Abstract
Peatlands, especially fens, are known to emit methane. Reindeer (Rangifer tarandus) use mires mainly as spring and summer pastures. In this work we observed that adding reindeer droppings to fen peat increased the potential methane production by 40%. This became apparent when droppings originating from reindeer kept in pen or pasture in winter were added to methanogenic fen peat samples. The droppings introduced Methanobacteriaceae (Methanobrevibacter; > 90% of the mcrA MiSeq reads) to the peat, which was originally populated by Methanosarcinaceae, Methanosaetaceae, Methanoregulaceae, Methanobacteriaceae, Methanomassiliicoccaceae, Methanocellaceae and Methanomicrobiaceae. The original community structure did not explain the induced methane production and neither did the origin of the droppings. Instead, the increment in methane production was explained by the increased methanogenic abundance, measured by mcrA qPCR, due to the addition of droppings. The result confirms that methanogens from the reindeer rumen participate in peat methane production. This finding suggests that reindeer grazing may increase methane emissions in northern fens.
Highlights
Reindeer (Rangifer tarandus) use peatlands mainly as spring and summer pastures (Kolari et al, 2019)
The droppings of the pen fed reindeer alone without peat produced almost no methane, regardless of whether the droppings had been kept at +4 ◦C or − 20 ◦C, whereas the droppings of reindeer kept in natural pastures had a methane production rate of 0.0296 (±0.034) nmol CH4 h− 1 g− 1 when kept at +4 ◦C and the freezing of the droppings resulted in a 10-fold decrease of that rate (Fig. 1) which was significant
Reindeer droppings fall on fen surfaces but as reindeer paths show hoof penetration down to 15–20 cm, parts of their droppings are introduced through trampling directly into the wet, anoxic subsurface zone, where methane production activity is high (Peltoniemi et al, 2016)
Summary
Reindeer (Rangifer tarandus) use peatlands mainly as spring and summer pastures (Kolari et al, 2019). As reindeer or caribou (Rangifer tar andus caribou) graze everywhere in the Arctic, their diet may impact the quality of the droppings which, in turn, could be reflected in the methane production rate of the peatland pastures. Another explanation is that the droppings may induce a change in the community structure of the methane producing Archaea in the peat. We evaluated these two main hypotheses in an experiment where reindeer droppings collected from animals kept and fed in pens or grazing in natural pastures were added to peat samples in the laboratory. Three research questions guided our work: 1) is the reindeer diet reflected in the methane pro duction potential of the peat, 2) does the addition of droppings either change or increase the size of the peat methanogenic archaeal commu nity and 3) as reindeer graze all year round, does the freezing of the droppings at a typical artic winter temperature influence the results?
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
