Influence of nitrogen deposition on carbon dynamics in peatlands

The impact of high levels of nitrogen deposition from the atmosphere (primarily from the combustion of fossil fuels and transportation) on soil carbon fluxes and carbon sequestration pathways in peatlands are uncertain and limit our understanding of its consequence on peatlands’ role as global carbon sinks. An alteration in peatlands’ natural carbon accumulation process could result in the increased release of CO2 into the atmosphere, potentially increasing the greenhouse effect and contributing to climate change. Recent studies in forest soils have shown that high concentrations of inorganic nitrogen accelerate the activity of key soil enzymes involved in the degradation of easily decomposable litter (low lignin content) but slow down the decomposition of lignin abundant litter. Peatland soils are adapted to slow rates of nitrogen mineralization; therefore increasing the nitrogen supply in these environments may have an even deeper impact on litter quality, potential litter decomposability, and overall carbon storage capacity. The aim of this study is to use plant wax biomarkers as proxies of vegetational change in litter profiles. An alkane and alcohol profile database of peatland vegetation is currently being characterized for comparison with samples taken from the Whim Moss experimental site (Edinburgh) where different levels of nitrogen has been added to peatland soil since 2002. A temporal study combining the MicroResp technique (community level physiological profiles) and enzyme activity assays is considered to look at the effect of litter compositional changes on soil microbial diversity and biological activity. To better understand how nitrogen deposition in peatland soil affects the mechanisms controlling carbon storage, the incorporation of stable isotope labelling (13C) would allow direct determination of the fate of carbon into the different carbon pools and better pin-point the changes in litter composition

The assimilation and retention of carbon in upland heath plant communities typical of contrasting management regimes : a 13C tracer study

Peer reviewedPublisher PD

Net carbon dioxide emissions from an eroding Atlantic blanket bog

The net impact of greenhouse gas emissions from degraded peatland environments on national Inventories and subsequent mitigation of such emissions has only been seriously considered within the last decade. Data on greenhouse gas emissions from special cases of peatland degradation, such as eroding peatlands, are particularly scarce. Here, we report the first eddy covariance-based monitoring of carbon dioxide (CO2) emissions from an eroding Atlantic blanket bog. The CO2 budget across the period July 2018–November 2019 was 147 (± 9) g C m−2. For an annual budget that contained proportionally more of the extreme 2018 drought and heat wave, cumulative CO2 emissions were nearly double (191 g C m−2) of that of an annual period without drought (106 g C m−2), suggesting that direct CO2 emissions from eroded peatlands are at risk of increasing with projected changes in temperatures and precipitation due to global climate change. The results of this study are consistent with chamber-based and modelling studies that suggest degraded blanket bogs to be a net source of CO2 to the atmosphere, and provide baseline data against which to assess future peatland restoration efforts in this region

Peatland restoration and potential emissions savings on agricultural land: an evidence assessment

Peatland restoration has a significant role in tackling the global climate emergency and helping Scotland meet its ambitious climate change targets. Globally, peatlands are the largest natural terrestrial carbon store, containing about 25% of global soil carbon. However, they have been damaged by overexploitation. The Scottish Government has committed to restoring 250,000 hectares of peatland in Scotland by 2030. About a quarter of Scotland’s area is covered in peat, storing over 3 billion tonnes of carbon. Peat also provides a range of other co-benefits. Changing some current uses of peatland, particularly for agriculture, may lead to significant savings in greenhouse gas (GHG) emissions and offer some of the highest per hectare emissions savings. This report assesses the current evidence for the potential for emissions savings from re-wetting peatland currently used for agriculture in Scotland and explores alternative uses that might provide an economic return

UK GHG Flux Network – Peatlands

Peatlands occupy 12% of the UK territory and can store large amounts of carbon (C). However, drainage, peat extraction, and other management activities have turned these ecosystems into greenhouse gas (GHG) emitters. Currently, peatlands account for ~ 4% of the UK’s total annual GHG emissions. Eddy covariance is considered the best method to measure landscape scale GHG exchange (CO2, CH4, N2O), between the Earth’s surface and the atmosphere. Recently many flux towers have been installed on UK peatlands under different land-use and in different condition, with some undergoing restoration. In total there are currently 30 operating, with 9 in Scotland (SCO2FLUX managed by The James Hutton Institute, JHI) and 21 across England, Wales and Northern Ireland (managed by UKCEH), including the Auchencorth Moss ICOS site. As part of the projects, NERC-MOTHERSHIP and SRC-CENTREPEAT, these peatland sites are being harmonised into a network. The data is being analysed using standard protocols in order to generate a powerful dataset to examine the exchange of CO2 and CH4 over UK peatlands. Some of the topics being investigated are: the spatial and temporal variability of emissions for all peatland classifications; the main drivers and controlling mechanisms of GHG exchange, such as the effect of water table depth on gas exchange and restoration impacts (e.g. raising water levels in agricultural peatlands); the value and effectiveness of restoration techniques (e.g. the timeline of recovery in the transition from forest to bog); improving the modelling of peatlands in JULES and other land-surface models; ground-proofing data for Earth observation techniques; assessing the contribution of peatlands to achieving net zero; examining the impact of wildfire on restoration from forest to bog. An overview of the network of sites and some highlights of the analysis to date will be presented

