Revisiting the species–area relationship in a semi-natural habitat: floral richness in agricultural buffer zones in Finland

Buffer zones in agroecosystems are maintained to prevent soil erosion, nutrient leaching and pesticide drift from arable fields. Buffer zones are also semi-natural habitats supporting wildlife in farmland. At the landscape level, buffer zones may also function as corridors in agricultural mosaics. This study aims at understanding the relationship between spatial structure of buffer zones and floral species richness. These are linear landscape elements for which the area is approximated by the product of length and width. The species–area relationship ( S= cA z ) was revised, accordingly, and it was found that patch width was the most effective spatial indicator for species richness in buffer zones. The modified species–area model emphasised the species–area relationship and the importance of width in buffer zone design in an agricultural landscape. It was concluded that there is no unique best-fit model of species–area for both natural and semi-natural ecosystems. Especially in agricultural landscapes, in which habitat heterogeneity is introduced by agricultural activities, the species–area model must be reconsidered accordingly. Some possible factors accounting for the results were discussed. It was suggested that the increase in species diversity with an increase in width of the buffer zone may be due to cross-sectional habitat gradients within the linear patches. The result can be used for optimising buffer zones to meet the needs of biodiversity conservation.