bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reproductive Phenology of Woody Species in a North Australian Tropical Savanna1
Authors: Williams Richard J. , Myers Bronwyn A. , Eamus Derek , Duff Gordon A. 
Published: March 2006

ABSTRACTInterspecific and interannual variation in reproductive phenology was quantified for 50 common species of trees and shrubs from a mesic savanna near Darwin, northern Australia. The presence of buds, flowers, and fruit was noted over a 30‐month period, from September 1992 to February 1995. Surveys were undertaken at monthly intervals for the less common species, and at bimonthly intervals for ten of the common trees and tall shrubs. The majority of species flowered each year at about the same time. There was no evidence of sub‐annual or continuous regimes of reproductive phenology. There was no supra‐annual carryover of seed‐bearing fruit in the canopy of any species. The peak flowering periods were the mid to late dry season (July–August) and the transition between the dry season and the wet season (October–November). The two dominant trees–Eucalyptus miniata and E, tetrodonta– flowered during the dry season, thereby providing resources for some elements of the vertebrate fauna. Flowering and fruiting were uncommon at the end of the wet season (February/March), although two species that flower and fruit at this time (E. porrecta and Terminalia ferdinandianas may provide resources to consumers at a time when floral or fruit resources are otherwise scarce. Because the peak of reproductive activity takes place during the late dry season, fruit maturity and seed dispersal have occurred prior to the onset of the rainy season for most species, and germination and seedling establishment potentially may take effect in response to the first rains. Late dry season fires, which tend to be extensive and intense, are a potential threat to the floral and fruit reserves within these savannas.
Distribution of Two Sympatric Species of Sloths (Choloepus didactylus and Bradypus tridactylus) along the Sinnamary River, French Guiana1
Authors: Taube Erica , Vié Jean–Christophe , Fournier Pascal , Genty Christophe , Duplantier Jean–Marc 
Published: March 2006

ABSTRACTDuring the filling of the Petit Saut dam in French Guiana, a wildlife rescue operation was conducted for 17 months. Over 900 sloths (Bradypus tridactylus and Choloepus didactylus) were captured along the Sinnamary River in a primary rain forest that was largely undisturbed at the outset. Raw densities of 1.7 B, tridactyluslkm1 and 0.9 C. didactylusl km2 were estimated. The distribution of captures was relatively continuous for both species along the rivers; variations most likely reflected biases due to capture methods. The highest densities of captures were located mainly in marshy areas. During the first months, due to different probabilities of sighting the two species, B. tridactylus captures predominated; however, as defoliation advanced, captures of C. didactylus reached the same level. In both species, over 73 percent of individuals captured were solitary and another 23‐24 percent were females carrying young, accounting for 96 percent of emancipated individuals.
A Comparison of the Soil Water, Nutrient Status, and Litterfall Characteristics of Tropical Heath and Mixed‐Dipterocarp Forest Sites in Brunei1
Authors: Moran Jonathan A. , Barker Martin G. , Moran Alison J. , Becker Peter , Ross Sheila M. 
Published: March 2006

ABSTRACTTwo of the main hypotheses to explain the distribution and special characteristics of tropical heath forest are nutrient and water limitation. A study was undertaken to investigate both factors on two sites under tropical heath forest (Badas Forest Reserve) and mixed‐dipterocarp forest (Andulau Forest Reserve) in Brunei. Soil water potentials were monitored at depths of 20, 50, and 90 cm over wet and dry periods for five months at each site. The results showed the mixed‐dipterocarp forest site to be drier at 50 cm depth compared to the tropical heath forest site. There was no significant difference in water potentials between sites at 20 or 90 cm. Nutrient concentrations in the soil solution were monitored at the same depths over a seven‐month period at the same sites. A 12‐month litterfall study was also undertaken to monitor nutrient returns from the canopy at each site. The results of both studies suggest that the tropical heath forest site is poorer in nitrogen, but richer in calcium, than the mixed‐dipterocarp forest site. The results for phosphorus are less clear, but do not suggest that its limitation is a significant factor at the tropical heath forest site compared to the mixed‐dipterocarp forest site. Phosphorus and magnesium concentrations in the soil solution showed a strong positive correlation with sliding 30‐day rainfall totals at both sites.
The Role of Soil Seed Banks in the Rehabilitation of Degraded Hillslopes in Southern Wello, Ethiopia1
Authors: Tekle Kebrom , Bekele Tesfaye 
Published: March 2006

