Effect Of Enclosure On Soil Characteristics And Organic Carbon Of Alpine Meadow In Three-river Headwater Region

Alpine meadow in Three-river Headwater region is considered as an importanteco-function area, and a large carbon reservoir effect. In order to explore thedistribution characteristics of soil organic carbon, as well as in the implementation ofThree-river Headwater of ecological engineering, the distribution patterns andstability of soil organic carbon storage of alpine meadow in the Three-riverheadwater region and the effect of fencing duration were studied in in2007,2010and2013. And34sampling plots were selected and soil moisture content, bulk density, pHvalue, soil organic carbon, microbial biomass carbon, ammonium nitrogen and nitratenitrogen were measured. The main results are as follows.1. Fencing improved the content soil organic carbon in alpine meadow and with theextension of fencing time, the increase of organic carbon showed a rapid patternin early period and tnen kept stable. Soil organic carbon between soil anddecreases with the increase in depth. The soil organic carbon content showed anorder of6years>9years>3years based on enclosure duration. With the increaseof soil depth, soil organic carbon content decreased, soil organic carbon contentof10-20cm was1.76%in fencing3years, and this was lower than that at20-40cm (1.93%). The soil organic carbon content reached the highest (5.12%) under6year-fencing treatment. It was4.16%under9year-fencing treatment. The soilorganic carbon content positively correlated with aboveground biomass,underground biomass and soil moisture.2. Along with the extended period of fencing, biomass increased gradually, fencingincreased by3years to6years is remarkable, from the enclosure6years to9years, the increase wa not significant. There were significant differences betweenaboveground and underground biomass (p<0.01). Fencing3years of alpinemeadows, aboveground biomass of plant communities was ranged from0.12kgm-2to0.63kg m-2; and belowground biomass was significantly higher than the aboveground biomass, around10times the aboveground biomass. Fencing6years meadow, a sharp increase in aboveground biomass of plant communitiesand belowground biomass, were significantly higher than the productivity ofgrassland fencing3years. Aboveground biomass and belowground biomass onthe ground slowly increased slightly in9years-fencing meadow, but significantlyhigher than that for3years enclosure.3. With the extension of fencing time, the soil nitrate content increased at a differentdegree. The increasing range was larger from3years enclosure to6years, andsmaller from6years to9years. Soil nitrate content of3years fencing plots0-10cm were ranged from0.76to4.85g/kg. With the increase of soil depth, thenitrate content decreased. For fencing3years, with the increase of soil depth, theammonium nitrogen content decreased. With the increase of soil depth, soilammonium nitrogen content decreased. Soil ammonium nitrogen, mainlybetween0.62to3.92g/kg in6years fencing plots in0-10cm layer, with theincrease of soil depth, the ammonium nitrogen content decreased. The soilmoisture was significantly increased with the enclosure duration and the orderwas3years <6years <9years. The soil pH value for fencing3years,6yearsand9years were7.24,7.20and7.20respectively. The soil bulk density washigher for fencing3years, and it was followed by duration of6years and9years.4. Soil microbial biomass carbon content of different fencing durations were rangedfrom0.03to2.82g/kg. And it increased along with the enclosure duration. Theorder was3years <6years <9years.