Home About us Contact
|
Home About us Contact | ||
|
|
||
Alpine Species (alpine + species)
Selected AbstractsEnvironmental warming increases invasion potential of alpine lake communities by imported speciesGLOBAL CHANGE BIOLOGY, Issue 11 2005Angela M. Holzapfel Abstract Global warming increasingly pressures species to show adaptive migratory responses. We hypothesized that warming increases invasion of alpine lakes by low-elevation montane zooplankton by suppressing native competitors and predators. This hypothesis was tested by conducting a two-factor experiment, consisting of a warming treatment (13 vs. 20°C) crossed with three invasion levels (alpine only, alpine+montane, montane only), in growth chambers over a 28-day period. Warming significantly reduced total consumer biomass owing to the decline of large alpine species, resulting in greater autotrophic abundance. Significant temperature-invasion interactions occurred as warming suppressed alpine zooplankton, while stimulating certain imported species. Herbivorous invaders suppressed functionally similar alpine species while larger native omnivores reduced invasion by smaller taxa. Warming did not affect total invader biomass because imported species thrived under ambient and warmed alpine conditions. Our findings suggest that the adaptability of remote alpine lake communities to global warming is limited by species dispersal from lower valleys, or possibly nearby warmer alpine ponds. [source] A regional impact assessment of climate and land-use change on alpine vegetationJOURNAL OF BIOGEOGRAPHY, Issue 3 2003Thomas Dirnböck Abstract Aim, Assessing potential response of alpine plant species distribution to different future climatic and land-use scenarios. Location, Four mountain ranges totalling 150 km2 in the north-eastern Calcareous Alps of Austria. Methods, Ordinal regression models of eighty-five alpine plant species based on environmental constraints and land use determining their abundance. Site conditions are simulated spatially using a GIS, a Digital Terrain Model, meteorological station data and existing maps. Additionally, historical records were investigated to derive data on time spans since pastures were abandoned. This was then used to assess land-use impacts on vegetation patterns in combination with climatic changes. Results, A regionalized GCM scenario for 2050 (+ 0.65 °C, ,30 mm August precipitation) will only lead to local loss of potential habitat for alpine plant species. More profound changes (+ 2 °C, ,30 mm August precipitation; + 2 °C, ,60 mm August precipitation) however, will bring about a severe contraction of the alpine, non-forest zone, because of range expansion of the treeline conifer Pinus mugo Turra and many alpine species will loose major parts of their habitat. Precipitation change significantly influences predicted future habitat patterns, mostly by enhancing the general trend. Maintenance of summer pastures facilitates the persistence of alpine plant species by providing refuges, but existing pastures are too small in the area to effectively prevent the regional extinction risk of alpine plant species. Main conclusions, The results support earlier hypotheses that alpine plant species on mountain ranges with restricted habitat availability above the treeline will experience severe fragmentation and habitat loss, but only if the mean annual temperature increases by 2 °C or more. Even in temperate alpine regions it is important to consider precipitation in addition to temperature when climate impacts are to be assessed. The maintenance of large summer farms may contribute to preventing the expected loss of non-forest habitats for alpine plant species. Conceptual and technical shortcomings of static equilibrium modelling limit the mechanistic understanding of the processes involved. [source] Natural avalanche disturbance shapes plant diversity and species composition in subalpine forest beltJOURNAL OF VEGETATION SCIENCE, Issue 5 2007Christian Rixen Abstract Background: Disturbances by avalanches have created unique habitats for animals and plants in subalpine ecosystems worldwide, but at the same time avalanches can pose a major threat to humans. Thus, avalanches are suppressed by means of avalanche barriers to protect settlements and infrastructures in populated areas of the European Alps. As a consequence, the disturbance regime in avalanche tracks has fundamentally changed. Methods: In the present study we address ecological consequences of avalanche suppression on plant diversity. We analysed plant diversity and species composition in recent and old avalanche tracks with and without avalanche suppression and in undisturbed adjacent forests at high and low elevations. Results: The number of species was higher in both active and inactive avalanche tracks as compared to undisturbed subalpine forest. The species composition indicated a wider range of ecological niches in active than in inactive avalanche tracks. The vegetation from active tracks showed lower indicator values for temperature and nitrogen availability. The proportion of alpine species was lower in formerly active tracks. Conclusions: The conditions that exist in active avalanche tracks increase plant diversity in relation to undisturbed forest. In the few decades following avalanche suppression, species composition changes in tracks from which avalanches have been excluded. Continued suppression of avalanche disturbance may lead to a decline in plant and habitat diversity. Avalanche disturbance can exert an important influence on the biodiversity of subalpine forests and provide important habitats. Anthropogenic changes in the natural regime of avalanche disturbance are likely to contribute significantly to future landscape changes in subalpine forests. [source] Substantial genetic substructuring in southeastern and alpine Australia revealed by molecular phylogeography of the Egernia whitii (Lacertilia: Scincidae) species groupMOLECULAR ECOLOGY, Issue 5 2005DAVID G. CHAPPLE Abstract Palaeoclimatic events and biogeographical processes since the mid-Tertiary are believed to have strongly influenced the evolution and distribution of the terrestrial vertebrate fauna of southeastern Australia. We examined the phylogeography of the temperate-adapted members of the Egernia whitii species group, a group of skinks that comprise both widespread low- to mid-elevation (E. whitii) and montane-restricted species (Egernia guthega, Egernia montana), in order to obtain important insights into the influence of past biogeographical processes on the herpetofauna of southeastern Australia. Sequence data were obtained from all six temperate-adapted species