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1.
  • Balogianni, Vasiliki G., et al. (författare)
  • Root production in contrasting ecosystems : the impact of rhizotron sampling frequency
  • 2016
  • Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 217:11, s. 1359-1367
  • Tidskriftsartikel (refereegranskat)abstract
    • Despite their critical role in every terrestrial ecosystem, fine root production and mortality have not been widely compared among systems due to the practical difficulties of belowground research. We examined fine root production and mortality among five contrasting sites: native and invaded grassland in eastern Montana, USA, aspen forest in southern Saskatchewan, Canada, and birch forest and tundra in northern Sweden. Additionally, we investigated the importance of minirhizotron sampling interval on measures of root production and mortality by comparing measures produced from 1-, 7-, 14-, and 21-day sample intervals. Root length and mortality varied significantly among sites, with invaded grassland having the greatest root length (> 2 x than any other site) and significantly greater root mortality than native grassland (54 %). In contrast, there were no significant differences in root production among the sites. Sample interval had no significant influence on root production or mortality. Minirhizotron sampling intervals up to 3 weeks did not underestimate the measures of root production and mortality in comparison to measures derived from shorter sampling intervals, regardless of the site studied. The results suggest that 3 weeks can be an accurate and efficient sample interval when studying root production and mortality with minirhizotrons.
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2.
  • Bergstedt, Johan, et al. (författare)
  • In the eye of the beholder : bias and stochastic variation in cover estimates
  • 2009
  • Ingår i: PLANT ECOLOGY. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 204:2, s. 271-283
  • Tidskriftsartikel (refereegranskat)abstract
    • Cover estimates by eye is a prevailing method to assess abundance. We examined cover estimates with regard to bias and random variation. Ten observers working with a national forest vegetation survey estimated sixteen 100 m(2)-plots, placed in two different vegetation types. These had similar species composition but were clearly distinguishable in the field. In species-wise analyses, observer bias varied greatly, with Dicranum spp., Vaccinium vitis-idaea and Vaccinium myrtillus having the largest bias. Experience had a surprisingly small impact on variation. Power analysis revealed only small differences between observers in the ability to distinguish the two vegetation types, and little value in averaging the assessments from two, three or four observers. Cover estimates did better than presence/absence data in separating the two vegetation types and multivariate analyses were more powerful than univariate ones.
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3.
  • Carlsson, Georg, et al. (författare)
  • N-2 fixation in three perennial Trifolium species in experimental grasslands of varied plant species richness and composition
  • 2009
  • Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 205, s. 87-104
  • Tidskriftsartikel (refereegranskat)abstract
    • This study is the first to investigate quantitative effects of plant community composition and diversity on N-2 fixation in legumes. N-2 fixation in three perennial Trifolium species grown in field plots with varied number of neighbouring species was evaluated with the N-15 natural abundance method (two field sites, several growing seasons, no N addition) and the isotope dilution method (one site, one growing season, 5 g N m(-2)). The proportion of plant N derived from N-2 fixation, pNdfa, was generally high, but the N addition decreased pNdfa, especially in species-poor communities. Also following N addition, the presence of grasses in species-rich communities increased pNdfa in T. hybridum and T. repens L., while legume abundance had the opposite effect. In T. repens, competition for light from grasses appeared to limit growth and thereby the amount of N-2 fixed at the plant level, expressed as mg N-2 fixed per sown seed. We conclude that the occurrence of diversity effects seems to be largely context dependent, with soil N availability being a major determinant, and that species composition and functional traits are more important than species richness regarding how neighbouring plant species influence N-2 fixation in legumes.
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4.
  • Caron, M. M., et al. (författare)
  • Latitudinal variation in seeds characteristics of Acer platanoides and A. pseudoplatanus
  • 2014
  • Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 215:8, s. 911-925
  • Tidskriftsartikel (refereegranskat)abstract
    • Climate change will likely affect population dynamics of numerous plant species by modifying several aspects of the life cycle. Because plant regeneration from seeds may be particularly vulnerable, here we assess the possible effects of climate change on seed characteristics and present an integrated analysis of seven seed traits (nutrient concentrations, samara mass, seed mass, wing length, seed viability, germination percentage, and seedling biomass) of Acer platanoides and A. pseudoplatanus seeds collected along a wide latitudinal gradient from Italy to Norway. Seed traits were analyzed in relation to the environmental conditions experienced by the mother trees along the latitudinal gradient. We found that seed traits of A. platanoides were more influenced by the climatic conditions than those of A. pseudoplatanus. Additionally, seed viability, germination percentage, and seedling biomass of A. platanoides were strongly related to the seed mass and nutrient concentration. While A. platanoides seeds were more influenced by the environmental conditions (generally negatively affected by rising temperatures), compared to A. pseudoplatanus, A. platanoides still showed higher germination percentage and seedling biomass than A. pseudoplatanus. Thus, further research on subsequent life-history stages of both species is needed. The variation in seed quality observed along the climatic gradient highlights the importance of studying the possible impact of climate change on seed production and species demography.
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5.
  • Csergoe, Anna-Maria, et al. (författare)
  • Two-scale modelling of Saponaria bellidifolia Sm. (Caryophyllaceae) abundance on limestone outcrops from its northern range periphery (Southeastern Carpathians)
  • 2009
  • Ingår i: PLANT ECOLOGY. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 203:2, s. 229-242
  • Tidskriftsartikel (refereegranskat)abstract
    • We modelled the effect of habitat heterogeneity on the abundance of the submediterranean Saponaria bellidifolia, a red list species in Romania. The study was designed at two scales: 100 and 0.5 m(2). At larger scale, generalized additive models and canonical correspondence analysis were used to model the density of ramets, whereas at microscale, binomial logistic regression was employed to model the species' occurrence. S. bellidifolia abundance responded sensitively to habitat type (classified as "grassy", "rocky" and "scree"), rather than to microclimatic variables. At both scales, habitat type was the best predictor of ramet abundance, followed by slope and vegetation cover. At 0.5 m(2), soil depth was also a good predictor of species occurrence. The data revealed that screes are the most suitable habitats for hosting relatively large populations of this rare species, because of occasional natural disturbances and presumably lower interspecific competition.
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6.
  • Dias, Arildo S., et al. (författare)
  • How liana loads alter tree allometry intropical forests
  • 2016
  • Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052.
  • Tidskriftsartikel (refereegranskat)abstract
    • Intense competition with lianas (woodclimbers) can limit tree growth, reproduction, andsurvival. However, the negative effects of liana loadson tree allometry have not yet been addressed. Weinvestigated the hypothesis that liana loading on treecrown alters tree’s allometry, expressed throughslenderness (height–diameter ratio). The relationshipbetween trunk slenderness and percentage of treecrown covered by lianas was investigated for 12 treespecies from 10 fragments of the SemideciduousSeasonal Forest in Southeastern Brazil. We also testedwhether the relationship between slenderness andwood density differ between trees without lianas andtrees heavily infested. Liana loads significantly alteredtree allometry by decreasing slenderness, even whenlianas covered less than 25% of tree crown. Heavywoodspecies decreased their trunk slenderness in agreater ratio than light-wood species. Our findingsindicate that liana infestation shifts tree allometry, andthese effects are stronger on heavy-wood tree species.
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7.
  • Dietrich, Anna L., et al. (författare)
  • Restoration effects on germination and survival of plants in the riparian zone : a phytometer study
  • 2015
  • Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 216:3, s. 465-477
  • Tidskriftsartikel (refereegranskat)abstract
    • Many streams that were channelized to facilitate timber floating in northern Sweden, have in recent years been restored by returning coarse sediment (cobbles and boulders) to the channel and reconnecting riparian with instream habitats. We asked if such restoration measures affect germination and survival of plants in the riparian zone, and if such potential effects depend on location in the catchment. We used a paired site approach, comparing the performance of Helianthus annuus (sunflower) phytometers (seeds and seedlings) in the riparian zone in channelized versus restored river reaches along climate and stream size gradients in the Vindel River catchment in northern Sweden. Phytometer survival, substrate availability, and soil nutrient content in large streams were enhanced by restoration, but overall, phytometer performance was negatively related to the length of the growing season, i.e. phytometers grew best at high altitudes and short growing seasons. This result may have been caused by less competition from the shorter and sparser neighbouring vegetation at these sites or to more frequent flooding events, enhancing retention of organic matter. Soil nutrient levels were lowest close to the coast and in large streams, probably due to deposition of mineral sediment. The higher availability of riparian habitat at restored than at channelized sites suggests that plant species richness and abundance may potentially increase after restoration. Seedling transplantation seems to be a preferable revegetation measure, because phytometer seedlings established better than seeds and survival was significantly higher at restored sites. The good plant performance at sites with short growing seasons and high altitudes suggests that, with limited resources, restoration measures should first be located to such sites.
