Range Site Division And Range Health Assessment In Xilin River Watershed

The range site classification and its creterion were discussed in order to manage rangeland resources rationally. Based on the quantative change of vegetation and soil characteristics under different grazing intensities the assessment system of range health and the dada base of rangeland resources information were established. The main results are as follows:(l) The approach of range site classification and naming is made with topography, soil genus, and vegetation association, and there are nine range sites in Xilin River Watershed, including middle hill-sandy loam carbonate chernozem soil Filifolium sibiricum, Stipa grandis, and xero forbs range site, middle hill thick chernozem soil Leymus chinensis, forbs range site, lowland sandy soil Stipa grandis xero forbs range site, plain thick black chestnut soil Leymus chinesis range site, slight slope chestnut soil Stipa grandis range site, plain sandy chestnut soil Stipa grandis range site, flood land humus wamp soil Carex range site, south slope tight sand soil Prunus sibiricus, Hedysarum gmelinii range site, north slope tight sand soil Prunus padus, Spiraea aquailegifolia range site, and interhills lowland sandy chestnut soil Stipa grandis, Cleistogenes squarrosa range site. The characteristics of vegetation, soil and topograpgy in each range site was described.The height, coverage and yield of dominant species decreased as grazing intensity increased. The distribution pattern of same species in different range sites varied with the change of grazing intensity. Plant a and P biodiversity declined with the increase of grazing intensity. The effect of grazing intensity on plant photosynthesis is complex, and the daily change of photosynthetic rate of Leymus chinensis and Stipa grandis showed the single peak curve. The height, coverage and yield of plant community showed the declined trend with the increase of grazing intensity. The soil organic matter, total nitrogen, total phosphorus, and available nutrients decreased as grazing intensity increased. Soil pH value and electric conductivity had no obvious change with the grazing intensity. The total number of soil microorganism, soil moisture and siol respiration rate reduced as grazing intensity increased and bulk density and compaction increased as grazing intensity increased.Plant community coverage, aboveground biomass, plant species number, soil bulk density, soil water content, organic matter, total nitrogen, total phosphorus, NO3-N, NH4-N, available phosphorus, potassium, total number of microorganism and soil respiration rate can be used as the indications of range health assessment. Therefore, the degradation gradients in Xilin River Watershed can be divided into 3 different health levels according to the comprehensive range health indice, i.e. health, range health index 0.85-1; subhealth, range health index 0.65-0.85; non health, range health index 0-0.65.The database of rangeland information in Xilin River Watershed wasestablished, which will benefit to the information management of rangeland in this area.