Environmental and historical factors limiting the distribution of rare forest grasses in south Sweden

Abstract

High soil acidity is often the most important limiting factor for common woodland species. Rare species, however, may be additionally restricted by forest history and management. The distribution of the rare forest grasses Hordelymus europaeus, Festuca altissima, Bromus benekenii and Bromus ramosus in Skåne, south Sweden, is studied in respect to both soil acidity and factors related to former land use. Bromus ramosus seems to be limited primarily by a low soil pH. However, the rarity of the grasses compared with other forest species with a similar range in respect to soil pH may be attributed to former land use. Historical studies show that the rare forest grasses are restricted to estate beech forests with long continuity. This could be due to a combination of low colonising ability and sensitivity to coppice/wooded meadow management or severe grazing, common management features until the early 20th century in most other forest types. With a low colonising ability of the rare grasses, the existing populations probably are relics of an originally wider distribution before humans changed the forest environment. Conservation of the existing pattern of deciduous forest and management without large clear fellings may be necessary to ensure the survival of the rare grasses and other forest plants with similar ecology.