8.1.3 Ombrotrophic mires 8.1.3.1 Heath moors (site type 3.2.1.1) Heath moors are located on concave or flat sandy areas. They are formed as a consequence of repeated burning of heath forests causing perishing of trees, decrease of evaporation and forming a compact ortstein horizon inhibiting the water infiltration in soil (Masing, 1960; Valk, 1988b). In that way the development of heath moors has not started from the stage of minerotrophic fens but directly from bog-like communities (Valk, 1988a). The peat layer thickness is usually less than 0.5 m and it is laying on ortstein horizon. The tree layer is sparse and stunted, in bush layer some Salix cinerea or S. starkeana can grow. In field layer Calluna vulgaris, Vaccinium uliginosum, Ledum palustre, Andromeda polifolia and other dwarf-bushes dominate. In moss layer besides Sphagnum spp., Polytrichum commune and/or P. strictum can grow rather abundantly. Number and area. 85 areas on 1,165 hectares have been registered as heath moors. Of these, 76 areas (on 980 hectares) include only heath moors, while others also consist of habitats of other types in their marginal parts (mainly raised bogs and peatland forests). Additionally, 17 areas include heath moors as marginal habitats. The actual surface of heath moors may be somewhat larger than the presented figure, since it seems that some registrators did not recognize all heath moors and thus some localities of this site type may be listed under “commonâ€? hummock bogs (site type 3.2.2.1). All in all, there are more than 1,200 hectares of open and treed heath moors in Estonia. This coincides sufficiently with the estimate of Ilomets et al. (2010), according to which heath moors and moor forests together equal to ca 1,500 hectares (Table 6). Distribution. Heath moors are distributed locally and patchily in Estonia (Fig. 18). 62% of all registered habitats (52 areas, 719 ha) are situated either on Hiiumaa Island or in the northwestern part of the mainland. The number of heath moors on Saaremaa Island is notably low. Some small habitats of this site type can be found in central Estonia (between Tori and JĂľgeva) and single sites randomly elsewhere. Large parts in western, southern and northeastern Estonia have no heath moors. Compared with raised bogs, heath moors are small in area. Only two areas (Klooga in northern and Tapiku in central Estonia) exceed 100 hectares, the former being the largest (122 ha). The four next areas hold between 60 and 90 hectares and the next 19 between 10 and 50 ha. Thus, the majority of Estonian moors are tiny to small. Division by Natura 2000 habitats. Most of our heath moors (49 areas on 715 hectares) correspond to the Natura habitat type 7110 (active raised bogs) and 33 areas (413 hectares) to the habitat type 91D0 (bog woodlands). This characterizes the proportion of relatively open heath moors and treed (wooded) moors. Compared with raised bogs, heath moors are small in area. Only two areas (Klooga in northern and Tapiku in central Estonia) exceed 100 hectares, the former being the largest (122 ha). The four next areas hold between 60 and 90 hectares and the next 19 between 10 and 50 ha. Thus, the majority of Estonian moors are tiny to small. Division by Natura 2000 habitats. Most of our heath moors (49 areas on 715 hectares) correspond to the Natura habitat type 7110 (active raised bogs) and 33 areas (413 hectares) to the habitat type 91D0 (bog woodlands). This characterizes the proportion of relatively open heath moors and treed (wooded) moors.
ESTONIAN MIRES: INVENTORY OF HABITATS
114