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Large Trees (large + tree)
Selected AbstractsSpatial population structure of a specialist leaf-mining mothJOURNAL OF ANIMAL ECOLOGY, Issue 4 2008Sofia Gripenberg Summary 1The spatial structure of natural populations may profoundly influence their dynamics. Depending on the frequency of movements among local populations and the consequent balance between local and regional population processes, earlier work has attempted to classify metapopulations into clear-cut categories, ranging from patchy populations to sets of remnant populations. In an alternative, dichotomous scheme, local populations have been classified as self-sustaining populations generating a surplus of individuals (sources) and those depending on immigration for persistence (sinks). 2In this paper, we describe the spatial population structure of the leaf-mining moth Tischeria ekebladella, a specialist herbivore of the pedunculate oak Quercus robur. We relate moth dispersal to the distribution of oaks on Wattkast, a small island (5 km2) off the south-western coast of Finland. 3We build a spatially realistic metapopulation model derived from assumptions concerning the behaviour of individual moths, and show that the model is able to explain part of the variation in observed patterns of occurrence and colonization. 4While the species was always present on large trees, a considerable proportion of the local populations associated with small oaks showed extinction,recolonization dynamics. The vast majority of moth individuals occur on large trees. 5According to model predictions, the dominance of local vs. regional processes in tree-specific moth dynamics varies drastically across the landscape. Most local populations may be defined broadly as ,sinks', as model simulations suggest that in the absence of immigration, only the largest oaks will sustain viable moth populations. Large trees in areas of high oak density will contribute most to the overall persistence of the metapopulation by acting as sources of moths colonizing other trees. 6No single ,metapopulation type' will suffice to describe the oak,moth system. Instead, our study supports the notion that real populations are often a mix of earlier identified categories. The level to which local populations may persist after landscape modification will vary across the landscape, and sweeping classifications of metapopulations into single categories will contribute little to understanding how individual local populations contribute to the overall persistence of the system. [source] The influence of changes in habitat structure on the species composition of bird assemblages in the southern KalahariAUSTRAL ECOLOGY, Issue 5 2010COLLEEN L. SEYMOUR Abstract Land use management practices often change habitat structure, which in turn influence diversity and the composition of floral and faunal assemblages. In the southern Kalahari, southern Africa, heavy grazing after above-average rainfall has lead to bush thickening, and widespread use of arboricides and/or removal of large trees for firewood has also impacted habitat structure. At sites near Kimberley, in South Africa, we investigated the effects of these changes on bird species richness and which aspects of habitat structure most influenced bird assemblage diversity and composition. We also investigated correlations between bird life history traits and habitat characteristics using RLQ analysis. Bird species richness and abundance were both explained by vertical habitat heterogeneity and density of woody species between the heights of 0,2 m, with bird species richness also explained by the density of woody species at heights above 6 m. Large trees within bush-thickened areas dampened the effects of bush thickening on bird assemblages by enabling certain species to persist, consistent with the idea that large trees are keystone structures. Smaller insectivorous gleaners, ball- and cup-nesters, birds with parts of their range extending into arid areas and birds with long-wavelength plumage (i.e. red, orange or yellow plumage) dominated bush-thickened habitats. Seed-eaters, burrow- and ground-nesters, bark-foragers, birds that perch and sally, or perch and swoop to the ground, were all negatively associated with bush thickening. Cavity-nesters, bark-foragers, hawkers, frugivores, birds that perch and sally and species with iridescent plumage were negatively affected by the loss of large trees. Of the common species analysed, nearly 40% of species had life history traits tied to large trees; and 68% had traits negatively associated with bush thickening and removal of large trees together, suggesting that where these changes in habitat occur simultaneously, bird diversity will be strongly affected. [source] The Aquatic Conservation Strategy of the Northwest Forest PlanCONSERVATION BIOLOGY, Issue 2 2006GORDON H. REEVES gestión de ecosistemas; gestión ribereña; modelos de soporte de decisiones; terrenos públicos Abstract:,Implemented in 1994, the Aquatic Conservation Strategy of the Northwest Forest Plan was designed to restore and maintain ecological processes for aquatic and riparian area conservation on federal lands in the western portion of the Pacific Northwest. We used decision support models to quantitatively evaluate changes in the condition of selected watersheds. In the approximately 10 years since strategy implementation, watershed condition scores changed modestly, but conditions improved in 64% of 250 sampled watersheds, declined in 28%, and remained relatively the same in 7%. Watersheds that had the largest declines included some where wildfires burned 30,60% of their area. The overall statistical distribution of the condition scores did not change significantly, however. Much of the increase in watershed condition was related to improved riparian conditions. The number of large trees (>51 cm diameter at breast height) increased 2,4%, and there were substantial reductions in tree harvest and other disturbances along streams. Whether such changes will translate into longer-term improvements in aquatic ecosystems across broader landscapes remains to be seen. Resumen:,Implementada en 1994, la Estrategia de Conservación Acuática del Plan Forestal del Noroeste fue diseñada para restaurar y mantener procesos ecológicos para la conservación de áreas acuáticas y ribereñas en terrenos federales en la porción occidental del Pacífico Noroeste (E.U.A.). Utilizamos modelos de soporte de decisiones para evaluar cuantitativamente los cambios en la condición de cuencas seleccionadas. En los casi 10 años desde la implementación de la estrategia, los valores de la condición de las cuencas cambiaron someramente, pero las condiciones mejoraron en 64% de las 250 cuencas muestreadas, declinaron en 28% y permanecieron relativamente iguales en 7%. Las cuencas con las mayores declinaciones incluyeron algunas en las que 30-60% de su superficie fue quemada por fuegos sin control. Sin embargo, la distribución espacial total de los valores no cambió significativamente. Buena parte del incremento en las condiciones de la cuenca se relacionó con el mejoramiento de las condiciones ribereñas. El número de árboles grandes (>51 cm diámetro a la altura del pecho) aumentó 2-4%, y hubo reducciones sustanciales en la cosecha de árboles y otras perturbaciones a lo largo de arroyos. Aun habrá que ver si tales cambios se traducirán en mejoramientos a largo plazo en los ecosistemas acuáticos en paisajes más extensos. [source] One Hundred Fifty Years of Change in Forest Bird Breeding Habitat: Estimates of Species DistributionsCONSERVATION BIOLOGY, Issue 6 2005LISA A. SCHULTE aptitud del hábitat; ecología aviar; ecología de paisaje; planificación de conservación Abstract:,Evaluating bird population trends requires baseline data. In North America the earliest population data available are those from the late 1960s. Forest conditions in the northern Great Lake states (U.S.A.), however, have undergone succession since the region was originally cut over around the turn of the twentieth century, and it is expected that bird populations have