30 mai 2017 Morgane CAMPION

Our grasslands– an asset for the biodiversity of agroecosystems

The CRA-W highlights the importance of grassland managementto increase floral diversity, and hence ecosystem services. In sustainable and multifunctional agriculture, it is essential to reconcile provisioningand regulating services.

Our grasslands– an asset for the biodiversity of agroecosystems

In our livestock systems, which occupy almost 50% of agricultural land in Wallonia, the challenge is to combine grass production with regulatingfunctions potentially providedby grasslands, such as carbon storage, water filtration, soil erosion regulation or pollination. Recent studies indicate a link between the grassland ecosystem functioning and the provision of a set of services which are essential to our societies and their development. The range of functions that an agroecosystem can support is closely linked to the biodiversity it contains. Thus, a species-rich environment ensures a greater diversity of functions (as each species can play a complementary role) but is also potentially more stable  face to disturbances (since any role no longer performed by a missing species can be quickly filled by another species). We therefore felt it important to throw some light on the links between management and plant diversity in grasslands.

During  BIOECOSYS project, the monitoring of flora in 49 grasslands across  Ardenne, Famenne and  Pays de Herve regionsconfirmed the existence of a link between floral diversity and management intensity: extensive grasslandswere found to have up to more than 30 species, compared with less than a dozen in the more intensively managed ones. It should be emphasised that floral diversity increases rapidly with a reduction ofmanagement intensity, whether by delaying the first mowing until after 15 June or by replacing mineral fertilisers with organic fertilisers. For instance, in Ardenne region, intensively managed  grasslands under conventional regimes show lower levels of species-richness than intensive organic management (on average 9 vs 15 species observed in temporary fields and 11 vs 15 species observed in permanent fields). In organic farming, floral diversity is higher, with the presence of species such as Anthoxanthum odoratum, Cynosurus cristatus or Achillea millefolium, and more abundant in legumes, with, for example, 15 to 25% white clover coverage versus 5% in conventional intensive grasslands.

Moderate grassland management, with organic nutrient inputs, therefore seems to be a positive factor in strengthening regulating services while maintaining a satisfactory fodder provisioning service (of the order of 800 VEM on average for the first cut). This type of management allows greater floral diversity, including legumes  which contribute positively to (1) the digestibility and nutritional value of forage, (2) the fertility of soil by stimulating the fixation of atmospheric nitrogen by root nodules, (3) carbon sequestration and (4) the provision of food resources for pollinators.

Date of update 30 mai 2017