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Alpine Ecosystems (alpine + ecosystem)
Selected AbstractsWater Sources of Dominant Species in Three Alpine Ecosystems on the Tibetan Plateau, ChinaJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 3 2008De-Yu Duan Abstract Plant water sources were estimated by two or three compartment linear mixing models using hydrogen and oxygen isotope (,D and ,18O) values of different components such as plant xylem water, precipitation and river water as well as soil water on the Tibetan Plateau in the summer of 2005. Four dominant species (Quercus aquifolioides, Pinus tabulaeformis, Salix rehderiana and Nitraria tangutorum) in three typical ecosystems (forest, shrub and desert) were investigated in this study. Stable isotope ratios of the summer precipitations and the soil water presented variations in spatial and temporal scales. ,18O values of N. tangutorum xylem water were constant in the whole growth season and very similar to those of deep soil water. Water sources for all of the plants came from both precipitations and soil water. Plants switched rapidly among different water sources when environmental water conditions changed. Rainwater had different contributions to the plants, which was influenced by amounts of precipitation. The percentage of plant xylem water derived from rainwater rose with an increase in precipitation. Water sources for broad-leaved and coniferous species were different although they grew in the same environmental conditions. For example, the broad-leaved species Q. aquifolioides used mainly the water from deep soil, while 92.5% of xylem water of the coniferous species P. tabulaeformis was derived from rainwater during the growth season. The study will be helpful for us to fully understand responses of species on the Tibetan Plateau to changes in precipitation patterns, and to assess accurately changes of vegetation distribution in the future. [source] Variable reproductive effort for two ptarmigan species in response to spring weather in a northern alpine ecosystemJOURNAL OF AVIAN BIOLOGY, Issue 3 2010Scott Wilson Predicting how animal populations respond to climate change requires knowledge of how species traits influence the response of individuals to variation in anuual weather. Over a four-year study with two warm and two cold years, we examined how sympatric rock ptarmigan Lagopus muta and white-tailed ptarmigan L. leucura in the southern Yukon Territory respond to spring weather in terms of breeding phenology and the allocation of reproductive effort. The onset of breeding was approximately synchronous; for each one-degree rise in spring temperature, mean breeding dates of rock and white-tailed ptarmigan advanced by about 2.7 and 4 days respectively. Although onset of breeding was similar, the two species differed in their reproductive effort. As breeding was delayed, average first clutch sizes of rock ptarmigan declined from 9.4 to 5.8 eggs over the breeding period, while those of white-tailed ptarmigan only declined from an average of 7.8 to 6.8. Rock ptarmigan were also less likely to re-nest if their first clutch was lost to predators and as a consequence they had shorter breeding seasons. White-tailed ptarmigan produced about 25% more offspring annually than rock ptarmigan and contributed more young through re-nesting. While white-tailed ptarmigan had higher annual reproductive output, adult rock ptarmigan had a 20,25% higher annual survival rate, which may indicate a reproduction,survival trade-off for the two species. These results show that even within the same location, closely related species can differ in how they allocate effort as environmental conditions fluctuate. [source] Carbon flux from plants to soil: roots are a below-ground source of phenolic secondary compounds in an alpine ecosystemJOURNAL OF ECOLOGY, Issue 3 2008Courtney L. Meier Summary 1Phenolics are an important, biologically reactive component of the carbon (C) pool that moves from plants to soil. Once in soil, phenolics can regulate plant,soil feedbacks because of their influence on soil nitrogen biogeochemistry. 2Roots are a largely overlooked potential source of below-ground phenolic C. We examined phenolic fluxes from plants to soil in an alpine ecosystem, where phenolics are associated with slow rates of nutrient cycling. Using a phenolic-rich forb (Acomastylis rossii) and a grass with low tissue phenolics (Deschampsia caespitosa), we asked whether leaves, leaf litter or roots are the dominant source of soil phenolics during the growing season. We also determined whether the composition of root-derived phenolics differed from that of leaf litter. 3Both labile low molecular weight phenolics and tannins disappeared from A. rossii leaf litter over the winter. Evidence from this study and others indicates litter phenolics are not a significant source of labile C for soil microbes throughout the growing season. 