Peatland pools are tightly coupled to the contemporary carbon cycle.

Peatlands are globally important stores of soil carbon (C) formed over millennial timescales but are at risk of destabilization by human and climate disturbance. Pools are ubiquitous features of many peatlands and can contain very high concentrations of C mobilized in dissolved and particulate organic form and as the greenhouses gases carbon dioxide (CO2 ) and methane (CH4 ). The radiocarbon content (14 C) of these aquatic C forms tells us whether pool C is generated by contemporary primary production or from destabilized C released from deep peat layers where it was previously stored for millennia. We present novel 14 C and stable C (δ13 C) isotope data from 97 aquatic samples across six peatland pool locations in the United Kingdom with a focus on dissolved and particulate organic C and dissolved CO2 . Our observations cover two distinct pool types: natural peatland pools and those formed by ditch blocking efforts to rewet peatlands (restoration pools). The pools were dominated by contemporary C, with the majority of C (~50%-75%) in all forms being younger than 300 years old. Both pool types readily transform and decompose organic C in the water column and emit CO2 to the atmosphere, though mixing with the atmosphere and subsequent CO2 emissions was more evident in natural pools. Our results show little evidence of destabilization of deep, old C in natural or restoration pools, despite the presence of substantial millennial-aged C in the surrounding peat. One possible exception is CH4 ebullition (bubbling), with our observations showing that millennial-aged C can be emitted from peatland pools via this pathway. Our results suggest that restoration pools formed by ditch blocking are effective at preventing the release of deep, old C from rewetted peatlands via aquatic export.

Testate amoebae response and vegetation composition after plantation removal on a former raised bog.

Extensive drainage of peatlands in north-west Europe for the purposes of afforestation for timber production and harvesting has altered the carbon balance and biodiversity value. Large-scale restoration projects aim to reinstate hydrological conditions to keep carbon locked up in the peat and to restart active peat growth. Testate amoebae are an informal grouping of well-studied protists in peatland environments and as microbial consumers play an important role in nutrient and carbon cycling. Using a space for time substitution approach, this study investigated the response of testate amoebae assemblages and vegetation composition after tree removal on a drained raised bog. There was a clear difference in microbial assemblages between open and a chronosequenceof restoration areas. Results suggest microbial recovery after rewetting is a slow process with plant composition showing a faster response than the microbial assemblage. Mixotrophic testate amoebae had not recovered seventeen years following plantation removal and the establishment of Sphagnum mosses in the wetter microforms. These results suggest that vegetation composition and Testate amoeba assemblages respond differently to environmental drivers at forest-to-bog restoration areas. Local physicochemical peat properties were a stronger driver of the testate assemblage compared with vegetation. Complete recovery of microbial assemblages may take place over decadal timescales.

Towards a microbial process-based understanding of the resilience of peatland ecosystem service provisioning - A research agenda.

Peatlands are wetland ecosystems with great significance as natural habitats and as major global carbon stores. They have been subject to widespread exploitation and degradation with resulting losses in characteristic biota and ecosystem functions such as climate regulation. More recently, large-scale programmes have been established to restore peatland ecosystems and the various services they provide to society. Despite significant progress in peatland science and restoration practice, we lack a process-based understanding of how soil microbiota influence peatland functioning and mediate the resilience and recovery of ecosystem services, to perturbations associated with land use and climate change. We argue that there is a need to: in the short-term, characterise peatland microbial communities across a range of spatial and temporal scales and develop an improved understanding of the links between peatland habitat, ecological functions and microbial processes; in the medium term, define what a successfully restored 'target' peatland microbiome looks like for key carbon cycle related ecosystem services and develop microbial-based monitoring tools for assessing restoration needs; and in the longer term, to use this knowledge to influence restoration practices and assess progress on the trajectory towards 'intact' peatland status. Rapid advances in genetic characterisation of the structure and functions of microbial communities offer the potential for transformative progress in these areas, but the scale and speed of methodological and conceptual advances in studying ecosystem functions is a challenge for peatland scientists. Advances in this area require multidisciplinary collaborations between peatland scientists, data scientists and microbiologists and ultimately, collaboration with the modelling community. Developing a process-based understanding of the resilience and recovery of peatlands to perturbations, such as climate extremes, fires, and drainage, will be key to meeting climate targets and delivering ecosystem services cost effectively.

Restoration of afforested peatland: Immediate effects on aquatic carbon loss.

