氮添加对黄土高原草原生态系统净碳交换的影响

以黄土高原典型草原为对象,采用静态箱-红外分析仪联用法进行野外原位试验,研究氮添加对生态系统CO2通量的影响。设置6个氮添加水平,分别为N0(0)、N1(1.15 g·m^-2·a^-1)、N2(2.3 g·m^-2·a^-1)、N3(4.6 g·m^-2·a^-1)、N4(9.2 g·m^-2·a^-1)和N5(13.8 g·m^-2·a^-1),氮素类型为尿素((NH2)2CO)。结果表明:氮添加处理没有改变生态系统碳交换的季节动态趋势,但是增加了生态系统净碳交换能力(NEE)、生态系统呼吸(ER)和总生态系统生产力(GEP)的峰值。N2、N3、N4、N5处理的NEE生长季绝对累积量分别比对照增加62%、45%、72%和48%;ER累积量分别增加66%、69%、78%、70%;GEP累积量分别增加65%、66%、77%、68%。氮添加处理增强了黄土高原典型草原植物生长季的碳汇功能。0~10 cm层土壤温度和湿度是影响黄土高原典型草原生态系统净碳交换的重要因素。

Influence of Nitrogen Addition on Net Ecosystem Carbon Exchange of Steppe in the Loess Plateau

The static chamber and infrared analyzer were used to investigate the effect of increased nitrogen (N) deposition on ecosystem carbon (C) exchange, and a field experiment that simulated N deposition was conducted in a steppe located in the Loess Plateau. There were six N treatments included in the experiment: 0, 1.15, 2.3, 4.6, 9.2 and 13.8 gN·m^-2·a^-1 with (NH₂)₂CO. The results indicated that the N treatments did not change the seasonal patterns of ecosystem C exchange, but increased the peak values of net ecosystem exchange (NEE), ecosystem respiration (ER), and general ecosystem production (GEP). The seasonal accumulation of NEE under 2.3, 4.6, 9.2 and 13.8 gN·m^-2·a^-1 N treatments increased by 62%, 45% ,72% and 48%, respectively, while the seasonal accumulation of ER increased by 66%, 69%, 78% and 70%, and GEP by 65%, 66%, 77% and 68%, compared with the control treatment. Therefore, the N treatments could significantly reduce C sequestration in the typical steppe of the Loess Plateau. Soil temperature and soil moisture in the 0-10 cm soil layer were the most important factors affecting ecosystem C exchange.