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Different Elevations (different + elevation)
Selected AbstractsElevational gradients, area and tropical island diversity: an example from the palms of New GuineaECOGRAPHY, Issue 3 2004Steven Bachman The factors causing spatial variation in species richness remain poorly known. In this study, factors affecting species richness of palms (Palmae/Arecaceae) were studied along the elevational gradient of New Guinea. Interpolated elevational ranges were calculated from a database of all known collections for 145 species in 32 genera. The amount of land area at different elevations greatly affects the species richness gradient. If assessed in equal-elevation bands species richness appears to decline monotonically, but when assessed in equal-area bands species richness shows a pronounced mid-elevation peak, due to the large proportion of lowlands in New Guinea. By randomising species ranges within the total elevational gradient for palms and accounting for area, we found the mid-elevation peak to be consistent with a mid-domain effect caused by the upper and lower limits to palm distribution. Our study illustrates the importance of accounting for area in macroecological studies of richness gradients and introduces a novel yet simple method for doing this through the use of equal-area bands. Together, the effect of area and the mid-domain effect explain the majority of variation in species richness of New Guinea palms. We support calls for the multivariate assessment of the mid-domain effect on an equal footing with other potential explanations of species richness. [source] LATITUDINAL VARIATION IN SPECIATION MECHANISMS IN FROGSEVOLUTION, Issue 2 2010Xia Hua Speciation often has a strong geographical and environmental component, but the ecological factors that potentially underlie allopatric and parapatric speciation remain understudied. Two ecological mechanisms by which speciation may occur on geographic scales are allopatric speciation through niche conservatism and parapatric or allopatric speciation through niche divergence. A previous study on salamanders found a strong latitudinal pattern in the prevalence of these mechanisms, with niche conservatism dominating in temperate regions and niche divergence dominating in the tropics, and related this pattern to Janzen's hypothesis of greater climatic zonation between different elevations in the tropics. Here, we test for latitudinal patterns in speciation in a related but more diverse group of amphibians, the anurans. Using data from up to 79 sister-species pairs, we test for latitudinal variation in elevational and climatic overlap between sister species, and evaluate the frequency of speciation via niche conservatism versus niche divergence in relation to latitude. In contrast to salamanders, we find no tendency for greater niche divergence in the tropics or for greater niche conservatism in temperate regions. Although our results support the idea of greater climatic zonation in tropical regions, they show that this climatic pattern does not lead to straightforward relationships between speciation, latitude, and niche evolution. [source] Responses of riparian plants to flooding in free-flowing and regulated boreal rivers: an experimental studyJOURNAL OF APPLIED ECOLOGY, Issue 6 2002M. E. Johansson Summary 1The long history of river regulation has resulted in extensively changed ecosystem structures and processes in rivers and their associated environments. This fact, together with changing climatic and hydrological conditions, has increased the need to recover the natural functions of rivers. To develop guidelines for river restoration, comparative ecological experiments at contrasting water-level regimes are needed. We compared growth and survival of transplanted individuals of four riparian plant species (Betula pubescens, Carex acuta, Filipendula ulmaria and Leontodon autumnalis) over 2 years on four free-flowing and four regulated riverbank sites in northern Sweden. The species were chosen as representatives of dominating life-forms and species traits on different elevations of the riverbanks. 2In Betula and Filipendula, mean proportional growth rates were significantly higher at free-flowing sites than at regulated sites, whereas no consistent differences between free-flowing and regulated sites were found in Carex and Leontodon. Differences among species were generally in accordance with natural distribution patterns along riverbank elevation gradients and with experimental evidence on flooding tolerance, although plants of all species survived and even showed positive growth rates on elevations below their natural range of occurrence. 3Partial least squares regression was used to relate plant performance (growth and survival) to duration, frequency and timing of flooding at the different sites. Flood duration and frequency typically reduced performance in all species and during all time periods, although to various degrees. Flood events early in the experiment determined the outcome to a high degree at all sites. Variables indicating a regulated regime were mostly negatively related to plant performance, whereas free-flowing regime variables were positively related to plant performance. 4We used two of the regression models generated from our data with an acceptably high predictive power to simulate a hypothetical re-regulation scenario in run-of-river impoundments. With an overall reduction in flooding duration and frequency of 50,75%, plant performance of Filipendula at low riverbank elevations showed predicted increases of about 20,30%, levelling off to zero at the highest elevations. Reductions in summer floods represented about one-third to half of this increase. 