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Natural Landscapes (natural + landscapes)
Selected AbstractsRestoring landscapes: the authenticity problemEARTH SURFACE PROCESSES AND LANDFORMS, Issue 13 2006Isis Brook Abstract Philosophical concerns about restoring landscapes often revolve around two, connected, issues. First is the idea that a restored landscape, even if it is a perfect replica, has lost some of its value. The claim might appeal to a break in the continuity of the landscape and that continuity is part of what is valuable. Alternatively, often in the case of natural landscapes, the appeal is that any human manipulation is inauthentic; here the analogy is sometimes made with the art world and the restoration is deemed a fake. The second problem highlighted in philosophical debates is that the greater the success of restoration projects, the more threatened natural landscapes become: any claim that something must be preserved in its pristine or historically layered state is undermined by the claim that it could be put back again. Initially I discuss two opposing potential responses to these claims: (1) that humans are part of nature and thus cannot be an alien dominating force outside of nature; and (2) that nature is itself a social construct. Neither of these positions is entirely satisfactory, but what they jointly reveal is the reality of our fluid and multifaceted relationship with the world. I then show that Elliot's claim of the additional value of pristine nature is actually not based on an inherent value, but is dependent on the human valuation of it. I propose an alternative that places the source of value in the thing itself and thus arrive at a positive role for restoration as the setting in train and guiding of positive relationships above and beyond their social or public amenity value to us. Copyright © 2006 John Wiley & Sons, Ltd. [source] Soil creep and convex-upward velocity profiles: theoretical and experimental investigation of disturbance-driven sediment transport on hillslopesEARTH SURFACE PROCESSES AND LANDFORMS, Issue 13 2004Joshua J. Roering Abstract The movement of unconsolidated materials near the Earth's surface is often driven by disturbances that occur at a range of spatial and temporal scales. The nature of these disturbances ranges from highly variable, such as tree turnover, to periodic and predictable, such as frost heave or creep. To explore the effect of probabilistic disturbances on surface processes, we formulated a granular creep model with analogy to rate process theory (RPT) used for chemical reactions. According to the theory, individual particles must be energized to a height greater than adjacent particles in order for grain dilation and transport to occur. The height of neighbouring particles (which is akin to activation energy in chemical reactions) varies with slope angle such that energy barriers get smaller in the downslope direction as slopes steepen. When slopes approach the friction-limited angle of repose, the height of energy barriers approaches zero and grains ,ow in the absence of disturbance. An exponential function is used to describe the probability distribution of particle excitation height although alternative distributions are possible. We tested model predictions of granular dynamics in an experimental sandpile. In the sandpile, acoustic energy serves as the disturbance agent such that grains dilate and shear in response. Particle velocities are controlled by the frequency of energy pulses that result in grain displacement. Using tracer particles, we observed a convex-upward velocity pro,le near the surface of the sandpile, consistent with predictions of our RPT-based velocity model. In addition, we depth-integrated the velocity model to predict how ,ux rates vary with inclination of the sandpile and observed non-linear ,ux,gradient curves consistent with model predictions. By varying the acoustic energy level in the experimental sandpile, we documented changes in the rate of grain movement; similar changes in modelled velocities were achieved by varying the exponent of the particle excitation probability distribution. The general agreement between observed and modelled granular behaviour in our simple laboratory sandpile supports the utility of RPT-based methods for modelling transport processes (e.g. soil creep, frost heave, and till deformation), thus enabling us to account for the probabilistic nature of disturbances that liberate sediment in natural landscapes. Copyright © 2004 John Wiley & Sons, Ltd. [source] Predator control of ecosystem nutrient dynamicsECOLOGY LETTERS, Issue 10 2010Oswald J. Schmitz Abstract Predators are predominantly valued for their ability to control prey, as indicators of high levels of biodiversity and as tourism attractions. This view, however, is incomplete because it does not acknowledge that predators may play a significant role in the delivery of critical life-support services such as ecosystem nutrient cycling. New research is beginning to show that predator effects on nutrient cycling are ubiquitous. These effects emerge from direct nutrient excretion, egestion or translocation within and across ecosystem boundaries after prey consumption, and from indirect effects mediated by predator