Study On Grassland Biomass By Gridding Approach

Since the 20th century,the global grassland has irreversible destroyed by overusing.In this situation,the grassland ecosystem is damaged,the acreage of grassland is decreased,and the yield of grass is reduced,it has become a shortcoming of the sustainable development of grassland animal husbandry.At present,spatial analysis based on the management of gridding approach,has gradually grown into an essential technology in the field of resource management,and plays a decisive role in optimal allocation of natural resources.As one of the key pastoral areas in north China,Altay region of Xinjiang is rich in grassland resources.However,the irrational use of grassland cause the degradation of grassland and the decline of grassland productivity,and seriously inhibit the sustainable use of grassland resources and the improvement of people’s living in Altay region.Therefore,the natural grassland of 2015 in Altay region of Xinjiang is selected as a study area in this research.The spatial pattern of grassland biomass is obtained and analyzed by gridding approach of multivariate data in this study area,based on empirical means and remote sensing methods.The multivariate data include field survey data of grassland biomass,climate data（temperature,precipitation,humidity,etc.）,remote sensing data（NDVI）and surface data（DEM,grassland type,soil type）.This study aims to comprehensively understand the spatial pattern of grassland biomass in Altay region,and provides technical and theoretical references in grassland degradation and sustainable management of grassland in other regions.The main results are as follows:（1）In Altay region,the total biomass of grassland is between 835.51⁴387.24g·m^-2,the aboveground biomass is 62.17²26.97 g·m^-2,the belowground biomass is645.95⁴078.21 g·m^-2.Furthermore,the grassland belowgroumd biomass is 308.17²552.67 g·m^-2 in the soil layer of 0¹0 cm,157.97¹097.41 g·m^-2 in the soil layer of10²0 cm,67.41⁵28.20 g·m^-2 in the soil layer of 20³0 cm.The spatial pattern of grassland aboveground biomass,belowground biomass and total biomass is similar,declining from north to south,and decreasing from mountain to plain in a vertical gradient;The aboveground biomass of the natural grassland in this study area accounts for 6.09%of the total grassland biomass,the belowground biomass accounts for 93.91%;There are types of grassland in this region,and the grassland biomass of them are varies,but the distribution ratio of aboveground biomass and belowground biomass is basically the same.（2）In Altay region,the correlation coefficient ranges from 0.35 to 0.75,between altitude,annual mean temperature,≥10°C annual accumulated temperature,annual mean precipitation,humidity,NDVI and grassland biomass.In addition,NDVI and grassland aboveground biomass has significant correlation（P<0.05）.The total grassland biomass,aboveground biomass,belowground biomass and layered belowground biomass（0¹0cm,10²0cm,20³0cm）are extremely significant correlated with other environmental factors（P<0.01）.（3）The quadratic function model is suitable for describing the correlation between altitude,annual mean temperature,annual mean precipitation,humidity and grassland biomass index;Both quadratic and logarithmic models can be used to describe the correlation between≥10°C annual accumulated temperature and grassland biomass;the power function is the best fitting function of NDVI and grassland biomass.（4）The results of grassland biomass can objectively reflect the spatial pattern and gradient change of natural grassland biomass in Altay region by gridding approach.The gridding accuracy of total grassland biomass,aboveground biomass,and belowground biomass are 69.59%,50.48%and 65.32%.The gridding accuracy of layered grassland belowground biomass（0¹0cm,10²0cm,20³0cm）are 62.75%,61.37%and 56.48%.