undergone concomitant change. We propose pre-Euro-American settlement as an alternative baseline for assessing changes in bird populations. We evaluated the amount, quality, and distribution of breeding bird habitat during the mid-1800s and early 1990s for three forest birds: the Pine Warbler (Dendroica pinus), Blackburnian Warbler (D. fusca), and Black-throated Green Warbler (D. virens). We constructed models of bird and habitat relationships based on literature review and regional data sets of bird abundance and applied these models to widely available vegetation data. Original public-land survey records represented historical habitat conditions, and a combination of forest inventory and national land-cover data represented current conditions. We assessed model robustness by comparing current habitat distribution to actual breeding bird locations from the Wisconsin Breeding Bird Atlas. The model showed little change in the overall amount of Pine Warbler habitat, whereas both the Blackburnian Warber and the Black-throated Green Warbler have experienced substantial habitat losses. For the species we examined, habitat quality has degraded since presettlement and the spatial distribution of habitat shifted among ecoregions, with range expansion accompanying forest incursion into previously open habitats or the replacement of native forests with pine plantations. Sources of habitat loss and degradation include loss of conifers and loss of large trees. Using widely available data sources in a habitat suitability model framework, our method provides a long-term analysis of change in bird habitat and a presettlement baseline for assessing current conservation priority. Resumen:,La evaluación de tendencias de las poblaciones de aves requiere de datos de referencia. En Norte América, los primeros datos disponibles de poblaciones son del final de la década de 1960. Sin embargo, las condiciones de los bosques en los estados de los Grandes Lagos (E.U.A.) han experimentado sucesión desde que la región fue talada en los inicios del siglo veinte, y se espera que las poblaciones de aves hayan experimentado cambios concomitantes. Proponemos que se considere al período previo a la colonización euro americana como referencia alternativa para evaluar los cambios en las poblaciones de aves. Evaluamos la cantidad, calidad y distribución del hábitat para reproducción de tres especies de aves de bosque (Dendroica pinus, D. fusca y D. virens) a mediados del siglo XIX e inicios del XX. Construimos modelos de las relaciones entre las aves y el hábitat con base en la literatura y conjuntos de datos de abundancia de aves y los aplicamos a los datos de vegetación ampliamente disponibles. Los registros topográficos de tierras públicas originales representaron las condiciones históricas del hábitat, y una combinación de datos del inventario forestal y de cobertura de suelo representaron las condiciones actuales. Evaluamos la robustez del modelo mediante la comparación de la distribución de hábitat actual con sitios de reproducción de aves registrados en el Wisconsin Breeding Bird Atlas. El modelo mostró poco cambio en la cantidad total de hábitat de Dendroica pinus, mientras que tanto D. fusca como D. virens han experimentado pérdidas sustanciales de hábitat. Para las especies examinadas, la calidad del hábitat se ha degradado desde antes de la colonización y la distribución espacial del hábitat cambió entre ecoregiones, con la expansión del rango acompañando la incursión de bosques en hábitats anteriormente abiertos o el reemplazo de bosques nativos con plantaciones de pinos. Las fuentes de pérdida y degradación de hábitats incluyen la pérdida de coníferas y de árboles grandes. Mediante la utilización de fuentes de datos ampliamente disponibles en un modelo de aptitud de hábitat, nuestro método proporciona un análisis a largo plazo de los cambios en el hábitat de aves y una referencia precolonización para evaluar prioridades de conservación actuales. [source] Assessing the relationship between forest types and canopy tree beta diversity in AmazoniaECOGRAPHY, Issue 4 2010Thaise Emilio Planning of conservation priorities has often taken mapped forest types as surrogates for biological complementarity. In the Brazilian Amazon, these exercises have given equal weight to each forest type as if they were all equally distinct. Here, we examine floristic similarity between forest types to assess the reliability of vegetation maps as a surrogate for canopy tree-community composition. We analyzed floristic differences at the genus level between twelve Amazonian forest types using 1184 one-hectare inventories of large trees with three complementary approaches. First, we compared a map of floristic composition, from a uni-dimensional NMDS ordination of the inventories, with a map of coarser-level forest types commonly recognized as distinct by classification systems across Amazonia. Using Mantel and means-difference tests, we next examined the distance-decay of floristic similarity for all paired samples and for the pairs drawn from within and between twelve more finely divided forest types. Finally, we examined the degree of floristic separation of each pair of the twelve forest types using non-parametric analysis of variance. Maps of floristic composition and coarse-level forest types were highly congruent. At the finer level of classification, similarity was only slightly higher when pairs were drawn from the same versus from different forest types. This was true for all geographic distances. Nonetheless, eighty percent of the 66 paired combinations of forest types were significantly different in the unreduced genus-space and nearly half showed little or no overlap in a two-dimensional ordination. Three types were most distinct from all others: white sand, seasonally dry, and bamboo-dominated forests. Here, we show that forest types exhibit variable degrees of separation. For this reason, treating all fine-level forest types as equally distinct results in poor representation of canopy tree beta diversity. We recommend explicitly considering the degree of floristic separation between all forest types , as presented here for Amazonian flora , as a way to improve the use of this biodiversity surrogate. [source] Postfledging habitat selection of juvenile middle spotted woodpeckers: a multi-scale approachECOGRAPHY, Issue 4 2009Carlos Ciudad Despite its relevance for the persistence of populations, the ecological mechanisms underlying habitat use decisions of juvenile birds are poorly understood. We examined postfledging habitat selection of radio-tracked juvenile middle spotted woodpeckers Dendrocopos medius at multiple hierarchically-nested spatial scales in NW Spain. At the landscape and home range scales, old oak forest was the most used and selected habitat, young oak forests and pine plantations were avoided, and riverside forests were used as available. At a lower scale, birds selected larger diameter trees for foraging. Home ranges had higher densities of large deciduous trees (mainly oaks Quercus spp., but also poplars Populus spp. and willows Salix spp. >22,cm and >33,cm DBH) selected for foraging by juveniles than non-used areas. These results suggest that foraging conditions may drive, at least partly, habitat use decisions by juvenile birds. We also discuss the potential influence of intraspecific competition, the search for a future breeding territory in the early postfledging period and predation avoidance on habitat use decisions by juvenile birds. Contrary to previous studies on migrant forest birds, postfledging juvenile woodpeckers selected the same habitat as for the breeding adults (i.e. old oak forest), indicating that migrant and resident specialist avian species may require different conservation actions. Conservation strategies of woodpecker populations should consider the protection of old oak forests with high densities of large trees to provide suitable habitat to breeding adults and postfledging juveniles. The habitat improvement for this indicator and umbrella species would also favour other organisms that depend on characteristics of old-growth oak forests. [source] Spatial population structure of a specialist leaf-mining mothJOURNAL OF ANIMAL ECOLOGY, Issue 4 2008Sofia Gripenberg Summary 1The spatial structure of natural populations may profoundly influence their dynamics. Depending on the frequency of movements among local populations and the consequent balance between local and regional population processes, earlier work has attempted to classify metapopulations into clear-cut categories, ranging from patchy populations to sets of remnant populations. In an alternative, dichotomous scheme, local populations have been classified as self-sustaining populations generating a surplus of individuals (sources) and those depending on immigration for persistence (sinks). 