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Abstract:
Organic management is one of the most popular strategies to reduce negative environmental impacts of
intensive agriculture. However, little is known about benefits for biodiversity and potential worsening
of yield under organic grasslands management across different grassland types, i.e. meadow, pasture
and mown pasture. Therefore, we studied the diversity of vascular plants and foliage-living arthropods
(Coleoptera, Araneae, Heteroptera, Auchenorrhyncha), yield, fodder quality, soil phosphorus concentrations
and land-use intensity of organic and conventional grasslands across three study regions in
Germany. Furthermore, all variables were related to the time since conversion to organic management
in order to assess temporal developments reaching up to 18 years. Arthropod diversity was significantly
higher under organic than conventional management, although this was not the case for Araneae,
Heteroptera and Auchenorrhyncha when analyzed separately. On the contrary, arthropod abundance,
vascular plant diversity and also yield and fodder quality did not considerably differ between organic
and conventional grasslands. Analyses did not reveal differences in the effect of organic management
among grassland types. None of the recorded abiotic and biotic parameters showed a significant trend
with time since transition to organic management, except soil organic phosphorus concentrations which
decreased with time. This implies that permanent grasslands respond slower and probably weaker to
organic management than crop fields do. However, as land-use intensity and inorganic soil phosphorus
concentrations were significantly lower in organic grasslands, overcoming seed and dispersal limitation
by re-introducing plant species might be needed to exploit the full ecological potential of organic grassland
management. We conclude that although organic management did not automatically increase the diversity of all studied taxa, it is a reasonable and useful way to support agro-biodiversity.
