Dynamics Of Natural Decomposition Of Tea Prunings And Leaf Litter Of Associated Tree Species And Their Effects On Soil Nutrients

Tea industry is one of the characteristic industries in Guizhou.However,the large-scale planting of single Camellia sinensis leads to the decline of biodiversity and poor stability of ecosystems of tea plantations,which easily leads to the decline of soil fertility and the decline of tea production and quality.Planting appropriate associated tree species and returning plant residues to improve soil nutrients are effective ways to solve the problem and realize the sustainable development of ecological tea plantations.This research adopts the decomposition method of mesh bag in tea plantation field decomposition experiment,to study the dynamics of mass loss,nutrient release,enzyme activity and soil nutrient change of the pruning content of Camellia sinensis and four kinds of litter leaves of common local tree species(Cunninghamia lanceolata,Pinus massoniana,Cinnamomum glanduliferum,Betula luminifera)by separate and mixed decomposition.From the perspective of decomposition of plant residues,select the suitable associated tree species of tea plantation and returning materials,the results are as follows:(1)With the increase of decomposition time,the mass loss of different plant residues increased gradually.The decomposition process could be divided into rapid decomposition stage(0-62 days)and slow decomposition stage(123-366 days).The average decomposition rate of0-62 days was 241.93 mg·d^-1 and the average decomposition rate of 123-366 days was 21.12mg·d^-1,and the interannual decomposition rate ranged from 2.24 mg·d^-1 to 283.98 mg·d^-1.Olson's exponential decay model could well fit the decomposition process of plant residues(R²>0.82).The decomposition half-life of plant residues in the study ranged from 0.44 years to 1.59 years,and the decomposition turnover ranged from 3.73 years to 14.16 years.On day 366,the cumulative decomposition rate of plant residues was 42.70%?59.06%,and the fastest decomposition rate was Cinnamomum glanduliferum and the slowest was Pinus massoniana.The cumulative decomposition rate of plant residues was between 44.53%and 58.31%,and the decomposition rate was the fastest for Cinnamomum glanduliferum+Betula luminifera,and the slowest for Camellia sinensis pruning+Cunninghamia lanceolata.Lower initial lignin,cellulose contents and higher initial nitrogen,phosphorus and potassium contents were beneficial to the rapid decomposition of plant residues,and initial nitrogen,phosphorus,potassium and lignin contents could better reflect the decomposition speed of plant residues.The combination of tea prunings and broad-leaved tree species promoted decomposition,while the combination of Camellia sinensis prunings and coniferous tree species inhibited decomposition.The combination of coniferous tree species and Betula luminifera accelerated decomposition,but the combination of coniferous tree species and Cunninghamia lanceolata inhibited decomposition.(2)In the decomposition process of different plant residues,the contents of carbon,nitrogen,potassium and cellulose were all in the state of net release,phosphorus was in the state of net release and enrichment-release,lignin was in the state of net release and alternating release and enrichment.The mixed decomposition of tea pruning and Betula luminifera had the strongest promoting effects on the release of carbon and nitrogen,and the mixed decomposition of Betula luminifera and Pinus massoniana had the stronger promoting effects on the release of phosphorus and potassium and the degradation of cellulose and lignin.(3)In the decomposition process of different plant residues,sucrase and cellulase mainly played their roles at the early decomposition stage,catalase and acid phosphatase mainly played their roles at the late decomposition stage.While polyphenol oxidase showed high activity at both the early and late decomposition stages,and had a low enzyme activity at the middle stages of decomposition.Among them,in the process of decomposition of plant residues,invertase activity first increases and then reduces overall trends,cellulose enzyme activity to reduce the fluctuation change trend,catalase and acid phosphatase activity change dynamic is roughly similar to that of enzyme activity were slightly lower at the early stage of the decomposition,decomposition of late has increased dramatically,acid phosphatase activity increase first decreases after the change trend,polyphenol oxidase activity were lower before the change trend of increase,and the change dynamics were similar to those of the seasons.But urease fluctuates irregularly.(4)Except for Cinnamomum glanduliferum,returning single plant residues to the field had promoting effects on the improvement of soil nutrient content.The effects of mixed decomposing plant residues on the improvement of soil nutrient content varied with the combination of plant species.The change of soil organic carbon content,there was no significant correlation with the decomposition of plant residues,nitrogen,phosphorus,potassium and enzyme activity in the process of decomposition of plant residues,there is a certain correlation of soil total nitrogen content and plant residues quality loss and carbon release rate were significantly negative correlation,and soil total phosphorus,total potassium,hydrolytic nitrogen,available phosphorus,available potassium content and plant residues quality loss and carbon release rate was significantly positively related.The mixed decomposition of Cinnamomum glanduliferum and Cunninghamia lanceolata had the stronger promoting effect on increasing the contents of soil organic carbon,total nitrogen and total potassium,the mixed decomposition of Cinnamomum glanduliferum and Pinus massoniana had the strongest promoting effect on increasing the contents of soil total phosphorus and available phosphorus,and the mixed decomposition of Camellia sinensis prunings and Cunninghamia lanceolata had the stronger promoting effect on increasing the contents of soil hydrolytic nitrogen and available potassium.Based on interspcific coordination between four tree species and Camellia sinensis,Pinus massoniana and Betula luminifera were the best associated trees of Camellia sinensis,followed by Cinnamomum glanduliferum.From the perspective of decomposition of promoting the soil nutrient,plant residues returning alone decomposition can improve soil nutrient content,Camellia sinensis pruning,litter leaves of Cunninghamia lanceolata,Pinus massoniana,Cinnamomum glanduliferum,Betula luminifera as returning decomposition material separately.Cinnamomum glanduliferum mixed with different plant residues can improve the nutrient content of the soil,and it was an optimal material for the mixed return to the field and decomposition.Cinnamomum glanduliferum mixed with Cunninghamia lanceolata can fully increase the soil carbon,nitrogen,phosphorus,and potassium content.It is the better combination of mixed return to the field and decomposition.Cinnamomum glanduliferum mixed with Pinus massoniana can effectively promote the increase of soil phosphorus.Adding Cinnamomum glanduliferum Mixed with Camellia sinensis pruning material can be used as a decomposing material to improve soil available nutrients.