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1.
Home range size, habitat utilization, and activity patterns of five adult Bairds tapirs (Tapirus bairdii) were studied via radiotelemetry from June 1995 to May 1996 in Corcovado National Park, Costa Rica. Estimates of 4153 animal locations were made. Home range sizes (95% minimum convex polygon) for the entire study period (wet season and dry season) averaged 125.0 ha (SD = 72.7), 94.9 ha (SD = 47.6), and 96.8 ha (SD = 51.2), respectively. Monthly home range sizes averaged 55.5 ha (SD = 32.1) and did not vary between seasons. Across the entire study, secondary forest, the most commonly used habitat type (61.3%) was utilized more than expected as predicted by availability (49.6%), while the second most used habitat, primary forest, was used (25.0%) less than expected (36.2%). The same general habitat selection pattern was observed in the dry season. Wet season habitat utilization values showed tapirs using both primary and secondary forest habitats in proportion to their availability. Diurnal and nocturnal activity levels were estimated at 20.2 and 80.4 percent, respectively. More diurnal and less nocturnal activity was observed during the wet season compared to the dry season.  相似文献   

2.
The black lion tamarin (Leontopithecus chrysopygus) is a threatened species due to past destruction of its natural habitat, thus knowledge of its home range size and use is essential in planning for its conservation. I studied one group for 4 months in the Morro do Diabo State Park, in São Paulo State, Brazil. I estimated the home range of the group to be 64 and 127 ha via the quadrat and convex polygon methods, respectively, while a composite method yielded an estimate of 106 ha. They ate insects most frequently (38% of scans), a resource which was distributed throughout their home range. Fruit was the second major resource, but when it was not available, they ate more gum. The exploitation of fruits was associated with dryland forest, while gum-feeding occurred mainly in swamp forest. The study group used a transition zone between dryland and swamp forest most frequently, and all of their sleeping trees were located there. Although the vegetation reached 15–20 m, the group spent most of the time (55%) in the upper understory, between 4 and 8 m high. The study group revealed more specific habitat needs than thought previously, suggesting that the current population may be smaller than estimated.  相似文献   

3.
We collected data during a 10-month study carried out on the mongoose lemur, Eulemur mongoz, at Anjamena in northwestern Madagascar, which provide baseline information on seasonal variation in the ecology, home range use and some aspects of the behavior of two neighboring groups. We monitored group size of nine groups in the study area and assessed them for seasonal variation. We present additional information collected during short-term surveys in other areas before and during the study for comparison. The study groups were small family units, and changes in group size were limited to births and emigrations of sexually mature progeny. In spite of clear seasonal changes in climate and vegetation, there is no variation in grouping patterns, so it is not possible to correlate variation in group size with seasonal variation of ecological variables. Comparison with ecological data from other field studies on lemurids reveals differences in food resource distribution in western forests versus other types of Malagasy forest. This distribution of food resources may predict home range size in mixed frugivorous–folivorous lemurs. Small home ranges, mainly in the West, could be correlated with a uniform distribution of food resources. Finally, we suggest that the dry season in the West may not present frugivorous–folivorous lemurs with major problems in finding an adequate food supply. This is supported by the lack of seasonal differences in ranging behavior of mongoose lemurs.  相似文献   

4.
Herrera  Bernal  Finegan  Bryan 《Plant and Soil》1997,191(2):259-267
A 28 yr old secondary lowland rain forest in Costa Rica was dominated by two tree species of contrasting ecologies, Vochysia ferruginea - a species typical of well-drained but infertile soils of high Al saturation, and Cordia alliodora, a species requiring soils of at least moderate fertility. The two species exhibited markedly different spatial distributions in the forest and we sought to determine whether or not these different distributions were related to variation in substrate conditions and the nutrient requirements of the two species. Two soil types were present: Ultisols (Typic Haplohumults) and Inceptisols (Typic Dystropepts) and topography was of low hills. The study formed part of an analysis of site quality for timber production in the two species and therefore used standard forestry methods for such analyses. 36 plots of 20 m×20 m were established using predetermined criteria of site uniformity, presence of at least four dominant trees of at least one of the study species, and absence of disturbance. The abundance (number of individuals 10 cm dbh) of each species was determined in each plot. Soil samples were taken in 27 of the 36 plots, 9 plots being considered to replicate conditions already sampled, and 14 soil chemical and physical variables were measured using standard methods. Foliar nutrient analyses were carried out for trees of both species with crowns fully exposed to sunlight, distributed across the gradient of soil conditions. Variations in species abundances were not related to soil type, but plots in which Vochysia ferruginea was more abundant tended to be on steeper slopes with soils of higher exchangeable acidity and lower concentrations of Mn; Cordia alliodora was more abundant on gentler topography where soils had much lower exchangeable acidity but higher Mn. Differences between the two species in foliar nutrient concentrations were marked and supported previous interpretations of their nutrient requirements; foliar nutrients of Vochysia ferruginea were typical of tree species of moist tropical forest on infertile soils, and those of Cordia alliodora typical of a species requiring more fertile soils. Factors such as the distributions of seed trees at site abandonment may affect the spatial distributions of tree species in secondary forests such as that studied. The relationships of the distributions of the two species to substrate variation, however, and their evidently different nutrient requirements, support the hypothesis that variation in the composition and structure of the forest studied is at least partially related to exchangeable acidity and its dominant cation, Al.  相似文献   