ABSTRACTThe species composition in the soil seed bank of degraded hillslopes in southern Wello, Ethiopia, was assessed using the seedling emergence method and compared with that of the standing vegetation. Surface soils were sampled at 0‐to 5‐cm depth from 49 plots of four physiognomic vegetation classes (hereafter vegetation classes): forests, shrublands, grasslands, and degraded sites. Soils were spread on sterile sand in a glasshouse and watered. Emerging seedlings were recorded for five months until no new seedlings emerged. A total of 3969 seedlings belonging to 71 species and 30 families germinated. The species composition of the seed bank was dominated by 53 herb species (75%) compared to 2 tree species which accounted for only 3 percent of the total number of species. Seedling density differed significantly among vegetation classes and ranged from 391 to 7807 seeds/m2. Mean species richness also differed significantly among the vegetation classes. Forty‐two species were found to be common to the seed banks and the standing vegetation; however, correspondence between species numbers and composition of the seed banks and the standing vegetation was poor. Although most of the species that germinated in the seed banks were herbs and grasses, they can develop a vegetative cover and contribute to reduction of soil erosion. Regeneration of the tree species (some of which have seed viability up to four years) however, requires both time and the presence of mature individuals. Together with hillside closure and soil conservation measures (e.g., terracing), planting of native woody seedlings might help to expedite rehabilitation of degraded hillslopes devoid of trees and shrubs.
Forest Succession and Distance from Forest Edge in an Afro‐Tropical Grassland1
Authors: Duncan R. Scot , Duncan Virginia E. 
Published: March 2006

ABSTRACTForest succession on degraded tropical lands often is slowed by impoverished seed banks and low rates of seed dispersal. Within degraded landscapes, remnant forests are potential seed sources that could enhance nearby forest succession. The spatial extent that forest can influence succession, however, remains largely unstudied. In abandoned agricultural lands in Kibale National Park, Uganda, recurrent fires have helped perpetuate the dominance of tall (2–3 m) grasses. We examined the effects of distance from forest and grassland vegetation structure on succession in a grassland having several years of fire exclusion. At 10 and 25 m from forest edge, we quantified vegetation patterns, seed predation, and survival of planted tree seedlings. Natural vegetation was similar at both distances, as was seed (eight species) and seedling (six species) survival; however, distance may be important at spatial or temporal scales not examined in this study. Our results offer insight into forest succession on degraded tropical grasslands following fire exclusion. Naturally recruited trees and tree seedlings were scarce, and seed survival was low (20% after 7 mo). While seedling survival was high (95% after 6 to 8 mo), seedling shoot growth was very slow (x̄= 0.5 cm/100 d), suggesting that survivorship eventually may decline. Recurrent fires often impede forest succession in degraded tropical grasslands; however, even with fire exclusion, our study suggests that forest succession can be very slow, even in close proximity to forest.
Post‐Establishment Seedling Success in the Brazilian Cerrado: A Comparison of Savanna and Forest Species1
Authors: Hoffmann William A. 
Published: March 2006

ABSTRACTDue to frequent fire, low nutrient availability, and prolonged drought, tropical savanna is a stressful environment for the survival and growth of woody plant seedlings. To understand why forest species do not succeed in this environment while savanna species are able to persist, the effects of fire and woody cover on seedlings of these two functional groups were investigated in the Brazilian Cerrado. Seedlings were established in experimental plots under three densities of woody cover, in sites protected from fire and sites to be subjected to fire. There was a clear difference in the ability of savanna and forest species to survive fire. None of the three forest species were able to survive fire during the first two years of life, whereas eight of the nine savanna species were able to resprout following fire. The small seed size of the ninth savanna species, Miconia albicans, predisposed its seedlings to be sensitive to fire, because there was a strong positive correlation between seed size and survivorship. Savanna species were less dependent on woody cover than were forest species, which exhibited higher growth and survival under tree canopies than in open grassland. The low rates of establishment and survival of forest trees in savanna, combined with high sensitivity to fire, appear sufficient to prevent the expansion of forest into savanna under current fire regimes in the Cerrado.
Plant Phenology in a Cloud Forest on the Island of Maui, Hawaii1
Authors: Berlin Kim E. , Pratt Thane K. , Simon John C. , Kowalsky James R. , Hatfield Jeff S. 
Published: March 2006

