bluuebunny/crossref_metadata_2025_split huggingface dataset:
Environmental Effects of Canopy Gap Formation in High‐Rainfall Mangrove Forests1
Authors: Ewel Katherine C. , Zheng Songfa , Pinzón Zuleika S. , Bourgeois John A. 
Published: March 2006

ABSTRACTThis study investigated the importance of gap formation in mangrove swamps on the island of Kosrae, Federated States of Micronesia, in order to understand better both natural processes of forest development and the effects of harvesting trees for firewood in these wetlands. Measurements were concentrated in seven plots located near four rivers: three in fringe zones and four in basin zones. Each plot was a cluster of five points and covered an area of ca 1.3 ha. From every point in each of the seven plots, the nearest canopy gap ≥10 m2 was located; 25 of the 35 gaps were formed by harvesting. Porewater salinity was significantly higher under the canopy in fringe mangrove forests than in basin mangrove forests. Although gaps were small (mean gap size = 158 m2; median gap size = 92 m2), soil temperatures were significantly higher in gaps of both zones. Soil redox potential was significantly lower and porewater salinity significantly higher in the gaps than under the canopy in the basin zone only. Higher porewater salinity may be attributed to high evaporation rates from the soil and high transpiration rates from trees surrounding gaps. There were significantly more seedlings in gaps than under the canopy only in the fringe zones. Although gap formation alters the soil environment of Kosraean mangrove swamps, high freshwater input may buffer these effects in basin mangrove swamps by reducing porewater salinity. Current harvesting rates do not appear to be changing canopy species composition, but large gaps, especially in mangrove forests in more arid areas, may lead to major changes.
Stand Biomass and Tree Mortality from Permanent Forest Plots on Krakatau, Indonesia, 1989–19951
Authors: Whittaker R. J. , Schmitt S. F. , Jones S. H. , Partomihardjo T. , Bush M. B. 
Published: March 2006

ABSTRACTForest closure on the three original Krakatau Islands (Panjang, Rakata, and Sertung) took place ca 1930, about 50 yr after the apparent sterilization of the islands due to volcanic eruptions. Two permanent forest plots were established on each of these islands in 1989. A full enumeration of these plots, of two additional Rakata plots, and of two “mainland”plots from the Ujung Kulon National Park, West Java, was undertaken in 1992. These data provide the first estimates of aboveground biomass from Krakatau. The values reported for Krakatau are below the local West Javan figures, with considerable variation occurring within the islands. In 1992, the fourth Krakatau island, Anak Krakatau, began an eruption sequence which continued through the study period, depositing ash on the study sites of Panjang and Sertung. A further partial survey of these plots in 1994–1995 revealed a significant increase in mortality since the volcanic activity recommenced, with an increase in deaths of larger stems. Although Rakata has not been influenced directly by volcanism, three sites surveyed on Rakata in 1994–1995 have experienced increased tree mortality, in two cases as a consequence of storm damage and in particular, of lightning strikes. Stand dynamics on Krakatau thus appear to be strongly influenced by episodic environmental disturbance with varying degrees of dependence on the volcanic activity of Anak Krakatau.
Seedling and Sprout Response to Slash‐and‐Burn Agriculture in a Tropical Deciduous Forest1
Authors: Miller P. M. , Kauffman J. B. 
Published: March 2006

ABSTRACTSurvival and growth of seedlings and sprouts were assessed in three plots for 16 mo following the slashing and burning of a tropical deciduous forest in Jalisco, Mexico. We encountered a total of 47 species: 21 seedling species and 35 sprout species. Calliandra formosa and Piptadenia flava were the most common seedling species; Bursera arborea, Cordia alliodora, and Piptadenia constricta were the most common sprouts. Colubrina triflora, Diphysa occidentalis, and Cnidoscolus spinosus had limited sprouting ability. Twenty‐six species were represented by one seedling or one sprout. Thirty‐eight percent of the seedlings were tree species, 59 percent were shrub species, and 2 percent were vines species. In contrast, 86 percent of the sprouts were from trees and 13 percent from shrubs. One year after the initial measurements, 29 percent of the seedlings and 13 percent of the sprouts were dead. Each of the seedling means (number of stems/individual, height and diameter of the tallest stem, and elliptical crown area) was significantly smaller (P < 0.05) than that of sprouts at all three measurement periods, but relative growth rates were similar. Total canopy area of seedlings had a larger relative increase than did the canopy area of sprouts. The presence of seedlings increased species diversity compared to calculated diversity excluding seedlings. Timing of fruit dispersal in relation to the date of burning and the high number of Leguminosae species in the forest appeared to favor seedling establishment for some species.
The Potential Impact of Small‐Scale Physical Disturbance on Seedlings in a Papuan Rainforest1
Authors: Mack Andrew L. 
Published: March 2006

