高寒草地退化对土壤碳氮磷及酶活性的影响

Effects of alpine meadow degradation on soil carbon, nitrogen,phosphorus and correlative enzyme activity

摘要:

【目的】土壤碳氮磷元素是支撑高寒草地生态系统的关键，高寒草甸退化会改变土壤养分含量及分布规律，明确高寒草甸退化对土壤关键养分碳氮磷含量及其与酶活性之间相关性的影响可为退化高寒草甸的恢复提供理论依据。【方法】以东祁连山围封草地（FG）为对照，对轻度（LD）、中度（MD） 和重度（SD）退化高寒草甸土壤有机碳、全氮、有效氮、全磷、有效磷含量，以及土壤碳氮磷转化相关的过氧化氢酶、脲酶、碱性磷酸酶活性进行研究。【结果】相比 FG，退化基本导致高寒草甸土壤的有机碳含量升高，SD 0~10 cm 土层有机碳含量最高，为 82. 1 g/kg；退化导致过氧化氢酶活性表现出下降的趋势，围封草地 20~30 cm 土层的过氧化氢酶活性最高，为 23. 35 mg/g，LD 10~20 cm 土层的过氧化氢酶活性最低，为 20. 90 mg/g。退化导致土壤全氮含量降低，有效氮含量和脲酶活性显著升高，SD 草地有效氮含量和脲酶活性均最高，分别为 649 mg/k 和 3. 47 mg/g，脲酶活性在 FG 和 SD 随土层加深而升高，但在 MD 和 SD 随土层加深而降低。4 种类型草地全磷的变化范围为 0. 18~0. 22 g/kg，退化对 0~ 10 cm 土层的全磷含量没有显著影响，而使 0~10 cm 土层，LD 和 MD 的有效磷含量分别增加了 152% 和 60%，而 SD 降低了 32%，0~30 cm 土层碱性磷酸酶活性升高，变化范围为 0. 52~0. 62 mg/g。相关性分析表明，围封草地土壤有机碳与过氧化氢酶活性呈显著负相关，而轻度和重度退化未表现出有相关性；围封草地土壤全氮、有效氮含量与脲酶活性均没有相关性，而轻度和中度退化高寒草甸的脲酶活性与土壤有效氮含量存在显著正相关性；围封草地的土壤全磷、有效磷含量与碱性磷酸酶活性均成呈显著正相关，而退化草地未表现出明显的相关性。【结论】高寒草甸退化后改变了其关键养分与其相关酶活性之间的相关性，重度退化高寒草甸恢复中应考虑土壤磷素的投入。

Abstract:

【Objective】 Soil carbon，nitrogen and phosphorus are of key importance to alpine grassland ecosystem，and alpine meadow degradation can change soil nutrients content and their distribution. Clarifying the effects of alpine meadow degradation on soil key nutrients carbon，nitrogen and phosphorus content and their correlation with enzyme activity can provide a theoretical basis for the restoration of degraded alpine meadows.【Method】 Four types alpine meadows，including Fenced （FG） as a control，light degraded （LD），moderate degraded （MD） and serious degraded （SD） alpine meadow，were selected to study the effects of alpine meadow degradation on soil key nutrients content，correlative enzymes activities as well as correlation of soil key nutrients to enzymes in growing season in the eastern Qilian Mountain area. Soil organic carbon，soil total and available nitrogen，soil total and available phosphorus， soil catalase activity，soil catalase，urease，and alkaline phosphatase activity were analyzed.【Result】 Soil carbon contents increased after degradation compared with CK except for 10~20 cm depth in LD and 0~10 cm depth in MD， and soil carbon content of 0~10cm in SD was the highest，which was 82. 1 g/kg. But soil catalase activity was declined after degraded，and it showed the highest in 20~30 cm in FG，the lowest value was in 10~20 cm in LD，the value was 23. 35 mg/g and 20. 90 mg/g respectively. The degradation resulted in the decrease of soil total nitrogen content，and the increase of available nitrogen content and urease activity. The highest available nitrogen content and urease activity were 649 mg/kg and 3. 47 mg/g in SD grassland，respectively. . Urease activity increased in FG and SD，but decreased in MD and SD with the soil depth. The value of urease activity varied from 0. 18 g/kg to 0. 22 g/kg. Alpine meadow degradation had no significant effect on soil total phosphorus of 0~10cm depth. Soil available phosphorus of LD and MD increased，but SD decreased compared with FG. Soil available phosphorus of LD， MD and SD increased 152%、60% and -32% respectively in 0~10 cm dept. Soil alkaline phosphatase activity increased under degradation，ranging from 0. 52 mg/g to 0. 62 mg/g. The correlation analysis showed that soil the correlation between organic carbon content and catalase activity was significant in FG，but there was no significant correlation in LD and SD. There was no significant correlation between soil nitrogen content and urease activity in FG，but was significant in MD and MD. There was significant correlation between soil phosphorus content and alkaline phosphatase activity in FG，but was no significant correlation in degraded meadows.【Conclusion】The correlation between soil key nutrients content and enzyme activity was changed after degradation in alpine meadows，and phosphorus addition may be needed in the restoration of serious degraded alpine meadow.