bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence for Effective Seed Dispersal by the Sulawesi Red‐Knobbed Hornbill, Aceros cassidix1
Authors: Kinnaird Margaret F.
Published: March 2006

The Sulawesi red‐knobbed hornbill (Aceros cassidix) is a large‐bodied, frugivorous bird that nests in high densities in the Tangkoko‐DuaSudara Nature Reserve, North Sulawesi, Indonesia. I measured seedling abundance and species richness, diversity, and dominance in plots placed below and immediately behind 20 active nest sites to evaluate the role of red‐knobbed hornbills as agents of seed dispersal. Comparisons of treatment (below nests) and control plots (behind nests) show that hornbills affect the abundance and distribution of diet‐species seedlings. Nondiet and nest tree seedlings did not differ between control and treatment plots suggesting that differences in diet species were the result of additional input by hornbills rather than by random or other dispersal events. Significantly greater numbers of diet seedlings germinated below nests, and the diversity of diet species was greater than that of nondiet species. Dominance of a few species in the treatment plots is consistent with the hypothesis that hornbills are effectively dispersing seeds of some, but not all, of their diet species. Although seedlings under nests may eventually experience density‐dependent mortality, seedlings survived at least 12 months, indicating that red‐knobbed hornbills were effectively dispersing seeds and influencing the initial fate of seeds of several tropical forest tree species.
Predatory Mites in Tropical Australia: Local Species Richness complementarity1
Authors: Walter David Evans , Proctor Heather C.
Published: March 2006

Although little supporting data is available, mites (Acari) are often considered to be one of the ‘hyperdiverse’ taxa in tropical ecosystems. To test this assumption, we sampled single guilds of predatory mites (Hydracarina and Mesostigmata) in three different habitats (fresh water, rotting fungi, and forest foliage) across a range of sites in monsoonal, wet‐tropical, and subtropical Australia. Most species (61%) were collected at a single site; as a result, all seven collector's curves rose steeply with little indication of reaching asymptotes. Regional faunas ranged from 87–94 percent distinct and of the 247 species identified, 114 (46%) were previously unknown in Australia and appear to be new. Even within taxonomically well‐studied groups, such as the Hydracarina and Phytoseiidae, we found many new species (32% and 60%, respectively). Our results suggest that the diversity of tropical mites is very high and comparable to that of many insect taxa.

We propose a simple model to explain our results, i.e. that in the tropics, high levels of complementarity between sites amplify local mite species richness. We tested this model by additional sampling, comparing within‐site to between‐site complementarity, and contrasting temperate with tropical foliar Mesostigmata. As predicted by the model, collecting at new sites continued to accumulate new species, complementarity was significantly greater between‐sites than within‐sites (72 vs. 25%), and temperate collections were more homogeneous and less diverse than tropical collections.
Fire as a Recurrent Event in Tropical Forests of the Eastern Amazon: Effects on Forest Structure, Biomass, and Species Composition1
Authors: Cochrane Mark A. , Schulze Mark D.
Published: March 2006

The effects of fire on forest structure and composition were studied in a severely fire‐impacted landscape in the eastern Amazon. Extensive sampling of area forests was used to compare structure and compositional differences between burned and unburned forest stands.

Burned forests were extremely heterogeneous, with substantial variation in forest structure and fire damage recorded over distances of <50 m. Unburned forest patches occurred within burned areas, but accounted for only six percent of the sample area. Canopy cover, living biomass, and living adult stem densities decreased with increasing fire inrensiry / frequency, and were as low as 10–30 percent of unburned forest values. Even light burns removed >70 percent of the sapling and vine populations. Pioneer abundance increased dramatically with burn intensity, with pioneers dominating the understory in severely damaged areas. Species richness was inversely related to burn severity, but no clear pattern of species selection was observed.

