Effects of cropping practice dynamics on permanent grassland vegetation during the conversion to organic farming

The aim of this work was to identify the impact of farming practices on permanent grassland vegetation during the conversion from conventional to organic farming. We considered functional and species diversities in order to compare the different grassland categories based on the farming practices used over a period of six years - five years before conversion and one year after. We identified three categories of grasslands: those generally cut twice a year, those intensely grazed, and those that were used under diversified practices. We showed that grasslands characterised by cutting and low fertilization level have the highest species richness compared to the other two categories (23.2, 16.9 and 17 species, respectively), and the lowest pastoral index (45.9, 66.8 and 68.6, respectively). These cut paddocks also presented the highest functional diversity (i.e., richness of functional property attributes) for two of the properties studied: means of dispersal and establishment strategy as defined by Grime. Grasslands with diversified practices (grazing, cutting and nitrogen supply) were not characterised by any single or combined functional property attribute, to the contrary of the two other categories. Finally, farming practices alone do not explain all of the differences in vegetation. We therefore hypothesize that, first, the dynamics of permanent grassland vegetation following conversion to organic farming is only initiated by agricultural practices and, second, other key factors such as landscape characteristics affect these dynamics.