Search

Peatlands are a globally important wetland habitat, estimated to contain over a third of terrestrial soil carbon, placing their preservation and restoration at the forefront in debates around climate change mitigation. Anthropogenic activities, however, are driving peatland degradation loss both directly and indirectly. One such activity, is the creation of linear disturbances such as roads and tracks. The expansion of these networks, frequently in pursuit of resources, or the desire to explore remote regions, is rapidly outpacing research, with long time lags often experienced before impacts are appreciable.In 2013 an experiment was established at Moor House, an upland blanket peatland in northern England to examine the impacts of temporary plastic mesh tracks on peatland functioning. A 1.5 km long plastic mesh track was installed and split into five different treatments based on frequency of usage. The tracks were abandoned in 2015/16, and no further vehicular usage occurred. In 2020, 18 7m long sections of this track were removed, to intensively examine the ecohydrological effects of removal compared to leaving the track to overgrow. The impacts of different treatments were evaluated on the ecohydrology; removed vs abandoned track, previous usage frequency, delayed usage, and unsurfaced track. Detailed surficial structural (nanotope) assessments of the tracks were carried out, to compare ruts, centres and controls. Additionally, soil moisture measurements, overland flow sediment, peat cavity strength measurement, hydraulic conductivity, bare peat occurrence and vegetation diversity were recorded.Across all treatments alteration of the surface nanotopography was observed, loss of vegetation diversity after track removal and a reduction in vegetation height across all treatments occurred compared to controls, both on the track and along track edges. Our nanotope surveys augmented vegetation recovery assessments, demonstrating how different conclusions can be drawn, depending on whether vegetation-only or more complete assessments of surface condition are undertaken. Peat cavity strength on the tracks, measured using a peat specific penetrometer, suggests the persistence of vehicular compaction in the post abandonment and track removal periods. We also present data from overland flow sediment traps, hydraulic conductivity, and soil moisture surveys. Our findings suggest that where mesh track is to be removed, then additional revegetation interventions are required. We demonstrate that because the impacts of tracks, including mesh tracks, even after only light, short duration use, are long-lived, careful consideration of the necessity of tracks is required prior to their construction on peatland.

Temporary permissions are often granted for track use on peatlands. However, even when peatland track designs attempt to minimise environmental impacts via use of mesh systems, such linear disturbances may have persistent impacts. We evaluated the surface peatland structure of five abandoned tracks (four with a mesh surface, one unsurfaced) with varying past usage frequencies, at an upland site in northern England. Simplification of the surface nanotopography was found on all tracks compared to surrounding control areas, with increased micro-erosion patterns in rutted areas, and invasive species on some treatments. The frequency of previous usage was not found to be a significant factor controlling nano-topographic loss. Edge effects and hillslope position were influential in places, but these effects were not consistent across treatments. Nano-topographic recovery was found to be inhibited when track usage commenced within a short time frame after track construction. Mesh tracks appear to create a spatial constraint leading to poor development of plants and a reduced ability to form characteristic structures which are integral to mire function.

Prescribed burning affects plant community composition including the abundance of peat-forming Sphagnum mosses. Understanding the processes by which fire impacts occur and the variability of impacts according to fire severity is important when making fire management decisions. We monitored fire temperatures and their impact on Sphagnum capillifolium in 16 experimental fires in the field. Cell damage in response to high temperature exposure in the laboratory was also quantified for five different Sphagnum species (S. capillifolium, S. papillosum, S. magellanicum, S. austinii and S. angustifolium). Maximum temperatures recorded at the moss surface during fire ranged from 33 °C to 538 °C and were higher in plots with greater dwarf shrub cover. Higher temperatures were associated with a greater proportion of cell damage in S. capillifolium, with 93–100% cell damage observed 10 weeks after burning in the upper parts of plants exposed to temperatures over 400 °C. All five species tested in the laboratory experiment also showed more damage at higher temperatures, with damage occurring immediately after heat exposure. These results indicate that hotter fires are likely to have a greater impact on Sphagnum survival and growth, and could slow the rate at which the peatland moss layer sequesters carbon.

