| Grass litter is the general name of the organic matter derived from the death of thebiological components in the grassland ecosystem，which is an important part of grasslandecosystem with important ecology functions. The decomposition of the grass litter ingrassland ecosystem is the basic process of transformation of the residues of organic matter,the key link in the process of nutrient cycling, playing a decisive role in the soil physical andchemical properties, soil fertility and plant productivity. At present, the research of theaccumulation and decomposition of litter are mostly focused on the forests and wetlands, withless regard to the arid and semi-arid grassland. In the study, we investigated the amount oflitter accumulation and composition in the National Natural Reserve of Yunwu Mountainafter different enclosure years. We used the method of nylon mesh bag to study the massremaining, decomposition rate of Stipa bungeana and Artemisia sacrorum （stem and leaf）,mearused main nutrient element dynamic during the decomposition process of a year, andtested the influence of factors （litter type, slope aspect, the mesh size of nylon and buried tothe10cm soil layer） on the litter decomposition of Stipa bungeana. Our main conclusions areas follows:1. The litter accumulation amount and composition of grassland with different enclosure yearsThe averages amount of surface and standing litter were2.48t·hm-2and3.50t/hm-2. Thetotal litter accumulation will be fluctuating within the level of5.696t·hm-2in the NationalNatural Reserve of Yunwu Mountain at the state of equilibrium and stable development. Theamount of the standing litter accounted for about59.81%of the total accumulation of thelitter.2. Mass remaining and decomposition rate of the littersThe decomposition rate was fast-slow-fast during a year. The weight loss ratio of thefirst month accounted for an average of20.96%. The order of the value of decomposition rateconstant k was the leaf of A. sacrorum （0.446）>S. bungeana （0.446）>Stem of A. sacrorum（0.220）, sunny slope （0.355）>shady slope （0.301）. The time needed for50%decomposition of the litters were between1.39a and3.45a, and the time needed for100%decomposition ofthe litters was between6.22a and15.12a.3. Dynamic of the nutrient element changing in the decomposition of littersThe carbon concentration had fluctuantly varied with a rapidly drop and then afluctuantly rising. The nitrogen concentration were fluctuantly rising; the phosphorusconcentration were fluctuantly declining and the potassium concentration was continuouslydeclining in the process of litters decomposition during one year. In the process of litterdecomposition, the release patterns of carbon and phosphorus element wereleaching-enriching-releasing, the nitrogen element was in a enriching-releasing pattern andthe potassium element was in a continued releasing pattern. Overall, the elementaccumulation index （NAI） values of C, N, P and K of the two plant species were less than100%, so the element absolute quantity decreased in both species. The release andaccumulation of litter elements were different, which may be due to the initial elementconcentration, the state of existence of litter and the role of microbiological degradation.4. Impact factors of the litter decomposition rateThe decomposition rate constant k had significantly positive correlation with the initialnitrogen content of the litter （r=0.895） and significantly negative correlation with the C/Nratio （r=-0.940）. Comparing the sunny slope to the shady slope, the size of the nylon bag of16meshes to the100meshes and the nylon bag buried in10cm soil layer to the soil surfacewe found that the former could increase the litter decomposition significantly... |
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