Effects of seed mixture and management on beetle assemblages of arable field margins

Beetle assemblages and their response to plant community composition and architectural structure were monitored from 2002 to 2006 within arable field margins. Field margins were sown with either tussock grass and forbs, fine grass and forbs or grass only seed mixtures. After an establishment year, field margins were managed using standard sward cuts, scarification, or graminicide application. For predatory beetles, overall density was greatest where tussock grasses were included within the seed mixtures, while the densities of phytophagous beetles were greatest where forbs were present. Unexpectedly, species rarefaction curves suggested that phytophagous beetle species richness was greatest where field margins were established using a grass only seed mixture. The structure of the beetle assemblages, i.e., the relative abundances of individual species, was largely dependent on seed mixture, although margin management also played an important role. The results suggest that field margins established using seed mixtures containing tussock grasses and forbs would be expected to provide the greatest resources for beetles, at least at local scales. However, the use of a single standardised seed mixture for margin establishment would result in a homogenisation of beetle assemblages at a regional scale. (C) 2008 Elsevier B.V. All rights reserved.

Do seed lists have a future?

In the 1960s Taxon published articles aimed at improving botanical Seed Lists. We compared suggestions made then with the situation in 2007. Sadly the majority of problems raised in the original manuscripts were still evident today. Botanic gardens must improve if this practice is to survive.

Management of grass weeds in overwintering stubbles

With uncertainty concerning the future of set-aside, over-wintering stubble is an attractive management option within the agri-environment scheme. Over-wintering stubbles could be included as part of rotational set-aside, benefiting farmland biodiversity. However, there is little research on managing stubbles to maximise weed seed loss, so farmers may be reluctant to adopt this option for fear of increased weed infestation. The purpose of this investigation is to develop effective management of over-wintering stubbles to minimise pernicious grass weeds in sequential crops, whilst maintaining beneficial species diversity. Research has focused on four annual grass-weeds (Alopecurus myosuroides, Anisantha sterilis, Bromus commutatus and Lolium multiflorum) of increased occurrence and/or resistance to herbicides. Hitherto, work has concentrated on the effects of stubble manipulation on weed seed germination and mortality, in particular by straw spreading or removal after harvest. The dynamics of artificially inoculated weed populations were monitored from harvest until early spring. Results obtained indicate that where straw is retained on the soil surface, it provides a favourable microclimate for seed depletion of Anisantha sterilis and Bromus commutatus through germination. Conversely, greater depletion of Alopecurus myosuroides and Lolium multiflorum seed occurred from stubbles in which a straw layer was absent. Seed recovery work provided evidence that most seeds remaining ungerminated throughout the trial period were still viable, but a large proportion of the seeds sown were unaccounted for. As these species are not generally favoured as a food source, the as yet unknown fate of these seeds has implications for subsequent grass-weed infestations.

The influence of winter oilseed rape (Brassica napus ssp oleifera var. biennis) canopy size on grass weed growth and grass weed seed return

Four experiments conducted over three seasons (2002-05) at the Crops Research Unit, University of Reading, investigated effects of canopy management of autumn sown oilseed rape (Brassica napus L. ssp. oleifera var. biennis (DC.) Metzg.) on competition with grass weeds. Emphasis was placed on the effect of the crop on the weeds. Rape canopy size was manipulated using sowing date, seed rate and the application of autumn fertilizer. Lolium multiflorum Lam., L. x boucheanum Kunth and Alopecurus myosuroides Huds. were sown as indicative grass weeds. The effects of sowing date, seed rate and autumn nitrogen on crop competitive ability were correlated with rape biomass and fractional interception of photosynthetically active radiation (PAR) by the rape floral layer, to the extent that by spring there was good evidence of crop: weed replacement. An increase in seed rate up to the highest plant densities tested increased both rape biomass and competitiveness, e.g. in 2002/3, L. multiflorum head density was reduced from 539 to 245 heads/m(2) and spikelet density from 13 170 to 5960 spikelets/m(2) when rape plant density was increased from 16 to 81 plants/m(2). Spikelets/head of Lolium spp. was little affected by rape seed rate, but the length of heads of A. myosuroides was reduced by 9 % when plant density was increased from 29-51 plants/m(2). Autumn nitrogen increased rape biomass and reduced L. multiflorum head density (415 and 336 heads/m(2) without and with autumn nitrogen, respectively) and spikelet density (9990 and 8220 spikelets/m(2) without and with autumn nitrogen, respectively). The number of spikelets/head was not significantly affected by autumn nitrogen. Early sowing could increase biomass and competitiveness, but poor crop establishment sometimes overrode the effect. Where crop and weed establishment was similar for both sowing dates, a 2-week delay (i.e. early September to mid-September) increased L. multiflorum head density from 226 to 633 heads/m(2) and spikelet density from 5780 to 15 060 spikelets/m(2).

Post dispersal weed seed predation by avian and non-avian predators

Seed predation by avian and non-avian predators was quantified in the boundaries and cropped areas of cereal fields by presenting known quantities of seed with and without exclusion cages. Predator encounter-rates with the dishes exceeded 99%. Birds removed on average 6.7% seed from the dishes during the seven-day trials compared to 51% by non-avian predators. A comparison was made of the causal factors responsible for predation of Avena fatua, Chenopodium album and Cirsium arvense seeds. A. fatua seeds were preyed most heavily by both avian and non-avian predators. Seed removal by birds was greater in the cropped area than in the field boundary, non-avian predators being generally more active in the field boundary. Seed predation by birds was greater in spring than in any other season, whilst losses to other animals were greater during autumn and winter. Although, birds were not the main seed predators in cereal fields, they may contribute to weed seed depletion, of relevance to reduced-input farming systems where herbicides use is restricted.

