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Extensive cattle grazing is the dominant land use in northern Australia. It has been suggested that grazing intensity and rainfall have profound effects on the dynamics of soil nutrients in northern Australia's semi-arid rangelands. Previous studies have found positive, neutral and negative effects of grazing pressure on soil nutrients. These inconsistencies could be due to short-term experiments that do not capture the slow dynamics of some soil nutrients and the effects of interannual variability in rainfall. In a long-term cattle grazing trial in northern Australia on Brown Sodosol-Yellow Kandosol complex, we analysed soil organic matter and mineral nitrogen in surface soils (0-10 cm depth) 11,12 and 16 years after trial establishment on experimental plots representing moderate stocking (stocked at the long- term carrying capacity for the region) and heavy stocking (stocked at twice the long-term carrying capacity). Higher soil organic matter was found under heavy stocking, although grazing treatment had little effect on mineral and total soil nitrogen. Interannual variability had a large effect on soil mineral nitrogen, but not on soil organic matter, suggesting that soil nitrogen levels observed in this soil complex may be affected by other indirect pathways, such as climate. The effect of interannual variability in rainfall and the effects of other soil types need to be explored further. Received 27 August 2014, accepted 12 May 2015, published online 11 September 2015, Introduction Many of northern Australia's soils are low in nutrients. This is because Australian landscapes are weathered relics of earlier pedological processes (Mott et at. 1985). In addition, northern Australia [...]

In arid ecosystems, shrub patches are regarded as “islands of fertility,” enriched in resources that facilitate growth of herbaceous vegetation. It is often assumed that the modulation of resources and the effect that it has on herbaceous vegetation are homogeneous within each shrub patch. We examined the modulated resources in terms of their fine-scale spatial extent, level, and response to anthropogenic disturbances, that is, canopy removal and grazing. We defined three patch types—core of shrub patch, periphery of shrub patch, and intershrub patch—and recorded their levels of soil nutrients (organic matter, potassium, phosphorus, nitrate, and ammonium) and temperature regimes, with and without canopy removal, and/or grazing. Overall, our study found higher soil-nutrient contents and lower maximum temperatures at the core of the shrub patch than in the intershrub matrix. However, we also found that resource modulation was not spatially homogeneous within the shrub patch: soil nutrient levels were higher in the core than at the periphery. Anthropogenic disturbances did not affect soil nutrients within the 2-year time scale of our study. Our results emphasize the importance of examining the landscape at the spatial scale of the modulated resources, in order to develop patch management that increases productivity and diversity, and prevents desertification. [ABSTRACT FROM PUBLISHER]

Experimentation has been the cornerstone of much of integrated pest management (IPM) research. Here, we aim to open a discussion on the possible merits of expanding the use of observational studies, and in particular the use of data from farmers or private pest management consultants in "ecoinformatics" studies, as tools that might complement traditional, experimental research. The manifold advantages of experimentation are widely appreciated: experiments provide definitive inferences regarding causal relationships between key variables, can produce uniform and high-quality data sets, and are highly flexible in the treatments that can be evaluated. Perhaps less widely considered, however, are the possible disadvantages of experimental research. Using the yield-impact study to focus the discussion, we address some reasons why observational or ecoinformatics approaches might be attractive as complements to experimentation. A survey of the literature suggests that many contemporary yield-impact studies lack sufficient statistical power to resolve the small, but economically important, effects on crop yield that shape pest management decision-making by farmers. Ecoinformatics-based data sets can be substantially larger than experimental data sets and therefore hold Out the promise of enhanced power. Ecoinformatics approaches also address problems at the spatial and temporal scales at which farming is conducted, can achieve higher levels of "external validity," and can allow researchers to efficiently screen many variables during the initial, exploratory phases of research projects. Experimental, observational, and ecoinformatics-based approaches may, if used together, provide more efficient solutions to problems in pest management than can any single approach, used in isolation. [ABSTRACT FROM AUTHOR]

Sarcopoterium spinosum (prickly burnet) is a dominant shrub species in many semiarid shrublands of the eastern Mediterranean region. The annual plant community under the shrub canopy differs significantly from that in open (intershrub) patches in terms of abundance, biomass, and species diversity. This shrub/open contrast in vegetation closely matches the contrast in abiotic conditions, which is mainly attributed to the engineering effects of the shrub. However, S. spinosum may also act as a seed barrier between patch types, thus controlling which seeds are exposed to the contrasting conditions. As the canopy of S. spinosum is shaped like a tightly packed cushion, we hypothesized that it prevents or slows the movement of seeds across patch boundaries. We tested this hypothesis by comparing the seed rains under intact shrubs, under shrubs whose canopies were removed, and in open patches. We compared the distribution among the patch types of species at the seed stage with that of the same species at the adult stage. We found a sharp contrast in seed population between seed traps under intact shrubs and those in open patches, and a much weaker contrast between seed traps under removed shrub canopies and those in open patches. However, between-patch differences at the seed stage tightly paralleled those seen at the adult stage, strongly suggesting that within-patch dispersal is much more probable than between-patch dispersal. The implications of these dispersal patterns for population and community dynamics are discussed. In addition, we discuss the consequences of our findings for shrub-annuals interaction. [ABSTRACT FROM AUTHOR]

Hairy stork's-bill (Erodium crassifolium) (HSB) is one of the few Geraniaceae species that produce tubers. While HSB tubers were occasionally used as a food source by desert nomads, they have not yet been taken up in the modern kitchen. Recently, HSB tubers were recognized as harboring potential to become an industrial pharmaceutical crop. The objective of this study was to determine a set of agricultural practices that would maximize the yield of the bioactive compounds of the present HSB genetic material. A generous and consistent irrigation regime of about 700 mm season−1 increased tuber yield and size. The optimal plant density on sandy soils was 16–20 plants m−2. Mineral nutrition, applied through fertigation, increased tuber yield from 0.6 to almost 1 kg m−2. Source-sink manipulations (consistent pruning of the reproductive organs) almost doubled the tuber yield. During 10 years of research, the adopted agricultural practices increased yield by an order of magnitude (from about 0.2–2.0 kg m−2) without any dilution of the bioactive compounds. Nevertheless, further research and development are required to achieve HSB potential as an industrial field crop, including selection and breeding of outstanding infertile clones, optimization of fertigation, and development of various concrete pharmaceutical products. [ABSTRACT FROM AUTHOR]