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8.
  • Dinnétz, Patrik, et al. (författare)
  • Population viability analysis of Saxifraga cotyledon, a perennial plant with semelparous rosettes
  • 2002
  • Ingår i: Plant Ecology. - 1385-0237 .- 1573-5052. ; 159:1, s. 61-71
  • Tidskriftsartikel (refereegranskat)abstract
    • The aim with this study was to analyse the population dynamics of Saxifraga cotyledon, a rare, long lived herb, with semelparous rosettes. In Sweden, S. cotyledon grows in fragmented habitats at high altitude and is classified as vulnerable according to the IUCN system. From a five year demographical study we estimated population growth rates and extinction risks for one small and one large subpopulation. In the small subpopulation deterministic matrix simulations showed large variation, with two transitions projecting negative and two projecting positive population growth. The large subpopulation also showed large variation, but all yearly transitions projected positive population growth. In both subpopulations survival and growth contributed more than twice as much to population growth rates than did sexual reproduction, vegetative reproduction and the seed bank all taken together. In stochastic simulations the maximum likelihood growth estimator was larger than 1 for both subpopulations. None of the two subpopulations suffer from high extinction rates and although the effect of demographic stochasticity increase extinction risk in small populations it is enough with 70 individuals for a viable population of S. cotyledon. Hence, for the studied population of S. cotyledon, rareness per se is not a good indicator of vulnerability.
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9.
  • Donath, Tobias W., et al. (författare)
  • Effects of bryophytes and grass litter on seedling emergence vary by vertical seed position and seed size
  • 2010
  • Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 207:2, s. 257-268
  • Tidskriftsartikel (refereegranskat)abstract
    • Establishment of plants through seeds is often constrained by the quality of microsites, which is in part controlled by the nature and amount of ground cover. The latter consists of living shoots of vascular plants or bryophytes and/or the dead remains of the dominant species. In the present article, we report the results of a controlled pot experiment with five species characteristic of floodplain grasslands. We manipulated the amounts of grass litter and/or mosses to study (1) differences between ground cover types with respect to their effects on microenvironment and seedling emergence and (2) how these effects interact with seed size and seed sowing position. Increasing amounts of both cover types led to increasing soil humidity, whereas temperature amplitude and illumination were decreased. However, since grass litter decomposed much faster than bryophytes, light conditions for germination under grass litter improved considerably with time. Although seedling emergence varied significantly between species, ground cover types and cover amounts, seed position alone explained about 50% of the variation in the data set. Additionally, we found an important interaction between seed size, seed position and cover type: large-seeded species showed a fitness advantage when seeds were situated beneath a cover, irrespective of cover type, which disappeared when seeds were shed on top of a cover layer. We suggest that this interaction may be ecologically and evolutionarily relevant because it may lead to changes in species composition and diversity of plant communities as a consequence of changes in the amount and type of ground cover.
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10.
  • Graae, Bente J., et al. (författare)
  • The impact of temperature regimes on development, dormancy breaking and germination of dwarf shrub seeds from arctic, alpine and boreal sites.
  • 2008
  • Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 198, s. 275-284
  • Tidskriftsartikel (refereegranskat)abstract
    • It has been suggested that the infrequent sexual reproduction of arctic dwarf shrubs might be related to the harsh environmental conditions in which they live. If this is the case, then increases in temperature resulting from global climate change might drastically affect regeneration of arctic species. We examined whether recruitment of Empetrum nigrum ssp. hermaphroditum and Vaccinium uliginosum (hereafter E. nigrum and V. uliginosum) was affected by temperature during three reproductive stages: seed development, dormancy breakage and germination. Seeds were collected from an arctic, an alpine (only E. nigrum) and a boreal site with different climates; stored at different winter temperatures and incubated for germination at different temperatures. Seeds of V. uliginosum developed in the boreal region had a higher percentage germination than did seeds developed in the Arctic. In contrast, seeds of E. nigrum from the arctic site had a higher or similar percentage germination than did seeds from the alpine and boreal sites. Increased winter temperatures had no significant effect on resulting germination percentage of E. nigrum. However, V. uliginosum seeds from the arctic site suffered increased fungal attack (and thus decreased germination) when they were stratified under high winter temperatures. Seeds of both species increased germination with increased incubation temperatures. Our results suggest that both species would increase their germination in response to warmer summers. Longer summers might also favour the slow-germinating E. nigrum. However, increased winter temperatures might increase mortality due to fungal attack in V. uliginosum ecotypes that are not adapted to mild winters.
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11.
  • Gundale, Michael, et al. (författare)
  • Variation in protein complexation capacity among and within six plant species across a boreal forest chronosequence
  • 2010
  • Ingår i: Plant Ecology. - : Springer. - 1385-0237 .- 1573-5052. ; 211:2, s. 253-266
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigated among and within species variation in several litter chemical properties, including protein complexation capacity (PCC), for six plant species across a boreal forest chronosequence in northern Sweden across which stand fertility declines sharply with stand age. We hypothesized (1) that evergreen species which dominate in late-successional stands would exhibit higher PCCs than deciduous species that dominate in young stands, (2) that individual species would increase their PCCs in response to nutrient limitation as succession proceeds, and (3) that differences in PCC among litter types would determine their interactive effects with proteins on soil N and C mineralization. The data demonstrated a high PCC, but a low PCC per unit of soluble phenol, for two deciduous species that dominate in early-successional high fertility stands, providing mixed support for our first hypothesis. No species demonstrated a significant correlation between their PCC and stand age, which did not support our second hypothesis. Finally, a soil incubation assay revealed that litter extracts for three of the six species had negative interactive effects with added proteins on N mineralization rates, and that all six species demonstrated positive interactive effects with protein on C mineralization. This pattern did not provide strong support for our third hypothesis, and suggests that N immobilization was likely a more important factor regulating N mineralization than stabilization of proteins into tannin complexes. These data suggest that multiple interactive mechanisms between litter extracts and proteins likely occur simultaneously to influence the availability of N in soils.
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12.
  • Götmark, Frank, 1955, et al. (författare)
  • Regeneration of oaks (Quercus robur/Q-petraea) and three other tree species during long-term succession after catastrophic disturbance (windthrow)
  • 2014
  • Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 215:9, s. 1067-1080
  • Tidskriftsartikel (refereegranskat)abstract
    • In broadleaved temperate forests in Europe, oak (Quercus robur/Q. petraea) regeneration is reported to be weak or absent. However, most work concern seedlings or saplings, studied relatively few years. We studied a Picea abies stand in Sweden, windthrown and logged (all stems harvested) in 1969, testing the hypothesis that oaks regenerate in the long term among competing tree species after catastrophic disturbance. In 2011, after 40 years/growth seasons, we recorded live and dead trees in the new stand and investigated the surroundings, competition, and succession. The following trees, up to 26 m tall, colonized: Sorbus aucuparia, Betula pendula/B. pubescens, Fagus sylvatica, Q. robur/Q. petraea, and Corylus avellana (a shrub). Betula dominated, and only Fagus was regenerating in 2011. Sorbus had produced most of the dead trees, mainly or partly through intraspecific competition. In the stand, compared to the surroundings, Quercus, Picea, and Alnus glutinosa were under-represented, and Sorbus, Betula, and Fagus were over-represented. Yet, the density of Quercus was far from negligible; 48 large trees/ha. Most of the oaks (74 %) were co-dominant trees and many grew near Sorbus. Thus, oaks can survive and grow fast among pioneer trees and browsing animals, a conclusion which is supported by the literature (nine studies identified). High mortality of Sorbus is part of a long-term succession, where Fagus might come to dominate. However, Quercus likely will persist, in low density. We propose three key traits contributing to long-term persistence of Q. robur/Q. petraea in European temperate forests: long life span, ecological plasticity, and resistance to disturbances.