4In the field, levels of phenolics were higher under A. rossii canopies than under D. caespitosa canopies throughout the growing season. We also estimated significantly higher phenolic fluxes into soils for A. rossii than for D. caespitosa in the glasshouse. Field and glasshouse results suggest roots are an important source of these compounds. Furthermore, the phenolic chemistry of roots was different from that of leaf litter, indicating that the effects of root phenolics on soil processes and neighbouring plant growth may differ from those associated with leaves. 5Synthesis. Based on our results, labile phenolic inputs from roots are likely to have a more important influence on soil nutrient dynamics during the alpine growing season than phenolic inputs from leaf litter. We suggest that roots may be the dominant input of labile phenolics to soil during the growing season in other ecosystems with seasonal patterns of plant growth and senescence. These observations are critical to our understanding of how phenolic-rich species may interact with soil microbes to influence soil nutrient cycling and shape the soil resource environment. [source] Geochemistry and source waters of rock glacier outflow, Colorado Front RangePERMAFROST AND PERIGLACIAL PROCESSES, Issue 1 2006M. W. Williams Abstract We characterize the seasonal variation in the geochemical and isotopic content of the outflow of the Green Lake 5 rock glacier (RG5), located in the Green Lakes Valley of the Colorado Front Range, USA. Between June and August, the geochemical content of rock glacier outflow does not appear to differ substantially from that of other surface waters in the Green Lakes Valley. Thus, for this alpine ecosystem at this time of year there does not appear to be large differences in water quality among rock glacier outflow, glacier and blockslope discharge, and discharge from small alpine catchments. However, in September concentrations of Mg2+ in the outflow of the rock glacier increased to more than 900,µeq,L,1 compared to values of less than 40,µeq,L,1 at all the other sites, concentrations of Ca2+ were greater than 4,000,µeq,L,1 compared to maximum values of less than 200,µeq,L,1 at all other sites, and concentrations of SO reached 7,000,µeq,L,1, compared to maximum concentrations below 120,µeq,L,1 at the other sites. Inverse geochemical modelling suggests that dissolution of pyrite, epidote, chlorite and minor calcite as well as the precipitation of silica and goethite best explain these elevated concentrations of solutes in the outflow of the rock glacier. Three component hydrograph separation using end,member mixing analysis shows that melted snow comprised an average of 30% of RG5 outflow, soil water 32%, and base flow 38%. Snow was the dominant source water in June, soil water was the dominant water source in July, and base flow was the dominant source in September. Enrichment of ,18O from ,10, in the outflow of the rock glacier compared to ,20, in snow and enrichment of deuterium excess from +,17.5, in rock glacier outflow compared to +,11, in snow, suggests that melt of internal ice that had undergone multiple melt/freeze episodes was the dominant source of base flow. Copyright © 2005 John Wiley & Sons, Ltd. [source] ALPINE AREAS IN THE COLORADO FRONT RANGE AS MONITORS OF CLIMATE CHANGE AND ECOSYSTEM RESPONSE,GEOGRAPHICAL REVIEW, Issue 2 2002MARK W. WILLIAMS ABSTRACT. The presence of a seasonal snowpack in alpine environments can amplify climate signals. A conceptual model is developed for the response of alpine ecosystems in temperate, midlatitude areas to changes in energy, chemicals, and water, based on a case study from Green Lakes Valley,Niwot Ridge, a headwater catchment in the Colorado Front Range. A linear regression shows the increase in annual precipitation of about 300 millimeters from 1951 to 1996 to be significant. Most of the precipitation increase has occurred since 1967. The annual deposition of inorganic nitrogen in wetfall at the Niwot Ridge National Atmospheric Deposition Program site roughly doubled between 1985,1988 and 1989,1992. Storage and release of strong acid anions, such as those from the seasonal snowpack in an ionic pulse, have resulted in episodic acidification of surface waters. These biochemical changes alter the quantity and quality of organic matter in high-elevation catchments of the Rocky Mountains. Affecting the bottom of the food chain, the increase in nitrogen deposition may be partly responsible for the current decline of bighorn sheep in the Rocky Mountains. [source] Do pipits use experimentally supplemented rich sources of calcium more often in an acidified area?JOURNAL OF AVIAN BIOLOGY, Issue 2 2001S. Bure How birds respond to the recent phenomenon of calcium deficiency in acidified areas is