| Plant litter decomposition is the principal way of material cycle and energy conversion in forest ecosystems. The nutrient release of tree litter on forest land nutrient balance and growth had the vital significance in Pinus massoniana plantations. Forest gap size could play an important role in litter decomposition and nutrient release due to its effects on the microenvironment. To evaluate the effects of forest gap size and soil fauna on leaf litter nutrient release of four native species (Toona ciliata, Phoebe zhennan, Cinnamomum camphora, Pinus massoniana), and to evaluate the correlation between litter leaf nutrient release and temperature, water content of environmental factors, a field experiment consisting of seven gap sizes (i.e., G1:100 m~2, G2:225 m~2, G3:400 m~2, G4:625 m~2, G5:900 m~2, G6:1225m~2, and G7: 1600 m~2) was established in Laifu town in 2013. The main research results are as follows:1) In the process of decomposition of two years, the average temperature within gaps and moisture content changing rule were obvious with the seasonal changed.The average temperature was lowest in January and highest in August. The water content in May and August were higher than other times. The average temperature and water content showed a trend of rising with the increase of forest gap area, but both had no significant differences between gap center and edge.2) Elements content variation characteristics of different species were different. Element content variation characteristics of the same litter showed the same in different gaps. After two years, Litter N and P content in G2-G4 gaps were higher than others gaps and CK, but K content in G5-G7 gaps were lower than others gaps and CK.3) Decomposition time and specie both had significant impact on the litter leaf nitrogen, phosphorus and potassium release. However, location within gaps had no significant impact on the litter leaf three elements release rate. The release of the three elements were mainly concentrated in the first year, entered the stage of slow release of the second year. Elements release rate of T. ciliate were the highest among the four species.4) Litter leaf nitrogen, phosphorus and potassium elementreleaserate all were significantly influenced by forest gap size. In addition to the Toona ciliate, the other three litter leaf N and P element took place concentration. Furthermore, N and P elements release rate were significantly higher in forest gaps (G3-G5) than in other gaps (CK, G1-G2, G6-G7).However, litter K element release rates were significantly higher in forest gaps (G5-G7) than in the other gaps (CK, G1-G4). The correlation between litter elementsrelease rate and temperature or water content were positive significant.5) When excluding soil fauna, the changing rules of litter N and P elements release rate were obvious different from those with soil fauna exists. At the end of decomposition test, the soil fauna were significantly promoted litter N, P and K elements release for Cinnamonum camphora and Pinus massoniana. Therefore, the contribution rates of soil fauna showed positive effect.The research results showed:G3-G5 forest gaps were in favour of litter N and P elements release, and G5-G7 forest gaps were in favour of K element release. The nutrient release of four litters occurs mainly in the first year. Elements release rate of T. ciliate were the highest among the four species. forest gap size and litter sampling location in the gaps significantly affected litter mass loss and nutrient release. However, the extent of these effects and dynamic changes depended on the initial litter quality. Therefore, G3-G5 forest gaps were more suitable of the interference forest gap in Pinus massoniana plantation in the area, were advantageous to release the serious lack of N and P nutrient in the subtropical Pinus massoniana plantation. |
PDF Full Text Request