玉米农田土壤呼吸作用的空间异质性及其根系呼吸作用的贡献

Spatial heterogeneity of soil respiration and contribution of root respiration in a maize (Zea mays L.) agricultural field

基于4月底到9月底东北地区玉米农田土壤呼吸作用全生长季的观测,阐明了土壤呼吸作用的空间异质性特征,综合分析了水热因子、土壤性质、根系生物量及其测定位置对土壤呼吸作用空间异质性的影响,并对生长季中根系呼吸作用占土壤呼吸作用的比例进行了估算。结果表明,在植株尺度上,土壤呼吸作用存在着明显的空间异质性,较高的土壤呼吸速率通常出现在靠近玉米植株的地方。根系生物量的分布格局是影响土壤呼吸作用空间异质性的关键因素。在空间尺度上,土壤呼吸作用与根系生物量呈显著的线性关系,而土壤湿度、土壤有机质、全氮和碳氮比对土壤呼吸作用空间异质性的影响并不显著。通过建立土壤呼吸作用与玉米根系生物量的回归方程,对根系呼吸作用占土壤呼吸作用的比例进行了间接估算。玉米生长季中,根系呼吸作用占土壤呼吸作用的比例在43.1%～63.6%之间波动,均值为54.5%。

Soil respiration for a specific ecosystem can be characterized by its magnitude and its temporal and spatial variability. In order to accurately estimate carbon budgets in target ecosystems, we must be able to account for small-scale spatial variation in soil respiration. However, spatial heterogeneity of soil respiration has been less studied as compared with its magnitude and its temporal variability in agricultural ecosystems. Based on continuous t of soil respiration in a maize ecosystem in Northeast China from late April to late September in 2005, the spatial variation of soil respiration was elucidated and the effects of heat and water factors, soil properties, root biomass, and measurement position on it were analyzed synthetically. The results showed that there were significant spatial patterns for soil respiration at the plant scale of the maize ecosystem and higher soil respiration rates tended to occur near the maize plant during the growing season. The spatial variation of root biomass accounted for spatial heterogeneity of soil respiration, and there were linear relationships existing between soil respiration rate and root biomass. However, there were weaker relationships between the spatial heterogeneity of soil respiration and the spatial variation of other environmental factors such as the soil moisture, soil organic matter, total nitrogen content and C：N. In addition, root respiration was evaluated indirectly by establishing linear regressive relationships between soil respiration rates and dry root weights. The contribution of root respiration to soil respiration averaged 54.5% and fluctuated from 43.1% to 63.6% during the maize-growing season.