Litter Decomposition In Different Successional Stages Of Loropetalum Chinense Communities In Karst Area Of Guilin

Litter decomposition is an important link between bioelement cycles and energy flow in the community ecosystems,and the main source of nutrients for plants and soil.The objective of the study was to evalutate the annual litterfall,the litter substrate mass,soil enzyme of different restoration stages of Loropetalum chinense communities and to analyze the influences of different factors on the litter decomposition rate at the different restoration stages,providing a scientific basis for the further study of ecological nutrient cycling in karst are.The main study results were as follows:(1)The litterfall in thrub stage,shrub-tree stage and treestage were 4353.04 kg·hm-^-2·a^-1,6733.24 kg·hm-^-2·a^-1 and 6587.46 kg·hm-^-2·a^-1,respectively.The litterfall in shrub stage and shrub-tree stage were the highest in August while tree stage was in October.The litterfall in three different stages were the lowest in January.The order of litterfall organs in shrubs stage and shrub-tree stage were:leaves>barks and debries>branches>floweres and fruits,respectively while in tree stage was:leaves>branches>barks and debries>floweres and fruits.(2)After one-year decomposition,the litter mass loss of Loropetalum chinense communities was the following order:shrub stage>shrub-tree stage>tree stage.For 50%and 95%litter decomposition of shrub stage,shrub-tree stage and tree stage on spending time were 1.28a,5.54a,1.38a and 5.97a,1.41a,6.09a,respectively,whose annual decomposition coefficient k were 0.541,0.502 and 0.492,respectively.After one-year decomposition,the initial content of N and cellulose at each restoration stage were generally increasing.The initial content of P in shrubs stage and tree stage were generally decliningcomparing with the shrub-tree stage.The content of organic carbon were increasing in shrubs stage and shrub-tree stage and declining in tree stage.The content oflignin in shrubs stage and shrub-tree stage were generally increasing while tree stage was generally declining.There were significant correlation between litter decomposition rate and organic carbon,N,P,C/P,N/P in shrubs stage.There were significant correlation between litter decomposition rate and N,lignin/N in shrub-tree stage.There were significant correlation between litter decomposition rate and N,cellulose,C/N,lignin/N in tree stage.Path analysis showed that the key factors of litter decomposition were C,C/N,N,C/P and N in shrub stage and shrub-tree stage,respectively.However,the C and lignin were key factors of the litter decomposition in tree stage.(3)The litter layer enzyme activity of Polyenoloxidase,Urease and Sucrase at three different restoration stages were lowest in December and the enzyme activity of Polyenoloxidase was highest in March.The enzyme activity of Urease and Sucrase were highest in June.The cellulase activity at three different restoration stages was highest in June.The lowest enzyme activity of cellulase in shrubs-tree stage and tree stage were in September while shrubs stage was in March.The order of three different restoration stages litter enzyme in different time were:Sucrase>Urease>Cellulase>Polyenoloxidase,respectively.The highest soil enzyme activity of Polyenoloxidase at three different stages were in September.The enzyme activity of Polyenoloxidase in shrubs stage and tree stage were lowest in june,in shrub-tree stage was in December,there is significant between the highest and the lowest(p<0.05).The enzyme activity of Urease?Sucrase in shrubs stage and tree stage were highest in june.The enzyme activity of Urease?Sucrase in shrubs stage were lowest in december in tree stage.The enzyme activity of Urease?Sucrase were lowest in december and march,respectively.The significant difference were found between the highest and the lowest(p<0.05).In shrubs stage,the enzyme activity of Urease was highest in March and the lowest in June whilethe enzyme activity of Sucrase was highest in Juneand the lowest in March.The enzyme activity of Cellulase in three different stages were highest in September andthe lowest in March.There is significant difference between the highest and the lowest(p<0.05).(4)Litter enzyme at the different restoration stagesplayed different role on the rate of decomposition.Correlation analysis showed thatlitter decomposition rate was positively related to the the litter layer enzyme activity of Sucrase(p<0.05)in shrub stage.There were significant correlation between litter decomposition rate and the litter layer enzyme activity of Urease(p<0.05)in shrub to tree stage.There was not significant correlation between litter decomposition rate and the litter layer enzyme activity in tree stage.There were significant positive correlation between litter decomposition rate and the litter layer enzyme activity of Urease and Sucrase in Loropetalum chinense communities(p<0.01).Path analyses showed that the Sucrase,Urease and Polyenoloxidase were key factors influencing litter decomposition in shrub stage.In shrub to tree stage and tree stage were Urease,Cellulase and Polyenoloxidase,respectively.The different restoration stages soil enzymehad different effects on the rate of decomposition.Correlation analysis showed that there was significant positive correlation between litter decomposition rate and the litter layer enzyme activity of Polyenoloxidase(p<0.01)in shrub stage and tree stage.There was significant positive correlation between litter decomposition rate and the litter layer enzyme activity of Sucrase and Polyenoloxidase(p<0.01)in shrub-tree stage.Path analyses showed that the key factors of litter decomposition in shrub stage were Sucrase and Polyenoloxidase.In shrub-tree stage were Sucrase,Polyenoloxidase and Cellulase.In tree stage were Urease and Polyenoloxidase.