Showing papers in "Journal of Tropical Ecology in 1990"
TL;DR: The literature on tropical secondary forests, defined as those resulting from human disturbance (e.g., logged forests and forest fallows), is reviewed to address questions related to their extent, rates of formation, ecological characteristics, values and uses to humans, and potential for management as discussed by the authors.
Abstract: The literature on tropical secondary forests, defined as those resulting from human disturbance (e.g. logged forests and forest fallows), is reviewed to address questions related to their extent, rates of formation, ecological characteristics, values and uses to humans, and potential for management. Secondary forests are extensive in the tropics, accounting for about 40% of the total forest area and their rates of formation are about 9 million ha yr−1. Geographical differences in the extent, rates of formation and types of forest being converted exist.Secondary forests appear to accumulate woody plant species at a relatively rapid rate but the mechanisms involved are complex and no clear pattern emerged. Compared to mature forests, the structure of secondary forest vegetation is simple, although age, climate and soil type are modifying factors. Biomass accumulates rapidly in secondary forests, up to 100 t ha−1 during the first 15 yr or so, but history of disturbance may modify this trend. Like biomass, high rates of litter production are established relatively quickly, up to 12–13 t ha−1 yr−1 by age 12–15 yr. And, in younger secondary forests (< 20 yr), litter production is a higher fraction of the net primary productivity than stemwood biomass production. More organic matter is pro duced and transferred to the soil in younger secondary forests than is stored in above-ground vegetation. The impact of this on soil organic matter is significant and explains why the recovery of organic matter in the soil under secondary forests is relatively fast (50 yr or so). Nutrients are accumulated rapidly in secondary vegetation, and are returned quickly by litterfall and decomposition for uptake by roots.We propose a model of the gains and losses, yields and costs, and benefits and tradeoffs to people from the current land-use changes occurring in the tropics. When the conversion of forest lands to secondary forests and agriculture is too fast or land-use stages are skipped, society loses goods and services. To avoid such a loss, we advocate management of tropical forest lands within a landscape perspective, a possibility in the tropics because land tenures and development projects are often large.
1,257 citations
TL;DR: The Asian elephant's foraging strategy in its natural habitat and in cultivation was studied in southern India during 1981-83 and crop raiding can be thought of as an extension of the elephant's optimal foraging Strategy.
Abstract: The Asian elephant's foraging strategy in its natural habitat and in cultivation was studied in southern India during 1981-83. Though elephants consumed at least 112 plant species in the study area, about 85% of their diet consisted of only 25 species from the order Malvales and the families Leguminosae, Palmae, Cyperaceae and Gramineae. Alteration between a predominantly browse diet during the dry season with a grass diet during the early wet season was related to the seasonally changing protein content of grasses. Crop raiding, which was sporadic during the dry season, gradually increased with more area being cultivated with the onset of rains. Raiding frequency reached a peak during October-December, with some villages being raided almost every night, when finger millet (Eleusine coracana) was cultivated by most farmers. The monthly frequency of raiding was related to the seasonal movement of elephant herds and to the size of the enclave. Of their total annual food requirement, adult bull elephants derived an estimated 9.3% and family herds 1.7% in quantity from cultivated land. Cultivated cereal and millet crops provided significantly more protein, calcium and sodium than the wild grasses. Ultimately, crop raiding can be thought of as an extension of the elephant's optimal foraging strategy.
286 citations
TL;DR: Five of the seven non-pioneer species showed a significant negative correlation between loads and diameter growth, and the high incidence of lianas and hemiepiphytes at La Selva is paralleled in most other Neotropical wet forests.
Abstract: We evaluated occurrence and abundance of lianas and woody hemiepiphytes on canopy and emergent tree species in primary tropical wet forest at the La Selva Biological Station, Costa Rica. Two pioneers, Cecropia obtusifolia and C. insignis, lacked both lianas and hemiepiphytes. The seven non-pioneer species differed significantly in their loads of lianas and hemiepiphytes. For all non-pioneer species, two measures of liana and hemiepiphyte loads (the percentage of the crown occupied and the combined basal area of descending hemiepiphyte and liana roots and stems) increased significantly with tree diameter. In all non-pioneer species, most trees >70 cm diameter (50-97%) were colonized. Lianas occupied more trees and had a smaller mean host diameter than did hemiepiphytes; however, basal area of descending roots or stems was equivalent for the two life forms in occupied trees. We used partial correlations con- trolling for tree diameter to evaluate the relationship between annual tree diameter growth and loads of hemiepiphytes and lianas for six non-pioneer species. Five of the six species showed a significant negative correlation between loads and diameter growth. Existing published data show that the high incidence of lianas and hemiepiphytes at La Selva is paralleled in most other Neotropical wet forests.
235 citations
TL;DR: The disinterest of caviomorph rodents in germinated seeds, because of rapid exhaustion of endosperm reserves, prevents feeding from hoarded Vouacapoua during the long dry season when resources are scarce.
