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Changes in the δ 13 C values of trees during a tropical rainy season: some effects in addition to diffusion and carboxylation by rubisco?
Author(s) -
Terwilliger Valery J.
Publication year - 1997
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.3732/ajb.84.12.1693
Subject(s) - evergreen , biology , canopy , wet season , deciduous , dry season , botany , rubisco , δ13c , tree canopy , evergreen forest , tropical savanna climate , agronomy , horticulture , photosynthesis , ecosystem , ecology , physics , quantum mechanics , stable isotope ratio
The δ 13 C values of deciduous and evergreen tree leaves were compared in open and closed‐ canopy environments throughout a rainy season in Panamá. Newly emerging leaves had higher δ 13 C values than older leaves of all seedlings and trees at all dates sampled. This was apparently not caused by a decline in water use efficiency as leaves develop because instantaneous c i / c a was significantly higher in newly emerging than in expanded leaves on the same twigs of trees in the field as well as on seedlings growing in a controlled, unchanging environment. Higher δ 13 C values in newly emerging leaves occurred across diverse environmental comparisons. For example, leaves emerging during the rainy season had higher δ 13 C values than corresponding mature leaves that had emerged both during the dry season and when water was abundant. The early enrichment in 13 C may thus reflect the translocation of carbon to initiate a new leaf. Furthermore, the lack of sensitivity of this enrichment to a microclimate suggests that it might be the result of processes that occur after carbon fixation by Rubisco. Other changes in δ 13 C values as leaves developed may also have resulted from carbon translocation processes. Foliar δ 13 C decreased significantly after most of the leaf biomass of the deciduous Apeiba membranacea had developed. The δ 13 C values of the evergreen Cecropia insignis were lower in the open canopy than in closed‐canopy forests at the end of the rainy season. These findings suggest that the δ 13 C values of leaves can yield ecological information about the allocation of carbon within trees.