科尔沁沙地半固定沙丘不同坡位土壤C,N特征

目的]研究沙丘不同坡位土壤碳氮的分布特征,旨在探索沙丘不同坡位植被演替机制。方法]选取高于5m的半固定沙丘,沿主要风向于坡底、坡中、坡顶和背风坡设置样点,对土壤容重、土壤总有机碳含量和土壤总氮含量进行测定,并计算碳氮比、碳氮密度和碳氮储量。结果](1)不同坡位土壤碳含量均随深度增加显著降低,主要变异层发生在0—40cm层。不同坡位土壤碳含量在30—40cm层和60—100cm层存在差异。(2)氮含量与容重在不同坡位和不同深度均不存在显著差异性,碳氮比在坡底和坡顶存在显著的垂直差异性,背风坡60—100cm层土壤碳氮比显著高于其它坡位。(3)各坡位土壤碳密度随深度增加显著下降。30—40cm层土壤碳密度存在显著的坡位差异,而土壤氮密度的垂直差异和坡位间差异均不显著。(4)半固定沙丘土壤碳氮储量分别为716.89和94.14kg/m2,不同坡位差异性不显著;碳储量的构成在4种坡位差异较大,而各坡位不同深度土壤氮储量对总储量的贡献差异较小。结论]科尔沁沙地半固定沙丘土壤碳氮含量与密度不同坡位的差异较小,同时各坡位的碳氮均存在显著的垂直差异性,尤其在30—40cm层,变异程度较大,这可能与该层植物根系分布有关。

Soil Carbon and Nitrogen Characteristics of Different Positions of Semi-fixed Dune in Horqin Sandy Land

Objective] To investigate the distribution of soil organic carbon(SOC) and total nitrogen(TN) in different positions of semi-fixed dune in Horqin sandy land, for exploring the vegetation succession mechanism of different dune slope positions.Methods] Soil samples were collected from the bottom of windward slope, mid-slope, top and leeward of semi-fixed dunes with 5 m height, along the direction of prevailing wind. Soil bulk density, SOC and TN contents were measured and then the ratio of carbon/nitrogen(C/N), densities and stocks of SOC and TN were calculated.Results] (1) SOC contents in all 4 positions of the semi-fixed dune were decreased with soil depth and the obvious variation occurred in depth of 0-40 cm, and there were position differences (p<0.05) of SOC contents at depth of 30-40 cm and 60-100 cm; (2) TN contents and bulk density were all insignificantly different among different depths and slope positions. Ratio of C/N showed significant differences between the bottom and top of semi-fixed dunes. The ratio at the depth in leeward from 60 to 100 cm had significantly higher values than others; (3) SOC density decreased significantly with soil depth in all slope positions, and there existed significant differences of SOC density at depth of 30-40 cm among slope positions. No significant differences of nitrogen density were found among dune positions and profile depths; (4) Stocks of SOC and TN were 716.89 and 94.14 kg/m² in semi-fixed dune, respectively. The differences among slope positions were insignificant. However, contribution in each layer of SOC stock to the total stock was different between slope positions while TN was similar in each layer to the total.Conclusion] There were insignificant differences in both contents and densities of SOC and soil nitrogen in semi-fixed dune of Horqin sandy land among dune position, however, contents of SOC and soil nitrogen differed significantly among soil depth in all dune positions, especially at the depth of 30-40 cm, which changed intensely, and this may due to plant root distribution of this depth.