bluuebunny/crossref_metadata_2025 huggingface dataset:
Coherent responses of sulphate concentration in Norwegian lakes: relationships with sulphur deposition and climate indices
Authors: Dillon P. J. , Skjelkvåle B. L. , Somers K. M. , Tørseth K.
Published: April 2010

Abstract. The coherence or synchrony in the trends in SO42– concentration in a set of 100 lakes in Norway that have a long-term chemical record was evaluated. Using a statistical technique that compares patterns or trends that are not uni-directional, the lakes were grouped into 18 subsets or clusters, each with between 2 and 11 lakes that had similar trends. These temporal trends were strongly correlated with several climate indices, notably the Arctic Oscillation Index (AOI) measured in the autumn, and the annual North Atlantic Oscillation Index (NAOI). Because these clusters of lakes were spatially dispersed, they could not be compared directly with trends in wet S deposition, because S deposition varied substantially between lakes within each cluster. However, the average trend in SO42– concentration was evaluated in each of 10 regions of Norway that were defined previously on the basis of pollution load, meteorological variables and biogeography. Although these regions did not match the statistically-selected clusters of lakes with equal trends very closely, there were similar, strong correlations between climate indices (the AOI and NAOI) and the 10 average SO42– trends, although there were even stronger relationships with average wet S deposition in the regions. When subsets of lakes with coherent SO42– trends were selected from within each of the 10 regions, both wet S deposition and the climate indices were strongly correlated with those SO42– trends. Hence, lakes in Norway respond to changes in wet S deposition and are influenced by large-scale, i.e. global, climate signals. Future evaluation of recovery of lakes affected by acid deposition must therefore consider the confounding effects of climate and potential climate change. Keywords: recovery, acid deposition, coherence, sulphate, climate change
Assessing emission reduction targets with dynamic models: deriving target load functions for use in integrated assessment
Authors: Jenkins A. , Cosby B. J. , Ferrier R. C. , Larssen T. , Posch M.
Published: April 2010

Abstract. International agreements to reduce the emission of acidifying sulphur (S) and nitrogen (N) compounds have been negotiated on the basis of an understanding of the link between acidification related changes in soil and surface water chemistry and terrestrial and aquatic biota. The quantification of this link is incorporated within the concept of critical loads. Critical loads are calculated using steady state models and give no indication of the time within which acidified ecosystems might be expected to recover. Dynamic models provide an opportunity to assess the timescale of recovery and can go further to provide outputs which can be used in future emission reduction strategies. In this respect, the Target Load Function (TLF) is proposed as a means of assessing the deposition load necessary to restore a damaged ecosystem to some pre-defined acceptable state by a certain time in the future. A target load represents the deposition of S and N in a defined year (implementation year) for which the critical limit is achieved in a defined time (target year). A TLF is constructed using an appropriate dynamic model to determine the value of a chemical criterion at a given point in time given a temporal pattern of S and N deposition loads. A TLF requires information regarding: (i) the chemical criterion required to protect the chosen biological receptor (i.e. the critical limit); (ii) the year in which the critical limit is required to be achieved; and (iii) time pattern of future emission reductions. In addition, the TLF can be assessed for whole regions to incorporate the effect of these three essentially ecosystem management decisions. Keywords: emission reduction, critical load, target load, dynamic model, recovery time
Estimating rainfall distributions at high temporal resolutions using a multifractal model
Authors: Pathirana A. , Herath S. , Yamada T.
Published: April 2010

Abstract. Rainfall data from 18 stations in the vicinity of Tokyo city, measured to a precision of 1 mm, were analysed for multifractal properties. A multifractal model based on the scaling properties of temporal distribution of rainfall intensities was formulated to investigate the intensity distribution relationships in the available scaling regime. Although conventional analysis did not provide encouraging results with these measurements, an alternative approach that could be applied to rainfall data of widely variable quality and duration was used to establish a scaling relationship between daily and hourly rainfall intensities. Using a discrete cascade algorithm based on the log-Lèvy generator, synthetic hourly rainfall series were generated from the multifractal statistics of daily-accumulated rainfall. Several properties of rainfall time series that are relevant to the use of rainfall data in surface hydrological studies were used to determine, statistically, the degree of agreement between the synthetic hourly series and observed hourly rainfall. Keywords: rainfall modelling, cascades, multifractal, downscaling
Dynamical properties of the spatial distribution of snow
Authors: Skaugen T. , Beldring S. , Udnæs H.-C.
Published: April 2010

