兴凯湖附近退耕还湿地、天然沼泽和稻田土壤的氧化亚氮、甲烷产生潜力和除氮能力模拟研究

Simulation of Production Potentials of Nitrous Oxide and Methane and Nitrogen Removal Capacity of Soils in Restored and Natural Marshes and Paddy Fields near Xingkai Lake

于2019年10月12日至13日,在黑龙江省密山市兴凯湖国家级自然保护区毗邻区域,选取天然沼泽、由稻田退耕1 a、6 a和10 a的自然恢复沼泽、由天然沼泽开垦已经耕作5 a和50 a的稻田作为6处采样地,采集0~20 cm深度土壤样品,测定其理化指标;2021年4月6日至12日,开展了室内土壤样品培养实验,研究土壤氧化亚氮和甲烷产生潜力随培养时间的变化和土壤对外源氮的去除能力。研究结果表明,稻田退耕后,随着退耕时间的增加,其0~20 cm深度土壤p H逐渐减小,退耕10 a的自然恢复沼泽0~20 cm深度土壤的pH(5.18)最小,退耕6 a和10 a的自然恢复沼泽0~20 cm深度土壤中的无机氮和有机碳含量显著大于天然沼泽和稻田;在无外源氮输入条件下,天然沼泽0~20 cm深度土壤氧化亚氮产生潜力峰值[1.90 mg/(kg·h)]最大,退耕10 a的自然恢复沼泽0~20 cm深度土壤甲烷产生潜力峰值[1 387.67 mg/(kg·h)]最大;在外源氮输入条件下,各采样地0~20 cm深度土壤氧化亚氮产生潜力都大幅上升,而甲烷产生潜力则明显减小,退耕10 a的自然恢复沼泽0~20 cm深度土壤的氧化亚氮和甲烷产生潜力峰值都最大,分别为350 mg/(kg·h)和23.11 mg/(kg·h);天然沼泽0~20 cm深度土壤对铵态氮的去除率(78.8%)最大;退耕6 a、10 a的自然恢复沼泽和天然沼泽0~20 cm深度土壤对硝态氮的去除率(分别为96.11%、99.79%和90.56%)和对总外源氮的去除率(分别为84.86%、73.98%和84.66%)都显著大于耕作稻田和退耕1a的自然恢复沼泽。退耕还湿工程的实施有利于土壤有机碳累积和外源氮去除。

During October 12-13, 2019, soil samples at 0-20 cm depth were sampled from natural marsh and natural recovery marshes for 1 year, 6 years and 10 years from paddy fields, and paddy fields cultivated for 5years and 50 years in the area adjacent to the Xingkai Lake National Nature Reserve, Mishan city,Heilongjiang province. The physical and chemical indexes of soils at 0-20 cm depth of 6 sampling sites were measured, and the production potential of nitrous oxide and methane and the removal ability of exogenous nitrogen of the soils were studied by laboratory incubation experiments. The results showed that pH of soils at0-20 cm depth in natural recovery marshes gradually decreased with the increase of restored years, and pH(5.18) of soil at 0-20 cm depth of natural recovery marsh for 10 years was the smallest. The contents of inorganic nitrogen and organic carbon in the soils at 0-20 cm depth of natural recovery marshes for 6years and10 years were significantly higher than those in natural marsh and paddy fields. Without exogenous nitrogen input, the peak value(1.90 mg/(kg· h)) of production potential of nitrous oxide from the soil at 0-20 cm depth in natural marsh was the largest. The peak value(1387.67 mg/(kg· h)) of production potential of methane from the soil at 0-20 cm depth of natural recovery marsh for 10 years was largest. Under exogenous nitrogen input,the production potential of nitrous oxide from the soils at 0-20 cm depth of 6 sampling sites increased significantly, while the production potential of methane decreased significantly. Meanwhile, the maximum production potential of nitrous oxide and methane from the soil at 0-20 cm depth of natural recovery marsh for10 years were 350 mg/(kg · h) and 23.11 mg/(kg · h), respectively. The maximum removal rate of ammonium nitrogen was 78.8% by the soil at 0-20 cm depth of natural marsh. The removal rates of nitrate nitrogen were96.11%, 99.79% and 90.56%, and the removal rates of total exogenous nitrogen were 84.86%, 73.98% and84.66% by the soils at 0-20 cm depth of natural recovery marshes for 6 years and 10 years, and natural marsh,respectively, which were significantly higher than those in the paddy fields and natural recovery marsh for 1year. With the paddy fields to marshes, it is beneficial to the accumulation of organic carbon in the soil and the removal of exogenous nitrogen.