Greenhouse gas emissions from European soils under different land use: effects of soil moisture and temperature

In order to estimate potential greenhouse gas flux rates from soils under different land use and climate, and to particularly assess the influence of soil temperature and soil moisture, we measured fluxes of nitrous oxide (N2O), nitric oxide (NO), carbon dioxide (CO2) and methane (CH4) from intact soil cores obtained from 13 European sites under controlled laboratory conditions. The soils covered the different climates of Europe and included four different land-use types: croplands, forests, grasslands and wetlands. In a two-factorial experimental design, the soil cores were incubated under four temperatures (5-20 degrees C) and water contents (20-80% water-filled pore space). We found a non-linear increase of N2O, NO and CO2 emissions with increasing temperature. Nitrous oxide emissions were positively correlated with soil moisture, while NO emission and CH4 oxidation rates were negatively correlated with soil moisture. Maximum CO2 emissions occurred at intermediate soil moisture. Different land-use types strongly affected greenhouse gas fluxes. Nitrous oxide and CO2 emissions were highest in grassland soils, while NO emissions were highest in forest soils. In grasslands, high soil microbial activity stimulated by high carbon (C) and nitrogen (N) contents, dense root systems and high C input from above-ground decaying biomass was the most likely cause for high N2O and CO2 emissions. High NO emissions from forest soils were mainly attributed to low pH and high soil porosity. Northern soils showed the greatest capacity to take up CH4 under warmer and dryer soil conditions. Nitric oxide emissions were positively correlated with N input.