不同底座嵌入方式和入土深度对典型草原土壤呼吸的影响

Effects of Different Collar Embedding Methods and Buried Depth on Soil Respiration in Typical Steppe

【目的】作为连接陆地生态系统和大气系统最主要的碳通道,土壤呼吸在预测全球变化及构建全球碳循环模型中都扮演者非常重要的角色。目前,多数研究集中于环境因子变化对土壤呼吸的影响,而很少关注土壤呼吸测定值对底座设置的响应。研究旨在了解不同底座嵌入方式和深度对土壤呼吸测定结果潜在的影响及其调控机制。【方法】在内蒙古典型草原设置了3种底座嵌入方式[IM(即插即测);IS(提前一天嵌入测完随即拔出)和IL(永久嵌入)]和2种底座入土深度(2 cm和5 cm)处理。【结果】整个生长季,底座嵌入方式和入土深度均显著改变了土壤呼吸测定值,IM最大,其次是IL,IS最小。IM处理土壤呼吸比IS和IL处理分别降低了5.5%~13.0%和1.2%~10.2%;底座入土越深,IM处理土壤呼吸越高,IS和IL处理土壤呼吸越低。SEM结果表明,底座嵌入方式主要通过改变地上净初级生产力对土壤呼吸测定结果产生影响;而底座入土深度还通过降低土壤水分和增加土壤温度来使土壤呼吸测定结果降低,嵌入较深的IM处理主要因其对土壤孔隙扰动较大而使土壤呼吸测定结果偏大。所有因子共同解释了土壤呼吸63%的变异。【结论】研究发现,气室法测定土壤呼吸时,底座嵌入方式和入土深度对土壤呼吸测定结果具有显著影响,该研究对准确测定土壤CO_(2)释放速率,进而准确评估土壤碳循环在当下及未来全球气候变化中的作用尤为重要。实践中,适当降低底座入土的深度可以有效减少底座嵌入对试验所造成的扰动。

[Ojective]As the main carbon channel connecting terrestrial ecosystem and atmospheric system,soil respiration plays an important role in predicting global change and constructing global carbon cycle model.Most of the previous studies focus on the influence of environmental factors on soil respiration,little attention is paid to the response of soil respiration measured to the collar setting.This study aims to understand the effects of different collar embedded methods and buried depths on soil respiration measurement results and the mechanisms.[Methods]We conducted a two-factor experiment to examine how soil collar embedded methods(Insert and measure,IM;Insert for a short time,IS and Insert for a long time,IL)and depths(2 cm and 5 cm)affected the soil respiration(SR)in a semi-arid steppe of Inner Mongolia.[Results]Throughout the growing season,the collar embedded methods and depths significantly changed the soil respiration measured values,IM was the highest,followed by IL and IS.Soil respiration of IM was 5.5%-13.0%and 1.2%-10.2%lower than that of IS and IL treatment respectively;the deeper the collar was embedded in the soil,the higher the soil respiration of IM was,and the lower the soil respiration of IS and IL was.Structural equation model indicated that the collar embedded methods affected the soil respiration measurement results mainly by changing ANPP;the lower respiration in the deep-inserted soil collars was due to the lower soil moisture and higher soil temperature,the IM treatment with deeper embedded caused higher soil respiration measurement due to its larger disturbance to soil porosity.All factors jointly explain 63%variation of soil respiration.[Conclusion]The findings suggest that the collar embedded methods and depths on soil respirationhave significant effects on the soil respiration measurement results.This study is significant for accurate measurement of soil CO_(2)release rate and accurate assessment of the role of soil carbon cycle in current and future global climate change.In practice,accurately grasping of collar embedment is particularly important for the accuracy of soil respiration measurement.