Time matters: Effects of duration of the organic management on biodiversity in hedgerows

Summary in the original language of the document

Organic farming has been suggested to counteract declines in farmland biodiversity but comparisons to conventional farming have produced variable outcomes. At the plot and field scales positive effects of organic farming on abundance of birds, predatory insects, and soil organism have been found and for plants positive effects on species richness have been found in hedgerows. Establishment of new species is a slow process especially in nutrient rich habitats such as hedgerows in the farmland.
Fluctuating market prices and short-term economic gains have become increasingly important as incentive for conversion from conventional to organic management and transition forth and back between practices has become more frequent. We investigated the effect of duration of the organic management on the biodiversity of hedgerow ground vegetation.
We found that duration of the organic management of the neighbouring fields (3 to 30 years) significantly affected the species richness of hedgerow ground vegetation. Transition times of up to thirty year did not result in saturation of the species curve and short term organic management resulted in relatively small positive effects on plant species richness of hedgerow ground vegetation. Mainly herbs, either annual and biennial or perennial, showed increased species richness in organic hedgerows whereas the number of grass species was more or less unaffected. Generally, the flora was richer in hedgerows on loamy soils compared to hedgerows on sandy soils. Despite management practice and soil type a few tall-growing and highly competitive species such as Elytrigia repens, Dactylis glomerata, Urtica dioca, Anthriscus sylvestris, and Cirsium arvense dominated the hedgerow ground vegetation and made up 70-99% of the plant cover.