Protecting our peatlands - short summary of the 10-year Peatland- ES-UK report.

A landmark project studying moorland management has released its ten-year results. Peatland-ES-UK is a University of York project designed to address many of the key questions that drive the debate around moorland management – especially prescribed heather burning, which is often associated with management for red grouse. What impact does moorland vegetation management have on peatland? Can active bogs be maintained under the different management approaches, so they function as healthy ecosystems that support biodiversity, store carbon and lay down peat? Peatland-ES-UK addressed these and other questions using a robust scientific design to give reliable answers. The results so far are findings from the first half of a long-term study. It is vital that the work continues for at least the length of a complete management cycle of about 20 years

Protecting our peatlands. A summary of ten years studying moorland management as part of Peatland-ES-UK: heather burning compared to mowing or uncut approaches.

The presented results are the findings from the first half of a long-term study. Although Peatland-ES-UK has already continued for longer than nearly all other moorland research, it is important that the work covers at least the length of a complete management cycle. To produce results that are robust and long-term enough to guide moorland management policy, we plan to continue the project for another decade. This was the conclusion when our Defra project report9 was reviewed by external scientists after five years, and it remains the case. However, the results to date suggest some very interesting and important findings, which may begin to help any interested parties who are confused by the seeming contradictions in the science previously. All three management approaches were able to support active, healthy peatlands in which peat can grow and carbon can be stored, which is also the finding from some other long-term studies6. Both burning and mowing release considerable amounts of carbon during or in the first years after management, but this is counteracted by increased absorption later on. Short-term assessments are therefore misleading. Heather management also seems to increase biodiversity and maintain higher water tables in the longer term, compared to areas of unmanaged heather. Where a site is wet enough to use prescribed burning, this seems to be the most suitable option to allow carbon storage, peat growth, reduce heather dominance, increase biodiversity and keep the peatland wet. Where a site is drier, mowing could be more appropriate and may help keep the site wetter in the short-term. This threshold sits at a water table of around 12 cm below the peat surface

A critical review of the IUCN UK Peatland Programme’s “Burning and Peatlands” Position Statement

Despite substantial contrary evidence, there has been a growing tendency to present prescribed vegetation burning as a management practice that is always damaging to peatland ecosystems in the UK. This is exemplified by the “Burning and Peatlands” position statement published by the International Union for Conservation of Nature UK Peatland Programme. Indeed, while we strongly agree with several of the statements made within this position statement, it also contains a series of unverified assertions and misleading arguments that seemingly serve to simplify the narrative and paint prescribed burning as a wholly damaging peatland management tool. Given that this position statement is published by one of the UK’s most prominent peatland conservation organisations, it is likely to be consulted when debating upland land use policy. Therefore, for the benefit of policymakers, we provide a point-by-point critical review of the “Burning and Peatlands” position statement. We also discuss several further points for researchers and policymakers to consider that are consistently ignored by those attempting to simplify the narrative about prescribed burning. Our aim in producing this discussion paper is to encourage the research and policy community to move towards an evidence-based position about prescribed burning impacts on UK peatlands

An outline summary document of the current knowledge about prescribed vegetation burning impacts on ecosystem services compared to alternative mowing or no management

Despite substantial contrary evidence, there has been a growing tendency to present prescribed burning as a management practice that is only ever damaging to peatland ecosystems in the UK (Thompson et al. 2016; Natural England 2019; Wild Justice 2019). This is exemplified by the recently released “Burning and Peatlands” position statement by the IUCN UK Peatland Programme (IUCN 2020). Indeed, while we strongly agree with several of the statements made within this position statement, it also contains a series of unverified assertions and misleading arguments that serve to simplify the narrative and paint prescribed burning as a peatland management tool that is only ever damaging. Given that this position statement is published by one of the UK’s most prominent peatland conservation organisations, it is likely to be consulted when debating and designing upland land use policy. Therefore, for the benefit of policymakers, we provided a point-by-point critical review of the “Burning and Peatlands” position statement (Ashby & Heinemeyer, 2021). We also discuss several further points that should be considered by practitioners and policymakers when inferring the impact of prescribed burning. We are neither pro nor anti burning; our aim in producing this summary document is to encourage robust research and evidence assessments and support the practitioner and policy community to move towards an evidence-based position about management impacts on UK upland peatlands, which considers burning as part of several options that can be deployed depending on site conditions and context (i.e. the right tool in the right place for the right reason). Given the uncertainties within the evidence base and practicalities of conducting robust experimental research, we suggest land managers follow an adaptive management approach when using prescribed burning. The fundamental tenet of adaptive management is to monitor management interventions and use the results to inform future actions (e.g. by halting any interventions that are found to be damaging) (Holling 1978). We propose that a ‘learning by doing’ approach should be endorsed within grouse moor management policy because it (i) allows various managements to continue as long as landowners monitor the environmental impacts of their interventions (ideally supported by scientific input at representative high-intensity monitoring sites); (ii) encourages landowners to adopt a more cautious approach to management (by realising the benefits and challenges of different options); (iii) potentially ensures more environmentally sensitive management techniques are trailed and tested (before being adopted in general); and, (iv) contributes to evidence base (in a real-world context)

