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Patchiness is a critical functional feature of arid lands, increasing productivity and diversity, but there is little information on the long-term dynamics of patch formation. While plant-created heterogeneity is widespread, grazing reduces plant density, hence removing patchiness. Patchiness is also associated with fallen logs and it is particularly important to assess this association in grazed areas, as there are few patches which are not created by living plants. We studied differences in soil nutrient content and soil seed bank associated with the presence of logs in the long ungrazed Koonamore Vegetation Reserve and an adjacent heavily grazed paddock in chenopod shrublands of South Australia. We studied soil properties associated with fallen logs of unknown age, and others known to have persisted for up to 78 years. Logs acted as traps for soil nutrients and seeds. Organic carbon was higher in soils associated with logs, and also higher inside the reserve than in the grazed paddock. Propagule number and species richness were higher next to logs than in open spaces and viable seeds were in much higher abundance next to logs in the grazed paddock than any other site. Increased time in situ of a log had a relatively small effect on soil organic carbon and total nitrogen. Logs act as resource traps which may enhance the diversity of the system, and may be particularly important for maintaining patches of resources in areas of severe grazing damage. Hence, their preservation should be incorporated into management schemes. [Correction added on 3 March 2015, after online publication: The following parts in the abstract have been edited. 'Organic carbon and total nitrogen were higher in soils associated with logs' has been corrected to 'Organic carbon was higher in soils associated with logs', and 'had a relatively small effect on soil organic carbon, total nitrogen and available potassium' has been corrected to 'had a relatively small effect on soil organic carbon and total nitrogen'.] [ABSTRACT FROM AUTHOR]

We investigated the effects of waterlogging and salinity on the water relations of Eucalyptus gracilis F. Muell. growing within the Stockyard Plain Disposal Basin Reserve, 15 km southwest of Waikerie, South Australia. Presence and depth of the saline groundwater had relatively little effect on the water relations of the trees even when large differences in tree health were visible. Predawn water potential, stomatal conductance, and foliar sodium and potassium concentrations were similar for all individuals independent of the depth and salinity of the groundwater. As expected, the severity of water stress increased over summer when predawn water potentials became progressively more negative and foliar salt concentrations increased. These changes occurred in all plants independent of depth or salinity of the groundwater.