Study Of Carbon Flow During Decomposition Process In Leaf Litter From Loess Plateau

Litter refers to the organic matter which are produced by plant components and then returned to the ground, acting as the source of matter and energy for decomposers so as to maintain the ecosystem functions. The leaf decomposition and carbon flux process play an important role in biogeochemical cycling. Therefore, the study of the litter decomposition process contributes to comprehending biogeochemical cycle and formation of soil organic matter in ecosystem. Due to severe natural environment and long-term reclamation and irrational utilization hereof, loess plateau has been faced with heavily damaged natural vegetation, poorer soil as well as extremely weak ecosystem. In recent years, Chinese government has initated a big ecological project to reestablish the ecology by grain for green. With the process of the above-mentioned projects, plant litter becomes the main source of organic matter and nutrients in this region. Therefore, study of litter decomposition conditions and ecosystem management has theoretical and guiding significance.In this paper, leaf litter of several plants widely planted in loess plateau were chosen as the object of study and indoor constant temperature incubation was chosen to study different leaf litter’s decomposition characteristics and its impact on soil organic carbon, nitrogen and phosphrous content in soil, impact of different temperature, soil water content and nitrogen addition on leaf litter’s decomposition characteristics, and in the end, decomposition characteristics of mixing litter leaves. The main conclusions are as follows:1. After added to soil, the CO2 release rate of different leaf litters showed similar trend, which showed relatively high CO2 release rate at the initial stage followed by relatively slow and steady decomposition process. Maize leaf litter had the maximum calculative amount of CO2 release, while Pine tabulaeformis the minimum. The mass of different leaf litters decreased over time. The decomposition rate of 10 types of leaf litters involved in this study was mainly in the range of 0.47-1.20 kg kg-1 a-1. Based on relevant analysis of litters’ initial substrate mass and residual rate of dry weight, results showed that decomposition rate of leaf litters is related to all carbon, phosphorus and potassium content(P<0.01). The content of N and P was on the rise, while change of content of C and K were different during the decomposition of different leaf litters. Modes of nutrient release of different leaf litters during various stages. C and N in the decomposition of 10 types of leaf litters is approximately in the mode of release, while P and K of different leaf litters had significant difference in dynamic condition.2. Temperature rise could accelerate CO2 release during decomposition of leaf litters. Calculative amount of CO2 release at 25 ℃ was 2.4-25.3% larger than that at 15 ℃. High soil water content in soil could accelerate CO2 release of leaf litters. Calculative amount of CO2 release in condition of 80% field capacity was 9.5-17.7% higher than that of 40% field capacity. The impact of nitrogen addition on calculative amount of CO2 release varied with different leaf litters. Nitrogen addition could accelerate CO2 release of Pine tabulaeformis at later stage and inhibit that of stipa capillata Linn., while had no different impact on CO2 release of Black Locust and Populus L. leaf litters. A rise of temperature and water content in soil could accelerate decomposition of leaf litters and nitrogen addition could accelerate decomposition of Black Locust, stipa capillata Linn. and Populus L. leaf litters. Temperature rise could significantly lower residual rate of C at the early stage of decomposition of most leaf litters, promote N, P and K release of part of the leaf litters. Impact of water content and nitrogen addition on nutrient release of leaf litters was related to source of leaves and types of nutrient.3. Mixing of leaf litters in group of Black Locust- stipa capillata Linn., Black Locust – Populus L., stipa capillata Linn.- Populus L., could accelerate CO2 release, while the impact of mixture in other groups varied with different decomposition stage. At month 12, all litter mixtures did not have effect on the mass remaining,but most litter mixtures have a significant positive effect at initial. Impact of mixing of litters on nutrient release in decomposition were not the same in different groups of litters, and, degree of impact and tendency changed over the period of decomposition. After 12 months of decomposition, the amount of organic carbon and nitrogen content in soilin mixing leaf litters was lower than that in any single leaf litter, with average amount lower 16.3% and 13.9%, while phosphorus content in soil increased 3.4%.