Effect Of Harvest And Land Uses On Soil Microbial Biomass Carbon And Nitrogen In Natural Secondary Forest Of Northeast China

Reponses of soil microbial biomass carbon and nitrogen to different harvest methods and land use patterns after cutting were measured in Maoershan Experimental Forest Farm of Northeast Forestry University. Second shaw growth was chosen to be processed in four treatments (afforestation (forestation after clear cutting), cropland (farming after clear cutting), partial cutâ… (50% of the stand volume removed), partial cutâ…¡(25% of the stand volume removed)). In two consecutive years, dynamic of soil microbial biomass carbon and nitrogen were measured. The results showed:The soil microbial biomass carbon (SMBC) from different treatments range as follow: afforestation, partial cutâ… , cropland, partial cutâ…¡, control(uncut). And the soil microbial biomass nitrogen (SMBN) range as follow:afforestation, cropland, partial cutâ… , partial cutâ…¡, control. The amounts of soil microbial biomass carbon and nitrogen in the 0-10 cm horizon from different treatments is significantly higher than that in 10-20 cm soil horizon; SMBC contents in 0-10cm and 10-20cm soil horizons varied respectively from 208.36 to 2284.51mg.kg-1 and from 75.79 to 980.72mg.kg-1. SMBN contents in 0-10cm and 10-20cm soil horizons ranged from 66.97 to 325.34mg.kg-1 and from 16.11 to 126.59mg.kg-1 respectively. The contents of SMBC and SMBN showed obvious seasonal variation, high in spring and autumn, and low in summer.The soil microbial quotient from different treatments range as follow:control, partial cutâ…¡, afforestation, cropland, partial cutâ… . There are no significant differences among different harvest methods. The microbial quotient varied from 1.12 to 4.47. There are also no significant differences between 0-10cm soil horizon and 10-20cm soil horizon. After woods harvested, there are a large number of logging slash in the forest land, so that soil organic carbon(SOC) and SMBC increased rapidly. But soil microbial quotient decreased, and soil degrade.SOC, total nitrogen, nitrate, ammonium, total phosphorus, available phosphorus, total potassium, pH, soil temperature and moisture in the 0-10cm soil horizons were higher significantly than that in the 10-20cm soil horizons. SOC, total nitrogen, nitrate, ammonium, total phosphorus, available phosphorus and total potassium showed significant seasonal dynamics, high in spring and autumn, and low in summer.Soil organic carbon and total nitrogen correlated significantly with SMBC and SMBN. It shows SMBC and SMBN are sensitive indicators of soil organic carbon and nutrient. Soil moisture and total phosphorus can affect significantly SMBC and SMBN. But available phosphorus, total potassium, soil moisture and pH have no correlations with SMBC and SMBN.After harvesting, SMBC and SMBN showed obvious seasonal variation. SOC, total nitrogen, total phosphorus and soil moisture had important effects on SMBC and SMBN. Soil microbial biomass in the plots of afforestation,cropland and partial cut I increased in short-term, but the quality of soil decreased.