Abstract: A possible mutualistic dispersal system between a large-seeded tree of French Guiana, Vouacapoua americana (Caesalpiniaceae), and caviomorph rodents, Myoprocta exilis and Dasyprocta leporina, is described. Mast fruiting of Vouacapoua at the beginning of the wet season coincides with scatter-hoarding seed dispersal. During the wet season, almost 100% of marked seeds on three sites were removed: nearly 70% were buried and the rest were eaten by mammals. Unburied seeds were attacked by insects and/or lost their ability to germinate. Rodents preferred ungerminated seeds, and had no interest in germinated seeds. Seeds were buried individually near natural objects such as palms, branches, logs, lianas, roots and trees. After predation by rodents, seedling distribution did not differ from seed distribution. Most seeds were transported less than 5 m from the feeding plots but some were carried as far as 22.4 m. Between 40 and 85% of dispersed seeds were retrieved during the following month by rodents and eaten. The disinterest of caviomorph rodents in germinated seeds, because of rapid exhaustion of endosperm reserves, prevents feeding from hoarded Vouacapoua during the long dry season when resources are scarce. Seedlings emerging from forgotten or abandoned cached seeds appear to increase the recruitment of Vouacapoua americana.
210 citations
TL;DR: Both white-lipped peccary and lowland tapir diets are unaffected by inundations and enable them to exploit the greater fruit production of flooded forests more frequently than brocket deer and collared peCCary.
Abstract: Terrestrial ungulates use different strategies to cope with widespread annual flooding of the Amazon basin. Red brocket deer (Mazama americana) and collared peccary (Tayassu tajacu) retreat to floodplain islands and shift from a frugivorous to a woody browse diet. However, both white-lipped peccary (Tayassu pecari) and lowland tapir (Tapirus terrestris) diets are unaffected by inundations; in the case of white-lipped peccary because they migrate into and out of flooded areas and in the case of lowland tapir because of their semi-aquatic nature. These strategies of white-lipped peccary and lowland tapir enable them to exploit the greater fruit production of flooded forests more frequently than brocket deer and collared peccary.
205 citations
TL;DR: Demographic projections from experimental data suggest that mammalian herbivory kills at least 48% of the juveniles of this species over two years, and contributes to the death of 32% more that actually die of drought stress, but that the higher proportions of vigorous individuals survive in edges, gaps and understorey, respectively.
Abstract: Effects of mammalian herbivory and seasonal drought were studied for Virola surinamensis (Myristicaceae) juveniles on Barro Colorado Island, Panama. Seedlings were planted at three months of age and the juveniles were monitored for two years; Treatments included: intact plants protected from mammals by cages, defoliated plants similarly protected, and unprotected plants, each planted in treefall gaps, on gap edges, and in the shaded understorey.Juveniles planted in treefall gaps survived seasonal drought far better than those planted on gap edges or in shaded understorey. Two years after establishment, juveniles protected from mammalian herbivory showed a 78% survival in gaps (mean 6.8% skylight), 50% survival on gap edges (mean 3.0% skylight), and 33% survival in shaded understorey (1.4% skylight). This advantage was due to accelerated growth in gaps. Juveniles in gaps increased 616% in height, 1075% in leaf number, and 1800% in total leaf area. Comparable numbers in edges were 247%, 378% and 690%; in understorey 33%, 222% and 289%. Accelerated growth in gaps permitted yearlings to survive drought that killed suppressed yearlings in understorey. Mean light differentials as small as 0.6% and 0.3% skylight significantly influenced survival on edges and in shaded understorey, respectively.Mammalian herbivory killed juveniles directly, and defoliation by mammals strongly accentuated drought mortality by suppressing root development. Natural defoliation was not attributable to gap conditions. Demographic projections from experimental data suggest that mammalian herbivory kills at least 48% of the juveniles of this species over two years, and contributes to the death of 32% more that actually die of drought stress. These projections suggest that 14% of the juveniles of this species die of drought mortality, independent of herbivory, during the first two years. Herbivory most strongly affects plants < 0.5 m in height, and is a continuing source of mortality among suppressed juveniles in the understorey. Steep slopes and large seed size each enhanced juvenile growth and survival in the intermediate conditions of gap edges, but not under the extreme conditions of gaps or shaded understorey.The context of establishment determines the ‘shade tolerance’ of this conspicuous canopy tree. Without serious mammalian herbivory or extreme dry seasons, V. surinamensis can easily recruit as a shade tolerant plant in the understorey. Under present conditions on Barro Colorado Island, it cannot. Persistence involves both the chances of arrival in different microhabitats, and survival therein. Projections that include both the forest area represented by gaps, gap edges, and understorey and the experimental results from this study indicate that juvenile V. surinamensis can survive for two years in gaps, edges, and understorey, but that the higher proportions of vigorous individuals survive in edges, gaps and understorey, respectively.