2In this paper, we describe the spatial population structure of the leaf-mining moth Tischeria ekebladella, a specialist herbivore of the pedunculate oak Quercus robur. We relate moth dispersal to the distribution of oaks on Wattkast, a small island (5 km2) off the south-western coast of Finland. 3We build a spatially realistic metapopulation model derived from assumptions concerning the behaviour of individual moths, and show that the model is able to explain part of the variation in observed patterns of occurrence and colonization. 4While the species was always present on large trees, a considerable proportion of the local populations associated with small oaks showed extinction,recolonization dynamics. The vast majority of moth individuals occur on large trees. 5According to model predictions, the dominance of local vs. regional processes in tree-specific moth dynamics varies drastically across the landscape. Most local populations may be defined broadly as ,sinks', as model simulations suggest that in the absence of immigration, only the largest oaks will sustain viable moth populations. Large trees in areas of high oak density will contribute most to the overall persistence of the metapopulation by acting as sources of moths colonizing other trees. 6No single ,metapopulation type' will suffice to describe the oak,moth system. Instead, our study supports the notion that real populations are often a mix of earlier identified categories. The level to which local populations may persist after landscape modification will vary across the landscape, and sweeping classifications of metapopulations into single categories will contribute little to understanding how individual local populations contribute to the overall persistence of the system. [source] Size of orchard trees as a factor affecting behavioural control of apple maggot flies (Dipt., Tephritidae) by trapsJOURNAL OF APPLIED ENTOMOLOGY, Issue 7 2001R. J. Prokopy Over a 3-year period (1997,1999), we examined the influence of tree size on effectiveness of traps for behaviourally controlling apple maggot flies, Rhagoletis pomonella (Walsh), in small blocks of trees in Massachusetts commercial apple orchards. Traps were red spheres coated with Tangletrap and baited with an attractive synthetic host fruit odour (butyl hexanoate). Traps were placed 6 m apart on perimeter apple trees of each block and were designed to intercept apple maggot flies immigrating into blocks from unmanaged host trees. Based on captures of adults by unbaited red spheres placed near the centre of each block to monitor degree of adult penetration into the interior and on percentages of fruit injured by apple maggot, traps surrounding blocks of small trees (1.5 m canopy diameter) planted at high density were more effective in controlling apple maggot flies (relative to control obtained by insecticide sprays used in comparison blocks) than were traps surrounding blocks of large trees (3.7 m canopy diameter) planted at low density, with traps surrounding blocks of medium-size trees (2.5 m canopy diameter) planted at medium density generally providing an intermediate level of control. [source] On cognitive conservation biology: why chickadees leave a patch of woodlandJOURNAL OF AVIAN BIOLOGY, Issue 4 2001Thomas C. Grubb Although not previously emphasized, colonization of habitat patches by cognitive animals involves both decisions bringing an animal to a particular patch and decisions causing the animal to remain in the patch. We focus on the latter form of decision by examining the habitat and landscape correlates of persistence in chickadees (Poecile spp.) that we introduced into small woodlots previously cleared of conspecifics. The birds' decisions to remain were associated importantly with the presence of a canopy layer of large trees, and less so with area of the woodland patch and distance they had been transported from the capture site. The decision to persist was little related to landscape features near the focal habitat patch. The future holds promise for application of principles of cognition to landscape biology. [source] Effect of selective logging on forest structure and nutrient cycling in a seasonally dry Brazilian Atlantic forestJOURNAL OF BIOGEOGRAPHY, Issue 3 2006Dora Maria Villela Abstract Aim, The Brazilian Atlantic forest covers c. 10% of its original extent, and some areas are still being logged. Although several ecological studies in Atlantic forest have been published over the past two to three decades, there has been little research on forest dynamics and there is a particular lack of information on the effects of disturbance. The aim of the present study was to assess the impact of selective logging on forest structure, floristic composition soil nutrients, litterfall and litter layer in a seasonally dry Atlantic forest. Location, The Mata do Carvão is located in the Guaxindiba Ecological Reserve in São Francisco do ltabapoana district (21°24, S, 41°04, W), Rio de Janeiro, Brazil. Methods, Four plots (50 × 50 m) were set up in 1995 in each of two stands: unlogged and logged. In each plot, all trees , 10 cm d.b.h. were enumerated, identified and measured. Vouchers were lodged at UENF Herbarium. Five surface soil samples were collected in each plot in the dry season (in October 1995). Litterfall was collected in eight traps (0.50 m2) in each plot over a year from 14 November 1995 to 11 November 1996. The litter layer was sampled in eight quadrats (0.25 m2) in each plot in the dry and wet seasons. Soils were air-dried, sieved, and chemically analysed. The litter was dried (80 °C), sorted into six fractions, weighed and bulked samples analysed for nutrients. Results, Forest stands did not differ in stem density and total basal area, with a total of 1137 individuals sampled in 1996 (564 unlogged and 573 logged), and a total basal area of 15 m2 (unlogged) and 13.0 m2 (logged). However, unlogged stands had more large trees (, 30 cm in d.b.h.) and greater mean canopy height. Among the families, Rutaceae and Leguminosae were the most abundant families in both sites, although the Rutaceae had a higher density in unlogged and Leguminosae in the logged stand. The species diversity index was similar between stands. Late-successional species, such as Metrodorea nigra var. brevifolia and Paratecoma peroba, were less abundant in the logged stand. Selective logging did not affect nutrient concentrations in the soil or in the litter. However, quantities of the nutrients in the total litterfall and in the leaf litterfall and litter layer were higher in unlogged than in logged stands, mainly as a result of fallen M. nigra leaves. Metrodorea nigra was considered a key species in the nutrients dynamics in Carvão forest. Main conclusions, Despite the fact that effects on tree diversity and soil nutrients were not clear, selective logging in this Atlantic forest altered canopy structure, increased the relative abundance of some early-secondary species and decreased the litter input and stock of nutrients. Detailed information on the influence of logging on the distribution and structure of plant populations and in nutrient processes is fundamental for a sustainable logging system to be developed. [source] Structural and floristic characteristics of some monodominant and adjacent mixed rainforests in New CaledoniaJOURNAL OF BIOGEOGRAPHY, Issue 2 