Influence Of Different Forest Management Regimes On Soil Enzyme Activity And Microorganism In Natural Secondary Forests In Northeast China

Because of the great economical and ecological values in natural secondary forests, choose a reasonable management regime may have vast importance to forest multi-target management. In this study, four Korean pine (Pinus koraiensis) natural secondary forests representing different management regime (traditional forest management regime (FM1), target tree forest management regime (FM2), tree species adjusting forest management regime (FM3), and undisturbed forest management regime (FM4), respectively) were selected in Danqinghe Forestry Farm located in Harbin, Heilongjiang Province. The differences of soil enzyme activity, microbial quantity, microbial biomass, and microbial functional diversity among four different forests were studied, and the influent effect of soil chemical properties to these indexs were further explored. Results showed:(1) Soil enzyme activity (sucrose, urease, protease, alkaline phosphatase and catalase), microbial quantity (bacteria, actinobacillus, fungi and total), and microbial biomass (microbial biomass carbon, microbial biomass nitrogen, microbial biomass phosphorus) are all significantly higher in the soil depth of 0-20cm than in 20-40cm.(2) In the soil depth of 0-20cm, the five soil enzyme activities of four management regimes were all as follow:FM1>FM2-FM3-FM4. In the soil depth of 20-40cm, sucrose were as follow:FM1=FM2-FM3>FM4, proteaseand alkaline phosphatase activity are also as follow: FM1>FM2=FM3-FM4. And urease activity in FM1 was significantly higher than in FM3 and FM4 (p<0.05), but no significant difference between FM1 and FM2 (p>0.05). Catalase activity in FM1 and FM3 (no significant difference between the two) was significantly higher than in FM2 and FM4 (no significant difference between the two) (p<0.05).(3) The quantity of three soil microorganism was:bacteria> actinomyces> fungi. The quantity of bacteria and total microorganism of four management regimes in the soil depth of both 0-20cm and 20-40cm were all as follow:FM4>FM1-FM2-FM3, and the quantity of fungi were as follow: FM1>FM2-FM3-FM4. The quantity of actinomyces was no significant difference in the soil depth of 0-20cm among four different forests (p>0.05), but in the soil depth of 20-40cm, FM4 has the highest quantity of actinomyces.(4) In the soil depth of 0-20cm, soil microbial biomass carbon were as follow:FM1>FM2=FM3=FM4. But, in the depth of 20-40cm, it was as follow: FM1>FM2-FM3>FM4. And in both the two soil depth, soil microbial biomass nitrogen were as follow:FM1>FM3>FM2>FM4. In the soil depth of 0-20cm, FM1 has the significantly highest soil microbial biomass phosphorus (p<0.05), FM2 also significantly higher than FM4 (p<0.05), but there was no significant difference between FM2 and FM3 (also between FM3 and FM4) (p<0.05).(5) The carbon source utilization of soil microbial communities in FM1 was significantly lower than those in other three forests, and it was the highest in FM4, while there are no significant difference between soil carbon source utilization in FM2 and FM3. Soil microbial functional diversity has an order of FM4> FM2= FM3> FM1.(6) Soil organic carbon was the main factor affecting soil enzyme activity, microbial quantity, and microbial biomass. Total nitrogen was also one of the main factors affecting urease and protease activity, the same as soil microbial biomass carbon and nitrogen. Total phosphorus was also one of the main factor affecting alkaline phosphatase activity and microbial biomass phosphorus. Available nitrogen was one of the main factors affecting the quantity of bacteria and soil microbial biomass nitrogen. Soil pH mainly affected the quantity of fungi. Available nitrogen, available potassium, available phosphorus, soil organic carbon and carbon-nitrogen ratio had important effect on the carbon source utilization of soil microbial communities.(7) Comprehensive assessment of soil quality in four management regimes showed:FM1 was the best, FM4 was the worest, FM2 and FM3 were between the two, and FM2 was slightly better than FM3.Compared with the other three forest management regimes, FM1 was propitious to enhance soil quality, but it was not conducive to bacterial growth, and it even can reduce the carbon utilization and functional diversity of soil microorganism. FM4 had the highest bacterial quantity and functional diversity. FM2 and FM3 were between the two in general.