Temporal variability in 13C of respired CO 2 in a pine and a hardwood forest subject to similar climatic conditions

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• 作者：Behzad Mortazavi ; Jeffrey P. Chanton ; James L. Prater ; A. Christopher Oishi ; Ram Oren and Gabriel Katul
• 关键词：Carbon isotope ; Coniferous forest ; Hardwood forest ; Vapor pressure deficit ; Ecosystem respiration
• 刊名：Oecologia
• 出版年：2005
• 出版时间：January 2005
• 年：2005
• 卷：142
• 期：1
• 页码：57-69
• 全文大小：258 KB
• 刊物类别：Biomedical and Life Sciences
• 刊物主题：Life Sciences
  Ecology
  Plant Sciences
  
• 出版者：Springer Berlin / Heidelberg
• ISSN：1432-1939

文摘

Temporal variability in the 13C of foliage (13C_F), soil (13C_S) and ecosystem (13C_R) respired CO₂ was contrasted between a 17.2-m tall evenly aged loblolly pine forest and a 35-m tall unevenly aged mature second growth mixed broadleaf deciduous forest in North Carolina, USA, over a 2-year period. The two forests are located at the Duke Forest within a kilometer of each other and are subject to identical climate and have similar soil types. The 13C_F, collected just prior to dawn, was primarily controlled by the time-lagged vapor pressure deficit (VPD) in both stands; it was used for calculating the ratio of intercellular to ambient CO₂ (Ci/Ca). A remarkable similarity was observed in the relationship between Ci/Ca and time-lagged VPD in these two forests despite large differences in hydraulic characteristics. This similarity emerged as a result of physiological adjustments that compensated for differences in plant hydraulic characteristics, as predicted by a recently proposed equilibrium hypothesis, and has implications to ecophysiological models. We found that in the broadleaf forest, the 13C of forest floor CO₂ efflux dominated the 13C_R, while in the younger pine forest, the 13C of foliage respired CO₂ dominated 13C_R. This dependence resulted in a more variable 13C_R in the pine forest when compared to the broadleaf forest due to the larger photosynthetic contribution. Given the sensitivity of the atmospheric inversion models to 13C_R, the results demonstrate that these models could be improved by accounting for stand characteristics, in addition to previously recognized effects of moisture availability, when estimating 13C_R.