温度对生物土壤结皮斑块土壤氮矿化作用的影响

Effects of Temperature on Soil Net Nitrogen Mineralization under Different Biological Soil Crusts in Shapotou,Northern China

以腾格里沙漠东南缘天然植被区藓类结皮、藻地衣结皮斑块荒漠土壤为研究对象,采用原状土培养法,在人工气候箱中设置不同温度(-10、5、15、25、35、40℃)培养14d,测定土壤样品在培养前后NH4+-N和NO3--N含量,分析两种生物土壤结皮斑块土壤净硝化和净矿化速率对温度的响应。结果表明:①低温培养条件下(-10～15℃)土壤氮转化以固持态为主,随着温度升高,尤其当温度超过25℃后,藓类结皮、藻地衣结皮斑块土壤净硝化和净氮矿化速率显著提高(p<0.05);②同一温度培养下,以藓类结皮发育为主的土壤氮转化水平较高,净硝化速率和净氮矿化速率以及无机氮的积累明显大于以藻地衣结皮发育为主的土壤;③两种生物土壤结皮斑块土壤净氮转换速率(硝化和矿化)Q10值在2.46～3.33间波动,其中藓类结皮斑块土壤氮转换对温度的敏感性较高。此外,在土壤氮总矿化过程中,硝化过程具有较强的温度敏感性。高温促进了土壤净氮矿化水平,增加土壤氮有效性,因此可能会对荒漠生态系统的初级生产力产生正向影响作用。

Effects of temperature on soil net nitrogen transformation rates （nitrification and mineralization） under moss-covered soil and algae-lichen-covered soil were evaluated by measuring the concentrations of NH＋-N and NO3--N of undisturbed soil cores incubated in artificial chamber after 14 days of incubation with a temperature gradient of--10, 5, 15, 25, 35, 40 v. Results showed that： （1）immobilization was the main form in the nitrogen transformation （nitrification and mineralization） under the lower incubation temperatures （- 10 - 15℃ ）, the net nitrification and mineralization rates increased significantly （p 〈0.05） with increasing temperature, especially when the temperature surpassed 25℃ ; （2） the moss-dominated soil facilitated the nitrogen transformation, the rates of net nitrification, nitrogen mineralization, and the contents of inorganic nitrogen in moss-dominated soil were higher than in algae-lichen-dominated soil; （3） the Q10 values of nitrogen transformation rates ranged from 2.46 to 3.33. In addition, the net nitrogen transformation rates of moss-dominated soil were more sensitive to temperature variation than algae-lichen-covered soil. Concerning the whole nitrogen transformation process, nitrification was more sensitive to temperature than mineralization. Higher temperature is beneficial to soil net nitrogen mineralization rate and the biological soil crusts can enhance the availability of nitrogen, which may affect the primary productivity in desert ecosystems.