Effects Of Litten Input On Soil Biochemical Characteristics Of Typical Plantations In Taizi Mountatins

The input of litters may affect the biological and biochemical characteristics of the soil of plantation,which will have an important impact on the ecological process of plantation system.Understanding the decomposition characteristics of different types of litter and the difference of their input on the biological and biochemical characteristics of the soil is the basis of establishing a healthy management mode of stand.Therefore,Pinus massoniana,Iiex.purpueaHassk,,Quercus.acutissima,Pinus.massoniana+Iiex.purpueaHas sk,Pinus.massoniana+Quercus.acutissima were selected as the study subjects.Through in-situ litter decomposition experiments,combining with the composition characteristics of surface litter in different types of forest land and controlling the input of the fresh litter.we assessed the characteristics of input and decomposition of leaf litter and the corresponding changes of soil biological and biochemical characteristics in plantations.The results will reveal the mechanism of litter input and decomposition process on soil biochemical characteristics in the five plantations.The main results are as follows:(1)Over one year of litter collection,the annual input of leaf litter of Pinus massoniana was 4238.5±73.8(kg/ha),Iiex.purpueahassk was 1702.5±40.05(kg/ha),Quercus.acutissima was 4607.9±252.6(kg/ha),Pinus.massoniana+ Iiex.purpueaHassk was 5666.4±248.9(kg/ha),Pinus.massoniana+Quercus.acutissim a was 3973.2±166.4(kg/ha).The annual input of leaf litter was Pinus.massoniana+Iiex.purpueaHassk>Quercus.acutissima>Pinus.massoniana>Pinus.massoniana+Que.rcusacutissima>Iiex.pur pueahassk.(2)After one year's decomposition,the order of loss rate from five litter treatments was as follows: Iiex.purpueaHassk>Quercus.acutissima>Pinus.massoniana + Iiex.PurpueaHassk>Pinusmassoniana+Quercusacutissima>Pinus massoniana.Tesults of exponential regression(Olson model)showed that the 95% decay time for litter of Pinus.massoniana,Iiex.purpueaHassk,Quercus.acutissima,Pinus.massoniana+Iiex.purpueaHassk and Pinus.massoniana+Quercus.acutissima were 11.06,5.78,7.93,8.23 and 10.90 year,respectively;while the 50% decay time for them were 2.59,1.27,1.77,1.86 and 2.44 year,respectively.The mixture of Pinus massoniana and Iiex.purpueaHassk promoted the decomposition of leaf litter,while the mixture of Pinus.massoniana and Quercus.acutissima had no significant effect on the decomposition rate of leaf litter.(3)During the decomposition process,the carbon and potassium concentration of leaf litter in five treatments decreased gradually,while the nitrogen concentration first increased and then decreased.The carbon and potassium elements of leaf litter were in a net release state,and the nitrogen elements of leaf litter were enriched first and then released,except for Iiex.purpueaHassk.The C/N value of leaf litter first decreased and then increased,and the C/P value decreased gradually,while the N/P value did not change significantly during the decomposition process.Compared with the expected values,the mixture of Pinus.massoniana and Iiex.purpueaHassk promoted the rate of litter decomposition and the release of carbon pHospHorus and potassium.The mixture of Pinus.massoniana and Quercus.acutissima has no significant effect on decomposition rate of leaf litter at the early stage of decomposition,but a weak inhibition effect on decomposition rate of Quercus.acutissima at the late stage of decomposition.(4)Compared with the removed litter of soil,the pH,organic carbon,total nitrogen,total potassium,alkali-hydrolyzed nitrogen and available potassium in the soil with litter were relatively high,but there was no significant difference of total phosphorus and available phosphorus.The activities of urease,invertase and cellulase are relatively high,the activities of phosphatase are relatively low,and the effects of peroxidase has no significant different;Soil C/N,C/P and N/P were not significantly affected by litter input.During the decomposition,soil MBC and MBN increased significantly(except for the pure forest of Iiex.purpueaHassk),while MBC/MBN had no certain response by litter input.In addition,Gram-positive bacteria,fungi and mycorrhizal fungi were relatively higher with litter input,while the content of eukaryotes and actinomycetes was relatively lower in litter input.(5)Total phosphorus,total potassium,sucrase,peroxidase and urease in pure Pinus.massoniana forest soil;pH,cellulase,phosphatase,peroxidase and MBN in pureforest of Iiex.purpueaHassk forest soil;soil organic carbon,total nitrogen,total potassium,hydrolytic nitrogen,cellulase,peroxidase and urease in pure Quercus acutissima forest soil;pH,organic carbon,total nitrogen and hydrolytic nitrogen,cellulase and MNC in Pinus.massoniana+Iiex.purpueaHassk forest soil;Total potassium,hydrolyzed nitrogen,available potassium,cellulase activity,pHospHatase activity,peroxidase activity and MBC content in Pinus.massoniana+ Quercus-acutissima forest soil were positively correlated with the C,N,P and K nutrient input of leaf litter.In addition,during the incubation,the correlation between soil biochemical characteristics and nutrient concentration can vary in the five studied plantations.In conclusion,the input of leaf litter can effectively improve the soil nutrient content of plantation.There is a positive correlation between soil biochemical characteristics and nutrient input of litter.However,the diverse initial soil fertility and litter stock in the five plantations would have varying effects on the litter decomposition rate and nutrient cycling in situ;related problems and mechanisms need to be further study.