Wei Yaxing

Grassland classification and evaluation of grazing capacity in Naqu Prefecture, Tibet Autonomous Region, China

Abstract Grassland animal husbandry is an important component of the regional economy in Naqu Prefecture of Tibet. A grassland survey was initiated to specify biological and socio‐economic characteristics of animal husbandry. The information from the survey was used to classify grassland resources and to evaluate grazing capacity. Based on the China Grassland Classification System, the grasslands in Naqu Prefecture were classified into 4 classes, 10 groups, and 32 types. The assessment of grazing capacity indicated that the grasslands in the eastern counties of the temperate wet zone and some counties in the central and western parts are severely overgrazed, which has resulted in serious grassland deterioration. Clarifying the ownership of the grazing lands should be the top priority for the government if a policy of sustainable development of grassland animal husbandry in Naqu Prefecture is to be adopted.

Simulating Alpine Vegetation Net Primary Productivity by Remote Sensing in Qinghai Province, China

Primary productivity of ecosystem is important indicator about ecological assessment. Remote sensing technology has been used to monitor net primary productivity (NPP) of ecological system for several years. In this paper, the remotely sensed NPP simulation model of alpine vegetation in Qinghai Province of Tibet Plateau was set up based on the theory of light use efficiency. Firstly a new approach based on mixed pixels and Support Vector Machine (SVM) algorithm were used to correct simulated NPP values derived from Moderate Resolution Imaging Spectroradiometer (MODIS) data. Finally, spatial distribution and monthly variation characteristics of NPP in Qinghai Province in 2006 were analyzed in detail. The result showed that NPP of vegetation in Qinghai Province in 2006 ranged from 0 to 422 gC/m2/a and the average NPP was 151 gC/m2/a. NPP gradually increased from northwest to southeast. NPP of different vegetation types were obviously different. The average NPP of broad-leaved forest was the largest (314 gC/m2/a), and sparse shrub was the smallest (101 gC/m2/a). NPP in Qinghai Province significantly changed with seasonal variation. The accumulation of NPP was primarily in the period (from April to September) with better moist and heat conditions. In July, the average NPP of vegetation reached the maximum value (43 gC/m2). In our model, the advantage of traditional LUE models was adopted, and our study fully considered typical characteristics of alpine vegetation light use efficiency and environmental factors in the study area. Alpine vegetation is the most important ecological resource of Tibet Plateau, exactly monitoring its NPP value by remote sensing is an effective protection measure.