Elevated nutrient concentrations in headwaters affected by drained peatland

Abstract

Nutrient export from drained peatland has significant impacts on aquatic environments in Nordic catchments. Spatial information on variations in nutrient concentrations across different landscapes and land uses is needed to design measures for achieving the good ecological status of the EU Water Framework Directive. In this study we determined background concentrations in natural peatland-dominated streams and examined effects of peatland use practices on water quality in headwater catchments. We quantified sources for different elements by joint analysis of water chemistry, isotopes, and hydrology for 62 small catchments in North Ostrobothnia, Finland. Concentrations of nutrients and suspended solids were relatively high in catchments containing drained peatland. In particular, dissolved nitrogen and phosphorus concentrations were elevated during baseflow conditions when flow likely originated from deeper soil layers. Total concentrations of nutrients, suspended solids, and loss on ignition also showed elevated values, and changes in the ratio of dissolved and particulate forms, especially the C/N ratio, were observed. Past drainage had a stronger effect on organic matter and nutrients concentrations than local hydroclimate conditions. These results strongly indicate that current water protection methods are not sufficient to capture all seasonal variations in nutrient and suspended solid loads from drained peatland. Thus, more effort and actions are needed for water protection in such areas.

Browning of freshwaters: Consequences to ecosystem services, underlying drivers, and potential mitigation measures

“…Extensive peatland areas throughout Fennoscandia have been drained, in more or less systematic ways, with the purpose to improve forest production (Päivänen and Hånell 2012;Sikström and Hökkä 2016). Area drained for peatland forestry has been positively correlated with TOC and DOC (Marttila et al 2018) and drained peatland forests have been shown to be significantly greater sources of DOC to receiving waters than undrained peatlands and upland forest soils (Rantakari et al 2010). Päivänen and Hånell (2012) suggested that in drained peatlands, aeration promotes microbial processes and solubility, and thereby increases peat mineralization, resulting in the increasing DOC concentration.…”

“…Päivänen and Hånell (2012) suggested that in drained peatlands, aeration promotes microbial processes and solubility, and thereby increases peat mineralization, resulting in the increasing DOC concentration. This increase in peat decomposition level due to drainage, combined with naturally fluctuating water tables, creates a condition with increased loads of DOC and nutrients from drained peatlands (Marttila et al 2018;Nieminen et al 2018).…”

Controls of Organic Carbon and Nutrient Export from Unmanaged and Managed Boreal Forested Catchments

“…However, a recent study [21] suggested that N and P concentrations in runoff from old drained peatlands may slowly increase as a function of time. Drainage causes also long-term changes in the quality of organic matter in runoff [22]. There is a clear knowledge gap between the controlled paired catchment studies and monitoring studies concerning response of water quality to long-term effects of drainage and low intensity harvesting such as thinning, small area clear-cutting and partial harvesting.…”

Land‐use dominates climate controls on nitrogen and phosphorus export from managed and natural Nordic headwater catchments

“…Local increases of nitrogen and phosphorus concentrations in forestry‐impacted catchments is well‐documented (De Wit et al, 2014; Lofgren, Ring, von Bromssen, Sorensen, & Hogbom, 2009) but its impact on a wider temporal and spatial scale is less clear (Sponseller et al, 2016). In areas with intensive peatland forestry like Finland, harvesting operations in forest on organic soils are of specific concern (Marttila et al, 2018; Nieminen et al, 2018). Furthermore, intensified forestry by conducting whole tree harvesting may require application of a fertilizer to avoid reduced forest growth (Akselsson, Westling, Sverdrup, & Gundersen, 2007; Merila et al, 2014).…”