ABSTRACTWe recorded the times of flowering, fruiting, and leafing for ten native canopy and subcanopy trees and shrubs (monthly from December 1994 through December 1997) in a montane cloud forest with relatively aseasonal rainfall on the island of Maui, Hawaii. These species represented the great majority of individual woody plants at the site. Flowers and fruits were available in the community year–round; however, all species exhibited annual patterns of flowering, and four species showed annual patterns of fruiting while the rest fruited in supra–annual patterns. Many species had protracted flowering or fruiting peaks, and some bore small numbers of flowers or fruit year‐round. Most species flowered in a monthly peak mainly between May and August, corresponding to the period of greatest solar irradiance and marginally higher temperatures. Fruit ripening followed at varying intervals. In contrast, the heaviest flowering occurred between November and March, resulting from bloom of the dominant tree, Metrosideros polymorpha. At the highest elevations, Metrosideros flowering was heaviest during September, but peak flowering of lower elevation trees occurred in late fall and winter. Two forms of this species differed in their temporal and spatial patterns of flowering. For M. polymorpha var. polymorpha and var. incana, bloom peaked annually between November and January; however, for M. polymorpha var. glaberrima, flowering peaked from April through July, with an earlier secondary peak in January.
The Effects of Primates and Squirrels on Seed Survival of a Canopy Tree, Afzelia quanzensis, in Arabuko‐Sokoke Forest, Kenya1
Authors: Gathua Mwangi 
Published: March 2006

ABSTRACTI examined the fate of seeds from ten focal trees of Afzelia quanzensis (Leguminosae), a canopy tree in the Arabuko‐Sokoke, Kenya. The study was conducted for one fruiting season, between August 1990 and July 1991. Yellow baboons (Papio cynocephalus), Syke's monkeys (Cercopithecus albogularis), sun squirrels (Heliosciurus rufobrachium), and bush squirrels (Paraxerus palliatus) were all observed to interact with A. quanzensis seeds at various stages of pod development. Baboons and squirrels consumed high percentages of seeds when they were still immature, but the seeds were still unavailable to Syke's monkeys at this stage. Baboons bit open the hard green pods and squirrels gnawed through the pods to extract the immature seeds (hereafter referred to as seed predation), but monkeys were unable to open the pods. Upon maturity, the pods opened slightly, revealing red arils that were sought by baboons, monkeys, and squirrels. Monkeys removed the highest percentage of mature seeds from these pods. These mammal dispersers ate the arils from the mature seeds and discarded the viable part that germinates (hereafter referred to as seed dispersal). My data indicate that baboons and squirrels are seed predators while monkeys are seed dispersers of A. quanzensis.
Effects of Shade‐Tree Species and Crop Structure on the Winter Arthropod and Bird Communities in a Jamaican Shade Coffee Plantation1
Authors: Johnson Matthew D. 
Published: March 2006

