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Undisturbed Areas (undisturbed + area)

Distribution by Scientific Domains
Life Sciences100%

Selected Abstracts

Physiological and Behavioral Differences in Magellanic Penguin Chicks in Undisturbed and Tourist-Visited Locations of a Colony

CONSERVATION BIOLOGY, Issue 5 2005
BRIAN G. WALKER
corticoesterona; ecoturismo; perturbación humana; Spheniscus magellanicus Abstract:,Studies examining anthropogenic effects on wildlife typically focus on adults and on behavioral responses rather than the physiological consequences of human disturbances. Here we examined how Magellanic Penguin ( Spheniscus magellanicus) chicks living in either tourist-visited or undisturbed areas of a breeding colony were affected by human visitation by comparing the baseline and stress-induced levels of corticosterone during three periods of the breeding season. Newly hatched chicks in visited areas had higher corticosterone stress responses than newly hatched chicks in undisturbed areas (p =0.007), but baseline levels were similar (p =0.61). By 40,50 days of age and around fledging time, both visited and undisturbed chicks showed a robust corticosterone stress response to capture. Tourist-visited chicks did not flee when approached by humans, however, whereas undisturbed chicks fled significantly sooner (i.e., when approached no closer than 9 m; p < 0.0001). Although it is unknown whether Magellanic Penguin chicks raised in visited areas suffer negative consequences from the elevation of the corticosterone stress response at hatching, they do exhibit behavioral habituation to human contact by the time they are ready to fledge. Unlike adults living in tourist areas, however, fledging chicks in visited areas do not have a decreased stress response to capture and restraint. Our results show that the coupling of behavioral and physiological habituation in Magellanic Penguins is complex and life-history context may greatly affect the ability of wildlife to adapt to anthropogenic disturbances. Resumen:,Los estudios de los efectos antropogénicos sobre la vida silvestre se centran típicamente en adultos y en las respuestas conductuales en lugar de las consecuencias fisiológicas de las perturbaciones humanas. Aquí examinamos el efecto de la visita de humanos sobre pollos de pingüino (Spheniscus magellanicus) en áreas visitadas por turistas o no perturbadas mediante la comparación de los niveles, base e inducidos por estrés, de corticoesterona durante tres períodos de la temporada reproductiva. Los pollos recién eclosionados en áreas visitadas tuvieron mayor respuesta de la corticoesterona al estrés que los pollos recién eclosionados en áreas no perturbadas (p =0.007), pero los niveles básicos fueron similares (p =0.61). A los 40,50 días y en la etapa de volantón, los pollos visitados y no perturbados mostraron una marcada respuesta de la corticoesterona al estrés al ser capturados. Sin embargo, los pollos visitados por turistas no huyeron cuando se les acercaron humanos, mientras que los pollos no perturbados huyeron significativamente antes (i.e., acercamiento a más de 9 m; p < 0.0001). Aunque se desconoce si los pollos de pingüino criados en áreas visitadas sufren consecuencias negativas por la elevación de la corticosterona en respuesta al estrés al eclosionar, si presentan acostumbramiento conductual al contacto con humanos al momento que están listos para dejar el nido. Sin embargo, a diferencia de adultos que viven en áreas turísticas, los pollos volantones en las áreas visitadas no tienen una disminución en la respuesta al estrés cuando son capturados y sujetados. Nuestros resultados muestran la complejidad de la combinación del acostumbramiento conductual y fisiológico en Spheniscus magellanicus y que el contexto de la historia de vida puede afectar a la habilidad de la vida silvestre para adaptarse a las perturbaciones antropogénicas. [source]

Recolonisation of natural landslides in tropical mountain forests of Southern Ecuador

