EFFECT OF LAND-USE ON SOIL NUTRIENTS AND MICROBIAL BIOMASS OF AN ALPINE REGION ON THE NORTHEASTERN TIBETAN PLATEAU, CHINA

Land-use patterns affect the quantity and quality of soil nutrients as well as microbial biomass and respiration in soil. However, few studies have been done to assess the influence of land-use on soil and microbial characteristics of the alpine region on the northeastern Tibetan plateau. In order to understand the effect of land-use management, we examined the chemical properties and microbial biomass of soils under three land-use types including natural grassland, crop-field (50 + y of biennial cropping and fallow) and abandoned old-field (10 y) in the area. The results showed that the losses of soil organic carbon (SOC) and total nitrogen (TN) were about 45 and 43 per cent, respectively, due to cultivation for more than 50 y comparing with natural grassland. Because of the abandonment of cultivation for about a decade. SOC and TN were increased by 27 and 23 per cent, respectively, in comparison with the crop field. Microbial carbon (ranging from 357.5 to 761.6 mg kg(-1) soil) in the old-field was intermediate between the crop field and grassland. Microbial nitrogen (ranging from 29.9 to 106-7 mg kg I soil) and respiration (ranging from 60.4 to 96.4 mg CO2-C g(-1)C(mic) d(-1)) were not significantly lower in the old-field than those in the grassland. Thus it could be concluded that cultivation decreased the organic matter and microbial biomass in soils, while the adoption of abandonment has achieved some targets of grassland restoration in the alpine region of Gansu Province on the northeastern Tibetan plateau. Copyright 2010 John Wiley & Sons, Ltd.