ABSTRACTI examined the effects of two farm management variables, shade‐tree species and crop structure, on the winter (dry season) arthropod and bird communities in a Jamaican shade coffee plantation. Birds and canopy arthropods were more abundant in areas of the plantation shaded by the tree Inga vera than by Pseudalbizia berteroana. The abundance of arthropods (potential pests) on the coffee crop, however, was unaffected by shade‐tree species. Canopy arthropods, particularly psyllids (Homoptera), were especially abundant on Inga in late winter, when it was producing new leaves and nectar‐rich flowers. Insectivorous and nectarivorous birds showed the strongest response to Inga; thus the concentration of birds in Inga may be a response to abundant food. Coffee‐tree arthropod abundance was much lower than in the shade trees and was affected little by farm management variables, although arthropods tended to be more abundant in dense (unpruned) than open (recently pruned) areas of the plantation. Perhaps in response, leaf‐gleaning insectivorous birds were more abundant in dense areas. These results underscore that although some shade coffee plantations may provide habitat for arthropod and bird communities, differences in farm management practices can significantly affect their abundances. Furthermore, this study provides evidence suggesting that bird communities in coffee respond to spatial variation in arthropod availability. I conclude that /. vera is a better shade tree than P. berteroana, but a choice in crop structures is less clear due to changing effects of prune management over time.
Efectos de la Extracción de Maderas sobre la Diversidad de Mamiferos Pequeños en Bosques de Tierras Bajas de la Guayana Venezolana1
Authors: José Ochoa G. 
Published: March 2006

RESUMENSe evaluaron las respuestas de comunídades de mamiferos pequeños ante los efectos del aprovechamiento de maderas en bosques de tierras bajas de la Guayana Venaolana (Reserva Forestal Imataca). El estudio se basó en el análisis comparativo de las especies presentes en bosques primarios y en sectores afectados por la extracción selectiva de árboles. Los grupos taxonómicos evaluados heron Didelphimorphia, Chiroptera y Rodentia (familias Sciuridae, Muridae y Echimyidae). Para el inventario de especies se utilizaron los siguientes métodos: (1) mallas de neblina; (2)trampas en cuadrículas de 2,4 ha (con 120 puntos de trampeo cada una: 60 terrestres y 60 en estructuras arbóeas); y (3) observaciones mediante recorridos diurnos y nocturnos. El eshem de muestreo totalizó, 1904horas‐malla, 10.320 trampas‐noche y 567horas de observación. Al menos 83 especies conformaron las comunidades de mamíferos pequeños presentes en el área de estudio; de ellas, 15,3 por ciento heron registradas únicamente en bosques primarios. Chiroptera h e el orden más diverso (74,7%de las especies). En bosques explotados, las comunidades se caracterizaron por: (1) incremento en la abundancia de individuos; (2) menor proporción de murciélagos carnívoros e insectivoros del follaje; (3) mayor abundancia relativa de murciélagos frugívoros asociados con elernentos vegetales típicos de estadios serales tempranos; (4) incremento en las frecuencias de apariciopAn de murciélagos insectívoros de welo libre (Molossidae) en los estratos inferiores del bosque; (5) simplificación en la estructura trófica de la fracción comunitaria constituida por especies no voladoras, con el predominio de 10s depredadores‐omnivoros/semiarborícolas, seguidos por los frugívoros‐omnivoros/terrestres; y (6) disminución en las abundancias relativas de especies arboricolas dependientes del dosel. Estos resultados son explicados por: (1) la reducción en la disponibilidad de recursos claves asociados con la condición primaria del bosque (. e.g, refugios en troncos huecos de árboles maduros, frutos del dosel y estratos de movilidad); (2) el incremento en las abundancias relativas de renglones alimentarios como invertebrados del suelo y plantas saprófitas, principalmente en aquellos sectores donde la producción primaria está limitada por la presencia de suelos con una baja fertilidad (3)una mayor oportunidad de refugios en el estrato inferior del bosque, principalmente en oquedades formadas entre troncos caidos; (4) la modificacón de los patrones microclimáticos del sotobosque, como consecuencia de una mayor incidencia de luz al ser disminuida la cobertura arbórea; y (5) el aumento en las densidades de plantas pertenecientes a las primeras fases de sucesión. Se discuten las implicaciones de estos aspectos para la conservación de la diversidad biológica en áreas de la Guayana Venezolana destinadas a la producción industrial de maderas.
Aerobic Heterotrophic Bacterial and Fungal Communities in the Topsoil of Omo Biosphere Reserve in Southwestern Nigeria1
Authors: Okoh A. I. , Babalola G. O. , Olaniran A. O. 
Published: March 2006

