Study On The Decomposition Characteristics Of Forest Leaf Litter In Tongguling Nature Reserve,Hainan

The tropical evergreen monsoon elfin forest is the climax vegetation types of Tongguling Nature Reserve on Hainan island. Before the establishment of nature reserve, some of the low elevation native monsoon el tin forest were destroyed, and then formed the secondary shrub. It has already gotten a better recovery now, and have the developing trend of monsoon elfin forest. Litter decomposition can promote nutrient cycling in forest ecosystem, maintain soil fertility, guarantee plant regeneration and promote the recovery of vegetation succession process, it also plays an important role in the restoration of the ecosystem. In order to understand the leaf litter decomposition characteristics of the same species in the same vegetation distribution, which in different successional stages of the forest; we also tried to explore the impact of the invasive species litter on the litter decomposition of the successional stages of the forest. In the native tropical evergreen monsoon elfin forest and the shrubbery of destructed and natural regeneration, we take the leaf litter of common specics(Machurodendron oligophlebium and Hydnocarpus hainanensis), mixed leaf litter, the leaf litter of Chromolaena odorata invasion and native species of Clerodendrum cyrtophyllum as research object, then based on field decomposition experiment, try to explore the relationship between leaf litter decomposition and the different successional stages of forest, the nutrient release rules, and the impact of Chromolaena odorata invasion on the forest litter decomposition rate and the nutrient release rule, in order to provide basic data for the tropical evergreen monsoon elfin forest restoration, to provide a reference for the overall management of forest ecosystem. The main conclusions showed that:(1)All kinds of leaf litter in the monsoon elfin forest and the shrubbery after one-year decay, the leaf litter residual rate in monsoon elfin forest was less than in shrubbery, mixed leaf litter residual rate was greater than the single species leaf litter residual rate. The leaf litter decomposition rate in the monsoon elfin forest was significantly higher than in shrubbery, and the time for decomposing50%and95%was significantly less than in shrubbery.(2)As the leaf litter decomposition of two different succession stage forest, content dynamics of N,P,Ca,Mg were first increased and then decreased,K content was expressed as a direct decline;while C content of leaf litter was first decreased then increased in monsoon elfin forest, and first decreased, then increased and finally decreased in the shrubbery.(3)In the leaf litter decomposition process of two different succession stage forest, in prophase of decomposition, N showed varying degrees of net enrichment,besides individual treatment,the other elements showed a net enrichment,the overall elements showed the net release.(4)In the monsoon elfin forest,the decomposition coefficient k had significant positive correlations with the initial N mass fraction (P<0.05), and with the initial C/N ratio had significant negative correlation (P<0.01).In the shrubbery, decomposition coefficients k had significant negative correlations with the initial C mass fraction and C/N value (P<0.05).(5)The invasive species of Chromolaena odorata and native species of Clerodendrum cyrtophyllum were mixed in different proportions dominant species leaf litter of Maclurodendron oligophlebium, then put it in the shrubbery for280days, through calculating the residual rate of dry weight and Olson exponential model, the results showed that being mixed with invasive species of Chromolaena odorata and native species of Clerodendrum cyrtophyllum could effectively accelerate the decomposition of leaf litter, and the Chromolaena odorata showed more significant effect. The greater the proportion added, the faster the litter decomposed.And the decomposition coefficient k had significant positive correlations with the initial P content (P<0.05), and with the initial C/N ratio had significant negative correlation(P<0.05). By observing the variation curve of nutrient content and residual volume, we found that being mixed with Chromolaena odorata could significantly accelerated the release of N and P of leaf litter in prophase of decomposition.