interactions with prey. Depending on their behavioural ecology, predators can create heterogeneous or homogeneous nutrient distributions across natural landscapes. Because predator species are disproportionately vulnerable to elimination from ecosystems, we stand to lose much more from their disappearance than their simple charismatic attractiveness. [source] Diffusion models for animals in complex landscapes: incorporating heterogeneity among substrates, individuals and edge behavioursJOURNAL OF ANIMAL ECOLOGY, Issue 5 2008John D. Reeve Summary 1Animals move commonly through a variety of landscape elements and edges in search of food, mates and other resources. We developed a diffusion model for the movement of an insect herbivore, the planthopper Prokelisia crocea, that inhabits a landscape composed of patches of its host plant, prairie cordgrass Spartina pectinata, embedded in a matrix of mudflat or smooth brome Bromus inermis. 2We used mark,release,resight experiments to quantify planthopper movements within cordgrass,brome and cordgrass,mudflat arenas. A diffusion model was then fitted that included varying diffusion rates for cordgrass and matrix, edge behaviour in the form of a biased random walk and heterogeneity among planthoppers (sessile vs. mobile). The model parameters were estimated by maximum likelihood using the numerical solution of the diffusion model as a probability density. Akaike's information criterion (AIC) values were used to compare models with different subsets of features. 3There was clear support for models incorporating edge behaviour and both sessile and mobile insects. The most striking difference between the cordgrass,brome and cordgrass,mudflat experiments involved edge behaviour. Planthoppers crossed the cordgrass,brome edge readily in either direction, but traversed the cordgrass,mudflat edge primarily in one direction (mudflat to cordgrass). Diffusion rates were also significantly higher on mudflat than for cordgrass and brome. 4The differences in behaviour for cordgrass,brome vs. cordgrass,mudflat edges have implications for the connectivity of cordgrass patches as well as their persistence. Higher dispersal rates are expected between cordgrass patches separated by brome relative to mudflat, but patches surrounded by mudflat appear more likely to persist through time. 5The experimental design and diffusion models used here could potentially be extended to any organism where mass mark,recapture experiments are feasible, as well as complex natural landscapes. [source] Birth size and postnatal growth in cave- and bridge-roosting Brazilian free-tailed batsJOURNAL OF ZOOLOGY, Issue 1 2010L. C. Allen Abstract As the human population continues to expand, increased encroachment on natural landscapes and wildlife habitats is expected. Organisms able to acclimate to human-altered environments should have a selective advantage over those unable to do so. Over the past two decades, bats have increasingly begun to roost and raise offspring in spaces beneath pre-cast concrete bridges. Few studies have examined the health or fitness of individuals living in these anthropogenic sites. In the present study, we examined birth size and postnatal growth, as surrogates of reproductive success, in Brazilian free-tailed bat pups born at a natural and a human-made roost. Based on putative stress-related conditions (noise from vehicular traffic, chemical pollutants and a modified social environment) present at bridges, we predicted that bats at these sites would have reduced reproductive success. Contrary to our prediction, pups born at a bridge site were on average heavier and larger at birth and grew faster than those born at a cave site. Also, both birth size and growth rates of pups differ between years. We attribute observed differences to a combination of roost-related conditions (i.e. roost temperature and proximity to foraging areas), climate and maternal effects with larger mothers raising larger pups. Thus, some bridge roosts, at least in the short term, are suitable, and in some cases may provide better conditions, for raising young bat pups than cave roosts. [source] Microsatellite DNA markers for three toad-headed lizard species (Phrynocephalus vlangalii, P. przewalskii and P. guttatus)MOLECULAR ECOLOGY RESOURCES, Issue 2 2009AIBIN ZHAN Abstract To assess the impact of natural landscapes on the population structure of lizards, 10 polymorphic microsatellite DNA markers were developed for the Qinghai toad-headed lizard, Phrynocephalus vlangalii. The number of alleles at these informative loci ranged from four to 28. The novel markers and those previously developed for Phrynocephalus przewalskii were cross-tested among three toad-headed lizard species P. vlangalii, P. przewalskii and P. guttatus. A high cross-utility rate of more than 58% was observed among these three species. These markers are expected to be useful tools for taxonomic considerations as well as population genetic analysis and future conservation management. [source] Spatial analysis of the coincidence of rare vascular plants and landforms in the Carolinian zone of Canada: implications for protectionTHE CANADIAN GEOGRAPHER/LE GEOGRAPHE CANADIEN, Issue 3 2002BRIAN KLINKENBERG Assessing biodiversity in natural landscapes