Drought alters respired 未¹³CO₂ from autotrophic, but not heterotrophic soil respiration

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• 作者：D. Risk^a ; ^{drisk@stfx.ca} ; N. Nickerson^a ; ^b ; C.L. Phillips^a ; L. Kellman^a ; M. Moroni^c ; ¹
• 关键词：Soil respiration ; Carbon ; Isotopes ; Partitioning ; Autotrophic ; Heterotrophic
• 刊名：Soil Biology & Biochemistry
• 出版年：2012
• 期刊代码：96_00380717
• 类别：abs
• 出版时间：July, 2012
• 卷：50
• 期：Complete
• 页码：26-32
• 文件大小：517 K

摘要

Many researchers are interested in the variability of root-respired 未¹³CO₂ as an indication of linkages between belowground plant respiration and canopy processes. Most studies in this area have, however, relied upon the assumption that temporal variability of total soil respired 未¹³CO₂ reflects autotrophic soil processes, but in fact few supporting measurements of purely autotrophic soil respiration (partitioned from total soil respiration) are available. Here we use a combination of physical and isotopic partitioning methodologies to track the variability in autotrophic and heterotrophic soil 未¹³CO₂ at five sites in Eastern Canada during a very dry growing season. Three dimensional modeling of soil isotopic transport dynamics in the static sampling chambers allow us to constrain measurement bias and to eliminate non-steady-state effects as a potential driver of observed variability. We provide experimental results that support a pivotal assumption made in prior interpretations of soil 未¹³CO₂ dynamics: we observed minimal isotopic variability in soil microbial 未¹³CO₂ efflux, but appreciable temporal variability in root-respired 未¹³CO₂ at sites where near drought conditions were observed, suggesting that isotopic discrimination is likely linked to seasonal variations in transpirational demand.