亚热带城郊草坪土壤呼吸对春季天气变化的响应

采用静态箱-碱液吸收法,对亚热带(长沙市)城郊2种暖季型草坪(狗牙根和台湾草)2012年初春典型天气过程下的土壤呼吸进行了连续28天的逐日观测,研究草坪土壤呼吸对春季天气变化的响应规律。结果表明,在春季的连续阴雨期、寒潮降温期和快速升温期,土壤呼吸波动较大,分别介于C 0.22~0.53、0.51~0.89和0.51~1.22 g/(m2·d),基本与土温变化一致。在观测期内,草坪土壤呼吸的表观Q10值较高(2.52),但在寒潮降温期和快速升温期Q10值降低(1.70和1.96),反映出草坪土壤微生物和根系活动对初春快速温度变化响应的敏感度降低,这可能是土壤呼吸长期适应的结果。春季降雨充沛,草坪土壤呼吸随着土壤质量含水量的升高而降低,较高的日降雨量明显抑制了土壤呼吸。两种草坪间土壤呼吸速率没有显著性差异,草种对初春土壤呼吸的影响可能很小。试验结果表明春季水热变化快,土壤呼吸日值波动大,在估算土壤呼吸年通量时,应充分考虑短期天气变化尺度上土壤呼吸的剧烈波动。

Response of Soil Respiration to Changes of Spring Weather Under Subtropical Urban Lawns

The daily response of soil respiration to changes of spring weather under two subtropical urban lawns (Cynodon dactylon (Linn.) Pers. and Zoysia tenuifolia Willd. ex Trin.) were investigated through 28 days in situ measurements using static chamber with alkali absorption technology. Results showed that the soil respiration fluctuated greatly and primarily consisted with the fluctuation of soil temperature during the period of continuous rain, the period of rapid warming and the period of cold-air outbreak. The apparent Q10 value of soil respiration across the study period was 2.52, but it decreased to 1.96 and 1.70 during the period of rapid warming and the period of cold-air outbreak, respectively. It seemed that the microbial respiration and root activity were relatively insensitive to rapid daily changes of temperature in early spring. Owing to the abundant spring rainfall, the soil respiration of lawns was decreased with the rising of soil gravimetric water content and was inhibited by the saturation of soil water. No difference of soil respiration rate was found between the two types of lawns. This study suggested that the spring daily soil respiration of urban lawns varied greatly and it should incorporate changes of soil respiration at weather scales into the annual model of soil respiration.