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  • 251. Wiedermann, M. M.
    et al.
    Gunnarsson, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Nilsson, M. B.
    Nordin, A.
    Ericson, L.
    Can small-scale experiments predict ecosystem responses?: An example from peatlands2009In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 118, no 3, p. 449-457Article in journal (Refereed)
    Abstract [en]

    Oligotrophic, Sphagnum-dominated peatlands have been regarded as long-term stable ecosystems that function as carbon sinks. As a result of environmental perturbations, particularly anthropogenic N deposition, this view is now increasingly questioned. We examined whether small-scale field experiments can predict the direction and magnitude of ecosystem responses to increased N supply. We, therefore, compared data from a 10-year field experiment (involving deposition of 2, 15 and 30 kg N ha-1 year-1) with data from a gradient associated with increased N deposition (2, 8 and 12 kg N ha -1 year-1). We chose to compare: (1) the physiological response of Sphagnum balticum, measured in the form of N accumulation as free amino acids (NAA); and (2) changes in the total Sphagnum cover, the cover of S. balticum, and vascular plant cover. In all cases we found a highly significant correlation between the two data sets. We attribute the high correspondence between the two data sets to the key function of the dominant group of organisms, the Sphagna, that monopolize N availability and control the water balance, creating an environment hostile to vascular plants. Thus the key role of Sphagna as ecosystem engineers seems to supersede the role of other, scale-dependent processes. We also conclude that NAA is a sensitive indicator that can be used to signal the slow and gradual shift from Sphagnum to vascular plant dominance.

  • 252. Wiedermann, Magdalena M.
    et al.
    Gunnarsson, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Ericson, Lars
    Nordin, Annika
    Ecophysiological adjustment of two Sphagnum species in response to anthropogenic nitrogen deposition2009In: New Phytologist, ISSN 0028-646X, E-ISSN 1469-8137, Vol. 181, no 1, p. 208-217Article in journal (Refereed)
    Abstract [en]

    Here, it was investigated whether Sphagnum species have adjusted their nitrogen (N) uptake in response to the anthropogenic N deposition that has drastically altered N-limited ecosystems, including peatlands, worldwide.A lawn species, Sphagnum balticum, and a hummock species, Sphagnum fuscum, were collected from three peatlands along a gradient of N deposition (2, 8 and 12 kg N ha(-1) yr(-1)) The mosses were subjected to solutions containing a mixture of four N forms. In each solution one of these N forms was labeled with N-15 (namely (NH4+)-N-15 (NO3-)-N-15 and the amino acids [N-15] alanine (Ala) and [N-15] glutamic acid (Glu)).It was found that for both species most of the N taken up was from, followed by Ala, Glu, and very small amounts from. At the highest N deposition site N uptake was reduced, but this did not prevent N accumulation as free amino acids in the Sphagnum tissues.The reduced N uptake may have been genetically selected for under the relatively short period with elevated N exposure from anthropogenic sources, or may have been the result of plasticity in the Sphagnum physiological response. The negligible Sphagnum NO3- uptake may make any NO3- deposited readily available to co- occurring vascular plants.

  • 253. Wielgolaski, FE
    et al.
    Karlsson, P Staffan
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Plant Ecology.
    Neuvonen, S
    Thannheiser, D
    Tommervik, H
    Gautestad, AO
    The Nordic mountain birch ecosystem – challenges to sustainable management2005In: Plant ecology, herbivory, and human impact in Nordic mountain birch forests, Springer-Verlag, Berlin , 2005, p. 343-356Chapter in book (Refereed)
  • 254.
    Wikberg, Sofie
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Plant Ecology. PLANT ECOLGY.
    Svensson, Brita
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Plant Ecology.
    Ramet demography in a ring-forming clonal sedge2003In: Journal of Ecology, Vol. 91, p. 847-854Article in journal (Refereed)
  • 255. Wikberg, Sofie
    et al.
    Svensson, Brita
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Plant Ecology. Växtekologi.
    Ramet dynamics in a centrifugally expanding clonal sedge: a matrix analysis2006In: Plant Ecology, Vol. 185, p. 55-63Article in journal (Refereed)
  • 256.
    Wiklund, K.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Plant Ecology. PLANT ECOLGY.
    Phosphorus concentration and pH in decaying wood affect establishment of the red-listed moss Buxbaumia viridis2003In: Canadian Journal of Botany, Vol. 81, p. 541-549Article in journal (Refereed)
  • 257.
    Wänstrand, I
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Plant Ecology. Växtekologi.
    Snoeijs, P
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Plant Ecology. Växtekologi.
    Phytoplankton community dynamics assessed by ships-of-opportunity sampling in the northern Baltic Sea: A comparison of HPLC pigment analysis and cell counts2006In: Estuarine Coastal and Shelf Science, Vol. 66, no 1-2, p. 135-146Article in journal (Refereed)
  • 258.
    Ågren, Jon
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Ehrlén, Johan
    Solbreck, Christer
    Spatio-temporal variation in fruit production and seed predation in a perennial herb influenced by habitat quality and population size2008In: Journal of Ecology, ISSN 0022-0477, E-ISSN 1365-2745, Vol. 96, no 2, p. 334-345Article in journal (Refereed)
    Abstract [en]