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13.
  • Hagenah, Nicole, et al. (författare)
  • Interacting effects of grass height and herbivores on the establishment of an encroaching savanna shrub
  • 2009
  • Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 201:2, s. 553-566
  • Tidskriftsartikel (refereegranskat)abstract
    • Shrub encroachment is a widely observed problem in Southern African savannas. Although the effects of herbivory and grass height on woody species recruitment have been studied individually, little information exists about how these factors interact. In this study seeds and seedlings of the encroaching shrub Dichrostachys cinerea were planted in clipped and unclipped grass plots, with and without large herbivores present. Seed germination, seedling survival and seedling predation were monitored for 8 months. Germination started earlier in plots where herbivores were excluded. Overall, the earlier the seeds germinated, the longer the seedlings survived. Clipping positively affected the number of germinated seeds, seedling growth and survival but effects varied among herbivore exclusion treatments and sites. Invertebrates caused the majority of the seedling damage. We conclude the recruitment of D. cinerea is influenced by the interplay of grass height and herbivory. In this study, the presence of large herbivores early in the wet season, and the absence of simulated grazing later on, affected the regeneration of D. cinerea negatively. However, differences in effects among sites suggest that the mechanisms found here may work differently in other habitats.
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14.
  • Hemborg, Åsa M., et al. (författare)
  • Floral phenotypic plasticity as a buffering mechanism in the globeflower-fly mutualism
  • 2011
  • Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 212:7, s. 1205-1212
  • Tidskriftsartikel (refereegranskat)abstract
    • A buffering mechanism in co-evolutionary relationships could be to display phenotypic plasticity in response to environmental changes. In the nursery pollination mutualism between the European globeflower and its exclusive fly pollinators, adults feed and mate in flowers, and larvae develop feeding on seeds. Flower number and size influence fitness for both partners, and large flowers attract more flies. We tested floral plasticity in plants from two contrasting environments: a high-altitude heath and low- and intermediate-altitude meadow forests. High-altitude plants have single flowers, while meadow-forest plants sometimes have multiple flowers. Plants were grown for 3 years in a garden and supplied with eight times more nutrients than available in natural soils, given to controls. During the experiment, over 90% of all plants with excess nutrients flowered, while in controls, 40% (high-altitude) to 75-78% (meadow-forest) plants flowered. Excess nutrients stimulated 30% larger flowers, and in meadow-forest plants flower number increased 4.5-5 times. Flower number was only doubled in high-altitude plants. High-altitude plants displayed less plasticity, and possibly, a different genetic strategy involving meristem limitation.
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15.
  • Henn, Jonathan, et al. (författare)
  • Plant age affects intraspecific variation in functional traits
  • 2021
  • Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 222:6, s. 669-680
  • Tidskriftsartikel (refereegranskat)abstract
    • Functional traits are often used to examine ecological patterns and processes. Ontogeny-changes that occur over time as the result of development-generates variation in traits within individual organisms. We aimed to quantify the role of ontogeny in structuring functional trait variation across a range of co-existing herbaceous perennial species and hypothesized that ontogenetic variation in traits would be greater in younger vs. older plants. We grew eight herbaceous perennial forb species common in tallgrass prairies from seed in a greenhouse in Madison, Wisconsin, USA to determine how and when time-related variation in functional traits is large relative to other sources of variation, such as differences between leaves and species. We destructively measured common functional traits on four individuals of each species every two weeks for 19 weeks, including leaf mass fraction, root mass fraction, stem mass fraction, specific leaf area, leaf dry matter content, and leaf area. We found that most functional traits indeed change through time, that the direction of many changes are consistent between species but the magnitude of change is species specific, and most time-related variation occurred earlier in development. These results emphasize the importance of considering sampling timing and differences between young and old plants when measuring functional traits. Our results suggest that ontogenetic intraspecific variation can be substantial, especially early in life. It may be problematic to use traits measured from mature plants to interpret the importance of processes that occur at earlier life stages or vice versa; using seedling traits to understand adult plant responses may also be inappropriate.
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16.
  • Hjältén, Joakim (författare)
  • Nutrient and secondary metabolite concentrations in a savanna are independently affected by large herbivores and shoot growth rate
  • 2014
  • Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 215, s. 73-82
  • Tidskriftsartikel (refereegranskat)abstract
    • Carbon-based secondary metabolites (CBSMs) such as tannins are assumed to function as plant defences against herbivores. CBSMs are thought to be inversely related to growth rate and nutrient concentrations because a physiological trade-off exists between cellular growth and differentiation, but CBSM concentrations can be altered by herbivory-induced changes in the trade-off. We predicted that a significant interaction exists between herbivory and growth phase, such that the effects of large herbivores (or their exclusion) on nutrient or CBSM concentrations are greatest during phases of rapid shoot or leaf growth. Leaf samples were collected during phases of different growth rate from six woody species 4 years after establishment of a large-scale long-term herbivore exclusion experiment in Kruger National Park, South Africa. Samples were analysed for N, P, condensed tannins and total phenolics. Interactions between growth phase and herbivores were rare. However, the assumption that elevated nutrients and reduced CBSMs occurs during fast phases of growth was supported by four species (consistent with the growth-differentiation balance hypothesis), but not the other two. Large herbivores generally did not affect nutrients, but CBSMs in four species were reduced by large herbivores other than elephants, while CBSMs in two species were reduced by elephants. Carbon limitation ultimately prevailed among woody plants taller than 2 m under long-term browsing. Large herbivores and plant growth phase are independent and important determinants of nutrients or CBSMs in African savannas, but the effects depend on the interacting assemblages of species, which poses challenges to the application of current general hypotheses of plant defence.
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17.
  • Hughes, Francine MR, et al. (författare)
  • The influence of hydrological regimes on sex ratios and spatial segregation of the sexes in two dioecious riparian shrub species in northern Sweden
  • 2010
  • Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 208:1, s. 77-92
  • Tidskriftsartikel (refereegranskat)abstract
    • River management practices have altered the hydrological regimes of many rivers and also altered the availability of regeneration niches for riparian species. We investigated the impact of changed hydrological regimes on the sex ratios and the Spatial Segregation of the Sexes (SSS) in the dioecious species Salix myrsinifolia Salisb.–phylicifolia L. and S. lapponum L. by studying the free-flowing Vindel River and the regulated Ume River in northern Sweden. We surveyed sex ratios of these species in 12 river reaches on the Vindel River and in 17 reaches on the Ume River. In addition, we surveyed the sex and location above mean river stage of 1,002 individuals across both river systems to investigate the SSS of both species. Cuttings were collected from male and female individuals of S. myrsinifolia–phylicifolia from both rivers and subjected to four different water table regimes in a greenhouse experiment to investigate growth response between the sexes. We found an M/F sex ratio in both river systems similar to the regional norm of 0.62 for S.myrsinifolia–phylicifolia and of 0.42 for S. lapponum. We found no evidence of SSS in either the free-flowing Vindel River or the regulated Ume River. In the greenhouse experiment, hydrological regime had a significant effect on shoot and root dry weight and on root length. Significantly higher shoot dry weights were found in females than in males and significantly different shoot and root dry weights were found between cuttings taken from the two rivers. We concluded that changed hydrological regimes are likely to alter dimensions of the regeneration niche and therefore to influence sex ratios and SSS at an early successional stage, making it difficult to find clear spatial patterns once these species reach maturity and can be sexed.
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18.
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19.
