华北平原地区麦田土壤呼吸特征

Soil respiration of winter wheat fields in North China Plain.

2008年4—6月利用LI-8100及LI-6400-09测定了华北平原典型冬小麦田土壤CO2通量,并分析了麦田土壤呼吸变化规律及其影响机制。结果表明:土壤呼吸日变化呈明显的单峰曲线,最高值出现在12:30—14:30,最低值出现在5:00—6:30;在不同的天气条件下,土壤呼吸速率晴天最高,多云其次,阴天最小;观测期间冠层内各高度CO2浓度与麦田土壤呼吸速率白天呈显著线性负相关,夜间正相关;土壤呼吸速率与5cm地温的季节变化趋势基本一致,二者显著指数相关;在田间持水量范围内,土壤呼吸速率与土壤湿度正相关,当土壤相对湿度低于30%时,土壤呼吸受到抑制而通量降低;综合考虑土壤温度与湿度的双因素指数回归模型能较好地解释土壤呼吸的变化情况,土壤温度低于15℃时效果更好。

By using LI-8100 and LI-6400-09, the soil CO2 flux of a winter wheat field in North China Plain was determined from April to June 2008, with its change patterns and affecting factors analyzed. The soil respiration had a single-peak diurnal variation, with the maximum at 12： 30-14：30 and the minimum at 5：00-6：30, and the respiration rate was higher in sunny days than in cloudy or overcast days. There was a significant negative correlation between the CO2 concentrations at all canopy heights and the soil respiration rate at daytime, but a significant positive correlation at night. The soil respiration rate presented a seasonal variation similar to the soil temperature at 5 cm depth, and had a significant exponential relationship with the soil temperature. Significant correlation was also found between the soil respiration rate and soil humidity when the soil moisture content was within the range of field capacity. Soil humidity less than 30% would limit the soil respiration, inducing a decrease of soil CO2 flux. A multiple exponential regression model of soil temperature and moisture could better explain the variation of soil respiration, especially when the soil temperature was below 15 ℃.