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Core Habitat (core + habitat)

Distribution by Scientific Domains

Life Sciences	60%

Selected Abstracts

Conservation planning and viability: problems associated with identifying priority sites in Swaziland using species list data

AFRICAN JOURNAL OF ECOLOGY, Issue 3 2010
Robert J. Smith
Abstract Conservation planning assessments based on species atlas data are known to select planning units containing ecotones because these areas are relatively species-rich. However, this richness is often dependent on the presence of adjoining core habitat, so populations within these ecotones might not be viable. This suggests that atlas data may also fail to distinguish between planning units that are highly transformed by agriculture or urbanization with those from neighbouring untransformed units. These highly transformed units could also be identified as priority sites, based solely on the presence of species that require adjoining habitat patches to persist. This potential problem was investigated using bird and mammal atlas data from Swaziland and a landcover map and found that: (i) there was no correlation between planning unit species richness and proportion of natural landcover for both taxa; (ii) the priority areas that were identified for both birds and mammals were no less transformed than if the units had been chosen at random and (iii) an approach that aimed to meet conservation targets and minimize transformation levels failed to identify more viable priority areas. This third result probably arose because 4.8% of the bird species and 22% of the mammal species were recorded in only one planning unit, reducing the opportunity to choose between units when aiming to represent each species. Therefore, it is suggested that using species lists to design protected area networks at a fine spatial scale may not conserve species effectively unless population viability data are explicitly included in the analysis. Résumé On sait que les évaluations de planifications de la conservation qui se basent sur les données d'atlas des espèces choisissent des unités de planification qui contiennent des écotones parce que ces zones sont relativement riches en espèces. Cependant, cette richesse dépend souvent de la présence proche d'un habitat principal, de sorte que les populations de ces écotones pourraient en fait ne pas être viables. Cela signifie que les données des atlas pourraient aussi ne pas faire la distinction entre les unités de planification qui sont fortement modifiées par l'agriculture ou l'urbanization et celles, voisines, qui ne sont pas modifiées. Des unités profondément modifiées pourraient aussi être identifiées comme sites prioritaires, si l'on se base seulement sur la présence d'espèces qui ont besoin des îlots d'habitats voisins pour subsister. Ce problème potentiel fut étudié en utilisant les données d'atlas sur des oiseaux et des mammifères du Swaziland et une carte de la couverture du terrain, et on a découvert que (i) il n'y avait pas de corrélation entre la richesse en espèces des unités de planification et la proportion de couverture naturelle pour les deux taxons; (ii) les zones prioritaires qui avaient été identifiées pour les oiseaux et pour les mammifères n'étaient pas moins transformées que si les unités avaient été choisies au hasard et (iii) une approche qui visait à atteindre des cibles de conservation et à minimizer le taux de transformation n'avait pas réussi à identifier les zones prioritaires les plus viables. Ce troisième résultat vient peut-être du fait que 4.8% des espèces d'oiseaux et 22% des espèces de mammifères avaient été rapportés pour une seule unité de planification, ce qui a réduit la possibilité de choisir entre les unités lorsque l'on a cherchéà représenter chaque espèce. C'est pourquoi on attire l'attention sur le fait que l'utilization des listes d'espèces pour concevoir les réseaux d'AP à petite échelle spatiale risque de ne pas préserver efficacement les espèces à moins que les données sur la viabilité de leur population ne soient explicitement incluses dans l'analyzse. [source]

Factors determining the centrifugal organization of remnant Festuca grassland communities in Alberta

JOURNAL OF VEGETATION SCIENCE, Issue 1 2000
K. Vujnovic
Moss (1983); Pavlick & Looman (1984) Abstract. This paper describes the species composition of remnant grasslands in the aspen parkland region of Alberta and its relation to soil characteristics and small-scale disturbance. Our findings are consistent with the centrifugal model of communities with Festuca hallii dominating undisturbed ,core' habitat and the composition of more ,peripheral' habitats varying in soil properties and in the magnitude of disturbance. Invasive non-native species are not present in the core habitat and are present only in the disturbed sites, most abundantly in those with the highest soil nitrogen. The centrifugal model, as it applies to these remnant grasslands, differs from its previous application to wetlands and forests in that the core communities are not on the most fertile sites, but on the least disturbed. These findings have implications for the management of prairie remnants to exclude invasive exotic species. [source]

Forest landscape pattern in the KwaZulu,Natal midlands, South Africa: 50 years of change or stasis?

AUSTRAL ECOLOGY, Issue 6 2004
MICHAEL J. LAWES
Abstract Understanding patterns and processes of habitat change is essential for managing and conserving forest fragments in anthropogenically altered landscapes. Digitized aerial photographs from 1944 and 1996 were examined for changes to the indigenous forest landscape in the Karkloof-Balgowan archipelago in KwaZulu,Natal, South Africa. Attributes relating to proximate land-use, patch shape, isolation and position in the landscape were used to determine putative causes of forest change. The total change in forest area was ,5.7% (forest covered 6739 ha in 1996). This is contrasted with previous reports for the period 1880,1940 that estimated change in total forest area of up to ,80%. Attrition was the predominant process of forest transformation between 1944 and 1996. Despite little overall change in forest area, 786 mostly small (<0.5 ha) forest patches were lost from the landscape, leaving 1277 forest patches in 1996. An increase in patch isolation, but no change in patch cohesion accompanied the changes in forest area. Ignoring patches that were eliminated, 514 patches decreased in area. This was partly a function of patch size, but the conversion of natural grassland to commercial plantation forestry in the matrix also influenced forest decline. Their small size and irregular shape caused forest patches in the region to be vulnerable to edge effects. Core area declined in a negative exponential way with increasing edge width and the total area of edge habitat exceeded that of core habitat at an edge width of only 50 m. Nevertheless, total core area decreased by only 2% (65 ha) between 1944 and 1996 because most of the eliminated patches were small and contained no core area. The large Karkloof forest (1649 ha) is a conservation priority for forest interior species, but the ecological role and biodiversity value of small forest patches should not be overlooked. [source]

Response of ground-dwelling beetles across logging coupe edges into streamside reserves

AUSTRALIAN JOURNAL OF ENTOMOLOGY, Issue 3 2009
Susan C Baker
Abstract Streamside reserves can provide important habitat reservation in forest landscapes subject to logging. Depending on the width of streamside reserves, edge effects have the potential to compromise their effectiveness for terrestrial conservation, yet edge effects into riparian environments have rarely been assessed. It would be unwise to assume that edge effects act in the same way at streamside reserves as at the non-riparian edges of logging coupes, as interactions with riparian influences on beetles along the stream-upslope gradient might create unique edge conditions. In this study, we assess edge effects on ground dwelling beetles at four sites, using transects of pitfall traps across logging coupe edges into streamside reserves that have only been affected by logging on one side of the stream. Edge effects were found to extend further into streamside reserves in this study than into upslope habitat at the same sites from a concurrent study. Edge effects were site specific and appeared to extend as far as the stream in most cases (23,65 m). Comparison of beetle assemblage composition with adjacent unlogged streams supported the conclusion that beetles within 10 m of streams in streamside reserves were still responding to edge effects. These results suggest that streamside reserves might not contain habitat comparable with riparian areas away from the influences of nearby clearfelling, and wider reserves are recommended to maintain core habitat not compromised by edge effects. [source]