still poorly known. This study, carried out in the Jeseníky Mountains (heavily polluted, acidified area in the Czech Republic), in alpine ecosystems of central Norway, and in the limestone part of the Malá Fatra Mountains (Slovak Republic), provides the first experimental evidence that birds select and bring supplemented calcium-rich items to their nestlings more often in an acidified area. Meadow Pipits Anthus pratensis and Water Pipits A. spinoletta selected calcium-rich items (mainly snail shells) from various materials placed near their nests and this selectivity did not differ between areas or species. Thinning of egg shells (8% at blunt pole, 5% at egg side) suggests that Meadow Pipits in the Jeseníky Mountains were negatively influenced by the low calcium availability, in spite of their ability to adjust foraging behaviour. [source] A hybrid zone dominated by fertile F1s of two alpine shrub species, Phyllodoce caerulea and Phyllodoce aleutica, along a snowmelt gradientJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 2 2008Y. KAMEYAMA Abstract In alpine ecosystems, the steep environmental gradients produced by the difference in snowmelt timing create a dynamic selective regime for alpine plants. As these gradients directly alter flowering phenology, they can affect pollen-mediated gene flow among populations of single and related species. In northern Japan, we found a hybrid zone dominated by fertile F1s of two alpine shrub species, Phyllodoce caerulea and P. aleutica, along a snowmelt gradient. Seed germination confirmed the fertility of F1 hybrid, making the rarity and absence of backcross and F2 plants puzzling. The long-term clonal perpetuation of F1 hybrids (at least a few thousand years ago) contributes the maintenance of this unique hybrid zone. The distribution patterns of chloroplast DNA haplotypes suggest that F1 formation might be caused by directional pollen flow between parental species along the snowmelt gradient. Based on these results, we discuss the ecological and evolutionary significance of this unique hybrid zone. [source] Carbon Sequestration in Two Alpine Soils on the Tibetan PlateauJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 9 2009Yu-Qiang Tian Abstract Soil carbon sequestration was estimated in a conifer forest and an alpine meadow on the Tibetan Plateau using a carbon-14 radioactive label provided by thermonuclear weapon tests (known as bomb- 14C). Soil organic matter was physically separated into light and heavy fractions. The concentration spike of bomb- 14C occurred at a soil depth of 4 cm in both the forest soil and the alpine meadow soil. Based on the depth of the bomb- 14C spike, the carbon sequestration rate was determined to be 38.5 g C/m2 per year for the forest soil and 27.1 g C/m2 per year for the alpine meadow soil. Considering that more than 60% of soil organic carbon (SOC) is stored in the heavy fraction and the large area of alpine forests and meadows on the Tibetan Plateau, these alpine ecosystems might partially contribute to "the missing carbon sink". [source] Seasonal changes in pollinator activity influence pollen dispersal and seed production of the alpine shrub Rhododendron aureum (Ericaceae)MOLECULAR ECOLOGY, Issue 4 2006A. S. HIRAO Abstract In alpine ecosystems, microscale variation in snowmelt timing often causes different flowering phenology of the same plant species and seasonal changes in pollinator activity. We compared the variations in insect visitation, pollen dispersal, mating patterns, and sexual reproduction of Rhododendron aureum early and late in the flowering season using five microsatellites. Insects visiting the flowers were rare early in the flowering season (mid-June), when major pollinators were bumblebee queens and flies. In contrast, frequent visitations by bumblebee workers were observed late in the season (late July). Two-generation analysis of pollen pool structure demonstrated that quality of pollen-mediated gene flow was more diverse late in the season in parallel with the high pollinator activity. The effective number of pollen donors per fruit (Nep) increased late in the season (Nep = 2.2,2.7 early, 3.4,4.4 late). However, both the outcrossing rate (tm) and seed-set ratio per fruit were smaller late in the season (tm = 0.89 and 0.71, seed-set ratio = 0.52 and 0.18, early and late in the season, respectively). In addition, biparental inbreeding occurred only late in the season. We conclude that R. aureum shows contrasting patterns of pollen movement and seed production between early and late season: in early season, seed production can be high but genetically less diverse and, during late season, be reduced, possibly due to higher inbreeding and inbreeding depression, but have greater genetic diversity. Thus, more pollinator activity does not always mean more pollen movement. [source] | |||||||||||||