32 resultados para Herbaceous perennial


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The efficacy of ‘sod removal’ as a fenland restoration technique was tested using an experimental approach at Montiaghs Moss Nature Reserve, Northern Ireland, from 2006 to 2008. The site suffered from rank growth of purple moor-grass Molinia caerulea which was out-competing herbaceous species. Soil was removed up to a depth of 15 cm completely denuding vegetation in the experimental plot exposing bare peat. By July 2007, 15.2% of sod-removal areas were revegetated; by October 2008 cover had risen to 64.6%. Of this cover, purple moor-grass accounted for only 9-11% compared to 78- 79% on control plots. Cover of other rank-forming grass species was also significantly reduced. Sod removal significantly increased the cover of species characteristic of fenlands including sedges Carex spp., rushes Juncus spp., marsh pennywort Hydrocotyle vulgaris and lesser spearwort Ranunculus flammula. It seems likely that sod removal, which lowered the surface of the peat, restored minerotrophic conditions and exposed the historical seed bank stimulating regeneration of some fenland specialists and pioneer species; this resulted in significantly higher species richness on sod removal plots than control plots two years after treatment. There was no demonstrable effect of sod removal on abundance of devil’s-bit scabious Succisa pratensis, the larval food plant of the Annex II listed marsh fritillary butterfly Euphydryas aurinia. We recommend that consideration should be given to artificially seeding devil’s-bit scabious soon after sod removal treatment to promote early recolonisation and to increase plant abundance on the site.

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Mineral prospecting and raising finance for ‘junior’ mining firms has historically been regarded as a speculative activity. For the regulators of securities markets upon which ‘junior’ mining companies seek to raise capital, a perennial problem has been handling not only the indeterminacy of scientific claims, but also the social basis of epistemic practices. This paper examines the production of a system of public warrant and associated knowledge practices intended to enable investors to differentiate between ‘destructive’ and ‘productive’ varieties of financial speculation. It traces the use of the notion of ‘disclosure’ in constructing and legitimizing the ‘juniors’ market in Canada. It argues that though the work of ‘economics’ may be necessary in the construction of markets, it is by no means sufficient. Attention must also be given to the ways in which legal models of ‘the free-market’ can be translated and constantly re-worked across the sites and spaces of regulatory practice, animating the geographies of markets.

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Arcellacea (testate lobose amoebae) communities were assessed from 73 sediment-water interface samples collected from 33 lakes in urban and rural settings within the Greater Toronto Area (GTA), Ontario, Canada, as well as from forested control areas in the Lake Simcoe area, Algonquin Park and eastern Ontario. The results were used to: (1) develop a statistically rigorous arcellacean-based training set for sedimentary phosphorus (Olsen P (OP)) loading; and (2) derive a transfer function to reconstruct OP levels during the post-European settlement era (AD1870s onward) using a chronologically well-constrained core from Haynes Lake on the environmentally sensitive Oak Ridges Moraine, within the GTA. Ordination analysis indicated that OP most influenced arcellacean assemblages, explaining 6.5% (p < 0.005) of total variance. An improved training set where the influence of other important environmental variables (e.g. total organic carbon, total nitrogen, Mg) was reduced, comprised 40 samples from 31 lakes, and was used to construct a transfer function for lacustrine arcellaceans for sedimentary phosphorus (Olsen P) using tolerance downweighted weighted averaging (WA-Tol) with inverse deshrinking (RMSEPjack-77pp; r2jack = 0.68). The inferred reconstruction indicates that OP levels remained near pre-settlement background levels from settlement in the late AD 1970s through to the early AD 1970s. Since OP runoff from both forests and pasture is minimal, early agricultural land use within the lake catchment was as most likely pasture and/or was used to grow perennial crops such as Timothy-grass for hay. A significant increase in inferred OP concentration beginning ~ AD 1972 may have been related to a change in crops (e.g. corn production) in the catchment resulting in more runoff, and the introduction of chemical fertilizers. A dramatic decline in OP after ~ AD 1985 probably corresponds to a reduction in chemical fertilizer use related to advances in agronomy, which permitted a more precise control over required fertilizer application. Another significant increase in OP levels after ~ AD 1995 may have been related to the construction of a large golf course upslope and immediately to the north of Haynes Lake in AD 1993, where significant fertilizer use is required to maintain the fairways. These results demonstrate that arcellaceans have great potential for reconstructing lake water geochemistry and will complement other proxies (e.g. diatoms) in paleolimnological research.

