| 1. |
- Berendse, F, et al.
(författare)
-
Raised atmospheric CO2 levels and increased N deposition cause shifts in plant species composition and production in Sphagnum bogs
- 2001
-
Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 7:5, s. 591-598
-
Tidskriftsartikel (refereegranskat)abstract
- Part of the missing sink in the global CO2 budget has been attributed to the positive effects of CO2 fertilization and N deposition on carbon sequestration in Northern Hemisphere terrestrial ecosystems. The genus Sphagnum is one of the most important groups of plant species sequestrating carbon in temperate and northern bog ecosystems, because of the low decomposability of the dead material it produces. The effects of raised CO2 and increased atmospheric N deposition on growth of Sphagnum and other plants were studied in bogs at four sites across Western Europe. Contrary to expectations, elevated CO2 did not significantly affect Sphagnum biomass growth. Increased N deposition reduced Sphagnum mass growth, because it increased the cover of vascular plants and the tall moss Polytrichum strictum. Such changes in plant species composition may decrease carbon sequestration in Sphagnum-dominated bog ecosystems.
|
|
| 2. |
- Bragazza, Luca, et al.
(författare)
-
Effects of mineral and nutrient input on mire bio-geochemistry in two geographical regions
- 2003
-
Ingår i: Journal of Ecology. - : Wiley. - 0022-0477 .- 1365-2745. ; 91:3, s. 417-426
-
Tidskriftsartikel (refereegranskat)abstract
- 1 We assessed the role of climatic conditions and the effects of different, long-term atmospheric depositions in controlling the mineral and nutrient contents in pore-water, surface peat and in living Sphagna at a boreo-nemoral mire in Sweden and an alpine mire in Italy. 2 The terrestrial contribution of Ca2+, Mg2+ and SO42- in bulk precipitation was much greater at the Italian mire, in accordance with the different bedrock in the region and the higher level of atmospheric pollution. 3 At both mires, the contribution of bulk precipitation to the concentration of major ions in mire pore-water was much greater in the ombrotrophic than in the minerotrophic part, because of the raised morphology of the mires, which limited the inflow of mineral soil water to the margins. The only ions strongly depleted in mire pore-water compared with precipitation were K+, NO3- and NH4+ and these were therefore limiting to plant growth. 4 Higher SO42- concentration in pore-water at the Swedish mire, which experienced lower atmospheric inputs of sulphate, was probably caused by oxidative processes during a long dry period in the summer before sampling. 5 Higher rates of NO3-, NH4+, as well as SO42- atmospheric inputs at the Italian mire were reflected in significantly higher N and, partly, S concentrations in ombrotrophic Sphagna. Higher NO3- concentration in pore-water at the Italian mire was associated with a lower N retention coefficient of the ombrotrophic Sphagnum plants, suggesting a reduced nitrogen filtering ability of the moss layer.
|
|
| 3. |
|
|
| 4. |
- Ecke, Frauke, et al.
(författare)
-
Succession on a land uplift coast in relation to plant strategy theory
- 2000
-
Ingår i: Annales Botanici Fennici. - 0003-3847 .- 1797-2442. ; 37:3, s. 163-171
-
Tidskriftsartikel (refereegranskat)abstract
- Plant strategies under succession were evaluated for communities on rising seashores of the northern Gulf of Bothnia, Sweden, representing sites of primary succession. The succession could not be explained by Grime's CSR model. Early successional stages were neither characterized by high incidence of ruderals as proposed for secondary successions, nor by the dominance of stress tolerators, as proposed for primary successions. Short-lived species were almost totally absent. Instead, the shore habitat was characterized by species with an ability to tolerate and vegetatively recover from disturbance. The way in which different species experience one and the same form of stress or disturbance is an important reason why the classification on the basis of stress and disturbance seems to be insufficient to explain the course of this succession. Dominants of early and late successional stages differed with respect to root system, breeding system, leaf longevity and growth form (graminioid, herb).
|
|
| 5. |
- Falkengren-Grerup, U., et al.
(författare)
-
Does nitrogen deposition change the flora?
- 2000
-
Ingår i: Effects of nitrogen deposition on forest ecosystems. - Stockholm : Naturvårdsverket.
-
Bokkapitel (refereegranskat)
|
|
| 6. |
- Falkengren-Grerup, U., et al.
(författare)
-
Förändras floran av kvävenedfallet?
- 2000
-
Ingår i: Effekter av kvävenedfall på skogsekosystem. - Stockholm : Naturvårdsverket.
-
Bokkapitel (refereegranskat)
|
|
| 7. |
- Frost, Ingela, et al.
(författare)
-
Spatial pattern and size distribution of the animal-dispersed tree Quercus robur in two spruce-dominated forests
- 2000
-
Ingår i: Ecoscience. - 1195-6860. ; 7:1, s. 38-44
-
Tidskriftsartikel (refereegranskat)abstract
- We investigated the degree to which the spatial distribution of oaks (Quercus robur L.) was related to habitat conditions, as reflected by vegetation type and structural features presumed to attract animal dispersers (trails, community borders). We hypothesized that the distribution pattern of oaks, with their potential to establish in many habitats, depends on the behaviour of the dispersing animals to a greater extent than micro-habitat conditions. One 100 m x 100 m plot was surveyed in each of two coniferous forests in east-central Sweden. No adult oak trees grew in the forests; all oaks were considered as dispersed into the plots by animals. We tested whether oak distribution was clumped with spatial autocorrelation analyses and whether oak distribution was related to vegetation type, species composition, tree cover, distance to nearest fertile oak tree, or distance to animal trails. Our study showed that oak trees were also spatially aggregated in a small-scale context. The spatial distribution of seedlings and older trees were associated with species richness and tree cover but not with any specific vegetation type, even though fewer oaks than expected grew in spruce forest habitats. Furthermore, we found that oak trees were associated with trails. There were differences in oak distribution between the two study sites in total number of oaks, the number of first-year seedlings, caches, and oak occurrence in relation to species richness and distance to nearest fertile oak. Seed-dispersing animals seem to be of importance for oak distribution even though animal activities seem to differ between sites.
|
|
| 8. |
- Grandin, Ulf, et al.