176 citations
TL;DR: The data available support the argument that termites contribute significantly to atmospheric fluxes of CO 2 and CH 4 and suggest a coupling of regional soil forming processes and the global C budget.
Abstract: Termites, particularly the mound building, fungus growing Macrotermitinae, reach densities of up to 400 termites m−2 in soils of dry tropical Africa. The influence of Macrotermi tinae in increasing certain soil nutrients in mounds compared to adjacent soils has been documented, but the links between litter harvesting by termites, soil fertility, and global C cycling have not been explored. This study reviews the evidence from soil science, ecology and atmos pheric chemistry and generates hypotheses to explain the role of termites in dry tropical eco systems. It is suggested that termite activity exhaustively partitions litterfall among adjacent com peting colonies, where it is so thoroughly decomposed that little or no organic C is incorporated into the soils. Associated N, P, and cations build up in the mounds, but C apparently is emitted as CO2 and CH4 from the mounds. While not adequate to calculate nutrient fluxes through termites, the data available support the argument that termites contribute significantly to atmospheric fluxes of CO2 and CH4. Moreover, they suggest a coupling of regional soil forming processes and the global C budget.
157 citations
TL;DR: Growth in some Jamaican montane forest trees was limited by the natural supplies of N and of P, and trunk diameter growth was greater in the P fertilized plot.
Abstract: Plots in the Jamaican montane forest were fertilized with nitrogen or with phosphorus to test the hypothesis that growth of trees in this natural forest is limited by the supply of N and P from the soil.Once a year from 1983 to 1986, urea was added to one plot (at 150 kg N ha−1 y−1) and triple superphosphate was added to another (at 50 kg P ha−1 y−1). In each of these plots and in two control plots, foliage of four common tree species was collected immediately before each fertilizer addition. Trunk growth was measured in 105 individuals.Foliar N concentrations were not significantly higher in trees fertilized with N compared to control trees. In Dendropanax cf. pendulus and Hedyosmum arborescens fertilization with N resulted in lower P concentrations but only after the third year of fertilization, possibly due to dilution by increased leaf production. Mean trunk diameter growth was significantly higher in the N-fertilized trees than in controls.Mean foliar P concentrations were higher in Podocarpus urbanii and Clethra occidentalis following fertilization with P, but only after two years of fertilization. Trunk diameter growth was greater in the P fertilized plot.Thus growth in some Jamaican montane forest trees was limited by the natural supplies of N and of P.
138 citations
TL;DR: It is concluded that germination requirements play a very important role in controlling the species composition of regeneration in forest understorey, gap, and large clearing habitats.
Abstract: The germination of 43 tree species native to the lowland forests of Malaysia was monitored on forest soil in trays placed in closed-canopy forest, an artificial forest gap, and a large clearing. Germination varied significantly among habitats, with only seven species germinating well in all three sites. Seed germination of most species demonstrated clear patterns of shade tolerance or intolerance identical to those long recognized for tree seedlings. Favoured locations for germination were similar to known distributional patterns of adult individuals in mature and secondary forests. Most forest canopy species germinated in the gap, but germination in the large clearing was dramatically reduced or nil; the regeneration of these species in large clearings will be severely retarded even when seeds are present. Canopy-induced inhibition of germination was apparent in several pioneer species; seeds moved from the forest into the gap or clearing germinated rapidly. Results indicate that natural treefall gaps do not inhibit the germination of most species, but do allow pioneer species to germinate, and therefore regenerate. Although germination occurred in all three locations, the level of germination for particular species varied greatly among habitats. We conclude that germination requirements play a very important role in controlling the species composition of regeneration in forest understorey, gap, and large clearing habitats.
122 citations
TL;DR: In this article, the authors made continuous measurements of litterfall at two sites with contrasting topography in a mature tropical deciduous forest in Chamela, Jalisco, on the Pacific Coast of Mexico (190 30' N, 1050 03' W).
Abstract: Continuous litterfall measurements were made from 1977 to 1982, at two sites with contrasting topography in a mature tropical deciduous forest in Chamela, Jalisco, on the Pacific Coast of Mexico (190 30' N, 1050 03' W). The climate is strongly seasonal with the annual rainfall (x = 748 mm) concentrated in six months (June to November) and a mean annual temperature of 24.90C. Results of the five-year study show that at the Valley Site (slope < 50) the mean annual litterfall was 6.58 ? 0.15 (SE) Mg ha-' y-l composed of 73.3% leaves, 17.1% woody material, 5.6% reproductive remains and 4.0% finely fragmented debris. At the Hill Site (slope 20?-400) mean annual litterfall was 3.95 ? 0.16 Mg ha-' y1, consisting of 68.8% leaves, 17.0% woody material, 9.4% reproductive remains and 4.7% fragmented debris. At the Valley Site the year-to-year variation in total litterfall was not significant. In contrast, at the Hill Site it fluctuated markedly from year to year. Litter production exhibited a pronounced seasonality: at the Hill Site total litterfall peaked near the onset of the dry season; at the Valley Site it occurred two months later, apparently as a result of differences in soil moisture avail- ability between the study sites.