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A 40 cm thick primary bed of Old Crow tephra (131 ± 11 ka), an important stratigraphic marker in eastern Beringia, directly overlies a vegetated surface at Palisades West, on the Yukon River in central Alaska. Analyses of insect, bryophyte, and vascular plant macrofossils from the buried surface and underlying organic-rich silt suggest the local presence of an aquatic environment and mesic shrub-tundra at the time of tephra deposition. Autochthonous plant and insect macrofossils from peat directly overlying Old Crow tephra suggest similar aquatic habitats and hydric to mesic tundra environments, though pollen counts indicate a substantial herbaceous component to the regional tundra vegetation. Trace amounts of arboreal pollen in sediments associated with the tephra probably reflect reworking from older deposits, rather than the local presence of trees. The revised glass fission-track age for Old Crow tephra places its deposition closer to the time of the last interglaciation than earlier age determinations, but stratigraphy and paleoecology of sites with Old Crow tephra indicate a late Marine Isotope Stage 6 age. Regional permafrost degradation and associated thaw slumping are responsible for the close stratigraphic and paleoecological relations between Old Crow tephra and last interglacial deposits at some sites in eastern Beringia. © 2009 Elsevier Ltd.

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This chapter assesses ways in which the emergence in the long eighteenth century of a cluster of verse translations of Milton’s Poemata engendered an intellectual discourse and debate on translation itself, not dissimilar to the magazine warfare of the day. It argues that poetical renderings of Milton’s Latin verse, and the biographical and literary contexts in which they appeared, facilitated the interrogation of key issues that are still being debated by modern translation theorists: the nature and function of translation; the viability of rendering a source text in a target language that is also in this instance a poetic language; the potential ‘fetters’ which, in Drydenesque terms, might constrain ‘the verbal copier’; or by contrast the quasi-liberating fluency, the ‘fluent strategy’, attendant upon recourse to verse as translational medium; canonicity, amplification and omission; the much-debated issue of authorial equivalence, evinced here, it is suggested, by the editorial showcasing of the translator; and not least, the perennial question of translation as reading and critical interpretation. In short, verse renderings of Milton’s Latin poetry and the debates that they engendered assume a not inconsequential place in the history of translation theory, which, as Venuti notes, is forever concerned with ‘the changing relationships between the relative autonomy of the translated text and two other categories: equivalence and function.’

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Mineral prospecting and raising finance for ‘junior’ mining firms has historically been regarded as a speculative activity. For the regulators of securities markets upon which ‘junior’ mining companies seek to raise capital, a perennial problem has been handling not only the indeterminacy of scientific claims, but also the social basis of epistemic practices. This paper examines the production of a system of public warrant and associated knowledge practices intended to enable investors to differentiate between ‘destructive’ and ‘productive’ varieties of financial speculation. It traces the use of the notion of ‘disclosure’ in constructing and legitimizing the ‘juniors’ market in Canada. It argues that though the work of ‘economics’ may be necessary in the construction of markets, it is by no means sufficient. Attention must also be given to the ways in which legal models of ‘the free-market’ can be translated and constantly re-worked across the sites and spaces of regulatory practice, animating the geographies of markets.

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Biodiversity, a multidimensional property of natural systems, is difficult to quantify partly because of the multitude of indices proposed for this purpose. Indices aim to describe general properties of communities that allow us to compare different regions, taxa, and trophic levels. Therefore, they are of fundamental importance for environmental monitoring and conservation, although there is no consensus about which indices are more appropriate and informative. We tested several common diversity indices in a range of simple to complex statistical analyses in order to determine whether some were better suited for certain analyses than others. We used data collected around the focal plant Plantago lanceolata on 60 temperate grassland plots embedded in an agricultural landscape to explore relationships between the common diversity indices of species richness (S), Shannon's diversity (H'), Simpson's diversity (D1), Simpson's dominance (D2), Simpson's evenness (E), and Berger–Parker dominance (BP). We calculated each of these indices for herbaceous plants, arbuscular mycorrhizal fungi, aboveground arthropods, belowground insect larvae, and P. lanceolata molecular and chemical diversity. Including these trait-based measures of diversity allowed us to test whether or not they behaved similarly to the better studied species diversity. We used path analysis to determine whether compound indices detected more relationships between diversities of different organisms and traits than more basic indices. In the path models, more paths were significant when using H', even though all models except that with E were equally reliable. This demonstrates that while common diversity indices may appear interchangeable in simple analyses, when considering complex interactions, the choice of index can profoundly alter the interpretation of results. Data mining in order to identify the index producing the most significant results should be avoided, but simultaneously considering analyses using multiple indices can provide greater insight into the interactions in a system.

