Forb communities

First, to clarify the concept: forb communities mean here areas that are dominated by higher growing perennials in the dry and mesophilic range and - with cabbage thistle, meadowsweet, marsh cranesbill, etc. - in the wet area. Forb communities are formed mostly at border lines such as streams, shores, forests, ditches and roadsides or groups of bushes and can be observed scattered in a wide variety of other habitats. Are previously managed areas (fens, grasslands, meadows, etc.) abandoned (no more mowing, grazing), forb communities often will spread out in the area (with the years they will be replaced themselves by woodland communities). More rarely this is also possible at places with edaphic special locations (such as dry and steep woody heathland area with perennials of the Geranion sanguinei). Following differences characterize forb communities in comparison to the adjacent vegetation:
  • Low mechanical stress, ie no or very irregular, rare and rather late mowing / grazing
  • Higher nutrient levels due to concentration and lack of removal
  • Balanced, more humid and cooler microclimate conditions compared to the managed, lower growing and more gappy former start communities
  • Often rather good, but rather late availability of flowers
Altogether, forb communities are very important for a number of specialized Lepidoptera species (for instance Brenthis ino) as development sites, but just for significantly fewer species than many former start communities (at least grasslands and fens). For many other species, they are also important as a nectar habitat. Insofar forb communities are generally worthy of preservation. However, they may not, or only in exceptional cases, arise at the expense of valuable habitats such as low-nutrient grasslands. On the other hand for example a widening of a riverside or forest edge forb community at the expense of intensive meadows is very positive, however. After the abandonment of grazing in low-nutrient grasslands there will gradually be an increase of forbs and/or grasses. First, many butterfly species increase strongly in population density, because the disturbances are eliminated and the microclimatic conditions are still good. But after a few years there will be a closed canopy without gappy places and at least partial high forb community, where xerothermophilous species such as Polyommatus dorylas die out quickly. Forb communities are endangered by the following factors:
  • Extension of and inclusion in the agricultural or forest economy. Margins, especially those which are several meters wide, are now hardly tolerated. Boundaries, such as between forest and field or along rivers have to be reduced to a minimum, else it could indeed possibly a Euro go through their fingers. Add to that the love of order in the people...
  • Progress of succession, which may result in wetlands in reed communities, but leads generally to bush encroachment
  • Deposits e.g. of timber near the forest
  • Well-intentioned, but often significantly harmful (if more valuable stocks are destroyed) planting of trees, eg at river sides, at unused corners, etc.
  • Eutrophication from adjacent areas and from the air: final nettle monoculture (Urtica dioica)
feuchte Staudenflur dry forb community Filipendula ulmaria dominated forb community prior to flowering time Very humid forb community with Filipendula ulmaria and Iris pseudacorus Detailed view into a forb community with Filipendula ulmaria and Geranium palustre Forb community with Filipendula ulmaria that has been mown already in July (much too early, mowing better would have taken place in September) Alpine forb community dominated by Epilobium angustifolium Rarely mown forb communities such the Artemisia vulgaris line in the picture get narrower and narrower

to top