Abstract. A simulation exercise has been performed to study the temporal development of snow covered area and the spatial distribution of snow-water equivalent (SWE). Special consideration has been paid to how the properties of the spatial statistical distribution of SWE change as a response to accumulation and ablation events. A distributed rainfall-runoff model at resolution 1 x 1 km2 has been run with time series of precipitation and temperature fields of the same spatial resolution derived from the atmospheric model HIRLAM. The precipitation fields are disaggregated and the temperature fields are interpolated. Time series of the spatial distribution of snow-water equivalent and snow-covered area for three seasons for a catchment in Norway is generated. The catchment is of size 3085 km2 and two rectangular sub-areas of 484 km2 are located within the larger catchment. The results show that the shape of the spatial distribution of SWE for all three areas changes during winter. The distribution is very skewed at the start of the accumulation season but then the skew decreases and, as the ablation season sets in, the spatial distribution again becomes more skewed with a maximum near the end of the ablation season. For one of the sub-areas, a consistently more skewed distribution of SWE is found, related to higher variability in precipitation. This indicates that observed differences in the spatial distribution of snow between alpine and forested areas can result from differences in the spatial variability of precipitation. The results obtained from the simulation exercise are consistent with modelling the spatial distribution of SWE as summations of a gamma distributed variable. Keywords: Snow, SWE, spatial distribution, simulated hydrometeorological fields
Intercomparison of mesoscale meteorological models for precipitation forecasting
Authors: Richard E. , Cosma S. , Benoit R. , Binder P. , Buzzi A. , Kaufmann P.
Published: April 2010

Abstract. In the framework of the RAPHAEL EU project, a series of past heavy precipitation events has been simulated with different meteorological models. Rainfall hindcasts and forecasts have been produced by four models in use at various meteorological services or research centres of Italy, Canada, France and Switzerland. The paper is focused on the comparison of the computed precipitation fields with the available surface observations. The comparison is carried out for three meteorological situations which lead to severe flashflood over the Toce-Ticino catchment in Italy (6599 km2) or the Ammer catchment (709 km2) in Germany. The results show that all four models reproduced the occurrence of these heavy precipitation events. The accuracy of the computed precipitation appears to be more case-dependent than model-dependent. The sensitivity of the computed rainfall to the boundary conditions (hindcast v. forecast) was found to be rather weak, indicating that a flood forecasting system based upon a numerical meteo-hydrological simulation could be feasible in an operational context. Keywords: meteorological models, precipitation forecast
Simulation of soil moisture and evapotranspiration in a soil profile during the 1999 MAP-Riviera Campaign
Authors: Zappa M. , Gurtz J.
Published: April 2010

Abstract. Detailed plot-scale observations of basic hydrometeorological variables represent valuable data for assessing the quality of the soil moisture module and evapotranspiration scheme in hydrological models. This study presents the validation of soil moisture and evapotranspiration (ET) simulation during the special observing period (R-SOP) of the Riviera Project (July–November 1999), a sub-project of the Mesoscale Alpine Programme (MAP). The location investigated was a sandy soil plot at the edge of a corn field. The hydrological model PREVAH was driven using three meteorological data sets: hourly data from an experimental tower in the Riviera Valley (southern Switzerland), hourly data interpolated for the Riviera site during the R-SOP period from permanent automatic stations (MeteoSwiss network) and interpolated daily data (1980–2000). The quality of the interpolated meteorological data was evaluated with respect to data collected at an experimental tower. The interpolated data proved fairly representative for the location under investigation. The hydrological simulations were compared with recorded observations of soil moisture and latent heat flux (LE). The simulation of soil moisture was accurate in case of all three meteorological data sets. The results of ET simulations with three simple parameterisations showed high correlation to LE derived using the Bowen ratio and measured through eddy correlation. The quantitative agreement between observed and simulated LE was poorer because of the presence of a fully developed wind valley system during periods of good weather. This wind system claims part of the available energy and therefore reduces the amount of energy available for LE. The 21-year simulation at daily time step shows that the R-SOP period in 1999 was warm and wet compared to the last 21 years. Keywords: MAP-Riviera Project, soil moisture, evapotranspiration, hydrological modelling, model evaluation
TECHNICAL NOTE: The representation of rainfall drop-size distribution and kinetic energy
Authors: Fox N. I.
Published: April 2010

