| Grassland as one of the most widely cover of the earth's surface vegetation types,with a huge area and the distribution of carbon sequestration potential of carbon assessment plays an important role in the global system.The Mongolia plateau is located in the middle of the Eurasian,Siting in arid and semi-arid climate zone,the topography in the west is high and in the east is low.Grassland types are including meadow steppe,typical steppe and desert grassland,etc.Along with the population growth and economic development during the last half century,substantial LUCC has occurred over Mongolia plateau mainly due to over-grazing and over-cultivation.These changes caused ecological problems such as degradations of grassland and cropland,desertification and changes in carbon dynamics.The importance of grassland degradation condition monitoring can not be ignored.As the economic development of "One Belt And One Road",strengthening the neighboring diplomatic relations has important significance.This study used remote senscing data,vegetation typedata,meteorological data to calculate vegetation coverage,surface bareness and NPP.Then analyzed the different time and space scales vegetation index dynamic change,and the influence of climate factors;On the other hand,the degree of degradation and its spatial distribution are determined by using the coverage of grassland degenerate remote sensing monitoring.The main work and conclusions of this study are as follows:(1)The spatial and temporal distribution of grassland coverage and the response to meteorological factors.Based on GIMMS-NDVI and MODIS-NDVI data inversion of the Mongolian plateau area 1986-1999 and 2000-2013,analysis the spatial pattern of vegetation coverage and change trend from different time and space scales,and analyzes its response to climate change.In 1986-1999 and 2000-2013,the Mongolian plateau grassland coverage were 14.60%and 18.43%respectively,the grass coverage as a whole was on the rise,the annual area of grassland coverage significantly and extreme significantly increased in 1986-1999 298.86 km2 and 189.67 km2,accounting for 11.64%of the total area.The 2000-2013 values were 443.32 km2 and 92.46 km2,accounting for 10.59%of the total area.In annual level.Mongolia plateau grassland vegetation growth on the whole has close relationship with precipitation,and on the month level,the rainfall and temperature on the influence of vegetation growth,vegetation growth more dependent on the combination of water and temperature,the function of factors associated with a single climate,vegetation coverage and month response lag effect of rainfall.(2)The time and space dynamic distribution of the surface bareness of Mongolian plateau and its correlation analysis with climate factors.We chose the red light and thermal infrared data of MODIS products,using Fb model inversion the surface bare degree of the Mongolia Plateau in 2000-2013.The annual average and spring,summer and autumn analysis bare degree of spatial pattern and the change trend;Combined with the rainfall and temperature data in this region and this time scale,the inter annual variation of surface bareness was analyzed and the correlation of meteorological factors was analyzed,too.Bareness degree generally exposed increasing from northeast to southwest and west,the values of the 14 years plateau surface exposed degree average was of 26.04%,spring,summer and autumn plateau surface exposed degree average were of 23.9%,20.65%and 27.24%respectively;The overall level of bareness was decreased,and the rate of reduction is approximately-0.0008/14a.The correlation between bareness degree and average annual precipitation and temperature were of 0.08 and 0.04,respectively,bare degree is slightly higher than the negative correlation with precipitation and temperature of negative correlation,overall,the difference is not obvious.(3)The temporal dynamic distribution of NPP and its correlation analysis with climate factor.Based on the CASA model,the NPP of the Mongolian plateau simulated from 1986 to 2008,and its response to climate factors analyzed.The average level of net primary productivity of the Mongolian plateau in 1986-1999 and 2001-2008 were 290.1 gCm-2yr-1 and 287.2 gCm-2yr-1,which showed the declining distribution characteristics of northeast to southwest.The plateau NPP generally presents a trend of decreasing in the first place,with a reduction in 1986-1999 and 2000-2008 with an average of-0.24/14yr and 0.37/9yr,respectively.Plateau climate in the past few decade rainfall reduced,the temperature is rising trend,appeared dry phenomenon,precipitation and temperature two meteorological factors on the effect of vegetation NPP.(4)The remote sensing monitoring of grassland degradation of Mongolian plateau based on grassland degradation index used.In order to achieve the large remote sensing quantitative assessment of grassland degradation conditionin the Mongolian plateau,we used vegetation coverage from 1982 to 1985 as benchmark data(No degradation).The largest percentage of serious degraded grassland area in 1986-1999 was 50.35%.Moderate and severe degraded grassland area in 2000-2013 percent of close to 70%,the values were 39.42%and 30.34%,respectively.Grassland degradation condition was a better trend.From extreme serious,serious to moderate degradation conditions.The innovation of this study includes the following twoparts:firstly,this research chose body part of the Mongolia plateau(Inner Mongolia and Mongolia),contrastive analysis in both vegetation under the different regimes,to analyses meteorological factors correlation with degradation;choosing of index,time and space scale analysis.This study put grassland as the research focus,used grassland coverage,bareness degree and NPP,to analysis the different indicators in different time and space scales in Mongolia and Inner Mongolia.Secondly,put grassland vegetation coverage in 1982 to 1985 of as benchmark data,based on the quantitative evaluation of grassland degradation degree,the base and condition assessment of grassland degradation degree. |
PDF Full Text Request