Abstract. The Amazon plays a critical role in global atmospheric budgets of methane (CH 4 ) and nitrous oxide (N 2 O). However, while we have a relatively good understanding of the continental-scale flux of these greenhouse gases (GHGs), one of the key gaps in knowledge is the specific contribution of peatland ecosystems to the regional budgets of these GHGs. Here we report CH 4 and N 2 O fluxes from lowland tropical peatlands in the Pastaza-Marañón foreland basin (PMFB) in Peru, one of the largest peatland complexes in the Amazon basin. The goal of this research was to quantify the range and magnitude of CH 4 and N 2 O fluxes from this region, assess seasonal trends in trace gas exchange, and determine the role of different environmental variables in driving GHG flux. Trace gas fluxes were determined from the most numerically dominant peatland vegetation types in the region: forested vegetation, forested (short pole) vegetation, Mauritia flexuosadominated palm swamp, and mixed palm swamp. Data were collected in both wet and dry seasons over the course of four field campaigns from 2012 to 2014. Diffusive CH 4 emissions averaged 36.05 ± 3.09 mg CH 4 -C m −2 day −1 across the entire dataset, with diffusive CH 4 flux varying significantly among vegetation types and between seasons. Net ebullition of CH 4 averaged 973.3 ± 161.4 mg CH 4 -C m −2 day −1 and did not vary significantly among vegetation types or between seasons. Diffusive CH 4 flux was greatest for mixed palm swamp (52.0 ± 16.0 mg CH 4 -C m −2 day −1 ), followed by M. flexuosa palm swamp (36.7 ± 3.9 mg CH 4 -C m −2 day −1 ), forested (short pole) vegetation (31.6 ± 6.6 mg CH 4 -C m −2 day −1 ), and forested vegetation (29.8 ± 10.0 mg CH 4 -C m −2 day −1 ). Diffusive CH 4 flux also showed marked seasonality, with divergent seasonal patterns among ecosystems. Forested vegetation and mixed palm swamp showed significantly higher dry season (47.2 ± 5.4 mg CH 4 -C m −2 day −1 and 85.5 ± 26.4 mg CH 4 -C m −2 day −1 , respectively) compared to wet season emissions (6.8 ± 1.0 mg CH 4 -C m −2 day −1 and 5.2 ± 2.7 mg CH 4 -C m −2 day −1 , respectively). In contrast, forested (short pole) vegetation and M. flexuosa palm swamp showed the opposite trend, with dry season flux of 9.6 ± 2.6 and 25.5 ± 2.9 mg CH 4 -C m −2 day −1 , respectively, versus wet season flux of 103.4 ± 13.6 and 53.4 ± 9.8 mg CH 4 -C m −2 day −1 , respectively. These divergent seasonal trends may be linked to very high water tables (> 1 m) in forested vegetation and mixed palm swamp during the wet season, which may have constrained CH 4 transport across the soil-atmosphere interface. Diffusive N 2 O flux was very low (0.70 ± 0.34 µg N 2 O-N m −2 day −1 ) and did not vary significantly among ecosystems or between seasons. We conclude that peatlands in the PMFB are large and regionally significant sources of atmospheric CH 4 that need to be better accounted for in regional emissions inventories. In contrast, N 2 O flux was negligible, suggesting that this region does not make a significant contribut...

46Our limited knowledge of the size of the carbon pool and exchange fluxes in forested lowland tropical 47 peatlands represents a major gap in our understanding of the global carbon cycle. Peat deposits in 48 several regions (e.g. the Congo Basin, much of Amazonia) are only just beginning to be mapped and 49 characterised. Here we consider the extent to which methodological improvements and improved 50 coordination between researchers could help to fill this gap. We review the literature on measurement 51 of the key parameters required to calculate carbon pools and fluxes, including peatland area, peat bulk 52 density, carbon concentration, above-ground carbon stocks, litter inputs to the peat, gaseous carbon 53 exchange, and waterborne carbon fluxes. We identify areas where further research and better 54 3 coordination are particularly needed in order to reduce the uncertainties in estimates of tropical 55 peatland carbon pools and fluxes, thereby facilitating better-informed management of these 56 exceptionally carbon-rich ecosystems. 57

<p><strong>Abstract.</strong> Here we report methane (CH<sub>4</sub>) and nitrous oxide (N<sub>2</sub>O) fluxes from lowland tropical peatlands in the Pastaza-Marañón foreland basin (PMFB) in Peru, one of the largest peatland complexes in the Amazon basin. Trace gas fluxes were sampled from the most numerically-dominant peatland vegetation types in the region: forested vegetation, forested (short pole) vegetation, Mauritia flexuosa-dominated palm swamp, and mixed palm swamp. Data were collected in both wet and dry seasons over the course of four field campaigns from 2012 to 2014. Peatlands in the PMFB were large and regionally significant sources of atmospheric CH<sub>4</sub>, emitting 36.05 ± 3.09 mg CH<sub>4</sub>-C m<sup>−2</sup> d<sup>−1</sup>. CH<sub>4</sub> emissions varied significantly among vegetation types and between seasons. CH<sub>4</sub> fluxes were greatest for mixed palm swamp (52.0 ± 16.0 mg CH<sub>4</sub>-C m<sup>−2</sup> d<sup>−1</sup>), followed by <i>M. flexuosa</i> palm swamp (36.7 ± 3.9 mg CH<sub>4</sub>-C m<sup>−2</sup> d<sup>−1</sup>), forested (short pole) vegetation (31.6 ± 6.6 mg CH<sub>4</sub>-C m<sup>−2</sup> d<sup>−1</sup>), and forested vegetation (29.8 ± 10.0 mg CH<sub>4</sub>-C m<sup>−2</sup> d<sup>−1</sup>). CH<sub>4</sub> fluxes also showed marked seasonality, with divergent seasonal flux patterns among ecosystems. Forested vegetation and mixed palm swamp showed significantly higher dry season (47.2 ± 5.4 mg CH<sub>4</sub>-C m<sup>−2</sup> d<sup>−1</sup> and 85.5 ± 26.4 mg CH<sub>4</sub>-C m<sup>−2</sup> d<sup>−1</sup>, respectively) compared to wet season emissions (6.8 ± 1.0 mg CH<sub>4</sub>-C m<sup>−2</sup> d<sup>−1</sup> and 5.2 ± 2.7 mg CH<sub>4</sub>-C m<sup>−2</sup> d<sup>−1</sup>, respectively). In contrast, forested (short pole) vegetation and <i>M. flexuosa</i> palm swamp showed the opposite trend, with dry season fluxes of 9.6 ± 2.6 and 25.5 ± 2.9 mg CH<sub>4</sub>C m<sup>−2</sup> d<sup>−1</sup>, respectively, versus wet season fluxes of 103.4 ± 13.6 and 53.4 ± 9.8 mg CH<sub>4</sub>-C m<sup>−2</sup> d<sup>−1</sup>, respectively. Nitrous oxide fluxes were negligible (0.70 ± 0.34 µg N<sub>2</sub>O-N m<sup>−2</sup> d<sup>−1</sup>), and did not vary significantly among ecosystems or between seasons.</p>

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