Development of the breeding bird community of a silvoarable agroforestry system with short rotation coppice strips over a 16-year period

Abstract

Modern silvoarable agroforestry systems (AFS) with short rotation coppice strips (CS) are considered as a potential measure to increase structural diversity in agricultural landscapes and to promote biodiversity while simultaneously producing arable crops and woody biomass. However, studies investigating the actual potential of these novel land use systems to promote biodiversity are scarce. We therefore investigated the importance of a silvoarable AFS with different CS variants as habitat for breeding birds on an experimental site in northern Germany, which was studied several times over a 16-year period since its establishment. In addition, the habitat function and quality of CS was compared with hedgerows. The results show that establishing CS on arable land creates additional habitats for shrub and tree breeding species and thus increases species numbers and territory densities. Tree harvest resulted in a decrease in species numbers and densities. However, since Aspen rows (for timber production) or native woody species were retained during harvesting in some CS, suitable nesting opportunities for some species remained. A sharp decline in Skylark territories was observed within the open land of the AFS, from nine breeding pairs in the year after establishment (2009) to only two breeding pairs each in 2022 and 2023. Compared to CS, hedgerows were more species-rich and had much higher territory densities. We conclude that the integration of CS into croplands can promote some species of woody habitats, especially if measures such as the integration of trees of different heights or native woody species and sectional harvesting are implemented. However, CS still clearly lag behind hedgerows in terms of their habitat quality. Furthermore, the establishment of CS may have negative effects on threatened open land species like the Skylark. The requirements of these species should therefore be considered when planning AFS. Establishing AFS with CS could especially be an option in cleared, intensively used agricultural landscapes, where CS could represent a trade-off between the promotion of birds and agricultural production.