Limiting climatic factors and habitats of Erica tetralix L. at its eastern distribution range

20 March 2015

Aunina, Liene; Aunins, Ainars

We determined the limiting climatic factors as well as the preferred habitats of Erica tetralix L. at the eastern limit of its distribution range. It was found that E. tetralix is a typical bog woodland plant species preferring the wettest Sphagnum-rich sites. Northern Atlantic wet heath fragments, alkaline fen and species-rich Nardus grasslands were other habitats for the species. The species composition in E. tetralix habitats resembled that found in appropriate habitats within its main distribution range, although the habitats in the eastern Baltic region lack many Atlantic floristic elements characteristic of wet heath.
A generalised linear model describing the climatic niche of E. tetralix in Latvia suggests that mild winters, which exhibit a combination of a shallow maximum depth of soil freezing and a large number of days when the air temperature exceeds 0°C, as well as abundant annual and winter precipitation, are the main factors allowing the presence of E. tetralix in Latvia. The climate parameters at the eastern limit of the species’ distribution range are consistent with those recorded as being suitable for E. tetralix elsewhere. Our findings reveal a strong relationship between oceanity and E. tetralix distributions.
All known E. tetralix occurrences were found in a 2023 km-wide zone along the Baltic Sea, which was characterised by a more oceanic climate in comparison to the rest of Latvia. The climatic niche model suggests more climatically suitable areas in the Coastal Lowland geobotanical region where the species could potentially be found, most likely in bog woodlands. The future prospects to restore open areas of Northern Atlantic wet heath with E. tetralix in Latvia are poor due to the decline in traditional land-use; these areas have turned into bog woodlands or been converted into agricultural land.