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The objective of this 3-year study was to investigate the relationships between soil salinity and ecophysiological responses of C3 and C4 native plant species around Lake Altham and Lake Coyrecup (both are salt lakes in Western Australia), and to evaluate their potential for use in the remediation of salt-affected soils. Three shrubs (Atriplex vesicaria, Tecticornia lepidosperma and T. indica) that grew in highly saline soil of average Na concentration greater than 300 mM had higher leaf δ13C and δ15N ratios. These species also had higher Na-to-K and Na-to-Ca ratios in both their leaves and stem xylem sap, indicating that these species accumulate high amounts of sodium in their tissues. In contrast, tree species Eucalyptus loxophleba, Casuarina obesa and Acacia acuminata grew in soil of average Na concentration of less than 100 mM and had lower values of δ15N, δ13C, Na content, and Na-to-K ratio in their leaves. These species also had lower xylem Na-to-K and Na-to-Ca ratios. Seasonal effects were observed in leaf total N content, leaf Na, xylem sap Na-to-K ratio and xylem sap Na-to-Ca ratio. Strong and significant positive correlations (r > 0.75; P

The TGB Osborn Vegetation Reserve at Koonamore, South Australia, is a 390-ha exclosure in semi-arid chenopod shrubland. The area was heavily overgrazed in 1925 when it was fenced to exclude sheep. Permanent quadrats and photopoints have been maintained to the present. Feral rabbits were sometimes numerous until the mid-1970s but have since been controlled. The records represent 50 years without sheep grazing, followed by 26 years without either sheep or rabbits. Dramatic seedling establishment events have occurred since 1978 for the following species: Acacia aneura Benth., Myoporum platycarpum R.Br., Senna artemesioides subsp. coriacea Randell, S. artemesioides subsp. petiolaris Randell, Acacia burkittii Benth., Dodonaea attenuata A.Cunn., Eremophila longifolia (R.Br.) F.Muell., E. sturtii R.Br. and Maireana pyramidata (Benth.) Paul G.Wilson. However, the chenopod shrubs Atriplex vesicaria Benth. and A. stipitata Benth. increased earlier and did not respond in the same way to episodic rainfall events or rabbit control. Numbers of Alectryon oleifolius (Desf.) S.T.Reynolds and Casuarina pauper F.Muell. ex L.A.S.Johnson have remained almost unchanged, whereas Maireana sedifolia (F.Muell.) Paul G.Wilson and M. astrotricha (L.Johnson) Paul G.Wilson have shown a very gradual increase over time. The data show evidence for both episodic and gradual change among different species.

The application of multiple pattern analysis (multiscale ordination) to a phase-differentiated sample of perennial saltbush (Atriplex vesicaria) rangeland, along with assessments of the vegetative and reproductive states of individual plants, served to indicate the importance of sheep in determining some scales of distributional pattern in the shrub population. By comparison with conventional pattern analysis, it is shown that multiple pattern analysis can be used to provide an economic description of 'total' pattern in temporally related phases of a monospecific plant population. It is demonstrated that the pattern-determining interaction between sheep and saltbush individuals is dependent on plant size, sex and location with respect of other shrub individuals, in particular due to the trampling of seedling and pioneer phases and the selective grazing of sexually mature shrubs by sheep.

The majority of pattern analyses of total density data collected from geographically separated populations of Atriplex vesicaria, both in the western Riverine Plain of New South Wales and in areas of north-western New South Wales, provided evidence of bi- or trimodal contagion. More detailed analyses of pattern in age-related phases of these populations exhibited most intense patterning in 'seedling' phases, with a progressive reduction of pattern intensity in subsequent ('pioneer', 'building' and 'mature') phases of the entire population. It has been found that the pattern of young individuals may be correlated with patterned variation in microtopography, as well as with water and nutrient availability, and that the indirect effects of grazing animals may be responsible for the intermediate scales of the mosaic pattern in populations of sexually mature individuals. The performance of A. vesicaria plants was assessed experimentally in relation to a range of natural soils, with associated watering and defoliation treatments, and in controlled nutrient solution culture. The results suggest that performance (as estimated by dry weight yield) is affected significantly by soil type, water stress and defoliation. In an experimental context the prime effect of soil variation on yield appeared to be mediated by variation in soil cation balance, a patterned balance that may have been historically induced in the field situation.

Reflection and transmission spectra were measured for the leaves of a number of species of South Australian arid zone vegetation, over the wavelength range 350- 1350 nm. Spectra were also obtained for several non-arid species for comparison. Coefficients of reflection, transmission, and absorption of solar radiation were calculated from these spectra, and also obtained from direct measurements made with a specially constructed reflecting hemisphere. The coefficients of reflection for the arid zone species covered a wide range of values, and the group as a whole could not be clearly separated from the comparison group on the basis of reflection or absorption coeficients. Of the species in the group, Atriplex vesicaria had the highest coefficient of reflection, and also the lowest coefficient of absorption.

The factors controlling the relative distribution of Atriplex vesicaria and Kochia sedifolia were obscure, and explanations in the literature unsatisfactory. This paper describes the results of an experimental approach to an understanding of these factors. A survey of the soils on which A. vesicaria and K. sedifolia are found in the arid zone of South Australia revealed that the distribution of the two species is usually correlated with the depth to which the soil is wetted by the normal rainfall. K. sedifolia, a deep-rooted species, is frequently found on soils which can be wetted to a depth of 2 ft or more. A. vesicaria, a shallow-rooted species, is found on soils in which a heavy clay subsoil or hardpan impedes penetration of water beyond 12 in. From experimental evidence it appears that: (1) either species can grow successfully in pots of the surface soil associated with the other species; (2) each community utilizes water at the same rate; (3) there is no difference between the two species in the rate of defoliation in response to drought conditions, when held at night either in a dry atmosphere or in one with a relative humidity exceeding 85 %; (4) A. vesicaria can reduce the percentage moisture in the soil to a significantly lower level than can K. sedifolia when subjected to drought. These observations are discussed in relation to field conditions, and hypotheses are proposed to explain why these two species are usually found in distinct communities. More detailed work is necessary to test these hypotheses. I.

These two species are shown to have a closely similar leaf anatomy, and this is fully described with relevant notes on all the minor points of difference. In discussion, the origin and development of the lamina are compared with other plant groups. The autecological significance of the vesicular hairs is also briefly considered from an anatomical point of view. Brief comments are made on the water-storage properties of the hypodermal layer. The widespread occurrence of the 'Kranz' type of assimilatory tissue (concentric to the xylem of the leaf veins) in the Australian species of Atriplex is noted. The need for further investigations on the thick-walled phloem elements and bundle sheath cells is stressed. A taxonomic significance is suggested for the peculiar ventral development of the midrib in both species.

The distribution pattern of Atriplex vesicaria (perennial saltbush) was examined in a number of locations extending from Hay in western New South Wales to Koonamore Station in South Australia. The populations sampled were from a range of locations exhibiting a variety of topographical, edaphic, and effective rainfall conditions. The scales and intensities of pattern varied considerably between sites, but in all sites there was evidence of contagion on at least two scales (both larger than could be attributed to the morphology of the individual plants) and in no instance was there evidence of uniform (underdispersed) distribution. The two major scales of pattern were attributable to the development of gregariousness and either the patchiness of nodulated limestone (or gypsum) in the soils or the development of gilgai relief. It was demonstrated for one site that drought stress had brought about an apparent decrease in the stocking density of A. vesicaria; this reduction of density was associated with a decline in pattern intensity, although the scales of pattern present in the original vegetation were maintained in the residual population.