121 citations
TL;DR: Owing to their more gentle treatment of seeds in the gut, birds and bats probably are more effective dispersal agents than monkeys.
Abstract: We studied the seed dispersal ecology of the Neotropical pioneer tree Cecropia peltata L. (Moraceae) in tropical dry forest by documenting its (1) fruiting phenology, (2) rates of visitation by vertebrate frugivores, and (3) rate of recruitment of juveniles in different habitats at Santa Rosa National Park in northwestern Costa Rica.At Santa Rosa, C. peltata is a common but patchily-distributed plant. Fruiting in females is seasonal, and fruit availability peaks in June through August (the early wet season). Females bear a few ripe fruit per day over a 4–5 month, fruiting period. At least 28 vertebrate species (15 diurnal and 13 nocturnal species) eat Cecropia fruit; equal numbers of ripe fruit are removed during the night and day. Owing to their more gentle treatment of seeds in the gut, birds and bats probably are more effective dispersal agents than monkeys. The recruitment rate of juveniles into already established populations was about 0.8 ha−1 y−1 compared with a rate of 176 ha−1 y−1 during the colonization of a cleared roadside.
TL;DR: Under the shaded conditions none of the species grew beyond the two leaf stage over their first year, though Shorea curtisii seeds probably germinated less well but seedling survival and growth was better than canopy-shaded conspecifics.
Abstract: There was fruiting of the dipterocarps of Pantai Aceh Forest Reserve, Penang, Peninsular Malaysia in September 1986. The opportunity was taken to investigate the establishment and seedling survival of Shorea curtisii, Shorea multiflora and Shorea pauciflora over the subsequent year. The germination and seedling survival of Shorea curtisii was compared between canopy gaps and forest understorey sites. Under the shaded conditions none of the species grew beyond the two leaf stage over their first year. Shorea multiflora seedlings suffered a 72% mortality, significantly lower than that of Shorea pauciflora (89%) and Shorea curtisii (93%). The major cause of mortality appeared to be drought, though Shorea curtisii was also prone to predation by small mammals. In a gap, Shorea curtisii seeds probably germinated less well but seedling survival (28% versus 7%) and growth was better than canopy-shaded conspecifics. Seedlings in gaps escaped small mammal predation.
TL;DR: In this paper, the authors describe the forests as a background for soil and litterfall studies from 1 ha plots at each of the following altitudes: 100 m, 500 m, 1000 m, 1500 m, 2000 m, and 2600 m.
Abstract: Volcan Barva, Costa Rica, has on its northern slope an unbroken sequence of rain forest on volcanic parent materials from near sea level at La Selva Field Station up to its summit at 2906 m. It provides a good area to study forest changes with altitude and their causes. In the present paper we describe the forests as a background for soil and litterfall studies from 1 ha plots at each of the following altitudes: 100 m, 500 m, 1000 m, 1500 m, 2000 m and 2600 m. The canopy heights (with height of the highest emergent in parentheses) ranged from 35–40 m (45 m) at 100 m to 20–23 m (32 m) at 2600 m; basal area was least (22.7 m2) at 100 m and highest (51.2 m2) at 2600 m; the tree (≥10 cm dbh) density ranged from 391 ha–1at 500 m to 617 ha–1 at 2600 m. Most trees were identified and on samples of them we recorded presence of buttresses, lianes, skiophytic climbers, vascular epiphytes and bryophytes; and drew profile diagrams. In the classification of Whitmore (1984) the two lower plots are evergreen lowland rain forests; the other four are lower montane rain forest. Species richness was highest in the plot at 500 m, with at least 135 species of tree, and least at 2600 m, with at least 35 species. The Volcan Barva forest altitudinal sequence is briefly compared with those elsewhere.
TL;DR: Monitoring of fruit production by an understorey tree in treefall gaps and under intact canopy in a Costa Rican lowland rain forest suggested that gaps function as 'keystone habitats' by providing resident frugi- vores with fruit during periods of general fruit scarcity.
Abstract: Fruit production by an understorey tree, Miconia centrodesma, was monitored in treefall gaps and under intact canopy in a Costa Rican lowland rain forest. Trees in gaps dis- played much less seasonality in fruit production than trees of intact forest sites. For example, ripe fruits were common on gap trees for a six month period (January-June) when few or no trees under intact canopy were in fruit. The frequent and aseasonal fruiting of gap trees demon- strates that they are not constrained by phenological cueing mechanisms; the influence of such cues is overridden by habitat. Trees in gaps also produced larger crops, had more extended fruiting episodes, and fruited more frequently than shaded conspecifics. This level of intra- specific variation in fruiting behaviour suggests that treefall gaps play an important role in deter- mining the reproductive success of M. centrodesma. A substantial proportion of an individual's lifetime seed output may be produced during the brief period it occupies a gap. In addition, the large and continuous supply of fruits produced in gaps by M. centrodesma and other under- storey plants, may mean that gaps function as 'keystone habitats' by providing resident frugi- vores with fruit during periods of general fruit scarcity.
