腾格里沙漠东南缘不同类型生物土壤结皮对土壤有机碳矿化的影响

生物土壤结皮(BSCs)是荒漠生态系统的重要组成部分,是该区土壤碳循环及碳平衡的关键影响因素。研究了腾格里沙漠东南缘不同类型生物土壤结皮覆盖下土壤碳矿化过程及其对温度(10℃、25℃和35℃)和水分(土壤含水量10%和25%)变化响应特征,分析了土壤碳矿化过程与土壤理化性质的关系。结果表明:(1)结皮的形成和发育显著影响土壤有机碳矿化过程,藻类、地衣和藓类结皮覆盖的土壤碳矿化速率和CO_2-C累积释放量均显著高于去除结皮的土壤,不同类型BSCs覆盖土壤和去除结皮土壤之间均表现为藓类结皮土壤地衣结皮土壤藻类结皮。(2)含结皮层土壤的平均和最大矿化速率均随温度升高和水分增加而逐渐增大,有结皮覆盖的土壤和去除结皮的土壤对温度和水分变化的响应规律相同。(3)有结皮土壤和去除结皮土壤碳矿化速率的温度敏感性(Q_(10))与结皮类型密切相关,均表现为藓类结皮地衣结皮藻类结皮。结果表明生物土壤结皮由以藻类为主向以藓类为主的演变进一步促进了土壤碳矿化过程,结皮对土壤碳循环的调控作用受水热等环境因子的共同影响。

Carbon mineralization of soil covered by different types of biological crusts in the southeastern fringe of the Tengger Desert

Biological soil crusts (BSCs) are the association of soil organisms including algea, cyanobacteria, bacteria, fungi, lichen and moss and soil particles, which cover as much as 70% of the interspaces between vegetation and are the key component of arid and semiarid ecosystems. They play a significant role in the process of soil formation and biogeochemical cycling of carbon and nitrogen. Although the functions of BSCs in soil carbon cycling in drylands have been extensively described in the literature, previous research has primarily focused on the effects of BSCs on soil carbon sequestration and respiration. Knowledge is rather poor regarding their effects on soil organic carbon mineralization which is the major part of global carbon cycling and an important process of carbon loss from soils in terrestrial ecosystem. Consequently, understanding the effects of BSCs on soil organic mineralization and their regulating factors is crucial to thoroughly addressing their contribution to the soil carbon budget and balance in drylands.In this study, both intact soil (IS) and BSC-being-removed soil (BRS) samples were collected from algae-, lichen-, and moss-covered soil plots in the southeastern fringe of the Tengger Desert. Carbon mineralization rates of different types of soils and their responses to soil moisture and temperature were investigated by dark incubation. The relationships between soil mineralization rates and soil physicochemical factors were also analyzed. The results showed that (1) SOC mineralization rates and cumulative CO₂-C release from IS were significantly higher than those from BRS. These two parameters for both IS and BRS were in the order moss crust > lichen crust > algae crust. (2) The average and maximum soil carbon mineralization rates increased with increasing magnitude of incubation temperature and soil water content, and the dynamic patterns of their response both were similar. (3) Temperature sensitivity (Q₁₀) of the three intact soils and their respective subsoils were closely linked to BSC types, with the highest value for moss-covered soil and the lowest for algae-covered soil. Our understanding of the effects of on soil carbon mineralization suggests that the evolution of BSCs from algae-dominated to moss-dominated soil promoted carbon mineralization, and their regulation of soil carbon cycling was strongly controlled by environmental factors, such as temperature and soil moisture.