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Remnant Patches (remnant + patch)

Distribution by Scientific Domains

Life Sciences	100%

Selected Abstracts

Restoration of a Restinga Sandy Coastal Plain in Brazil: Survival and Growth of Planted Woody Species

RESTORATION ECOLOGY, Issue 1 2006
Luiz R. Zamith
Abstract In this article we report the results of an experiment introducing 17 native shrub and tree species into a Brazilian restinga (i.e., coastal sandy plain vegetation). Restingas have been affected by human impact for about 8,000 years, and human occupation for housing, tourism, and land speculation has recently increased in such a way that there is a need for conservation of remnant patches and restoration of degraded areas throughout the coast to protect biodiversity. Our study site is a remnant located in Rio de Janeiro, the second largest city in the country, and has been subjected in the past to deforestation, man-made fire, and sand extraction. Although trees and shrubs predominantly compose natural restinga vegetation, local vegetation after impact was replaced by an exotic grass cover, which meant a drastic reduction in species richness. Thus, in this experiment we removed the grass cover, introduced shrub and tree species, and monitored survival and growth of 20 plants per species for 2 years. Despite the adversities imposed by the nutrient-poor sandy soil, 70% of the species showed high survival percentage and considerable growth. This report on restoration initiatives in the restingas points out the viability of shrub and tree plantation following exotic grass removal as a strategy to restore Brazilian coastal vegetation. [source]

Impacts of Restored Patch Density and Distance from Natural Forests on Colonization Success

RESTORATION ECOLOGY, Issue 4 2003
Hans Jacquemyn
Abstract The reduction and fragmentation of forest habitats is expected to have profound effects on plant species diversity as a consequence of the decreased area and increased isolation of the remnant patches. To stop the ongoing process of forest fragmentation, much attention has been given recently to the restoration of forest habitat. The present study investigates restoration possibilities of recently established patches with respect to their geographical isolation. Because seed dispersal events over 100 m are considered to be of long distance, a threshold value of 100 m between recent and old woodland was chosen to define isolation. Total species richness, individual patch species richness, frequency distributions in species occurrences, and patch occupancy patterns of individual species were significantly different among isolated and nonisolated stands. In the short term no high species richness is to be expected in isolated stands. Establishing new forests adjacent to existing woodland ensures higher survival probabilities of existing populations. In the long term, however, the importance of long-distance seed dispersal should not be underestimated because most species showed occasional long-distance seed dispersal. A clear distinction should be made between populations colonizing adjacent patches and patches isolated from old woodland. The colonization of isolated stands may have important effects on the dynamics and diversity of forest networks, and more attention should be directed toward the genetic traits and viability of founding populations in isolated stands. [source]

Landscape structure influences tree density patterns in fragmented woodlands in semi-arid eastern Australia

AUSTRAL ECOLOGY, Issue 6 2009
VALERIE J. DEBUSE
Abstract Landscape and local-scale influences are important drivers of plant community structure. However, their relative contribution and the degree to which they interact remain unclear. We quantified the extent to which landscape structure, within-patch habitat and their confounding effects determine post-clearing tree densities and composition in agricultural landscapes in eastern subtropical Australia. Landscape structure (incorporating habitat fragmentation and loss) and within-patch (site) features were quantified for 60 remnant patches of Eucalyptus populnea (Myrtaceae) woodland. Tree density and species for three ecological maturity classes (regeneration, early maturity, late maturity) and local site features were assessed in one 100 × 10 m plot per patch. All but one landscape characteristic was determined within a 1.3-km radius of plots; Euclidean nearest neighbour distance was measured inside a 5-km radius. Variation in tree density and composition for each maturity class was partitioned into independent landscape, independent site and joint effects of landscape and site features using redundancy analysis. Independent site effects explained more variation in regeneration density and composition than pure landscape effects; significant predictors were the proportion of early and late maturity trees at a site, rainfall and the associated interaction. Conversely, landscape structure explained greater variation in early and late maturity tree density and composition than site predictors. Area of remnant native vegetation within a landscape and patch characteristics (area, shape, edge contrast) were significant predictors of early maturity tree density. However, 31% of the explained variation in early mature tree differences represented confounding influences of landscape and local variables. We suggest that within-patch characteristics are important in influencing semi-arid woodland tree regeneration. However, independent and confounding effects of landscape structure resulting from previous vegetation clearing may have exerted a greater historical influence on older cohorts and should be accounted for when examining woodland dynamics across a broader range of environments. [source]

