Summary• Carbon dioxide and methane (CH 4 ) fluxes were measured in a cutover bog of the Jura Mountains (France) together with biotic and abiotic variables for two entire vegetation periods in order to compare the carbon balance of the bog at three stages of regeneration.• Among all factors, air temperature and vegetation index (including leaf area of vascular plants, bryophyte density and bryophyte desiccation) were the two main determinants of ecosystem respiration and gross photosynthesis at light saturation. ). Methane fluxes accounted for a very small part of the total carbon efflux ( < 2%).• The recovery of vegetation in our naturally regenerating bog was beneficial for the carbon sequestration after the relatively short period of 20 yr.

Neotropical peatlands emit large amounts of methane (CH 4) from the soil surface, but fluxes from tree stems in these ecosystems are unknown. In this study we investigated CH 4 emissions from five tree species in two forest types common to neotropical lowland peatlands in Panama. Methane from tree stems accounted for up to 30% of net ecosystem CH 4 emissions. Peak CH 4 fluxes were greater during the wet season when the water table was high and temperatures were lower. Emissions were greatest from the hardwood tree Campnosperma panamensis, but most species acted as emitters, with emissions declining exponentially with height along the stem for all species. Overall, species identity, stem diameter, water level, soil temperature and soil CH 4 fluxes explained 54% of the variance in stem CH 4 emissions from individual trees. On the landscape level, On the landscape level, the high emissions from C. panamensis forests resulted in that they emitted at 340 kg CH 4 d À1 during flooded periods despite their substantially lower areal cover. We conclude that emission from tree stems is an important emission pathway for CH 4 flux from Neotropical peatlands, and that these emissions vary strongly with season and forest type.

Summary 1Significant areas of temperate bogs have been damaged by peat harvesting but may regenerate. These secondary mires, if well managed, may act as strong C sinks, regulate hydrology and buffer regional climate. 2 The potential effects of bog regeneration will, however, depend on the successful establishment of the principal peat formers -Sphagnum mosses. The influence of hydrology and microclimate on Sphagnum re-growth is well studied but effects of elevated CO 2 and N deposition are not known. 3 We carried out two in-situ experiments in a cutover bog during three growing seasons in which we raised either CO 2 (to 560 p.p.m.) or N (by adding NH 4 NO 3 , 3 g m −2 year −1). The two treatments had contrasting effects on competition between the initial coloniser Polytrichum strictum (favoured by high N) and the later coloniser Sphagnum fallax (favoured by high CO 2 ). 4 Such changes may have important consequences for bog regeneration and hence for carbon sequestration in cutover bogs, with potential feedback on regional hydrological and climatic processes.

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24Climate warming is likely to increase carbon dioxide (CO2) and methane (CH4) 25 emissions from tropical wetlands by stimulating microbial activity, but the magnitude 26 74 5 This is a critical knowledge gap as we do not know if the wealth of data exploring 75 temperature responses of CH4 and CO2 fluxes from higher latitude ecosystems can 76 be transferred to tropical systems. It is for example plausible that tropical wetland 77 microbial communities are adapted to higher temperatures, rendering them less 78 sensitive to elevated temperatures than those in higher latitudes. Alternatively, 79 differences in soil organic matter chemistry between high and low latitude wetlands 80 may result is substantial differences in the temperature response of decomposition 81 and release of GHGs (Lloyd and Taylor, 1994; Bosatta and Ågren, 1999; Fierer et 82 al., 2005). 83 84 Tropical peatlands are under threat from climate change, which could substantially 85 affect their water balance, and resultant CO2 and CH4 emissions (Furukawa et al., 86 2005; Li et al., 2007; Hooijer et al., 2010; Laiho, 2006; IPCC 2013). With regards to 87 climate change, current predictions indicate air temperatures in the neotropics and 88 Southeast Asia will be 3-4C higher by 2100 and 5-7 C higher by 2200 (IPCC, 89 2013). To date precipitation changes in the Amazon region have been associated 90 with wetter wet seasons and drier dry season but there are no strong overall trends 91 for the region (Almeida et al, 2017). In the future precipitation in the neotropics is 92 predicted to decrease by ca. 10% by 2100 (ca. 350 mm less per year) and by 20-93 40% by 2200 (up to 1400 mm less per year) under the Intergovernmental Panel on 94 Climate Change (IPCC) scenario RCP 8.5 (IPCC, 2013) although, model predictions 95 of changes in precipitation patterns are more uncertain than the temperature 96 predictions and patterns varies between inland and coastal areas (Chao et al., 2008;97