5We conclude that for a range of species individual plant performance is clearly reduced on banks of impoundments and storage reservoirs due to changes in the water-level regime. Furthermore, our model simulation suggests that rather substantial reductions of flood duration and frequency are needed to improve plant performance on riverbanks upstream from dams in impounded rivers. River restoration principles should, however, be based on a combination of experimental data on plant performance of individual species and observed long-term changes in plant communities of regulated rivers. Consequently, successful re-regulation schemes in boreal rivers should include both reductions of summer and winter floods as well as re-introduced spring floods. [source] Differential performance of reciprocal hybrids in multiple environmentsJOURNAL OF ECOLOGY, Issue 6 2008Sarah Kimball Summary 1Closely related taxa may be maintained as distinct species by a variety of reproductive isolating mechanisms. These include: inability to produce hybrid offspring, endogenous selection against hybrids in the form of genomic incompatibilities, and exogenous selection observable in genotype-by-environment interactions. To understand the relative importance of these three isolating mechanisms, we performed hand-pollination and reciprocal transplant experiments in a natural plant hybrid zone. 2We measured reproductive isolation by making crosses between two parent species of Penstemon and naturally occurring hybrids. Inclusion of reciprocal hybrid crosses allowed us to determine whether fitness components differed depending on the identity of the mother. 3Hybrid performance was evaluated in the greenhouse and in a reciprocal transplant experiment in the field. We measured fruit set, seed set, seed weight, time required for fruits to mature and seedling growth for potted plants. To test for exogenous isolation, we planted pure parents, reciprocal F1 hybrids and later generation hybrids in a reciprocal transplant experiment, and measured survival. 4On average, interspecific crosses produced as many seeds as conspecific crosses. Hybrid performance was also equal to or greater than parents in all environments, including the greenhouse and all field gardens, indicating a lack of endogenous isolation. Parent species and reciprocal F1 hybrids differed in many traits measured. In each field garden, the hybrid with the native cytoplasm had a higher survival rate, suggesting local adaptation to different elevations. 5Synthesis. Exogenous factors that differ along elevational gradients can be more important than intrinsic genetic incompatibilities in determining the fitness of plant hybrids. Our results illustrate the importance of studying hybrid performance in multiple environments and in generating reciprocal hybrids to test for isolating mechanisms in natural hybrid zones. [source] Late Quaternary deglacial history of the Mérida Andes, Venezuela,JOURNAL OF QUATERNARY SCIENCE, Issue 7-8 2005Nathan D. Stansell Abstract Radiocarbon-dated sediment cores from seven lakes and two bogs spanning the Cordillera de Mérida in the Venezuelan Andes were used to identify and date the regional history of late Pleistocene and Holocene glacial activity. Coring sites were selected at different elevations across a pronounced rain shadow from southeast (wet) to northwest (dry). Sediment lithostratigraphy and magnetic susceptibility, in conjunction with AMS radiocarbon dates on macrofossils and charcoal, were used to constrain deglaciation. The local expression of the Last Glacial Maximum occurred between 22,750 and 19,960,cal.,yr,BP. On the wetter southeastern side of the Cordillera de Mérida, glaciers had significantly retreated by 15,700,cal.,yr,BP, followed by several minor glacial advances and retreats between 14,850 and 13,830,cal.,yr,BP. At least one major glacial readvance occurred between 13,830 and 10,000,cal.,yr,BP in the wetter southeastern sector of the region. The drier northwest side of the Cordillera de Mérida records initial glacial retreat by 14,240,cal.,yr,BP. Multiple sites on both sides of the Mérida Andes record a further phase of extensive deglaciation approximately 10,000,cal.,yr,BP. However, the north-northwest facing Mucubají catchment remained partially glaciated until ca. 6000,cal.,yr,BP. Deglacial ages from the Venezuelan Andes are consistently younger than those reported from the Southern Hemisphere Andes, suggesting an inter-hemispheric deglacial lag in the northern tropics of the order of two thousand years. Copyright © 2005 John Wiley & Sons, Ltd. [source] Temperature Stress Tolerance of Conifer Seedlings after Exposure to UV-B RadiationPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 5 2005Sylvia J. L'Hirondelle ABSTRACT Ground-level UV-B radiation has increased globally due to a thinning stratospheric ozone layer. We estimated the effects of increased UV-B on 10 conifer species grown in chambers in greenhouses with supplemental UV-B. Species were selected from a wide range of geographic locations. Plant material of two ages (germinants, first growing season; seedlings, second season) were exposed to three levels of UV-B from ambient (at Victoria, B.C., Canada) to three times ambient (12 kJ m,2 d,1) for up to four months. Frost hardiness and heat tolerance of shoots were estimated from changes in chlorophyll