Closed-canopy Habitats Research Articles

Dietary reconstruction of Miocene Gomphotherium (Mammalia, Proboscidea) from the Great Plains region, USA, based on the carbon isotope composition of tusk and molar enamel

The Miocene of the Great Plains of North America has long been recognized as an interval of major ecological reorganization. To reconstruct the dietary response of the proboscidean Gomphotherium to Miocene ecosystem change in the Great Plains, we analyzed the carbon isotope composition of 185 serial samples of tusk enamel from 17 individuals and bulk samples of posterior molars from 15 individuals of Gomphotherium from localities in the Great Plains ranging in age from the Early Barstovian land mammal age (ca. 15 Ma) to the Early Hemphillian land mammal age (ca. 8 Ma). Sets of samples from each tusk were designed to encompass about 1 year of tusk growth. Based on cheek tooth morphology, Gomphotherium is thought to be a browser with a diet primarily of dicots. The mean δ 13C of all samples is −9.8±1.2‰, indicating that the diet of Gomphotherium was dominated by C 3 biomass. If Gomphotherium habitually foraged on water-stressed plants in arid habitats, which would have δ 13C values higher than the average composition for C 3 and C 4 plants, then all but one individual in this study consumed less than 50% C 4 biomass. The maximum percentage of C 4 in the diet would be much lower if food plants had average δ 13C values or if Gomphotherium foraged in closed-canopy habitats. Differences in δ 13C values between specimens from the southwestern US and the Great Plains, as well as between some coeval specimens from Nebraska, suggest geographic differences in either diet or typical foraging habitat. The data do not indicate a trend toward inclusion of more C 4 vegetation in the diet of Gomphotherium during the Miocene, and none of the serially sampled tusks exhibit seasonally varying δ 13C profiles. For most of its history in North America, Gomphotherium was a C 3 browser or a mixed feeder with a preference for browse. Our results indicate that areas of wooded habitat sufficient to support herds of large-bodied herbivores remained available in the Great Plains through the Late Miocene.

Habitat use and feeding ecology of Kulal White-eye Zosterops kulalensis

Kulal White-eye Zosterops kulalensis is endemic to Mt Kulal, northern Kenya. It is currently considered a Vulnerable species because of its restricted range. We investigated its habitat and microhabitat use, and flocking and foraging behaviour, with respect to seasonal and diurnal variation. In the dry season, Kulal White-eye was encountered only in montane forest, where it was more abundant in glades than in closed-canopy habitats. Here it fed frequently on fruit, as most fruiting occurred in the drier months. In the wet season population density was also higher in glades than in closed-canopy forest, but birds were mostly insectivorous. Foraging in bush outside the forest was favoured. In the wet season, Kulal White-eye inhabited both the forest and the drier bush at lower altitudes, and avoided habitats with mature trees, preferring young tree formations where vegetation was thicker. Flock size was larger in the dry season, and, in the wet season, larger flocks were encountered in the morning and in late afternoon. Our study suggests that Kulal White-eye is less restricted to mature forest than previously thought. The conservation of the species requires that both the forest and the adjoining bush habitats receive adequate protection. Although some traditional human activities could be compatible with conservation, grazing of domestic animals inside the forest and the removal of large tracts of bush to create new pastures could be detrimental to the species.

Efforts to restore habitat connectivity for an upland tropical rainforest fauna: A trial of underpasses below roads

Summary Four large underpasses, specifically designed for movements by fauna, form part of a major road upgrade project on the Atherton Tablelands in northeast Queensland, Australia. We describe the design and rationale of a project to test their effectiveness in restoring habitat continuity for tropical rainforest fauna. The large blocks of upland rainforest divided by the road are recognized for their high faunal conservation significance, forming habitat for many rare or threatened species. Ecologists, road engineers and the Atherton Tablelands conservation community have united with a common conservation goal: to design the ‘furniture’ within the underpasses and accomplish rainforest revegetation to provide protective cover and attract fauna to underpass entrances. Prior to construction, small mammals were trapped weekly for several months in habitats close to the road upgrade. The small mammal community comprised grassland species in abandoned pasture and differed significantly from the rainforest specialists found in three closed canopy habitats: rainforest edge, rainforest interior and Lantana shrubland. Rainforest restoration works designed to restore connectivity for rainforest fauna across this abandoned pastureland (via the underpasses to major rainforest blocks to the north and south of the road) are currently in progress. Monitoring of the effectiveness of the underpasses in allowing faunal movements will involve the use of infra‐red‐triggered cameras within the underpasses and near underpass entrances, and a survey of road‐killed fauna both prior to and postconstruction. Further examination of small mammal community structure and movements, with respect to both the new road and the underpasses, will be undertaken once rainforest plantings have become established. This evaluation should provide insights for further road‐associated restoration projects in rainforest regions.