Abstract. To relate observed rainfall rates (R) to the kinetic energy flux (E) that affects soil erosion it is necessary to develop relationships between the two. This paper explores theoretical E–R relationships based on gamma distributions of drop size. The relationship is poorly defined unless assumptions are made about changes in the shape of the drop-size distribution (DSD) with rainfall rate. The study suggests that the assumption of an exponential DSD leads to overestimation of kinetic energy flux. Further, incorporation of a horizontal component of kinetic energy allows for a clearer relationship between kinetic energy and rainfall intensity to be defined, but a question remains regarding the most appropriate definition of the horizontal component of drop velocity. Keywords: drop-size distribution, drop kinetic energy, soil erosion
Impact analysis of climate change for an Alpine catchment using high resolution dynamic downscaling of ECHAM4 time slices
Authors: Kunstmann H. , Schneider K. , Forkel R. , Knoche R.
Published: April 2010

Abstract. Global climate change affects spatial and temporal patterns of precipitation and so has a major impact on surface and subsurface water balances. While global climate models are designed to describe climate change on global or continental scales, their resolution is too coarse for them to be suitable for describing regional climate change. Therefore, regional climate models are applied to downscale the coarse meteorological fields to a much higher spatial resolution to take account of regional climate phenomena. The changes of atmospheric state due to regional climate change must be translated into surface and sub-surface water fluxes so that the impact on water balances in specific catchments can be investigated. This can be achieved by the coupled regional climatic/hydrological simulations presented here. The non-hydrostatic regional climate model MCCM was used for dynamic downscaling for two time slices of a global climate model simulation with the GCM ECHAM4 (IPCC scenario IS92a, "business as usual") from 2.8° × 2.8° to 4 × 4 km2 resolution for the years 1991–1999 and 2031–2039. This allowed derivation of detailed maps showing changes in precipitation and temperature in a region of southern Germany and the central Alps. The performance of the downscaled ECHAM4 to reproduce the seasonality of precipitation in central Europe for the recent climate was investigated by comparison with dynamically downscaled ECMWF reanalyses in 20 × 20 km2 resolution. The downscaled ECHAM4 fields underestimate precipitation significantly in summer. The ratio of mean monthly downscaled ECHAM4 and ECMWF precipitation showed little variation, so it was used to adjust the course of precipitation for the ECHAM4/MCCM fields before it was applied in the hydrological model. The high resolution meteorological fields were aggregated to 8-hour time steps and applied to the distributed hydrological model WaSiM to simulate the water balance of the alpine catchment of the river Ammer (c. 700 km2) at 100 × 100 m2 resolution. To check the reliability of the coupled regional climatic/hydrological simulation results for the recent climate, they were compared with those of a station-based hydrological simulation for the period 1991–1999. This study shows the changes in the temperature and precipitation distributions in the catchment from the recent climate to the future climate scenario and how these will affect the frequency distribution of runoff. Keywords: coupled climate-hydrology simulations, dynamic downscaling, distributed hydrological modelling, ECHAM4 climate scenario, alpine hydrology
Statistical representation of mountain shading
Authors: Essery R.
Published: April 2010

Abstract. Shadows cast by the mountains themselves have a strong influence on the surface energy balance of mountainous regions. If the influence of shadows is to be included on sub-grid scales in a surface energy balance model, a statistical representation has to be used. Slope components calculated from digital elevation models of areas in North Wales and the French Alps are found to have double-exponential distributions. From this result, expressions are developed for the fractions of the areas that will be either self-shaded or shaded by remote topography as functions of solar elevation and time of day. These expressions are in good agreement with results from a terrain shading model. Keywords: solar radiation, topography, surface energy balance, statistical parameterisation
Using stable isotopes of water to infer wetland hydrological dynamics
Authors: Clay A. , Bradley C. , Gerrard A. J. , Leng M. J.
Published: April 2010

Abstract. This paper considers the potential of oxygen and hydrogen isotope ratios to identify spatial and temporal changes in the water source of a lowland headwater wetland situated adjacent to the River Tern in Shropshire, UK. Stable isotope composition (d18O) of end-members varied between –7.5 and –8.0‰ for groundwater, –7.3 and –8.5‰ for river-water and –4.5 and –8.0‰ for precipitation. Water samples were extracted from six nests each comprising three porous cup samplers at depths of 0.2 m, 0.5 m and 1.0 m between June 2000 and October 2001, and their isotope compositions determined. Groundwater appears to be the main source of water to the wetland, but stable isotope ratios enable seasonal variations in the contribution of precipitation to be determined, and indicate the extent of precipitation storage within the wetland. Keywords: oxygen and hydrogen isotopes, water source, hydrodynamics, lowland wetland
Research Note:Derivation of temperature lapse rates in semi-arid south-eastern Arizona
Authors: Harlow R. C. , Burke E. J. , Scott R. L. , Shuttleworth W. J. , Brown C. M. , Petti J. R.
Published: April 2010

