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Partitioning Respiration of C3‐C4 Mixed Communities Using the Natural Abundance 13 C Approach ‐ Testing Assumptions in a Controlled Environment
Author(s) -
Schnyder H.,
Lattanzi F. A.
Publication year - 2005
Publication title -
plant biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.871
H-Index - 87
eISSN - 1438-8677
pISSN - 1435-8603
DOI - 10.1055/s-2005-872872
Subject(s) - respiration , biology , shoot , lolium perenne , biomass (ecology) , biomass partitioning , botany , agronomy , poaceae
Contributions of C3 and C4 plants to respiration of C3‐C4 ecosystems can be estimated on the basis of their contrasting 13 C discrimination. But accurate partitioning requires accurate measurements of the isotope signature of whole system respiratory CO 2 (δ R ), and of its members (δ 3 and δ 4 ). Unfortunately, experimental determination of representative δ 3 and δ 4 values is virtually impossible in nature, generating a need for proxies (surrogates) of δ 3 and δ 4 values (e.g., the δ of leaf biomass). However, recent evidence indicates that there may be systematic differences among the δ of respiratory and biomass components. Thus, partitioning may be biased depending on the proxy. We tested a wide range of biomass‐ and respiration‐based δ proxies for the partitioning of respiration of mixed Lolium perenne (C3) ‐ Paspalum dilatatum (C4) stands growing at two temperatures inside large 13 CO 2 / 12 CO 2 gas exchange chambers. Proxy‐based partitioning was compared with results of reference methods, including (i) the δ of whole plant respiratory CO 2 (δ 3 and δ 4 ) or (ii) respiration rate of intact C3 and C4 plants. Results of the reference methods agreed near perfectly. Conversely, some proxies yielded erroneous partitioning results. Partitioning based on either the δ of shoot or root respiratory CO 2 produced the worst bias, because shoot respiratory CO 2 was enriched in 13 C by several ‰ and root respiratory CO 2 was depleted by several ‰ relative to whole plant respiratory CO 2 . Use of whole plant or whole shoot biomass δ gave satisfactory partitioning results under the constant conditions of the experiments, but their use in natural settings is cautioned if environmental conditions are variable and the time scales of respiration partitioning differ strongly from the residence time of C in biomass. Other biomass‐based proxies with faster turnover (e.g., leaf growth zones) may be more useful in changing conditions.