ABSTRACTPhysical disturbance, such as falling debris, is an important cause of mortality to rain forest seedlings. I used artificial seedlings to quantify physical disturbance in a rain forest at the Crater Mountain Biological Research Station in Papua New Guinea. Single (N= 418) and clustered artificial seedlings (N= 428) were placed on eight transects spanning varied topography to assess the area's disturbance regime, to test if ground slope affected disturbance, and to test if clustering affected the incidence of damage.Two transects showed a significant departure from random in the spatial distribution of damaged seedlings within the transect, suggesting that some areas of experience more disturbance than others. Artificial seedlings on level ground experienced damage less often than artificial seedlings on slopes; disturbance increased with ground slope. Artificial seedlings in dry washes experienced the greatest probability of damage. Artificial seedlings in clusters experienced significantly less damage than single ones, suggesting clustered seedlings might be less vulnerable to damage than lone seedlings. The disturbance rate at this site (34.7% damaged in one year) was markedly lower than that measured at the La Selva Biological Reserve in Costa Rica (82.4%).
Sugar Composition of Nectars and Fruits Consumed by Birds and Bats in the Tropics and Subtropics1
Authors: Baker Herbert G. , Baker Irene , Hodges Scott A. 
Published: March 2006

ABSTRACTSeveral characteristics of flowers and fruits have been suggested as comprising syndromes of characters that indicate particular classes of pollinators and fruit dispersers. Common phylogenetic history among species, however, may also significantly influence these characters and obscure or enhance perceived patterns of plant syndromes. We analyzed the proportions of glucose, fructose, and sucrose by paper chromatography in the nectar and fruit juice of 525 tropical and subtropical plant species to test whether sugar chemistry was correlated with volant vertebrate pollinator or fruit disperser classes. Samples were taken from Old World and New World species and the calculations kept separate. Kruskal‐Wallis tests of family means showed significant deviations in the percent sucrose content among pollinatorl disperser classes. Mann‐WhitneyU‐tests showed significant differences among nectars of all pollinator classes but fruit juices differed only due to the high sucrose content of megachiropteran dispersed fruits. In addition, sign tests of samples occurring within families showed significant correlations between percentage sucrose content and pollinator/disperser classes. Passerine nectars had low sucrose content. In striking contrast, the nectar of hummingbird flowers had very high sucrose content. The Microchiroptera nectars showed hexose richness with a sucrose content somewhat greater than that of passerine flowers. Megachiroptera flowers showed sucrose‐rich nectars. The results for fruits were comparable to those for nectars. Passerine fruits were hexose dominated, microchiropteran fruits had a sucrose content similar to passerine fruits, and megachiropteran fruits were sucrose‐rich. We speculate on the evolutionary sequence of changes in nectar and fruit juice sugar composition and suggest that future investigations consider the chemistry of other food sources such as pollen and leaves. Only with these additions and other ecological studies can the full interplay of such plant‐animal interactions be anticipated.
The Assemblage of Birds Foraging in Native West Indian Pine (Pinus occidentalis) Forests of the Dominican Republic during the Nonbreeding Season1
Authors: Latta Steven C. , Wunderle Joseph M. 
Published: March 2006