Carbon isotope fractionation between diet and bioapatite in ungulate mammals and implications for ecological and paleoecological studies

The isotope enrichment ɛ* of 13C between tooth enamel of large ruminant mammals and their diet is 14.1 ± 0.5‰. This value was obtained by analyzing both the dental enamel of a variety of wild and captive mammals and the vegetation that comprised their foodstuffs. This isotope enrichment factor applies to a wide variety of ruminant mammals. Non-ruminant ungulates have a similar isotope enrichment, although our data cannot determine if it is significantly different. We also found a 13C isotope enrichment ɛ* of 3.1 ± 0.7‰ for horn relative to diet, and 11.1 ± 0.8‰ for enamel relative to horn for ruminant mammals. Tooth enamel is a faithful recorder of diet. Its isotopic composition can be used to track changes in the isotopic composition of the atmosphere, determine the fraction of C3 or C4 biomass in diets of modern or fossil mammals, distinguish between mammals using different subpathways of C4 photosynthesis,and identify those mammals whose diet is derived from closed-canopy habitats.

Use of naturally and anthropogenically disturbed habitats in Amazonian rainforest by the teiid lizard Ameiva ameiva

We studied the effects of natural and anthropogenic habitat disturbances on environmental temperatures and their consequent effects on thermoregulation and habitat use of Ameiva ameiva in a complex habitat matrix of primary tropical forest and several types of disturbed forest in Amazonian Brazil. Data on Ameiva ameiva from other regions in Brazil with habitats that have little canopy coverage are compared with data from rain forest sites to determine if activity of rain forest Ameiva is temporally or spatially limited by the thermal opportunities available in shaded environments. Ameiva ameiva preferentially used disturbed habitats in rain forest regions. These sites had significantly higher environmental temperatures than did surrounding undisturbed rain forest. Environmental temperature distributions indicate that the closed canopy rain forest is a thermally marginal habitat for Ameiva ameiva and that high temperatures resulting from forest clearing are likely to enable Ameiva ameiva to increase foraging activity in adjacent forest edges above what is possible in the continuous interior forest. Ameiva ameiva from rain forest, cerrado and savanna regions of Brazil had significantly lower body temperatures than Ameiva from caatinga, an open habitat type with little canopy coverage. This difference is probably due to high ambient temperatures and the high availability of basking sites in open habitats and suggests a thermal constraint on habitat use and time of activity for Ameiva in closed canopy habitats.

Forest Canopy Closure and Juvenile Emigration by Pool-Breeding Amphibians in Maine

For amphibians that breed in temporary pools, juvenile emigration is an important life-history movement linking the aquatic habitat of larvae to the surrounding upland habitats occupied by maturing animals and adults. However, little is known regarding the habitat preferences and sensitivity to disturbance of newly metamorphosed amphibians. We examined whether selection occurs for closed-canopy forest conditions during emigration by using pitfall traps and drift fences to sample naturally occurring populations of wood frogs (Rand sylvatica) and spotted salamanders (Ambystoma maculatum) along recently created forest-clearcut edges in central Maine. Habitat preferences during emigration were further investigated via an experimental approach that quantified movements of newly metamorphosed wood frogs cultured in artificial pools located along an abrupt forest-power line edge. Among natural populations, the abundance of juveniles and adults of both species declined sharply across a gradient running from relatively mature forest-interior habitat (70-90 yr old) to recently clearcut habitat (2-11 yr old). Similarly, in the power line experiment, juvenile wood frogs showed an emigration preference for closed-canopy habitat immediately upon metamorphosis, with the highest capture rates occurring in microhabitats characterized by dense foliage in both the understory and canopy layers. Our results suggest populations of wood frogs, spotted salamanders, and other amphibian species breeding in temporary pools are likely to benefit from efforts to maintain connectivity between upland forest habitats and aquatic breeding sites. Seminatural field experiments provide a valuable manipulative approach for studying the potential effects of habitat fragmentation on populations of migratory amphibians.

