The multi-annual carbon budget of a peat-covered catchment.

This study estimates the complete carbon budget of an 11.4 km(2) peat-covered catchment in Northern England. The budget considers both fluvial and gaseous carbon fluxes and includes estimates of particulate organic carbon (POC); dissolved organic carbon (DOC); excess dissolved CO(2); release of methane (CH(4)); net ecosystem respiration of CO(2); and uptake of CO(2) by primary productivity. All components except CH(4) were measured directly in the catchment and annual carbon budgets were calculated for the catchment between 1993 and 2005 using both extrapolation and interpolation methods. The study shows that: Over the 13 year study period the total carbon balance varied between a net sink of -20 to -91 Mg C/km(2)/yr. The biggest component of this budget is the uptake of carbon by primary productivity (-178 Mg C/km(2)/yr) and in most years the second largest component is the loss of DOC from the peat profile (+39 Mg C/km(2)/yr). Direct exchanges of C with the atmosphere average -89 Mg C/km(2)/yr in the catchment. Extrapolating the general findings of the carbon budget across all UK peatlands results in an approximate carbon balance of -1.2 Tg C/yr (+/-0.4 Pg C/yr) which is larger than previously reported values. Carbon budgets should always be reported with a clear statement of the techniques used and errors involved as this is significant when comparing results across studies.

Spatial variation in concentrations of dissolved nitrogen species in an upland blanket peat catchment.

The concentration of nitrogen (N), particularly as nitrate (NO3-N), in upland streams, lakes and rivers is frequently used as a diagnostic of the vulnerability of upland ecosystems to increased atmospheric nitrogen deposition and N saturation. The N content of running waters, however, is generally assessed on the basis of sampling at a limited number of points in space and time within the catchment under investigation. The current study was conducted at Trout Beck, an 11.5 km2 blanket peat-dominated catchment in the North Pennine uplands of the UK. Results from sampling at 33 sites within this catchment demonstrated that the concentrations of all dissolved N species were highly variable, even over short distances. Statistical relationships between the concentrations of NO3-N and dissolved organic nitrogen (DON) and percentage catchment cover of Calluna/Eriophorum and Eriophorum vegetation were found. However, it was also noted that in catchments containing limestone outcrops, NO3-N concentration was much higher than in catchments where runoff was sourced directly from the blanket peat surface. It is possible that NH4-N and DON leached from the blanket peat are mineralised and nitrified, providing a source for the NO3-N found in the river channels. Overall, the current study suggests that interpretations of N-saturation based on river water chemistry measurements at a single point must be treated cautiously, and that the influence of catchment-scale physical factors, such as vegetation and geology cover on the concentration of dissolved N species in upland river waters should not be ignored.

Monitoring of aquatic macrophytes for detection of long-term change in river systems.

This paper presents details of the methodology developed by the United Kingdom's Environmental Change Network for the long-term monitoring of macrophytes in rivers and streams. The methodology is based on techniques first proposed by the Standing Committee of Analysts (1987) and later adapted by the National Rivers Authority (NRA) and Environment Agency, but differs in splitting the surveyed 100 m stretch of water into sections to provide an objective measure of the frequency of occurrence of individual species in place of the more subjective estimation of cover. A pilot study of the ECN methodology took place at five sites in 1997. The results of this study, including a few practical difficulties in the application of the methodology, are presented and discussed. For all but one of the sites strong associations were found between the number of species observed and the physical characteristics of the watercourse. The most important characteristics were degree of shading, substrate type, depth and clarity. The frequency of occurrence of individual species within sections of the watercourse was found to be strongly related to the log of the overall estimates of cover. Because the use of sections, rather than a single overall cover estimate, enables variation in the pattern of vegetation over surveyed stretches to be detected and related to watercourse characteristics, the precision with which change can be detected is increased, and the possibility of determining the causes of change is thereby enhanced. Moreover the use of sections allows within-site variation to be calculated and hence the accuracy of estimated changes to be quantified. In general implementation of the ECN methodology was not found to be particularly onerous or difficult. As a result of the pilot study some changes in the ECN methodology have been made, primarily to reduce the workload so that sites can be surveyed comfortably in a single day.

Trends in stream water quality in Environmental Change Network upland catchments: the first 5 years.

Hydrochemical data from catchment streams at three Environmental Change Network (ECN) upland catchments in north-east Scotland, south-east Scotland and northern England have been subjected to statistical analysis to separate the components due to long-term trend, season and flow. The relative variances due to each are presented for pH, Ca, SO4-S, NO3-N, DOC and Cl. Long-term trends have been identified with increases in concentration for NO3-N and DOC, decreases in SO4-S concentrations, along with short-term seasonal fluctuations. Application of this trend technique has allowed the detection of changes and contributed to an improved understanding of catchment behaviour.

The dynamics of dissolved nitrogen in a blanket peat dominated catchment.

Precipitation, soil solution and drainage water were collected from a blanket peat catchment at Moor House National Nature Reserve in the Northern Pennine Uplands, UK, an area of moderately high N deposition. Two tributaries of the main stream were also sampled. Between 1993 and 1995 samples were analysed for NH4+ and NO3- and for part of the period for organic N. Inputs of N in precipitation exceeded outputs in stream water. Organic N represented a small proportion of N inputs while inputs of inorganic N averaged 10.2 kg ha(-1) a(-1). Soil solution from 10 cm depth in the peat was dominated by organic N whereas at 50 cm NH4+ slightly exceeded organic N. NO3- was rarely detected at either depth except during a period of exceptionally warm and dry weather in 1995. Output fluxes in stream water of organic N (5.7 to 6.5 kg ha(-1) a(-1)) were much greater than those of inorganic N (0.6 to 2.2 kg ha(-1) a(-1)). Inorganic N in streams was predominantly NO3- except in the smallest stream which had the largest concentrations of NH4+. This suggests that N transformations, particularly nitrification, may be taking place in the mineral soils adjacent to the streams or within the stream channel of the larger catchment.

Effects of clearfelling on stream and soil water aluminium chemistry in three UK forests.

Data are presented demonstrating how clearfelling has changed soil and stream water aluminium chemistry. For soil waters, a strong empirical relationship was observed between inorganic aluminium (Al(inorg)) and total inorganic anion (TIA) concentrations. Before felling, chloride and sulphate accounted for the largest proportion of the TIA concentration. After felling, in soils where nitrification was active, nitrate became increasingly important. Where this led to an increase in TIA, Al(inorg) concentrations increased. Over five years, nitrate concentrations have fallen, along with TIA, resulting in a sympathetic decline in Al(inorg). Streams draining clearfelled areas initially became more acid, although chloride and sulphate concentrations decreased. Stream water nitrate concentrations increased soon after felling and remained higher than controls for up to four years. While nitrate concentrations were high, Al(inorg) remained unchanged. Subsequently, as nitrate and TIA decreased, Al(inorg) also declined to concentrations below those in the control stream. Clearfelling upland forests will not necessarily result in immediate improvements in water quality, although long-term benefits may be seen before canopy-closure of the next crop.