Post-dispersal seed predation of non-target weeds in arable crops

Field experiments were conducted to quantify the natural levels of post-dispersal seed predation of arable weed species in spring barley and to identify the main groups of seed predators. Four arable weed species were investigated that were of high biodiversity value, yet of low to moderate competitive ability with the crop. These were Chenopodium album, Sinapis arvensis, Stellaria media and Polygonum aviculare. Exclusion treatments were used to allow selective access to dishes of seeds by different predator groups. Seed predation was highest early in the season, followed by a gradual decline in predation over the summer for all species. All species were taken by invertebrates. The activity of two phytophagous carabid genera showed significant correlations with seed predation levels. However, in general carabid activity was not related to seed predation and this is discussed in terms of the mainly polyphagous nature of many Carabid species that utilized the seed resource early in the season, but then switched to carnivory as prey populations increased. The potential relevance of post-dispersal seed predation to the development of weed management systems that maximize biological control through conservation and optimize herbicide use, is discussed.

Mutant alleles at the rugosus loci in pea affect seed moisture sorption isotherms and the relations between seed longevity and moisture content

Pea (Pisum sativum L.) mutant near-isogenic lines (RRrbrb, rrRbRb, rrrbrb) with lower starch but higher lipid contents, brought about by lesions in the starch biosynthetic pathway, had seed moisture sorption isotherms displaced below that of the wild type (RRRbRb). The negative logarithmic relationship between seed longevity and seed storage moisture content (%, f.wt basis), determined in hermetic storage at 65 °C, also differed: longevity in the mutant near-isogenic lines was poorer and less sensitive to moisture content than in the wild type (i.e. CW was lower). The low-moisture-content limit (mc) to this relation also differed, being lower in the mutant near-isogenic lines (5.4–5.9%) than in the wild type (6.1%). In contrast, all four near-isogenic lines showed no difference (P >0.25) in the negative semi-logarithmic relationship between equilibrium relative humidity (ERH) and seed longevity. It is concluded that the effect of these alleles at the r and rb loci on seed longevity was largely indirect; a consequence of their effect on seed composition and hence on moisture sorption isotherms. However, this explanation could not be invoked at moisture contents below mc where differences in longevity remained substantial (RRRbRb double that of rrrbrb). Hence, these mutant alleles affected seed longevity directly at very low moisture contents.

Antioxidant and tyrosinase inhibitory activity of mango seed kernel by product

The antioxidant and tyrosinase inhibitory properties of extracts of mango seed kernel (Mangifera indica L.), which is normally discarded when the fruit is processed, were studied. Extracts contained phenolic components by a high antioxidant activity, which was assessed in homogeneous solution by the 2,2-diphenyt-1-picrylhydrazyl radical and 2,2'-azinobis (3-ethylbenzothialozinesulfonic acid) radical cation-scavenging assays and in an emulsion with the ferric thiocyanate test. The extracts also possessed tyrosinase inhibitory activity. Drying conditions and extraction solvent were varied, and optimum conditions for preparation of mango seed kernel extract were found to be sun-drying with ethanol extraction at room temperature. Refluxing in acidified ethanol gave an increase in yield and the obtained extract had the highest content of total phenolics, and also was the most effective antioxidant with the highest radical-scavenging, metal-chelating and tyrosinase inhibitory activity. The extracts did not cause acute irritation of rabbit skins. Our study for the first time reveals the high total phenol content, radical-scavenging, metal-chelating and tyrosinase inhibitory activities of the extract from mango seed kernel. This extract may be suitable for use in food, cosmetic, nutraceutical and pharmaceutical applications. (C) 2009 Elsevier Ltd. All rights reserved.

The consequences of diffractively spreading beams in ultrafast THz spectroscopy

There are established methods for calculating optical constants from measurements using a broadband terahertz (THz) source. Applications to ultrafast THz spectroscopy have adopted the key assumption that the THz beam is treated as a normal incidence plane-wave. We show that this assumption results in a frequency-dependent systematic error, which is compounded by distortion of the beam on introduction of the sample.

A dual QPSK soft-demapper for ECMA-368 exploiting time-domain spreading and guard interval diversity

When considering the relative fast processing speed and low power requirements for Wireless Personal Area Networks (WPAN) and Wireless Universal Serial Bus (USB) consumer based products, then the efficiency and cost effectiveness of these products become paramount. This paper presents an improved soft-output QPSK demapper suitable for the products above that not only exploits time diversity and guard carrier diversity, but also merges the demapping and symbol combining functions together to minimize CPU cycles, or memory access dependant upon the chosen implementation architecture. The proposed demapper is presented in the context of Multiband OFDM version of UWB (ECMA-368) as the chosen physical implementation for high-rate Wireless USB.

A dual QPSK soft-demapper for multiband OFDM exploiting time-domain spreading and guard interval diversity

When considering the relative fast processing speeds and low power requirements for Wireless Personal Area Networks (WPAN) including Wireless Universal Serial Bus (WUSB) consumer based products, then the efficiency and cost effectiveness of these products become paramount. This paper presents an improved soft-output QPSK demapper suitable for the products above that not only exploits time diversity and guard carrier diversity, but also merges the demapping and symbol combining functions together to minimize CPU cycles, or memory access dependant upon the chosen implementation architecture. The proposed demapper is presented in the context of Multiband OFDM version of Ultra Wideband (UWB) (ECMA-368) as the chosen physical implementation for high-rate Wireless US8(1).