ABSTRACTWe studied avian resource use in a native West Indian pine (Pinus occidentalis) forest in the Cordillera Central of the Dominican Republic during the nonbreeding season. The forest is characterized by a fairly open pine canopy and a dense mixed‐broadleaf and pine understory. We used a principal components analysis of 23 foraging characters for 23 bird species, including foraging height, the proportional use of 5 different foraging methods, 3 horizontal positions and foliage densities, and 11 foraging substrates. Five principal components accounted for 74 percent of the total variance of the assemblage variables and resulted in the delineation of at least 5 foraging guilds. 78 percent of bird species had mean foraging heights of 5.0–10.0 m, corresponding to the region of overlap of pine and broadleaf vegetation. As a result, the diversity of foraging substrates and maneuvers used by birds, rather than foraging height, appears to be the primary means by which birds that exploit this habitat separate ecologically. Migrant wood warblers (Parulinae) are probably able to integrate into the community because of little diet overlap between residents and migrants, and the fairly specialized nature of their largely insectivorous foraging habits. Avian foraging in this habitat may reflect the effects of frequent disturbance such as hurricanes.
The Influence of Temporal Changes in Fruit Availability on Diet Composition and Seed Handling in Blue Monkeys (Cercopithecus mitis doggetti)1
Authors: Kaplin B. A. , Munyaligoga V. , Moermond T. C. 
Published: March 2006

ABSTRACTWe investigated the relation between temporally varying resources, diet composition, and seed‐handling behaviors in a group of blue monkeys (Cercopithecus mitis doggetti) in a tropical montane forest of Rwanda. Changes in diet composition were related to concurrent phenological studies of fruit‐producing trees, and density and abundance of tree resources within the monkey's home range. Fruit composed nearly 50 percent of the diet. Over 50 percent of the fruits eaten had juicy fleshy pulp. Observations of seed handling behavior provided insights into the role of these animals as potential seed dispersal agents. The monkeys moved the seeds of 29 species out of parent canopies by defecating seeds intact and by potentially carrying seeds in cheek pouches and dropping them later. Seeds of 18 species were found intact in fecal piles. Our study showed community‐level phenology patterns did not indicate a decrease in fruit availability during the study period, but an analysis of the preferred fruits consumed by the monkeys showed distinct periods of low fruit availability. The study period included two dry seasons; only one of these produced a period of fruit scarcity for the animals. The animals employed different strategies during times of preferred fruit scarcity. They increased consumption of leaves and other fleshy fruits, and diet diversity increased, or became mainly seed predators and diet diversity decreased. The variable responses of these monkeys to changes in food availability highlights their dietary plasticity and imposes significant variations in their role as potential seed dispersers.
Local and Regional‐Scale Food Web Structure in Nepenthes alata Pitchers1
Authors: Sota T. , Mogi M. , Kato K. 
Published: March 2006

ABSTRACTTropicalNepenthespitcher plants provide small, isolated aquatic habitats. We examined inter‐pitcher variation in the community structure of the inhabitants ofNepenthes alataBlanco in West Sumatra, focusing on the conditions of the pitchers, bacterial density in the pitcher fluid, density and biomass of metazoan inhabitants, and the frequencies of interspecific encounters. Older pitchers contained more insect carcasses. The bacterial density increased with the age of the pitchers, but decreased in withered pitchers that contained finely decomposed detritus. In live pitchers, the bacterial density, the density, mass and species richness of metazoa, and the number of trophic levels per pitcher were positively correlated with detrital mass, which was correlated with volume of pitcher fluid. The metazoan fauna fromN. alataconsisted of 4 predators and 12 saprophages, among the richest known forNepenthesspecies. However, each individual pitcher harbored a limited numbers of species, owing to (1) the low incidence of many species, and (2) the aggregated distribution and different temporal colonization pattern of major species. Six dipteran taxa (one predator and five saprophages) accounted for the bulk of metazoan inhabitant biomass. Of 48 combinations of predator‐prey encountered, only four occurred frequently (in > 30% of pitchers), which included two predators and three saprophages. Thus, individual pitchers harbored relatively simple communities despite the regional species richness, and only limited kinds of predator‐prey encounters seemed to occur frequently in the regional food web. The local‐scale properties of the subdivided communities presented here provide the basic information for understanding the maintenance of regional species richness and food web complexity.
Before Cattle: A Comparative Floristic Study of Eucalyptus Savanna Grazed by Macropods and Cattle in North Queensland, Australia1
Authors: Fensham R. J. , Skull S. D. 
Published: March 2006

