Decomposition Characteristics Of Four Types Of Forest Litter In Three Forest Stands And Their Impact On Soil Properties

There are problems in the management of natural secondary forests and plantation of Betula alnoides and Pinus kesiya,such as a lack of scientific rationality,decreased forest biodiversity,decreased site quality,low productivity,and susceptibility to pest outbreaks.Using local broad-leaved tree species to construct mixed forests is an effective way to solve various ecological problems in artificial forests,especially pure artificial forests and secondary forests,introduction of suitable broad-leaved trees can promote the decomposition of litter under artificial forests and natural secondary forests,improve the nutrient recovery rate,and maintain the stability of soil fertility.Using the field decomposition bag method,dynamically simulate the forest litter of different native broad-leaved and coniferous tree species under different forest stands in the field,to study the decomposition process and chemical component changes of the litter of Castanopsis hystrix,Altingia excelsa,Pinus kesiya,and Mesua ferrea in P.kesiya plantation,natural secondary forest,and Betula alnoides plantation.The Olson model was employed to forecast its decomposition process and to analyze the soil’s reaction to litter decomposition.To explore the impact of litter decomposition on soil fertility,so as to provide data support for the study of nutrient cycling in forest litter and the relationship between litter and soil interface for different broad-leaved and coniferous tree species under different forest stands,and to provide scientific basis for understanding the functional mechanism of litter from different afforestation tree species in soil restoration in different forest stands,To provide theoretical basis for nutrient restoration of degraded soil in artificial forests in Yunnan Province through the construction of mixed forests,provide guidance for the selection and allocation of afforestation tree species in actual production of artificial mixed forests,and provide theoretical basis for the sustainable management of major artificial forests in Yunnan.(1)There are significant differences in the decomposition process of different litters in different stands.The rapid decomposition stage of the litters of A.excelsa and C.hystrix was 75 days ago,and the litters of P.kesiya appeared to decompose rapidly from75 to 105 days ago(0.51-0.67%/d).Except for P.kesiya forest,the litters of Mesua ferrea decomposed rapidly before 45 days,and there was no significant rapid decomposition stage.According to Olson,the decomposition rates of the four types of litter in the three stands are all as follows:A.excelsa>P.kesiya>C.hystrix>M.ferrea.A.excelsa decomposes the fastest in the B.alnoides forest(0.57%/d),P.kesiya decomposes the litter similarly in the P.kesiya forest and the B.alnoides forest(0.40%/d),C.hystrix decomposes the fastest in the P.kesiya forest(0.35%/d).(2)With the advancement of litter decomposition,the four types of litter have improved the soil nutrients of the forest land to varying degrees,and increased the activities of soil sucrase,urease,and acid phosphatase.The litter of P.kesiya has the greatest increase in sugarcane enzyme activity in P.kesiya forest and secondary forest(6.08 mg glucose/g/d),while the litter of C.hystrix has the greatest increase in urease activity in P.kesiya forest and secondary forest(17.90 μg glucose/g/d).The highest increase in acid phosphatase activity(85.35 nmol/h/g)was observed in the litter of A.excelsa.(3)The total carbon,nitrogen,potassium,lignin,and cellulose contents of the four types of litter were released during the decomposition process in the three stands.The highest total carbon release rate(84%-89%)and the highest total nitrogen release rate(68.86%-83.23%)were observed in the A.excelsa.The total nitrogen content of the P.kesiya litter showed a decrease in release rate during the middle decomposition stage of the secondary forest and the B.alnoides forest,with a decrease of 8.70%-16.61%;The total phosphorus in the litter of C.hystrix and M.ferrea was first enriched and then released in the secondary forest and B.alnoides forest;The litters of A.excelsa and P.kesiya show a pattern of first release,then enrichment,and then release.In the secondary forest,the litter of A.excelsa has seen the greatest rise in soil organic carbon,with a27.49 g/kg rise.In the B.alnoides forest,it has the greatest increase in soil alkaline nitrogen content,with an increase of 33.71 mg/kg.The litter of C.hystrix has the greatest increase in available potassium content in the P.kesiya forest,with an increase of 43.00mg/kg.The capacity for soil cation exchange initially augmented,then diminished to its starting point.C.hystrix showed the greatest increase in soil cation exchange capacity in the P.kesiya forest,with an increase of 5.66 cmol/kg.Among them,the decomposition rate and nutrient release rate of A.excelsa litter in each stand are the fastest,while the C.hystrix litter is more suitable for decomposition in the P.kesiya forest,with a higher rate and nutrient release rate than in the B.alnoides forest.The decomposition rate of M.ferrea litter in the three stands is the slowest,and the effect of soil improvement in the forest is only higher than the control treatment,but the nutrient release is stable,which can increase the stability of soil organic carbon pool.In the transformation and quality improvement of P.kesiya and natural secondary forest,it is appropriate to introduce C.hystrix and A.excelsa,reduce the proportion of P.kesiya;B.alnoides forest can be densely planted with A.excelsa or M.ferrea for forests in low canopy density.