TL;DR: The 71 ha Bukit Timah Nature Reserve contains the largest surviving area of primary rain forest in Singapore and consists of at least 854 species: 787 angiosperms in 109 families, 65 pteridophytes and three gymnosperms.
Abstract: The 71 ha Bukit Timah Nature Reserve contains the largest surviving area of primary rain forest in Singapore. The recorded vascular plant flora of the forest consists of at least 854 species: 787 angiosperms in 109 families, 65 pteridophytes and three gymnosperms. 58.6% of the species are trees or shrubs, 18.7% climbers, 12.3% terrestrial herbs, 8.8% epiphytes and hemi-epiphytes, 1.0% saprophytes and 0.6% parasites. The four families with most species - Rubiaceae, Euphorbiaceae, Orchidaceae and Moraceae - account for a quarter of the angio- sperm flora but contribute few large trees. Community reproductive phenology is charac- terized by supra-annual bursts of general flowering and fruiting, contrasting with a low back- ground level. After an exceptionally dry and sunny February, 1987, more than 150 species in 42 families flowered between late March and late May, followed by an equally well-defined fruiting peak 13 weeks later, between late June and late August.
TL;DR: Patterns of body size based on length and mass measurements of 603 individual snakes of 27 species captured at La Selva, Costa Rica from March 1982 through August 1984 are reported to show more diverse species richness and morphological diversity than a temperate assemblage.
Abstract: Length-mass relationships within an assemblage of tropical snakes are used to describe morphological groups. We report patterns of body size based on length and mass measurements of 603 individual snakes of 27 species captured at La Selva, Costa Rica from March 1982 through August 1984. This assemblage of snakes is composed of at least four morphological groups each of which consists of species with similar habitat preferences. These groups are heavy-bodied terrestrial forms, light-bodied arboreal forms, long-tailed leaf-litter forms, and forms of unextreme relative mass and tail length. This tropical snake assemblage is more diverse in species richness and morphological diversity than a temperate assemblage.
TL;DR: The hypothesis, developed from studies of bird communities, that the under- storey of Malaysian dipterocarp forest supports relatively few obligate frugivores, at least in non-masting years is supported.
Abstract: Bat communities in the understorey of primary lowland dipterocarp forest in peninsular Malaysia and Sabah were sampled with mist nets and harp traps to estimate their trophic structure. Overall, 4 of 26 species (15%) at one site, and 6 of 33 species (18%) at the other site were frugivores, while the remainder were insectivores. In terms of individuals, 7-12% of all captures were frugivores. However, the true proportion of frugivores at both sites was pro- bably closer to 1%, because the sampling procedures were strongly biased towards frugivores. In contrast, previously published studies indicate that frugivores comprise 34-48% of species, and up to 80% of individuals in bat communities in the understorey of Neotropical forest. These results support the hypothesis, developed from studies of bird communities, that the under- storey of Malaysian dipterocarp forest supports relatively few obligate frugivores, at least in non-masting years. However, further data are required on bats in the canopy, and on the foraging ranges of bats to compare the absolute densities of bats in Malaysian and Neotropical forests.
TL;DR: The low reproductive densities, combined with the skewed sex ratios and overlapping generations of these species, create very small effective breeding populations, placing species such as these at great risk in the face of deforestation and habitat fragmentation.
Abstract: The densities of the breeding populations and the sex of all flowering individuals were recorded for five dioecious canopy tree species of Central Amazonian Myristicaceae, in 11 study areas of the Minimum Critical size of Ecosystems Project totalling 22.5 ha. Adult population densities were extremely low, ranging from 0.38 to 1.61 ha–1 for the five species studied. In a 10 ha study plot the mean distance to the nearest flowering conspecific ranged from 48 to 100 m, while the mean distance to the nearest opposite sex conspecific was 147 m. The two most abundant species, Iryanthera macrophylla and Virola calophylla, both showed male-biased sex ratios, of 23:9 and 20:6, respectively. The size class distribution of males, females and non-flowering individuals in V. calophylla suggests that earlier reproductive maturation of male plants may provide a partial explanation for this bias. In I. macrophylla, since 95% of the individuals were observed flowering, the observed ratio is representative of the population, and may be caused by sex shifts from male to female. The low reproductive densities, combined with the skewed sex ratios and overlapping generations of these species, create very small effective breeding populations, placing species such as these at great risk in the face of deforestation and habitat fragmentation.
TL;DR: Evidence that such a mechanism is operating among the foundress queens of another leaf-cutting ant species, Atta sexdens L., is presented and it is shown that, once in the preferred habitat, they search for the best microhabitat.