ABSTRACTFloristic differences between cattle‐grazed and macropod‐grazed sites (protected from domestic stock by enclosure within a Holocene lava flow) were examined in Eucalyptus savanna in north Queensland, Australia. While macropod‐grazed sites have had a lower incidence of fire than the cattle‐grazed sites, it seems probable that grazing impacts per se are the major differences between these treatments. One dominant (Capillipedium parviflorum) and another common (Sehima nervosa) native perennial grass in the macropod‐grazed treatment were not recorded within the cattle‐grazed treatment. There was generally a lower species richness and Shannon‐Weaver diversity of perennial forbs in the cattle‐grazed treatment compared to the macropod‐grazed treatment. There was higher richness, diversity, and abundance of annual grasses in the cattle‐grazed treatment compared to the macropod‐grazed treatment. The relative richness of native and exotic species was not significantly affected by cattle grazing.
Structure of Benthic Diatom Assemblages from a Mangrove Environment in a Mexican Subtropical Lagoon1
Authors: Beltrones David A. Siqueiros , Castrejón Edna Sánchez 
Published: March 2006

ABSTRACTThe taxonomic list and the structure of benthic diatom assemblages occurring in fine sediments (silt and sand) from the mangrove forest of the Balandra lagoon in Baja California Sur, Mexico was determined based on seasonal samplings for one year. Assemblage structure was analyzed using several ecological indices for estimating diversity (H'), dominance (REDI), equitability, and similarity. A total of 230 diatom taxa were identified and include 109 new records for the Baja California peninsula coast. Taxa representative of highly productive and hypersaline environments were common. Assemblages were characterized by a few abundant species and many uncommon or rare taxa. High diatom diversity estimates at all sampling sites during all seasons suggest that diatom assemblages in sediments of the Balandra lagoon represent a quasi‐pristine environment.
Tree Ferns in the Interior and at the Edge of a Mexican Cloud Forest Remnant: Spore Germination and Sporophyte Survival and Establishment1
Authors: Bernabe N. , Williams‐Linera G. , Palacios‐Rios M. 
Published: March 2006

ABSTRACTThe three most common tree fern species in a Mexican montane cloud forest fragment (Alsophila firma, Lophosoria quadripinnata and Sphaeropteris horrida) were selected for laboratory and transplant experiments. The objectives were: (1) to determine the percentage of spore germination and gametophytes producing sporophytes, and (2) to compare early establishment of sporophytes at the edge and in the interior of the forest. Percent spore germination varied between 16 and 86 percent, and the number of gametophytes that produced sporophytes was high (>50%). Survival and growth of sporophytes differed between species and habitats. Survival was greater at the edge than in the forest interior for Lophosoria, but it was similar for Alsophila and Sphaeropteris. Number and length of fronds were higher at the forest edge for individuals of Alsophila and Lophosoria, but not for Sphaeropteris. RGR was higher at the forest edge than in the forest interior for sporophytes of the three species. This study suggests that the forest edge is an appropriate habitat for establishment of Alsophila and Lophosoria, but Sphaeropteris is apparently a forest interior species.
Ecology of Aglaia mackiana (Meliaceae) Seedlings in a New Guinea Rain Forest1
Authors: Mack Andrew L. , Ickes Kalan , Jessen J. Heinrich , Kennedy Brian , Sinclair Ross 
Published: March 2006

