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The Arabian Desert is characterised by very low rainfall and high evaporation, yet over 210 springs are on its northeastern edge in central Iraq along the Abu Jir lineament, which represents the western depositional margin of a foreland basin infilled by the floodplain sediments of the Tigris and Euphrates Rivers; there is little evidence of faulting. The springs discharge from gently east-dipping Paleocene–Eocene limestones, either where groundwater flowpaths intersect the ground surface or where groundwater flow is forced to the surface by confining aquitards. Calculated annual recharge to the aquifer system across the Arabian Desert plateau (130–500 million m3) is significant, largely due to rapid infiltration through karst dolines, such that karst porosity is the primary enabler of groundwater recharge. The recharge is enough to maintain flow at the Abu Jir springs, but active management of groundwater extraction for agriculture is required for their long-term sustainability. The hydrochemistry of the springs is determined by evaporation, rainfall composition (high SO4 concentrations are due to the dissolution of wind-blown gypsum in rainfall), and plant uptake of Ca and K (despite the sparse vegetation). Limestone dissolution has relatively little impact; many of the springs are undersaturated with respect to calcite and lack tufa/travertine deposits. The springs at Hit-Kubaysa contain tar and high levels of H2S that probably seeped upwards along subvertical faults from underlying oil reservoirs; this is the only location along the Abu Jir lineament where deep-seated faults penetrate to the surface. The presence of hydrocarbons reduces the Hit-Kubaysa spring water and converts the dissolved SO4 to H2S. [ABSTRACT FROM AUTHOR]

Coral cay soil chemical and physical properties were described from Coringa-Herald National Nature Reserve, Australia. Soil A horizons under littoral herblands and Argusia argentea shrubs were shallow and coarse textured. Interior soil A horizons, particularly under Pisonia grandis closed forest, were deeper (1.2 m) with finer textures. Average surface soil pH values ranged from pH 8.76 at the seashores to pH 8.09 in the interior. Average surface soil organic carbon ranged from 2.4% to 4.8%; and phosphorus (Colwell-P) concentrations ranged from 467 mg/kg to 882 mg/kg within the interior areas. Chemical fertility of all A horizons increased from the seashore to the island interior. The higher fertility levels are attributed to high organic matter contributed by vegetation, combined with activities of seabirds, particularly the burrowing wedge-tailed shearwater, Puffinis pacificus. Leaching of nutrients from surface soils is reflected in the rapid decline in soil fertility with depth. Deeper interior A horizons are interrupted by formation of an abrupt white C profile. It is speculated that the formation of this layer is the product of periodic 'washing' by a seasonally high fresh/brackish water table., CORINGA-HERALD National Nature Reserve (CHNNR) (Figure 1) is a remote locality of relatively high biodiversity in the northeastern Australian Exclusive Economic Zone. The soils of the five vegetated cays at [...]

In recent decades, the conventional equilibrium paradigm for explaining rangeland vegetation dynamics has been challenged. Proponents of an alternative non-equilibrium paradigm argue that in variable rangeland environments, external climatic events are critical to vegetation dynamics and there is little opportunity for plant-herbivore interactions to reach equilibrium. Understanding which paradigm more effectively describes an ecosystem has important consequences for management. In particular, some authors have argued that a focus on reducing stocking rates in non-equilibrium systems may be futile, and management should be opportunistic in response to unpredictable rainfall events. We measured herbaceous biomass and plant species richness and abundance at five 14-year exclosures on Innamincka Regional Reserve. Four were situated in the dunefields land system, and one on the Cooper Creek floodplain. We did not detect any significant differences between grazed and ungrazed treatments in total species richness or abundance, life form richness or abundance, or herbaceous biomass. Only one species, Portulaca oleracea, showed differences in abundance between treatments at more than one site, but the direction of these differences was not consistent. These results suggest that the non-equilibrium paradigm more accurately describes vegetation dynamics in the dunefields and floodplains of north-eastern South Australia. It is possible that some species had been lost from the study area prior to the establishment of the exclosures, thereby precluding recovery with protection from grazing; however, a regional analysis of the flora reveals little evidence of this. We argue that the dominance of ephemeral species confers resilience by limiting the development of strong feedbacks between grazing intensity and vegetation dynamics. Current grazing practices seem consistent with the conservation of plant species diversity across the dunefields and floodplains. Future studies should focus on the impacts of cattle grazing on areas of the landscape dominated by palatable perennials, as well as the small number of rare and potentially grazing-sensitive species identified. [ABSTRACT FROM AUTHOR]

The putative hybrid zone between Eucalyptus populnea and E. brownii is examined using morphological and molecular techniques. This species complex displays continuous morphological variation across the study area, which has been previously interpreted as the product of hybridization between allopatric species. A microsatellite analysis indicates that there was little genetic structuring across the morphological cline and only low levels of population differentiation. The nested clade analysis of the JLA+ region of the chloroplast DNA (cpDNA) indicates that the geographical distribution of cpDNA haplotypes is unlikely to be the result of historical hybridization events, and that restricted seed-mediated gene flow with isolation by distance is responsible for the phylogeographical distribution. A more plausible explanation for the origin and persistence of the morphological cline is that the process of continuous morphological diversification has been promoted by a directional selection gradient. This study addresses species status within Eucalyptus and the belief that hybridization is widespread and is an important process in the group's evolution. [ABSTRACT FROM AUTHOR]