Fire appears to be a cyclical event in the study region: <30 percent of the burned forest sample had been subjected to only one burn. Based on estimated solar radiation intensities, burning substantially increases fire susceptibility of forests. At least 50 percent of the total area of all burned forests is predicted to become flammable within 16 rainless days, as opposed to only 4 percent of the unburned forest. In heavily burned forest subjected to recurrent fires, 95 percent of the area is predicted to become flammable in <9 rain‐free days. As a recurrent disturbance phenomenon, fire shows unparalleled potential to impoverish and alter the forests of the eastern Amazon.
Edge Structure Determines the Magnitude of Changes in Microclimate and Vegetation Structure in Tropical Forest Fragments1
Authors: Didham Raphael K. , Lawton John H.
Published: March 2006

Edge structure is one of the principal determinants of the extent and magnitude of edge effects in forest fragments. In central Amazonia, natural succession at forest edges typically produces a dense wall of vegetation dominated by Cecropia spp. that buffers the forest interior. Fire encroachment into forest edges, however, eliminates the soil seed bank, enhances plant mortality, and promotes succession to an open, Vismia–dominated edge that does not buffer the forest interior. Contrasting open, fire–encroached forest edges and closed, non–fire–encroached edges were examined in central Amazonia to assess the effects of edge structure on microclimate and vegetation structure in tropical forest fragments. Edge penetration distances for most microclimate and vegetation structure variables were as much as two to five times greater at open edges than at closed edges. The magnitude of these differences suggests that edge structure is one of the main determinants of microclimate and vegetation structure within tropical forest fragments.

Edge effects also varied systematically with fragment area. For a given edge type, 100–ha fragments had consistently lower canopy height, higher foliage density, higher temperature, a higher rate of evaporative drying, lower leaf litter moisture content, and lower litter depth than continuous forest, at all distances from the forest edge. These differences, however, were relatively minor compared to the striking differences in edge penetration between open and closed forest edges. For organisms in small fragments, the difference between open and closed edges may be the difference between total edge encroachment on one hand and an effective nature reserve on the other, relatively independent of absolute fragment area.
Deforestation Rates (1938–1988) of Tropical Lowland Forests on the Andean Foothills of Colombia1
Authors: Viña Andrés , Cavelier Jaime
Published: March 2006

Deforestation rates were estimated in 270 km2 of lowland moist forest on the eastern slope of the Colombian Andes (300–800 m). Deforestation was quantified by determining areas of pasture, secondary growth, and forest in aerial photographs (1:19,000–1:60,000) taken in the 1930s, 1950s, 1960s, 1970s, and 1980s. Mean annual deforestation rate for the 1938–1988 period was 1.5 percent, and ranged from <0.1 percent (1938–1955) to 4.4 percent (1970s–1980s). Between the 1930s and the 1980s, areas covered by pasture and young secondary forest increased from 26–53 percent and from 2–14 percent, respectively. This suggests that, although there are areas with clear signs of forest regeneration, the overall trend is the conversion of mature tropical forests to pastures for cattle ranching.
Ecologia, Producción y Aprovechamiento del Mangle Conocarpus erectus L., en Barra de Tecoanapa Guerrero, México1
Authors: Hernández Cristian Tovilla , Espino Guadalupe de la Lanza
Published: March 2006

Biological aspects of the development of the buttonwood mangrove, Conocarpus erectus L., from Barra de Tecoanapa, Guerrero, México are described. Litterfall, flowers and seed production, leaf turnover, decomposition of leaves, and the optimal use of this species by the local community are quantified. Conocarpus erectus produces mean litterfall of 2.6 g/m2/d, increasing (>20%) during the wet season. This is comparable to production recorded for other mangrove species of the Pacific and Caribbean. Flowering and fruiting are continuous but seed viability is (<12%). This is more critical during the dry season when <5 percent of seed germinates and only 1.6 percent of seedlings survive to form flowers after 25–28 mo. Leaf development is rapid for the first 64 days, with completion in 136 + 9 days, giving an annual leaf turnover >2.6. High leaf cellulose and lignin content results in a slow decomposition rate (up to 284 d). Organic matter content in green leaves is greater (95%) than in yellow leaves (85%). The local people exploit the forest selectively using three species of tree, of which C. erectus and Laguncularia racemosa are most used. Buttonwood mangrove wood is used in house construction, fencing, and for firewood. Exploitation has altered gravely areas near occupation, creating clearings that will not recover easily. Some recommendations for the recuperation of these areas are presented, including proposals for more rational exploitation of this wetlands resource.
Fruiting Phenology and the Conservation of the Great Pied Hornbill (Buceros bicornis) in the Western Ghats of Southern India1
Authors: Kannan Ragupathy , James Douglas A.
Published: March 2006