  • Jensen, Anna M., et al. (författare)
  • Effects of competition and indirect facilitation by shrubs on Quercus robur saplings
  • 2012
  • Ingår i: Plant Ecology. - : Springer. - 1385-0237 .- 1573-5052. ; 213:4, s. 535-543
  • Tidskriftsartikel (refereegranskat)abstract
    • Indirect facilitation by shrubs has been suggested as a cost-effective way of regenerating oaks in forests of conservation interest. In this study, we tested whether shrubs can enhance growth in pedunculate oak (Quercus robur) by suppressing herbaceous competitors. We studied interactions between young oaks, shrubs, and/or herbaceous vegetation in an open-field experiment, in southern Sweden, over the first 3 years after planting. Oak saplings were grown in four competition treatments: no competing vegetation; with herbaceous vegetation; with shrubs; and with both herbaceous vegetation and shrubs. Competition from shrubs and herbaceous vegetation both reduced stem diameter and biomass accumulation, but they affected biomass partitioning differently. Saplings grown with competition from shrubs partitioned biomass primarily into height growth, while those saplings exposed to competition from herbaceous vegetation invested a relatively higher proportion in root growth. Competition between shrubs and herbaceous vegetation reduced the above-ground biomass of the herbaceous vegetation, resulting in an indirect facilitative effect for the oaks during the first 2 years after planting. However, during the third year, shrubs had a negative effect on biomass accumulation. In summary, results from this study suggest that shrubs indirectly facilitate biomass accumulation of oak saplings by suppressing herbaceous vegetation, possibly by reducing competition for below-ground resources. However, owing to the relatively short duration of positive net outcome for the oak, we recommend that a longer-term assessment of the interaction between oak regeneration and neighboring shrubs be made before the outcome of this study is applied to practical forestry.
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20.
  • Johansson, Maria, et al. (författare)
  • Browser selectivity alters post-fire competition between Erica arborea and E. trimera in the sub-alpine heathlands of Ethiopia
  • 2010
  • Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 207, s. 149-160
  • Tidskriftsartikel (refereegranskat)abstract
    • Mammalian herbivores have the potential to alter the competitive relations of woody species, if consumption is unevenly distributed between species. At elevations above 3,500 m in the southern Ethiopian highlands, vegetation is dominated by Erica arborea and E. trimera. Both species can potentially grow into short trees, but are burnt on a rotation of 6-10 years, and regenerate by re-sprouting from belowground lignotubers. The regenerating scrub is heavily browsed by cattle. We set up browsing exclosures at three burnt sites to quantify the impact of browsing over a 3-year period. When protected from browsing, E. trimera had similar or better height growth than E. arborea, but in browsed vegetation, E. arborea instead grew taller. Browsing was more intense on E. trimera in the first years after fire, indicating a difference in palatability between the species. We checked if browse quality differed, by analysing shoot contents of acid detergent fibre (ADF), protein, phenolics and tannins. Contrary to expectations, the preferred E. trimera contained more ADF, less protein and had a higher tannin activity than E. arborea. Although the vegetative growth of E. arborea is favoured relative to E. trimera under high browsing pressure, rapid change in abundance would not be expected, since short-interval fire will repeatedly eradicate any gains in vegetative growth. However, within the typical fire return interval of less than 10 years, E. trimera barely reach a reproductive state, whereas E. arborea flower profusely. Under the current regime of fire and browsing, this may in the long run be more important than differences in height growth, leading to a gradual increase in the proportion of E. arborea.
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21.
  • Lemke, Isgard H., et al. (författare)
  • Patterns of phenotypic trait variation in two temperate forest herbs along a broad climatic gradient
  • 2015
  • Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 216:11, s. 1523-1536
  • Tidskriftsartikel (refereegranskat)abstract
    • Phenotypic trait variation plays a major role in the response of plants to global environmental change, particularly in species with low migration capabilities and recruitment success. However, little is known about the variation of functional traits within populations and about differences in this variation on larger spatial scales. In a first approach, we therefore related trait expression to climate and local environmental conditions, studying two temperate forest herbs, Milium effusum and Stachys sylvatica, along a similar to 1800-2500 km latitudinal gradient. Within each of 9-10 regions in six European countries, we collected data from six populations of each species and recorded several variables in each region (temperature, precipitation) and population (light availability, soil parameters). For each plant, we measured height, leaf area, specific leaf area, seed mass and the number of seeds and examined environmental effects on within-population trait variation as well as on trait means. Most importantly, trait variation differed both between and within populations. Species, however, differed in their response. Intrapopulation variation in Milium was consistently positively affected by higher mean temperatures and precipitation as well as by more fertile local soil conditions, suggesting that more productive conditions may select for larger phenotypic variation. In Stachys, particularly light availability positively influenced trait variation, whereas local soil conditions had no consistent effects. Generally, our study emphasises that intra-population variation may differ considerably across larger scales-due to phenotypic plasticity and/or underlying genetic diversity-possibly affecting species response to global environmental change.
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22.
  • Liew, Josefine, et al. (författare)
  • Regeneration capacity from buds on roots and rhizomes in five herbaceous perennials as affected by time of fragmentation
  • 2013
  • Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 214:10, s. 1199-1209
  • Tidskriftsartikel (refereegranskat)abstract
    • Variation in seasonal sprouting pattern from roots and rhizomes of perennial herbaceous plants influence the success of plant proliferation ability, invasiveness and escape from weed control measures. The latter often rely on methods, which repeatedly fragment the underground system, thereby trigger adventitious and axillary buds to sprout, and consequently reduce the amount of stored energy. If carried out at times when no re-growth occurs, treatments will have little effect on weed populations, but cost much in terms of labour and energy. The purpose of this experiment was to determine the seasonal variation in bud sprouting capacity after fragmentation. Five troublesome perennial weed species, collected in northern and southern Sweden, were grown outdoors in Uppsala, Sweden (N 59°49′, E 17°39′), from May 2009 to January 2010. Cut root and rhizome fragments, taken at two weeks intervals from July to January, were used to evaluate bud sprouting capacity, which was statistically analyzed using generalized additive models. In Elytrigia repens from southern Sweden and Sonchus arvensis sprouting capacity was significantly impaired during a period from September to November. In Equisetum arvense and Tussilago farfara sprouting was low between July and November where after it increased. In contrast, Cirsium arvense and E. repens from northern Sweden sprouted readily throughout the period. Except for E. repens, a model by populations was significantly better than one based on latitudinal origin. The result suggests a species-specific timing of treatments in weed management, avoiding the non-effective autumn period for E. arvense, S. arvensis and T. farfara, and in some cases in E. repens.
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23.
  • Loydi, Alejandro, et al. (författare)
  • Opposite effects of litter and hemiparasites on a dominant grass under different water regimes and competition levels
  • 2018
  • Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 219:2, s. 133-144
  • Tidskriftsartikel (refereegranskat)abstract
    • Direct and indirect biotic interactions may affect plant growth and development, but the magnitude of these effects may vary depending on environmental conditions. In grassland ecosystems, competition is a strong structuring force. Nonetheless, if hemiparasitic plant species are introduced the competition intensity caused by the dominant species may be affected. However, the outcome of these interactions may change between wet or dry periods. In order to study this, we performed a pot experiment with different densities of the dominant species Schedonorus arundinaceus (1, 2 or 4 individuals) under constantly moist or intermittently dry conditions. The different Schenodorus densities were crossed with presence or absence of hemiparasites (either Rhinanthus minor or R. alectorolophus). Additionally, pots remained with bare ground or received a grass litter layer (400 g m(-2)). We expected that indirect litter effects on vegetation (here Schedonorus or Rhinanthus) vary depending on soil moisture. We measured Schedonorus and Rhinanthus aboveground biomass and C stable isotope signature (delta C-13) as response variables. Overall, Schedonorus attained similar biomass under moist conditions with Rhinanthus as in pots under dry conditions without Rhinanthus. Presence of Rhinanthus also increased delta C-13 in moist pots, indicating hemiparasite-induced water stress. Litter presence increased Schedonorus biomass and reduced delta C-13, indicating improved water availability. Plants under dry conditions with litter showed similar biomass as under wet conditions without litter. Hemiparasites and litter had opposite effects: hemiparasites reduced Schedonorus biomass while litter presence facilitated grass growth. Contrary to our expectations, litter did not compensate Schedonorus biomass when Rhinanthus was present.
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24.
