The Investigation Of Grassland Degradation And Analysis About Degradation Reason In Dari County Of Qinghai Province

Grassland degradation is a world problem. This report is about the remote sensing investigation of the grassland in Dan County of Qinghai province, and the reason of grassland degradation is analyzed. In the report, 3S technologies are used; they are remote sensing, GIS and GPS. Many domestic and foreign scholars have made a great deal of researches about using NDVI of American meteorological satellite NOAAJAVHRR and LANDSAT TM image to monitor the grassland, have proved it is efficient, precious and inexpensive to use this method to investigation grassland vegetation. Degraded grassland investigation in Dan County mainly used remote sensing technology, combined GIS with field sample technology. The history information (husbandry plan report, grassland type map, grassland gradation map and seasonal grassland map in 1985, topographic map etc.) and information in 1997 (NOAA~. TM and measured yield datum in field) are also used. After image processing and complex evaluation, calculated taking the township as unit, and provide the information and maps about landusing (total area, shrub, grassland, usable grassland, bare-land and rock), grassland gradation, yield, stocking rate (theoretic stocking rate, winter-spring and summer-autumn stocking rate) and seasonal yield change. In this report, mainly using NOAA data once in per half-month in April 15th ? October 15th of 1997, calculated out the NDVI of all images, then taking the statistic calculation with the grass yield measured in the field in the same place and same time, get out the logarithm equation:Y249.l37*LgX ?347.2 13 (correlative coefficient r is 0.823), X stand for the NDVI and V stand for the grass 3 yield in this equation. The investigation indicate that total usable grassland area is 10 793.36 km2 in Dan county in 1997, including fifth gradation grassland 5 203.379 km2 and sixth gradation grassland 5 590.283 km2 , respectively occurring 48.30% and 51.70% of usable grassland. Theoretic grass yield, usable herbage and intake total figure are 345.4537 (10 000 ton), 278.7811 (10 000 on) and 139.3906 (10 000 ton). Theoretic stocking rate, winter-spring stocking rate and summer-autumn stocking rate respectively is 100.24, 87.25 and 125.2 (10 000 SU). By comparing two grassland husbandry resource investigation results in 1985 and 1997, may get out such conclusion: usable grassland area have reduced, bare- grassland area have increased; In usable grassland, hig~i gradation grassland rate have decreased, low gradation grassland rate have increased; grassland herbage yield and stocking rate have decreased. The reasons of grassland degradation include human and natural two sides. The theoretic stocking rate of Dan county decreased to 100.24 (10 000 SU) in 1997 from 172.43 (10 000 SU) in 1985, actual stocking rate become 120.90 (10 000 SU) in 1997 from 125.76 (10 000 SU) in 1985, so grassland is overgrazing in Dan county. The research also indicates that the severely dry climate in the middle of Asia have deeply influenced the grassland in Dan county. Overgrazing is the main reason of grassland degradation in Dan County; desertification caused by high temperature in the globe also is the important reason of grassland degradation, forming many bare-grassland in Dan County, which located in semi-arid and semi-humid arid region. But the reasonable grazing...