(författare)
-
Allozyme variation at a PGI locus in differently aged populations of Moehringia trinervia (Caryophyllaceae) in a successional area
- 2002
-
Ingår i: Nordic Journal of Botany. - : Wiley. - 0107-055X .- 1756-1051. ; 22:3, s. 303-311
-
Tidskriftsartikel (refereegranskat)abstract
- We studied genetic effects of the colonisation process during primary succession by analysing allozyme variation at a PGI locus in differently aged populations of Moehringia trinervia, which is a selfing annual with low dispersal ability. The populations studied come from islands and shores created in the 1880s by a drop in the water table of a Swedish lake and from old parts of a large island and of the mainland. The population age is known from five vegetation analyses over a century. We have also analysed the genetic composition of M. trinervia derived from seeds in the soil. Mainland populations had a higher genetic diversity than island populations that were little differentiated and differed genetically from the mainland populations. There was no temporal trend in the distribution of genetic variation on the new islands. The presence of alleles in the extant populations was associated with the proportion of that allele in the seed bank, indicating a main recruitment from the seed bank and not by repeated immigrations. We suggest that some of the new islands were colonised by a few early founders from the mainland. Later colonisation has occurred between adjacent islands, which preserves the founder effect and could explain the uniform, low genetic variation in the island populations
|
|
| 9. |
- Gunnarsson, Urban, et al.
(författare)
-
Diversity and pH changes after 50 years on the boreal mire Skattlosbergs Stormosse, Central Sweden
- 2000
-
Ingår i: Journal of Vegetation Science. - 1100-9233 .- 1654-1103. ; 11:2, s. 277-286
-
Tidskriftsartikel (refereegranskat)abstract
- The Skattlosbergs Stormosse min was reinvestigated in 1995 after 50 years of natural development since the previous investigation. The undrained mire is situated in an area with low anthropogenic deposition. The distribution of 106 plant species was mapped in detail and pH was measured at 251 locations, providinga unique opportunity to quantify long-term mire dynamics. The resultss how decreased pH in the richer (high-pH) parts of the mire, but little or no change in the poor fen andombrotrophipca rts.1 4 species had disappeared while two news pecies were recorded. Most species had a more restricted distribution in the mire area in 1995 than in 1945. Species richness in lOm x 0Omp lots had decreased, especially in plots with higher pH. Most Sphagnum species had unchanged distributions over the mire, while 7 3 % of other bryophyt sepecies and 3 8% of vascular plant species had decreased by more than 20 % in plot frequency. There was a strong relationship between number of species and pH-value. The mean and standard eviation of pH in plots where the species occurred have both decreased since 1945. We interpret the changes in species richness in the richer fens to be mainly caused by acidification. This could partly be an autogenic succession, but may be enhanced by increased atmospheric deposition. The mire represents an almost untouched site which can act as a reference for mires in morepolluted areas.
|
|
| 10. |
- Gunnarsson, U, et al.
(författare)
-
Dynamics or constancy in Sphagnum dominated mire ecosystems? A 40-year study
- 2002
-
Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 25:6, s. 685-704
-
Tidskriftsartikel (refereegranskat)abstract
- Traditionally mire ecosystems (especially bogs) have been viewed as stable systems with slow changes in the vegetation over time. In this study the mire Akhultmyren, south-central Sweden was re-investigated in 1997 after 40 yr of continued natural development. The results show a high degree of dynamics in a Sphagnum dominated bog and fen. Altogether 97 vascular plant and bryophyte species were recorded in the two inventories of the bog and poor fen vegetation. pH and electrical conductivity in the mire water were also surveyed. In 1997 we found 10 new species and that 8 species had disappeared since 1954 but the over-all mean number of species per plot (size 400 m(2)) had hardly changed. However, 21% of the species increased and 21% decreased significantly in frequency. Most of the species that decreased in frequency were low-grown vascular plants, most common in wet microhabitats. Vascular plant species that increased in frequency included trees (defined as > 1.3 m in height) and were generally taller than the unchanged or decreasing species. The frequency of dwarf shrubs and hummock bryophytes increased too. Areas with an initial pH of 4.5-5.0 showed the strongest decrease in pH, coinciding with an enlarged distribution of some Sphagnum species. The species diversity increased on the bog, but decreased in the wettest parts of the fen, where the pH also decreased. Species with unchanged or increasing frequency often showed high capacity to colonise new plots. On average the sum of gains and losses of species in the plots in 1997 was ca 50% of the species number in 1954. The vegetation changes indicate a drier mire surface and an increased availability of nitrogen. The increased tree cover may have triggered further changes in the plant cover.
|
|
