Research On Characteristic Of Soil Respiration In Different Managed Forests Of Phyllostachy Edulis, Mufu Mountain,Southern Hubei, China

Soil respiration as the second largest carbon flux on earth, is the primary way of carbonexchange between terrestrial ecosystem and atmosphesic. Annual CO₂release from soilrespiation is estimated to be98±12PgC, more than10times of that from human activity,therefore, small change in soil respiration can lead a singnificant impact on atmosphereic CO₂concentration. However, soil respiration is spatial-temporal and regional-vegetationalheterogeneity. Thus enhangcing research in soil respiration of different regions and vegetationtypes is of great singificance to increase accuracy in estimation soil respiration on a large scale.Bamboo forest is one of critical forest types in south China, with an area of5.38millionhectare and more than70%was moso bamboo（Phyllostachy edulis）forest. As predicted,carbon storage in bamboo forest accounts for about11%of total forest carbon storage and itshows a trend of increase with the expansion of growing areas. Althrough the global forest areais reducing at present, bamboo forest area is increasing at the speed of3%per year, thus itplays an increasingly impotant role in global carbon balance, especially under the condition ofglobal warming. Many researches have been carried out on above-ground carbon process inbamboo ecosystem, but below-ground carbon process is still full of uncertainties, especially indifferent managmed bamboo forests. Application of management is one of the most importantmeasures to improve yield in moso bamboo forest, thus, in this research, pure moso bambooforest with no management was selected as contro（Ⅰ）and managements of reclamation（Ⅱ）,herbicide application（Ⅲ）and grass-chopping（Ⅳ）forests were selected as research stands. TheCO₂release from soil was monitored by Li-8100, with estimation of annual growth, the carbonsink or source was determined. The main results were as follows:（1）The impact factors of soil respiration showed significantly monthly or seasonalchanges. Soil temperature and moisture was highest in summer and lowest in winter, but no significant difference occured among different stands; leaf area index（LAI）was featured byone-peak curve with peak in August and low bottom in March, and LAI of stand Ⅰ andⅣwas remarkable lower than that of Ⅱa ndⅢ; SOM was highest in spring and lowest inautumn, and stand Ⅲ was significantly higher than other stands; Meanwhile, litter input waslowest in summer and highest in winter, amounting to significant difference; additionally,monthly and seasonal changes was also found in root biomass, fine root biomass, however,stand Ⅲ was significantly lower than Ⅰ, Ⅱ, Ⅳ.（2）Daily changes of total soil respiration, root respiration litter respiration and mineralrespiration was feastured by one-peak or two-peak curve with peaking in hour12:00,14:00and16:00, but not entirely in sync with changes in total soil respiration.（3）As affected by soil temperature, moiture and management, total soil respiration andsource components were singinicantly characterized by seasonal changes with highest insummer and lowest in winter. Compared with control stand, reclamation, application ofherbcides and herb-chopping could increase total soil respiration, which was high-lighted byreclamation stand of significantly higher than control stand. Reclamation and application ofherbcides could significantly increase root respiration while herb-chopping decreased rootrespiration, but not signicantly. Contribution of root respiration to total soil respiratin was30%on a year scale; litter respiration of managed stands was lightly lower than control stand and itscontribution to total soil respiration was20%; reclamation and herb-chopping weresignificantly increase mineral respiraiton, however, application of herbcides remarkable reducemineral respiration, and its contibution to total soil respiration was nearly50%.（4）Total soil respiration and source components were exponentially related with soiltemperature and linearly related with soil moisture. The correlation coefficients of total soilrepsiratin and mineral respiration were higher than thoes of root respiration and litterrespiration. Reclamation and application of herbcides increased soil temperature sensitivitymeanwhile herb-chopping decreased soil temperature sensitivity. Annual total soil respirationwas positively linearly related with annual LAI, NEP, litter input, root biomass and fine root biomass. Annual root respiration was positively linearly related with annual LAI, NEP andSOM, but negatively linearly related with root biomass and fine root biomass. Litter respirationwas positively related with annual litter biomass, and mineral respiration was negativelyrelated with SOM content. Combinational model of soil temperature and soil moisture canbetter predict the dynamic changes of soil respiration and source components.（5）Annual biomass growth of on-year moso bamboo of each stand were1131.32,1353.07,1155.38and1578.40g·m^-2·a^-1; CO₂release from soil respiration were884.38,042.83,904.05and910.10g C·m^-2·a^-1and net annual ecosystem carbon sequestration were339.01,414.86,451.73and372.99g C·m^-2·a^-1, which indicated that, compared with controlstand, reclamation, application of herbcides and herb-chopping could increase annual biomassgrowth, CO₂release and net annual ecosystem carbon sequestration.（6）This research showed that on-year moso bamboo forest played a role of carbon sink,and reclamation, application of herbcides and herb-chopping could increase the ability ofcarbon sequestration, application of herbcides was best, which was a more reasonablemanagment in research area. Application of herbcides could not only increase above biomass,also increase soil SOM content and carbon storage. However, effect of herbcides on soilmicrobial diversity and soil chemical and phisycal properties were needed to further research.