The phenology of principal fruits consumed by the endangered Great Pied Hornbill (Buceros bicornis) was monitored for two years in a wet forest habitat in southern India. Lipid–rich fruits, produced by several interior forest trees mainly of the family Lauraceae, were highly seasonal in their availability, and their production in the dry, hot season coincided with the breeding of the hornbill. Sugary fruits, produced mainly by several species of Ficus, were available year–round due to aseasonal fruiting patterns. Because Ficus fruited even at times of low fruit resource availability, and was heavily utilized by hornbills and other frugivores, it played a keystone role in the maintenance of the avian frugivore community. Overall fruit production was scarce between July and January during the southwest and northeast monsoon seasons. Vitex altissima produced berries abundantly during much of this time (September–December) and thus was another important fruit resource for avian frugivores. To safeguard the fruit resource base for the Great Pied Hornbill, we recommend: (1) The protection of Ficus and Vitex trees from overexploitation, and (2) the conservation of forest integrity to maintain compositions and densities of the lipid–rich fruit tree species utilized by the hornbill.
Factors Related to the Recovery of Subalpine Woodland on Mauna Kea, Hawaii1
Authors: Hess Steven C. , Banko Paul C. , Brenner Gregory J. , Jacobi James D.
Published: March 2006

We measured mature tree and sapling density, tree associations, crown size, age structure, recovery from ungulate browsing, and grass cover at four study sites in two types of subalpine woodland on Mauna Kea volcano, island of Hawaii. Beginning in 1981, introduced ungulates were reduced in number to allow regeneration of Sophora chrysophylla (mamane) in habitat supporting the endangered Hawaiian finch, Loxioides bailleui (palila). We found Sophora regeneration at all four study sites, but regeneration was higher in mixed species woodland with codominant Myoporum sandwicense (naio) than in areas where Sophora dominated. Regeneration of Myoporum was uniformly very low in comparison. Invasive grass cover, which suppresses Sophora germination, was highest in mid‐elevation woodland where Sophora dominated. The distribution of mature and sapling Sophora were both related to study site, reflecting previous ungulate browsing and uneven recovery due to grasses. Densities of Sophora snags were not different among any of the sites, suggesting a more even distribution in the past. Selective browsing before ungulate reduction may have favored Myoporum over Sophora, leading to high densities of mature Myoporum in codominant woodland. After ungulate reduction, however, we found no pattern of competitive inhibition by Myoporum on regeneration of Sophora. Reduction of Myoporum is not likely to enhance habitat for Loxioides as much as supplemental plantings of Sophora, glass control, and continued ungulate eradication. Mid‐elevation Sophora woodland areas, where Loxioides forage and nest in high densities, would benefit the most from these management actions.
Isolated Pasture Trees and the Vegetation under their Canopies in the Chiapas Coastal Plain, Mexico1
Authors: Otero‐Arnaiz Adrians , Castillo Silvia , Weave Jorge , Ibarra‐Manríquez Guillermo
Published: March 2006

The Coastal Plain of Chiapas (southern Mexico) was formerly covered by large tracts of subhumid tropical forests but is heavily deforested at present. In this region, 15 pastures were selected to characterize species composition of isolated trees, as well as to describe species composition, growth form patterns, and patterns of dispersal units in the vegetation growing under their canopies. The 65 recorded pasture trees belonged to 20 species and 11 families, of which Fabaceae and Moraceae were the most species‐rich. Coccoloba barbadensis (Polygonaceae) and Enterolobium cyclocarpum (Fabaceae) were the most abundant and frequent trees in the studied pastures. More than half (55%) of isolated tree species were fleshy‐fruited. In the vegetation sampled under pasture trees, 134 species and 45 families were found. Fabaceae and Poaceae had the largest numbers of species. Herbs were the predominant growth form (46.3%), followed by shrubs (23.9%), trees (23.1%), and lianas (2.2%); 6 species could nor be placed in any growth form category. Most species of this flora were fleshy‐fruited (43.3%), followed by heavy, gravity‐dispersed fruits (17.9%). The analysis of dispersal units by growth form category confirmed the prevalence of fleshy fruits, although their predominance was not so obvious among herb species. Almost half (49.2%) of the flora under pasture trees was typical of secondary vegetation; this pattern was true for herbs but not for most woody species, which were typical of primary vegetation. A numeric classification of the vegetation samples taken under pasture trees produced eight floristic groups, all of which were independent of the specific identity of pasture trees. No significant effect of dispersal unit type of pasture tree on the characteristics of the vegetation growing under them was found. Future attempts to re‐create the original forest cover using isolated trees in pastures as regeneration foci should pay more attention to the maintenance of a large specific diversity independently of the dispersal types among these components of tropical landscapes.
A Nectar Reward: Is More Better?1
Authors: Salguero‐Faría José A. , Ackerman James D.
Published: March 2006

