Dynamic Study Of Characteristics And Decomposition Of Standing Dead And Litter In Stipa Grandis Community

Stipa grandis steppe is one of the typical tussock-grass steppe in mid-east region of Eurasian grasslands. It is also the most representative typical steppe in Mongolia plateau. Alternate growing season and non-growing season makes the above-ground parts distinguish as growth period and senesces period. Standing dead and litter are not only one of the structural components of grassland ecosystem, but also the main source of forage for herd in non-growing season. This research investigates the dynamics of litter characteristics and decomposition under grazing and fencing activities at43million mu of Mao Deng pasturage of Xilin Gol League. Results indicated that:1. The standing dead and litter of S. grandis community was divided into bunch grasses, dwarf grasses, tumbleweed and forbs, species composition of the standing dead in S. grandis community changed obviously with the seasons. From growing season to non-growing season, tumbleweed and Allium species of forbs were lost rapidly due to their own characteristics and environmental conditions (wind, snow). Important value about standing dead of S. grandis was the highest, followed by Leymus chinensis of the community in S. grandis steppe. On the other hand, bunch grasses which have relative stronger wind and storm resistant capabilities was easier reserved, and become a major component of community in the non-growing season;2. Species number about standing dead of community was lower in grazing S. grandis community than in fencing S. grandis community, and grazing led to higher important value of S. grandis; 3. From August of that year to August of the following year, as the season goes on the density, height about standing dead of the S. grandis community performanced first increased and reached its maximum in October of that year,then decreased gradually to August of the following year have increased. Maximum mass about standing dead and litter appeared in October of that year. The density, height and mass of standing dead and litter was significantly lower in grazing S. grandis community compared to fencing S. grandis community in different times.4. Organic carbon storage reached to maximum in October, organic carbon reserved by standing dead and litter in fencing plot were0.46t·hm-2and0.37t·hm-2respectively in this time, in grazing plot were0.07t·hm-2and0.15t·hm-2respectively in this time, and the organic carbon storage was significantly lower in grazing S. grandis community compared to fencing S. grandis community;5. Decomposition rate of litter was higher than that of standing dead in both fencing and grazing S. grandis community, and decomposition rate of standing dead and litter of S. grandis and communities were faster in grazing grazing S. grandis community than in fencing grazing S. grandis community. Litter decomposition rate had no significant correlation with nitrogen (N) content, had a negative correlation with phosphorus (P) content and positive correlation with the ratio of nitrogen and phosphorus (N/P) in fenced sites. Litter decomposition rate showed positive relations with nitrogen (N) and (N/P) in grazing sites and had no significant correlation with phosphorus (P) content.