  • Maes, Sybryn L., et al. (författare)
  • Effects of enhanced nitrogen inputs and climate warming on a forest understorey plant assessed by transplant experiments along a latitudinal gradient
  • 2014
  • Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 215:8, s. 899-910
  • Tidskriftsartikel (refereegranskat)abstract
    • Global warming and enhanced nitrogen (N) inputs are two key global-change drivers affecting temperate forest ecosystems simultaneously. Interactive effects of multiple drivers might cause species responses to differ from those in single-factor experiments; therefore, there is an urgent need for more multi-factor studies. Here, we assessed the growth and reproductive performance of multiple populations of a widespread grass of deciduous forests (Milium effusum) sampled along a latitudinal gradient and subjected to experimental manipulations of temperature and nitrogen availability. Common garden transplant experiments along the latitudinal gradient were used to manipulate temperatures and combined with experimental N addition to assess intraspecific responses of the study species to global-change drivers as well as to determine local adaptation. The total biomass, number of seeds and seedling emergence time of M. effusum increased when transplanted in the southern common garden. Apart from effects on the seed mass, the species did not respond to N addition alone. Yet, interactive effects between warming and N addition were found: N addition led to increased biomass growth but only in the northern common garden. Significant home-site advantages were apparent, most likely because of increased mycorrhizal colonization of roots of local transplants. We show that multiple global-change drivers may alter dynamics in understorey communities of temperate forests. Our study reinforces the need to increase our understanding of plant responses to future environmental changes by expanding the multi-factor research framework.
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25.
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26.
  • Manzaneda, AJ, et al. (författare)
  • Effects of microsite disturbances and herbivory on seedling performance in the perennial herb Helleborus foetidus (Ranunculaceae)
  • 2005
  • Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 179:1, s. 73-82
  • Tidskriftsartikel (refereegranskat)abstract
    • The impact of small scale disturbances on the early seedling performance components of Helleborus foetidus (Ranunculaceae) was studied through a transplant experiment. The aims of this study were: (i) to determine if the herbivory pattern depends on microsite disturbance, by the analysis of two of its components, seedling encounter (the probability of at least one seedling being harmed) and seedling exploitation (the proportion of seedling tissue removed once encountered); (ii) to test if seedlings of H. foetidus in disturbed microsites will survive in a greater proportion than seedlings in undisturbed microsites; (iii) to investigate if seedling survival is correlated with the degree of herbivory. Microsite disturbances had a large effect on the herbivory pattern. Seedlings growing in undisturbed vegetation had a 2-fold higher likelihood of being grazed and suffered 1.38-fold higher damage than those growing in disturbed plots. At the end of this experiment, after fourteen months, only 10.4% of the seedlings transplanted were still alive due to seedling desiccation, but no differences on seedling survival were found between disturbed and undisturbed plots. The effect of herbivory and the interactive effect of herbivory and disturbance on seedling survival only reached statistical significance dependent upon site. We concluded that although small scale disturbances had a large impact on herbivory patterns; they had only a minor role in the early seedling survival of H. foetidus. Only locally, small scale disturbances showed an effect on seedling survival through herbivory. Abiotic factors like summer drought and spatial variations determined the early survival of H. foetidus seedlings to a major extent.
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27.
  • Marteinsdottir, Bryndis, et al. (författare)
  • An experimental test of the relationship between small scale topography and seedling establishment in primary succession
  • 2013
  • Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 214:8, s. 1007-1015
  • Tidskriftsartikel (refereegranskat)abstract
    • In infertile environments, the spatial scale and distribution of favourable microsites may be an important determinant of vegetation patterns. Such patterns may be persistent although the association and causality may only be detectable during initial establishment. In this study we investigated experimentally how spatial variation on two different scales and species-specific traits affected seedling survival at an early successional site on SkeiA degrees ararsandur, a 1,000 km(2) homogeneous glacial outwash plain in SE-Iceland. Seedlings of eight native species were transplanted into six different micro-topographical combinations: three types of microsites (lee side of small stones and cushion plants, and control), located within two topographical features (shallow depressions and surrounding flats). Seedling survival was then recorded. Only 11 % of transplanted seedlings survived through the second winter, however seedlings that survived past the second growing season were likely to persist. Survival rates varied by species and were positively linked to seed size. Seedling survival was only weakly associated with spatial variation. The strongest association found was that survival was sometimes higher on flats compared to depressions. Sand accumulation in depressions might lower seedling survival there. We conclude that early plant establishment at the site, and the emergent vegetation mosaic, is most likely produced by the interaction of stochastic factors, such as the sand storms that intermittently rage across the plain and species-specific properties like seed size. However, in better-vegetated areas of SkeiA degrees ararsandur depressions often have higher moss and vascular plant cover than nearby flats, suggesting that moss may control vegetation patterns seen later in succession.
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28.
  • Milberg, Per, et al. (författare)
  • Site factors are more important than management for indicator species in semi-natural grasslands in southern Sweden
  • 2020
  • Ingår i: Plant Ecology. - : SPRINGER. - 1385-0237 .- 1573-5052. ; 221:7, s. 577-594
  • Tidskriftsartikel (refereegranskat)abstract
    • Management of semi-natural grasslands is essential to retain the characteristic diversity of flora and fauna found in these habitats. To maintain, restore or recreate favourable conditions for grassland species, knowledge regarding how they occur in relation to grazing intensity and soil nutrient availability is crucial. We focused on grassland plant species, i.e., species selected to indicate high natural values in semi-natural grasslands. Environmental monitoring data collected at 366 grassland sites in southern Sweden between 2006 and 2010 were used to relate the occurrence of indicator species to factors describing geographic location, local site conditions related to nutrients and moisture, and management. Site productivity, soil moisture and cover of trees and shrubs were the main structuring factors, while other factors related to management had a lesser effect (grass sward height, amount of litter, type of grazer). Not surprisingly, these patterns were also reflected in species-wise analyses of the 25 most commonly occurring indicator species, with almost all species negatively related to site productivity and most also to soil moisture. Furthermore, many species were negatively affected by increasing sward height and litter. In contrast, species-wise responses varied among species in relation to increasing cover of trees and shrubs. In comparison to cattle grazing, sheep grazing was detrimental to six species and beneficial to none, while horse grazing was detrimental to no species and beneficial to four species. When evaluating species traits, taller plant species were favoured when site productivity, grass sward height and the amount of grass litter were high. There were no strong patterns related to the flowering time, leaf arrangement, or nutrient and light requirements of species. These results highlight the importance of nutrient-poor and dry sites, e.g., when selecting sites for conservation, and the importance of the type of management executed.
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29.
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30.
  • Mårtensson, Linda-Maria, et al. (författare)
  • Soil chemistry of local vegetation gradients in sandy calcareous grasslands
  • 2010
  • Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1573-5052 .- 1385-0237. ; 206:1, s. 127-138
  • Tidskriftsartikel (refereegranskat)abstract
    • Acidification and N-deposition are continuous processes that alter the composition of plant communities. We investigated vegetation transitions in sandy grasslands and tested two hypotheses: (1) a shift from vegetation dominated by Koeleria glauca to one dominated by Corynephorus canescens is due to acidification and (2) a shift from vegetation dominated by K. glauca to one dominated by Arrhenatherum elatius is due to increased mineral-N. The occurrence of K. glauca and C. canescens followed pH shifts strikingly well. However, the pH varied considerably between sites, and we found that differences in preference for bare sand may be important for the coexistence of these two species at both high and low pH. In 75% of the gradients, the dominance of A. elatius was related to high content of mineral-N. Most species preferred lime-rich soils and we concluded that both N-enrichment and acidification may lead to loss of species in calcareous sandy grasslands.
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31.
