Effects Of Forest Structure On Soil Microbial Diversity

China ’s plantation area ranks first in the world,062million hectares ofplantation area, plantation production is not high, the dysfunction of ecosystemservices. Over the years, the business objectives of the plantation just to maximizeaccess to wood, seldom consider the ecological functions of biodiversity，so that theplantation of low productivity, species in a single, the system is simple(unreasonable)， Lead to reduced biodiversity, soil fertility decline and biologicalproduction decline, a serious impact on the sustainable management of theplantation.This paper selected two typical poplar plantation as the research object base inthe northern part of China’s Jiangsu Province, through the study of silviculturalmeasures (to create a mixed forest, create a different density design) the plantationsoil quality test analysis comparing different nurturing measures changes differencesbetween poplar plantation soil fertility， soil microbial diversity. The main researchresults were shown as follows:（1）The effect of planting density on soil physical and chemical propertieswere no significant， Judging from the impact of planting density woodland soilorganic matter, total nitrogen, available nitrogen, available phosphorus and othernutrients content,6m×6m and5m×5m were the more suitable planting density forbetter soil structure， nutrient adequacy.The effect of mixed plantation on soil physical and chemical properties weresignificant， poplar×Bauhinia mixed forest was the more suitable mixed plantationfor better soil structure and nutrient adequacy，according by the effect of soil organicmatter, total nitrogen, available nitrogen, available phosphorus and other nutrientscontent(P<0.05).effects of different silvicultural measures on soil physical and chemicalproperties: there were significant difference of soil physical and chemical propertiesunder soil depth and seasonal changes, soil depth and seasonal changes affect eachtreatment soil physical and chemical properties has changed significantly, and soilnutrients in summer was higher than winter, the top soil nutrients was significantlyhigher than the underlying soil.（2）Study microbial functional diversity by Biolog method showed that themicrobial metabolic activity in summer than in winter.The mixed forest microbial activity and the Shannon diversity index werehigher than pure forest; there was no significant difference of microbial activity andShannon diversity index under different stand density. The carbon utilizationprincipal component analysis showed that the mixed forest soil microbial metabolic capacity of carbohydrates, amino acids, polymers, were higher than the soil of pureforest; there was no significant difference of soil microbial metabolic capacity underdifferent stand density.The experimental results showed that the seasonal variation and the depthplayed an important role in microbial functional diversity of the whole process.create a mixed forest will produce a certain influence in microbial functionaldiversity, if plantations density design is too large or too small， it can also affectthe microbial community structure.（3）PCR-DGGE analysis of soil microbial genetic diversity showed that, usingdenaturant range of45%to65%, voltage75V, temperature60℃, electrophoresistime16h DGGE in experiments， it would be able to get a better effect ofelectrophoresis.UPGMA cluster analysis showed that soil bacterial community structure ofdifferent density and different tree species in the upper soil (0~10cm) and middle (10~20cm) were similar, but there was a significant difference with the subsoil (20~40cm). the Soil microbial bacterial community under Different tree speciesprocessing can be divided into two categories: Poplar×Bauhinia mixed forest andpure poplar, and the similarity of the two major groups was less than50%, becauseof silvicultural measures， mixed forest and pure poplar showed a significantdifference, This results were coincided with the Biolog method; between differentdensity poplar forest topsoil density of5m×5m is closer to3m×8m density forest,there were a difference with the6m×6m density forest, overall, the similarity soilbacterial community between the three different stand density reached about70%.（4）Correlation analysis of soil physical and chemical properties and soilmicrobial diversity index， Found that there is a significant negative linearcorrelation between soil bulk density and soil microbial diversity index， there is nosignificant linear relationship between soil porosity, soil pH and microbial diversity,there is a significant positive linear correlation between soil organic matter, soiltotal N, available phosphorus and soil microbial diversity index.