Effects Of Forest Thinning And Pruning On Soil Respiration And Microbial Community Structure

Soil is the biggest carbon pool of land-based ecosystems and plays an important part of forest sustainable development. Soil respiration is very important to global carbon balance and the greenhouse effect. Soil microbial community structure plays a crucial role in maintaining plant growth,soil fertility,and the material energy metabolism and circulation.The Chinese fir is the dominant tree species of subtropical area in China. It occupies a very important place in forestry production and ecology construction in southern China.The study of effects of thinning and pruning on soil respiration and soil microbial community structure in Chinese fir plantation can provide the theoretical basis and technical support to people,in order to formulate appropriate management measures and maximize the ability of forest carbon sequestration in production practice.In this paper,we took Chinese fir plantation in Huitong county as research project.The seasonal variation characteristic of soil respiration,the response of soil respiration and soil microbial community structure to soil physical and chemical properties and environmental factors, and the effects of thinning and pruning on soil respiration and soil microbial community structure had been studied.The results show that:(1) The seasonal variation of the Chinese fir plantation soil respiration rendered as a single peak curve as a whole.The seasonal variation of soil respiration on different forest management measures had similar trends, reaching the peak of soil respiration in the summer months of July,August and September, and the minimum value appeared in February with lower temperatures.The results showed the value of soil respiration of different forest management measures from high to low was pruning,thinning and control,which were 1.76μmol·m-2·s-1,1.65μmol·m-2·s-1 and 1.58μmol·m-2·s-1 on average.(2) Temperature was the most important factor affecting soil respiration.The soil respiration of all these three measures had extremely significantly positive correlation with soil temperature(p<0.01),which can explain over 90% of the variations of soil respiration.The soil water content,soil pH,soil microbial biomass carbon(MBC),soil sucrose,amylase and β-D-glucosidase had no significant relation with soil respiration.The biomass of bacteria, fungi and actinomycetes was negative related with soil respiration both in control and thinning plot,while it was positive related with soil respiration in pruning plot.(3) Thinning and pruning had no significant effect on soil temperature, soil water content and soil pH,and these two measures decreased sucrose and β-D-glucosidase activity.Thinning decreased amylase activity,while pruning increased its activity. The monthly average soil respiration had no significant difference among different forest management measures.Soil respiration markedly increased in January,March and April both in thinning and pruning plot. Soil respiration markedly decreased in July, September and November in thinning plot,however.(4) Soil microbial biomass had no significant correlation with soil temperature and soil pH,while it positively related with soil water content,MBC,total carbon,total nitrogen and carbon nitrogen ratio.Thinning markedly decreased soil MBC,total carbon and total nitrogen.Pruning decreased soil MBC but increased soil total carbon and total nitrogen.Thinning and pruning deceased the biomass of soil bacteria, fungi, actinomycetes,gram-positive bacteria and gram-negative bacteria.