2000J. Read Abstract Nothofagus spp. dominate the upper canopy of some rainforests on ultramafic soils in New Caledonia. These monodominant forests typically occur within, or contiguous with, larger areas of mixed-canopy rainforest. In this study the structure, diversity and composition of six Nothofagus -dominated plots were investigated, and comparisons were made with three adjacent mixed rainforest plots. Stand density and basal area (all stems , 1.3 m high) in the Nothofagus plots were in the range 16,056,27,550 stems/ha and 43.1,69.9 m2/ha, respectively. There was no significant difference (P , 0.05) in total stand density or basal area between the paired Nothofagus and mixed rainforests, but there were consistently fewer trees and less basal area of trees , 40 cm d.b.h. in the Nothofagus forests. Species richness, species diversity (Shannon-Wiener, based on basal area) and equitability (based on basal area) of trees , 20 cm d.b.h. on 0.1 ha Nothofagus plots were in the range 4,17, 0.96,3.76 and 0.45,0.87, respectively. No significant differences (P , 0.05) were recorded in these three parameters between the paired Nothofagus and mixed rainforests, although species diversity was consistently lower in the paired Nothofagus forests. Comparison of dominance by density and basal area indicated that although the uppermost canopy of the Nothofagus forests was dominated by Nothofagus (70,95%), the basal area and density contribution was , 55% except at Col de Yaté (, 85%). Analysis of similarity indicated no significant difference in stand composition of trees , 20 cm d.b.h. (following removal of Nothofagus from the data set) between Nothofagus and mixed rainforests using basal area, density or presence-absence data. It is concluded that the Nothofagus -dominated forests differ from the adjacent mixed rainforests mainly by (1) dominance of the uppermost canopy, without necessarily dominance of the stand by basal area or density, and (2) the smaller basal area contributed by large trees (all species). [source] Home ranges and survival of Nahan's Francolin Francolinus nahani in Budongo Forest, UgandaAFRICAN JOURNAL OF ECOLOGY, Issue 4 2009Eric Sande Abstract We studied home ranges, habitat use and survival of radio-tagged Nahan's Francolin in Budongo Forest Reserve, Uganda during July 1998,December 1999. We studied Nahan's Francolin in an unlogged nature reserve, in a compartment logged in 1947,1952 and in a compartment logged twice, in 1963,1964 and 1996,1997. Mean home range was 14.22 ± 1.35 ha (n = 17). The home range was significantly larger in the nature reserve than in the recently logged compartment. Birds spent more time during the day in areas with high understorey vegetation density but preferred to roost and nest between buttresses of large trees. Understorey vegetation density and canopy openness were significantly greater in the logged forest than in the nature reserve. Annual survival of adult Nahan's Francolins was 20.09 ± 7.33% (n = 23). Our results suggest that the maintenance of large trees and areas with high understorey vegetation density are both important for Nahan's Francolin. Résumé Nous avons étudié le territoire, l'utilisation de l'habitat et la survie de francolins de Nahan marqués dans la Réserve Forestière de Budongo, en Ouganda, entre juillet 1998 et décembre 1999. Nous avons étudié les francolins de Nahan dans une réserve naturelle non exploitée, dans une parcelle qui avait été exploitée entre 1947 et 1952 et dans une parcelle où des coupes de bois avaient eu lieu deux fois, en 1963,64 et en 1996,97. Le territoire moyen couvrait 14,22 ± 1,35 ha (n = 17). Le territoire était significativement plus grand dans la réserve naturelle que dans la parcelle récemment exploitée. Pendant la journée, les oiseaux passaient plus de temps dans les endroits où la végétation des sous-bois était très dense, mais ils préféraient se percher et nicher protégés par le rempart de grands arbres. La densité de la végétation des sous-bois et l'ouverture de la canopée étaient sensiblement plus grandes dans la forêt exploitée que dans la réserve naturelle. La survie annuelle des francolins adultes était de 20.09 ± 7.33% (n = 23). Nos résultats suggèrent que le maintien de grands arbres et de zones où la végétation des sous-bois est dense est très important pour le francolin de Nahan. [source] Changes in the structure and composition of miombo woodlands mediated by elephants (Loxodonta africana) and fire over a 26-year period in north-western ZimbabweAFRICAN JOURNAL OF ECOLOGY, Issue 2 2009Isaac Mapaure Abstract Changes in structure and composition of miombo woodlands mediated by elephants and fire were studied in 26-year-old permanent transects established in 1972 in north-western Zimbabwe. Elephants caused 48% decline in proportions of large trees (>11 cm diameter), significant reductions (30.9,90.9%) in tree heights, reductions in stem areas (43.5%) and densities (2.5%) of all trees. There were increases in proportions of small trees (64.8%), shrub canopy volumes (271%) and shrub densities (172%). These increases are attributed to natural recruitment because of longer fire-free periods and reduction of tree suppression effects on lower strata as a result of elephant-induced tree declines. Frequencies of occurrence of most species dropped by 28,89.6%. Brachystegia boehmii was replaced by Pseudolachnostylis maprouneifolia as the most dominant tree, largely because of high elephant preference for Brachystegia boehmii. A new suite of species, dominated by Combretaceae, increased in dominance resulting in local floristic changes. Reductions in old elephant (33.4%), old unknown (89.9%) and new elephant (13.7%) damage suggest that elephant occupancy of miombo woodlands has declined, possibly because of limited availability of preferred browse species. This study clearly shows that elephants and fire have contributed significantly to the changes in miombo woodlands in the area. Résumé Les changements de la structure et de la composition des forêts de miombo dus aux éléphants et aux feux ont étéétudiés sur des transects permanents établis en 1972 dans le nord-ouest du Zimbabwe. Les éléphants ont causé un déclin de 48% de la proportion de grands arbres (>11 cm de diamètre), des réductions significatives (30,9,90,9%) de la hauteur des arbres, des réductions de la surface des tiges (43,5%) et de la densité (2,5%) de tous les arbres. Il y avait des augmentations de la proportion de petits arbres (64,8%), du volume des buissons (271%) et de leur densité (172%). Ces augmentations sont attribuées au recrutement naturel dûà de plus longues périodes sans feux, et à la réduction des effets suppressifs des arbres sur les couches inférieures due au déclin des arbres induit par les éléphants. La fréquence de la plupart des espèces a chuté de 28%à 89,6%. Brachystegia boehmi a été remplacé par Pseudolachnostylis maprouneifolia comme arbre dominant, en grande partie à cause de la forte préférence marquée par les éléphants pour Brachystegia boehmi. Une nouvelle série d'espèces, dominée par des Combrétacées, a accru sa dominance et entraîné des changements floristiques locaux. La réduction des dommages « anciens dus aux éléphants » (33,4%), « anciens d'origine inconnue » (,9,9%) et « nouveaux dus aux éléphants » (13,7%) suggère que l'occupation des forêts de miombo par les éléphants a diminué, peut-être à cause de la disponibilité limitée des espèces fourragères qu'ils préfèrent. Cette étude montre clairement que les éléphants et les feux ont contribué significativement aux changements survenus dans les forêts de miombo de la région. [source] Trends in woody vegetation cover in the Kruger National Park, South Africa, between 1940 and 1998AFRICAN JOURNAL OF ECOLOGY, Issue 2 2000H. C. Eckhardt Changes in the cover and density of shrubs and trees were assessed from aerial photographs (1940, 1974 and 1998) as well as from fixed-point photographs taken in 1984 and 1996 in the Kruger National Park, South Africa. Woody cover (trees and shrubs combined) increased by 12% on granite substrates but decreased by 64% on basalt substrates over the