Distribution Characteristics Of Soil Active Organic Carbon In Black Soil Region

Based on the black soil area at different growth stages and different soil keep forest type soil active organic carbon variation and the degree of recovery, and different water ratio, extraction agent type and extraction temperature under the condition of different land use types of soil dissolved organic carbon content of and for scientific evaluation of black soil zone of vegetation recovery and soil and water conservation forest influence on soil quality in the course of building to provide reference. The main results are as follows:Soil labile organic carbon from Larch plantations of different ages in typical black soil region were studied by measuring and analyzing soil water-soluble organic carbon (WOC), soil microbial biomass carbon(MBC) and particulate organic carbon (POC) and et al. Results showed that the concentration of soil WOC, MBC and POC varied from 0.49～0.61g/kg, 32.38～51.90mg/kg,1.78～4.17g/kg respectively, and the concentration of POC and proportion of total soil organic carbon were larger than the others; The concentration of soil labile organic carbon in Larch plantations increased firstly, and then reduced with increased standing age, approaching the levels of undisturbed black soil after 30 yeas old. Larch plantations can improve the concentration and quality of soil labile organic carbon to some extent, reaching and even exceeding the levels of undisturbed black soil.Aiming to confirm the effects of extraction methods on the concentration of topsoil dissolved organic carbon (DOC) and select suitable conditions for extracting DOC of black soil, topsoil samples in the depth of 0—10 cm collected from four land use types, including Dahurian larch plantation, natural grassland, arable land and natural secondary forest from black soil, were used by measuring the concentration of DOC extracted with different water-to-soil ratios, extractants and temperatures. Results showed that:1) the concentration of DOC extracted from topsoil presented a positive linear relationship significant with water-to-soil ratio (R2 ranged in 0.82 — 0.98). The differences of DOC concentrations in topsoil of four land use types were significant (P<0.05) when the water-to-soil ratio was 40:1 with a peak value in the natural secondary forest. It was 1.16,1.88 and 1.61 times of that of larch plantation, natural grassland and arable land, respectively.2) The type of soil extractant also had influence on concentration of DOC in topsoil to some degree. DOC extracted with deionized water resulted in a higher concentration compared with other conditions.3) The extraction concentration of DOC under four land use types did not show a significant regularity until the temperature increased to 70 ℃ (P<0.05). It can propose a relatively appropriate extraction procedure for DOC concentration from topsoil, and which can reflect its differences among the land use patterns of black soil:field-moist soil extracted with deionized water at a 1:40 water- to-soil ratio.The distribution characteristics of soil active organic carbon and the relation with soil erodibility from water conservation forest such as Manchurian Ash (Fraxinus mandshurica), Dahurian Larch(Larix gmelini),Scots Pine(Pinus sylvestris var.mongolica) and abandoned land in the black soil area was studied by measring water-soluble organic carbon (WOC), readily oxidizable carbon (ROC),particulate organic carbon (POC) and indexes of soil erodibility. Results show that:(1) the amounts of soil ROC and POC among forests were similar; Soil WOC in the abandoned land is higher than the other types.(2) ROC and POC in the soil and water conservation forest appeared a descending trend in the soil depth of 0-30cm.(3) There is significant correlation among ROC,POC and TOC.(4) The order of soil erodibility was Manchurian Ash<Dahurian Larch<Scots Pine<abandoned land.(5) ROC and POC were significantly positive correlation with MWD;WOC was significantly negative correlation with PA0.25, PAD0.25, Soil saturation degree and water stability index, but the value of R2 is less than WOC/TOC. effect of soil and water conservation forests can improve soil active organic carbon and reduce soil erodibility, especialy Manchurian Ash; WOC/TOC can be used as indicator to predict and evaluate soil erodibility.