Litter Decomposition Dynamics Of Typical Stand Types In Tianma Reserve And Its Influence On Soil Properties

Litter decomposition is an important part of nutrient cycling and energy flow in forest ecosystem.It is of practical significance to explore the internal decomposition mechanism for the sustainable development of forest ecosystem.This research focused on the litter decomposition process of different litter types and their effects on soil nutrients and soil enzyme activities.Three parts of litters of branches,leaves,and mixed branches and leaves which from deciduous broad-leaved forest,mixed coniferous broad-leaved forest,Pinus taiwanensis forest,and Cunninghamia lanceolata forest were collected in the Tianma National Nature Reserve,Anhui province.These litters were put in mesh bag,and take in-situ decomposition experiment in June,2019.Collecting samples of litter and soil to analyze the Litter loss,soil nutrients and soil enzyme activities.The main results were as follows:(1)The decomposition process of litter of the four forests showed a trend of fast decomposition in the early stage(0-94 d),slow decomposition in the middle stage(94-336d)and slow decomposition in the late stage(336-496 d)with a slightly increased decomposition rate compared with that in the middle stage.After 496 d decomposition,the litter mass residual rate of the broadleaved deciduous forest and the mixed coniferous broad-leaved forest was significantly lower than that of the P.taiwanensis forest and the C.lanceolata forest(P<0.05).The decomposition residual rate of branch litter of the same forest was significantly higher than that of leaf litter and mixed litter during the whole decomposition cycle(P<0.05).Except for branch litter,the mass residual rates of four forests leaves and mixed litter were un-decomposed<semi-decomposed layers,but the difference was not significant(P<0.05).(2)The litter decomposition of the four forests was in line with the exponential decay model,the decomposition time for 50%of litter was 1.12 a<t_0.5<4.77 a,the decomposition time for 95%of litter was 4.83 a<t_0.95<20.62 a,and the time required to decompose 50%and 95%of branches litter was significantly longer than that of leaves and mixed litter.(3)The contents of C,N and P in litters were significantly affected by forest type,decomposition time of litters and their interactions(P<0.05).The residual rates of C,N,and P in litters of four forests were gradually decreased with the decomposition process,and the changes of C,N,and P contents were all net release mode.(4)During the decomposition process of the four forests litters,the soil pH value varied from 3.09 to 5.99,and the pH value in the 0-10cm soil layer was lower than that in the10-20 cm soil layer.In the same soil layer,the pH values of each forest were all sort by C.lanceolata forest>deciduous broad-leaved forest>mixed coniferous broad-leaved forest>P.taiwanensis forest.The soil pH in C.lanceolata forest and the P.taiwanensis forest were all different with the mixed coniferous broad-leaved forest and the deciduous broad-leaved forest in significantly(P<0.05).But there were no significant difference between the mixed coniferous broad-leaved forest and the deciduous broad-leaved forest(P>0.05).(5)The soil N content(0-20 cm)of the P.taiwanensis forest and the mixed coniferous broad-leaved forest were significantly higher than that of the deciduous broad-leaved forest and the C.lanceolata forest.The C content in 0-10 cm soil layer of the P.taiwanensis forest and the mixed coniferous broad-leaved forest were significantly higher than that of the deciduous broad-leaved forest and the C.lanceolata forest.The content of C in 10-20 cm soil layer sorted by the Pinus taiwanensis forest>the mixed coniferous broad-leaved forest>the deciduous broad-leaved forest>the C.lanceolata forest.The soil P contents of 0-20 cm in the C.lanceolata forest was significantly higher than the other three forests(P<0.05).Litter composition,decomposition time and soil structure had significant effects on soil C,N and P contents(P<0.05).(6)The effects of litter decomposition on soil enzyme activity were different in different forest types.Soil urease activities increased firstly and then decreased in the mixed coniferous broad-leaved forest and the C.lanceolata forest,decreased firstly,then increased and then decreased in the deciduous broad-leaved forest and the P.taiwanensis forest in the process of litter decomposition.Soil sucrase activities and soil peroxidase activities showed an increasing trend in four forests.Soil acid phosphatase activities fluctuated during litter decomposition in the mixed coniferous broad-leaved forest,the deciduous broad-leaved forest,and the P.taiwanensis forest,but changed differently in the C.lanceolata forest due to different litter components.(7)There was a certain correlation among litter nutrients,soil nutrients,and soil enzyme activities.The soil C,N,P contents and soil enzyme activities were significantly affected by forest type(P<0.05).The difference of forest type led to the difference of litter,which effected on soil enzyme activities and nutrients.