51 resultados para forest plantations
Resumo:
This paper examines the degree to which tree-associated Coleoptera (beetles) and pollen could be used to predict the degree of ‘openness’ in woodland. The results from two modern insect and pollen analogue studies from ponds at Dunham Massey, Cheshire and Epping Forest, Greater London are presented. We explore the reliability of modern pollen rain and sub-fossil beetle assemblages to represent varying degrees of canopy cover for up to 1000m from a sampling site. Modern woodland canopy structure around the study sites has been assessed using GIS-based mapping at increasing radial distances as an independent check on the modern insect and pollen data sets. These preliminary results suggest that it is possible to use tree-associated Coleoptera to assess the degree of local vegetation openness. Additionally, it appears that insect remains may indicate the relative intensity of land use by grazing animals. Our results also suggest most insects are collected from within a 100m to 200m radius of the sampling site. The pollen results suggest that local vegetation and density of woodland in the immediate area of the sampling site can have a strong role in determining the pollen signal.
Resumo:
The discovery that the hypotensive sequela of envenomation by the South American viper, Bothrops jararaca, was mediated by peptides, represented a milestone in drug discovery research that led to the introduction of ACE inhibitors. These bradykinin-potentiating peptides (BPPs) have been found in the venoms of many species of viper and molecular cloning of biosynthetic precursors has revealed that each encodes several different BPPs in tandem with a single copy of a C-type natriuretic peptide (CNP) located at the C-terminus. Venoms of the African forest vipers (Atheris) have been poorly studied possibly because they do not represent a major danger to humans. However, initial studies have indicated that they contain some of the “classical” protein toxins of viper venoms and a novel class of peptide, the polyglycine/polyhistidine (pGpH) peptides. These peptides occur in several molecular forms with different numbers of repetitive glycine and histidine repeats. We have cloned the biosynthetic precursor of A. squamigera pGpH peptides from a venom-derived cDNA library and have confirmed that a single copy of CNP is located at the C-terminus and additionally that, like BPPs in other vipers, pGpH peptides are encoded in tandem within this single precursor. Solid phase peptide synthesis of pGpH peptides has proven to be extremely difficult but is progressing and acquisition of synthetic replicates of each peptide is a necessary prerequisite for systematic pharmacological characterisation as establishment of a biological function for these peptides remains elusive. pGpH peptides may prove to play a role as fundamental as that of the BPPs.
Resumo:
Madagascar has lost about half of its forest cover since 1953 with much regional variation, for instance most of the coastal lowland forests have been cleared. We sampled the endemic forest dwelling Helictopleurini dung beetles across Madagascar during 2002–2006. Our samples include 29 of the 51 previously known species for which locality information is available. The most significant factor explaining apparent extinctions (species not collected by us) is forest loss within the historical range of the focal species, suggesting that deforestation has already caused the extinction, or effective extinction, of a large number of insect species with small geographical ranges, typical for many endemic taxa in Madagascar. Currently, roughly 10% of the original forest cover remains. Species–area considerations suggest that this will allow roughly half of the species to persist. Our results are consistent with this prediction.
Resumo:
An increase in edge area reduces the effective size of habitat fragments and thus the area available for habitat-interior specialists. However, it is unclear how edge effects compare at different ecotones in the same system. We investigated the response of a small mammal community associated with Afromontane forests to edge effects at three different habitat transitions: natural forest to grassland (natural edge, structurally different vegetation types), natural forest to mature plantation (human-altered edge, structurally similar vegetation types) and natural forest to harvested plantation (human-altered edge, structurally different vegetation types). We predicted that edge effects should be less severe at natural ecotones and at similarly structured contiguous vegetation types than human-altered ecotones and differently structured contiguous vegetation types, respectively. We found that forest species seemed to avoid all habitat edges in our study area. Surprisingly, natural edges supported a less diverse small mammal community than human-altered forest edges. However, edge effects were observed deeper into native forests surrounded by mature alien plantations (and more so at harvested plantations) than into native forests surrounded by native grasslands. The net effect of mature plantations was therefore to reduce the functional size of the natural forest by creating a larger edge. We suggest that when plantations are established a buffer zone of natural vegetation be left between natural forests and newly established plantations to mitigate the negative effects of plantation forestry.
Resumo:
In this study we show that forest areas contribute significantly to the estimated benefits from om outdoor recreation in Northern Ireland. Secondly we provide empirical evidence of the gains in the statistical efficiency of both benefit and parameter estimates obtained by analysing follow-up responses with Double Bounded interval data analysis. As these gains are considerable, it is clearly worth considering this method in CVM survey design even when moderately large sample sizes are used. Finally we demonstrate that estimates of means and medians of WTP distributions for access to forest recreation show plausible magnitude, are consistent with previous UK studies, and converge across parametric and non-parametic methods of estimation.
Resumo:
Ethel Smyth’s opera, Der Wald, met with mixed reactions at its premiere in Berlin in 1902. Many factors contributed to this, not least, as Smyth herself observed, anti-British sentiment in Germany following the second Boer War. One might have expected that the reception of the opera at its British premiere on 18 July at Covent Garden might have been more positive, but even here critical opinion was divided. Even positive reviews were not free from gender discrimination, and other reviews condemned the opera for being too German or Wagnerian. What was meant by ‘Wagnerian’? This article answers the question in three ways. Firstly, I argue that ‘Wagnerian’ meant not a leitmotif-filled, through-composed work (as distinct from a number opera), but simply a lyrical drama; for British audiences the model for this was Tannhäuser or Lohengrin, not the Ring or Tristan. Secondly, taking this definition on board, I analyse the musical language of the opera, in particular the key structure. The central duet sung by the doomed lovers, Heinrich and Röschen, is in F major, almost the furthest possible distance from the home key of the opera (E major), which characterizes the forest and ‘nature’ in general; by contrast, the next scene, where the Kundry-like Iolanthe attempts to seduce Heinrich (a crucial reversal of the more conventional power relations of the love duet), sees a return to the home key. Thirdly, I set the hermeneutical implications of this reversal in the context of the decadent movement, with which late nineteenth-century Wagnerism was associated, and which, following the conviction of Oscar Wilde in 1895, was discredited. Der Wald thus failed because of its ‘guilt by association’ with an aesthetic that had fallen into disrepute.
Resumo:
Connectance webs represent the standard data description in food web ecology, but their usefulness is often limited in understanding the patterns and processes within ecosystems. Increasingly, efforts have been made to incorporate additional, biologically meaningful, data into food web descriptions, including the construction of food webs using data describing the body size and abundance of each species. Here, data from a terrestrial forest floor food web, sampled seasonally over a 1-year period, were analysed to investigate (i) how stable the body size abundance and predator prey relationships of an ecosystem are through time and (ii) whether there are system-specific differences in body size abundance and predator prey relationships between ecosystem types.