Effect Of Gap Size On Soil Labile Organic Carbon In Three Types Of Pinus Koraiensis Mixed Forest

Forest gap is one of wide range interference phenomena in forest landscape pattern. The formation of gap changed the light and water and heat conditions of the forest community’s microhabitat, resulting in the differences of soil nutrients in forest. Small, medium and large gaps in three representative forest types Tilia amurensis-Pinus koraiensis mixed forest (TP), Picea sp.-Abies nephlolepis-Pinus koraiensis mixed forest (PAP), Betula costata-Pinus koraiensis mixed forest (BP) were selected as experimental plots, and respectively closed stand around each gap was set up as the control in Xiaoxing’an Mountains of Northeast China. Soil organic carbon(SOC), microbial biomass carbon(MBC), soil dissolve organic carbon(DOC), soil carbon mineralization content(CO2-C), total nitrogen(TN) at the depth of0-10cm in the different size of forest gaps and their controls of various forest types was determined June to September,2012, aims to illustrate the gap size for different types of natural Pinus koraiensis mixed forest changes of soil active organic carbon, The results are as follows:(1) Gap size have no significant effect on the SOC, MBC, DOC in three kinds of natural Korean pine mixed forest. Gap size have significant effect on the CO2-C only in TP, gap size have significant effect on TN only in PAP, which were no significant in other forest types. Month have significant effect on SOC, MBC, DOC, TN in three kinds of natural Korean pine mixed forest, which have significant effect on CO2-C in PAP, have no significant in TP and BP.(2) Soil labile organic carbon have same trend in PAP and BP, SOC and DOC were in the order of large gap>small gap>medium gap; MBC was medium gap>large gap>small gap; CO2-C and TN were large gap>medium gap>small gap. SOC, TN were in order of medium gap>small gap>large gap in TP, MBC was small gap>large gap>medium gap in TP. DOC and CO2-C were large gap>medium gap>small gap in TP. SOC, DOC, CO2-C were higher in the gap than the closed stand in three kinds of forest; MBC have the same trend in TP and PAP, but was in the opposite order in BP; TN was lower in the gap than the closed stand in TP and BP. but was in the opposite order in PAP.(3) SOC, MBC, DOC content in the different forest types were showed that PAP>TP>BP; CO2-C was showed that BP>TP>PAP; TN was showed that TP>PAP>BP. Soil labile organic carbon was in order of MBC>DOC>CO2-C in PAP and BP, MBC> CO2-C>DOC in TP.(4) SOC, DOC, CO2-C, MBC, TN mostly show unimodal form along with the change of month in three kinds of natural Korean pine mixed forests, peaked in July or August, but MBC peaked in June in TP and PAP, TN peaked in September in PAP.