FEDDES REPERTORIUM, Issue 3-4 2004
(corresp. author) C. Ohl Dr.
The regeneration of the vegetation of natural landslides was studied at Estación Científica San Francisco (ECSF) in a tropical mountain forest area of Southern Ecuador, north of Podocarpus National Park. The study focused on the process of regeneration on natural landslides and the vegetation change along an altitudinal gradient using space-for-time substitution. The most important plant families present on the landslides during the first stages of succession are Gleicheniaceae (Pteridophyta), Melastomataceae, Ericaceae and Orchidaceae. Species of the genus Sticherus (Gleicheniaceae) are dominant, and species composition varies with altitude and soil conditions. Colonisation of landslides is not homogeneous. Zones with bare ground, sparsely vegetated patches and densely covered areas may be present within the same slide. This small scale spatial heterogeneity is often created by local ongoing sliding processes and different distances towards undisturbed areas. Therefore, the duration of the successional process is highly variable. The initial stage of the succession is a community of non vascular plants interspersed with scattered individuals of vascular plants. By means of runner-shoots they form vegetation patches which start growing into each other. The second stage is dominated by Gleicheniaceae (species composition varying in altitude and soil chemistry). In the third stage, bushes and trees colonise, sheltered by the ferns, and a secondary forest develops with pioneer species that are not found in the primary forest vegetation. The common phenomenon of the natural landslides leads to an increase in structural and species diversity on a regional scale. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) Rekolonisation auf natürlichen Hangrutschungen in tropischen Bergwäldern Südecuadors Im tropischen Bergwald Südecuadors (nördlich des Podocarpus Nationalparks im Gebiet der Estación Científica San Francisco, ECSF) wurden Artenzusammensetzung und Rekolonisationsprozesse früher Sukzessionsstadien entlang eines Höhengradienten auf natürlichen Hangrutschungen untersucht. Besonders Gleicheniaceae, Melastomataceae, Ericaceae und Orchidaceae sind von Bedeutung. Arten der Gattung Sticherus (Gleicheniaceae) sind sehr zahlreich vertreten. Die Artenzusammensetzung wechselt entlang des Höhengradienten und in Abhängigkeit von den Bodenbedingungen. Die mosaikartige Verteilung der Vegetation auf den Rutschungen (gänzlich unbedeckte bis stark überwucherte Zonen) ist auf häufige lokale Nachrutschungen sowie auf unterschiedliche Geschwindigkeiten der Wiederbesiedlung entsprechend der Distanz zu ungestörter Vegetation zurückzuführen. Die Dauer der Sukzession ist daher sehr variabel. Das Initialstadium wird von Moosen und Flechten gebildet. Im weiteren Verlauf führt die überwiegend vegetative Ausbreitung einzelner Gefäßpflanzen zum zweiten Sukzessionsstadium. Dieses ist durch die Dominanz von Gleicheniaceae gekennzeichnet, während im dritten Stadium im Schutze der Farne erste Büsche und Bäume heranwachsen und den Pionierwald bilden. Da diese Arten nicht im Primärwald vertreten sind, kommt es regional zu einer beträchtlichen Erhöhung der Artenzahl und der strukturellen Diversität. [source]

Impact of land use on the ecology of uncultivated plant species in the Rwenzori mountain range, mid western Uganda

AFRICAN JOURNAL OF ECOLOGY, Issue 4 2009
Moses Muhumuza
Abstract Rwenzori mountain range is important for its high diversity of unique species and as a water catchment area and yet very fragile to human interference. The study documented the impact of land use on ecology of uncultivated plant species in the Rwenzori mountain range using Bugoye sub-county as a reference site. The ecological aspects of the plants studied included distribution, abundance and diversity of the plant species in and around the various land uses as well as in degraded, disturbed and undisturbed areas. Land uses identified were; agriculture, built up area and land with other activities (conservation and abandoned fields). The study revealed that agriculture was the main land use category taking up 69.7% of land use area. Plants distributed in and around the land uses were mainly trees with species diversity of 34.5%. Generally, there was no relationship in the distribution of plant species in degraded, undisturbed and disturbed areas (a = 0.01). In disturbed areas, there was vegetation cover especially of plant species that occur as secondary re-growth, and in degraded areas, the ground was sparsely covered by primary succession species while in the undisturbed areas, plant species growing in a ,natural. habitat dominated and most of them were climax species. Résumé Le Massif de Ruwenzori est important pour sa grande diversité d'espèces uniques et comme zone de captage d'eau, et il est pourtant très sensible à toute interférence humaine. L'étude a documenté l'impact de l'utilisation du sol sur l'écologie d'espèces de plantes sauvages dans le massif du Ruwenzori, en employant le sous-comté de Bugoye comme site de référence. Les aspects écologiques des plantes étudiées incluaient la distribution, l'abondance et la diversité des espèces végétales dans et autour de sites avec diverses utilisations du sol ainsi que dans des zones dégradées, perturbées et non perturbées. Les utilisations de sol identifiées étaient : agriculture, zone construite et terrain avec autres activités (conservation et champs abandonnés). L'étude a révélé que l'agriculture était la principale catégorie d'utilisation de sol, avec 69,7% de la superficie utilisée. Les plantes réparties dans et autour des sols utilisés étaient principalement des arbres, avec une diversité d'espèces de 34.5%. Généralement, il n'y avait aucune relation dans la distribution des espèces végétales dans les zones dégradées, non perturbées et perturbées (a = 0.01). Dans les zones perturbées, il y avait une couverture végétale composée principalement d'espèces qui se rencontrent comme repousses secondaires, et dans les zones dégradées, le sol était recouvert, de façon éparse, par des espèces de succession primaire, alors que dans les zones non perturbées, les espèces végétales poussant dans un habitat naturel dominaient, la plupart d'entre elles étant des espèces climaciques. [source]

Using Dominance-Diversity Curves to Assess Completion Criteria After Bauxite Mining Rehabilitation in Western Australia