Characters involved in pollinator attraction are likely maintained by selection. Plants that invest more in floral displays and/or rewards are expected to attract more pollinators than those that do not. A large number of plants, however, are severely pollen‐limited yet either produce small rewards or none at all. The orchid, Comparettia falcata, is a pollinator‐dependent, self‐compatible epiphyte distributed throughout the Greater Antilles, Central and South America. In Puerto Rico where it is pollinated by the hummingbird Chlorostilbon maugaeus, C. falcata presents a smaller nectar reward than most other plants pollinated by the same species. To determine whether or not selection would favor the production of higher nectar levels, we enhanced the quantity of nectar offered by flowers in a Puerto Rican population for two flowering seasons. We monitored visitation frequencies, pollen movement, and reproductive success at three sites with different canopy coverages. Daily censuses of hummingbirds provided estimates of relative pollinator abundance. A multiway contingency test employing Walďs statistic showed no overall differences in reproductive success between plants with enhanced rewards and unmanipulated controls. Site differences, however, were clear. Plants of the mid‐ and high‐light sites had greater success than those of the low‐light site, and the differences were usually at least two‐fold. There was a significant site‐treatment interaction in reproductive success that could be attributed to the overall trend whereby controls of both mid‐ and high‐light sites did better than the nectar‐enhanced plants. Most of the observed pollinations (85%) with stained pollinia resulted in self‐pollinations that did not differ among treatments. Seed crops from self‐ and cross‐pollinations revealed no differences in the number of viable seeds. Because we found little evidence of selection for increasing nectar reward via inbreeding depression or male and female reproductive success, and previous studies have indicated that meager natural levels of reward are better than none at all, we suspect that reward production in C. falcata may be driven by a combination of pollination‐limitation and resource constraints.
Does Optimal Packing of Flowers in Syconia Shape Style Length Variation in Monoecious Figs?1
Authors: Ganeshaiah K. N. , Kathuria Prarthana , Shaanker R. Uma
Published: March 2006

Style length variation in female flowers of monoecious figs has been shown to play an important role in regulating the proportion of flowers that develop into seeds and those that become infested by the pollinator wasp. In this study, we tested the suggestion that style length variation in figs is a consequence of optimal packing of the flowers. We show that optimal packing of flowers in fig syconia will result in a highly skewed distribution of style lengths and a positive skewness of pedicel lengths. These predictions were qualitatively tested in eight species of figs and the results indicate that observed style length distributions did not conform to those expected. We argue that while the pedicel lengths are likely to be a spinoff of optimal packing of the flowers, style lengths are probably shaped by independent selective fotces. The pedicel lengths also are subjected to compensatory growth so as to place the stigmas at a common height in the central cavity for effective pollination of the flowers. This was substantiated by the response (dependence) of pedicels to (on) the length of the style, neck, and other floral features. In all species the coefficient of variation of styles was very consistent (ca 30 %). This is in accordance with expectations if style lengths are shaped to regulate the proportion of flowers for wasp and seed production.
Nodding Capitula in Superpáramo Asteraceae: An Adaptation to Unpredictable Environment1
Authors: Sklenár Petr
Published: March 2006

