Estimating heterotrophic and autotrophic soil respiration using small-area trenched plot technique: Theory and practice

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• 作者：Rachhpal S. Jassal ; T. Andrew Black
• 关键词：Root exclusion ; Soil respiration ; Heterotrophic ; Autotrophic ; Soil CO₂ efflux ; Soil CO₂ concentration ; Diffusivity
• 刊名：Agricultural and Forest Meteorology
• 出版年：2006
• 期刊代码：2_01681923
• 类别：abs
• 出版时间：30 November 2006
• 卷：140
• 期：1-4
• 页码：193-202
• 文件大小：452 K

摘要

The trenching method of root exclusion is generally used to estimate heterotrophic (microbial decomposition) (F_h) and autotrophic (root and associated rhizosphere respiration) (F_a) components of soil respiration (F₀), particularly in forest ecosystems. However, some uncertainties exist on the accuracy and interpretation of the results from such experiments using small-area root exclusion plots. Using field and laboratory measurements as well as simulations using a process-based model of CO₂ production and transport in soil, we show that: (a) CO₂ concentrations at or immediately below the depth of root exclusion in small-area root exclusion plots are similar to those at the same depth in nearby undisturbed soil and (b) the contribution of soil CO₂ flux from below the root exclusion depth to the measured efflux at the surface of a root exclusion plot (F_0re) is increased because of the higher concentration gradient at the bottom of the root exclusion layer due to the decreased rate of CO₂ production above this depth. Consequently, F_a, calculated as F_0c measured in control (non-disturbed) plots minus F_0re measured in root exclusion plots, is underestimated. We describe an analytical model, derived from the soil CO₂ production and diffusion equation, to obtain correct estimates of F_a measured using small-area root exclusion plots. The analytical model requires knowledge of depth distribution of soil CO₂ diffusivity and source strength as inputs.