997 resultados para Forest influences


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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.

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As James Scott’s Seeing Like a State attests, forests played a central role in the rise of the modern state, specifically as test spaces for evolving methods of managing state resources at a distance, and as the location for grand state schemes. Together, such ambitions necessitated both the elimination of local understandings of forest management – to be replaced by centrally controlled scientific precision – and a narrowing of state vision. Forests thus began to be conflated with trees (and their timber) alone. All other aspects of the forest, both human and non-human, were ignored. Through the lens of the 18th and early 19th century New Forest in southern England, this paper examines the impact of government attempts to shift the focus of state forests from being remnant medieval hunting spaces to spaces of income generation through the creation of vast sylvicultural plantations. This state scheme not only reworked the relationship between the metropole and the provinces – something effected through systematic surveys and novel bureaucratic procedures – but also dramatically impacted upon the biophysical and cultural geographies of the forest. By equating forest space with trees alone, the British state failed to legislate for the actions of both local commoners and non-human others in resisting their schemes. Indeed, subsequent oppositions proved not only the tenacity of commoners in protecting their livelihoods but also the destructive power of non-human actants, specifically rabbits and mice. The paper concludes that grand state schemes necessarily fail due to their own internal illogic: the narrowing of state vision creates blind spots in which human and non-human lives assert their own visions.

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Small mammals that inhabit arid and temporally unproductive environments use several methods to conserve energy. Here, we investigate the energetic role of sun basking in striped mice Rhabdomys pumilio from the Succulent Karoo desert in South Africa. We observed mice in front of their nests for 140 h and recorded the time they spent basking during the non-breeding (dry) and the breeding (wet) seasons. We measured temperature changes in model mice to provide an indication of the heat that can be absorbed from the sun. Finally, we measured the oxygen consumption (circle dot O-2) of mice at their basking sites in the field both in the sun and in the shade. This was accomplished using a portable respirometry system with a metabolism chamber, which could be placed in and out of the sun. Observations showed that mice basked more often during the non-breeding than during the breeding season. During the former season, mice spent an average of 11.9 +/- 1.1 min (se) in the morning and 5.5 +/- 0.5 min in the afternoon per day basking. Within the metabolism chamber, circle dot O-2 decreased when the animal was in the sunshine compared with the shade. This effect occurred independent of the ambient temperature (T-a), indicating that a significant amount of radiant energy was absorbed from the sun. Basking may be an alternative to other energy-acquisition behaviours, such as foraging, which might be particularly useful at times when food is scarce.

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The large range of body-mass values of soil organisms provides a tool to assess the ecological organization of soil communities. The goal of this paper is to identify graphical and quantitative indicators of soil community composition and ecosystem functioning, and to illustrate their application to real soil food webs. The relationships between log-transformed mass and abundance of soil organisms in 20 Dutch meadows and heathlands were investigated. Using principles of allometry, maximal use can be made of ecological theory to build and explain food webs. The aggregate contribution of small invertebrates such as nematodes to the entire community is high under low soil phosphorus content and causes shifts in the mass-abundance relationships and in the trophic structures. We show for the first time that the average of the trophic link lengths is a reliable predictor for assessing soil fertility responses. Ordered trophic link pairs suggest a self-organizing structure of food webs according to resource availability and can predict environmental shifts in ecologically meaningful ways.

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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.

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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.

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Huntington disease (HD) is a neurodegenerative disorder caused by the abnormal expansion of CAG repeats in the HD gene on chromosome 4p16.3. Past studies have shown that the size of expanded CAG repeat is inversely associated with age at onset (AO) of HD. It is not known whether the normal Huntington allele size influences the relation between the expanded repeat and AO of HD. Data collected from two independent cohorts were used to test the hypothesis that the unexpanded CAG repeat interacts with the expanded CAG repeat to influence AO of HD. In the New England Huntington Disease Center Without Walls (NEHD) cohort of 221 HD affected persons and in the HD-MAPS cohort of 533 HD affected persons, we found evidence supporting an interaction between the expanded and unexpanded CAG repeat sizes which influences AO of HD (P = 0.08 and 0.07, respectively). The association was statistically significant when both cohorts were combined (P=0.012). The estimated heritability of the AO residual was 0.56 after adjustment for normal and expanded repeats and their interaction. An analysis of tertiles of repeats sizes revealed that the effect of the normal allele is seen among persons with large HD repeat sizes (47-83). These findings suggest that an increase in the size of the normal repeat may mitigate the expression of the disease among HD affected persons with large expanded CAG repeats. (C) 2003 Wiley-Liss, Inc.

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