Namibian rainfall and the 1933/34 Benguela Nino

KlimawandelHistorical multi-year records of different length available from two Namibian rainfall stations and shorter series for ten rainy seasons (July 1928- June 1938), compiled by GELLERT (1955) from 70 stations distributed irregularly in the Namibian hinterland, are reanalysed in context with updated monthly series of the sea surface temperature anomaly. These series describe changes in thermal conditions at the surface of the eastern South-Atlantic (2.5° - 37.5° S, 17.5° W - 17.5°E) on the base of gridded 5° x5°-fields compiled by KAPLAN et al. (1998). It is shown that the extreme Benguela Niño 1933/34, which was reported manifold in the literature, coincides with enhanced precipitation in the Namibian hinterland and that strong thermal contrasts between exceptional warm coastal waters (2.5° - 27.5° S, 12.5° E) and colder offshore waters around 27.5° S, 7.5° W accompanied this phenomenon. This thermal dipole is regionally fixed and positive peaks, which exceed the value of 0.5°C, exhibit a quasi-cycle of about 14 years coinciding with that of ‘wet years’ detected over the St. Helena Island as well as over the Namibian hinterland. It is concluded that the relationship between this thermal dipole and extreme Namibian rainfall mainly results from (i) the south-westward displacement of the climatic position of the Intertropical Convergence Zone (ITCZ), the belt of the south-east trade wind, and the core of the cold Benguela Current (BC), and (ii) enhanced evaporation over the Gulf of Guinea and the belt of warm coastal waters reaching the latitude of about 26° S. Concerning so-called Namibian ‘wet years’, dominating air flows involve an enhanced south and/ or south-westward advection of humid equatorial air masses towards the Namibian hinterland to reach comparable importance than those originating from the West Indian Ocean

The Effects of Strategic Nitrogen Fertiliser Application During the Cool Season on the Composition of a Perennial Ryegrass-White Clover Pasture in the Western Cape Province of South Africa

Application of fertiliser N to stimulate DM production of perennial ryegrass-white clover pastures during the cool season can be an important management tool. Application of fertiliser N should however maintain clover contents between 30 and 50 percent (Martin, 1960; Harris, 1994). The aim of the study was to develop a better understanding of the effect of a strategic N fertiliser application during the cool season on the grass-clover balance and to identify possible management guidelines that would maximise dry matter production without suppressing clover content to values lower than required to maintain the benefit of clover in the pasture

Seed-drill opener type and crop residue load affect canola establishment, but only residue load affects yield

Handling crop residue during planting operations is a challenge to conservation agriculture (CA) farmers worldwide. It remains unclear which tools are most effective in which conditions. Canola (Brassica napus L.), an oilseed crop widely used in rotation with cereals, is particularly sensitive to seedbed conditions, and thus may be influenced by residue loads and the choice of seed-drill openers. To identify optimal planting practices, this study compared the performance of disc and tine openers on canola establishment, growth, and yield under differing residue loads in a Mediterranean-type climate region. First, soil disturbance caused by disc and tine openers was evaluated to assess their effect on seedbed conditions; and second, the interacting effects of the openers with different residue loads was investigated. Tine openers and low crop residue loads resulted in the best (P 0.05)

Geniculo-Cortical Projection Diversity Revealed within the Mouse Visual Thalamus

This is the final version of the article. It was first available from PLOS via http://dx.doi.org/10.1371/journal.pone.0144846All dLGN cell co-ordinates, V1 injection sites, dLGN boundary coordinates, experimental protocols and analysis scripts are available for download from figshare at https://figshare.com/s/36c6d937b1844eec80a1.The mouse dorsal lateral geniculate nucleus (dLGN) is an intermediary between retina and primary visual cortex (V1). Recent investigations are beginning to reveal regional complexity in mouse dLGN. Using local injections of retrograde tracers into V1 of adult and neonatal mice, we examined the developing organisation of geniculate projection columns: the population of dLGN-V1 projection neurons that converge in cortex. Serial sectioning of the dLGN enabled the distribution of labelled projection neurons to be reconstructed and collated within a common standardised space. This enabled us to determine: the organisation of cells within the dLGN-V1 projection columns; their internal organisation (topology); and their order relative to V1 (topography). Here, we report parameters of projection columns that are highly variable in young animals and refined in the adult, exhibiting profiles consistent with shell and core zones of the dLGN. Additionally, such profiles are disrupted in adult animals with reduced correlated spontaneous activity during development. Assessing the variability between groups with partial least squares regression suggests that 4?6 cryptic lamina may exist along the length of the projection column. Our findings further spotlight the diversity of the mouse dLGN?an increasingly important model system for understanding the pre-cortical organisation and processing of visual information. Furthermore, our approach of using standardised spaces and pooling information across many animals will enhance future functional studies of the dLGN.Funding was provided by a Wellcome Trust grant jointly awarded to IDT and SJE (083205, www.wellcome.ac.uk), and by MRC PhD Studentships awarded to MNL and ACH (http://www.mrc.ac.uk/)

