Changes in biodiversity composition and soil nutrient content with management in a Pyrenean grassland community

We investigated the influence of livestock type on vegetation and biogeochemical cycling in grasslands with the objective of describing differences between agropastoral systems experiencing different managements from a trophic perspective. We sampled grassland plots in the Pyrenees of which four were grazed by sheep and four by cattle. We defined three patch types, based on the specific and functional plant composition: Legume-dominated (mostly by Lotus corniculatus); Grass-dominated (mainly by either Festuca nigrescens or Nardus stricta); and Forb-diverse (with Myosotis sylvatica and a diversity of other species). We sampled both above- and below-ground to obtain information about vegetation, roots (including mycorrhiza colonization) and soil nutrients. The above- and belowground plant biomass depended upon functional components of the patch and on grazing management. Plant allocation to green and dead matter changed between management types. Further, differences in grassland vegetation composition between cattle- and sheep-grazed areas found in previous studies were also confirmed. Higher P and NO3 concentrations in cattle-grazed areas suggest eutrophication under this management, linked with lower mycorrhizal colonisation. Our results therefore confirm patterns in previous studies and provide a deeper insight into the mechanisms of biotic differentiation and biogeochemical processes associated with differences in grazing management.This work was supported by the CARBOAGROPAS (CGL2006-13555-C03-01/BOS) and the OBAMA (CGL2009-13425-C02-01 /BOS) projects from the Spanish Ministry of Education and Science, and Consolider-Ingenio Montes SD2008-00040