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Perennial rye-grass plants were grown at 15°C in microcosms containing soil sampled from field plots that had been maintained at constant pH for the last 30 years. Six soil pH values were tested in the experiment, with pH ranging from 4.3-6.5. After 3 weeks growth in the microcosms, plant shoots were exposed to a pulse of 14C-CO2. The fate of this label was determined by monitoring 14C-CO2 respired by the plant roots/soil and by the shoots. The 14C remaining in plant roots and shoots was determined when the plants were harvested 7 days after receiving the pulse label. The amount of 14C (expressed as a percentage of the total 14C fixed by the plant) lost from the plant roots increased from 12.3 to 30.6% with increasing soil pH from 4.3 to 6. Although a greater percentage of the fixed 14C was respired by the root/soil as soil pH increased, plant biomass was greater with increasing soil pH. Possible reasons for observed changes in the pattern of 14C distribution are discussed and, it is suggested that changes in the soil microbial biomass and in plant nitrogen nutrition may, in particular be key factors which led to increased loss of carbon from plant roots with increasing soil pH. © 1990 Kluwer Academic Publishers.

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Carbon distribution within perennial ryegrass was determined at different stages of plant development, by pulse-labelling laboratory and field-grown plants with 14C-CO2. During the early stages of growth (23-51 days), C distribution of laboratory grown plants was not markedly affected by plant age, with 12.4-24% of net assimilated label lost into the soil as root-soil respiration. The percentage of net assimilate translocated below ground was 20-28% during this stage of growth. At 65 days, the percentage of the label translocated below ground decreased to 8.1% of the net assimilate, with a subsequent decrease in root-soil respiration to 3.9%. The ability of the plant to fix the label (expressed in MBq g-1 oven dry total plant weight) decreased steadily as the plants aged. When the 30 day old plants were subjected to water stress (soil water potential -1.5 MPa) for 2 days before pulse-labelling, root-soil respiration of the pulse-label decreased compared with plants grown at field capacity. The distribution of a 14C pulse-label within perennial ryegrass grown under field conditions was found to be dependent on the age of the plants. For 4 week old plants, 67% of net assimilated label was translocated below ground, with 64.8% of this respired by the roots and soil. Less label was translocated below ground at subsequent pulse-labels from weeks 8 to 24. The proportion of label translocated below ground respired by the roots and soil also decreased. The investment of label in the plant shoots was found to be greater in field grown plants as compared to plants of the same age grown in a controlled, laboratory environment. © 1990.

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Perennial ryegrass was subjected to a range of anaerobic treatments. The distribution of C within the plant was determined by pulse labelling the shoots with 14C-CO2. A 5 h anaerobic period before pulse labelling reduced by 2.5-10 times the 14C remaining in the plants and released into the soil. The distribution of the 14C within the plant was also affected by anaerobiosis. Short periods of anaerobiosis (5 or 10 h) led to increased root-soil 14C respiration (monitored for 7 days). A longer period of anaerobiosis (48 h) initially inhibited root-soil 14C respiration, but when aerobiosis was restored. 57% of the total 14C fixed by the plant was respired by the roots-soil during the following 7 days compared to 19% for the aerobic control. There was a two-thirds reduction in the percentage C retained by the plants stressed for the 48 h compared to the aerobic control. At harvest, all anaerobic treatments were associated with more 14C remaining in the soil as a proportion of the total 14C fixed by the plant compared to the aerobic control. © 1990.

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Perennial rye-grass plants were pulse labelled with [14C]-CO2 over a range of temperatures (5-25°C). The fate of the label was determined within the plant and soil. The temperature at which plants were pulse labelled had a marked effect on the distribution of the label within the plant and soil system. Root-soil respiration increased from 5.7 to 24.15% when expressed as a percentage of net assimilated label. The percentage of label remaining in the plant root and in the soil was greater at 5 and 25°C, with a minimum for both these components at 15°C. At 15°C the percentage of net assimilated label that remained in the shoots was greater than at other temperatures, with this percentage decreasing at the lower and higher temperatures. © 1989.

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Perennial rye-grass was subjected to two different14C labelling regimes to enable a partitioning of the carbon sources contributing to rhizosphere carbon-flow. Plant/soil microcosms were designed which enabled rye-grass plants to either receive a single pulse of14C-CO2 or to be pre-labelled using a series of14C-CO2 pulses, allowing the fate of newly photoassimilated carbon and carbon lost by root decomposition to be followed into the soil. For young rye-grass plants grown over a short period, rhizosphere carbon flow was found to be dominated by newly photoassimilated carbon. Evidence for this came from the observed percentage of the total14C budget (i.e. total14C-CO2 fixed by the plants) lost from the root/soil system, which was 30 times greater for the pulse labelled compared to pre-labelled plants. Root decomposition was found to be less at 10°C compared to 20-25°C, though input of14C into the soil was the same at both temperatures. © 1988 Kluwer Academic Publishers.

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This article seeks to consider evidence of post-feminist and "post-equality" gender narratives contained in the discourses of law in the UK and European contexts. Analysis of perennial ghosts of gender in the areas of gender-neutrality in policy, legislative regulation of sexual crimes, and the adjudication of gendered issues by judges will be undertaken in order to renew and reinstate the focus of the legal feminist project and advocate for continued scrutiny in these three practical areas.