Peatland restoration is undertaken to bring back key peatland ecosystem services, including carbon storage. In the case of drained, afforested blanket peatlands, restoration through drain blocking and tree removal may impact upon aquatic carbon concentrations and export, which needs to be accounted for when considering the carbon benefits of restoration. This study investigated concentrations and export of aquatic carbon from a drained, afforested blanket bog catchment, where 12% of the catchment underwent drain blocking and conifer removal (termed 'forest-to-bog' restoration), and from two control catchments: one in open bog and one that remained afforested. Using a before-after-control-impact (BACI) design, we found no significant increases in concentrations or export of aquatic carbon (DOC, POC or DIC) in the first year following forest-to-bog restoration (i.e. across the whole post-restoration period). However, increased DOC concentrations were observed in the first summer (2015) post-restoration, and seasonally increased DOC export was noted during storm events in the autumn of the same year. The lack of significant effects of forest-to-bog restoration on aquatic carbon export may be a consequence of the small proportion of the catchment (12%) undergoing management. In terms of management, the removal of more of the forestry residues (i.e., brash) may help to mitigate effects on aquatic carbon, by removing a potential DOC and POC source. Restoring small areas at a time (≤12%) should result in minimal aquatic carbon export issues, in contexts similar to the current study.

Annual gaseous carbon budgets of forest-to-bog restoration sites are strongly determined by vegetation composition.

Large areas of naturally open peatland in western Europe were drained and planted with non-native conifers in the twentieth century. Efforts are currently underway to restore many of these sites. Ultimately, forest-to-bog restoration aims to bring back functional peatlands that can sequester carbon but there is a lack of empirical evidence for whether current approaches are effective. Using a chronosequence design, we compared the annual gaseous carbon balance of two forest-to-bog restoration areas with an open area not subject to afforestation. A closed chamber method was used to determine gas fluxes (Net Ecosystem Respiration, Gross Primary Productivity, Net Ecosystem Exchange (NEE) and methane (CH4)) over a twelve-month period for locations spanning the range of peatland microtopography and vegetation communities. Relationships between gas fluxes, vegetation/cover and environmental factors were analysed and regression models used to estimate annual CO2 and CH4 budgets. During the study period, NEE estimates (total gaseous C expressed as CO2-eq) showed a net sink for the unafforested (-102 g C m-2 yr-1) and oldest (-131 g C m-2 yr-1) restoration area (17 years post-restoration 'RES 17 YRS'), whilst the youngest restoration area (6 years post-restoration 'RES 6YRS'), was a net source (35 g C m-2 yr-1). We observed significantly higher CH4 emissions from restoration areas dominated by Eriophorum angustifolium compared with other peatland vegetation types. Sampling points with higher cover of Sphagnum were found to be most effective for C sequestration. Overall, vegetation composition/cover was observed to be an important factor determining C emissions from forest-to-bog restoration areas. These results suggest that restoration is effective in returning the carbon sink function of peatlands damaged by commercial forestry and - depending on restoration techniques - timescales of >10 years may be required.

Capturing Gas Fluxes on Your Phone: An iOS- and Android-based Data-Logging Setup for EGM-4 Environmental Gas Monitoring Systems.

Mobile devices have become increasingly important for field monitoring to improve data capture efficiency, increase storage capacity, and replace heavy equipment. We introduce a quick and straightforward protocol to capture greenhouse gas (GHG) emission rates on mobile devices. We developed our setup on the widely used infrared gas analyzer (IRGA) EGM-4 by PP Systems. This IRGA has a limited internal storage capacity and requires an external device such as a laptop to conduct even modest field sampling. Furthermore, when raw data storage is required, carbon dioxide concentration resolution is reduced by the internal EGM-4 software settings, making the equipment less suitable for high-frequency measurements. Our protocol lets the user bring either an iOS or Android mobile device in to the field to connect to the EGM-4's data stream. For both platforms, a mobile console application was used to read, log, and share flux data. The raw data can be processed in either Python, R, or Matlab using the provided scripts that give the user flexibility to amend further postprocessing steps to obtain GHG fluxes. We demonstrate the flexible applicability of mobile devices for field recording and show that a cost-effective solution can enhance the operational life of superseded field equipment while also increasing the quality of the captured data.

Measuring restoration progress using pore- and surface-water chemistry across a chronosequence of formerly afforested blanket bogs.

