Oak forest development as a result of historical land-use patterns and present nitrogen deposition

Historical sources of the use of the forests around the manor Hald during three centuries are used to outline a typical development for many areas on poor sandy soils in Denmark. The balance between forest, shrub, agricultural land, fallow and heathlands in the zone depended on the intensity of land-use for agriculture, grazing and wooden products. The forests at Hald were never totally deforested, and since the forest act of 1805 and first conservation in the early 20th century, the open and shrubby oak woods have developed into oak forest. In a preliminary analysis, data on under-storey vegetation and light conditions from 1916 are compared to data from 1995. Due to conservation of the forest, light penetration has been drastically reduced in the forest since early this century and the reduced light penetration in combination with increased nitrogen deposition has changed the under-storey vegetation significantly. Species diversity and abundance have declined and the typical raw humus species are relatively better adapted to the present conditions. The relative importance of management and air pollution is discussed in relation to succession and preservation of oak forests at a certain successive stage on oligotrophic sandy soils.