喀斯特农田土壤呼吸对干湿交替的响应特征

Response of soil respiration to dry-wet alternation in karst farmland

【目的】探究中国西南喀斯特地区农田石灰性土壤二氧化碳(CO_(2))排放通量对该区频繁发生的干湿交替的响应规律。【方法】以喀斯特农田石灰性土壤为研究对象,设计2种干湿交替强度(模拟降水量为10和25 mm),以干湿交替循环周期10 d为1个循环过程,研究喀斯特农田土壤呼吸对干湿交替的响应。【结果】干湿交替强度显著影响土壤呼吸速率和土壤总CO_(2)排放量(P<0.05)。在2种干湿交替强度下,随着水分施加,土壤CO_(2)排放通量会在短时间内达到最大值,然后逐渐下降。对于10 mm降水干湿交替强度,不同循环周期下的土壤CO_(2)排放通量和土壤总CO_(2)排放量之间的差异并不显著。然而,对于25 mm降水干湿交替强度,大多数循环周期下的土壤CO_(2)排放通量和土壤总CO_(2)排放量之间的差异显著(P<0.05)。相关分析表明:干湿交替多重周期作用下,土壤含水量和土壤CO_(2)排放通量之间的相关关系不断降低。【结论】干湿交替强度和干湿交替过程是影响喀斯特农田土壤呼吸排放的重要因素.

[Objective]The objective of this study is to explore the response of soil CO_(2) emission flux from calcareous soil to frequent dry-wet alternation in farmland of karst areas in southwest China.[Method]Taking calcareous soil in karst farmland as the research object,two dry-wet alternation intensities(simulated precipitation of 10 and 25 mm)were designed,with a dry-wet alternation cycle of 10 days as one cycle process,to investigate the response of soil respiration to dry-wet alternation in karst farmland.[Result]The intensity of dry-wet alternation significantly affected soil CO_(2) emission flux and total soil CO_(2) emissions(P<0.05).Under two different dry-wet alternation intensities,soil CO_(2) emission flux reached its maximum shortly after water was applied,and then gradually decreased.For the 10 mm dry-wet alternation intensity,there was no significant difference between soil CO_(2) emission flux and total soil CO_(2) emissions under different cycles.However,for the 25 mm dry-wet alternation intensity,the difference between soil CO_(2) emission flux and total soil CO_(2) emissions under most cycles was significant(P<0.05).Correlation analysis revealed that the correlation between soil water content and soil CO_(2) emission flux decreased continuously under the multiple cycles of dry-wet alternation.[Conclusion]The intensity and process of dry-wet alternation are important factors affecting soil respiration release in karst farmland.