ABSTRACTAs a part of the surveillance effort to monitor the ecological status of Omo Biosphere Reserve in the southwestern region of Nigeria, the aerobic heterotrophic bacterial and fungal communities of the topsoil were investigated in March 1995 and April 1996, before the onset of the rainy season. Four distinct wood‐tree plantations, a core strict nature reserve (SNR) area, and a buffer zone were sampled. The topsoil samples (7.5 cm depth), including the litter, were taken with an auger (8 cm diameter) and transported to the laboratory in polyethylene bags. One‐gram dry weight equivalent of sample was suspended in 10 ml sterile water, and serial dilutions from it were used for the estimation of bacterial and fungal densities. The bacterial and fungal densities ranged in the order of 106 and 103 cfu/g, respectively. Out of the 18 bacterial and 16 fungal species that were obtained, 13 and 12, respectively, were isolated from the core SNR. About 46 to 69 percent of the bacteria and 50 to 83 percent of the fungi species found in the SNR were absent in different combinations in the plantations and the buffer zone; these variations were significant among the sites monitored. The bacterial and fungal species compositions were significantly different between the SNR and each of the other sites. Proportional distributions within the sites were significant only for the bacterial communities. It would appear that plantation and human activities have caused significant changes in the distribution and species richness of the heterotrophic bacterial and fungal communities relative to the undisturbed SNR area of the Omo Biosphere Reserve.
Genetic Diversity of a Tropical Tree Species, Shorea leprosula Miq. (Dipterocarpaceae), in Malaysia: Implications for Conservation of Genetic Resources and Tree Improvement1
Authors: Lee S. L. , Wickneswari R. , Mahani M. C. , Zakri A. H. 
Published: March 2006

ABSTRACTGenetic diversity and population genetic structure of Shorea leprosula was investigated using seven natural populations distributed throughout Peninsular Malaysia and one natural population from Borneo. The mean population and species level genetic diversity were exceptionally high (He= 0.369 ± 0.025 and 0.406 ± 0.070, respectively). Heterozygosity varied among populations, ranging from 0.326 to 0.400, with the highest values found in the populations from central Peninsular Malaysia. Correlations among ecological factors (longitude, latitude, and annual rainfall) were not significant (P > 0.05), indicating that these ecological variables were not responsible for the observed genetic differences among populations. The Bangi adult population exhibited a higher level of observed heterozygosity but lower fixation indices in comparison to its seedling population. All other seedling populations also showed positive fixation indices (f), indicating a general excess of homozygotes. This also may suggest selection against homozygotes between the seedling and adult stages. A low level of population differentiation was detected (GST= 0.117 with the Lambir population and GST= 0.085 without the Lambir population). Furthermore, gene flow (Nm) between populations was not significantly correlated with geographical distances for the populations within Peninsular Malaysia. Cluster analysis also did not reflect geographical proximity and gave little insight into the genetic relatedness of the populations. This may indicate that the populations sampled are part of a continuous population with fragmentation having occurred in the recent past.
Population Structure and Growth Patterns of Opuntia echios var. gigantea along an Elevational Gradient in the Galípagos Islands1
Authors: Hicks David J. , Mauchamp Andre 
Published: March 2006

ABSTRACTCacti growing in forests potentially experience growth limitation due to reduced light availability. To test this hypothesis, we studied the population structure of Opuntia echios var. gigantea at 15 sites on the south side of Isla Santa Cruz, Galípagos Islands, Ecuador. Populations were located in communities ranging from arid scrub at low elevations to closed‐canopy tropical dry forest at higher elevations. Ordination confirmed the existence of a strong elevation‐vegetation gradient. Opuntia abundance peaked at lower elevations (ca 30 m), with lower densities in closed‐canopy sites. For populations in scrub vegetation, density declined fairly regularly with plant height. Populations in forested sites had few plants of intermediate height, suggesting periodic recruitment. Scrub populations had random dispersion, while those in forests were aggregated. The change in spatial pattern may be related to a change in primary reproductive mode from asexual propagation via fallen fruits to propagation via fallen cladodes. Height was significantly correlated with stem diameter. Intercepts of these relationships increased toward higher elevations, probably in response to the increasing height of the surrounding canopy.