Accommodating Dynamic Oceanographic Processes and Pelagic Biodiversity in Marine Conservation Planning

Pelagic ecosystems support a significant and vital component of the ocean's productivity and biodiversity. They are also heavily exploited and, as a result, are the focus of numerous spatial planning initiatives. Over the past decade, there has been increasing enthusiasm for protected areas as a tool for pelagic conservation, however, few have been implemented. Here we demonstrate an approach to plan protected areas that address the physical and biological dynamics typical of the pelagic realm. Specifically, we provide an example of an approach to planning protected areas that integrates pelagic and benthic conservation in the southern Benguela and Agulhas Bank ecosystems off South Africa. Our aim was to represent species of importance to fisheries and species of conservation concern within protected areas. In addition to representation, we ensured that protected areas were designed to consider pelagic dynamics, characterized from time-series data on key oceanographic processes, together with data on the abundance of small pelagic fishes. We found that, to have the highest likelihood of reaching conservation targets, protected area selection should be based on time-specific data rather than data averaged across time. More generally, we argue that innovative methods are needed to conserve ephemeral and dynamic pelagic biodiversity

The effect of fertiliser N rates on growth of perennial ryegrass (Lolium perenne) and white clover (Trifolium repens) grown at high soil water levels under controlled conditions

The response of perennial ryegrass and white clover to fertiliser N rates of 0, 30, 60, 120 and 180 kg N ha-1 when grown at soil water potentials of -10, -20, -25 and -35 kPa were investigated. Increasing fertiliser N levels from 0 to 120 kg N ha-1 resulted in increased (P=0.05) perennial ryegrass primary dry matter production (PDM) at the end of the first regrowth cycle (31 days). Ryegrass PDM yield was influenced (P=0.05) by soil water potential, with higher yields recorded at the -10 and -20 kPa treatments compared to the -25 and -35 kPa treatments. White clover PDM production was not influenced by N rate or soil water potential. Carry-over fertiliser N caused increased (P=0.05) ryegrass residual dry matter (RDM) yields as fertiliser N rate was increased from 0, 30, or 60 kg N ha-1 to 120 and 180 kg N ha-1, while clover RDM production increased as fertiliser N rate was increased from 0 to 180 kg N ha-1. Higher (-10 and -20 kPa) soil water levels caused increased ryegrass RDM production, a response not observed in clover. Total dry matter (TDM) production (the accumulative dry matter production during a 60 day period following fertiliser N application) of ryegrass was significantly increased as fertiliser N rate was increased from 0 to 180 kg N ha-1. Higher ryegrass TDM yields at-10 kPa and -20 kPa were recorded at the higher (120 and 180 kg N ha-1) N application rates, but water content did not influence TDM production at the lower (0, 30 and 60 kg N ha-1) fertiliser N application rates. Clover TDM production was not influenced by the treatments applied.Articl

The effect of low soil temperature and fertiliser N rate on perennial ryegrass (Lolium perenne) and white clover (Trifolium repens) grown under controlled conditions

The response of perennial ryegrass and white clover to soil temperatures of 6, 12 and 18°C, and to nitrogen applications equivalent to 0, 50, 100 and 150 kg N ha-1, were investigated under controlled conditions. Ryegrass primary dry matter production (PDM) at the end of the first regrowth cycle (31 days) increased as fertiliser N rate was increased from 0 to 100 kg N ha-1. Residual dry matter production (RDM) at the end of the second regrowth cycle (60 days) and total dry matter production (TDM) over the two regrowth cycles were increased by all N application rates tested. Although yield responses were less at 6°C compared to 12 and 180°C, results clearly showed that N applications could be used to stimulate dry matter production of ryegrass during the cool season. White clover PDM, RDM and TDM were significantly influenced (P0.05) by soil temperature resulting in lower yields at 6°C. None of the fertiliser N treatments tested resulted in significant reductions in clover PDM, RDM and TDM. Increasing fertiliser N rates increased (P0.05) the number of ryegrass tillers, but stolon growing points of white clover were not affected. Leaf nitrogen content at the end of the first regrowth cycle was higher than levels regarded as adequate for optimum perennial ryegrass and white clover dry matter production. Results suggest that fertiliser N rates as high as 150 kg N ha-1 applied at low temperatures will stimulate perennial ryegrass dry matter production without any direct negative effect on white clover productivity.Articl