past 58 years. Both these figures are expressed in terms of the initial values, respectively. The density of the large tree component of woody vegetation decreased on both substrates. Woody vegetation cover declined as fire return periods became shorter, but the relationship was weak. The increases in woody plant density and cover on granite are thought to be the result of decreased competition from grasses, which in turn is a result of overgrazing by wild herbivores whose numbers have been kept high through the provision of surface water. These effects were not seen on the relatively nutrient-rich basalts, where grasses can recover rapidly even after heavy grazing. The decline in overall woody cover on basalts is interpreted as a result of regular, short-interval prescribed burning over the past 40 years, while the universal decline in large trees seems to result from an interaction between regular, frequent fires and utilization by elephants. The implications for management are discussed. Résuné On a évalué les changements du couvert et de la densité des arbustes et des arbres à partir de photos aériennes (1940, 1974 et 1998) et de photos prises d'un endroit fixe en 1984 et en 1996 dans le Parc National Kruger, en Afrique du Sud. Le couvert boisé (arbustes et arbres pris ensemble) a augmenté de 12% sur les substrats granitiques mais diminué de 64% sur les substrats basaltiques, au cours des 58 dernières années. Ces deux chiffres sont exprimés en termes de valeurs initiales, respectivement. La densité de la composante de grands arbres de la végétation boisée a diminué sur les deux substrats. Le couvert végétal boisé a diminué alors que les périodes de récupération entre les feux raccourcissaient, mais la relation est faible. On pense que l'augmentation de la densité et du couvert boisés sur le granite est le résultat d'une diminution de la compétition exercée par les herbes qui elle, résulte d'un surpâturage des herbivores sauvages dont le nombre a été maintenu élevé par l'apport d'eau de surface. On n'a pas observé ces effets sur les basaltes relativement riches en nutriments, car les herbes peuvent y repousser rapidement même après un pâturage intense. On interprète le déclin du couvert boisé global sur le basalte comme le résultat des feux provoqués régulièrement et avec de brefs intervalles depuis 40 ans, alors que le déclin général des grands arbres semble être le résultat d'une interaction entre les feux, réguliers et fréquents, et la présence des éléphants. On discute de ce que cela implique pour la gestion. [source] Effects of size, competition and altitude on tree growthJOURNAL OF ECOLOGY, Issue 5 2007DAVID A. COOMES Summary 1,Understanding the factors influencing tree growth is central to forest ecology because of the significance of growth to forest structure and biomass. One of the simplest, yet most controversial growth models, proposed by Enquist and colleagues, predicts that stem-diameter growth scales as the one-third power of stem diameter. Recent analyses of large-scale data sets have challenged the generality of this theory and highlighted the influence of resource competition on the scaling of growth with size. 2Here we explore the factors regulating the diameter growth of 3334 trees of mountain beech (Nothofagus solandri var. cliffortioides) growing in natural single-species forests in New Zealand. Maximum-likelihood modelling was used to quantify the influences of tree size, altitude, the basal area of taller neighbours (BL) and the basal area of all neighbours (BT) on growth. Our interpretation of the models assumed that taller neighbours compete for light whereas all neighbours compete for nutrients. 3The regression analyses indicate that competition for light has a strong influence on the growth of small trees, whereas competition for nutrients affects trees of all sizes. These findings are consistent with experimental manipulation studies showing that competition for light and nutrients inhibits the growth of small mountain beech trees, and fertilizer application studies showing that nitrogen limits the growth of large trees. 4Tree growth declined with altitude. The regression analyses suggest that the intensity of light competition also declines with altitude, when trees with similar BT and BL values were compared along the gradient. These results are consistent with observations that trees become stunted and have more open canopies at high altitudes. 5Our study is the first to build the effects of competition and environment into Enquist's model of tree growth. We show that competitive interactions alter the scaling of mean growth rate with size, whereas altitude does not influence the scaling of potential growth rate with size. [source] Developmental changes in habitat associations of tropical treesJOURNAL OF ECOLOGY, Issue 3 2007LIZA S. COMITA Summary 1Recent studies have documented local-scale associations between tree species and topographic and edaphic habitat types in forests worldwide. To determine whether such associations form at early life stages, we compared species' positive associations with five habitat types (high plateau, low plateau, slope, streamside, and swamp) at two life stages for 80 tree and shrub species in a Panamanian lowland forest. 2Nineteen significant, positive habitat associations were detected at the small tree stage (seedlings and saplings , 20 cm tall and < 1 cm d.b.h.), and 18 at the large tree stage (individuals , 1 cm d.b.h.), according to results of torus-translation randomization tests. The majority of species did not show consistent associations at the two stages. Of the 30 species significantly associated with a habitat, only five were associated with the same habitat at both stages. Overall, more species were associated with the wetter slope habitat at the large tree stage compared with the small tree stage. 3For a subset of species, we examined the relationship between observed habitat associations and seed dispersal and seedling establishment patterns by using species-specific seed dispersal kernels to predict seed rain into each habitat. 4Two-thirds of species associated with a habitat at the large tree stage had higher predicted seed densities in the associated habitat relative to other habitat types, indicating that limited seed dispersal acts to reinforce habitat associations for most species. In contrast, only one-third of the species associated with a habitat at the large tree stage showed evidence of higher seedling establishment rates in the associated habitat compared with other habitats, and an equal number of species appeared to have lower rates of establishment in the habitat that large trees of the species were associated with. 5Overall, our results indicate that habitat associations of large trees typically do not form at early life stages. Rather, many species appear to exhibit different ecological habitat preferences across life stages. Future studies of species' habitat associations should therefore include multiple life stages in order to detect developmental shifts in ecological preferences. [source] Habitat associations of Sterculiaceae trees in a Bornean rain forest plotJOURNAL OF VEGETATION SCIENCE, Issue 5 2006Toshihiro Yamada Ashton (1980) Abstract. Questions: 1. Are trees in a Bornean tropical rain forest associated with a particular habitat? 