RESTORATION ECOLOGY, Issue 1 2003
C. D. Grant
Abstract Dominance-diversity curves have been previously constructed for a range of ecosystems around the world to illustrate the dominance of particular species and show how their relative abundances compare between communities separated in time or space. We investigate the usefulness of dominance-diversity curves in rehabilitated areas to compare the floristic composition and abundance of "undisturbed" areas with disturbed areas, using bauxite mining rehabilitation in Western Australia as an example. Rehabilitated pits (11,13 years old) subjected to prescribed fire in autumn and spring were compared with unburned rehabilitated areas and the native jarrah (Eucalyptus marginata) forest. Dominance diversity curves were constructed by ranking the log of the species density values from highest to lowest. Species were categorized according to a variety of functional responses: life form (trees, shrubs, subshrubs, and annuals), fire response syndrome (seeder or resprouter), nitrogen fixing capability, and origin (native or adventive). Exponential functions showed extremely good fits for all sites (r2 = 0.939,0.995). Dominance diversity graphs showed that after burning of rehabilitated areas, sites exhibited a more similar dominance-diversity curve than before burning. This was emphasized in a classification (UPGMA) of the regression equations from the dominance-diversity curves that showed that sites burned in spring were more similar to the native forest than sites burned in autumn. There was no significant segregation of the nitrogen-fixing and species origin categories, although the life form and fire response groupings showed significant segregation along the dominance-diversity curve. Resprouters tended to be over-represented in the lower quartiles and under-represented in the upper quartiles of post-burn sites. It is suggested that using dominance-diversity curves in the monitoring of rehabilitated areas may be a useful approach because it provides an easily interpretable visual representation of both species richness and abundance relationships and may be further utilized to emphasize categories of plants that are over- or under-represented in rehabilitated areas. This will assist in the post-rehabilitation management of these sites. [source]

New method to census primate groups: Estimating group density of Japanese macaques by point census

AMERICAN JOURNAL OF PRIMATOLOGY, Issue 2 2003
Goro Hanya
Abstract We devised a new method to estimate the density of primate groups in habitats that preclude the use of a line-transect census because the ground is too steep. We combined point census and group follows. From the number of groups counted at a fixed point for an hour, n, group density D was calculated: . ,, the detectability constant, was a constant when distance-dependent detectability g(y) was regressed on a half-normal model: g(y) = e -,2 and can be estimated by combining the information of group follow and point census. Using this method, we estimated the group density of Japanese macaques in Yakushima. A census area of 7 km2 was divided into 28 grid squares (500 m×500 m). One observer was positioned at a point in each grid square, and those points were censused simultaneously for 4,6 days from 0600,0700 to 1500,1600 hr. Four troops were followed for 144 hr during the point census. Distance-dependent detectability closely correlated with the half-normal model. The detectability constant varied with the time of day, but it was not influenced by troop identity or topography. Group density was calculated to be 1.48±0.61 and 0.701±0.432 groups/km2 in the disturbed and undisturbed areas, respectively (95% confidence limit). "True" group density estimated by home range data was within the confidence limit calculated by a point census in the home range of the troops for two troops, suggesting that this method was valid. This method is applicable to other species as long as at least one group can be followed, because it satisfies the fundamental assumptions of point census, and the detectability does not seem to be biased by troop or topography. Am. J. Primatol. 60:43,56, 2003. [source]

Population dynamics in Digitalis purpurea: the interaction of disturbance and seed bank dynamics

JOURNAL OF ECOLOGY, Issue 6 2007
NINA SLETVOLD
Summary 1Plant ecologists have long since realized that the persistence of many facultative biennial plants depends upon disturbance. However, we still have a limited knowledge of the population-level effects of disturbance, and the connection between adult and seed bank dynamics. 2Using data from a 3-year demographic study combined with experimental gap-opening in a large population of Digitalis purpurea, we parameterized stochastic transition matrix models in ,disturbed' vs. ,undisturbed' areas. We simulated different gap sizes (fraction of population that was disturbed) and temporal disturbance patterns (constant, random, regular and irregular return intervals) and evaluated the effects on population growth rate and seed bank dynamics. To explore seed bank importance we used two alternatives for seed bank survival rate (0.75/0.35) and three alternatives for seed bank recruitment fraction (0.9/0.5/0.1). 3Observed background recruitment levels were insufficient to ensure a positive population growth rate. Increased amounts of gap-opening led to higher growth rates, and population persistence was predicted at moderate disturbance levels if seed bank survival was high (0.75). 4Temporal disturbance pattern affected model results; random and interval scenarios resulted in lower population growth rates and higher extinction risks than constant scenarios of the same average disturbance level. Small and frequent disturbances led to considerably higher growth rates than large and rare disturbances. 5Stochastic elasticity analyses identified the seed bank as the most important life cycle stage with respect to population growth and persistence in most scenarios, and its relative impact was positively related to seed bank survival rate and negatively related to disturbance level. Variation in the recruitment fraction from seed bank vs. seed rain affected both population growth rate and elasticity patterns, indicating the large impact of spatial variation in seed bank density. 6Synthesis: Despite the existence of a large seed bank, our data suggest that recruitment may be locally seed-limited due to a patchy seed bank structure. Local population development may consequently differ widely from gap to gap. These results illustrate how spatial structures in both seed bank, adult population and gap formation interact to shape plant population dynamics, as well as the occurrence of microsite- vs. seed-limitation. [source]