Genet structure and determinants of clonal structure in a temperate deciduous woodland herb,Uvularia perfoliata

1 We used isozyme variation to examine the genet structure of Uvularia perfoliata patches in gap and closed canopy habitats in a temperate deciduous forest in Maryland, USA. 2 A large patch in a gap habitat was composed of a small number of widely spread genets with many ramets, and a large number of genets with more restricted distribution and few ramets. Genets with many ramets were patchily distributed at a metre scale. Analysis of genet structure on a scale of square centimetres, however, revealed that the genets were highly intermingled with no clear boundaries between them. The presence at both scales of sampling of many genets with unique multilocus genotypes indicated continuing genet recruitment within the population. 3 In the closed canopy habitat, the patches examined were each composed of a single unique multilocus genotype, suggesting that each had developed by asexual propagation following the establishment of a single genet. 4 The clonal structure of U. perfoliata patches in both gap and closed canopy habitats therefore appears to depend on recruitment patterns of genets. Populations in closed canopy habitats are characterized by a ‘waiting’ strategy, in which asexual ramet production maintains populations until genet recruitment by seed production can occur under the more optimal conditions associated with canopy gaps. Extended sampling suggests that the genetic diversity of U. perfoliata populations is primarily controlled by the disturbance regime of the forest canopy.

Effect of small-scale disturbance on butterfly communities of an Indochinese montane rainforest

The differences between the composition of butterfly communities in gaps created by illegal logging and in closed canopy habitat were studied in montane forest in the Tam Dao Mountains, northern Vietnam. Methods of constrained ordination (canonical correspondence analysis, redundancy analysis) were used for data analysis. The species composition in the two habitats differs significantly: stenotopic species confined to the closed canopy habitat usually have a smaller geographic range. Although the species richness and diversity was higher in gaps, the conservation value of closed canopy habitat lies in the presence of species with restricted range. The creation of gaps by local people changes the natural disturbance regime and causes a threat to biota confined to the closed canopy forest. Bioindicator importance of the local butterfly fauna (Papilionoidea) was evaluated and a list of species is presented.

Experimental Manipulation of Sculpin (Cottus cognatus) Populations in a Small Stream

Abstract We examined movement and age distribution of experimentally manipulated natural populations of slimy sculpin (Cottus cognatus) in streams having open and closed vegetation canopies. Densities were estimated in three treatments: reference populations (no transfers), reductions (fish removed from the sites), and additions (fish added to the sites). Biweekly replenishment of addition sites raised sculpin densities to over 10/m2 in the open canopy, at least 3 times that of reduction and reference populations. In closed canopy habitats, densities of addition populations (6/m2) were twice as great as reference populations (3/m2), although reduction populations (41m2) did not differ from either. Addition sites showed a net increase of numbers of sculpin over four summer months, in spite of a decline in older sculpin (age III-V years). Reduction sites showed no differences from reference sites regarding sculpin numbers, indicating that recruitment of fish to reduction sites did occur. However, more than ...

Leaf Litter Decomposition across Broad Thermal Gradients in Southeastern Coastal Plain Streams and Swamps

ABSTRACT A 16 week study of leaf decomposition for sweetgum (Liquid-ambar styraciflua), American sycamore (Platanus occidentalis), and baldcypress (Taxodium distichum) was conducted during winter 1983–1984 in thermal and non-thermal streams and floodplain swamps in South Carolina. Mean daily temperatures ranged from 7.6 to 49.0 C in streams and from 10.5 to 29.8 C in swamps. Sweetgum leaves consistently decomposed more rapidly than sycamore leaves and leaf decomposition rates for sweetgum and sycamore tended to be inversely related to thermal regimes. Cypress leaves showed relatively uniform, slow losses over all temperature ranges. The highest processing rates for all leaf types were found in non-thermal, closed-canopy swamp habitat, where the shredding caddisfly, Pycnopsyche sp., was relatively abundant.