Recruitment and growth of herb-layer species with different colonizing capacities in ancient and recent forests


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Abstract. Forest herbs differ greatly in their capacity to recolonize secondary forests established on former agricultural land. We investigated whether interspecific differences in recruitment or growth can account for differences in colonization success. Seeds and adults of two species with limited colonization capacities (Anemone nemorosa and Primula elatior) and two species with high colonization capacities (Ranunculus ficaria and Geum urbanum) were introduced in ancient and recent forest sites within the Muizen forest (Belgium). At all sites, half of the plots were also cleared of above-ground vegetation.

Seedling establishment was similar in recent and ancient forest sites. However, both the number and subsequent survival of seedlings of the two hemicryptophytes (G. urbanum and P. elatior) were significantly lower when vegetation cover was present, while seedling number and survival of the two geophytes (A. nemorosa and R. ficaria) were less influenced by vegetation cover. Adult performance of P. elatior and G. urbanum was significantly better in the nutrient enriched recent forest stands and in the absence of vegetation cover. Performance of A. nemorosa and R. ficaria was not affected by any of these factors. We conclude that the extent of seed limitation is probably the main cause for the different colonization capacities of the species investigated.