Effect Of Harvest And Land Uses On Soil Labile Organic Carbon In Natural Second Growth Of Northeast China

Reponses of soil labile organic carbon 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 different cuttings. After a growing season, changes of soil labile organic carbon were measured. Meanwhile, second growth, 20-year larch forest(Larix gmelinii) planted after cutting(plantation), and 20-year reclaimed cropland(cropland) were chosen as comparison measurement. The results showed:After a growing season, the potential mineralization rate and cumulative mineralized amount of soil organic carbon (SOC) from different plots range as follow: partial cut I (50% of the stand volume removed), cropland (farming after clear cutting), partial cut II (25% of the stand volume removed), control(uncut), afforestation (forestation after clear cutting). There are no significant differences among different harvest methods. The amount of soil readily oxidation carbon (ROC) of partial cut I in all the three soil horizons is significantly higher than control. The amount of soil microbial biomass carbon (MBC) of partial cut I in the 0-10 cm and 10-20 cm soil horizons is significantly higher than control; in the 0-10 cm soil horizon, the amount of MBC of afforestation is significantly lower than control. The amount of water-soluble organic carbon (WSOC) of partial cut I in the 0-10 cm and 10-20 cm soil horizons is significantly higher than control, in the 20-30 cm soil horizon, the amount of WSOC of afforestation is significantly lower than control. The percentage of all forms of labile organic carbon in soil organic carbon ranges highest in partial cut I, and lowest in afforestation.The potential mineralization rate and cumulative mineralized amount of SOC from second growth, plantation and cropland range as follow: second growth, plantation, cropland in the 0-10 cm soil horizon, second growth, cropland, plantation in the 10-20 cm soil horizon, and second growth, plantation, cropland in the 20-30 cm soil horizon. There are no significant differences among different land uses in all three soil horizons. The amount of ROC of second growth in 0-10 cm soil horizon is significantly higher than plantation and cropland. The amount of MBC of second growth in 0-10 cm soil horizon is significantly higher than plantation and cropland, and the plantation is significantly higher than cropland too, in 10-20 cm soil horizon, second growth and cropland are significantly higher than plantation. The amount of WSOC of second growth in 0-10 cm soil horizon is significantly higher than plantation and cropland, in the 10-30 cm soil horizon, second growth is higher than plantation and cropland, but there are no significant differences among different land uses. The percentage of all forms of labile organic carbon in soil organic carbon ranges highest in second growth and cropland. The amount of mineralized carbon(MC), ROC, MBC and WSOC show significant correlation. And the amount of soil labile organic carbon, SOC and total nitrogen(TN) show significant correlation too.It suggests that after partial cut with greater intensity, the amount of soil labile organic carbon will increase, but after forestation following clear cutting it will decrease in the second growth of northeast China. But as the ecosystem of plantation recovers year by year, its labile organic carbon of soil is accumulated. As natural second growth was turned to cropland and its soil is disrupted constantly, the amount of its labile organic carbon of soil reduces. After 20 years, the amount of labile organic carbon in natural second growth and plantation is higher than that in cropland.