Prescribed Fire in UK Heather-Dominated Blanket Bog Peatlands: A Critical Review of “Carbon Storage and Sequestration by Habitat: A Review of the Evidence (Second Edition)” by Gregg et al., 2021

Abstract

Peatlands are a vast global carbon store. Both climate change and management have shaped peatlands over millennia, sometimes negatively, sometimes positively. Across the globe, prescribed fire is an important and well-recognised vegetation management tool used to promote biodiversity, increase habitat heterogeneity and mitigate uncontrolled wildfires. However, in the UK, there is an ongoing debate about the efficacy and legitimacy of using prescribed fire as a vegetation management tool. The debate centres around the extent to which prescribed burning is associated with a decline in habitat status and ecological function, especially in relation to carbon storage within heather-dominated blanket bog peatlands. Robust reviews of the evidence base are thus required to disentangle this debate and inform land management policies that ensure the protection and enhancement of blanket bog ecological functioning. Here, we critically review “Carbon storage and sequestration by habitat: a review of the evidence (second edition)” by Gregg et al., 2021. We see the value in synthesising the evidence on this topic but question the methodological approach used by Gregg et al. Another concern is their misrepresentation of evidence relating to prescribed burning impacts on blanket bog ecosystems and carbon budgets. We highlight these issues by focusing on the relevant peatland sections within the review by Gregg et al. and conclude by making a series of recommendations to improve the review’s scientific robustness and, thereby, its value to academics, land managers and policymakers.

Application of a hand-held supplementary light for extending field-based net ecosystem exchange carbon flux measurements in low light conditions

“…Chamber-based ecosystem carbon uxes are frequently used to determine the carbon balance over low vegetation, for example, in relation to vegetation cover [19], [20], [21], climate change [22] and management [23], [13]. Here we report on a practical advance in seasonal eld monitoring of manual chamber-based carbon uxes in low vegetation ecosystems, where light conditions are often limiting.…”

“…However, whilst seasonality in light response curve parameters was considered important as early as 1998[18], light (and sometimes also other environmental) response curves are often tted annually across all measured uxes [24], [25], [11], [12], [14], [15]. Such an overall annual t approach misses important seasonal differences in LCP and impacts on net carbon sink to source calculation [13] and affects the subsequent annual carbon balance, which further emphasises the need for an in-depth understanding of phenology responses to abiotic conditions associated with climatic changes [9]. However, some studies did not consider light responses at all and upscaled NEE uxes based on other environmental factors such as temperature and water table depth [26].…”

“…Moreover, unmanaged (uncut) plots were included as part of a replicated experimental block design of 5 x 5 m monitoring plots for all treatments resulting in four plots each for burnt, cut with or without brash removal and uncut plots at each site. The overall experimental and management design is fully described in two published and peer-reviewed reports [13], [16], which also provide more detailed information on site climate, soil type, hydrology and vegetation; the following section provides an overview on relevant site condition parameters for Whitendale.…”

“…Whilst eddy covariance (EC) NEE ux tower approaches are frequently used to capture a site's carbon budget, EC systems measure larger ux 'footprint' areas and cannot be easily deployed over smaller experimental treatment areas or patches of different vegetation [8]. Chamber-based measurements of NEE uxes are therefore frequently used in plot-scale studies to obtain such parameters [9], [10] for individual treatments or vegetation types to allow upscaling the manual uxes over time based on ne resolution (e.g., hourly) climatic data (e.g., temperature and light) to derive integrated carbon budgets [11], [12], [13], [14], [15], [16]. Such measurements have so far nearly always relied on natural light levels, which can be very limited, especially in upland peatlands with frequently thick cloud cover, mist or fog.…”

“…Such systems are heavy, have considerable power requirements and cause potential changes in environmental chamber conditions (e.g., temperature) with required cooling [10], which can limit its use in remote places. In this study we used the latest handheld LED ashlight technology (IMALENT SR16) to provide supplementary light during in situ chamber NEE ux measurements at a UK upland peatland site as part of an ongoing longterm study assessing climate and vegetation management impacts on heather-dominated blanket bogs [13]. Speci cally, NEE measurements were carried out on regrown areas of previously burnt or cut areas and on unmanaged, old heather areas.…”