Soil seed bank responses to edge effects in temperate European forests

Aim: The amount of forest edges is increasing globally due to forest fragmentationand land-use changes. However, edge effects on the soil seed bank of temperate forests are still poorly understood. Here, we assessed edge effects at contrasting spatialscales across Europe and quantified the extent to which edges can preserve the seedsof forest specialist plants.Location: Temperate European deciduous forests along a 2,300-km latitudinalgradient.Time period: 2018–2021.Major taxa studied: Vascular plants.Methods: Through a greenhouse germination experiment, we studied how edge effects alter the density, diversity, composition and functionality of forest soil seedbanks in 90 plots along different latitudes, elevations and forest management types.We also assessed which environmental conditions drive the seed bank responses at the forest edge versus interior and looked at the relationship between the seed bankand the herb layer species richness.

Results: Overall, 10,108 seedlings of 250 species emerged from the soil seed bank.Seed density and species richness of generalists (species not only associated withforests) were higher at edges compared to interiors, with a negative influence of C : Nratio and litter quality. Conversely, forest specialist species richness did not declinefrom the interior to the edge. Also, edges were compositionally, but not functionally,different from interiors. The correlation between the seed bank and the herb layerspecies richness was positive and affected by microclimate.Main conclusions: Our results underpin how edge effects shape species diversity andcomposition of soil seed banks in ancient forests, especially increasing the proportionof generalist species and thus potentially favouring a shift in community composition.However, the presence of many forest specialists suggests that soil seed banks stillplay a key role in understorey species persistence and could support the resilience ofour fragmented forests.

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