Fire, including prescribed burning, is common on peatlands globally and can affect vegetation, including peat-forming Sphagnum mosses, and affect ecosystem services. We monitored vegetation in different burn-age categories at three UK peatland sites over a 19-month period. Half of the plots had Sphagnum fragments added and their survival was assessed. Changes in vegetation composition over time, and associations between vegetation composition, site and burn-age category were investigated. Plots in the most recently burned category were likely to have more bare peat, a thinner moss layer and lower vascular plant strata. Graminoid cover initially increased after burning but was low after 10 + years. Dwarf shrub cover increased after burning and remained high after 10 + years. At the most Sphagnum-rich site, a high proportion of existing Sphagnum cover was bleached one year after burning, but recovery occurred during the study period. Sphagnum re-introduction success decreased over the study period in the most recent and intermediate burn-age categories at the most Sphagnum-poor site. These results show that burning rotation length is an important factor in determining site-level vegetation composition on burned sites. More frequent burning will result in a greater proportion of land in the early post-burning stages, potentially resulting in a thinner moss layer, more bare peat and less healthy Sphagnum, with potential consequences for carbon balance. No evidence was found to support the use of burning as a tool to increase existing Sphagnum or promote Sphagnum re-establishment success.

There is considerable interest in how headwater management may influence downstream flood peaks in temperate humid regions. However, there is a dearth of data on flow velocities across headwater hillslopes and limited understanding of whether surface flow velocity is influenced by seasonal changes in roughness through vegetation cycles or management. A portable hillslope flume was used to investigate overland flow velocities for four common headwater grassland habitats in northern England: Low‐density Grazing, Hay Meadow, Rank Grassland and Juncus effusus Rush pasture. Overland flow velocity was measured in replicate plots for each habitat, in response to three applied flow rates, with the experiments repeated during five different periods of the annual grassland cycle. Mean annual overland flow velocity was significantly lower for the Rank Grassland habitat (0.026 m s−1) followed by Low‐density Grazing and Rushes (0.032 and 0.029 m s−1), then Hay Meadows (0.041 m s−1), which had the greatest mean annual velocity (examples from 12 L/min flow rate). Applying our mean overland flow velocities to a theoretical 100 m hillslope suggests overland flow is delayed by >1 hr on Rank Grassland when compared to Hay Meadows in an 18 mm storm. Thus grassland management is important for slowing overland flow and delaying peak flows across upland headwaters. Surface roughness was also strongly controlled by annual cycles of vegetation growth, decay, grazing and cutting. Winter overland flow velocities were significantly higher than in summer, varying between 0.004 m s−1 (Rushes, November) and 0.034 m s−1 (Rushes, June); and velocities significantly increased after cutting varying between 0.006 m s−1 (Hay meadows, July) and 0.054 m s−1 (Hay meadows, September). These results show that seasonal vegetation change should be incorporated into flood modelling, as cycles of surface roughness in grasslands strongly modify overland flow, potentially having a large impact on downstream flood peak and timing. Our data also showed that Darcy‐Weisbach roughness approximations greatly over‐estimated measured flow velocities.

Background and aims Peatland moss communities play an important role in ecosystem function. Drivers such as fire and atmospheric pollution have the capacity to influence mosses via multiple pathways. Here, we investigate physical and chemical processes which may influence establishment and growth of three key moss species in peatlands. Methods A controlled factorial experiment investigated the effects of different peat bulk density, ash deposition and rainwater chemistry treatments on the growth of Sphagnum capillifolium, S. fallax and Campylopus introflexus. Results Higher peat bulk density limited growth of both Sphagnum species. S. capillifolium and C. introflexus responded positively to ash deposition. Less polluted rain limited growth of C. introflexus. Biomass was well correlated with percentage cover in all three species. Conclusions Peat bulk density increases caused by fire or drainage can limit Sphagnum establishment and growth, potentially threatening peatland function. Ash inputs may have direct benefits for some Sphagnum species, but are also likely to increase competition from other bryophytes and vascular plants which may offset positive effects. Rainwater pollution may similarly increase competition to Sphagnum, and could enhance positive effects of ash addition on C. introflexus growth. Finally, cover can provide a useful approximation of biomass where destructive sampling is undesirable.

