bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

ABSTRACTEdge 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

ABSTRACTDeforestation 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

ABSTRACTBiological 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

ABSTRACTThe 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

ABSTRACTWe 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

ABSTRACTThe 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

ABSTRACTCharacters 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

ABSTRACTStyle 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

ABSTRACTNodding 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

ABSTRACTAs 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

ABSTRACTPlant 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

ABSTRACT 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

ABSTRACTA 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

ABSTRACTShade‐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

ABSTRACTWe 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.