continues to be a focus of attention. While some researchers assess the value of predictive features, such as land-form, others examine concentrations of rare species, seeking insight into their significance. In this paper I examine two inter-related concepts. I explore the distributions of rare species on the landscape, assessing correlations between landform, numbers of rare species, and protected areas. I also examine the role of protected sites in maintaining biodiversity. Using records of rare plant collections for the south-western portion of Ontario (the Carolinian zone) that were compiled as part of the Atlas of Rare Vascular Plants of Ontario project, and combining these with a) a map of the landforms of south-western Ontario and b) the locations of protected areas within this region, an analysis was made of the spatial coincidence of rare vascular plants, landforms and protected areas. The findings here indicate that protected areas are critically aligned with the distribution of rare vascular plant species. While protected areas occupy less than 2 percent of the study region, approximately 20 percent of the 4379 unique rare plant records analyzed (representing 170 of the 293 rare species in the database or 68%) were collected from a protected site. In addition, while 42 percent of the rare vascular plant records occur on a single landform type, sand plains, sand plains occupy only 18 percent of the region. And while 24 percent of the study region is composed of till plains, less than 2 percent of the rare plant collections were found on this landform. Significantly, four land-forms, representing 50 percent of the study region, support over 80 percent of all rare plant collections. L'évaluation de biodiversité dans les paysages naturels continue d'être un point de mire. Pendant que certains chercheurs estiment la valeur des caracteristiques prédictives, telles que des formes de relief, d'autres examinent les concentrations d'espèces rares pour comprendre leur signification. Dans cet exposé, j'examine deux concepts intereliés. J'explore les distributions d'espèces rares dans le paysage, évaluant les corrélations entre les formes de relief, les nombres d'espèces rares, et les sites protégés. J'examine aussi le rôle des sites protégés dans la conservation de biodiversité. La coïncidence spatiale des plantes vasculaires rares, formes de relief, et sites protégés a été analysée. L'analyse utilise, en partie, l'inventaire de collections de plantes rares pour une région dans le sud-ouest de l'Ontario. Cet inventaire a été compilé pour le projet Atlas of Rare Vascular Plants of Ontario. L'analyse totale combine cet inventaire avec (a) une carte des formes de relief dans le sud-ouest de l'Ontario et (b) les emplacements des sites protégés dans la même région. Les resultats indiquent que les sites protégés sont fortement alignés avec la distribution d'espèces rares. Alors que les sites protégés occupent mains que 2 pour cent de la region étudiée, environ 20 pour cent des 4379 plantes rares uniques analysées (représentant 7 70 des 293 espèces rares dans la banque de données ou 68%) se trouvent sur des sites protégés. De plus, alors que 42 pour cent des plantes rares se retrouvent sur un seul type de forme de relief (plaine de sable), ce type occupe seulement 18 pour cent de la région. Et alors que les plaines constituent 24 pour cent de la région, mains que 2 pour cent des plantes rares se retrouvent sur celles-ci. Fait révélateur, quatre formes de relief constituent 50 pour cent la région étudiée mais elles soutiennent plus que 80 pour cent des plantes rares. [source] Factors for the presence of avian scavengers in Accra and Kumasi, GhanaAREA, Issue 3 2009Michael Campbell Avian scavengers are common and active in the social life of southern Ghana, yet few studies consider both the ecological factors for avian presence and the avian,human interactions from human gender and age perspectives, and compare avian behaviour in both human-dominated and natural landscapes. This paper examines interactions between people, hooded vultures and pied crows in Accra and Kumasi, Ghana using both ecological and social research methods. Land use was classified for species presence into meat and waste production, vegetable marketing, non-food production, residential and central business areas, green spaces and rural areas. One hundred and eighty-four people were interviewed, classified according to age and gender. Hooded vultures and pied crows were more common in urban than rural areas, and their presence was positively correlated with human numbers. Birds were most common in meat and waste production areas, but also foraged for street discards in non-food production and residential areas, and were most rare in rural areas. Bird consumption of waste was viewed positively, while eating of other foods, close proximity and unusual behaviours were viewed negatively. Both species, especially the larger vultures, were feared as spiritual agents, this measured by odd behaviours. Women and older people had stronger beliefs, due to cultural conditioning. These human perspectives and reactions influenced avian presence. This study contributes to urban avian ecology, socio-cultural studies and urban planning. [source] | |||||||||||||