within the E. whitii species group, and specifically from across the distributional ranges of E. whitii, E. guthega and E. montana. We targeted a fragment of the ND4 mitochondrial gene (696 bp) and analysed the data using maximum likelihood and Bayesian methods. Our data reveal a deep phylogeographical break in the east Gippsland region of Victoria between ,northern' (Queensland, New South Wales, Australian Capital Territory) and ,southern' (Victoria, Tasmania, South Australia) populations of E. whitii. This divergence appears to have occurred during the late Miocene,Pliocene, with the Gippsland basin possibly forming a geographical barrier to dispersal. Substantial structuring within both the ,northern' and the ,southern' clades is consistent with the effects of Plio,Pleistocene glacial-interglacial cycles. Pleistocene glacial cycles also appear to have shaped the phylogeographical patterns observed in the alpine species, E. guthega and E. montana. We used our results to examine the biogeographical process that led to the origin and subsequent diversification of the lowland and alpine herpetofauna of southeastern Australia. [source] Alpine flora dynamics , a critical review of responses to climate change in the Swedish Scandes since the early 1950sNORDIC JOURNAL OF BOTANY, Issue 4 2010Leif Kullman Reports about changes of alpine plant species richness over the past 60 years in the Swedish Scandes are reviewed, synthesized and updated with data from recent reinventories. Methodologically, this endeavour is based on resurveys of the floristic composition on the uppermost 20 m of four high-mountain summits. The key finding is that the species pool has increased by 60,170% since the 1950s and later. Some of the invading species are new to the alpine tundra, with more silvine and thermophilic properties than the extant alpine flora. Not a single species of the original flora has disappeared from any of the summits. This circumstance is discussed in perspective of widespread expectations of pending temperature-driven extinction of alpine species in an alleged future warmer climate. These progressive changes coincided with distinct warming (summer and winter) since the late 1980s. During a short cooler period (1974,1994), the species numbers decreased and the upper elevational limits of some ground cover species descended. Thus, discernible responses, concurrent with both warming and cooling intervals, sustain a strong causal link between climate variability and alpine plant species richness. Methodologically, plot-less revisitation studies of the present kind are beset with substantial uncertainties, which may overstate floristic changes over time. However, it is argued here that carefully executed and critically interpreted, no other method can equally effectively sense the earliest phases of plant invasions into alpine vegetation. [source] Short-Term Changes in Heat Tolerance in the Alpine Cushion Plant Silene acaulis ssp. excapa [All.] J. Braun at Different AltitudesPLANT BIOLOGY, Issue 6 2000G. Neuner Abstract: The habit of cushion growth positively affects plant temperature but at the same may increase the risk of occasional overheating. In order to determine the adaptive response to short-term heat stress, we exposed S. acaulis cushions at field sites to controlled heat treatments using infrared lamps. Natural diurnal changes in heat tolerance were monitored at alpine sites and at a site distinctly below the natural distribution boundary, where higher temperatures were expected. The range of heat tolerance limits in summer, 45.5 - 54.5 °C (9 K), exceeded that reported for other alpine species (0.1 - 5 K) and even that for total seasonal changes (5 - 8 K). Heat tolerance either increased or decreased on most days (80 %). The maximum diurnal increase was + 4.7 K. Under the experimental conditions heat hardening started at leaf temperatures around 30 °C and proceeded at mean rates of 1.0 ± 0.5 K/h. The onset of functional disturbances in photosystem II also occurred at 30 °C. Heating rates exceeding those naturally found above 30 °C (> 10 K/h) appeared to retard heat hardening. During summer average leaf temperature maxima were 12.4 K (600 m) and 13.0 K (1945 m) higher than air temperature which corroborates the heat trapping nature of cushion plants. At 600 m, as compared to 1945 m, cushions experienced significantly higher leaf temperature maxima (+ 8.8 K) and exceeded 30 °C on most days (80 %). This resulted in a significantly higher heat tolerance (LT50) at 600 m (51.7 ± 0.2 °C) than at 1945 m (49.8 ± 0.2 °C). The fast short-term changes of heat tolerance in summer help S. acaulis to cope with the occasional diurnal short-term heat stress associated with cushion growth. [source] Assessing the dominance of Phleum pratense cv. climax, a species commonly used for ski trail restorationAPPLIED VEGETATION SCIENCE, Issue 2 2009Francis Isselin-Nondedeu Abstract Questions: (1) Are some species used for ski trail restoration too dominant to allow native species to re-establish? (2) What plant traits can be used to predict which species are good competitors? We tested the hypothesis that limited native species establishment on ski trails is caused by (1) the dominance of Phleum pratense cv. climax (PPC) and (2) the asymmetry of competitive interactions. Location: Sub-alpine area in the northern French Alps. Methods: PPC was cultivated outdoors over 2 years with 15 alpine species in a systematic design with high- and low-nutrient soil conditions. For each species relative survival, competitive performance and relationships with plant traits were measured. Results: PPC exerted strong dominance on most of its neighbouring species. Survival performance of Anthyllis vulneraria, Luzula sudetica and Lotus alpinus were dramatically reduced. Results of above-ground competition showed that species were trapped in asymmetric competition. Festuca rubra, Trifolium repens, Alchemilla xanthochlora, Trifolium pratense and Plantago alpina best counteracted PPC. Below-ground competition was more symmetric, particularly at the high nutrient level. Plant traits such as biomass, canopy size and specific leaf area were positively correlated with competitive performance of the species. Conclusion: The study has implications for the management of restored ski trails since PPC may hinder the establishment of native sub-alpine species. Consequently, recommendations should focus on (1) maintaining a low proportion or decreasing the proportion of PPC seeds in the revegetation mix and (2) reducing soil fertilization. Plant traits and competition experiments can help to predict changes in restored grasslands. [source] | |||||||||||||