Does cattle movement between forest pastures and fertilized grasslands affect the bryophyte and vascular plant communities in vulnerable forest pasture biotopes?

Abstract

The intensification of agriculture has led to a dramatic decrease in traditional forest pastures in Northern Europe. Furthermore, the remaining forest pastures have often lost their typical characteristics due to eutrophication and forestry practices. We investigated whether the common management practice of fencing forest pastures within the same enclosures as fertilized grassland pastures leads to eutrophication and the consequent decline of bryophyte and vascular plant diversity in Finnish forest pastures, given that when cattle can freely roam between the fertilized grassland pastures and unfertilized forest pastures, nutrients are transported to the forest pastures in the feces and urine of the grazing animals. We found that grazing led to higher electrical conductivity and potassium (K) levels in the forest pastures (n=18) compared to the background levels in adjacent non-grazed forests (n=18). Vascular plant species richness and diversity (Shannon’s entropy) were higher and community structures different in the forest pastures compared to the adjacent forests. Highest species richness was observed in the forest pastures that were unconnected to fertilized grasslands (n=7). Connection here refers to the situation where cattle can access both forest pasture and adjacent fertilized grassland simultaneously. Furthermore, many species indicative of valuable semi-natural pasture biotopes were found only in these traditionally managed forest pastures. In contrast, bryophyte species richness did not differ between the forests and the two types of forest pastures. Moreover, bryophyte communities largely overlapped between the forests and the forest pastures. Our results indicate that even if the forest pastures connected to the fertilized grasslands sustain plant communities that are characteristic of unfertilized semi-natural forest pastures, the conservational quality and diversity of vascular plant communities in particular may be reduced in comparison to the forest pastures without grassland connection. This decline can, at least partially, be caused by the transport of nutrients to the forest pastures and, hence, we recommend that forest pastures are not connected with fertilized grasslands.