Abstract: The founding of a new nest is the most crucial period in the life of an ant colony (Wilson 1971). Mechanisms that enhance colony survivorship during this phase are thus of great value. Of special importance is the search for a suitable habitat by the foundress queen, since established colonies of most ant species are unable to migrate over long distances (Wilson & Hunt 1966). That ant queens select the habitat in which they will found a new colony has been demonstrated for several temperate zone species (Brian 1952, Brian et al. 1966, Pontin 1960, Wilson & Hunt 1966) and for the Neotropical leaf-cutting ants Atta cephalotes L. and Acromyrmex octospinosus Reich (Cherrett 1968). In this paper, evidence that such a mechanism is operating among the foundress queens of another leaf-cutting ant species, Atta sexdens L., is presented. Furthermore, it is shown that, once in the preferred habitat, they search for the best microhabitat. Field work was done at 'Fazenda Dimona', a ranch located about 70 km north of Manaus, Brazil (600 4' W, 20 19 S). In this ranch two forest fragments of 1 ha, one of 10 ha and one of 100 ha were created during late 1984 to meet the requirements of the Minimum Critical Size of Ecosystem Project (a collaborative binational research project between the Instituto Nacional de Pesquisas da Amazonia and the World Wildlife Fund-US). A fifth fragment about 100 m wide and bordering a local stream, but not related to the MCSE Project, was created at the same time. Brachiaria grass was planted in the cleared area, but no efforts were made to maintain the pasture free of weed species. One year later, at the beginning of the study, stands of secondary vegetation 1-2 m tall, mainly Laetia procera (Poepp.) Eichl., Solanum rugosum Dun. and species of Cecropia, were present throughout the pasture. The vegetation of the fragments was a primary, terra-firme forest (as defined by Guillaumet 1987).
TL;DR: Certain sympatric members of the monophyletic Polyalthia hypoleuca complex are shown to have clearly diverged in autecological characteristics that affect their distribution including P. glauca, P. Hypoleuca, and P. sumatrana.
Abstract: One component of the high organismal diversity of tropical lowland rain forests is the existence of series of closely related, sympatric species. For example, the six distinct tree species of the monophyletic Polyalthia hypoleuca complex regularly grow sympatrically in various combinations throughout the rain forests of Malesia. Theoretical and empirical evidence has been presented indicating that the members of such series either (1) are well differentiated with respect to at least one major niche component; or (2) may lack differentiated niches. In this study, certain sympatric members of the complex are shown to have clearly diverged in autecological characteristics that affect their distribution including: (1) P. glauca, P. hypoleuca, and P. sumatrana differ in growth characteristics, height at maturity, seedling germination requirements, and are found on soils with differing degrees of hydration; (2) P. discolor grows to a different height and on different substrate types than does P. multinervis; and (3) P. glauca and P. hypoleuca seedlings differ in transpiration characteristics and response to flooding and drought.
TL;DR: Flooded savannas in south-west Venezuela consist of seasonal, marshy and flooded grassland communities, the distribution of which depends on soil level, and Hymenachne amplexicaulis appears to be the least drought tolerant from the species selected.
Abstract: Flooded savannas in south-west Venezuela consist of seasonal, marshy and flooded grassland communities, the distribution of which depends on soil level. Seasonal grasslands are dominated by tuft-forming, rhizomatous C4-grasses (exemplified by Paspalum chaffanjonii in this study), while flooded grasslands are dominated by stoloniferous grasses which develop rooted, floating culms during the rainy season (Leersia hexandra and Hymenachne amplexi- caulis). The interface between these two communities is a marshy grassland dominated by stoloniferous grass species which tolerate flooding to a depth of 10 to 25 cm (Panicum laxum and Leersia hexandra). All perennial grass species in flooded grasslands behave as typical C3 plants, while marshy grasslands are dominated by Panicum laxum, a species with reduced photo- respiration, low RuBP/PEP-carboxylase ratios, and low absolute RuBP-carboxylase activity compared to C3 grasses. It also has lower photosynthetic rates than the other grass species. Hymenachne amplexicaulis appears to be the least drought tolerant from the species selected, in accordance with its distribution in the wettest side of the flooding gradient studied. The other species showed marked reduction in relative water content and pronounced increase in leaf proline content in drought experiments lasting 6 to 30 days. Alcohol dehydrogenase in- creased markedly in response to anaerobiosis in the root environment in the tuft forming grasses, while the stoloniferous species with ascending culms were least affected by this treat- ment, probably as a result of better aeration inside the culms and also to the production of adventitious roots in upper nodes. Nitrate reductase activity increased as a result of anaerobiosis in the roots but not in the leaves, of all species except Leersia hexandra. No difference among the species was found in malate accumulation, or the activity of malic enzyme.
TL;DR: The abundance and distribution of reptiles and amphibians inhabiting tropical monsoonal wetlands in Kakadu National Park, northern Australia, were monitored between late 1979 and 1982 as discussed by the authors.
