Perceived feasibility of sward management options in permanent grassland of Alpine regions and expected effects on delivery of ecosystem services.

Agriculture in Alpine regions plays an important role for multiple ecosystem services (ES) supplied from permanent grassland (PG). This paper investigates the feasibility of sward renewal, overseeding, and rising plate meters on PG for the Swiss Alpine region and analyses their expected effects on ES supply. Sward renewal and overseeding are management options implemented in response to a decline of grassland yields and nutritive value or sward damage. Rising plate meters focus on increased grass utilisation for improving profitability of grassland farms in a sustainable manner. The aim was to improve the understanding which of these three PG management practices could be promoted to deliver a wide range of agricultural and non-agricultural ESs in the Swiss Alpine region. Through interviews with 75 farmers (including organic and intensive/extensive non-organic farmers) and a Delphi-methodology on a panel of experts (N = 10 experts with different expertise), we found that sward renewal is perceived to have negative effects on biodiversity, carbon storage, flood control, prevention of soil erosion, and prevention of loss of organic matter in Alpine regions. Therefore, sward renewal should not be promoted, although about half of the farmers interviewed had already carried out the practice on plots following severe sward damage in Alpine regions. Overseeding is perceived to have positive effects on biodiversity, prevention of soil erosion, and grass production. Thus, the high level of overseeding that is currently practiced in the Swiss Alpine region is probably sustainable. Rising plate meters do not play a significant role in PG management in the Alpine region because calibration in PG with diverse grassland botanical composition in the Alpine region is too difficult.

Does liming grasslands increase biomass productivity without causing detrimental impacts on net greenhouse gas emissions?

Soil acidification has negative impacts on grass biomass production and the potential of grasslands to mitigate greenhouse gas (GHG) emissions. Through a global review of research on liming of grasslands, the objective of this paper was to assess the impacts of liming on soil pH, grass biomass production and total net GHG exchange (nitrous oxide (N2O), methane (CH4) and net carbon dioxide (CO2)). We collected 57 studies carried out at 88 sites and covering different countries and climatic zones. All of the studies examined showed that liming either reduced or had no effects on the emissions of two potent greenhouse gases (N2O and CH4). Though liming of grasslands can increase net CO2 emissions, the impact on total net GHG emission is minimal due to the higher global warming potential, over a 100-year period, of N2O and CH4 compared to that of CO2. Liming grassland delivers many potential advantages, which justify its wider adoption. It significantly ameliorates soil acidity, increases grass productivity, reduces fertiliser requirement and increases species richness. To realise the maximum benefit of liming grassland, we suggest that acidic soils should be moderately limed within the context of specific climates, soils and management.