旱塬地区不同耕作模式小麦田土壤CO_2释放通量的变异特征

The variation characteristics of soil CO_2 release in wheat growing period in dry land

【目的】揭示不同耕作管理条件下,旱塬地区农田土壤CO2的释放规律。【方法】在陕西关中头道塬设置小麦田与休闲田、旋耕与深耕等双因子4处理裂区试验,用碱吸收法监测小麦生育期间土壤剖面0～40cm土层土壤CO2的释放通量。【结果】(1)小麦生育期间不同处理农田土壤CO2释放通量的变化过程呈现出双峰和双谷特征,分别在小麦播种后秋季苗期及竖年4月初拔节-孕穗期呈现峰值,在越冬期和小麦成熟期出现低谷。小麦田和休闲田土壤CO2释放通量差异明显,其变化规律基本相似。(2)在小麦全生育期,主要根区土壤剖面中CO2释放通量呈现出明显上层低下层高的空间分布梯度。不同耕作模式对土壤剖面中CO2释放通量的时空变异特征有明显影响。(3)在小麦全生育期,不同处理农田土壤CO2累计释放总量差异明显,表现为旋耕处理高于深耕处理,小麦田高于休闲田。【结论】不同土壤耕作管理措施是调控农田土壤碳素循环及土壤空气质量的有效措施。

[Objective] Soil respiration is one of the key components of the terrestrial carbon cycle. The objective of this field study was to compare the effect of different crop and tillage systems on CO2 release from dryland soil on the Guanzhong plain. [Method] The study area consisted of four 70 m^2 （7 m×10 m） field plots. There were two cropping treatments and two tillage treatments. Soil CO2 flux from the 0--40 cm depth was determined using the alkali absorption method. [Result] The result showed two peaks and two valleys in soil CO2 flux rates across the growing season. Soil CO2 flux rates reached peak during the seedling stage and again during the jointing-booting stage. In contrast CO2 flux rates were low during the over-wintering and mature stages. CO2 release amount varied with the two tillage treatments,but changes in flux rates across the growing season were similar regardless of tillage treatment. Tillage also had a significant effect on total CO2 release during the entire growing season. [Conclusion] In summary, the results indicated that total CO2 release during the growing season was much larger for a wheat field compared to a fallow field. In the fallow field, total CO2 release was significantly larger in the rotary tillage treatment compared to the deep tillage treatment.