Catchment water quality in the year preceding and immediately following restoration of a drained afforested blanket bog

Abstract

The restoration of drained afforested peatlands, through drain blocking and tree removal, is increasing in response to peatland restoration targets and policy incentives. In the short term, these intensive restoration operations may affect receiving watercourses and the biota that depend upon them. This study assessed the immediate effect of ‘forest-to-bog’ restoration by measuring stream and river water quality for a 15 month period pre- and post-restoration, in the Flow Country peatlands of northern Scotland. We found that the chemistry of streams draining restoration areas differed from that of control streams following restoration, with phosphate concentrations significantly higher (1.7–6.2 fold, mean 4.4) in restoration streams compared to the pre-restoration period. This led to a decrease in the pass rate (from 100 to 75%) for the target “good” quality threshold (based on EU Water Framework Directive guidelines) in rivers in this immediate post-restoration period, when compared to unaffected river baseline sites (which fell from 100 to 90% post-restoration). While overall increases in turbidity, dissolved organic carbon, iron, potassium and manganese were not significant post-restoration, they exhibited an exaggerated seasonal cycle, peaking in summer months in restoration streams. We attribute these relatively limited, minor short-term impacts to the fact that relatively small percentages of the catchment area (3–23%), in our study catchments were felled, and that drain blocking and silt traps, put in place as part of restoration management, were likely effective in mitigating negative effects. Looking ahead, we suggest that future research should investigate longer term water quality effects and compare different ways of potentially controlling nutrient release.

Peatland pools are tightly coupled to the contemporary carbon cycle

“…Ditch blocking often results in the establishment of pools behind small dams (Chapman et al., 2022; Holden et al., 2018). These “restoration” pools may retain C that would otherwise be directly lost from peatlands via runoff into drainage ditches (Gaffney et al., 2021; Parry et al., 2014). It is therefore important to know whether pools formed through restoration efforts are receiving and emitting old C destabilized by legacy drainage, in addition to the contemporary C turnover expected under raised water table conditions (Evans et al., 2021; Parry et al., 2014; Waldron et al., 2019).…”

Optimising production of a biochar made from conifer brash and investigation of its potential for phosphate and ammonia removal

“…This practice emerged in blanket bog peatlands, following increased awareness of the negative impacts of drainage and conifer plantations on blanket bog vegetation, breeding waders, peatland carbon stocks and surface water quality (Anderson et al, 2016;Wilson et al, 2014). While restoration of drained afforested blanket bogs (termed 'forest-to-bog' restoration) can re-instate key ecosystem services over a long time frame, i.e., after around 20 years post-felling (Gaffney et al, 2018;Hambley et al, 2019;Hancock et al, 2018), certain short term (potentially negative) effects of restoration can occur related to peatland ecohydrology and biogeochemical processes (Gaffney et al, 2021(Gaffney et al, , 2018. One of these effects is altered pore-and surface-water chemistry following restoration, attributed (in part) to decomposition of brashthe treetops and branches which can remain on site and decompose post-restoration; and, the rewetting of previously aerobic peat (Gaffney et al, 2021(Gaffney et al, , 2018Shah and Nisbet, 2019).…”

“…While restoration of drained afforested blanket bogs (termed 'forest-to-bog' restoration) can re-instate key ecosystem services over a long time frame, i.e., after around 20 years post-felling (Gaffney et al, 2018;Hambley et al, 2019;Hancock et al, 2018), certain short term (potentially negative) effects of restoration can occur related to peatland ecohydrology and biogeochemical processes (Gaffney et al, 2021(Gaffney et al, , 2018. One of these effects is altered pore-and surface-water chemistry following restoration, attributed (in part) to decomposition of brashthe treetops and branches which can remain on site and decompose post-restoration; and, the rewetting of previously aerobic peat (Gaffney et al, 2021(Gaffney et al, , 2018Shah and Nisbet, 2019). The main water chemistry changes associated with restoration are commonly increased concentrations of nutrients (ammonium-nitrogen; NH 4 + -N and phosphate; PO 4 3− -P) in run-off, which may be detected locally in streams and may also reach main rivers, depending on the proportion of the catchment undergoing restoration.…”

Aquatic carbon concentrations and fluxes in a degraded blanket peatland with piping and pipe outlet blocking

“…Recent research into blanket peatland degradation has examined landform structure (Chico et al, 2020), hydrological function (Holden et al, 2011), processes controlling gully erosion (Evans & Lindsay, 2010), the production, loss and fate of particulate organic carbon (POC) and dissolved organic carbon (DOC) in runoff (Li et al, 2019;Palmer et al, 2016;Pawson et al, 2012), and metal and nutrient pollution of watercourses (Gaffney et al, 2021;Rothwell et al, 2005). Recent work has also examined the impacts of restoration action such as exclusion of grazing (Valdeolivas et al, 2018), revegetation (González & Rochefort, 2018), ditch blocking, gully blocking and re-vegetation on runoff production (Shuttleworth et al, 2019), and DOC and POC concentrations and fluxes in stream water (Evans et al, 2016;Peacock et al, 2018;Renou-Wilson et al, 2019;Shuttleworth et al, 2015).…”