  • Nilsson Hegethorn, Marie-Charlotte (författare)
  • Sphagnum and feather moss-associated N-2 fixation along a 724-year chronosequence in eastern boreal Canada
  • 2021
  • Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 222, s. 1007-1022
  • Tidskriftsartikel (refereegranskat)abstract
    • Dinitrogen (N-2) fixation associated with moss-dwelling bacteria (diazotrophs) is a N source in boreal forests. In feather moss-dominated understories of Fennoscandia, N-2 fixation rates increase with forest age due to N limitation. Whether this is applicable across different boreal ecosystems and successional pathways is not fully understood. In eastern Canada, increasing Sphagnum dominance starting about 100 years post-fire (paludification), is prevalent. Our main objectives were to determine how potential moss-associated N-2 fixation and relative contributions of Sphagnum and other mosses vary with time since fire and to explore the mechanisms driving observed patterns. Sampling was conducted in eight black spruce forests (Picea mariana; 64-724 years post-fire) in northwestern Quebec, Canada, along an established post-fire successional gradient. Potential N-2 fixation was measured with the acetylene reduction method in seven common moss species (Pleurozium schreberi, Hylocomium splendens, Dicranum polysetum, Sphagnum capillifolium, Sphagnum angustifolium, Sphagnum russowii, and Sphagnum magellanicum). N-2 fixation rates by moss communities were low and seemed to increase with stand age, but large variability was found between sites and species. The mechanisms underlying N-2 fixation rates were related to a switch in moss communities from feather moss to a Sphagnum dominance, which had the highest individual acetylene reduction rates, and to an increasing frequency of N-2-fixing samples in old forests. This study provided one of the first records of moss-associated N-2 fixation in eastern Canada and offers insights into how regional and cross-continental differences in moss community composition determine N cycling in boreal forests.
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32.
  • Piqueras, Jesús, 1961-, et al. (författare)
  • Demography and modelling of clonal fragments in the pseudoannual plant shape Trientalis europaea L
  • 1998
  • Ingår i: Plant Ecology. - 1385-0237 .- 1573-5052. ; 136:2, s. 213-227
  • Tidskriftsartikel (refereegranskat)abstract
    • The clonal growth pattern and demography of clonal fragments (aggregation of ramets derived from a common parent ramet) in the pseudoannual plant Trientalis europaea were studied in field conditions from 1991 to 1993. During this period the population of clonal fragments declined, with a half-life of 7.4 years. Number and size of the clonal progeny and stolon length were positively related to the size of the mother ramet. Survival rates of ramets and tubers increased with size. The rate of clonal growth was low: after three years, about 70% of the clonal fragments had only one ramet. This suggests that the pseudoannual growth habit in T. europaea is more important as mechanism of perennation than of ramet multiplication.Field data were used in a simulation model of architecture and population dynamics of clonal fragments. About 10% of the clonal fragments survived to the end of the simulation (15 years) and the mean survival was 4.7 years. The model predicted a positive correlation between persistence of the clonal fragment and number of ramets produced. Sensitivity analysis showed that the production of a daughter ramet of at least the same size as the parent ramet was the most important pathway for the survival and the number of ramets of the clonal fragment, whereas the production of secondary ramets had a very small effect. This confirms the interpretation of the pseudoannual life-cycle as a mechanism of ramet replacement in this species. Sensitivity analysis also revealed that changes in survival probabilities of the smallest ramets had the largest impact on clonal fragment dynamics. This reflects the important role of the smallest size class of ramets as a source of new vegetative propagules, maintaining a hierarchy in the size structure of the population.
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33.
  • Piqueras, Jesús, 1961-, et al. (författare)
  • Modelling the morphological response to nutrient availability in the clonal plant Trientalis europaea L
  • 1999
  • Ingår i: Plant Ecology. - 1385-0237 .- 1573-5052. ; 141:1-2, s. 117-127
  • Tidskriftsartikel (refereegranskat)abstract
    • The morphological responses to changes in environmental quality shown by many clonal plants have been interpreted as an expression of foraging behaviour, as they allow the ramets to become concentrated in more favourable microhabitats. The morphological response to increased nutrient availability in the pseudoannual plant Trientalis europaea was studied in a field experiment. The response was largely size-dependent and consistent with enhanced clonal growth. Fertilized ramets produced more tubers and a larger main tuber. In contrast, stolon length was not affected by the treatment. A spatially explicit simulation model calibrated with data from the field experiment examined the population dynamics of T. europaea ramets in a spatially hetereogeneous, temporally constant, environment. The model showed that T. europaea was effective at concentrating its ramets in favourable patches, but this process was strongly influenced by patch size. The analysis of this response at the clone level showed that ramet aggregation was mainly due to the enhanced performance of clones located initially in the favourable patches, or clones that located a favourable patch by chance. In these clones, the simultaneous increase of ramet size and survival accelerated the production of ramets. The temporal and spatial scale at which the aggregation of ramets in favourable patches was manifested suggests that the effectiveness of the morphological response in T. europaea is favoured by a high spatio-temporal predictability in the environment. Overall, the model emphasized the important role of population dynamics in understanding the nature of the foraging response.
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34.
  • Risberg, Lotta, et al. (författare)
  • Exploiting a window in time. Fate of recruiting populations of two rare fire-dependent Geranium species after forest fire
  • 2014
  • Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 215, s. 613-624
  • Tidskriftsartikel (refereegranskat)abstract
    • Fire ephemerals are few in the boreal forest despite a long history of recurrent fires, which suggests such a life-history pose problems here. We analysed the fate of recruiting populations of two rare and fire-dependent annual Geranium species at burnt forest sites in South-eastern Sweden, to extract vital information on their life-history. Seedlings emerged from the soil seed bank only in the year of fire but spread over several weeks. At sites that burnt early in the season, some seedlings exhibited a summer-annual life-cycle, but those were less successful than plants at the same sites that delayed reproduction until the following year (winter-annuals). Herbivory was frequent in the fire year and until the following spring, but later almost absent, and thus hit seed production in summer-annuals badly. Winter mortality was highly variable for rosette-stage winter-annuals, with some populations nearly obliterated. Reproductive success varied greatly between populations mainly due to pre-reproductive mortality, with a return of 0.2-395 (average 79) seeds per seedling. The vast majority of seeds (92-100 %) were produced by the primary generation, emerging from the seed bank. Out of this first seed crop, 0.2-2.5 % germinated within the study period, resulting in secondary generations. Plants in these later generations were small and produced few seeds, showing that the opportunity for high reproductive success is essentially restricted to one year only. This makes populations highly vulnerable to local near-complete reproductive failure due to winter mortality and herbivory and may be the ultimate reason why strict fire ephemerals are so few in northern forests.
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35.
  • Rozema, Jelte, et al. (författare)
  • Stratospheric ozone depletion: High arctic tundra plant growth on Svalbard is not affected by enhanced UV-B after 7 years of UV-B supplementation in the field
  • 2006
  • Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1573-5052 .- 1385-0237. ; 182:1-2, s. 121-135
  • Tidskriftsartikel (refereegranskat)abstract
    • The response of tundra plants to enhanced UV-B radiation simulating 15 and 30% ozone depletion was studied at two high arctic sites (Isdammen and Adventdalen, 78 degrees N, Svalbard).The set-up of the UV-B supplementation systems is described, consisting of large and small UV lamp arrays, installed in 1996 and 2002. After 7 years of exposure to enhanced UV-B radiation, plant cover, density, morphological (leaf fresh and dry weight, leaf thickness, leaf area, reproductive and ecophysiological parameters leaf UV-B absorbance, leaf phenolic content, leaf water content) were not affected by enhanced UV-B radiation. DNA damage in the leaves was not increased with enhanced UV-B in Salix polaris and Cassiope tetragona. DNA damage in Salix polaris leaves was higher than in leaves of C. tetragona. The length of male gametophyte moss plants of Polytrichum hyperboreum was reduced with elevated UV-B as well as the number of Pedicularis hirsuta plants per plot, but the inflorescence length of Bistorta vivipara was not significantly affected. We discuss the possible causes of tolerance of tundra plants to UV-B (absence of response to enhanced UV-B) in terms of methodology (supplementation versus exclusion), ecophysiological adaptations to UV-B and the biogeographical history of polar plants.
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36.