Bog Breathing: The extent of peat shrinkage and expansion on blanket bogs in relation to water table, heather management and dominant vegetation and its implications for carbon stock assessments

Peatlands represent a globally important carbon stock. Peat soil carbon stock assessments rely on measurements of carbon concentration, bulk density and soil depth. However, peat surface levels - and thus soil depths - change (“bog breathing”) largely as a response to peat shrinkage and expansion in relation to water table changes. This study assessed the magnitude of and potential for this mechanism to influence carbon stock calculations under field and laboratory conditions. In the UK, most peatlands are upland blanket bogs, of which a large proportion are managed as ‘grouse moors’. This currently involves rotational burning, although alternative management is increasingly considered. Peat depth and water tables were investigated on three grouse moors on blanket bog in northern England, comparing changes under different heather management interventions (burning, mowing and uncut). One site also allowed investigation of changes in relation to slope and under the three major bog vegetation types (ling heather, cottongrass and Sphagnum moss), which were compared to observed changes in peat cores under controlled laboratory conditions simulating periods of drought and rewetting. Changes in depth and bulk density were recorded and the potential implications for carbon stock estimates were calculated. Results highlight site specific relationships as potential habitat condition indicators and demonstrate that previously reported surface peat carbon losses resulting from enhanced decomposition under rising temperatures might also be explained by apparent changes due to peat shrinkage and expansion. It is recommended to accurately record bulk density and total peat depth measurements as part of peat carbon stock assessments

Timeseries partitioning of ecosystem respiration components in seasonal, non-tropical forests; comparing literature derived coefficients with evaluation at two contrasting UK forest sites

Funding The author(s) declare financial support was received for the research, authorship, and/or publication of this article. This work was supported by UK Research and Innovation and the Biotechnology and Biological Research Council through the Strategic Priorities Fund for Greenhouse Gas Removal. NetZeroPlus: Sustainable Treescapes Demonstrator and Decision Tools (Netzeroplus.ac.uk), Grant number BB/V011588/1. The Alice Holt 2010 soil flux data were collected as part of a Natural Environment Research Council (NERC grants: F14/G6/105 & NE/C513550/1) funded project Centre for Terrestrial Carbon Dynamics. Acknowledgments The authors would like to thank Prof. Jo Smith at Aberdeen University for comments and suggestions on an early draft, and special thanks to Edward Eaton for assisting with running the Alice Holt site and contributing to the soil flux measurements. We are further grateful to the Forestry Commission, UK, for funding both the Alice Holt and Harwood long-term research sites.Peer reviewe

Exploring the “overflow tap” theory: linking forest soil CO2 fluxes and individual mycorrhizosphere components to photosynthesis

Quantifying soil organic carbon stocks (SOC) and their dynamics accurately is crucial for better predictions of climate change feedbacks within the atmosphere-vegetation soil system. However, the components, environmental responses and controls of the soil CO2 efflux (Rs) are still unclear and limited by field data availability. The objectives of this study were (1) to quantify the contribution of the various Rs components, specifically its mycorrhizal component, (2) to determine their temporal variability, and (3) to establish their environmental responses and dependence on gross primary productivity (GPP). In a temperate deciduous oak forest in south east England hourly soil and ecosystem CO2 fluxes over four years were measured using automated soil chambers and eddy covariance techniques. Mesh-bag and steel collar soil chamber treatments prevented root or both root and mycorrhizal hyphal in-growth, respectively, to allow separation of heterotrophic (Rh) and autotrophic (Ra) soil CO2 fluxes and the Ra components, roots (Rr) and mycorrhizal hyphae (Rm). Annual cumulative Rs values were very similar between years (740±43 g Cm−2 yr−1) with an average flux of 2.0±0.3 μmol CO2 m−2 s−1, but Rs components varied. On average, annual Rr, Rm and Rh fluxes contributed 38, 18 and 44 %, respectively, showing a large Ra contribution (56 %) with a considerable Rm component varying seasonally. Soil temperature largely explained the daily variation of Rs (R2 = 0.81), mostly because of strong responses by Rh (R2 = 0.65) and less so for Rr (R2 = 0.41) and Rm (R2 = 0.18). Time series analysis revealed strong daily periodicities for Rs and Rr, whilst Rm was dominated by seasonal ( 150 days), and Rh by annual periodicities. Wavelet coherence analysis revealed that Rr and Rm were related to short-term (daily) GPP changes, but for Rm there was a strong relationship with GPP over much longer (weekly to monthly) periods and notably during periods of low Rr. The need to include individual Rs components in C flux models is discussed, in particular, the need to represent the linkage between GPP and Ra components, in addition to temperature responses for each component. The potential consequences of these findings for understanding the limitations for long-term forest C sequestration are highlighted, as GPP via root-derived C including Rm seems to function as a C “overflow tap”, with implications on the turnover of SOC

Response to comment on “Peatland carbon stocks and burn history: Blanket bog peat core evidence highlights charcoal impacts on peat physical properties and long‐term carbon storage” by Evans et al.

We would like to thank the authors Evans et al. for submitting a comment on our recent publication “Peatland carbon stocks and burn history: Blanket bog peat core evidence highlights charcoal impacts on peat physical properties and long‐term carbon storage”, we especially value their direct and open approach