Characteristics Of Leaf Litter And Fine Wood Decomposition And Its Affecting Factors In Fragmented Habitats

Litter decomposition is a key link of material cycle and energy flow in forest ecosystems.The mineralization of organic carbon to carbon dioxide,a central part of the global carbon cycle,is largely regulated by decomposition.In recent decades,due to human impacts from activities such as commercial logging,urbanization and agricultural developments,forests around the world have been destroyed to varying degrees,and about 70% of the forests have been in habitat fragmentation.At present,most of the studies on habitat fragmentation focus on the impact on biodiversity,and there is a lack of research on ecosystem functions,especially litter decomposition.Therefore,it is of great significance to study and deeply understand litter decomposition and its response mechanism to environmental changes in fragmentated habitats.Habitat fragmentation can change the decomposer community by changing abiotic environmental factors and plant communities.At the same time,different groups in the decomposer community(soil fauna and microorganisms)may have different responses and preferences to environment factors and decomposition substrates.As a result,habitat fragmentation had different effect types(positive,negative,no)on the litter of different species and different types of litter of the same species(leaf litter and fine wood).In order to investigate the above problems,leaves and fine wood of Quercus serrata?Castanopsis sclerophylla?Loropetalum chinense and Pinus massoniana,which are common woody plants in the Thousand Island Lake region,were selected as decomposition substrates.Two kinds of mesh size litter bags(coarse-mesh and finemesh)were used to exclude or include soil macroinvertebrates.Decomposition experiments were conducted for one year in 45 plots(margin vs interior)on 15 islands and in 15 continental plots located in contiguous forests.The main results are as follows:(1)The decomposition rates of leaf litter and fine wood were significantly different among species.The decomposition rate of leaf litter of Pinus massoniana was significantly lower than those of other three species,and the fine wood decomposition rate of Pinus massoniana and Quercus serrata was significantly lower than that of Castanopsis sclerophylla and Loropetalum chinense.(2)Soil macroinvertebrates had different effects on the decomposition rates of leaf litter and fine wood.The exclusion of macroinvertebrates significantly reduced the decomposition rates of the four types of leaf litter,but had no significant effect on the decomposition rates of fine wood.(3)Fungal fruiting body coverage in mainland was significantly lower than that in island,and mycelial coverage in mainland was significantly lower than that in island.Island isolation had a negative effect on termites and fungi mycelial coverage by decreasing tree species diversity,island area had a negative effect on fungi mycelial coverage by increasing air humidity,and increasing tree richness had a positive effect on fungi.(4)There was no significant difference in litter decomposition rates between mainland and island,but fine wood decomposition rate of Quercus serrata and Loropetalum chinense is significantly higher in island than in mainland.The decomposition rates of leaf litter and fine wood were not significantly different between margin and interior of the island.Island isolation had no significant effect on the decomposition rates of leaf litter and fine wood.However,there is a significant positive correlation between leaf litter decomposition rate of Quercus serrata and island area,but there is no significant correlation between decomposition rate of the four species and island area.In this study,we systematically explored the effects of habitat fragmentation on the decomposition rates of litters and fine wood,as well as the regulatory roles of abiotic environment and decomposer communities.These results suggest that species characteristics(substrate quality)determine the decomposition rates of the two types of litter,while the contribution of the decomposition animals depends on the type of litter(leaf litter and fine wood).Environmental factors may change under the action of habitat fragmentation and have the same or different effects on different decomposer groups(termites and fungi),thus causing changes in the composition of decomposer communities.In general,the relationship between decomposition rate of litter and habitat fragmentation depends on the quality of its characters and the compatibility with the decolorizer groups.For example,the nutrient content of Quercus serrata leaf litter is the highest,and soil animals are the main decomposers,so its decomposition rate increases with the increase of island area.The results of this study are helpful for us to understand the impact of forest fragmentation on litter decomposition rate in subtropical areas,and provide theoretical support for scientific management of forest biodiversity and ecosystem function in subtropical areas.