Researches On The Leaf Litter Decomposition Dynamic Of Eucalyptus Urophylla×eucalyptus Grandis Mixed With Other Species Leaf Litters

The links between aboveground and belowground subecosystem has now been the focus of many researchers. Changes in plant community structure can alter litter resource which enter the decomposer subsystem. There is an increasing awareness that different components of the soil food web show a range of responses to these resource inputs, however, the mechanism is still unclear to us.Non-additive patterns have been found in some mixed-species leaf litter decomposition studies which compared the characteristics of decomposition in litter-mixes to the responses predicted from decomposition of single-species litters. Another way to determine wherther interactions among litters are occurring in mixes is to analyze component litters in the mixture separately and compare decay of each species in the mix to the decay of each species when decaying alone, but not many studies have done this which may cause the lost of mechanistic information without single-species analysis. As litter identity is an important factor to influence litter decomposition rate when decaying alone, we wondered whether the litter identity of the component in the mixed-species would determine the result of mixed-species leaf litter decomposition and whether the mixing effect would change during the decomposition dynamic. We also fouced on the decomposer community which may responsed to the change of litter resource. In this study, we chose the Eucalyptus urophylla×Eucalyptus grandis as our main object, we mixed Eucalyptus urophylla×Eucalyptus grandis leaf litter respectivly with other seven species leaf litter which were Robinia pseudoacacia, Zanthoxylum bungeanum, Koelreuteria bipinnata, Alnus cremastogyne, Cinnamomum camphora, Magnolia denudata and Bambusa pervariabilis×Dondrocalamopsis daii. We detected the mass loss; canbon, nitrogen and phosphorus content; microbial biomass and microbial community structure; soil fauna density and soil fauna community component after three months, six months and eight months decomposition.The results are as follows:The mass loss of Eucalyptus urophylla×Eucalyptus grandis leaf litter in the mixed decomposition groups was no difference with single-specie decomposition of Eucalyptus urophylla×Eucalyptus grandis leaf litter during decomposition.The difference of Eucalyptus urophylla×Eucalyptus grandis leaf litter carbon, nitrogen and phosphous content between the mixed decomposition groups and single-specie decomposition was affected by decomposition stage. The N/P of Eucalyptus urophylla×Eucalyptus grandis leaf litter which respectivily mixed with Robinia pseudoacacia, Alnus cremastogyne, Magnolia denudata leaf litters were significant lower than the single-specie decomposition of Eucalyptus urophylla×Eucalyptus grandis leaf litter. And the C/N, C/P and C/N/P of Eucalyptus urophylla×Eucalyptus grandis leaf litter in the mixed decomposition groups were no significant different with the single-specie decomposition.Mixing Eucalyptus urophylla×Eucalyptus grandis leaf litter with Robinia pseudoacacia leaf litter would improve the carbon, nitrogen release of Eucalyptus urophylla×Eucalyptus grandis leaf litter. Mixing Eucalyptus urophylla×Eucalyptus grandis leaf litter with Bambusa pervariabilis×Dondrocalamopsis daii leaf litter would inhibit the carbon, nitrogen and phosphous release of Eucalyptus urophylla×Eucalyptus grandis leaf litter.The bacterial biomass and fungus biomass of Eucalyptus urophylla×Eucalyptus grandis leaf litter in all the mixed-species decomposition groups were higher than the single-specie decomposition. The bacterial community structure of Eucalyptus urophylla×Eucalyptus grandis leaf litter in the mixed-species decomposition groups were different with the single-specie decomposition.The fungus community structure of Eucalyptus urophylla×Eucalyptus grandis leaf litter in the mixed-species groups were also different with the single-specie decomposition of Eucalyptus urophylla×Eucalyptus grandis leaf litter.During decomposition, both the bacterial community structure and fungus community structure were changed. The main factors which caused the difference of bacterial community structure and fungus community structure during decomposition were canbon and nitrogen content.The soil fauna density of Eucalyptus urophylla×Eucalyptus grandis leaf litter which respectivly mixed with Robinia pseudoacacia and Zanthoxylum bungeanum leaf litter were significant higher than the the single-specie decomposition of Eucalyptus urophylla×Eucalyptus grandis leaf litter at the beginning of decomposition.The soil fauna density of Eucalyptus urophylla×Eucalyptus grandis leaf litter which mixed with Alnus cremastogyne leaf litter were significant lower than the single-specie decomposition of Eucalyptus urophylla×Eucalyptus grandis leaf litter after 6 months decomposition.In conclution, we found mixing decomposition could alter the nutrient release, microbial biomass, microbial community structure and soil fauna density of Eucalyptus urophylla×Eucalyptus grandis leaf litter in mixed decomposition groups, but mixing decomposition did not change the decomposition rate of Eucalyptus urophylla×Eucalyptus grandis leaf litter in mixed decomposition groups and had a low effect on soil fauna component of mixed decomposition groups. We also knew that microbial community and soil fauna community were changed during decomposition which reminded that litter decomposition itself was also a important factor to influence the food web structure underground. We considered litter mixed decomposition has a lower effect on food web structure underground than decomposition itself. But more works need to do to know the answer.