We measured the net ecosystem exchange (NEE) and respiration rates and modeled the photosynthesis and respiration dynamics in a cutover bog in the Swiss Jura Mountains during one growing season at three stages of regeneration (29, 42, and 51 years after peat cutting; coded sites A, B, and C) to determine if reestablishment of Sphagnum suffices to restore the C‐sequestration function. From the younger to the older stage Sphagnum cover increased, while net primary Sphagnum production over the growing season decreased (139, 82, and, 67 g m−2 y−1 for A, B, and C respectively), and fen plant species were replaced by bog species. According to our NEE estimations, over the vegetation period site A was a net CO2‐C source emitting 40 g CO2‐C/m2 while sites B and C were accumulating CO2‐C, on average 222 and 209 g CO2‐C/m2, respectively. These differences are due to the higher respiration in site A during the summer, suggesting that early regeneration stages may be more sensitive to a warmer climate. Methane fluxes increased from site A to C in parallel with Eriophorum vaginatum cover and vascular plant leaf area. Our results show that reestablishing a Sphagnum cover is not sufficient to restore a CO2‐sequestrating function but that after circa 50 years the ecosystem may naturally regain this function over the growing season.

and by identifying Zn forms in soils using extended X-ray absorption fine structure 31 (EXAFS) spectroscopy. We distinguished 3 pools of exchangeable Zn: the pool of 32 Zn exchangeable within 1 minute which is observed in all soils, Zn exchangeable on 33 the medium term, and the slowly and not exchangeable Zn. The amount of Zn 34 present in the 2 first pools was similar to the L value measured with T. caerulescens. 35The 3 first steps of the SSE solubilized the 1 st pool and a fraction of the 2 nd pool. 36Most of the 2 nd pool and a fraction of the 3 rd pool were extracted in the 4 th step of 37 the SSE, while the rest of the 3 rd pool was extracted in the final steps of the SSE. 38The EXAFS study conducted on two soils showed that more than half of the Zn was 39 present in species weakly bound to organic compounds and/or outer sphere 40 inorganic and organic complexes. Other species included strongly sorbed Zn species 41 and Zn species in crystalline minerals. The EXAFS study of selected SSE residues 42 showed that the specificity and the efficiency of the extractions depended on the 43 properties of the soil studied. 44 45 Introduction 46

Abstract. There is increasing interest in the measurement of methane (CH4) emissions from tree stems in a wide range of ecosystems so as to determine how they contribute to the total ecosystem flux. To date, tree CH4 fluxes are commonly measured using rigid closed chambers (static or dynamic), which often pose challenges as these are bulky and limit measurement of CH4 fluxes to only a very narrow range of tree stem sizes and shapes. To overcome these challenges we aimed to design and test new semi-rigid stem-flux chambers (or sleeves). We compared the CH4 permeability of the new semi-rigid chambers with that of the traditional rigid chamber approach, in the laboratory and in the field, with continuous flow or syringe injections. We found that the semi-rigid chambers had reduced gas permeability and optimal stem gas exchange surface to total chamber volume ratio (Sc / Vtot) better headspace mixing, especially when connected in a dynamic mode to a continuous flow gas analyser. Semi-rigid sleeves can easily be constructed and transported in multiple sizes, are extremely light, cheap to build and fast to deploy. This makes them ideal for use in remote ecosystems where access logistics is complicated.