Large areas of upland mire and moorland in Northwest Europe are regarded as degraded, not actively peat-forming, and releasing carbon. Conservation agencies have short-term targets to restore such areas, but often have no clear knowledge of the timing and nature of degradation. It has been suggested that palaeoecology can be used to inform conservation management about past vegetation states, so as to help identify feasible restoration targets. Our research study in northern England, commissioned by the national statutory conservation agency, applied multiple palaeoecological techniques to establish the vegetation history of several mire and moorland sites, specifically to ascertain the nature and timing of degradation. Techniques applied included pollen analysis, plant macrofossil and charcoal analyses, determination of peat humification and mineral magnetic susceptibility, with ages ascertained using spheroidal carbonaceous particle analysis, 210Pb and 14C dating. Data are presented from case-study sites in the North York Moors, North- and South Pennines to illustrate how palaeoecology can extend long-term monitoring and guide conservation management. Palaeoecological data from a site within a National Nature Reserve, subject to exceptionally long-term (half-centennial) ecological monitoring, showed that this period does not include its pre-degradation state and that its current valued vegetation is novel and may have established after major fire. Overall, the studies suggest that the principal vegetation change at the sites took place after the start of the Industrial Revolution, and that the current landscape appearance not only has no long history, but that valued aspects, such as extensive heather moorland, feature only recently in the cultural landscape. These findings pose challenging questions for conservation management. We offer a non-specialist guide to the palaeoecological techniques that considers level of skill, cost, and comparability with ecological aspects of conservation and monitoring interest. We suggest palaeoecological data can provide valuable information and insights to aid practical conservation. While mires are particularly suitable, palaeoecological techniques could be applied in many other degraded landscapes internationally.

An increasing demand for resources, coupled with technological advances which make remote exploration possible and economically viable, have led to a human push into previously inaccessible areas, including peatlands. In spite of the unsuitable nature of peat as a substrate for engineering projects there has been a growth of vehicular access networks on peatlands. However, there is a lack of understanding about how such networks impact peatland functioning. We found that research trends on peatland access track studies have changed from a concern largely with the physical properties of peat and its suitability as a substrate for building, to study of vegetation recovery, microbiological functioning and carbon cycling processes. Some recent research has examined vehicular access route impacts on peat ecohydrological processes showing that biogeochemical processes are affected, and that vegetation recovery is significantly impeded in post abandonment periods. Sizeable knowledge gaps which could form the focus of future research include the effects of roads on tropical peatlands, influence of plastic, erosion and pipe formation processes, the hydrological effects of seismic trails, ecotoxicological effects of plastic tracks and chemical pollutants on peatlands resulting from vehicular access, the ecohydrological recovery process after temporary roads are removed from peatlands.

Understanding fire impacts on peatland vegetation can inform management to support function and prevent degradation of these important ecosystems. However, time since burn, interval between burns and number of past burns all have the potential to modify impacts. Grazing regime may also affect vegetation directly or via an interaction with burning. We used new, comprehensive survey data from a hillslope-scale field experiment initiated in 1954 to investigate the effects of burning and grazing treatments on Sphagnum. Historical data were consulted to aid interpretation of the results. The unburned reference and the most frequently burned (10-year rotation) treatments had greater Sphagnum abundance and hummock height than intermediate treatments (20-year rotation and no-burn since 1954). Abundance of the most common individual species (S. capillifolium, S. subnitens and S. papillosum) followed similar patterns. Light grazing had no impact on Sphagnum-related variables, nor did it interact with the burning treatments.These results suggest that in some cases fire has a negative impact on Sphagnum, and this can persist for several decades. However, fire return interval and other factors such as atmospheric pollution may alter effects, and in some cases Sphagnum abundance may recover. Fire severity and site specific conditions may also influence effects, so we advise consideration of these factors, and caution when using fire as a management tool on peatlands where Sphagnum is considered desirable.