fluorescence after exposure to test temperatures. There were no significant differences among seed sources from different elevations in their response to temperature stresses. When UV-B increased above the ambient level, three species (interior Douglas-fir, Engelmann spruce, and interior lodgepole pine) increased in frost hardiness and four (grand fir, interior spruce, yellow-cedar, and western redcedar) decreased. Two species (western redcedar and western hemlock) increased in heat tolerance when UV-B increased to the 12 kJ level. The main differences in stress tolerance were between the triple ambient and the other two treatments, not between ambient and double ambient, suggesting that any changes in UV-B would have to be large to elicit physiological changes in conifer seedlings. [source] Life-history monographs of Japanese plants.PLANT SPECIES BIOLOGY, Issue 3 20079: Helonias orientalis (Thunb.) N. Tanaka (Liliaceae) Abstract The life-history characteristics of Helonias orientalis (Liliaceae) are described. The genus Helonias (Liliaceae), which includes Heloniopsis and Ypsilandra, is one of the representative members of the so-called Arcto-Tertiary Geoflora, with typical disjunct geographical ranges in eastern North America and eastern Asia, including the Japanese Islands to inland China and the Himalayan Mountains. The seasonal growth patterns of this evergreen perennial are most unique, showing different replacement patterns in foliage leaves, which are formed during two different seasons, once in late spring and again in late summer to autumn. Flowering occurs at different times of the year in populations that are located at different elevations. Lowland populations flower in late March to early April, whereas montane and subalpine,alpine populations bear flowers in early to mid-summer, June to August. Another outstanding feature of this species is that it produces tiny plantlets at the tips of the oldest (3-year-old) foliage leaves just before decaying. Survival rates of plantlets (ramets) are obviously much higher than that of the exceedingly minute seedlings (gamets), especially on the dark shady forest floor. Thus, populations in closed woodland habitats are primarily maintained by plantlets, that is, vegetative plantlet formation. The cost of seed production is dramatically higher in the subalpine,alpine populations compared with those of the lowland populations. [source] Restoring Tree Islands in the Everglades: Experimental Studies of Tree Seedling Survival and GrowthRESTORATION ECOLOGY, Issue 2 2008Arnold G. Van Der Valk Abstract In May 2004, 400 tree seedlings of seven different species found on tree islands in the Florida Everglades were planted at different elevations along five transects on eight newly constructed tree islands, four with and four without limestone cores. Seedlings suffered between 40 and 85% mortality during the first 120 days, the period with the lowest water levels. Ilex cassine L., Salix caroliniana Michx., Chrysobalanus icaco L., and Annona glabra had the highest number of surviving seedlings, whereas Magnolia virginiana L., Myrica cerifera L., and Acer rubrum L. had the fewest. During the remainder of the study, water levels were mostly higher and sometimes covered the entire islands for months at a time. After 220 days, nearly all seedlings of M. virginiana and My. cerifera had died. At the end of the study, seedlings of I. cassine and A. glabra had the highest survivorship rates. Seedling biomass of C. icaco and I. cassine was greatest at the highest elevations, whereas seedlings of A. glabra had similar biomass at all elevations. Seedling survivorship was not statistically different between islands with and without limestone cores; however, when seedlings of all species were combined, island core type was significantly different for aboveground biomass, seedling height, and canopy width. Because of the higher survivorship under both low and high water conditions, A. glabra, I. cassine, and S. caroliniana are the most suitable species for establishing tree species on restored tree islands in the Everglades. [source] Seed dispersal in a polder after partial tidal restoration: Implications for salt-marsh restorationAPPLIED VEGETATION SCIENCE, Issue 1 2008Armel Dausse Abstract Question: The vegetation in a polder after partial tidal restoration does not resemble the targeted salt-marsh vegetation. Is this difference in vegetation due to lack of dispersal or unsuitable abiotic conditions? What could be done for a better restoration of the site? Location: Northwestern France. Methods: Seeds were trapped at the single inlet of the polder with a 200- , m mesh net to estimate inputs of seeds from the bay. In parallel, seed dispersal was studied in the polder by placing Astroturf® seed traps on the surface of the sediment at three different elevations in three distinct areas. Abiotic conditions such as flooding frequency, water table level and soil salinity were monitored. Results: All but one species from the adjacent salt marshes were trapped at the inlet. Not all of these species were on the seed traps inside the polder. Seed dispersal was not homogeneous in the polder and seed trap content mostly discriminated in function of their elevation. Salinity and water logging at the bottom of the slope were very high compared to tolerance of most halophytes but decreased rapidly higher up the slope. Conclusions: The development of salt marsh target species is highly restricted by limited hydrochory inside the polder but also by unfavourable soil conditions