Nodding capitula are a striking feature in several Asteraceae species of the Andean superpáramo. In this study, the thermal environment of the nodding inflorescence in Culcitium canescens Humb. & Bonpl. was surveyed by a short‐term microclimatic measurement. Temperatures of the nodding inflorescences were higher than temperatures of the surrounding air during the day, while the respective temperatures were comparable during the night. Also, compared to other parts of the plant, the nodding inflorescence provided favorable temperature conditions. An experiment showed that the radiation reflected from the substratum explained most of the variability in the inflorescence temperature. It is suggested that the nodding capitula have evolved to protect the flowers from snow and rain while at the same time ensuring sufficient temperatures for floral development.
Population Structure and Life Cycle of Borassus aethiopum Mart.: Evidence of Early Senescence in a Palm Tree1
Authors: Barot Sébastien , Gignoux Jacques
Published: March 2006

As with other plants having a relatively simple morphology, solitary palms are useful biological models for studying the life histories of long‐lived plants. In the first study to investigate the life history ofBorassus aethiopum, a widespread dioecious palm growing in African savannas, we found that: (1) the number of leaves increased up to reproductive maturity and then decreased during the reproductive period, while height increased throughout life; (2) female fecundity, measured as the number of seedlings within a few meters under the female canopies, decreased markedly in old individuals with few leaves; and (3) height distribution was strongly bimodal. This bimodality was due to variations in the stem elongation rate during the life of the palm and the accumulation of adults with low mortality rates in the taller height classes. The observed pattern of fecundity and number of leaves in relation to height clearly suggests a senescence period that began just after sexual maturity and appeared to be protracted. Comparisons between the life history ofB. aethiopumand the life histories of some forest palms showed that environmental conditions cannot in themselves explain the various palm life histories.
Plant and Litter Influences on Earthworm Abundance and Community Structure in a Tropical Wet Forest1
Authors: Gonzalez Grizelle , Zou Xiaoming
Published: March 2006

Plant communities differ in species composition and litter input. To examine the influence of plant species on the abundance and community structure of soil fauna, we sampled earthworms in areas close to and away from the bases ofDacryodes excelsaandHeliconia caribaea, two distinct plant communities within a tropical wet forest in Puerto Rico. We also carried out a litter manipulation experiment to examine the short–term responses of earthworms to litter removal and litter addition treatments. We found that: (1) the density and biomass of both soil–feeding endogeic and litter‐feeding anccic worms did not differ between areas close to and away fromDacryodeftrees (in contrast, the density and biomass of anecic worms was higher in areas away fromHeliconiaplants despite the lack of differences for endogeic worms); and (2) total dry weight of earthworms tended to be higher in the litter addition treatment than in the control within theHeliconiacommunity. Our results suggest thatHeliconia caribaeahas a strong negative influence on anecic earthworms and that earthworms in theHeliconiacommunity are more sensitive to litter input than in theDacryodescommunity.
Distribución, Abundancia y Reproducción de Harengula jaguana Goode y Bean, 1879, en la Plataforma Continental del Sur del Golfo de México (Pisces: Clupeidae)1
Authors: García‐Abad M. C. , Tapia‐García M. , Yáñez‐Arancibia A. , Sánchez‐Gill P.
Published: March 2006

Harengula jaguana is a dominant species in the southern Gulf of Mexico. It is a demersal, estuarine‐dependent species, distributed throughout the Campeche Sound area (12‐54 m). It is found in areas influenced by coastal discharges. The size at first maturity of females is 117 mm total length. Reproduction occurs from February to October in depths 18‐36 m. The juveniles are found on the shelf (<20 m) and inside the Terminos Lagoon. Recruitment is in two distinct periods, March–June and August–November, when adults and juveniles migrate to the outer shelf. Greatest abundance is observed in depths of 12‐36 m. The biology and ecology of H. jaguana was analyzed in the Campeche Sound to better understand the structure and function of the demersal fish communities. It is a very important species in the trophic dynamics of the ecosystem because it transports matter and energy. A model of the biological pattern for this species in the area is proposed.
Ecology of Foliicolous Lichens at the “Botarrama” Trail (Costa Rica), a Neotropical Rain Forest. I. Species Composition and its Ecogeographical Implications1
Authors: Lücking Robert
Published: March 2006