  • Senior, John (författare)
  • Forest fire may disrupt plant-microbial feedbacks
  • 2018
  • Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 219, s. 497-504
  • Tidskriftsartikel (refereegranskat)abstract
    • Plant-microbial feedbacks are important drivers of plant community structure and dynamics. These feedbacks are driven by the variable modification of soil microbial communities by different plant species. However, other factors besides plant species can influence soil communities and potentially interact with plant-microbial feedbacks. We tested for plant-microbial feedbacks in two Eucalyptus species, E. globulus and E. obliqua, and the influence of forest fire on these feedbacks. We collected soils from beneath mature trees of both species within native forest stands on the Forestier Peninsula, Tasmania, Australia, that had or had not been burnt by a recent forest fire. These soils were subsequently used to inoculate seedlings of both species in a glasshouse experiment. We hypothesized that (i) eucalypt seedlings would respond differently to inoculation with conspecific versus heterospecific soils (i.e., exhibit plant-microbial feedbacks) and (ii) these feedbacks would be removed by forest fire. For each species, linear mixed effects models tested for differences in seedling survival and biomass in response to inoculation with conspecific versus heterospecific soils that had been collected from either unburnt or burnt stands. Eucalyptus globulus displayed a response consistent with a positive plant-microbial feedback, where seedlings performed better when inoculated with conspecific versus heterospecific soils. However, this effect was only present when seedlings were inoculated with unburnt soils, suggesting that fire removed the positive effect of E. globulus inoculum. These findings show that external environmental factors can interact with plant-microbial feedbacks, with possible implications for plant community structure and dynamics.
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37.
  • Sober, Virve, et al. (författare)
  • Seed number and environmental conditions do not explain seed size variability for the invasive herb Lupinus polyphyllus
  • 2013
  • Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1573-5052 .- 1385-0237. ; 214:6, s. 883-892
  • Tidskriftsartikel (refereegranskat)abstract
    • Intraspecific variation in seed size may result from life-history constraints or environmental conditions experienced. This variation in seed size is likely to affect the early stage of invasion as seed size may contribute to the success or failure of population establishment. However, only a few studies have examined seed size variability and its causes and consequences for invaders so far. Using the invasive herb Lupinus polyphyllus, we estimated seed mass variation within and among 39 populations from two different geographic regions in a part of the invaded range. We empirically and experimentally evaluated the effect of seed number and environmental conditions (e.g. geographic region, habitat type, intraspecific competition) on seed mass, emergence and seedling performance. Seed mass varied threefold, being largest among individual plants within populations and smallest among populations. Variation in seed mass was neither related to seed number nor the environmental conditions examined, but led to differences in offspring performance, with emergence and seedling size increasing with seed mass. Larger L. polyphyllus seeds were better establishers than smaller seeds regardless of environmental conditions, indicating that the success of L. polyphyllus invasions is likely to depend positively on seed mass. Our results suggest that some plant species such as the invasive L. polyphyllus may not show an adaptive response in seed mass to resources or environmental conditions, which may partly explain their ability to colonise a range of different habitats.
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38.
  • Sorensen, Pernille, et al. (författare)
  • Moss-specific changes in nitrogen fixation following two decades of warming, shading, and fertilizer addition
  • 2012
  • Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 213:4, s. 695-706
  • Tidskriftsartikel (refereegranskat)abstract
    • Climate warming will induce changes in Arctic ecosystem carbon balance, but besides climate, nitrogen availability is a critical controlling factor of carbon cycling. It is therefore essential to obtain knowledge on the influence of a changing climate on nitrogen fixation, as this process is the main source of new nitrogen to arctic ecosystems. In order to gain information on future nitrogen fixation rates in a changing climate, we studied the effects of two decades of warming with passive greenhouses, shading with sackcloth, and fertilization with NPK fertilizer on nitrogen fixation rates. To expand the knowledge on species-specific responses, we measured nitrogen fixation associated with two moss species: Hylocomium splendens and Aulacomnium turgidum. Our expectations of decreased nitrogen fixation rates in the fertilizer and shading treatments were met. However, contrary to our expectation of increased nitrogen fixation in the warming treatment, we observed either no change (Hylocomium) or a decrease (Aulacomnium) in fixation in the warmed plots. We hypothesize that this could be due to moss-specific responses or to long-term induced effects of the warming. For example, we observed that the soil temperature increase induced by the warming treatment was low and insignificant as vegetation height and total vascular plant cover of the warmed plots increased, and moss cover decreased. Hence, truly long-term studies lasting more than two decades provide insights on changes in key biogeochemical processes, which differ from more transient responses to warming in the Arctic.
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39.
  • te Beest, Mariska, et al. (författare)
  • Linking functional traits to impacts of invasive plant species : a case study
  • 2015
  • Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 216:2, s. 293-305
  • Tidskriftsartikel (refereegranskat)abstract
    • Our understanding of the link between plant functional traits and ecological impact of invasive alien plant species is fragmentary and the mechanisms leading to impacts are poorly understood. Moreover, current knowledge is heavily biased to the temperate regions of the world and we know much less about traits and impacts of invaders in tropical and subtropical ecosystems. We studied two leaf traits of the invasive alien shrub Chromolaena odorata and the impacts of its invasion on native vegetation in savannas. We compared specific leaf area (SLA) and leaf area index (LAI) between C. odorata and native species and assessed how C. odorata differentially affects canopy light interception, soil moisture, soil nutrients, and litter accumulation compared to native species. We found that C. odorata has higher SLA and LAI than native species, lower light and moisture levels below its canopy, but higher nutrient levels and a higher litter accumulation rate. Because of its higher SLA, C. odorata grows faster, resulting in more biomass, increased litter accumulation and higher nutrient availability. Due to its high SLA and LAI, C. odorata intercepts more light and reduces available moisture more than do native trees due to higher transpiration rates, reducing the biomass of native understory vegetation. This study provides empirical evidence for strong links between plant functional traits and ecological impact of invasive plant species, highlighting the importance of traits in predicting ecosystem-level impacts of invasive plant species.
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40.
  • Tye, Matthew R., et al. (författare)
  • Assessing seed and microsite limitation on population dynamics of a gypsophyte through experimental soil crust disturbance and seed addition
  • 2017
  • Ingår i: Plant Ecology. - : SPRINGER. - 1385-0237 .- 1573-5052. ; 218:5, s. 595-607
  • Tidskriftsartikel (refereegranskat)abstract
    • Understanding the factors limiting population growth is crucial for species management and conservation. We assessed the effects of seed and microsite limitation, along with climate variables, on Helianthemum squamatum, a gypsum soil specialist, in two sites in central Spain. We evaluated the effects of experimental seed addition and soil crust disturbance on H. squamatum vital rates (survival, growth and reproduction) across four years. We used this information to build integral projection models (IPMs) for each combination of management (seed addition or soil disturbance), site and year. We examined differences in population growth rate (lambda) due to management using life table response experiments. Soil crust disturbance increased survival of mid to large size individuals and germination. Contributions to lambda of positive individual growth (progression) and negative individual growth (retrogression) due to managements varied among years and sites. Soil crust disturbance increased lambda in the site with the highest plant density, and seed addition had a moderate positive effect on lambda in the site with lowest plant density. Population growth rate (lambda) decreased by half in the driest year. Differences in management effects between sites may represent a shift from seed to microsite limitation at increasing densities. This shift underscores the importance of considering what factors limit population growth when selecting a management strategy.
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41.
  • Wikberg, Sofie, et al. (författare)
  • Ramet dynamics in a centrifugally expanding clonal sedge: a matrix analysis
  • 2006
  • Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1573-5052 .- 1385-0237. ; 183:1, s. 55-63
  • Tidskriftsartikel (refereegranskat)abstract
    • Carex humilis is a clonal sedge that can form distinct rings of densely aggregated ramets. We hypothesize that rings form because both production of new ramets and ramet dispersal are positively correlated to ramet size. This would lead to an overrepresentation of fast-moving and large ramets with high ramet production at the periphery, whereas slow-moving and small ramets with low ramet production would mainly be found in the interior of rings. We use matrix models to analyse how ramet populations both at the periphery and in the interior develop in the absence of ramet dispersal. We found that the stable size class distributions of ramets predicted by the models were not different from the distributions found in the field. Also, the asymptotic ramet population growth rates (lambda(1)) were the same. Hence, we conclude that rings would form even in the absence of a link between ramet dispersal and ramet production. Further analysis of the matrix models showed that the ramet population increases at the periphery but decreases in the interior of rings because medium and large ramets produce fewer large ramets in the interior than at the periphery. We also found that the temporal variance in lambda(1) and transitions rates during the four study years was much higher at the periphery than in the interior. Our results suggest that rings may form because C. humilis ramets use below-ground resources from a much larger area than the one covered by the shoots. As the clone grows larger, the soil volume available to the ramets in the interior decreases because their access to soil outside the ring is cut-off by the ramets at the periphery. Ramet density in the interior is therefore decreasing.