2. Does the strength of habitat association with the species-specific optimal habitat increase with tree size? Location: A 52-ha plot in a mixed dipterocarp forest in a heterogeneous landscape at the Lambir Hills National Park, Sarawak, East Malaysia. Methods: Ten species from the Sterculiaceae were chosen as representative of all species in the plot, on the assumption that competition among closely related species is more stringent than that among more distantly related taxa. Their habitat associations were tested using data from a 52-ha plot by a torus-translation test. Results: The torus-translation test showed that eight out of the ten species examined had significant association with at least one habitat. We could not find negative species-habitat associations for rare species, probably due to their small sample sizes. Among four species small trees were less strongly associated with habitat than large trees, implying competitive exclusion of trees in suboptimal habitats. The other four species showed the opposite pattern, possibly owing to the smaller sample size of large trees. A habitat had a maximum of three species with which it was significantly positively associated. Conclusions: For a species to survive in population equilibrium in a landscape, habitats in which ,source' subpopulations can be sustained without subsidy from adjacent habitats are essential. Competition is most severe among related species whose source subpopulations share the same habitat. On the evidence of source subpopulations identified by positive species-habitat association, species-habitat association reduces the number of confamilial competitors. Our results therefore indicate that edaphic niche specialization contributes to coexistence of species of Sterculiaceae in the plot, consistent with the expectations of equilibrium hypotheses. [source] Habitat selection and habitat-specific survival of fledgling ovenbirds (Seiurus aurocapilla)JOURNAL OF ZOOLOGY, Issue 4 2006D. I. King Abstract Patterns of habitat use by some passerines change after the young leave the nest, and thus our understanding of habitat selection derived from counts of singing males earlier in the nesting cycle may not adequately represent the breeding habitat requirements of these species. Post-fledging changes in habitat use may have important conservation implications if the survival of fledglings is affected by characteristics of the habitat; however, there have been relatively few systematic studies of the post-fledging ecology of forest passerines and, of these, even fewer have incorporated analyses of the relationship between habitat characteristics and fledgling survival. We studied the post-fledging habitat selection and survival of ovenbirds Seiurus aurocapilla in northern New Hampshire, USA during two breeding seasons using radio telemetry. Habitat at sites used by radio-marked fledgling ovenbirds was characterized by fewer large trees and greater vertical structure 0,3 m above ground than ovenbird nest sites. Similarly, habitat at sites used by fledgling ovenbirds was characterized by fewer large trees and greater vertical structure than unused sites. Most (80%) of the 15 mortalities that we observed were due to predation. Nine (70%) of these occurred within the first 3 days of fledging, resulting in a significant drop in survival during this period. Fledgling survival increased significantly with increased vegetation structure. Our observations that fledgling ovenbirds are selective in their habitat use, that they select different habitat features than adult ovenbirds select for nesting and that fledgling survival is positively associated with these habitat features suggest that the use of habitat models based on counts of singing males before fledging does not adequately represent the habitat needs of this species. Conceivably, mortality during the post-fledging period could limit recruitment to levels insufficient to maintain the viability of ovenbird population even if adequate nesting habitat were available. [source] Capacitive effect of cavitation in xylem conduits: results from a dynamic modelPLANT CELL & ENVIRONMENT, Issue 1 2009TEEMU HÖLTTÄ ABSTRACT Embolisms decrease plant hydraulic conductance and therefore reduce the ability of the xylem to transport water to leaves provided that embolized conduits are not refilled. However, as a xylem conduit is filled with gas during cavitation, water is freed to the transpiration stream and this transiently increases xylem water potential. This capacitive effect of embolism formation on plant function has not been explicitly quantified in the past. A dynamic model is presented that models xylem water potential, xylem sap flow and cavitation, taking into account both the decreasing hydraulic conductance and the water release effect of xylem embolism. The significance of the capacitive effect increases in relation to the decreasing hydraulic conductance effect when transpiration rate is low in relation to the total amount of water in xylem conduits. This ratio is typically large in large trees and during drought. [source] Physiological girdling of pine trees via phloem chilling: proof of conceptPLANT CELL & ENVIRONMENT, Issue 1 2007KURT JOHNSEN ABSTRACT Quantifying below-ground carbon (C) allocation is particularly difficult as methods usually disturb the root,mycorrhizal,soil continuum. We reduced C allocation below ground of loblolly pine trees by: (1) physically girdling trees and (2) physiologically girdling pine trees by chilling the phloem. Chilling reduced cambium temperatures by approximately 18 °C. Both methods rapidly reduced soil CO2 efflux, and after approximately 10 days decreased net photosynthesis (Pn), the latter indicating feedback inhibition. Chilling decreased soil-soluble C, indicating that decreased soil CO2 efflux may have been mediated by a decrease in root C exudation that was rapidly respired by microbes. These effects were only observed in late summer/early autumn when above-ground growth was minimal, and not in the spring when above-ground growth was rapid. All of the effects were rapidly reversed when chilling was ceased. In fertilized plots, both chilling and physical girdling methods reduced soil CO2 efflux by approximately 8%. Physical girdling reduced soil CO2 efflux by 26% in non-fertilized plots. This work demonstrates that phloem chilling provides a non-destructive alternative to reducing the movement of recent photosynthate below the point of chilling to estimate C allocation below ground on large trees. [source] Recommendations for Integrating Restoration Ecology and Conservation Biology in Ponderosa Pine Forests of the Southwestern United StatesRESTORATION ECOLOGY, Issue 1 2006Reed F. Noss Abstract Over the past century, ponderosa pine,dominated landscapes of the southwestern United States have been altered by human activities such as grazing, timber harvest, road building, and fire exclusion. Most forested areas within these landscapes now show increased susceptibility to stand-replacing fires, insect outbreaks, and drought-related mortality. Recent large wildfires in the region have spurred public interest in large-scale fuel reduction and restoration programs, which create perceived and real conflicts with the conservation of biodiversity. Conservation concerns include the potential for larger road networks, soil and understory disturbance, exotic plant invasion, and the removal of large trees in treated areas. Pursuing prescribed burning, thinning, or other treatments on the broad scale that many scientists and managers envision requires the reconciliation of ecological restoration with biodiversity conservation. This study presents recommendations from a workshop for integrating the principles and practices of restoration ecology and conservation biology, toward the objective of restoring the composition, structure, and function of dry ponderosa pine forests. Planning on the scale of hundreds of thousands of hectares offers opportunities to achieve multiple objectives (e.g., rare species protection and restoration of ecological structures and processes) that cannot easily be addressed on a site-by-site basis. However, restoration must be coordinated with conservation planning to achieve mutual objectives and should include strict guidelines for protection of rare, declining, and sensitive habitats and species. [source] Vegetation correlates of gibbon density in the peat-swamp forest of the Sabangau catchment, Central Kalimantan, IndonesiaAMERICAN JOURNAL OF PRIMATOLOGY, Issue 7 2010Marie Hamard Abstract Understanding the complex relationship between primates and their habitats is essential for effective conservation plans. Peat-swamp forest has recently been recognized as an important habitat for the Southern Bornean gibbon (Hylobates albibarbis), but information is scarce on the factors that link gibbon density to characteristics of this unique ecosystem. Our aims in this study were firstly to estimate gibbon density in different forest subtypes in a newly protected, secondary peat-swamp forest in the Sabangau Catchment, Indonesia, and secondly to identify which vegetation characteristics correlate with gibbon density. Data collection was conducted in a 37.1,km2 area, using auditory sampling methods and vegetation "speed plotting". Gibbon densities varied between survey sites from 1.39 to 3.92,groups/km2. Canopy cover, tree height, density of large trees and food availability were significantly correlated with gibbon density, identifying the preservation of tall trees and good canopy cover as a conservation priority for the gibbon population in the Sabangau forest. This survey indicates that selective logging, which specifically targets large trees and disrupts canopy cover, is likely to have adverse effects on gibbon populations in peat-swamp forests, and calls for greater protection of these little studied ecosystems. Am. J. Primatol. 