Keywords: ornithochory; fleshy fruit; succession; species losses; cultural biotope.

Abstract

Abandonment of traditional agricultural practices in fruit orchards on hillsides in Central Germany results in successive changes in vegetation. We examined three hypotheses relating to these changes: (1) thickets of fleshy-fruited plants develop around planted trees as a result of ornithochory and local soil and site amelioration, (2) woody plants have long-term effects on soil fertility, and (3) thicket development reduces the plant-species diversity of semi-dry grassland between the trees. Field observations and nursery experiments supported the first and second hypotheses. Increased soil fertility, a seed rain of fleshy-fruited shrubs, and shrub establishment occurred mainly around planted fruit trees. Soils from old tree-planting sites remained fertile after the trees had died and disappeared. The third hypothesis was rejected because no decrease in species' richness or diversity occurred during the initial stages of thicket formation. Nevertheless, herbaceous plant species characteristic of the Festuco-Brometea community were absent from the vegetation and seed bank of shaded, nutrient-enriched sites. Conservation of semi-dry grasslands following orchard abandonment will therefore require active control of woody plants.