氮素输入影响下淡水湿地碳过程变化

THE VARIATION OF CARBON STOCK IN FRESHWATER MIRE AFTER NITROGEN INPUT

通过野外控制试验和室内培养试验研究了氮素输入对淡水沼泽湿地碳循环过程的影响。结果表明,氮素的输入能够提高沼泽湿地碳的生物累积,但过多的氮素输入则引起植物生产力的降低,并对常年积水沼泽湿地有机物质的分解有抑制作用。在非淹水条件下,氮素输入后有机物质的分解速率明显大于淹水条件,说明水文条件和氮素输入对枯落物的分解过程都有重要的影响,只是在不同环境条件下的响应存在一定的差异。氮素输入后,植物—土壤系统CO2排放量增大;但是,过多氮素输入后植物—土壤系统呼吸速率降低,这说明一定量的氮素输入可促进植物的生长和根的发育,对微生物的活性也有一定的影响,但过多的氮素输入则会对这些过程产生一定的抑制作用。氮素输入对土壤溶解有机碳(DOC)有明显的影响。氮素输入后,根层土壤DOC含量明显降低(P<0.05),不同土壤深度DOC的变化有一定的差异。

Field control experiment and laboratory culture experiment were conducted to study the influence of nitrogen input on the freshwater mire carbon stock. The results shown that nitrogen input can increase bioaccumulation of carbon in the swamp, however, too much nitrogen input will reduce plant growth rate and prevent organic matter decomposition of flooding mire. The decomposition rate of organic matter in submersed is obviously larger than that of organic matter unsubmersed after input of nitrogen, suggesting hydrological condition and nitrogen input were both affected organic matter decomposition. After nitrogen input, carbon dioxide emission was significantly increased. However, too much nitrogen input induced decrease in carbon dioxide emission. Nitrogen input can stimulate plant growth and activity of soil microbe. On the other hand, too much nitrogen input could prevent plant growth and activity of soil microbe. Nitrogen input also affected obviously the concentration of dissolved organic carbon （DOC）, and DOC concentration significantly decreased after nitrogen inout （P〈0.05）.