The Microbial Mechanism Of Understory Removal Affects On Moso Bamboo Litter Various Phosphorus Release

Phyllostachys edulis is an important non-wood economic forest species in south China.Due to the unreasonable management for a long time,the land capacity of some bamboo forests has declined seriously.How to maintain and improve the long-term productivity of bamboo forests is an urgent problem to be solved by forestry departments.Phosphorus is the main nutrient limiting factor of bamboo growing,and the soil phosphorus mainly comes from the decomposition of plant litter.Currently,the release rate of nutrients in the decomposition process of litters has attracted wide attention.However,studies on the release status of phosphorus in different forms in the decomposition process of litters are still lacking.In addition,as an important part of the forest ecosystem,undergrowth is often removed（i.e.cutting shrubs and clearing weeds）in order to reduce competition for nutrients and water between undergrowth and target species.There is a close relationship between aboveground plants and subterranean organisms in an ecosystem,which plays an important role in driving the ecosystem.The removal of undergrowth vegetation may change the structure of soil microbial community and affect the release process of different forms of phosphorus from litters.Soil microorganisms may adapt to the removal of undergrowth vegetation within a certain threshold and thus have no significant influence on the release of phosphorus from different forms of litter decomposition.However,the relevant hypothesis still needs to be verified by reasonable experiments,and the relevant studies are relatively scarce.This research choice of central Asian tropical bamboo plantation as the research object,to carry out the undergrowth to eliminate the bamboo litter decomposition studies the influence of different forms of phosphorus release,monitoring of soil physical and chemical properties,soil microbial biomass and community composition,litter decomposition rate and different forms of phosphorus release rate and other indicators,analysis of the undergrowth driven by eliminating soil microbial community structure on litter decomposition regulatory mechanism of different forms of phosphorus release.The results of this study can provide a new way to explore the return of phosphorus in the manmade bamboo plantation in the central subtropical region,provide a new way to the return of phosphorus in the soil,and provide scientific support for the removal of undergrowth vegetation as an effective artificial management measure.The preliminary results are as follows:（1）Removal of undergrowth vegetation significantly affected the physical and chemical properties of soil during the decomposition of litters,and the effect was seasonal.Compared with the control group,the removal of undergrowth vegetation significantly reduced the content of ammonia nitrogen（NH₄⁺-N）,total phosphorus（TP）and p H value of soil.However,soil contents of total nitrogen（TN）,nitrate nitrogen（NO₃^--N）,available phosphorus（AP）and organic carbon（SOC）were significantly increased.The reduction of SWC in summer after removing undergrowth was significantly smaller than that in the other three seasons.In the decomposition experiment,SWC decreased by 3.25%on average.The average decrease in p H value was 0.38.The difference of NH₄⁺-N content in soil was 3.15mg/kg at the maximum and 0.1 mg/kg at the minimum,with an average decrease of 1.76mg/kg.Soil TP content was significantly reduced by 0.07 g/kg on average.Compared with the control group,the average NO₃^--N content of undergrowth vegetation was significantly increased by 1.1 mg/kg,the AP increment was 2.35 mg/kg,and the SOC increment was about 3.33 g/kg.（2）The removal of undergrowth vegetation significantly changed the structure of soil microbial community of bamboo forest.Specifically,it increased the content of soil fungi and reduced the content of soil bacteria.Thus,increasing the ratio of fungi to bacteria.It was concluded that the increase of fungus content was mainly due to the increase of available P content.The decrease of bacteria content in understory vegetation removal was mainly attributed to the increase of available P and total N content,as well as the decrease of total P content.（3）Understory vegetation removal significantly reduced the decomposition rate of litters and inhibited the release of residual P,thus hindering the rate of P return to the soil ecosystem.The inhabitation of understory vegetation removal on P cycle may be mainly attributed to the increase of fungi content and the decrease of arbuscular mycorrhizal fungi and bacteria（i15:0）content.（4）In the decomposition process of P.edulis litters,the residual P was be enriched with decomposition,which proved that the enrichment of P was attributed to the residual P in the soil microbes during the litter decomposition period.This experimental result provides an important reference for further research on the mechanism of the decomposition process of litters driven by microorganisms.Based on the above results,it is suggested that undergrowth shrubs and herbaceous plants should be preserved in the management of P.edulis plantation.