| 1. |
- Balogianni, Vasiliki G., et al.
(författare)
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Root production in contrasting ecosystems : the impact of rhizotron sampling frequency
- 2016
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Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 217:11, s. 1359-1367
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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)
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In the eye of the beholder : bias and stochastic variation in cover estimates
- 2009
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Ingår i: PLANT ECOLOGY. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 204:2, s. 271-283
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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)
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N-2 fixation in three perennial Trifolium species in experimental grasslands of varied plant species richness and composition
- 2009
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Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 205, s. 87-104
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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)
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Latitudinal variation in seeds characteristics of Acer platanoides and A. pseudoplatanus
- 2014
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Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 215:8, s. 911-925
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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)
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Two-scale modelling of Saponaria bellidifolia Sm. (Caryophyllaceae) abundance on limestone outcrops from its northern range periphery (Southeastern Carpathians)
- 2009
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Ingår i: PLANT ECOLOGY. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 203:2, s. 229-242
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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)
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How liana loads alter tree allometry intropical forests
- 2016
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Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052.
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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)
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Restoration effects on germination and survival of plants in the riparian zone : a phytometer study
- 2015
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Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 216:3, s. 465-477
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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)
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Population viability analysis of Saxifraga cotyledon, a perennial plant with semelparous rosettes
- 2002
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Ingår i: Plant Ecology. - 1385-0237 .- 1573-5052. ; 159:1, s. 61-71
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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)
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Effects of bryophytes and grass litter on seedling emergence vary by vertical seed position and seed size
- 2010
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Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 207:2, s. 257-268
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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)
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The impact of temperature regimes on development, dormancy breaking and germination of dwarf shrub seeds from arctic, alpine and boreal sites.
- 2008
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Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 198, s. 275-284
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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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