Browsing by Subject "assemblages"

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  • Tolonen, Kimmo T.; Karjalainen, Juha; Hämäläinen, Heikki; Nyholm, Kristiina; Rahkola-Sorsa, Minna; Cai, Yongjiu; Heino, Jani (Springer Link, 2020)
    Aquatic Ecology 54 3 (2020)
    Lake littoral environments are heterogeneous, and different organisms typically show specific responses to this environmental variation. We examined local environmental and spatial factors affecting lake littoral biodiversity and the structuring of assemblages of phytoplankton, zooplankton and macroinvertebrates within and among three basins of a large lake system. We explored congruence of species composition and species richness among the studied organism groups to evaluate their general indicator potential to represent spatial variation in other groups. We expected that effects of water chemistry on plankton assemblages were stronger than effects of habitat characteristics. In contrast, we anticipated stronger effects of habitat on macroinvertebrates due to their mainly benthic mode of life. We also expected that within-basin spatial effects would be strongest on macroinvertebrates and weakest on phytoplankton. We predicted weak congruence in assemblage composition and species richness among the organism groups. Phytoplankton assemblages were mainly structured by the shared effects of water chemistry and large-scale spatial factors. In contrast to our expectations, habitat effects were stronger than water chemistry effects on zooplankton assemblages. However, as expected, macroinvertebrate species composition and richness were mainly affected by habitat conditions. Among-group congruence was weak for assemblage composition and insignificant for richness. Albeit weak, congruence was strongest between phytoplankton and zooplankton assemblages, as we expected. In summary, our analyses do not support the idea of using a single organism group as a wholesale biodiversity indicator.
  • Oksanen, Eljas; Lewis, Michael (2020)
    This paper explores some 220,000 medieval objects recorded in the Portable Antiquities Scheme (PAS) online database of archaeological small finds through Geographic Information System analysis of their relationship with contemporary market sites. First, an overview of the contents of the PAS database is presented in terms of its spatial and ‘object type’ distribution. Second, the relationship of the medieval finds data against documentary evidence of commercial activity is investigated at a national level. Finally, PAS data is contextualised in its historical landscape context through case studies. It is argued that the distribution of PAS finds on the national scale can be linked with patterns of commercial activity, and that while rural and urban finds scatters have distinguishing trends, the countryside population enjoyed access to a range of sophisticated metalwork culture; also, that certain assemblages can be analysed statistically to yield new data and perspectives on local historical development.