72:607,616, 2010. © 2010 Wiley-Liss, Inc. [source] Tree and forest characteristics influence sleeping site choice by golden lion tamarinsAMERICAN JOURNAL OF PRIMATOLOGY, Issue 9 2007Sarah J. Hankerson Abstract Lion tamarin monkeys are among a small number of primates that repeatedly use a few tree holes for the majority of their sleeping sites. To better understand why lion tamarins rely on tree holes as sleeping sites, we compared the physical characteristics of frequently used sleeping sites, infrequently used sleeping sites, and randomly selected forest locations at multiple spatial scales. From 1990 to 2004, we recorded 5,235 occurrences of sleeping site use by 10 groups of golden lion tamarins (Leontopithecus rosalia) in Poço das Antas Reserve, Rio de Janeiro State, Brazil. Of those, 63.6% were tree holes. Bamboo accounted for an additional 17.5% of observations. Frequently used tree holes were more likely to be found in living trees and their entrances were at lower canopy heights than infrequently used tree holes. We also found that frequently used sleeping sites, in comparison to random sites, were more likely to be found on hillsides, be close to other large trees, have a lower percent of canopy cover, and have larger diameter at breast height. Topography and small-scale variables were more accurate than were habitat-level classifications in predicting frequently used sleeping sites. There are ample tree holes available to these lion tamarins but few preferred sites to which they return repeatedly. The lion tamarins find these preferred sites wherever they occur including in mature forest and in relics of older forest embedded in a matrix of secondary forest. Am. J. Primatol. 69:976,988, 2007. © 2007 Wiley-Liss, Inc. [source] Radial growth responses to gap creation in large, old Sequoiadendron giganteumAPPLIED VEGETATION SCIENCE, Issue 4 2010Robert A. York Abstract Questions: Do large, old Sequoiadondron giganteum trees respond to the creation of adjacent canopy gaps? Do other co-occurring tree species and younger S. giganteum adjacent to gaps also respond? What are the likely factors affecting growth responses? Location: Mixed-conifer forests of the southern Sierra Nevada, California, USA. Methods: We measured the growth response of large, old S. giganteum trees (mean DBH=164 cm; ages estimated >1000 yr) to gap creation by coring trees and comparing growth after gap creation to growth before gap creation. We also measured young Abies concolor, Pinus lambertiana, and young S. giganteum. Gap-adjacent trees were compared with non-adjacent reference trees. Tree rings were analysed for carbon isotope discrimination and for longer-term growth trend correlations with climate. Results: Following gap creation gap-adjacent old S. giganteum grew more than reference trees. Abies concolor trees also exhibited a growth response to gap creation. No response was detected for young S. giganteum or P. lambertiana, although detection power was lower for these groups. There was no difference in carbon isotope discrimination response to gap creation between gap-adjacent and reference trees for old S. giganteum and radial growth was positively correlated with winter precipitation, but not growing season temperature. Conclusion: It is unclear what caused the growth release in old S. giganteum trees, although liberation of below-ground resources following removal of competing vegetation appears to be a significant contributor. Sequoiadondron giganteum, the third-longest lived and the largest of all species, remains sensitive to local environmental changes even after canopy emergence. Management activities that reduce vegetation surrounding individual specimen trees can be expected to result in increased vigor of even these very old and large trees. [source] Variation in ecophysiology and carbon economy of invasive and native woody vines of riparian zones in south-eastern QueenslandAUSTRAL ECOLOGY, Issue 6 2010OLUSEGUN O. OSUNKOYA Abstract Exotic and invasive woody vines are major environmental weeds of riparian areas, rainforest communities and remnant natural vegetation in coastal eastern Australia, where they smother standing vegetation, including large trees, and cause canopy collapse. We investigated, through glasshouse resource manipulative experiments, the ecophysiological traits that might facilitate faster growth, better resource acquisition and/or utilization and thus dominance of four exotic and invasive vines of South East Queensland, Australia, compared with their native counterparts. Relative growth rate was not significantly different between the two groups but water use efficiency (WUE) was higher in the native species while the converse was observed for light use efficiency (quantum efficiency, AQE) and maximum photosynthesis on a mass basis (). The invasive species, as a group, also exhibited higher respiration load, higher light compensation point and higher specific leaf area. There were stronger correlations of leaf traits and greater structural (but not physiological) plasticity in invasive species than in their native counterparts. The scaling coefficients of resource use efficiencies (WUE, AQE and respiration efficiency) as well as those of fitness (biomass accumulated) versus many of the performance traits examined did not differ between the two species-origin groups, but there were indications of significant shifts in elevation (intercept values) and shifts along common slopes in many of these relationships , signalling differences in carbon economy (revenue returned per unit energy invested) and/or resource usage. Using ordination and based on 14 ecophysiological attributes, a fair level of separation between the two groups was achieved (51.5% explanatory power), with AQE, light compensation point, respiration load, WUE, specific leaf area and leaf area ratio, in decreasing order, being the main drivers. This study suggests similarity in trait plasticity, especially for physiological traits, but there appear to be fundamental differences in carbon economy and resource conservation between native and invasive vine species. [source] The influence of changes in habitat structure on the species composition of bird assemblages in the southern KalahariAUSTRAL ECOLOGY, Issue 5 2010COLLEEN L. SEYMOUR Abstract Land use management practices often change habitat structure, which in turn influence diversity and the composition of floral and faunal assemblages. In the southern Kalahari, southern Africa, heavy grazing after above-average rainfall has lead to bush thickening, and widespread use of arboricides and/or removal of large trees for firewood has also impacted habitat structure. At sites near Kimberley, in South Africa, we investigated the effects of these changes on bird species richness and which aspects of habitat structure most influenced bird assemblage diversity and composition. We also investigated correlations between bird life history traits and habitat characteristics using RLQ analysis. Bird species richness and abundance were both explained by vertical habitat heterogeneity and density