    1.  In patchily distributed plant species, seed production is likely to be influenced both by local abiotic factors affecting plant size and conditions for fruit maturation, and by population characteristics affecting the intensity of interactions with mutualists and antagonists. However, the relative importance of these effects is poorly known.

    2. We used multiple regression and path models to examine the importance of abiotic factors (sun exposure, soil depth) and population characteristics (size, density and connectivity) for variation in flower and fruit production and intensity of seed predation among 39 populations of the long-lived herb Vincetoxicum hirundinaria in three consecutive years. In addition, we manipulated water availability in a field experiment and recorded short-term and long-term effects on fruit output, and conducted a supplemental hand-pollination experiment.

    3.  Flower production varied little, while fruit initiation, fruit abortion and fruit predation varied considerably among years. Sun exposure and soil depth affected fruit production per plant indirectly and positively through their effects on flower number. Population density affected fruit production negatively through its effect on flower number. Both fruit initiation and the proportion of fruits attacked by the tephritid fly Euphranta connexa were related positively to population size.

    4.  The number of full-size fruits per plant was related positively to sun exposure and population size in two years each, and related negatively to population density in one year. However, because of seed predation, the number of intact mature fruits was related significantly to population characteristics in only one of three years.

    5.  The field experiments showed that both shortage of water and insufficient pollination may limit fruit set in V. hirundinaria.

    6.  Synthesis. These results demonstrate that the relative importance of local abiotic conditions and population characteristics may vary considerably along the chain of events from flower formation to intact fruit, and also among years. They further show that, at least in species with a naturally patchy distribution, connectivity may be relatively unimportant for variation in reproductive output compared to effects of habitat quality, population size and density.

     

  • 259.
    Ågren, Jon
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Fortunel, Claire
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Ehrlén, Johan
    Selection on floral display in insect-pollinated Primula farinosa: Effects of vegetation height and litter accumulation2006In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 150, no 2, p. 225-232Article in journal (Refereed)
    Abstract [en]

    Grazing reduces litter thickness and vegetation height and may thereby indirectly affect reproductive success and selection on floral characters in plants with prostrate growth. Reductions in litter thickness and vegetation height should influence both the resource status of plants with leaves positioned close to the ground and the significance of inflorescence height for interactions with pollinators and seed predators. We experimentally examined how simulated grazing of surrounding vegetation affected pollen limitation, fruit predation and fecundity of short-scaped and long-scaped Primula farinosa, which differ markedly in floral display and therefore in expected attractiveness to pollinators. Litter removal and pruning of surrounding vegetation increased fruit and seed production per plant in the year of the treatment and the probability of flowering in the following year. Pollen limitation of fruit and seed production was stronger in the short-scaped morph than in the long-scaped morph, but was not significantly affected by litter removal and simulated grazing of surrounding vegetation. Supplemental hand-pollination reduced seed size in the year of the treatment and flowering probability in the second year, and these effects did not differ among scape morphs or grazing treatments. The results suggest that grazing indirectly favours seed production in P. farinosa, mainly because it increases the resource status of plants that escape damage. Contrary to expectation, there was no strong evidence that litter accumulation and tall vegetation increase the severity of pollen limitation or reduce the relative performance of the short-scaped morph.

3456 251 - 259 of 259
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