Long‐term effects of rotational prescribed burning and low‐intensity sheep grazing on blanket‐bog plant communities

Abstract

Summary1. The importance of peatlands is being increasingly recognized internationally for both the conservation of biodiversity and the provision of ecosystem services; strategies are being developed world-wide to help maintain their integrity. Prescribed burning has been highlighted as a threat with considerable debate over its use as it is perceived to produce a Calluna vulgaris monoculture and a decline in preferred peat-forming species. 2. We investigated the impact of prescribed burning on vegetation composition and diversity in a long-term experiment at Moor House NNR in northern England. The study comprised a comparison between no-burn reference plots last burned in ca. 1924 and an experiment where all plots were burned in 1954/5. Within the experiment, the effects of very light sheep grazing vs. no grazing and three burning rotations (no-burn since 1954/5, repeat-burning at 10-and 20-year intervals) were tested. 3. Calluna vulgaris and Hypnum jutlandicum cover and bryophyte species richness increased in the least-disturbed, no-burn reference plots, but bryophyte cover did not. Lichen diversity declined. 4. Within the formal experiment, low-intensity sheep grazing had little impact but there were substantive changes produced by the different burning rotations. There was divergence between the burning rotation treatments with the least-disturbed, no-burn treatment changing towards a C. vulgaris-H. jutlandicum community, whereas the most-disturbed 10-year rotation had a much greater abundance of both Eriophorum and Sphagnum spp. 5. Synthesis and applications. Our findings suggest that blanket-bog vegetation on peat responds to prescribed burning in a complex manner. Where burn return interval is long (>20 years), C. vulgaris becomes dominant and there was no evidence that preferred peatforming species (Eriophorum/Sphagnum) increased. Where burn return interval is short (10 years), E. vaginatum/Sphagnum abundance increased. We found no evidence to suggest that prescribed burning was deleterious to the abundance of peat-forming species; indeed, it was found to favour them. These results inform conservation management policy for blanket bogs in the UK and more generally for future wildfire-mitigation strategies on dwarf-shrubdominated peatlands elsewhere. Some lessons for the management of long-term experimental studies are also discussed.

Late Holocene regime shifts in moorland ecosystems: high resolution data from the Pennines, UK

“…In particular, there is a lack of data on the dynamics of non-eroding communities during recent centuries, when severe impacts have emerged. This creates uncertainty about the extent of moorland turnover (Dallimer et al 2009) and the role of burning in sustainable management (Lee et al 2013). Extrapolating across heterogeneous upland terrain may underestimate the extent of past spatial heterogeneity and temporal variability (Davies and Tipping 2004;Fyfe and Woodbridge 2012), so high spatial-resolution pollen analyses from different peatland habitats can usefully be employed to address these issues.…”

Sphagnum abundance and photosynthetic capacity show rapid short-term recovery following managed burning

“…Although differences in Sphagnum cover between burnt and unburnt plots were not significant, the slight but consistently higher cover values following burning suggest that Sphagnum abundance (Tables S2 and S3), weather information (Table S4) and F v /F m vs. time since fire for individual samples ( Figure S1). could increase in the longer term as a result of the removal of the Calluna canopy and increases in competitive ability relative to pleurocarpous mosses (Benscoter and Vitt 2008;Lee et al 2013). This hypothesis is supported by studies on a blanket bog in northern England which have previously found higher Sphagnum abundance at smaller times since fire (Burch 2009), and at short (10-year) vs. longer (20-year) burning rotations or unburnt (47 years) conditions (Lee et al 2013).…”

“…could increase in the longer term as a result of the removal of the Calluna canopy and increases in competitive ability relative to pleurocarpous mosses (Benscoter and Vitt 2008;Lee et al 2013). This hypothesis is supported by studies on a blanket bog in northern England which have previously found higher Sphagnum abundance at smaller times since fire (Burch 2009), and at short (10-year) vs. longer (20-year) burning rotations or unburnt (47 years) conditions (Lee et al 2013). Fire-induced heating greatly reduced S. capillifolium photosynthetic capacity as measured at ca.…”

“…We do however have a number of studies which suggest that certain Sphagnum species are resilient to the effects of fire. For instance, previous field research on the North York Moors (northern England) reported greater Sphagnum abundance in plots with a 10-year managed burning rotation compared to plots that had remained unburnt for 47 years (Lee et al 2013), whilst other studies of managed burning have shown greater abundance in more recently burnt areas (3-7 years) compared to areas unburnt for 25 years (Burch 2009). In peatlands in Alberta (Canada), Sphagnum abundance was highest at medium time spans postwildfire (20-80 years) compared to shorter (10 years) or longer time spans (>80 years) (Benscoter and Vitt 2008).…”

Using palaeoecology to advise peatland conservation: An example from West Arkengarthdale, Yorkshire, UK

“…BP) towards the surface. The increase in charcoal is indicative of burning, which has increased in the last few hundred years with the introduction of rotational burning for the management of grouse (Lee et al, 2013). Grazing of sheep has also taken place at the site, which is also known to encourage the growth of grasses (Wilson, Wilson, & Johnstone, 2011).…”