ABSTRACTThe large seeds of Aglaia mackiana (Meliaceae) germinate and produce vigorous seedlings under closed canopies or in large gaps. To assess seedling ecology after germination, we measured growth, herbivore damage, and survivorship of seedlings over one year. The sample included shaded seedlings from dispersed seeds, undispersed seeds under parent trees, and seedlings transplanted to gaps. We quantified the light environment using hemispherical canopy photographs taken above seedlings at the beginning and end of the one–year study.Seedlings transplanted to gaps grew faster and had more leaves, larger total leaf surface area, longer secondary roots, and greater root mass than shaded seedlings. Seedlings in gaps did not differ from shaded seedlings in survivorship or amount of herbivore– and pathogen–caused leaf damage.The canopy photographs taken one year apart suggest there is a rough equilibrium in closed canopies with slight changes occurring around an average light level. Sites with < 0.06 ISF (a unitless, relative measure of canopy openness or reflected sunlight) tended to remain the same with minor fluctuations toward brighter or darker. Sites with canopy openness > 0.06 ISF tended to close; few gaps grew larger.Seedlings under parenr trees and seedlings away from parent trees had similar amounts of leaf damage and virtually identical survivorship after 18 months, but seedlings under parent trees had slower growth rates and smaller total leaf surface areas. Dispersal did not strongly benefit seeds via escaping high levels of mortality or comperition around the parent.
Ant‐Homoptera Interactions in a Neotropical Savanna: The Honeydew‐Producing Treehopper,Guayaquila xiphias(Membracidae), and its Associated Ant Fauna onDidymopanax vinosum(Araliaceae)1
Authors: Del‐Claro Kleber , Oliveira Paulo S. 
Published: March 2006

ABSTRACTWe investigate the ant fauna associated with the Neotropical treehopper,Guayaquila xiphias, on shrubs ofDidymopanax vinosumin the cerrado (savanna) of SE Brazil. Treehoppers infested plants at the border of the cerrado almost exclusively and preferably fed near the apical meristem. During the reproductive phase of the host plant, however, the vast majority of the treehoppers aggregated on the inflorescences. We found 21 ant species harvesting honeydew atG. xiphiasaggregations, the most frequent beingCamponotus rufipes, Ectatomma edentatum, C. crassus, andC. renggeri.Such a taxonomic diversity of ants tendingG. xiphiasaggregations in the cerrado is far greater than that reported for any other ant‐homopteran system. Daily turnover of ant species at a given treehopper aggregation was observed on 29 percent (64 out of 222) of theG. xiphiasaggregations recorded onD. vinosumshrubs. Species replacements probably reflect distinct humidity and temperature ranges tolerated by the species, and may ultimately reduce interspecific competition at homopteran aggregations. Since predation and parasitism onG. xiphiascan be severe, and tending ants protect the homopterans against predators and parasitoids, the round‐the‐clock activity by ants atG. xiphiasaggregations is regarded as crucial for the survival of these treehoppers in the cerrado.
Seed Dispersal by Monkeys and the Fate of Dispersed Seeds in a Peruvian Rain Forest1
Authors: Andresen Ellen 
Published: March 2006

ABSTRACTPrimary seed dispersal by two species of monkeys and the effects of rodents and dung beetles on the fate of dispersed seeds are described for a rain forest in southeastern Perú. During the six‐month study period (June–November 1992) spider monkeys (Ateles paniscus) dispersed the seeds of 71 plant species, whereas howler monkeys (Alouatta seniculus) dispersed seeds of 14 species. Spider and howler monkeys also differed greatly in their ranging behavior and defecation patterns, and as a consequence, produced different seed rain patterns. Monkey defecations were visited by 27 species of dung beetles (Scarabaeidae). Dung beetles buried 41 percent of the seeds in the dung, but the number of seeds buried varied greatly, according to seed size. Removal rates of unburied seeds by rodents varied between 63–97 percent after 30 d for 8 plant species. The presence of fecal material increased the percentage of seeds removed by seed predators, but this effect became insignificant with time. Although seed predators found some seeds buried in dung balls (mimicking burial by dung beetles), depth of burial significantly affected the fate of these seeds. Less than 35 percent of Brosimum lactescens seeds buried inside dung balls at a depth of 1 cm remained undiscovered by rodents, whereas at least 75 percent of the seeds escaped rodent detection at a depth of 3 cm and 96 percent escaped at 5 cm. Both dung beetles and rodents greatly affected the fate of seeds dispersed by monkeys. It is thus important to consider postdispersal factors affecting the fate of seeds when assessing the effectiveness of frugivores as seed dispersers.