial distribution difference of typical pastoral area in the northwest Sichuan provincePopulation was the dominant influencing factor for the spatial distribution of the total grazing livestock and yaks in the northwest Sichuan province（explanatory power:0.48 and 0.45,respectively）,followed by the average annual temperature and grassland area.Instead,the vegetation coverage exerted the weakest influence on the spatial distribution of the total grazing livestock,yaks,and sheep.While the vegetation type exerted a relatively strong influence on the spatial distribution of yaks,the impact on the distribution of the total grazing livestock and sheep was relatively light.Rainfall and temperature were the primary factors restricting the spatial distribution of sheep in the northwest Sichuan province（explanatory power:0.30 and0.29,respectively）,followed by population and slaughter rate（explanatory power:0.22 and 0.17,respectively）.Finally,influencing factors enhanced each other when they interactively influenced the grazing livestock distribution in the Northwest Sichuan province.4.Analysis of influencing factors on structure management of livestock in typical pastoral areas in Northwest SichuanExcluding Zoige county,sheep were the main livestock in the typical pastoral area.The highest reproducing ratio of female yaks and sheep in Rangtang county was66.63%and 68.26%,respectively,while the lowest in Zoige county was 48.23%and51.67%,respectively.In terms of the reproduction rate,the highest reproduction rates of yaks and sheep in Zoige county were 46.04%and 63.26%,respectively,whilst in Rangtang county they were 35.51%and 63.67%.On the contrary,the lowest reproduction rates of yak and sheep in Aba and Hongyuan county,with 31.6%,46.21%and 40.07%,43.30%respectively.Men aged from 32 to 38 years old were the main herding labor force in a typical animal husbandry county,and their degree of education was generally low.The largest ratios of illiteracy and primary school education were 31.29%and 46.51%,respectively,while the lowest ratio of college education,junior college,or above was 4.96%.In terms of the management of livestock slaughter,the slaughter time of sheep in Aba county was more than 1 year,which is within a reasonable range.However,the slaughter time of yaks and sheep in other counties is relatively long,the slaughter rate is relatively low,and the largest slaughter rate was only 21.08%in Hongyuan county.