Effects of broadleaf woodland cover on streamwater chemistry and risk assessments of streamwater acidification in acid-sensitive catchments in the UK

Acidification of surface waters has been recognised as the major water quality problem in the UK uplands. The adverse effects of conifer afforestation on streamwater chemistry and ecology are well documented in acid-sensitive catchments and have mainly been attributed to the enhanced deposition of atmospheric pollutants onto conifer canopies (the “scavenging effect”). Currently, international and national policies promote the expansion of native broadleaf woodland in the UK. Pollutant deposition onto broadleaf canopies is considered less than onto the more aerodynamically rough conifers, but there is concern that largescale broadleaf planting could delay the recovery of acidified waters or lead to further acidification in most sensitive areas. However, there has been limited investigation of the influence of broadleaf woodland cover on streamwater chemistry in the UK. To investigate the effect of woodland cover 14 catchments with different (0-78%) percentages of broadleaf woodland cover were identified in representative acidsensitive areas in north-western and central Scotland (Glen Arnisdale and Loch Katrine area) and northern and south-western England (Ullswater area and Devon) using spatial datasets in a GIS. Streamwater was sampled at high flow from the catchment outlets in winter and spring 2005 and 2006 and was analysed for major cations, anions and trace metals using standard methods. The number of samples ranged from two in the Glen Arnisdale catchments to 10 in the Loch Katrine area catchments which were sampled more intensively. Significant positive correlations were found between percentage broadleaf woodland cover and streamwater NO3 (rs = 0.51) and soluble Al (rs = 0.64) concentrations. The greater NO3 leaching to streamwater in the three most forested catchments (> 50%) was probably due to enhanced N deposition onto woodland canopies and nitrification by alder in the Ullswater area forested catchments. Streamwater NO3 concentrations equalled or exceeded non-marine SO4 in the above catchments indicating that NO3 was the principal excess acidifying ion in catchments with greater woodland cover.The woodland effect on streamwater chemistry in the study catchments was masked to some extent by variability in acid deposition climate and soil type composition. Seasalt inputs were found to be a more important control than woodland cover for streamwater chemistry in the maritime Glen Arnisdale catchments. A risk assessment of acid-sensitivity in the study catchments was conducted by calculating streamwater critical load exceedances using the Steady-State Water Chemistry (SSWC) and First-order Acidity Balance (FAB) models and modelled pollutant deposition for 1995-97 and 2002. Critical loads were exceeded by 0.01 to 1.74 keq H ha-1 yr-1 in two catchments which had woodland covers > 50% and in the Devon control catchment. The remaining 11 study catchments were assessed to be not at risk of acidification, probably due to significantly reduced non-marine S deposition from 1986 to 2001, but seasalt inputs to the Glen Arnisdale catchments might cause acidic streamwater episodes. Acid-sensitivity was also assessed using macroinvertebrates sampled in 11 of the study catchments and the results generally agreed with the critical load assessments. More detailed estimates of the enhancement of dry S and N deposition onto birchwoods in the Loch Katrine area catchments using calculated roughness length within FRAME showed that it posed no risk for streamwater acidification in these catchments because of the high rainfall environment. However, in acid-sensitive areas of the UK with lower rainfall and closer to major pollution sources, enhanced pollutant scavenging by broadleaf woodland canopies could pose a greater risk of acidification to freshwaters. The finding that almost all study catchments with woodland covers less than 30% are well protected from acidification suggests that this is a sensible threshold value for use in risk assessments of the effects of broadleaf woodland planting conducted within the Forests and Water Guidelines. The results of a sensitivity analysis of the Guidelines’ methodology, conducted using parameters such as numbers and timing of streamwater sampling, different runoff estimates and critical acid neutralising capacity values, showed that the Guidelines should be able to protect sensitive freshwaters from acidification in areas where broadleaf woodland is expanding

The riparian reactive interface: a climate-sensitive gatekeeper of global nutrient cycles

Riparian zones are critical interfaces to freshwater systems, acting as gateways for the conveyance and modification of macronutrient fluxes from land to rivers and oceans. In this paper, we propose that certain riparian conditions and processes (conceptually 'Riparian Reactive Interfaces') may be susceptible to environmental change with consequences of accelerating local nutrient cycling cascading to global impacts on the cycles of carbon (C), nitrogen (N), and phosphorus (P). However, we argue that this concept is insufficiently understood and that research has not yet established robust baseline data to predict and measure change at the key riparian ecosystem interface. We suggest one contributing factor as lack of interdisciplinary study of abiotic and biotic processes linking C, N, and P dynamics and another being emphasis on riparian ecology and restoration that limits frameworks for handling and scaling topography-soil-water-climate physical and biogeochemical observations from plot to large catchment scales. Scientific effort is required now to evaluate riparian current and future controls on global nutrient cycles through multi-nutrient (and controlling element) studies, grounded in landscape frameworks for dynamic riparian behaviour variation, facilitating scaling to catchment predictions

Eliciting expert judgements to underpin our understanding of faecal indicator organism loss from septic tank systems

