基于BaPS系统的旱地土壤呼吸作用及其分量确定探讨

应用气压过程分离(BaPS)方法研究了大豆和玉米种植下土壤呼吸速率及其分量的动态变化,并同时用气相色谱仪分析了实验期间BaPS系统内的CO2气体浓度,对2种方法测定的土壤呼吸速率进行了比较.结果表明:(1)BaPS方法与气相色谱测得的土壤呼吸速率具有一致性和可比性;(2)大豆田根区土壤呼吸速率随根系生长有明显的季节变化,速率为(29.8±6.4)mg·kg-1·d-1(以C计),非根区土壤呼吸速率在整个生长季数值较低并且季节变化不明显,为(14.4±5.1)mg·kg-1·d-1(以C计);玉米种植下土壤呼吸有类似的规律,差别在于玉米根系生物量比大豆大,呼吸速率也高,根区呼吸速率为(70.8±38.6)mg·kg-1·d-1(以C计),非根区为(18.1±8.7)mg·kg-1·d-1(以C计);(3)根起源呼吸是土壤呼吸的重要组成部分,根区与非根区土壤呼吸速率的差值可以认为来自于根系活动,研究发现大豆田根起源呼吸占土壤呼吸的50%,玉米田根起源呼吸占到69%;(4)利用根起源呼吸与根系生物量的相关关系,得到大豆根起源呼吸系数为0.048mg·mg-1·d-1,玉米的根起源呼吸系数较小为0.042mg·mg-1·d-1.

Determination of upland soil respiration and its components with BaPS System

A BaPS (Barometric Process Separation) system was introduced to determine the seasonal variation of soil respiration rate in the soybean and maize fields. CO₂ concentration in headspace of the BaPSwas simultaneously detected by a gas chromatograph (GC/Agilent4890D). Root biomass of soybean and maize was measured while determining the soil respiration rate. Results indicated that the soil respiration rate measured by the BaPSwas comparable to that determined by the gas chromatograph.An obvious seasonal variation of soil respiration rate in the rhizosphere depending on root biomass was found, while that in the non-rhizosphere was not pronounced. Seasonal soil respiration rate in the rhizosphere averaged 29.8±6.4mg·kg^-1·d^-1 (in C) and 70.8±38.6mg·kg^-1·d^-1(in C) for the soybean and maize fields, respectively. In contrast, the soil respiration rate was relatively lower in the non-rhizosphere, with the seasonal average of 14.4±5.1mg·kg^-1·d^-1(in C)for the soybean field and 18.1±8.7mg·kg^-1·d^-1(in C)for the maize field. We defined the difference of soil respiration rates in the rhizosphere and in the non-rhizosphere as root-derived respiration, and found that the root-derived respiration accounted for 50% and 69% of the total soil respiration in the soybean and maize fields, respectively. Asignificant linear relationship between the root-derived respiration rate and root biomass produced a concept of root respiration coefficient, which was estimated to be 0.048mg·mg^-1·d^-1 for the soybean and 0.042mg·mg^-1·d^-1 for the maize field, respectively.