Finding sustainable grazing management in tundra ecosystems is becoming increasingly important for northern agriculture. In the Icelandic highlands, past grazing practices have played a major role in the extensive soil erosion, leaving many parts of this tundra rangeland in poor condition. However, following a reduction in sheep numbers, stricter grazing management policies, and a progressive turn to fertilisers for combating soil erosion, the current impacts of grazing practices are not well understood.
In this study we measured the short-term effect of current sheep grazing by comparing the amount of bare ground and aboveground biomass in grazed and ungrazed plots, with and without fertiliser application, in adjacent dwarf-shrub heaths and sparsely vegetated areas, at two sites within and outside the volcanic active zone.
After three years, grazing did not affect the amount of bare ground, but in the fertilised plots grazing consistently reduced plant biomass (mainly graminoids). Fertiliser application can increase grazing intensity, which can counteract the additional biomass accumulation. Consequently, the removal of biomass by sheep needs to be considered when fertilisers are used as part of a strategy to combat erosion.
The article is open access and you can find the full text here.
Reference: Mulloy, T.A., Barrio, I.C., Björnsdóttir, K., Jónsdóttir, I.S., Hik, D.S. (2019) Fertilisers mediate the short-term effects of sheep grazing in the Icelandic highlands. Icelandic Agricultural Sciences, 32: 75-85.
Text by Tara Mulloy, MSc student at Simon Fraser University
Picture: The study addressed the combined effects of fertiliser application and sheep grazing in the highlands of Iceland (photo: Tara Mulloy, Simon Fraser University, 2019)