Shifts in functional plant groups in ditch banks under agri-environment schemes and in nature reserves

Management of ditch banks of agricultural fields is considered to be a promising and multifunctional application of agri-environment schemes (AES) on farmland. Our previous research has shown that in the Netherlands, there is a small increase in the number of target plant species of AES in ditch banks. However, the productivity and Ellenberg indicator value for nitrogen also increased. This suggests a change in species composition towards more competitive species. This is important, because management mainly focuses on restoring disturbance tolerant species that used to be common in meadows, rather than competitive dominants. In this study we use a large scale dataset of target species composition in ditch banks of nature reserves and ditch banks with and without AES over 10 years to monitor results of functional plant species groups under these different management regimes. Our analyses show that plant functional type composition in ditch banks of agricultural fields indeed shifted towards more competitive species over the last 10 years, independent of AES. In nature reserves, a similar increase in competitive species was observed. The shift towards more competitive species was reflected in the increase of the average height of the vegetation and the increase in species with a leafy canopy structure, whereas species with a semi-basal canopy structure were decreasing. We conclude that current AES does not increase the number of targeted disturbance tolerant species and that more disturbance such as more frequent mowing is required to obtain these species.