Abstract: The abundance and distribution of reptiles and amphibians inhabiting tropical monsoonal wetlands in Kakadu National Park, northern Australia, were monitored between late 1979 and 1982. Seasonal trends in species richness, and the influence of various environmental attributes (including those caused by feral ungulates) on species distribution patterns were also examined.These wetlands support a high proportion of the amphibian species known from the Park, but are of less importance to reptiles. Within the wetlands, the structurally more complex forested ‘margins’ support many more species than the treeless floodplains. Amphibian species distributions seem to be influenced primarily by elevation, through its effects on soil moisture and flooding levels, while reptile distribution patterns reflect a more complex set of environmental factors, with structural attributes (e.g. vegetation height structure and cover, refuge abundance, leaf litter cover and depth, extent of flooding) being of prime importance.Feral buffalo and pigs, through their grazing, trampling and wallowing, may considerably influence such structural attributes and change the duration and extent of water lie, and thus indirectly affect species distribution patterns. Current buffalo culling programmes provide an opportunity to monitor vegetation and faunal changes, and quantify feral animal impact post facto.
TL;DR: The carbon-nitrogen (C/N) ratio of soil organic matter is related to the patterns of nitrogen immobilization and mineralization during organic matter decomposition by micro-organisms.
Abstract: The carbon-nitrogen (C/N) ratio of soil organic matter is related to the patterns of nitrogen immobilization and mineralization during organic matter decomposition by micro-organisms (Swift et al. 1979). Its value decreases as decomposition proceeds (Swift et al. 1979), is negatively correlated with the rate of nitrogen mineralization in decomposition experiments by soil incubation (Tsutsumi 1987a), and can indicate the decomposition rate in terrestrial ecosystems (Jordan 1985). The studies of soil carbon and nitrogen in tropical forest ecosystems (Jordan 1985), such as lowland rain forests (Uhl & Jordan 1984, Yoda & Kira 1982), seasonal forests (Hase & Folster 1982), and montane rain forests (Edwards 1982, Edwards & Grubb 1982), and various types of forests along altitudinal gradients (Marrs et al. 1988, Yoda & Kira 1969), have suggested an increase of the soil C/N ratio with a decrease in temperature and an increase in moisture (Jenny 1941). However, it also depends on the nitrogen contents of the litter itself (Jordan 1985, Swift et al. 1979), local variations in soil conditions according to topography and parent material (Tsutsumi 1987b). In an analysis of the structure and environmental relationships of seven tropical forest stands, Jordan (1985) found that the first principal component, which accounted for 63% of the ecosystem variance, was highly correlated (r = 0.94) with total soil nitrogen. Nitrogen has great effect on plant growth, affecting cell number and cell size (Chapin 1980). The availability of soil nitrogen to plants is determined largely by its mineralization during the decomposition of organic matter (Jordan 1985, Swift et al. 1979). Therefore we may expect a relationship between the C/N ratio and tree growth. This was
TL;DR: A raid by army ants on a colony of tropical swarm-founding wasps in Costa Rica involved a number of behavioural responses of the wasps to the ant attack which have not been reported before, and occurred at an unusually high elevation.
Abstract: In this note we describe a raid by army ants (Eciton burchelli Westwood) on a colony of tropical swarm-founding wasps (Agelaia yepocapa Richards). The general features of such raids have been discussed elsewhere (Jeanne 1970, Naumann 1975, Young 1979). Army ants are a major predation force on social wasp colonies in many Neotropical areas (Chadab 19 79a, Jeanne 1975), and features of swarm-founding wasp behaviour indicate strong selection for dealing with army ant predation (Chadab 19 79b, Jeanne 1975). The raid described here involved a number of behavioural responses of the wasps to the ant attack which have not been reported before, and occurred at an unusually high elevation. The raid took place next to the dirt road leading to the Monteverde Cloud Forest Preserve in Puntarenas Province, Costa Rica. The wasp nest was located 4 m above the ground in a trunk cavity of a large (about 0.7 m DBH) broadleaf tree, several kilometres downhill from the Preserve headquarters. The surrounding habitat is a mixture of disturbed forest and pasture, at an elevation of about 1100 m. This is near the upper elevational limit for E. burchelli in the area (William Haber, pers. comm.) We first noticed the attack on 27 July 1988 late in the morning, but local residents claimed it had begun the previous afternoon. Army ants were entering the wasp nest cavity and extracting wasp brood (larvae and pupae) when we arrived, and continued to do so during our last observation at 1500 h that afternoon. The raid spanned a period of at least 24 h though it is uncertain whether it had continued through the night, when army ants usually bivouac (Franks 1989). The wasps were identified as Agelaia yepocapa (formerly Stelopolybia yepocapa). This is the first record of an A. yepocapa nesting site; like most
TL;DR: Leigh et al. as discussed by the authors presented data collected over a two-year period on dead mammals recovered from a single lowland tropical forest site in central Panama, where the survey was carried out from 1 September 1977 through 31 August 1979, a total of 24 months.
