Structure and ecology of ash forest communities pruno-fraxinetum in Latvia
2008
Reihmane, D., University of Latvia, Riga (Latvia). Faculty of Geography and Earth Sciences
The vegetation of Pruno-Fraxinetum plant communities was described in 2004 – 2005 according to the Braun-Blanquet method throughout Latvia, in forests where common ash (Fraxinus excelsior L.) are dominant species in tree layer on moist soils. Classification of relevés (in total 52) by two way indicator species analysis (TWINSPAN) resulted in two variants of this association: typical variant (typicum) and variant with Filipendula ulmaria. Ellenberg indicator values were used to find out the relationship of flora with climatic (light, temperature, continentality) and edaphic (soil reaction, nitrogen, moisture) factors. Canonical correspondent analysis (CCA) was used to find out differences between two variants of Pruno-Fraxinetum. Results of this research have shown that these forests have complicated structure (form four vegetation layers, high species richness), which mainly depends on moist, rich eutrophic soils, usually with presence of limes. Main differential soil factors in ecological analysis are gradients of soil richness: moisture and nitrogen regimes. The influence of other factors was less expressed. Due to the human influence, especially drainage, the moist ash forests are decreasing and the species composition is changed. As Pruno-Fraxinetum forests in Latvia lie on the northern border of its distribution, the species composition differs from forests in the rest Europe; species characteristic determined by floodplain forests in Central Europe are absent.
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