Using spectral indices to estimate water content and GPP in Sphagnum moss and other peatland vegetation

Peatlands provide important ecosystem services including carbon stroage and biodiversity conservation. Remote sensing shows potential for monitoring peatlands, but most off-the-shelf data produces are developed for unsaturated environments and it is unclear how well they can perform in peatland ecosystems. Sphagnum moss is an important peatland genus with specific characteristics which can affect spectral reflectance, and we hypothesized that the prevalence of Sphagnum in a peatland could affect the spectral signature of the area. This study combines results from both laboratory and field experiments to assess the relationship between spectral indices and the moisture content and GPP of peatland (blanket bog) vegetation species. The aim was to consider how well the selected indices perform under a range of conditions, and whether Sphagnum has a significant impact on the relationships tested. We found that both water indices tested (NDWI and fWBI) were sensitive to the water content changes in Sphagnum moss in the laboratory, and there was little difference between them. Most of the vegetation indices tested (the NDVI, EVI, SIPI and CIm) were found to have a strong relationship with GPP both in the laboratory and in the field. The NDVI and EVI are useful for large-scale estimation of GPP, but are sensitive to the proportion of Sphagnum present. The CIm is less affected by different species proportions and might therefore be the best to use in areas where species cover is unknown. The PRI is shown to be best suited to small-scale studies of single species

FTIR spectroscopy can predict organic matter quality in regenerating cutover peatlands.

International audienceVegetational changes during the restoration of cutover peatlands leave a legacy in terms of the organic matter quality of the newly formed peat. Current efforts to restore peatlands at a large scale therefore require low cost, and high throughout, techniques to monitor the evolution of organic matter. In this study, we assessed the Fourier Transform Infrared (FTIR) spectra of the organic matter in peat samples at various stages of peatland regeneration from five European countries. Using predictive partial least squares analyses, we were able to reconstruct both peat C:N ratio and carbohydrate signatures, but not the micromorphological composit ion of vegetation remains, from the FTIR datasets. Despite utilising different size fractions, both carbohydrate (< 200 μm fraction) and FTIR (bulk soil) analyses report on the composition of plant cell wall constituents in the peat and therefore essentially reveal the composition of the parent vegetational material. This suggests that FTIR analysis of peat may be used successfully for evaluation of the present and future organic matter composition of peat in monitoring of restoration efforts

The potential for modelling peatland habitat condition in Scotland using long-term MODIS data

Funding: All James Hutton Institute authors are supported by the Scottish Government’s Rural and Environment Research and Analysis Directorate under the current Strategic Research Programme (2016-2021). Sally Johnson, Patricia Bruneau and Louise Ross did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors for this project. The peat spatial extent model was created in part within a UK Government – Department for Business, Energy and Industrial Strategy-funded project (TRN860/07/2014, Scoping the use of the methodology set out in Chapters 2 and 3 of the ‘2013 Supplement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories: Wetlands in the UK GHG Inventory: Land Use, Land Use Change and Forestry (LULUCF)), with further updates created within the Strategic Research Programme (2016-2021) funding.Peer reviewedPostprin

Assessing the reliability of peatland GPP measurements by remote sensing: from plot to landscape scale

Estimates of peatland carbon fluxes based on remote sensing data are a useful addition to monitoring methods in these remote and precious ecosystems, but there are questions as to whether large-scale estimates are reliable given the small-scale heterogeneity of many peatlands. Our objective was to consider the reliability of models based on Earth Observations for estimating ecosystem photosynthesis at different scales using the Forsinard Flows RSPB reserve in Northern Scotland as our study site. Three sites across the reserve were monitored during the growing season of 2017. One site is near-natural blanket bog, and the other two are at different stages of the restoration process after removal of commercial conifer forestry. At each site we measured small (flux chamber) and landscape scale (eddy covariance) CO2 fluxes, small scale spectral data using a handheld spectrometer, and obtained corresponding satellite data from MODIS. The variables influencing GPP at small scale, including microforms and dominant vegetation species, were assessed using exploratory factor analysis. A GPP model using land surface temperature and a measure of greenness from remote sensing data was tested and compared to chamber and eddy covariance CO2 fluxes; this model returned good results at all scales (Pearson’s correlations of 0.57 to 0.71 at small scale, 0.76 to 0.86 at large scale). We found that the effect of microtopography on GPP fluxes at the study sites was spatially and temporally inconsistent, although connected to water content and vegetation species. The GPP fluxes measured using EC were larger than those using chambers at all sites, and the reliability of the TG model at different scales was dependent on the measurement methods used for calibration and validation. This suggests that GPP measurements from remote sensing are robust at all scales, but that the methods used for calibration and validation will impact accuracy