极端干旱区土壤呼吸对储水灌溉和冻融循环的响应

目的] 揭示中国极端干旱区甘肃省石羊河流域储水灌溉与季节性冻融叠加作用下对土壤呼吸的影响，为进一步提高极端干旱区灌溉水资源利用效率和节约灌溉水源提供理论基础和技术支撑。方法] 按照1 199.4 m³/hm²低灌溉定额分为灌水和非灌水处理，将冻融循环分为冻结期、冻融期和解冻期3个时间段，采用LI-8100土壤碳通量全自动测量系统对各处理地块的土壤呼吸速率进行观测与分析。结果] 极端干旱区储水灌溉在季节性冻融作用下农田生态系统土壤呼吸速率增强，土壤碳排放量增加，农田生态系统碳循环被改变，有利于作物的生长和提高粮食产量。不同土地利用方式下土壤呼吸速率对水分和温度的响应程度不同。整个冻融过程中土壤呼吸速率呈现出：解冻期>冻结期>冻融期的规律。冻结期、冻融期和解冻期3个时期的土壤CO₂都表现为源，但在夜间极低温度时土壤CO₂由源转化为汇。结论] 储水灌溉调控了整个冻融期土壤呼吸的过程，改变了极端干旱区农田生态系统的碳循环。在水分与季节性冻融叠加作用下，储水灌溉地块土壤呼吸速率相对未储水地块随温度的波动更为剧烈，但与温度的变化趋势一致，水分加剧了其随温度的波动。

Response of Soil Respiration to Storage Irrigation and Freeze-thaw Cycles in Extremely Arid Areas

Objective] The effects of water storage irrigation and seasonal freezing and thawing on soil respiration were determined in order to improve the utilization efficiency of irrigation water resources, and save irrigation water resources at Shiyang River watershed of Gansu Province in extremely arid regions in China.Methods] The LI-8100 automatic soil carbon flux measurement system was used to observe and analyze soil respiration rates. Treatments were divided into irrigation and non-irrigated treatments according to the low irrigation quota of 1 199.4 m³/hm². The freeze-thaw cycle was divided into three time periods:freezing period, freeze-thaw period, and thawing period.Results] Under the effects of seasonal freeze-thaw cycles, soil respiration rate and soil carbon emissions of farmland ecosystems increased and the carbon cycle of farmland ecosystems was changed, resulting in increased crop growth and food production. Soil respiration rates responded differently to moisture and temperature under different land use patterns. During the entire process, soil respiration rate was greater during the thawing period than that of the freezing period and the freeze-thaw period. The soil CO₂ in the three periods of freezing, freeze-thaw, and thawing were all shown to be sources, but were all converted from sources to sinks at very low night temperature.Conclusion] Water storage irrigation regulated the process of soil respiration throughout the freezing and thawing period and changed the carbon cycle of farmland ecosystems in extremely arid regions. Under the superimposed action of moisture and seasonal freeze-thaw, the soil respiration rate of storage irrigation plots fluctuated more drastically with temperature than the soil respiration rate of non-storage plots, and this result was consistent with the change trend of temperature, indicating that moisture aggravates soil respiration fluctuations with temperature.