  •  
42.
  • Björn, Lars Olof, et al. (författare)
  • Is provitamin D a UV-B receptor in plants?
  • 2001
  • Ingår i: Plant Ecology. - 1573-5052. ; 154:1-2, s. 1-1
  • Tidskriftsartikel (refereegranskat)abstract
    • An hypothesis is presented that provitamin D (dehydrocholesterol and/or ergosterol) can act as a UV-B receptor in plants and algae. We also propose that the proportions between provitamins D, previtamins D, and vitamins D (D2 and D3), after calibration, can be used to evaluate UV-B exposure of phytoplankton and terrestrial vegetation. This is the final, accepted and revised manuscript of this article. Use alternative location to go to the published article. Requires subscription. The original publication is available at www.springerlink.com .
  •  
43.
  • Diekmann, M, et al. (författare)
  • Beech forest communities in the Nordic countries - a multivariate analysis
  • 1999
  • Ingår i: PLANT ECOLOGY. - : KLUWER ACADEMIC PUBL. - 1385-0237. ; 140:2, s. 203-220
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • In this study we present the first comprehensive multivariate analysis of beech (Fagus sylvatica) forest communities in the Nordic countries. The history of beech and beech forests in Scandinavia are described. In the north, the species is climatically re
  •  
44.
  • Falkengren-Grerup, Ursula, et al. (författare)
  • Vascular plants as indicators of nitrogen enrichment in soils
  • 2004
  • Ingår i: Plant Ecology. - 1573-5052. ; 172:1, s. 51-62
  • Tidskriftsartikel (refereegranskat)abstract
    • The quantification of species along environmental gradients has long been the subject of study regarding natural plant communities and, more recently, ecosystems disturbed by anthropogenic emissions of eutrophying and acidifying substances. We studied 527 sites in southern Swedish deciduous forests divided into two regions, with mean nitrogen depositions of 17 and 9 kg ha(-1) y(-1). The higher deposition in the more exposed region has resulted in higher nitrogen mineralisation and nitrification rates. The objective was to identify nitrogen indicators, which we defined as species with a skewed distribution in relation to the net potential nitrogen mineralisation in the soil. Soil pH was introduced as a co-variable as it may relate to other factors limiting plant growth and survival in these ecosystems. We tested the distribution of the net potential mineralised ammonium (minNH(4)(+)), nitrate (minNO(3)(-)), total inorganic nitrogen (minNH(4)(+)+NO3-) and the ratio of nitrification (percentage of minNH(4)(+)+NO3- as nitrate; %minNO(3)(-)) in 77 herbs. The number of species that showed a skewed distribution differed for the nitrogen variables studied in the following order: %minNO(3)(-) > minNO(3)(-) > minNH(4)(+) much greater than minNH(4)(+)+NO3-. As many as 21 species in region 1 and 17 species in region 2 were selected as indicators for one or several of the nitrogen variables. A fern, five graminoids and seven forbs were found to be indicators of low %minNO(3)(-) and two ferns, two grasses and 13 forbs were found to be indicators of high %minNO(3)(-). We correlated the Ellenberg N indicator values with species with and without skewed distributions, and found that the former group was best related to the N values. As with most indicators, the species identified here are probably best used in combination with other measures to demonstrate the effects of nitrogen deposition on vegetation.
  •  
45.
  • Gaberscik, A, et al. (författare)
  • The influence of enhanced UV-B radiation on the spring geophyte Pulmonaria officinalis
  • 2001
  • Ingår i: Plant Ecology. - 1573-5052. ; 154:1-2, s. 49-56
  • Tidskriftsartikel (refereegranskat)abstract
    • Pulmonaria officinalis is an understorey spring geophyte, which starts its vegetative period before full foliation of the tree storey. During its early growth phase it is exposed to full solar radiation, therefore the enhanced UV-B radiation could present a threat to this species. An outdoor experiment in which potted plants were exposed to below ambient, ambient, and above ambient (corresponding to 17% ozone reduction) UV-B radiation, was conducted in order to evaluate the radiation effects. The amount of photosynthetic pigments and photochemical efficiency of PSII were not affected, but the amount of UV-B absorbing compounds was lower in plants grown under reduced UV-B. This change was measurable after only fourteen days in reproductive shoots, while in the vegetative shoots, it was not detectable until after three months. The leaves of P. officinalis are variegated and the light green spots became less transparent to PAR under enhanced UV-B. The results reveal that under simulated 17% ozone depletion the harmful effects of UV-B on the measured parameters were negligible. This is the final, accepted and revised manuscript of this article. Use alternative location to go to the published article. Requires subscription. The original publication is available at www.springerlink.com.
  •  
46.
  • Moody, Sandra A., et al. (författare)
  • The direct effects of UV-B radiation on Betula pubescens litter decomposing at four European field sites
  • 2001
  • Ingår i: Plant Ecology. - 1573-5052. ; 154:1-2, s. 27-36
  • Tidskriftsartikel (refereegranskat)abstract
    • A co-ordinated series of field experiments were conducted to consider the effects of elevated UV-B radiation applied directly to decomposing plant litter. Betula pubescens was decomposed under ambient and elevated UV-B (simulating a 15% ozone depletion) using outdoor irradiation facilities at Adventdalen, Norway (78° N), Abisko, Sweden (68° N), Amsterdam, The Netherlands (52° N,) and Patras, Greece (38° N). There was no significant effect of treatment on mass loss for samples collected after 2, 12 and 14 months decomposition at Amsterdam, or after 4 months decomposition at Adventdalen. Significant reductions in the mass loss of litter decomposing under elevated UV-B compared to ambient were found at the other 2 sites. The only effect of treatment on litter chemistry during decomposition was a significant reduction in the N concentration of material at Abisko and a significant increase in C:N at Patras for litter decomposing under elevated UV-B. Significant differences were found in the structure of the fungal community decomposing litter in Sweden, the only site to be tested. These data, and the few published studies of the response of decomposition to UV-B incident on litter suggest that, in the ecosystems and climates that have been studied, such direct effects are typically confined to the initial stages of decomposition, and are rather small in magnitude.
  •  
47.
  • Odnevall Wallinder, Inger, et al. (författare)
  • Corrosion-induced release and environmental interaction of chromium, nickel and iron from stainless steel
  • 2006
  • Ingår i: Water, Air and Soil Pollution. - : Springer Science and Business Media LLC. - 0049-6979 .- 1573-2932. ; 170:1-4, s. 17-35
  • Tidskriftsartikel (refereegranskat)abstract
    • A cross-disciplinary research project has been implemented because of increased awareness of the potential environmental effects caused by dispersion of metals from external applications into the environment. The work comprises a 4-year (1998-2002) field exposure of grades 304 and 316 stainless steels, and a laboratory percolation study simulating 20-25 years of chromium and nickel containing runoff water interactions with soil. Total metal annual release rates varied between 0.2 and 0.7 mg m(-2) yr(-1) for Cr, between 0.1 and 0.8 mg m(-2) yr(-1) for Ni and between 10 and 200 mg m(-2) yr(-1) for Fe. Most Cr and Ni is present in an ionic form as a result of the limited presence of organic matter at the immediate release situation. Metal ion concentrations in the runoff water are far below reported ecotoxic concentrations. Studies of the environmental interaction between runoff water from stainless steel and soil show the majority of released Cr and Ni to be retained and their concentrations in percolation water to be very low (0.5-1 mu g L-1 and 1-5.5 mu g L-1 for Cr and Ni, respectively). Speciation calculations showed Cr to be primarily complexed to dissolved organic carbon while Ni also was present in an ionic form in the solution phase. Soil extractions showed Cr and Ni to be very strongly retained within the soil.
  •  
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