A total of 217 species of typically foliicolous lichens were found at the “Botarrama” trail, a premontane rain forest in the Braulio Carrillo National Park, Costa Rica. The species composition confirmed the classification of this study sice as transitional between lowland wet and montane rain forest. In terms of species tichness, the foliicolous lichen flora was dominated by the families Gomphillaceae (Calenia, Echinoplaca, Gyalideopsis, andTricharia), Trichotheliaceae (PorinaandTricbothelium), and Pilocarpaceae (ByssolomaandFellhanera). The most frequent species werePorina mirabilis(including its supposed anamorphPhyllophiale alba),Gyalectidium filicinum, Porina rufula, andStrigula platypoda.A large proportion of the species was rare. Frequency distributions based on area cover corresponded well to general community models by closely fitting a log‐normal approximation. Half of the species had narrow ecological amplitudes while more than 70 percent exhibited a wide geographical distribution, thus making che study site representative of a Neotropical rain forest. The use of foliicolous lichens as indicators of altitudinal zonation is discussed.
Responses of Tropical Understory Plants to a Severe Drought: Tolerance and Avoidance of Water Stress1
Authors: Tobin Michael F. , Lopez Omar R. , Kursar Thomas A.
Published: March 2006

Shade‐tolerant understory shrubs and subcanopy trees constitute most of the woody species in Neotropical moist forest, but studies demonstrating physiological differences among these species are few. Shade‐tolerant species that coexist in the forest understory exhibit differences in leaf life span that have been associated with variation in physiological traits. We hypothesized that water relations of understory species with widely divergent leaf life spans differ in response to drought. Although severe drought is infrequent in Neotropical moist forest, we studied the water relations of shade‐tolerant understory species with short or long leaf life spans during the severe 1991‐1992 dry season on Barro Colorado Island, Panama. The predawn leaf water potential declined to ‐2.8 and ‐3.6 MPa during the dry season inHybanthus prunifoliusandPsychotria horizontalis, respectively, two species with short leaf life spans, but remained above ‐1.3 MPa in two species with long leaf life spans,Swartzia simplexandOuratea lucens. The midday leaf water potential dropped as low as ‐3.4 and ‐4.5 MPa forH. prunifoliusandP. horizontalis, respectively. The osmotic potential ofH. prunifoliusandP. horizontalisand another species with short leaf life span,Alms blackiana, decreased early in the dry season, a period during which all three had substantially negative predawn water potential. In contrast, the osmotic potential ofS. Simplex, O. lucens, andLicania platypus, a third species with long leaf life span, declined late in the dry season, even though we observed little change in predawn water potential forS. simplexandO. lucens. We conclude that the variable and potentially severe dry season in Neotropical moist forest can be sufficiently intense to severely limit soil moisture availability for understory plants.H. prunifoliusandP. horizontalistolerated dehydration, whereasS. simplexandO. lucenspostponed dehydration.
Litter Cover Variability Affects Seedling Performance and Herbivory1
Authors: Benitez‐Malvido Julieta , Kossmann‐Ferraz Isolde D.
Published: March 2006

We assessed the effects of litter cover on herbivory and performance (annual survival and relative growth rate in height and leaf number) for established seedlings (≥9 cm tall, and ≥4 mo old), of four shade‐tolerant, large‐seeded, co‐occurring Sapotaceae species. Seedlings were divided into three litter treatments: (1) litter addition, (2) control, and (3) continuous litter removal. The mean survival for all treatments in descending order were:Chrysophyllum pomiferum(89%),Pouteria pemviemis(84%),P. caimito(75%), andMicropholis venulosa(40%). For all variables, species differed significantly within litter treatments. InM. venulosa, survival and relative growth rate in leaf number significantly decreased with the removal of litter, whereas herbivory increased. Relative growth rate in height ofP. peruviensisdecreased significantly with litter removal, while the levels of herbivory were higher with the addition of litter. Conversely, litter quantity had no effect on the performance ofC. pomiferum, but herbivory was lower in the removal treatment. Finally, inP. caimito, litter treatment did not affect performance or herbivory. Results suggest that differences in litter quantity differentially affect tree species with similar biology(i.e., large‐seeds, shade tolerance) in life stages other than germination and early establishment. The variability in species' responses to litter might be an important factor in determining species richness, abundance, and distribution of tropical rain forest tree species at the seedling level.
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

Interspecific 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

During 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

Two 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

The 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

Forest 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

Due 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

We 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

I 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

I 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

Se 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.