Development of oaks ( Quercuspetraea (Matt.) Liebl.) emerged from bird-dispersed seeds under old-growth pine ( Pinussilvestris L.) stands

Abstract

In East Germany, there are a lot of areas covered by old pine stands. They are growing on soils, on which under natural conditions without anthropogenic impact mixed stands of oak ( Quercus petraea (Matt.) Liebl.) and pine ( Pinus silvestris L.), would form a natural forest. An important objective of ecological silviculture in these areas is to convert the pure pine stands into mixed oak–pine stands by using natural regeneration methods. A highly appreciated assistant in this connection is the European jay ( Garrulus glandarius L.). The remarkable results of its work have been found by analyzing the natural regeneration in a few old pine stands in the forest district of Weißwasser in Saxony. Although mother trees of oak are very scarce there, natural regeneration of oak was found everywhere in the research area. The oak regeneration, undoubtedly created by the jay, amounted to at least 2000 oaks/ha. They were mainly distributed at random, while pine regeneration was aggregated in places where gaps in the pine canopy occurred. Oak regeneration was established much earlier than pine regeneration. Thus, oaks exceeded pines in age, height and diameter. The oaks were also superior to pines concerning height increment for the last three years. Thus, there is a good chance for oak to defend its prevailing role in the regeneration in the future. Probably, the next forest generation will be composed of oak and pine trees. The analysis of the quality of the oak regeneration shows that there is no substantial difference to artificially sown oak stands. This indicates that the European jay creates oak stands sufficiently both in number and quality.