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Australian mulga ecosystems – 13 C and 15 N natural abundances of biota components and their ecophysiological significance
Author(s) -
Pate J. S.,
Unkovich M. J.,
Erskine P. D.,
Stewart G. R.
Publication year - 1998
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1046/j.1365-3040.1998.00359.x
Subject(s) - perennial plant , herbaceous plant , botany , shoot , vegetation (pathology) , woody plant , biogeochemistry , abundance (ecology) , biology , agronomy , ecology , medicine , pathology
Samples of recently produced shoot material collected in winter/spring from common plant species of mulga vegetation in eastern and Western Australia were assayed for 13 C and 15 N natural abundance. 13 C analyses showed only three of the 88 test species to exhibit C 4 metabolism and only one of seven succulent species to be in CAM mode. Non‐succulent winter ephemeral C 3 species showed significantly lower mean δ 13 C values (– 28·0‰) than corresponding C 3 ‐type herbaceous perennials, woody shrubs or trees (– 26·9, – 25·7 and – 26·2‰, respectively), suggesting lower water stress and poorer water use efficiency in carbon acquisition by the former than latter groups of taxa. Corresponding values for δ 15 N of the above growth and life forms lay within the range 7·5–15·5‰. δ 15 N of soil NH 4 + (mean 19·6‰) at a soft mulga site in Western Australia was considerably higher than that of NO 3 – (4·3‰). Shoot dry matter of Acacia spp. exhibited mean δ 15 N values (9·10 ± 0·6‰) identical to those of 37 companion non‐N 2 ‐fixing woody shrubs and trees (9·06 ± 0·5‰). These data, with no evidence of nodulation, suggested little or no input of fixed N 2 by the legumes in question. However, two acacias and two papilionoid legumes from a dune of wind‐blown, heavily leached sand bordering a lake in mulga in Western Australia recorded δ 15 N values in the range 2·0–3·0‰ versus 6·4–10·7‰ for associated non‐N 2 ‐fixing taxa. These differences in δ 15 N, and prolific nodulation of the legumes, indicated symbiotic inputs of fixed N in this unusual situation. δ 15 N signals of lichens, termites, ants and grasshoppers from mulga of Western Australia provided evidence of N 2 fixation in certain termite colonies and by a cyanobacteria‐containing species of lichen. Data are discussed in relation to earlier evidence of nitrophily and water availability constraints on nitrate utilization by mulga vegetation.