Study On The Litter Decomposition And The Factors In Peatland

The aboveground litter decomposition process, and effects of litter quality andenvironmental factors were studied by the decomposition bag method in five different plantcommunities in Jinchuan peatland which located in Jilin Longwan National Nature Reserve.The five typical plant communities are dominated by Carex schmidtii (C), Carex tenuiflora(CT), Phragmites australis and Carex spp.(PC), Carex schmidtii and Thelypteris palustris var.pubescens (CPh), and Carex schmidtii and Sphagnum (CS), respectively. Several indexreperesenting litter decomposition were measured and calculated, including litter weight lossrate, nutrient accumulation index of carbon (NAI_C), nutrient accumulation index of nitrogen(NAI_N), amount of carbon release and nitrogen release. The relationships between thosedecoposition index and litter quality (C, N, P, C/N, lignin) and environmental factors (waterlevel, flooding period, pH, total nitrogen and total phosphorus of water, soil organic matterand N, P) were explored and disccused. Factor analysis and stepwise regression analysis werealso conducted for the litter quality and environmental factors.The main conclusions of this study were as followed:(1) Overall, the litter weight loss ratio of this herbaceous peatland kept similar annualdecomposition rate in three-year process of decomposition. The anual weight loss rate ofdecomposition was27.17±0.67%,28.69±1.22%and26.15±1.56%at the1st,2ndand3rdyear, respectively. The decomposition rate of C. schmidtii community was significantly lowerthan other communities (24.46±1.02%). Litter traits had significantly effects on the weightloss rate, and the effects varied at different stages of decomposition. The weight loss wasenhanced by the rapidly decomposed compounds at first, then decreased by the compoundswhich were difficult to break down at the late decomposing process. The effect of the initiallitter traits on litter weight loss was gradually weakened along with the decompostion process.The water level dropped below the soil surface strongly affected the litter weight loss ratenegatively, indicating the importance of maintaining and restoring the flooding environmentof the peatland to reduce the decomposition rate.(2) The total amount of carbon release in three years were61.20±2.08g/m~2. The annualcarbon release deceased year after year, which was27.72±1.21g/m~2、20.82±2.10g/m~2, and12.66±1.18g/m~2in the1st,2ndand3rdyear, respectively. The capability of carbon release inPC and CTh communities, which suffering more disturbance by human activity, were higherthan C community. Contrarily, the CS community developing from C community performedlower carbon release. Therefore, to maintain the original Carex community or lead the progressive succession will keep the peatland ecosystem with high carbon sequestrationability.(3) The carbon release was mainly controlled by water condition. Less carbon releasedwas with higher water level when peatland were flooded. The pH and TP of water alsoaffected the carbon release from litters. Compared to the effect of environmental factors, theeffect of litter traits on carbon release was much lower. The carbon release positively relatedwith P content of litter, but insignificantly related with other traits. More carbon was releasedfrom the litters with higher P content, which might because of the microorganism activityimproved by phosphorus.(4) The total N release from litter decomposition was-0.009~0.93g/m~2in this peatland,and varied remarkedly among communities. The first highest total N release was in CTcommunity (0.93g/m~2) and second was in CTh community (0.63g/m~2), which mainlyoccurred in the first year. The total N release was around zero in CS community, which was0.024g/m~2while C community accumulated N by0.009g/m~2, respectively.(5) All the N was released in the first year, and varied around zero in the latter two years.As an easily and rapidly decomposed element, the nitrogen was mostly off the plant or litterbefore falling off or at the prophase of decomposition. The residual nitrogen in the litter wasthen influenced and fluctuated by the surrounding, such as nitrogen in water and soil.(6) The nitrogen release was weakly affected by environmental factors, but significantlyaffected by the litter traits. The total nitrogen release was significantly related with the initialN content and C/N ratio of the litter, indicating more nitrogen release from litter with higherN content.