5.
6.
Photo-identification surveys conducted between 2002 and 2005 were used to determine dolphin home ranges and site fidelity within the Indian River Lagoon (IRL), Florida. The IRL was divided into six segments based on hydrodynamics and geographic features for purposes of characterization. Among the 615 dolphins with identifiable dorsal fins, 339 had ≥6 sightings and were used in segment and linear range analyses. The majority (98%) of dolphins were seen in ≤3 consecutive segments (331/339); of these, 44% (144/331) occurred in two segments, and 33% (109/331) in one segment. No dolphins were observed in all six segments. The largest number of dolphins was sighted in segment 1C (North Indian River). However, the highest density of dolphins was found in segment 2 (North-Central Indian River). Re-sighting rates for dolphins with ≥6 sightings ranged from 2.8 to 8.7 times observed. The mean linear home range varied from 22 to 54 km. Distributional analyses indicated that at least three different dolphin communities exist within the IRL: Mosquito Lagoon, and the North and South Indian River. No statistically significant correlations were found between the total number or density per km2 of dolphins and surface water area, salinity, or contaminant loads within segments of the lagoon. These results suggest that dolphins do not selectively avoid areas with relatively unfavorable water quality. IRL dolphins should be studied on smaller spatial scales than currently practiced, and potential anthropogenic impacts should be evaluated based on geographic partitioning.  相似文献   

7.
Soluble reactive phosphorus (SRP) transport/retention was determined at four sites in three rainforest streams draining La Selva Biological Station, Costa Rica. La Selva is located at the base of the last remaining intact rainforest transect from 30 m above sea level to 3000 m along the entire Caribbean slope of Central America. Steam SRP levels can be naturally high there due to regional, geothermal groundwater discharged at ambient temperature. Monitoring since 1988 has revealed distinctive long-term differences in background SRP and total P (TP) for three streams in close proximity, and identified the impact of ENSO (El Nino Southern Oscillation) events on SRP-enriched reaches. Mean interannual SRP concentrations (± standard deviation) were 89 ± 53μg/l in the Salto (1988–1996), 21 ± 39μg/l in the Pantano (1988–1998), and 26 ± 35μg/l in the Sabalo (1988–1996). After January, 1997 the separate upland-lowland contributions to discharge and SRP load were determined monthly in the Salto. SRP in Upper Salto was low (19 ± 8μg/l, 1997–2002) until enriched at␣the upland-lowland transition by regional groundwater. Mean SRP concentration in Lower␣Salto (108 ± 104μg/l) was typically highest February–April, the driest months, and lowest July–September, the wettest. SRP concentration was positively correlated to the inverse of discharge in Lower Salto when ENSO data were omitted (1992 and 1998–1999), but not in the Upper Salto, Pantano, or Sabalo. TP was positively correlated to the inverse of discharge in all three streams when ENSO data were omitted. High SRP springs and seeps along the Lower Salto contributed 36% of discharge but 85% of SRP export 1997–2001. Annual SRP flux from the total Salto watershed (1997–2001) averaged 2.9 kg/ha year, but only 0.6 kg/ha year from the Upper Salto. A dye tracer injection showed that pore water environments were distinctly different between Upper and Lower Salto. Upper Salto had high surface water–pore water exchange, high dissolved oxygen, low SRP, and low conductivity similar to surface water, and Lower Salto had low surface water–pore water exchange, low dissolved oxygen, high SRP, and high conductivity reflecting geothermal groundwater influence. SRP export from the Salto was controlled by regional groundwater transfer, which in similar volcanic settings could be a significant P source. However, ENSO events modified the SRP concentration in the Salto suggesting that long-term monitoring is required to understand underlying SRP dynamics and P flux to downstream communities.  相似文献   

