Herb layer vegetation patterns of silvopastoral systems: the interactive role of succession, disturbance and seed bank

Abstract Due to their heterogeneous landscape structure, extensively managed temperate silvopastoral systems provide multiple ecosystem services such as climate-resilient livestock production and carbon sequestration. Main habitat types within these landscapes (open pastures, solitary trees, shrubby patches, and adjacent second-growth forests) form an interconnected dynamic network with state transitions driven by secondary succession (towards woody states) and disturbance (towards open states), and the balance between the drivers is key to preserve their exceptionally rich herbaceous flora. To understand how soil seed bank may contribute to the dynamics of the herb layer in silvopastoral systems, we assessed its composition and richness in the above-mentioned habitats and compared these to the herb layer using non-metric multidimensional scaling, generalized linear mixed-effects models and indicator species analyses. We found that each habitat showed distinct compositional patterns, explained by strong environmental filters. Conversely, soil seed bank was more similar among habitats due to legacy seeds from previous vegetation states. This ecological memory in a particular location may assist future compositional transitions of the herb layer by reducing dispersal limitation and can be a useful asset in ecosystem restoration. Furthermore, our study showed that solitary trees with grassy or shrubby undergrowth have key roles in the herb layer dynamics of silvopastoral systems by being the main locations of soil seed bank build-up and transitional hotspots of herb layer diversity during early forest succession. Therefore, conservation strategies should pay extra attention to these small but important landscape features.