Septic tank systems (STS) in rural catchments represent a potential source of microbial pollution to watercourses; however, data concerning the risk of faecal indicator organism (FIO) export from STS to surface waters are scarce. In the absence of empirical data, elicitation of expert judgements can provide an alternative approach to aid understanding of FIO pollution risk from STS. Our study employed a structured elicitation process using the Sheffield Elicitation Framework to obtain expert judgements on the proportion of FIOs likely to be delivered from STS to watercourses, based on 36 scenarios combining: (i) septic tank effluent movement risk, driven by soil hydro-morphological characteristics; (ii) distance of septic tank to watercourse; and (iii) degree of slope. Experts used the tertile method to elicit a range of values representing their beliefs of the proportion of FIOs likely to be delivered to a watercourse for each scenario. The experts judged that 93 % of FIOs would likely be delivered from an STS to a watercourse under the highest risk scenario that combined (i) very high STS effluent movement risk, (ii) STS distance to watercourse 25 %. Under the lowest risk scenario, the proportion of FIOs reaching a watercourse would likely reduce to 5 %. Expert confidence was high for scenarios that represented extremes of risk, while uncertainty increased for scenarios depicting intermediate risk conditions. The behavioural aggregation process employed to obtain a consensus among the experts proved to be useful for highlighting both areas of strong consensus and high uncertainty. The latter therefore represent priorities for future empirical research to further improve our understanding of potential pollution risk from septic tanks and in turn enable better assessments of potential threats to water quality in rural catchments throughout the world where decentralised wastewater systems are common

The riparian reactive interface: a climate-sensitive gatekeeper of global nutrient cycles

Riparian zones are critical interfaces to freshwater systems, acting as gateways for the conveyance and modification of macronutrient fluxes from land to rivers and oceans. In this paper, we propose that certain riparian conditions and processes (conceptually ‘Riparian Reactive Interfaces’) may be susceptible to environmental change with consequences of accelerating local nutrient cycling cascading to global impacts on the cycles of carbon (C), nitrogen (N), and phosphorus (P). However, we argue that this concept is insufficiently understood and that research has not yet established robust baseline data to predict and measure change at the key riparian ecosystem interface. We suggest one contributing factor as lack of interdisciplinary study of abiotic and biotic processes linking C, N, and P dynamics and another being emphasis on riparian ecology and restoration that limits frameworks for handling and scaling topography–soil–water–climate physical and biogeochemical observations from plot to large catchment scales. Scientific effort is required now to evaluate riparian current and future controls on global nutrient cycles through multi-nutrient (and controlling element) studies, grounded in landscape frameworks for dynamic riparian behaviour variation, facilitating scaling to catchment predictions.</jats:p

Globe-LFMC 2.0, an enhanced and updated dataset for live fuel moisture content research

Globe-LFMC 2.0, an updated version of Globe-LFMC, is a comprehensive dataset of over 280,000 Live Fuel Moisture Content (LFMC) measurements. These measurements were gathered through field campaigns conducted in 15 countries spanning 47 years. In contrast to its prior version, Globe-LFMC 2.0 incorporates over 120,000 additional data entries, introduces more than 800 new sampling sites, and comprises LFMC values obtained from samples collected until the calendar year 2023. Each entry within the dataset provides essential information, including date, geographical coordinates, plant species, functional type, and, where available, topographical details. Moreover, the dataset encompasses insights into the sampling and weighing procedures, as well as information about land cover type and meteorological conditions at the time and location of each sampling event. Globe-LFMC 2.0 can facilitate advanced LFMC research, supporting studies on wildfire behaviour, physiological traits, ecological dynamics, and land surface modelling, whether remote sensing-based or otherwise. This dataset represents a valuable resource for researchers exploring the diverse LFMC aspects, contributing to the broader field of environmental and ecological research

Effects of broadleaf woodland cover on streamwater chemistry and risk assessments of streamwater acidification in acid-sensitive catchments in the UK

