Maximizing the information obtained from chamber-based greenhouse gas exchange measurements in remote areas

Abstract

Measurements of greenhouse gas (GHG) fluxes, particularly methane (CH4) and nitrous oxide (N2O) in mountain ecosystems are scarce due to the complexity and unpredictable behavior of these gases, in addition to the remoteness of these ecosystems. In this context, we measured CO2, CH4, and N2O fluxes in four semi-natural pastures in the Pyrenees to investigate their magnitude and range of variability. Our interest was to study GHG phenomena at the patch-level, therefore we chose to measure the gas-exchange using a combination of a gas analyzer and manual chambers. The analyzer used is a photoacoustic field gas-monitor that allows multi-gas instantaneous measurements. After implementing quality control and corrections, data was of variable quality. We tackled this by categorizing data as to providing quantitative or only qualitative information:

50% and 59% of all CH4 and N2O data, respectively, provided quantitative information above the detection limit.

We chose not to discard data providing only qualitative information, because they identify highest- and lowest-flux peak periods and indicate the variability of the fluxes, along different altitudes and under different climatic conditions.

We chose not to give fluxes below detection limit a quantitative value but to acknowledge them as values identifying periods with low fluxes.

We would like to thank Helena Sarri and Mercedes Ibañez, for their assistance during field work. We would also like to thank Mari Pihlatie from the University of Helsinki for fruitful discussions and suggestions. This work was funded by the Spanish Science Foundation (FECYT) through the projects CAPAS (CGL2010-22378-C03-01) and BIOGEI (CGL2013-49142-C2-1-R). The project was also developed within the project CAPACITI supported by a Marie Curie Intra European Fellowship within the 7th European Community Framework to NA (PIEF-GA-2010-275855), HD was supported by a FPI fellowship from the Spanish Ministry of Economy and Competitiveness (BES-2011-047009). Funding through the project “Potential for capture or emission of greenhouse gases in agro-pastoral systems” (2012-AGEC-00080) by the Catalan Government is also acknowledged. We are particularly grateful to two anonymous reviewers for improving the paper, through their useful comments and suggestions.