Effects Of Photodegradation On Leaf Litter Decomposition Of Lindera Glauca In Zijinshan Mountain

In forest ecosystem,litter performs an important linkage between plant community and soil.Therefore,litter decomposition constitutes a key process in maintaining the structural and functional integrity of ecosystem.Currently studies evaluating the effects of light radiation on litter decomposition mainly focused in the arid and semi-arid grassland ecosystems.However,research of the photodegradation in forest ecosystems is rare,which has important implications for elucidating litter turnover,biogeochemical cycling,and nutrient dynamics in forest soils.This paper studied the effects of light radiation on litter chemical composition of Lindera glauca in Zijinshan Mountain,by testing the decomposition dynamic,nutrient release process and the soil enzymes activities within the leaves.The main results were as follows:(1)Initial litter nitrogen and lignin concentrations of L.glauca that grown under natural light radiation environment were lower than that of unexposed(P<0.05).The initial C/N ratio between light treatments also differed significantly(P<0.05).These results indicated that long-term light radiation can significantly alters litter initial matrix quality.(2)Long-term light radiation promoted leaf litter decomposition,but soil fauna were not significantly different between the light treatments.The reasons may be as follows:1)As L.glauca is not a dominant species in the Zijin Mountain forest,soil fauna may be more inclined to feed the litter of dominant species,resulting in insignificant contribution of soil fauna on the decomposition of L.glauca.2)L.glauca is an aromatic plant,the taste of which may be not favored by soil fauna,resulting in a decreased contribution of soil fauna.3)The diversity and abundance of fauna in the selected plots might be too less to result in significant impact.(3)There was a net nitrogen(N)release across all treatments.The initial N content was significantly different in two different light treatment environments(P<0.05),indicating that light can affect the initial N content of L.glauca before it shed and fall to soil.In addition,in this experiment,the soil fauna could exert a significant influence on litter N release since the 10th month of incubation,while the light treatments only had a significant effect on litter N release in the 2nd month.There was no significant light-fauna interactions on the overall nitrogen release.The dynamic of C also showed a positive release across all experimental treatments.During the one-year decomposition process,soil fauna significantly affected litter C release process of L.glauca,but the light factor only began to significantly affect carbon release since the 12th month.(4)Initial litter lignin content of L.glauca were a significantly different between the light treatments(P<0.05),but there was no significant difference between the initial cellulose content,indicating that long-term exposure to natural light could promote lignin decomposition,and consequently helps accelerate later biodegradation in the soils.The main effects of soil fauna and light and their interactions could significantly affect the decomposition of cellulose at different time,while they only began to affect the degradation of lignin in the last four months.(5)There is a positive correlation between nitrate reductase,acid phosphatase,alkaline phosphatase and cellobiohydrolase and litter mass loss of L.glauca,while there is a negative correlation between urease and leaf litter mass loss.The correlations between ?-glucosidase as well as ?-xylosidase and litter mass loss were not significant.For the first six months of incubation,light significantly affected nitrate reductase,acid phosphatase,urease,?-glucosidase,and ?-xylosidase(P<0.05).Soil fauna had significant effects on the enzyme activities of nitrate reductase,acid phosphatase and urease(P<0.05).Therefore,it indicated that light factors affect soil enzyme activity to a certain extent,and thus help the biodegradation process of L.glauca.In summary,the enhancement of light radiation may directly or indirectly affect the various factors that have consequences in determining the decomposition process,and ultimately affects the litter decomposition rate,and the C and nutrient cycling.Therefore,the study of the effect of enhanced light radiation on the decomposition of forest litter will not only help to understand the importance of the elements cycle and energy flow in forest ecosystems,but also can help to reveal the impact of global environmental change on ecosystems as well as possible responses of ecosystems to the global changes.