Acidification of surface waters has been recognised as the major water quality problem in the UK uplands. The adverse effects of conifer afforestation on streamwater chemistry and ecology are well documented in acid-sensitive catchments and have mainly been attributed to the enhanced deposition of atmospheric pollutants onto conifer canopies (the “scavenging effect”). Currently, international and national policies promote the expansion of native broadleaf woodland in the UK. Pollutant deposition onto broadleaf canopies is considered less than onto the more aerodynamically rough conifers, but there is concern that largescale broadleaf planting could delay the recovery of acidified waters or lead to further acidification in most sensitive areas. However, there has been limited investigation of the influence of broadleaf woodland cover on streamwater chemistry in the UK. To investigate the effect of woodland cover 14 catchments with different (0-78%) percentages of broadleaf woodland cover were identified in representative acidsensitive areas in north-western and central Scotland (Glen Arnisdale and Loch Katrine area) and northern and south-western England (Ullswater area and Devon) using spatial datasets in a GIS. Streamwater was sampled at high flow from the catchment outlets in winter and spring 2005 and 2006 and was analysed for major cations, anions and trace metals using standard methods. The number of samples ranged from two in the Glen Arnisdale catchments to 10 in the Loch Katrine area catchments which were sampled more intensively. Significant positive correlations were found between percentage broadleaf woodland cover and streamwater NO3 (rs = 0.51) and soluble Al (rs = 0.64) concentrations. The greater NO3 leaching to streamwater in the three most forested catchments (> 50%) was probably due to enhanced N deposition onto woodland canopies and nitrification by alder in the Ullswater area forested catchments. Streamwater NO3 concentrations equalled or exceeded non-marine SO4 in the above catchments indicating that NO3 was the principal excess acidifying ion in catchments with greater woodland cover. The woodland effect on streamwater chemistry in the study catchments was masked to some extent by variability in acid deposition climate and soil type composition. Seasalt inputs were found to be a more important control than woodland cover for streamwater chemistry in the maritime Glen Arnisdale catchments. A risk assessment of acid-sensitivity in the study catchments was conducted by calculating streamwater critical load exceedances using the Steady-State Water Chemistry (SSWC) and First-order Acidity Balance (FAB) models and modelled pollutant deposition for 1995-97 and 2002. Critical loads were exceeded by 0.01 to 1.74 keq H ha-1 yr-1 in two catchments which had woodland covers > 50% and in the Devon control catchment. The remaining 11 study catchments were assessed to be not at risk of acidification, probably due to significantly reduced non-marine S deposition from 1986 to 2001, but seasalt inputs to the Glen Arnisdale catchments might cause acidic streamwater episodes. Acid-sensitivity was also assessed using macroinvertebrates sampled in 11 of the study catchments and the results generally agreed with the critical load assessments. More detailed estimates of the enhancement of dry S and N deposition onto birchwoods in the Loch Katrine area catchments using calculated roughness length within FRAME showed that it posed no risk for streamwater acidification in these catchments because of the high rainfall environment. However, in acid-sensitive areas of the UK with lower rainfall and closer to major pollution sources, enhanced pollutant scavenging by broadleaf woodland canopies could pose a greater risk of acidification to freshwaters. The finding that almost all study catchments with woodland covers less than 30% are well protected from acidification suggests that this is a sensible threshold value for use in risk assessments of the effects of broadleaf woodland planting conducted within the Forests and Water Guidelines. The results of a sensitivity analysis of the Guidelines’ methodology, conducted using parameters such as numbers and timing of streamwater sampling, different runoff estimates and critical acid neutralising capacity values, showed that the Guidelines should be able to protect sensitive freshwaters from acidification in areas where broadleaf woodland is expanding.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Protection of Peatlands and Wetlands – a potential new GAEC measure for Scotland:An output to RESAS as part of commissioned project on Economic Advice &amp; Related Services to Support Development of a New Rural Support Scheme for Scotland Output Ref: RESAS/005/21 – W10

The Scottish Government are committed to enhanced conditionality for future agricultural support. As part of the transition to future agricultural support schemes there is an opportunity to help transition towards future schemes by introducing additional conditions (cross compliance) through existing support schemes in 2025. The protection and enhancement of Scottish wetlands and peatlands offers potentially significant emission reductions and biodiversity improvements. The focus on peatland and wetland emissions has increased since national inventory methodology changes to the LULUCF to account for wetlands and peatlands moved LULUCF from a net sink of 5.4Mt CO2e to a net source of 2.7MtCO2e. A combination of actions across the proposed 4-Tier policy model could be used to seek protection and enhancement of peatlands, possibly in terms of Bronze/ Silver/Gold standards as suggested by ARE officials to ARIOB. In particular, Tier 1 cross compliance and Tier 2 conditionalities offer opportunities to enrol a high proportion of relevant land. This reflects the fact that wetlands and peatlands are widely distributed across Scotland, albeit particularly prevalent in the existing Region 3 of the Basic Payment Scheme.Tier 1 conditionality could take the form of restrictions on cultivation, drainage installation, stocking density, tree planting, conversion of permanent pasture on peatland to cropland, etc could be included. This would mirror inclusion of ‘Protection of wetlands and peatland’ within the new Good Agricultural and Environmental Condition (GAEC2) applied under the Common Agricultural Policy, thereby helping to maintain alignment with EU regulations. Tier 2 enhanced conditionality could then include blocking of hill drains, reduced stocking density, moorland management plans, restrictions on cultivations on peatlands used for cropping. Tiers 3 and 4 could then include support for more capital-intensive restoration actions (e.g., revegetating bare peat) and more demanding on-going management (e.g., intermittent scrub clearance, more radical stock reductions). In common with other specific policy objectives, the boundaries between different Tiers are not necessarily fixed, meaning that particular measures may switch Tiers over time. Consideration of effects and potential consequences of any Tier 1 cross compliance or Tier 2 conditionality on common grazing peatland / wetlands would need careful consideration, since individual crofters may not have the capacity or abilities to manage common grazing peatland areas.<br/