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Multi-decadal studies of community and ecosystemdynamics are rare; however, this time frame is most relevant for assessing the impact of anthropogenic influences and climate change on ecosystems. For this reason, we investigated changes in vegetation and microtopography over 52 years in two contrasting mire ecosystems, one ombrotrophic (bog) and one minerotrophic (fen), representing different successional stages and contrasting hydrological settings. In both peatlands, floristic composition was recorded in the same permanent plots (n = 55-56, 0.25 m(2)) in both 1960 and 2012 and microtopography was mapped over a large area (ca. 2500 m(2)) that encompassed these same plots. We quantified and compared the community-level changes and internal spatial dynamics, tested associations between pH/microtopography and community/species change, and examined how the area and location of hummock microforms had changed over time. The bog exhibited little site level change in vegetation, where few species changed significantly in cover and plot frequency. However, detailed analyses revealed some large within-plot changes over time in the bog, illustrating that bogs can be highly dynamic systems at a fine scale. In contrast, the rich fen experienced a clear directional change; specifically, bryophyte abundance decreased by 70% and brown mosses were almost extinct. Although pH had decreased over time at the rich fen, this decrease at the plot-level was not associated with the decline of brown moss abundance. The microtopographic structure did not change substantially at the bog where similar to 70% was covered by lawn/hummocks; however, in the rich fen hummocks expanded (from 10% to 16% cover) and moved or expanded down slope. Our study suggests, that at the site-level, the bog ecosystem was more resistant to environmental changes over time compared to the rich fen, as evidenced by shifts in vegetation and microtopography. The contrasting scales of vegetation dynamics observed within a bog (i.e., within-plot changes vs. site-level) indicate that plant-environment feedbacks contribute to the peatland level stability. While in rich fens, internal feedbacks may be weaker and the ecosystem's vegetation and microtopographic structure are vulnerable to shifting hydrological fluxes

Pollen analysis and 14C dating in outlining vegetation history of the primeval forest Fiby urskog, south Sweden

The data file is the raw data collected in Fiby urskog, south Sweden in order to perform a paleoecological study, covering ca 7000 years, using pollen analysis, including spores, charcoal fragments and mineral particles from a small wetland basin. 14C dating, diatom analysis and shore displacement data aided in dating the vegetation succession. Indicators of human impact and other disturbances, during the last ca 1000 years, are given particular attention as well as Picea immigration. Pollen was extracted from the sediment with a Russian peat corer (diameter 5 cm) every 2.5 cm down to ca 100 cm. Standard acetolysis method was used to extract pollen and spores. Treatment with hydrofluoric acid was performed on the lowermost part of the sediment to separate the large number of mineral particles.Materialet avser rådata som legat till grund för en pollenstudie vars syfte är att beskriva vegetationshistorien i Fiby urskog, Uppland, de senaste ca 7000 åren. En ca 100 cm sedimentpropp togs i en central våtmark. Tonvikt ligger på de senaste ca 1000 åren där granens invandring och eventuell kulturpåverkan betonas särskilt. 14C-analys har använts vid åldersbestämning liksom landhöjningsdata, diatomanalys och stratigrafi. Se engelska katalogsidan för mer information: https://snd.gu.se/en/catalogue/study/SND112

Birch sapling characteristics growing beyond the tree line in Norway and Sweden

Questions: How do population structure and recruitment characteristics of Betula saplings beyond the treeline vary among climatic regions, and what is the potential for development into tree-sized individuals with interacting grazing pressure? Location: Scandes Mountains. Methods: Sapling characteristics of Betula pubescens subsp. tortuosa, their topographic position above the treeline, growth habitat and evidence of recent grazing was investigated in three areas with a long continuous grazing history, along a latitudinal gradient (62-69°N). Results: Saplings were common up to 100 m above the treeline in all areas. The northern areas were characterised by small (<30 cm) and young (mean 14 years old) saplings in exposed micro-topographic locations unfavourable to long-term survival. In the southern area, broad height (2-183 cm) and age (4-95 years; mean 32 years) distributions were found in sheltered locations. Age declined with altitude in all areas. Sapling growth rate varied within and between areas, and the age x height interaction was significant only in the southern area. Growth rates decreased from south to north and indicated a considerable time required to reach tree size under prevailing conditions. Conclusions: Regional differences can be attributed to climatic differences, however, interacting biotic and abiotic factors such as micro-topography, climate and herbivory, mutually affect the characteristics of birch saplings. In view of the long time needed to reach tree size, the generally expected evident and fast treeline advance in response to climate warming may not be a likely short-term scenario. The sapling pool in the southern region possesses strongest potential for treeline advance

Femtio års skogsutveckling på Granskär, norra Uppland

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