induced by the actual hydrological regime. Halophytes are excluded at the bottom of the slope by abiotic conditions and out-competed by sub-halophytes higher up. In order to restore salt marsh vegetation inside the polder, a larger opening should be induced in order to increase the flooded surface, and diminish water logging and flooding frequencies. [source] Response to cutting of Larrea divaricata and L. cuneifolia in ArgentinaAPPLIED VEGETATION SCIENCE, Issue 1 2002E. Martinez Carretero Abstract. The response of Larrea divaricata and L. cuneifolia to cutting stems 0,20 cm above the ground was studied in the arid piedmont area west of Mendoza, Argentina. The species occur at different elevations and in vegetation zones: L. cuneifolia < 1250 m; L. divaricata between 1250 and 2500 m. Four treatments with 10 replicates were analysed in randomly chosen plants: cut at ground level with lopping shears; cut at ground level with a pick; cut at 10 cm with lopping shears; and cut at 20 cm with lopping shears. The initial and final height, volume, and dry matter (above- and below-ground) were determined. The relation between volume and initial and final dry matter and height was analysed through a factorial MANOVA (p < 0,05), and the functional relation between volume, dry matter and height was estimated by adjusting a regression model. In both species, maximum recovery was reached when cut with shears, and predicted recovery (turnover) was 17-18 yr. In the two last treatments height was a useful predictor of dry matter. L. divaricata -dominated plots have a lower biomass, growth rate, and allocation to stems and root than L. cuneifolia -dominated plots. Regrowth following clipping on an area of 3,10 ha, is sufficient to support the annual needs (cooking and heating) of one family. [source] A long-term record of Nothofagus dominance in the southern Andes, ChileAUSTRAL ECOLOGY, Issue 1 2005William Pollmann Abstract The general model of regeneration dynamics in Nothofagus forests of southern South America could have value in community ecology if predictive relationships between disturbance history, functional traits and site attributes could be identified. Examined here is the proposal that on favourable sites shade-intolerant Nothofagus are likely not to survive in competition with shade-tolerant, broad-leaved evergreen taxa of temperate rain forests, and persistence, thus, is dependent on periodic coarse-scale disturbance. Comparison of stand dynamics of three old-growth Nothofagus forests at different elevations in the southern Andes, Chile where deciduous Nothofagus alpina dominates the upper canopy, and examination of the life history trade-offs of this variation were made. Stem density of all stems ,5.0 cm d.b.h. was 233,303 stems per hectare, and basal area was 123.9,171.0 m2ha,1. Maximum lifespan of N. alpina was found to be greater than ca 640 years, exceeding all previously reported ages for this species in the region. Forests had a stable canopy composition for this long-term, but some appeared to lack effective regeneration of N. alpina in recent years. Regeneration of N. alpina was generally greater in disturbed stands and higher elevation than in undisturbed stands and at lower elevation. Recruitment emerged to be strongly affected by competitive over- and understorey associates. There was a gradient of increasing dependence of N. alpina on disturbance towards the more productive end of the environment gradients, and hence less dependence of N. alpina on disturbance for its regeneration towards higher elevation. The study confirms that changes in forest composition may be explained by processes occurring in accordance with the predictions of the existing model of Nothofagus regeneration dynamics, providing stronger evidence specifically directed at mid-tolerant N. alpina, and by factoring out regeneration dynamics on favourable sites. Thus, for N. alpina, trait differences probably contribute to the competitive advantage over its associates in productive habitats, and may be linked to small-to-intermediate-sized disturbances which inevitably occur as older trees die, enabling N. alpina to persist in forests and therefore maintain species coexistence for the long-term. [source] Holocene Floral and Faunal Remains Revealed Concealed Neotectonic Disturbance (Saria Tal, Kumaun Himalaya, India)ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 1 2010Asha GUPTA Abstract: Palynological and paleontological investigations supported by the radiocarbon dates of the lacustrine sediments of two profiles from the temperate lake Saria Tal, in Nairn Tal District, Kumaun Himalaya, have revealed the presence of a concealed fold at the region. The profile from bore cores represents the upper part of the Late Holocene and the profile from exposed sections from the Middle Holocene to the over middle part of the Late Holocene. The data generated from different investigations have uniformly indicated that the former profile represents normal superposition, while the latter represents the reverse order. The contemporary pollen as well as moüuscan zones of both profiles are situated at different elevations but consist of similar bioremains , indicating continuation of the same strata in two profiles. The presence of reverse order of superposition, continuation of the same strata in two profiles at different elevations, and the orientation of biozones, have indicated that the revealed folding is of syncline type. The present study has also given an idea about the origin of this lake. [source] | |||||||||||||