荒漠藓类植物死亡对表层土壤酶活性的影响

土壤胞外酶作为土壤生物化学反应的催化剂, 直接驱动了土壤物质循环和能量流动过程。全球气候变化和土地利用类型改变致使维持荒漠地表稳定的生物土壤结皮中的藓类植物出现不同程度的死亡, 然而, 藓类植物的死亡将如何影响荒漠表层土壤养分循环过程仍缺乏研究。该研究选取新疆古尔班通古特沙漠优势藓类结皮为研究对象, 测定了自然存活及自然死亡藓类结皮下不同土层(0-2、2-5、5-10、10-20 cm)碳氮磷循环相关酶活性。结果发现: 除蔗糖酶外, 藓类植物死亡显著影响了β-葡萄糖苷酶、过氧化物酶、多酚氧化酶、脲酶、硝酸还原酶、植酸酶和碱性磷酸酶活性, 并随土壤深度的增加酶活性逐渐递减。同时, 藓类植物死亡显著抑制了植酸酶活性, 促进了与碳氮磷循环相关的土壤酶活性。土壤碳氮循环相关酶活性与土壤有机碳、全氮、NO₃^--N和NH₄⁺-N含量显著正相关, 与pH显著负相关; 植酸酶、碱性磷酸酶活性与土壤全磷、速效磷含量相关性不显著。荒漠藓类植物的死亡, 在短期内显著改变了土壤酶系统, 加速了土壤养分循环。

Effects of moss mortality on soil enzyme activities in a temperate desert

Aims Catalysis associated with extracellular enzymes are closely related to nutrient circulation and energetic flow in soils. Changes of global climate and land use have resulted in different degrees of death of moss-dominated biological soil crusts (BSCs), yet there is still little knowledge of how moss mortality influences the nutrient cycling in the topsoil of a temperate desert. Methods In this study, we measured the enzyme activities related to carbon, nitrogen and phosphorus cycling in different soil layers (0-2, 2-5, 5-10, 10-20 cm) under living and dead mosses in a desert in Gurbantünggüt, Xinjiang, China. Important findings We found that moss death had a significant effect on the activities of β-glucosidase, peroxidase, polyphenol oxidase, urease, nitrate reductase, phytase and alkaline phosphatase; these enzyme activities decreased with the increase of soil depth. The moss death decreased phytase activity, and increased enzyme activities related to carbon, nitrogen and phosphorus cycling. The results of correlation analyses showed that the carbon- and nitrogen-related enzyme activities were positively correlated with soil organic carbon, total nitrogen, NO₃^--N and NH₄⁺-N contents, and negatively correlated with pH, whereas the phytase and alkaline phosphatase activities had no significant correlation with total phosphorus and available phosphorus contents. In summary, the moss death in the temperate desert changed soil enzyme activities and accelerated soil nutrient cycling in a relatively short time.