8.
Abstract.
  • 1 Local dispersal and philopatric behaviour of the alpine grasshopper, Podisma pedestris, were studied at two sites in the Alpes Maritimes using a new mark—release—resight technique featuring marking in situ, and multiple resighting without handling. The time-consuming nature of the design was justified by the quantity and quality of the data yielded.
  • 2 Philopatry is defined independently of any concept of home range as a phenomenon by which movements over longer periods are less than would be expected by extrapolation of measures over shorter periods.
  • 3 By this definition, the grasshoppers are shown to exhibit philopatry. Nymphs comprise two heterogenous classes of those which move little and those which move considerable distances.
  • 4 Daily dispersal estimates were obtained from movements of 1055 nymphs and adults at one site, and of 593 adults at another.
  • 5 Differences are demonstrated in daily dispersal distances for age, sex and site combinations.
  • 6 Some differences in microhabitat preference were observed.
  • 7 The findings are compared with previous measurements of dispersal in this species, and the merits of the new technique are discussed.
  相似文献   

9.
10.
Herbicide-resistant rice cultivars allow selective weed control. A glufosinate indica rice has been developed locally. However, there is concern about weedy rice becoming herbicide resistant through gene flow. Therefore, assessment of gene flow from indica rice cultivars to weedy rice is crucial in Tropical America. A field trial mimicking crop–weed growing patterns was established to assess the rate of hybridization between a Costa Rican glufosinate-resistant rice line (PPT-R) and 58 weedy rice accessions belonging to six weedy rice morphotypes. The effects of overlapping anthesis, morphotype, weedy accession/PPT-R percentage, and the particular weedy accession on hybridization rates were evaluated. Weedy rice accessions with short overlapping anthesis (4–9 days) had lower average hybridization rates (0.1%) than long anthesis overlapping (10–14 days) accessions (0.3%). Hybridization also varied according to weedy rice morphotype and accession. Sativa-like morphotypes (WM-020, WM-120) hybridized more readily than intermediate (WM-023, WM-073, WM-121) and rufipogon-like (WM-329) morphotypes. No hybrids were identified in 11 of the 58 accessions analyzed, 21 accessions had hybridization rates from 0.01% to 0.09%, 21 had rates from 0.1% to 0.9%, and 5 had frequencies from 1% to 2.3%. Another field trial was established to compare the weedy rice-PPT-R F1 hybrids with their parental lines under noncompetitive conditions. F1 hybrids had a greater phenotypic variation. They had positive heterosis for vegetative trait and reproductive potential (number of spikelets and panicle length) traits, but negative heterosis for seed set. This study demonstrated the complexity of factors affecting hybridization rates in Tropical America and suggested that the phenotype of F1 hybrids facilitate their identification in the rice fields.  相似文献   

11.

Background and Aims

Plants are expected to maximize their net photosynthetic gains and efficiently use available resources, but the fundamental principles governing trade-offs in suites of traits related to resource-use optimization remain uncertain. This study investigated whether Acer saccharum (sugar maple) saplings could maximize their net photosynthetic gains through a combination of crown structure and foliar characteristics that let all leaves maximize their photosynthetic light-use efficiency (ɛ).

Methods

A functional–structural model, LIGNUM, was used to simulate individuals of different leaf area index (LAIind) together with a genetic algorithm to find distributions of leaf angle (LA) and leaf photosynthetic capacity (Amax) that maximized net carbon gain at the whole-plant level. Saplings grown in either the open or in a forest gap were simulated with Amax either unconstrained or constrained to an upper value consistent with reported values for Amax in A. saccharum.

Key Results

It was found that total net photosynthetic gain was highest when whole-plant PPFD absorption and leaf ɛ were simultaneously maximized. Maximization of ɛ required simultaneous adjustments in LA and Amax along gradients of PPFD in the plants. When Amax was constrained to a maximum, plants growing in the open maximized their PPFD absorption but not ɛ because PPFD incident on leaves was higher than the PPFD at which ɛmax was attainable. Average leaf ɛ in constrained plants nonetheless improved with increasing LAIind because of an increase in self-shading.

Conclusions

It is concluded that there are selective pressures for plants to simultaneously maximize both PPFD absorption at the scale of the whole individual and ɛ at the scale of leaves, which requires a highly integrated response between LA, Amax and LAIind. The results also suggest that to maximize ɛ plants have evolved mechanisms that co-ordinate the LA and Amax of individual leaves with PPFD availability.  相似文献   

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