of woody species between the heights of 0,2 m, with bird species richness also explained by the density of woody species at heights above 6 m. Large trees within bush-thickened areas dampened the effects of bush thickening on bird assemblages by enabling certain species to persist, consistent with the idea that large trees are keystone structures. Smaller insectivorous gleaners, ball- and cup-nesters, birds with parts of their range extending into arid areas and birds with long-wavelength plumage (i.e. red, orange or yellow plumage) dominated bush-thickened habitats. Seed-eaters, burrow- and ground-nesters, bark-foragers, birds that perch and sally, or perch and swoop to the ground, were all negatively associated with bush thickening. Cavity-nesters, bark-foragers, hawkers, frugivores, birds that perch and sally and species with iridescent plumage were negatively affected by the loss of large trees. Of the common species analysed, nearly 40% of species had life history traits tied to large trees; and 68% had traits negatively associated with bush thickening and removal of large trees together, suggesting that where these changes in habitat occur simultaneously, bird diversity will be strongly affected. [source] Variation in litter under individual tree crowns: Implications for scattered tree ecosystemsAUSTRAL ECOLOGY, Issue 1 2010CHRIS MCELHINNY Abstract In forest ecosystems litter is usually assessed in terms of the average amount produced by the canopy. In scattered tree ecosystems this approach is problematic because the canopy is discontinuous and the spatial arrangement of litter highly variable. We addressed this problem by quantifying the spatial variation in litter load and litter composition associated with individual trees in a Eucalyptus melliodora , Eucalyptus blakelyi woodland. Litter was sampled under crowns and in grassland adjacent to 10 E. blakelyi and 10 E. melliodora trees ranging in diameter at breast height (dbh) from 14 to 129 cm. A total of 302 L samples were collected from these trees, at distances ranging from 0 to 42 m from main stem. The sampled litter loads ranged from 0.02 to 109.3 t ha,1 and were significantly higher under tree crowns than in grassland for litter and each component of litter (leaves, bark, fine twigs, coarse twigs). In particular, the mean litter load under tree crowns (12.5 t ha,1) was an order of magnitude higher than the mean litter load in grassland (1.27 t ha,1). There was a significant (P = 0.0103) positive relationship between mean litter load under the tree crown and dbh, indicating larger trees produced more litter per unit area of ground than smaller trees. Generalized Linear Modelling produced highly significant (P < 0.0001) models predicting the spatial variation in litter load and litter composition in terms of distance from main stem and dbh. Our models demonstrate gradients in litter load and composition under tree crowns. These gradients were most pronounced for the large trees in our study. The disproportionate input of litter and variety of litter components associated with large trees in our study supports their keystone role in scattered tree ecosystems and highlights the need to maintain these structures in agricultural landscapes. [source] Impacts of grazing, selective logging and hyper-aggressors on diurnal bird fauna in intact forest landscapes of the Brigalow Belt, QueenslandAUSTRAL ECOLOGY, Issue 6 2009TERESA J. EYRE Abstract The impact of forest management on diurnal bird assemblages and abundance was investigated in contiguous tracts of eucalypt forest in the Brigalow Belt Bioregion, south central Queensland. Sites were located across three levels of livestock grazing intensity and three levels of selective logging intensity within the most extensive habitat type, Corymbia citriodora -dominant forest. We recorded a high rate of incidence and large numbers of the hyper-aggressive noisy miner Manorina melanocephala (Passeriformes: Meliphagidae) at the majority of our survey sites, a phenomenon rarely reported in non-cleared landscapes. As shown by numerous studies in fragmented landscapes, the distribution of this species in our study had a substantial negative effect upon the distribution of small passerine species. Noisy miners exerted the strongest influence upon small passerine abundance, and masked any forest management effects. However, key habitat features important for small passerines were identified, including a relatively high density of large trees and stems in the midstorey. Selective logging appeared to exert a minimal effect upon noisy miner abundance, whereas grazing intensity had a profound, positive influence. Noisy miners were most abundant in intensively grazed forest with minimal midstorey and a low volume of coarse woody debris. Higher road density in the forest landscape also corresponded with increased numbers of noisy miners. Reduction in grazing pressure in Brigalow Belt forests has the potential to benefit small passerine assemblages across large areas through moderating noisy miner abundance. The strong relationship between noisy miners and small passerines suggests that noisy miner abundance could act as an easily measured indicator of forest condition, potentially contributing to monitoring of forest management outcomes. [source] Influence of canopy tree size on stand basal area may reflect uncoupling of crown expansion and trunk diameter growthAUSTRAL ECOLOGY, Issue 2 2003Christopher H. Lusk Abstract A recent article by Midgley and colleagues suggests that large trees give rise to inordinately high stand basal areas because they pack canopy space more efficiently than smaller trees. We argue that this phenomenon bears more relation to the fact that diameter increment is not necessarily accompanied by significant crown expansion during all stages of a tree's life. Using data from a canopy tree population in an old-growth temperate forest, we found that crown area scaled as roughly the 3/5 power of trunk basal area. Rather than reflecting fixed scaling laws, we suggest that this pattern arises because of limited opportunities for crown expansion in dense stands. Old canopy trees in dense stands can thus accumulate large basal areas without occupying a commensurately large canopy area. [source] Relationship Between Aboveground Biomass and Multiple Measures of Biodiversity in Subtropical Forest of Puerto RicoBIOTROPICA, Issue 3 2010Heather D. Vance-Chalcraft ABSTRACT Anthropogenic activities have accelerated the rate of global loss of biodiversity, making it more important than ever to understand the structure of biodiversity hotspots. One current focus is the relationship between species richness and aboveground biomass (AGB) in a variety of ecosystems. Nonetheless, species diversity, evenness, rarity, or dominance represent other critical attributes of biodiversity and may have associations with AGB that are markedly different than that of species richness. Using data from large trees in four environmentally similar sites in the Luquillo Experimental Forest of Puerto Rico, we determined the shape and strength of relationships between each of five measures of biodiversity (i.e., species richness, Simpson's diversity, Simpson's evenness, rarity, and dominance) and AGB. We quantified these measures of biodiversity using either proportional biomass or proportional abundance as weighting factors. Three of the four sites had a unimodal relationship between species richness and AGB, with only the most mature site evincing a positive, linear relationship. The differences between the mature site and the other sites, as well as the differences between our richness,AGB relationships and those found at other forest sites, highlight the crucial role that prior land use and severe storms have on this forest community. Although the shape and strength of relationships differed greatly among measures of biodiversity and among sites, the strongest relationships within each site were always those involving richness or evenness. Abstract in Spanish is available at http://www.blackwell-synergy.com/loi/btp [source] | |||||||||||||