Quantifying Beetle-Mediated Effects on Gas Fluxes from Dung Pats

Atte Penttilä,Eleanor M Slade,Asko Simojoki,Kari Minkkinen,Terhi Riutta,Tomas Roslin,Dorian Q Fuller

doi:10.1371/journal.pone.0071454

Atte Penttilä, Eleanor M Slade + Show 5 more

Open Access

https://doi.org/10.1371/journal.pone.0071454

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Journal: PloS one	Publication Date: Aug 7, 2013
Citations: 107	License type: CC BY 4.0

Affiliation: University of Helsinki, University of Oxford

Abstract

Agriculture is one of the largest contributors of the anthropogenic greenhouse gases (GHGs) responsible for global warming. Measurements of gas fluxes from dung pats suggest that dung is a source of GHGs, but whether these emissions are modified by arthropods has not been studied. A closed chamber system was used to measure the fluxes of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) from dung pats with and without dung beetles on a grass sward. The presence of dung beetles significantly affected the fluxes of GHGs from dung pats. Most importantly, fresh dung pats emitted higher amounts of CO2 and lower amounts of CH4 per day in the presence than absence of beetles. Emissions of N2O showed a distinct peak three weeks after the start of the experiment – a pattern detected only in the presence of beetles. When summed over the main grazing season (June–July), total emissions of CH4 proved significantly lower, and total emissions of N2O significantly higher in the presence than absence of beetles. While clearly conditional on the experimental conditions, the patterns observed here reveal a potential impact of dung beetles on gas fluxes realized at a small spatial scale, and thereby suggest that arthropods may have an overall effect on gas fluxes from agriculture. Dissecting the exact mechanisms behind these effects, mapping out the range of conditions under which they occur, and quantifying effect sizes under variable environmental conditions emerge as key priorities for further research.

Highlights

Climate change is one of the greatest drivers of environmental modification worldwide [1], with agriculture and food production being major sources of the greenhouse gases (GHGs) responsible for global warming [2], [3]
This study is, to our knowledge, the first to explore the effects of arthropods on GHG fluxes from dung pats
Three weeks after the start of the experiment, emissions of N2O showed a distinct peak in the presence of beetles – a pattern not detected in the treatments without dung beetles

Summary

Introduction

Climate change is one of the greatest drivers of environmental modification worldwide [1], with agriculture and food production being major sources of the greenhouse gases (GHGs) responsible for global warming [2], [3]. Of all anthropogenic GHG emissions, 18% are produced by cattle farming – of anthropogenic nitrous oxide (N2O) and methane (CH4) emissions, the corresponding figures are 65% and 35–50%, respectively [2]. Processes contributing to the decomposition of dung, and to associated gas fluxes, are of key interest in assessing gas fluxes from cattle farming. While recent findings suggest that the activity of earthworms may increase emissions of N2O and CO2 from dung pats [13], [14], and increase the rate of CH4 production in soils [15], [16], the potential for other invertebrates to modify emissions of GHGs is little explored (but see [17,18,19])

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