Seasonal Dynamics Of Leaf Litter Quantity And Stoichiometry Of Six Tree Speices In Evergreen Broad-leaved Forest In Jinyun Mountain

Litter is the main organic matter storage component and the foundation of long-term maintenance of soil fertility in forest.It plays an important structural and functional role in ecosystem function.Researches on forest litter mainly focus on the total amount of litter and its seasonal dynamics in the community level,or the dynamics of a specific species and their biological characteristics.However,there are few studies focus on the relationship between the litter in the community level and species level.Leaf litter is the dominant component of forest litter,and it is the most activity and important part of litter decomposition and material circulation.The stoichiometry of leaf litter highly affected its decomposition process.Therefore,long-term experiments are needed to study the effects of the leaf litter quantity,seasonal dynamics,and interannual fluctuations of leaf litter in species level on the amount and dynamics of litter in community level.The study on the seasonal dynamics of the stoichiometry of leaf litter is also important for the better understanding of the mechanism of the community maintenance,succession,and material cycle of forest.In order to study the relationship between the amount of leaf litter,seasonal dynamics and inter-annual fluctuations of the main tree species and the litter pattern of the community in the evergreen broad-leaved forest,we conducted an experiment in a 1ha permanent monitoring plot of the evergreen broad-leave forest in the Jinyun Mountain National Nature Reserve.Six common woody plants with different life forms are selected,including the evergreen broad-leaved tree species Castanopsis fargesii and Machilus nanmu,the evergreen coniferous tree species Cunninghamia lanceolata and Pinus massoniana,deciduous broad-leave tree species Alniphyllum fortunei and Liquidambar formosana.172 collection frames were set up in the sample plot,and the collected litter was brought back to the laboratory monthly.Leaf litters were identified to species,dried to constant weight.In this study,we use data collected from 2014 to 2019 to analyze the amount and the seasonal dynamics of litter.The stoichiometric characteristics（carbon,nitrogen,and phosphorus）of the leaf litter of 6 major species in 2018 were measured.The main conclusions are as follows:（1）From 2014 to 2019,the amount of litter in the evergreen broad-leave forest of Jinyun Mountain was 5.15-7.20 t·ha^-1·yr^-1.The seasonal dynamics of litter showed a bimodal model with"one big peak and one small peak".The big peak appeared in May,and the small peak appeared from October to November.Autocorrelation function analysis shows that the rhythm of litter is basically consistent between years in the evergreen broad-leaved forest in Jinyun Mountain.（2）From 2014 to 2019,the leaf litter in the evergreen broad-leaved forest of Jinyun Mountain was 3.89-5.19 t·ha^-1·yr^-1.The seasonal dynamics of leaf litter showed a same pattern with total litter.The big peak also appeared in May,and the small peak appeared from October to November.Autocorrelation function analysis shows that the rhythm of litter is basically consistent between years in the evergreen broad-leaved forest in Jinyun Mountain.（3）The seasonal dynamics of leaf litter differs with different species.The peak of leaf litter of evergreen broad-leave tree species（Castanopsis fargesii and Phoebe cylindrica）mainly appear in April or May.The seasonal dynamics pattern of leaf litter of Castanopsis fargesii almost did not chang between years.The seasonal dynamics pattern of leaf litter of Phoebe cylindrica varies in a small range between different years.The seasonal dynamics pattern of leaf litter of the two evergreen coniferous species（Cunninghamia lanceolata and Pinus massoniana）is irregular.There is no constant peak of leaf litter for the two evergreen coniferous species,and they show different seasonal dynamics pattern between years.The seasonal dynamics pattern of leaf litter of the deciduous broad-leave tree species（Alniphyllum fortunei and Liquidambar formosana）is more regular than evergreen coniferous species.The seasonal dynamics of leaf litter of deciduous broad-leaved tree species are generally unimodal.The leaf litter peak of Alniphyllum fortunei appears in August or October.The leaf litter peak of Liquidambar formosana appears in November and December.（4）The carbon content range of leaf litter of 6 tree species in Jinyun Mountain is455.20～573.53 g·kg^-1.The nitrogen content range is 4.05～17.26 g·kg^-1.The phosphorus content range is 0.19～1.84 g·kg-1.The range of C:N is 30.41～131.21.The range of C:P is 294.91～2752.94.The range of N:P is 8.09-29.68.The carbon content of leaf litter of the six tree species is higher than the average global level,while the phosphorus content is lower than the average global level.This may be related to the higher rainfall and the lower phosphorus content in the soil in eastern China.（5）There is an obvious seasonal fluctuation of the C content in the leaf litter of Castanopsis fargesii and Liquidambar formosana.The N content of the leaf litter of the6 tree species shows a fluctuate mode in growing season.The phosphorus content of the leaf litter of the 6 tree species has no obvious seasonal fluctuations.（6）There is a significant negative correlation between the phosphorus content and the amount of leaf litter of Castanopsis fargesii,which may indicate that Castanopsis fargesii has a high phosphorus reabsorption rate,which may reduce the dependence on phosphorus in the environment,and thus has a competitive advantage in this area.There is also a significant negative correlation between the phosphorus content and the amount of leaf litter of Pinus massoniana,which may indicate that Pinus massoniana also has a higher rate of phosphorus reabsorption and widely distributed in the subtropical regions of China.