The Research Of Soil Microbial Biomass Nitrogen,Soluble Nitrogen And Labile Organic Carbon In Typical Native Broad-Leaved Plantations In Southern Subtropical China

This research chooses Fubo Forest farm in Guangxi Pingxiang as pilot sites, selects four typical subtropical native broadleaved plantations including, Castanopsis hystrix, Mytilaria laosensis, Michelia macclurel, Paramichelia bailonii which have similar site conditions and stand age as objects and in comparison with the 7-year-old Eucalyptus robusta plantation, studying the diffirents soil layers of(0-20cm,20-40cm and 40-60cm) soil microbial biomass nitrogen, soluble nitrogen (free amino acid, nitrate nitrogen and ammonium nitrogen), labile organic carbon characteristics, The study shows that:The content of 5 kinds of artificial forest soil microbial biomass nitrogen, free amino acid and ammonium nitrogen has obvious vertical distribution pattern decreased with the increasing of soil depth, but there was no significant difference of soil nitrate nitrogen content in different soil layers (p>0.05); 4 species of native broad-leaved plantation in 0-20cm soil layer, soil microbial biomass the nitrogen content is higher than that of Eucalyptus plantation, and the content of free amino acids in the soil of Eucalyptus plantation soil showed higher than that of artificial broad-leaved forest local trend, but there is no obvious regularity between Eucalyptus plantation soil ammonium nitrogen content and indigenous broadleaf plantations, soil artificial broad-leaved forest in local effective nitrogen reserves and the supply side is not necessarily better than Eucalyptus plantation. Soil microbial biomass nitrogen, free amino acids and ammonium nitrogen and soil pH values showed a highly significant negative correlation (p< 0.01), and with the contents of soil organic matter showing significant or extremely significant correlation (p< 0.05), showed that the soil pH value and organic matter are two of the main factors of different tree species plantation in soil microbial biomass nitrogen, free amino acids and ammonium nitrogen content.The vertical distribution of the obvious characteristics of 5 species of artificial soil labile organic carbon content; but the labile of soil organic carbon to total organic carbon ratio did not show significantly decreased with soil depth and the trend of the labile organic carbon fractions in the total organic carbon ratio are easily oxidized carbon (EOC)> microbial biomass carbon (MBC)> soluble organic carbon (SOC); 0-20cm soil layer in various soil active organic carbon of 5 stand points were significantly higher than those in 20-40cm and 40～60 soil; there are little differences between the 4 indigenous broadleaf plantations of Eucalyptus Plantation in the active soil organic carbon fractions above; a significantly positive correlation between soil MBC, SOC, EOC content and soil porosity, available potassium (p<0.05), there were significant and the soil bulk density, pH value (p<0.05) or significant negative correlation (p<0.01), total nitrogen and soil water content,,total phosphorus,total potassium, the correlation is not significant.