Fritze, Hannu

Hahn, J.

Juottonen, H.

Tuittila, E. S.

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Experimental approach We wanted to find out if high CH4 emissions from rewetted peatland sites could be explained by previous land use as cattle pasture.  We analyzed the effects of dung application (DA) to peat soil on the methanogenic potential and community in three different experimental approaches (Fig.1):  a) DA treatment of peat soil in the laboratory  b) applying dung to three  restored and one pristine  peatland in the field in Finland c) sampling a restored peatland influenced by cattle pasture in Germany  Background Rewetting of drained peatlands aims to recover the biogeochemical processes typical to pristine peatlands. This includes an increase of CH4 emissions.  The potential for very high emissions has been measured in Central-European peatland sites previously used for grazing of cattle.  Results Cattle dung can increase CH4 production and influence the methanogen community of rewetted peat soils 1Natural Resources Institute Finland (Luke), Finland; Viikinkaari 4; 00790 Helsinki;  2University of Eastern Finland  Hahn J1, Juottonen H1, Tuittila ES2 and Fritze H1  mcrA  T-RF (bp) laboratory experiment field experiment cattle pasture 79 C, D, DA C 86 C, DA C, DA 97 C, DA 101 DA C, DA DA 106 D, DA D, DA D 108 C 119 D D D 132 C, DA 141 DA C, D, DA DA 152 C 160 C, DA 199 C, DA DA 210 DA C C, DA 214 D, DA C, D, DA C, D 220 DA C, DA DA 232 DA C, DA C, DA 237 C D, DA 257 C 292 C, DA 371 D, DA D 380 C, DA DA 389 DA 395 DA DA 399 DA 406 C, DA DA 473 C, DA C, DA 492 DA C, DA C, DA Table 1. Occurrence of mcrA TRFs in the samples of dung (D), control peat (C) and peat with dung application (DA) from the laboratory experiment, field experiment and the cattle pasture.  There are no unique control samples for the laboratory experiment as we added fresh dung to the samples from the pastured site for laboratory DA. The very same dung samples were used in the laboratory experiment and the cattle pasture.  The green mcrA-T-RF species was found only in dung and  has no match to known methanogens. The red mcrA-T-RF species were found in dung and dung-treated peat, only. The T-RF with 106bp length  matches with Methanobrevibacter species found in 70 % of all dung sequences.  Figure 3. Correlations between CH4 production potential and mcrA gene copy level in the laboratory (a, n=21) and field experiment (b, n=72) and at the cattle pasture (c, n=11). Figure 4. DCA of mcrA T-RF’s showing the separation of the community of methanogenic archaea between the control site and the site having cattle pasture in Germany. Measured variables We measured CH4 production potentials (Fig. 2), determined the numbers of methanogens by mcrA-qPCR (Fig. 3) and analyzed the methanogen community by mcrA T-RFLP-cloning-sequencing (Fig. 4; Tab. 1)  Conclusions We found  a shift in methanogen community due to DA and a sequence transfer of dung methanogens to the peatland soils. Both might have caused the higher CH4 production potentials after DA.  Our findings indicate that rewetting  of peatlands that have been  previously grazed by cattle might  lead to increased CH4 emissions. Figure 2. Increase of CH4 production potential after dung addition in the laboratory (a, n=84) and  field experiment (b, n=72) and at the cattle pasture (c, n=11). a) b) c) Figure 1. Dung application (DA) treatments were examined in a laboratory experiment (a), a field experiment (b) and at a peatland site with cattle pasture (c). a b c a b c 

Cattle dung can increase CH4 production and influence the methanogen community of rewetted peat soils

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