玉米地土壤呼吸作用对土壤温度和生物因子协同作用的响应

 基于2005年玉米(Zea mays)生长季土壤呼吸作用及其影响因子的动态观测资料，分析了玉米地土壤呼吸作用的日和季动态及其对土壤温度和生物因子协同作用的响应。结果表明 ，玉米地土壤呼吸作用的日变化为不对称的单峰型，其最小值和最大值分别出现在6∶00～7∶00和13∶00左右；玉米生长季中，土壤呼吸速率波动较大，其均值为3.16 μmolCO₂·m^-2·s^-1，最大值为4.87μmolCO₂·m^-2·s^-1，出现在7月28 日，最小值为1.32μmolCO₂·m^-2·s^-1，出现在5月4日。在土壤呼吸作用日变化中，土壤呼吸速率(SR)与10 cm深度土壤温度(T)呈显著的线性关系：SR=αT+β。在整个生长季节中，玉米净初级生产力(NPP)与直线斜率(α)呈显著正相关，生物量(B)也明显影响直线的截距(β)。基于此，建立了玉米地土壤呼吸作用动态模型SR=(aNPP+b)T+cB²+dB+e。土壤呼吸作用季节变化的大部分(97%)可以由土壤温度、NPP和生物量的季节变化来解释。当仅考虑土壤温度对土壤呼吸作用的影响时，指数方程会过大或过小地估计了土壤呼吸强度。该文的结果强调了生物因子在土壤呼吸作用季节变化中的重要作用，同时指出土壤呼吸作用模型不仅要考虑土壤温度的影响，在生物因子影响土壤呼吸作用的温度敏感性时，还应该把生物因子纳入模型。

RESPONSES OF SOIL RESPIRATION TO THE COORDINATED EFFECTS OF SOIL TEMPERATURE AND BIOTIC FACTORS IN A MAIZE FIELD

Aims Based on the dynamic measurements of soil respiration and its environmental factors in a maize (Zea mays) field during the growing season in 2005, the diurnal and seasonal variations of soil respiration (SR) and their responses to the coordinated effects of soil temperature and biotic factors were studied. Our objective was to describe the effects of biotic factors on the response of soil respiration to soil temperature and to determine the seasonal variation of soil respiration during the growth season of maize. Methods Soil respiration rates were measured twice monthly during the growing season (May-September) in 2005 using a soil respiration chamber (LI-6400- 09, Li-Cor Inc., Lincoln, NE) connected to a portable infrared gas analyzer (IRGA, LI-6 400, Li-Cor Inc., Lincoln, NE). We inserted 15 soil collars into the soil and soil respiration was pooled over all 15 collars per plot. To catch the diurnal pattern, soil respiration rates were measured every hour from 6∶00 to 18∶00 on May 4, June 5, June 28, July 28, August 28 and September 22. Important findings The diurnal variation of soil respiration showed asymmetric pattern, with the minimum value occurring around 6∶00-7∶00 hours (local time ) and the maximum value around 13∶00 hours. Soil respiration fluctuated greatly during the growing season. The mean soil respiration rate was 3.16μmolCO₂·m^-2·s^-1, with a maximum value of 4.87μmolCO₂·m^-2·s^-1 on July 28 and a minimum value of 1.32μmolCO2·m^-2·s^-1 on May 4. During the diurnal variation of soil respiration, there was a significant linear relationship between soil respiration and soil temperature (T) at 10 cm depth. During the growing season, the coefficients of α and β were fluctuated because the net primary productivity (NPP) of maize markedly increased the slope (α) and the biomass (B) markedly influenced the intercept (β) of the linear equation. Thus, the dynamic model of soil respiration was developed. Most of the temporal variability (97%) in soil respiration could be explained by the variations in soil temperature, biomass and NPP of maize defined in the model. However, just taking account into the influence of soil temperature on soil respiration, an exponential equation over- or underestimated the magnitude of soil respiration.