Comparison of soil greenhouse gas fluxes from extensive and intensive grazing in a temperate maritime climate

Abstract

Greenhouse gas (GHG) fluxes from a seminatural, extensively sheep grazed drained moorland and intensively sheep grazed fertilised grassland in SE Scotland were compared over 4 yr (2007–2010). Nitrous oxide and CH<sub>4</sub> fluxes were measured by static chambers, respiration from soil including ground vegetation by a flow through chamber and the net ecosystem exchange of CO<sub>2</sub> by eddy covariance. All GHG fluxes displayed high temporal and interannual variability. Temperature, radiation, water table height and precipitation could explain a significant percentage of seasonal and interannual variations. Greenhouse gas fluxes were dominated by the net ecosystem exchange of CO<sub>2</sub>, emissions of N<sub>2</sub>O from the grazed grassland (384 g CO<sub>2eq</sub> m<sup>−2</sup> yr<sup>−1</sup>) and emissions of CH<sub>4</sub> from ruminant fermentation (147 g CO<sub>2eq</sub> m<sup>−2</sup> yr<sup>−1</sup>). Methane emissions from the moorland were small (6.7 g CO<sub>2eq</sub> m<sup>−2</sup> yr<sup>−1</sup>). Net ecosystem exchange of CO<sub>2</sub> and respiration were much larger on the productive fertilised grassland (−1624 and +7157 g CO<sub>2eq</sub> m<sup>−2</sup> yr<sup>−1</sup>, respectively) than the seminatural moorland (−338 and +2554 g CO<sub>2eq</sub> m<sup>−2</sup> yr<sup>−1</sup>, respectively). Large CH<sub>4</sub> and N<sub>2</sub>O losses from the grazed grassland counteracted the CO<sub>2</sub> uptake by 35%, whereas the small N<sub>2</sub>O and CH<sub>4</sub> emissions from the moorland did only impact the NEE by 2%.The 4 yr average GHG budget for the grazed grassland was 1006 g CO<sub>2eq</sub> m<sup>−2</sup> yr<sup>−1</sup> and 331 g CO<sub>2eq</sub> m<sup>−2</sup> yr<sup>−1</sup> for the moorland

The use of biogeochemical models to evaluate mitigation of greenhouse gas emissions from managed grasslands

“…According to the median values, the G5 site reached the highest amount of C sequestration (~113.7 g C m −2 yr −1 ) at LD 50 N 0 . The general observation from the modelled sites of increasingly negative NEE in response to increasing N inputs is consistent with experimental observations that report increases in the flow of C to the soil in response to long-term fertilizer N use Skiba et al, 2013). For the period during which the C is sequestered, it is removed from the atmosphere and does not contribute to global warming.…”

The nitrogen, carbon and greenhouse gas budget of a grazed, cut and fertilised temperate grassland

“…Nitrous oxide emissions are influenced by both management and environmental conditions (Flechard et al, 2007, Bell et al, 2015Cowan et al, 2015). In our study N 2 O fluxes showed typical temporal variations with high N 2 O peaks after N application decreasing to background levels after < 1 to 20 days, increased losses during wetter periods, and reduced losses during the colder winter months (Skiba et al, 2013). Spatial variability was high due to the uneven distribution of excreta and urine and uneven soil compaction from grazing animals .…”

“…The DELTA system comprised of a denuder filter sampling train, an air pump (providing a sampling flow rate of 0.2-0.4 L min -1 ) and a high sensitivity dry gas meter to record sampled volumes (Tang et al, 2009) set at 1.5 m height above ground. N dry deposition fluxes were calculated using the average flux from four different inferential models; the UK CBED scheme (Concentration Based Estimated Deposition technique (Smith et al, 2000), the Dutch IDEM model (Bleeker, 2000), (Erisman et al, 1994), the dry deposition module of the Environment Canada model CDRY (Zhang et al, 2001;Zhang et al, 2003) and the surface exchange scheme EMEP (Simpson et al, 2003;Tuovinen et al, 2009), as described in detail by Flechard et al were measured using manual closed static chambers (Clayton et al,1994, Skiba et al, 2013 .…”

Carbon dynamics and environmental controls of a hilly tea plantation in Southeast China

“…Fertilizer addition is another management factor that affects the carbon dynamics in tea plantations, which will stimulate plant growth and microbial activity (Ammann, Flechard, Leifeld, Neftel, & Fuhrer, ; Schmitt, Bahn, Wohlfahrt, Tappeiner, & Cernusca, ; Skiba et al, ; Zeeman et al, ). Multiple studies reported that fertilizer additions will increase carbon uptakes (Eze et al, ; Moinet et al, ; Peichl, Leahy, & Kiely, ) or inhibit soil respiration and microbial respiration (Bowden, Davidson, Savage, Arabia, & Steudler, ; Janssens et al, ; Olsson, Linder, Giesler, & Hogberg, ; Ramirez, Craine, & Fierer, ), but other studies reported that the addition of N fertilizer results in a large carbon loss by the increase in soil microbial activity (Fang et al, ).…”