During the restoration of degraded bogs and other peatlands, both habitat and functional recovery can be closely linked with nutrient cycling, which is reflected in pore- and surface-water chemistry. Several peatland restoration studies have shown that the time required for recovery of target conditions is slow (>10 years); for heavily-impacted, drained and afforested peatlands of northern Scotland, recovery time is unknown. We monitored pore- and surface-water chemistry across a chronosequence of formerly drained, afforested bog restoration sites spanning 0-17 years, using a space-for-time substitution, and compared them with open blanket bog control sites. Our aims were to measure rate of recovery towards bog conditions and to identify the best suite of water chemistry variables to indicate recovery. Our results show progress in recovery towards bog conditions over a 0-17 year period post-restoration. Elements scavenged by trees (Mg, Na, S) completely recovered within that period. Many water chemistry variables were affected by the restoration process itself, but recovered within 11 years, except ammonium (NH4+), Zn and dissolved organic carbon (DOC) which remained elevated (when compared to control bogs) 17 years post restoration. Other variables did not completely recover (water table depth (WTD), pH), exhibiting what we term "legacy" effects of drainage and afforestation. Excess N and a lowered WTD are likely to slow the recovery of bog vegetation including key bog plants such as Sphagnum mosses. Over 17 years, we measured near-complete recovery in the chemistry of surface-water and deep pore-water but limited progress in shallow pore-water. Our results suggest that at least >17 years are required for complete recovery of water chemistry to bog conditions. However, we expect that newer restoration methods including conifer harvesting (stem plus brash) and the blocking of plough furrows (to increase the WTD) are likely to accelerate the restoration process (albeit at greater cost); this should be evaluated in future studies. We conclude that monitoring pore- and surface-water chemistry is useful in terms of indicating recovery towards bog conditions and we recommend monitoring WTD, pH, conductivity, Ca, NH4+, phosphate (PO43-), K, DOC, Al and Zn as key variables.

Ecological and environmental transition across the forested-to-open bog ecotone in a west Siberian peatland.

Climate change may cause increasing tree cover in boreal peatlands, and the impacts of this encroachment will be noted first at forested-to-open bog ecotones. We investigate key metrics of ecosystem function in five such ecotones at a peatland complex in Western Siberia. Stratigraphic analysis of three cores from one of these transects shows that the ecotone has been dynamic over time with evidence for recent expansion of forested peatland. We observed that the two alternative states for northern boreal peatlands (forested/open) clearly support distinct plant and microbial communities. These in turn drive and respond to a number of feedback mechanisms. This has led to steep ecological gradients across the ecotones. Tree cover was associated with lower water tables and pH, along with higher bulk density, aquatic carbon concentrations, and electrical conductivity. We propose that the conditions found in the forested peatland of Western Siberia make the carbon sink more vulnerable to warmer and drier conditions.

Contributions of the free oxidized and Q(B)-bound plastoquinone molecules to the thermal phase of chlorophyll-a fluorescence.

Variable chlorophyll a (Chl a) fluorescence is composed of a photochemical and a thermal phases of similar amplitudes. The photochemical phase can be induced by a saturating single turnover flash (STF) and reflects the reduction of the Photosystem II (PS II) Q(A) primary electron acceptor. The thermal phase requires multiple turnover flash (MTF) and is somehow related to the reduction of the plastoquinone (PQ) molecules. This article aimed to determine the relative contributions of the Q(B)-bound and the free oxidized PQ molecules to the thermal phase of Chl a fluorescence. We thus measured the interactive effects of exogenous PQ (PQex), of an inhibitor (DCMU) acting at the Q(B) site of PS II and of an artificial quencher, 2-methyl-1,4-naphtoquinone, on Chl a fluorescence levels induced by STF (F(F)) and MTF (F(M)) in spinach thylakoids. We observed that: (1) the incorporation of PQex in thylakoids stimulated photosynthetic electron transport but barely affected F(F) and F(M) in the absence of DCMU; (2) DCMU significantly increased the amplitude of F(F) but slightly quenched F(M); (3) 2-methyl-1,4-naphtoquinone quenched F(M) to a larger-extent than F(F); (4) DCMU increased the quenching effects of PQex on F(F) and F(M) and also, of methyl-1,4-naphtoquinone on F(F). These results indicate that: (1) the Q(B)-bound and the free PQ molecules contribute to about 56% and 25%, respectively, to the thermal phase Chl a fluorescence in dark-adapted thylakoids; and (2) the thermal phase of Chl a fluorescence is more susceptible than the photochemical phase to the non-photochemical quenching effect of oxidized quinones.