The Role of Cloud Combing and Shading by Isolated Trees in the Succession from Maquis to Rain Forest in New Caledonia1

BIOTROPICA, Issue 2 2002
L. S. Rigg
ABSTRACT This study examined the role of shading and cloud combing of moisture by scattered trees of the emergent conifer Araucaria laubenfelsii (Corbass.) in montane shrubland-maquis at Mont Do, New Caledonia, in facilitating the succession from shrubland to rain forest. Water collection experiments showed that these trees combed significant amounts of water from low clouds on days when no rainfall was recorded and deposited this moisture on the ground beneath the tree canopy. Analysis of photosystem II function in A. laubenfelsii and five other plant species using fluorometry revealed much lower photosystem stress in plants beneath scattered A. laubenfelsii than for individuals exposed to full sunlight in the open maquis. Transition matrix analyses of vegetation change based on "the most likely recruit to succeed" indicated that the transition from maquis to forest was markedly faster when emergent trees of A. laubenfelsii acted as nuclei for forest species invasion of die maquis. On the basis of these lines of evidence, it is argued that increased moisture and shading supplied to the area directly below the crown of isolated A. laubenfelsii trees in the maquis facilitates the establishment of both conifer seedlings and other rain forest tree and shrub species. In the absence of fire, rain forest can reestablish through spread in two ways: first, by expansion from remnant patches, and second, from coalescence of small rain forest patches formed around individual trees of A. laubenfelsii. [source]

Response of Dung Beetle Diversity to Human,induced Changes in a Tropical Landscape,

BIOTROPICA, Issue 1 2002
Gonzalo Halffter
ABSTRACT This paper examines dung beetle communities in remnant patches of tropical deciduous forest at Veracruz, Mexico, as a case study of the effects of tropical deforestation on biodiversity. The two study areas have a common biogeographic history and similar macroclimatic conditions and have been modified by human activities to different extents. The main difference between them is that cattle, which provide the dung beetle's food supply, are present in only one of the areas. Comparison of the dung beetle faunas sheds light on the relative importance of forest cover versus food supply as the principal factor determining the structure and diversity of the fauna. This comparison, which we broaden through an examination of data from other localities in central Veracruz, permits us to speculate about what happens to biodiversity when a tropical deciduous forest undergoes modification of varying type and intensity. Where tree cover has been most modified, native forest species undergo local extinction and are replaced by open area species. On the whole, there has not been a net reduction in species richness (gamma diversity) in the fragmented landscape of central Veracruz, although local species richness (alpha diversity) has diminished. RESUMES En este trabajo se presenta una aproximación de lo que ocurre con la biodiversidad estudiada a través de un grupo indicador (los escarabajos del estiércol) en dos remanentes de bosque tropical caducifolio del estado de Veracruz, México. Los dos sitios comparten la misma historia biogeografica, condiciones macroclimaticas semejantes, y ser bosques parcialmente modificados por la actividad humana. La diferencia principal está en la oferta de alimento para los Scarabaeinae, porque solamente en uno de los lugares hay ganado vacuno. La comparación de la fauna de Scara-baeinae de los dos lugares nos permite señalar que la cubierta forestal, y no la oferta de alimento, es el principal elemento conformador de la estructura y diversidad del gremio. Esta comparación, ampliada con datos de otros puntos de Veracruz centra nos permite especular lo que ocurre con la biodiversidad (representada por los Scarabaeinae) al modificarse el bosque tropical caducifolio en distintas formas e intensidades. Es relevante la sobrevivencia de las especies propias del bosque a nivel paisaje (diversidad gama), aunque puedan desaparecer en parte a escala puntual. Asi como su reemplazo por especies heliofilas en los puntos en que la vegetación arborea ha sido mas modificada. En conjunto el paisaje fragmentado y diverse de Veracruz centre no señala una pérdida de especies, aunque puntualmente (diversidad alia) si ocurra. [source]