Cascading effects of changes in land use on the invasion of the walnut Juglans regia in forest ecosystems

1. Plant invasions are affected by many factors that must be favourable in order for invasions to occur. Factors can be grouped into three major categories: propagule pressure, biotic factors and abiotic characteristics; all may be moderated by human activity. However, studies examining all factors simultaneously are rare, and most are limited to a single factor. This hampers our understanding of the mechanisms driving invasions. 2. In recent decades, an alien walnut (Juglans regia) has become invasive in Central Europe due to an increase in the populations of native dispersers, rooks (Corvus frugilegus), and political changes that have resulted in the abandonment of farmland. Here, we test whether increased propagule pressure resulting from the presence of seed-bearing walnuts in abandoned fields interacts with native forest-seed dispersing animals (biotic factors), landscape structure and management, and passive secondary dispersal by gravity (abiotic factors) to facilitate the furthe...