Ábrahám Levente (szerk.): Válogatott tanulmányok IV. - Natura Somogyiensis 15. / Miscellanea 4. (Kaposvár, 2009)
Salamon-Albert Éva - Horváth Ferenc: Külső-Somogy vegetációja III. Parlagok és inváziós növények diverzitása és tájmintázata
Salamon-Albert É. & Horváth R: Vegetation of Külső-Somogy 45 dry closed grasslands, other treeless habitats, dry closed woodlands, bush vegetation or woodland margins (especially P2a, P2b) and other tree-dominated habitats. Analysing invasive danger in habitat patches fitted to national scale according to Botta-Dukát (2008), 11 habitat groups can be defined in Külső-Somogy region (Fig. 2). Degree of threatening in habitat groups varies between 0 and 94 percentage. The most invaded habitat groups by areal proportion, that is over 80%, are riverine shrublands and woodlands, marshes, mesic deciduous woodlands in lowlands, dry open Quercus woodlands and rocky woodlands. The high invasibility of floodplains is generally described in the literature owing to the continuous disturbance by floods and propagule spreading by the water (e.g. Pysek and Prach 1994, Planty-Tabacchi et al 2001). Opposite to rocky woodlands belong to the most resistant habitats generally. The least invaded habitat groups, that is under 40% areal proportion, are dry closed Quercus woodlands and euhydrophyte habitats. Euhydrophyte habitats proved to be not threatened because the lack of species acclimated to this habitat type but originate from thermal water and present in Hungary (see Király et al 2006). Next see the results of threatened area in habitat groups by 15 most invasive and some other alian plant species according to national scale (Table 2). In the treeless habitat groups (marshes, wet meadows) the most important invasive species are the Solidago spp., and in the woody ones (especially riverine shrublands or woodlands and mesic deciduous woodlands on lowlands) Robinia pseudo-acacia dominates. High proportion of territories invaded by the two previous species mentioned were also revealed in dry and semi-dry grasslands, colline and montane hay meadows and dry, open and closed Quercus woodlands. Ailanthus altissima is frequent in dry and semi-dry closed grasslands, mesic deciduous woodlands of lowlands and mountains and dry open Quercus woodlands. Acer negundo in marshes, Echinocystis lobata in riverine woodlands, Elaeagnus angustifolia in dry and semi-dry closed grasslands, Phytolacca americana in rocky woodlands are the locally frequent species. Reynoutria spp. are completely absent in any habitat type or group, Prunus serotina is a sporadic invasive species of Külső- Somogy region by the database. Some other invasive plant exist in wet, mesic and dry habitat types and groups in the same way. The only exception in plant invasion are the euhydrophyte habitats owing to the total lack of alien species. Above all we can create a regional order of species importance by number of habitat groups with threats: Robinia pseudo-acacia, Solidago spp., some others, Ailanthus altissima, Acer negundo, Asclepias syriaca and Phytolacca americana. Spatial pattern of abandoned fields and invasion Abandoned fields were detected altogether in 86 quadrats (90.5%), habitats threatened by plant invasion were identified in 94 quadrats (99%) of Külső-Somogy region. Total territory of the abandoned fields is 6100 ha that is 2.1% to the whole territory of the region, 14.4% to the total vegetation cover. Habitats endangered by plant invasion have 15200 ha cover that is 5.2% to the whole territory of the region and 35.9% to the seminatural vegetation cover. Areal ratio of habitats threatened by plant invasion to abandoned fields is 2.53. Areal distribution of the two attributes is mostly overlapping and dominate in the North-Western and South-Eastern parts of the region. Abandoned fields occur a tighter (1.5 to 330 ha/quadrat), alien plant species occur in a broader range (1 to 750 ha/quadrat). Minimum proportion value of abandoned fields to a quadrat territory is 0.04%, maximum value is 9.4%, and similar that of habitats endangered by alien species is 0.03% and 21.4%. In order to display occurrence and spatial distribution of abandoned fields and plant invasion a thematic map was constructed for 95 quadrats of Külső-Somogy region (Fig.