Abstract: Few data exist on mortality of tropical forest mammals. Though dramatic reductions in population size have been reported for particular mammals in some years, such information is largely anecdotal and generally attributed to an unusual extrinsic factor such as a forest-wide fruit shortage or outbreak of a virulent disease (e.g. Collias & Southwick 1952, Foster 1982, Kaufmann 1962). It would be useful to have annual mortality data from specific mammal populations and communities, both for comparative purposes and to focus investigation on possible causal factors. However, the difficulty of collecting mortality data in the tropical forest is well appreciated. Vultures show a remarkable ability to locate fresh carcasses (Houston 1986) and the warm, humid environment and abundant insect life results in rapid destruction of any remainder. Here I present data collected over a two-year period on dead mammals recovered from a single lowland tropical forest site in central Panama. These data, though not extensive, give an indication of annual mortality in this mammalian community. In addition, for a few species, mortality peaks occurred at approximately the same time each year. Interspecific mortality peaks were not always synchronous, suggesting that factors adverse for some species may have had little effect on others in this same habitat. The survey was carried out from 1 September 1977 through 31 August 1979, a total of 24 months, on Barro Colorado Island, a 1500 ha nature preserve located in Gatun Lake, Republic of Panama. Details of the climate, topography, flora and fauna of Barro Colorado can be found in Leigh et al. 1982. Barro Colorado Island lends itself to the collection of infrequent and unpredictable data such as the occurrence of dead mammals because typically many researchers are active in the forest on any given day throughout the year. This greatly improves the chances that dead mammals will be encountered
TL;DR: Fruit production by Acacia albida trees in Mana Pools National Park, Zimbabwe, was monitored over eight years and potential fruit production was high when the late wet season was wet or cool and when fruit production in the previous year was low.
Abstract: Fruit production by Acacia albida (Leguminosae: Mimosoideae) trees in Mana Pools National Park, Zimbabwe, was monitored over eight years. Timing of ripe fruit-fall varied between years, as did fruit production: production of ripe fruits by the same tree varied from 5.4 kg in 1983 to 290.1 kg in 1988. Baboons reduced fruit production by feeding on unripe fruits and the mass eaten each year was negatively correlated with rainfall. Potential fruit production (i.e. production in the absence of baboons) was high when the late wet season was wet or cool and when fruit production in the previous year was low. Late wet season rainfall and temperature probably determined the degree of defoliation by caterpillars: in 1983 and 1987, when the late wet season was hot and dry, the trees were almost completely defoliated. During the late dry season, A. albida fruits were an important component of the diets of waterbuck, eland, elephant, buffalo and kudu; they were seldom eaten by hippopotamus and were ignored by zebra and warthog.
TL;DR: In this article, field observations and laboratory experiments on unweathered and weathered dune sand beneath a tropical deciduous forest in Veracruz, Mexico were used to test the hypo- thesis that temporary nutrient adsorption by more weathered soil facilitates more effective nutrient recycling through the stimulation of a superficial fine root system.
Abstract: Field observations and laboratory experiments on unweathered and weathered dune sand beneath a tropical deciduous forest in Veracruz, Mexico were used to test the hypo- thesis that temporary nutrient adsorption by more weathered soil facilitates more effective nutrient recycling through the stimulation of a superficial fine root system. An analysis of soil solution composition in the field indicated that K, P and NOR-N were being more effectively retained in weathered sand topsoil than in recent sand but, in a leaching experiment, only NO -N was more effectively adsorbed by this soil. Fine roots in weathered sand were more concentra- ted superficially than in recent sand, and a bioassay with seedlings of Cedrela odorata showed more fine root proliferation in this medium than in recent sand. In combination, these data suggest that weathering of sand in this area promotes an increased nitrate adsorption capacity which may stimulate greater root proliferation in topsoils and lead to the entrainment of other nutrients in a more concentrated topsoil-vegetation cycle. If these results can be applied to the larger domain of tropical soils generally, they suggest that nitrate adsorption may play an important role in stimulating effective nutrient recycling by forests occupying weathered soils.
TL;DR: This article studied the breeding success and distribution of three species of eagles, four species of vultures and one species of eagle owl on two areas of differing primary productivity from 1973 to 1984.
Abstract: We studied the breeding success and distribution of three species of eagles, four species of vultures and one species of eagle owl on two areas of differing primary productivity from 1973 to 1984. Densities of all species were lower in areas with lower productivity. Breed-ing success on both biomes was similar, the lower densities of birds on the least productive biome apparently compensating for the lower productivity. Eagles produced more one-egg clutches, laid later and reared fewer young in the period of poor rainfall, probably as a result of reduced productivity. Vulture data were difficult to interpret because abundant food at breed-ing time was created by ungulate population management throughout the entire study period. Concentrations of all species on the more productive biome, and solitary breeding on the least productive biome by a normally colonially breeding species, suggests that primary production also influences vulture densities and perhaps breeding success.