Greenhouse gas budget (CO2, CH4 and N2O) of intensively managed grassland following restoration. (10th February 2014)

• Record Type: Journal Article
• Authors: Merbold, Lutz; Eugster, Werner; Stieger, Jacqueline; Zahniser, Mark; Nelson, David; Buchmann, Nina
• Is Part Of: Global change biology. Volume 20:Number 6(2014:Jun.)
• Page Start: 1913
• Page End: 1928
• Publication Date: 2014-02-10
• Subjects: Climatic changes -- Environmental aspects -- Periodicals; Troposphere -- Environmental aspects -- Periodicals; Biodiversity conservation -- Periodicals; Eutrophication -- Periodicals; 551.5
• DOI: 10.1111/gcb.12518
• Languages: English
• ISSNs: 1354-1013

Abstract

<abstract abstract-type="main" id="gcb12518-abs-0001"> <title>Abstract</title> <p>The first full greenhouse gas (GHG) flux budget of an intensively managed grassland in Switzerland (Chamau) is presented. The three major trace gases, carbon dioxide (CO<sub>2</sub>), methane (CH<sub>4</sub>), and nitrous oxide (N<sub>2</sub>O) were measured with the eddy covariance (EC) technique. For CO<sub>2</sub> concentrations, an open‐path infrared gas analyzer was used, while N<sub>2</sub>O and CH<sub>4</sub> concentrations were measured with a recently developed continuous‐wave quantum cascade laser absorption spectrometer (QCLAS). We investigated the magnitude of these trace gas emissions after grassland restoration, including ploughing, harrowing, sowing, and fertilization with inorganic and organic fertilizers in 2012. Large peaks of N<sub>2</sub>O fluxes (20–50 nmol m<sup>−2</sup> s<sup>−1</sup> compared with a <5 nmol m<sup>−2</sup> s<sup>−1</sup> background) were observed during thawing of the soil after the winter period and after mineral fertilizer application followed by re‐sowing in the beginning of the summer season. Nitrous oxide (N<sub>2</sub>O) fluxes were controlled by nitrogen input, plant productivity, soil water content and temperature. Management activities led to increased variations of N<sub>2</sub>O fluxes up to 14 days after the management event as compared with background fluxes measured during periods without management (<5 nmol m<sup>−2</sup> s<sup>−1</sup>). Fluxes of CO<sub>2</sub> remained small until full plant development in early summer 2012. In contrast, methane emissions showed only minor variations over time. The annual GHG flux budget was dominated by N<sub>2</sub>O (48% contribution) and CO<sub>2</sub> emissions (44%). CH<sub>4</sub> flux contribution to the annual budget was only minor (8%). We conclude that recently developed multi‐species QCLAS in an EC system open new opportunities to determine the temporal variation of N<sub>2</sub>O and CH<sub>4</sub> fluxes, which further allow to quantify annual emissions. With respect to grassland restoration, our study emphasizes the key role of N<sub>2</sub>O and CO<sub>2</sub> losses after ploughing, changing a permanent grassland from a carbon sink to a significant carbon source.</p> </abstract>