温度和氮素输入对青藏高原三种高寒草地土壤碳矿化的影响

Effects of temperature and added nitrogen on carbon mineralization in alpine soils on the Tibetan Plateau

选取了海北高寒草甸、那曲高寒草原和当雄高寒湿地3种典型高寒草地生态系统类型为研究对象,采集了表层0~10 cm土壤,在实验室内进行可控温度下的碳矿化培养实验。结果表明,青藏高原土壤碳矿化在不同高寒草地类型间存在显著差异（P≤0.05）。在较低的温度下,高寒湿地土壤的碳矿化速率显著低于高寒草甸土壤,而温度在15℃左右时,高寒湿地土的碳矿化速率略高于高寒草甸土壤,当温度处于较高的水平时（〉20℃）,高寒湿地土壤碳矿化速率远高于高寒草甸土壤,高寒湿地土壤碳矿化的Q10显著大于高寒草甸。无论是低温还是较高的温度,高寒草原土壤碳矿化速率最低,数值范围也最窄。高寒草甸和高寒湿地土壤碳矿化均受温度的显著影响（P≤0.05）,其速率均跟温度呈现一级指数函数方程关系,而高寒草原土壤碳矿化速率与温度间未呈现明显的函数关系,但不同温度间的土壤碳矿化速率存在显著差异。氮素输入对高寒草甸和高寒湿地土壤碳矿化的影响不明显,但显著促进了高寒草原土壤碳矿化作用。

An incubation experiment was conducted to investigate effects of temperature and added nitrogen on carbon mineralization in three alpine soils under controlled conditions in the laboratory. These soils were collected from the top 10 cm depth in three grassland types： an alpine meadow at Haibei, an alpine steppe at Naqu and an alpine wetland at Dangxiong on the Tibetan Plateau. It was shown that grassland types significantly affected carbon mineralization in these alpine soils. At low temperature, mineralization rates in the alpine wetland soil were lower than in the alpine meadow soil. With increasing temperature, the rates were similar in the two soils at around 15 ℃. When temperature exceeded 20 ℃, mineralization rates were significantly greater in the alpine wetland soil than in the alpine meadow soil. Qlo for carbon mineralization was significantly greater in the alpine wetland soil than in the al- pine meadow soil. Compared with the two soils, mineralization rates in the alpine steppe soil were low showing a different pattern with increasing temperature. Relationship between carbon mineralization and temperature was well described by the first-order ex- ponential equation in both the alpine wetland soil and the alpine meadow soil, but was not for the alpine steppe soil. Nitrogen input had no significant effect on carbon mineralization in both the alpine wetland soil and the alpine meadow soil, but significantly in- creased carbon mineralization in the alpine steppe soil. A small amount of nitrogen input didn＇t alter temperature sensitivity of carbon mineralization in the three alpine soils.