Vegetation Change Under Different Stocking Rate In Desert Steppe Based On 3S Technology

In this paper, dynamic monitoring of the vegetation coverage is carried out for the grazing region of different stocking rates from 2002 to 2014 in dimidiate pixel model with the Stipa breviflora desert steppe experimental base, Siziwang Banner, of Inner Mongolia Academy of Agricultural & Animal Husbandry Sciences in Ulan Qab as the research area, based on the ALOS and LANDSAT multi-source remote sensing satellite data and ground survey data. Relationship between the spatial and temporal distribution characteristics of vegetation coverage and different stocking rates and annual dynamic changes and the weather, stocking rate and the spatial and temporal distribution of grazing of livestock is studied based on the meteorological data and GPS location tracking data, with various means, such as the spatial analysis of geographic information system, mathematical statistics analysis method, etc. for revealing the impact of stocking rate and meteorological factors on the vegetation coverage. This research can provide a theoretical basis for the sustainable management of grasslands.There are four stocking rates in study area, including 0.91sheep/hm2·half year in lightly grazed area,1.82 sheep/hm2·half year in moderately grazed area,2.71 sheep/ hm2·half year in heavily grazed area, and 0 sheep/hm2·year in control area.In August 2010, the ground data of 120 vegetation samples in the test area was collected, including the geographic coordinate and vegetation coverage; from 2010 to 2011, the livestock location tracking data was collected six days per month in the grazing season, for acquiring the frequentness of sheep in different terrains and vegetation coverage distribution. Meanwhile, the topographic survey of the test area was carried out at the proportion of 1:1000 in August 2011. The main research results are shown as below:1. In the grazing test from 2004 to 2014, with the increase of stocking rate, there were significant differences in the vegetation coverage in different stocking rates, and the vegetation coverage decreases in the sequence:control plot> slightly grazing plot> moderately grazing plot> heavily grazing plot. In 2014, the vegetation coverage of the control plot and slightly grazing plot was evidently higher than that in 2002 before the test, suggesting that enclosure and moderate grazing are effective management measures for improving the vegetation coverage in grasslands. The vegetation coverage of the moderately grazing plot and heavily grazing plot was evidently lower than that in the control plot and slightly grazing plot, but higher than that in 2002 before the test, suggesting that the rest grazing in winter and spring will reduce the impact of moderately and heavily grazing on the vegetation coverage.2. Precipitation is the primary climatic factors impacting the vegetation changes, and it is in a significant correlation with the positive dynamic change rate of vegetation at 0.01 level. Although the temperature is in correlation with the dynamic rate of vegetation coverage, only the temperature in July and August is in significant correlation with the positive dynamic rate of vegetation coverage in the moderately grazing plot and heavily grazing plot at 0.05 level, suggesting that the impact of precipitation on the vegetation growth in desert steppe is higher than that of temperature. The correlation of different precipitation amount shows that precipitation in spring and summer is in the strongest correlation with the positive change rate of the vegetation coverage (p<0.01), and then, it shall be the annual precipitation and summer precipitation. Meanwhile, the correlation between the precipitation and grazing plot is higher than that of the control plot, suggesting that the spring and summer precipitation is the primary factor impacting the vegetation growth in the desert steppe grazing plot.3. Livestock grazing distribution characteristic and stocking rate are important factors that may cause the changes of vegetation coverage. The adaptive grazing habit of livestock in grasslands and high stocking rate may lower the vegetation coverage in the moderately grazing plot and heavily grazing plot. In the grazing test period, the vegetation coverage of slightly grazing plot increased evidently. Therefore, it is considered that 0.91 sheep//hm2 half year of stocking rate shall be the most appropriate stocking rate for the recovering of vegetation coverage in the desert steppe.