Remotely Sensed Monitoring And Classification Management Of Grassland In The Gannan Region, China

The Gannan region is located on the northeast of Qinghai-Tibet Plateau, rich in grassland resources but had the severe climatic conditons and the ecological environment is very fragile. In the past decades, natural (climate change) and human factors (overgrazing and deterioration of natural environment) resulting in the degradation of 90% of grasslands in this region. Effective and accurate monitoring of the grassland vegetation changes will not only plays an important role in grassland animal husbandry and sustainable development of social economy and, but also has great significance to the construction of regional ecological environment.This research compared the correlation between 17 vegetation indices and grassland biomass, and found out the suitable VI to monitoring Gannan grassland change. The best VI was used to establish the Gannan grassland biomass/cover monitoring models. The VI and grassland biomass spatial-temporal variation were analyzed. The grassland resilience characteristics and the grassland classification management method were studied. Main conclusions obtained as follows:(1) The linear regression analysis between field survey data and MODIS data showed that the EVI was the best index to simulate the forage dry biomass and cover in the Gannan region from 17 vegetation indices (Ⅵs) evaluated. The results of precision estimation for models showed that the grassland biomass estimated model was:y=3738.073x1.553 (R2=0.626), grassland cover estimated model was:y=101.664+42.3861n(x) (R2=0.449).(2) The EVI monthly and yearly variation showed that:the EVI value increased from April to July during 2001 to 2009 and got the maximum at July except 2001, then the EVI value decreased. Maqu and Luqu had relatively higher EVI value and Zhouqu had the EVI minimum. The variation of EVI during 9 years was more obvious in Lintan, Xiahe, Zhouqu. The EVI increased obviously in Lintan, Xiahe, Zhouqu, Zhouni from 2001 to 2009.(3) The grassland biomass increased slightly from 2001 to 2009. The grassland biomass monthly variation was the single-peak parabola distribution and matched to grassland growth rule. The grassland biomass of warm temperate tussock, temperate steppe increased obviously from 2001 to 2009 (R2=0.529, sig=0.026; R2=0.423, sig=0.058).(4)The grassland with the lowest resilience accounted for 33.84% of the available grassland from 2001 to 2009. These grasslands mainly located in Zhuoni, Diebu and Lintai counties. The grassland with lower resilience mainly located in the northern of Xiahe county and accounted for 15.35% of available grassland in Gannan. Grassland with the highest and higer resilience mainly located in Maqu, Luqu and Xiahe, and accounted for 19.66% and 31.15%, respectively. The resilience of Zhuoni and Diebu counties were lower than other counties. Maqu and Luqu counties had the highest resilience. The grassland in Gannan had the highest resilience in summer and had the relatively stable condition in winter and spring. In fall, the grassland resilience was obviously decreased.(5)The index of classification management of grassland (ICG) was used to subdivide grassland into conservation grassland and moderately productive grassland in the Gannan region where no grassland fell into intensively productive grassland. The moderately productive grassland was the main grassland type in Gannan. Most conservation grassland located in Xiahe, Maqu, Diebu and Zhouqu and the area of conservation grassland in Xiahe was the largest. The area of conservation grassland is 3.45×104ha, accounted for 1.35% of the available grassland while the area of moderately productive grassland is 252.2×104ha accounted for 98.65% of the available grassland. Different management techniques should be applied to conservation, moderately and intensive productive grassland. Although the grassland in conservation sector could not provide the income for resident farmers, these losses can be compensated by the increase income of intensively productive grassland. In this study, grasslands divided into conservation sector can be mainly devoted to ecological and social values in the future. Anti-grazing and fencing had been suggested to restore degraded grasslands in the Gannan regions. The moderately productive grassland was suggested to carry out reasonable carrying capacity and rotational grazing by grazing in the summer and autumn and shelter feeding in winter and spring to achieve the balance between livestock need and forage supply.