科尔沁草甸湿地土壤碳氮剖面分布及生长季动态特征

采用定位观测的试验方法,于2016年5-10月及2017年8月对科尔沁草甸湿地0~100 cm土层土壤有机碳、全氮剖面分布及生长季动态特征进行了实验分析,旨在为科尔沁草甸湿地保护提供科学指导并为干旱半干旱地区湿地土壤碳氮储量估算提供借鉴。结果表明:1)科尔沁草甸湿地土壤有机碳、全氮含量整体随土层深度下降,0~20 cm土层间下降显著,20 cm以下趋于相对稳定,范围分别为11.9~23.5 g·kg^-1和0.66~1.50 g·kg^-1。2)各土层土壤碳氮含量月间差异显著(全氮40~60 cm土层除外),变化幅度随土层深度先减小后增大;土壤碳氮密度(100 cm)生长季变化大于年际变化,有机碳密度全生长季呈上升趋势,范围为15.44~20.82 kg·m^-2,全氮密度生长初期明显下降,之后趋于相对稳定,范围为1.01~1.16 kg·m^-2。3)土壤有机碳含量与全氮含量呈极显著正相关;植被和水文是影响其分布、变化的关键因子。科尔沁草甸湿地生长季土壤有机碳、全氮密度变化较大,且表现为潜在的碳汇和氮源,但年际间碳汇潜力未充分发挥,本研究建议禁牧力度应加大并增加氮肥投入以提高科尔沁草甸湿地生态系统功能。

Profile distribution and dynamics of soil organic carbon and total nitrogen in the Horqin meadow wetland during the growing season

Wetlands are highly productive ecosystems and serve as an important component of global carbon and nitrogen cycles. To better understand the functions of wetlands, more accurate estimations of soil organic carbon (SOC) and total nitrogen (TN) reserves in these environments are needed. In this study, soil samples were taken down to a depth of 100 cm twice a month from May to October 2016 and in August 2017 to analyze the profile distributions and dynamics of SOC and TN in the Horqin meadow wetland. The contents of SOC and TN, above- and below-ground biomass, and other soil physicochemical properties such as soil pH were determined. Our results showed that: 1) Both SOC and TN contents decreased significantly with soil depth in the surface layer (0-20 cm), but tended to remain relatively stable in the subsurface layer, ranging from 11.9 to 23.5 g·kg^-1 and from 0.66 to 1.50 g·kg^-1, respectively. 2) The monthly variations in SOC and TN contents were significant (except for TN content in the 40-60 cm layer), and the magnitude of variation first decreased and then increased with soil depth. The variations in SOC and TN densities (0-100 cm) were larger during the whole growing season than among years. The SOC density increased during the whole growing season, and ranged from 15.44 to 20.82 kg·m^-2, while the TN density decreased significantly in the early growth period and then tended to remain relatively stable, ranging from 1.01 to 1.16 kg·m^-2. 3) There was a significant positive correlation between SOC content and TN content (P<0.01). Vegetation and hydrology were the key factors affecting the distribution and variations of SOC and TN in the Horqin meadow wetland. The Horqin meadow wetland was found to be a potential carbon sink and nitrogen source during the growing season, but the carbon sink potential has not been fully evaluated on an inter-annual scale. The results indicated that grazing should be banned and nitrogen fertilizer inputs should be increased to enhance the wetland’s function.