Stability of grazed patches on rough fescue grasslands

Abstract

Continuous stocking usually leads to the formation of grazed patches. However, the effect of patches on the grassland community is related to their stability. Therefore, we studied the spatial stability of grazed patches on Rough Fescue Grasslands by mapping forage removal classes on 10 sites over a 4-year period, testing stability using the Kappa index (K), and characterizing the soils and vegetation of overgrazed and undergrazed patches. Spatial stability of grazed patches between consecutive years was good (K is greater than or equal to 0.26) on sites experiencing low grazing pressure. However, on sites having high grazing pressure, spatial stability was less consistent between consecutive years (0>K is lesser than or equal to 0.45) and low over a 4-year period (K is lesser than or equal to 0.10). Overgrazed patches were dominated by grazing-resistant seral species, but undergrazed patches were dominated by climax species. Rough fescue (Festuca scabrella) and Parry oat grass (Danthonia parryi) plants were 50% shorter, and forage production was about 35% less, on overgrazed than on undergrazed patches. Soil organic matter, carbohydrates, and depth of Ah horizon were significantly greater on undergrazed patches but urease activity, NO3-N, NH4, and available phosphorus were greater on overgrazed patches. Overgrazed and undergrazed patches were stable in the long term, although patch boundaries fluctuated.