Effects of temperature and moisture variability on soil CO2 emissions in European land ecosystems

Abstract:

Soil respiration is one of the largest terrestrial fluxes of carbon dioxide (CO₂) to the atmosphere. Hence, small changes in soil respiration rates could have large effects on atmospheric CO₂. In order to assess CO₂ emissions from diverse European soils under different land-use and climate (soil moisture and temperature) we conducted a laboratory incubation experiment.

Therefore, we incubated soil cores (Ø 7 cm; height 7 cm) from nine European sites which are spread all over Europe; from the United Kingdom (west) to the Ukraine (east) and Italy (south) to Finland (north). In addition these sites can be clearly distinguished between their land use into forests, arable lands, grasslands and one peat land. Soil cores were incubated in a two-factorial experimental design at 5 different temperatures (5, 10, 15, 20, and 25°C) and 6 different moisture contents (5, 20, 40, 60, 80, and 100 % water filled pore space (WFPS)). An automated laboratory incubation measurement system was used to measure CO₂ emissions.

Results show that highest CO₂ emissions occurred with intermediate moisture content (40% to 70%) over all sites. We found that the relationship between CO₂ emissions and temperature could be well described by a Gaussian model (R² ranges from 0.87 to 1) over all sites. In general CO₂ emissions were strongly related with both variables temperature and moisture. Temperature sensitivity (Q₁₀) was negatively correlated with temperature for all land-uses investigated. Moisture sensitivity was calculated as the slope of a quadratic function and showed highest values at very low and high moisture content for all land-uses investigated. Moisture sensitivity was increasing with temperature for all arable lands investigated. All coniferous forest sites investigated showed a strong increase of the temperature sensitivity at lower temperatures at a moisture range of 20 – 40 % WFPS.

In summary our results showed not only the relationship between temperature sensitivity of CO₂ emissions and moisture content for a broad range of land-uses within Europe but also investigated the relationship between moisture sensitivity of CO₂ emissions and temperature for said land-uses for the first time.