| Litter, as one of the main structural and functional units in ecology system of urban green space, is a central link of the woodland material exchange between plants and soil and has a certain impact on progress of soil formation, soil nutrient return, as well as biological activity and fertility conditions of soil. Therefore, researching the composition, quantity, and dynamic features of decomposition of urban camphor community litter will help reveal self-maintaining mechanism of the urban green space. This study chose three different Cinnamomum camphora plantations with different afforestation ages in Shanghai, and studied the litter production, nutrient dynamics, litter decomposition dynamics and nutrient release model by the method of space as a substitute for time. The results showed that:1. The litter was mainly composed of fallen leaves and branches, annual litter amount between 7382.29～9162.60 kg·hm-2·a-1 and presented mid-maturation forest> mature forest> young forest. The monthly litter amount showed the bimodal type, presented two peaks in April and July.2. The carbon (C) is the main component of litter, and its content is the highest, followed by nitrogen (N) and phosphorus (P). With the increase of forest age, the content of total carbon (TC) and total nitrogen (TN) of litter increased while the content of total phosphorus (TP) reduced to a certain range, and the difference between seasons was not significant (P> 0.05).3. The litter nutrients return amount (TC, TN, TP) at different development stages are inverted "V" type, namely mid-maturation forest (4058.46kg·hm-2)> mature forest (3389.86kg·hm-2)> sapling forest (3365.35kg hm"2), and the nutrient return content of three plantation are dynamic consistent with litter quantity change.4. The litter leaves and litter branch are main content of litter standing crop while the seed is in smaller proportion. The litter standing crop includes non-decomposition (L), half-decomposition layers (D) and decomposition layer (H) and H> L> D in all sample field. There are differences between the layers of litter standing crop, and the standing crop of young forest is highest. The ratio of litter standing crop and litter production and the reciprocal of the ratio are used to estimate annual decomposition rate and turnover period, respectively. Turnover period is commonly in the range of 0.7year to 0.9year. With the increase of forest age, litter decomposition rate increase, and the turnover period shorten.5. In the observation period (1.5 years), litter decomposition is divided into three periods:the early stage of the decomposition, litter mass loss is obvious; the middle of the decomposition, litter mass loss changes gently; the late decomposition, litter mass loss increase. Litter decomposition rate of litter leaves is twice of litter branch.6. According to simulation results by Olson equation, with the increase of forest age, the litter decomposition coefficient K increases, and the decomposition rate of litter accelerates. The predicted half-life of litter leaf is in the range of 0.6 year to 1.5years, while litter branch in the range of 1 year to 2 years. The time needed for the litter decomposition of 95% leaf is in the range of 2.7 years to 7.7 years, while the decomposition of 95% litter branch in the range of 4 years to 8 years.7. In the process of litter decomposition, theb nutrient release is asynchronism. Total carbon (TC) sustained release model. Total nitrogen (TN) and total phosphorus (TP) in the process of litter decomposition is a certain degree of accumulation process in the litter decomposition process, and TN/TP is relatively stable, which is about 7:1. |
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