Abstract. Ecological and hydrological modelling at the regional scale requires distributed information on weather variables, and temperature is important among these. In an area of basin and range topography with a wide range of elevations, such as south-eastern Arizona, measurements are usually available only at a relatively small number of locations and elevations, and temperatures elsewhere must be estimated from atmospheric lapse rate. This paper derives the lapse rates to estimate maximum, minimum and mean daily temperatures from elevation. Lapse rates were calculated using air temperatures at 2 m collected during 2002 at 18 locations across south-eastern Arizona, with elevations from 779 to 2512 m. The lapse rate predicted for the minimum temperature was lower than the mean environmental lapse rate (MELR), i.e. 6 K km–1, whereas those predicted for the mean and maximum daily temperature were very similar to the MELR. Lapse rates were also derived from radiosonde data at 00 and 12 UTC (5 pm and 5 am local time, respectively). The lapse rates calculated from radiosonde data were greater than those from the 2 m measurements, presumably because the effect of the surface was less. Given temperatures measured at Tucson airport, temperatures at the other sites were predicted using the different estimates of lapse rates. The best predictions of temperatures used the locally predicted lapse rates. In the case of maximum and mean temperature, using the MELR also resulted in accurate predictions. Keywords: near surface lapse rates, semi-arid climate, mean minimum and maximum temperatures, basin and range topography
A model for simulating the deposition of water-lain sediments in dryland environments
Authors: Bunch M. A. , Mackay R. , Tellam J. H. , Turner P.
Published: April 2010

Abstract. A numerical process-imitating model, the Discrete Storm Event Sedimentation Simulator (DSESS), has been developed to represent the climatic and hydraulic conditions of drylands in modelling their geomorphological development and sedimentary facies distributions. The ultimate aim is to provide insights into the lateral variability of permeability in the Triassic Sandstone aquifers of the UK for the study of solute movement. DSESS employs discrete storm-flood automata, released across a cellular landscape, to model sediment transport: erosion, migration and deposition. Sediment classes with different grain sizes can be modelled. Empirical process-based equations are used to quantify the movement of the automata, their erosion potential, sediment-carrying capacity and interaction with the underlying sediments. The approach emphasises the sequence of dryland storm events and associated floods rather than their timing. Flood events are assumed to be discrete in time. Preliminary tests carried out with DSESS using simple systems and idealised initial conditions produce lithological and land surface features characteristic of dryland settings and indicate the potential of the model for large-scale, long-time modelling of sedimentary facies development. Markedly different results are observed across the range of tests carried out in response to the non-linear interactions between the different elements of the landscape and the floodwaters simulated with DSESS. Simulations show that sediment accumulations develop concave upward radial profiles, plano-convex cross-profiles and possess a general lateral grading of sediment with distance from source. The internal grain size architecture shows evidence of both persistent and rapidly changing flow conditions, with both lateral and longitudinal stepping of coarse bodies produced by ‘scour and fill’ events and random avulsions. Armoured layers form so that near-surface sediments have increased likelihood of preservation. Future developments will include representation of aeolian deposition, mass wasting and hyper-concentrated (debris) flows. Keywords: avulsion, channel, deposition, drylands, erosion, gravel armouring, modelling, sheet-flood, transport capacity
Sampling variance of flood quantiles from the generalised logistic distribution estimated using the method of L-moments
Authors: Kjeldsen Thomas R. , Jones David A.
Published: April 2010

Abstract. The method of L-moments is the recommended method for fitting the three parameters (location, scale and shape) of a Generalised Logistic (GLO) distribution when conducting flood frequency analyses in the UK. This paper examines the sampling uncertainty of quantile estimates obtained using the GLO distribution for single site analysis using the median to estimate the location parameter. Analytical expressions for the mean and variance of the quantile estimates were derived, based on asymptotic theory. This has involved deriving expressions for the covariance between the sampling median (location parameter) and the quantiles of the estimated unit-median GLO distribution (growth curve). The accuracy of the asymptotic approximations for many of these intermediate results and for the quantile estimates was investigated by comparing the approximations to the outcome of a series of Monte Carlo experiments. The approximations were found to be adequate for GLO shape parameter values between –0.35 and 0.25, which is an interval that includes the shape parameter estimates for most British catchments. An investigation into the contribution of different components to the total uncertainty showed that for large returns periods, the variance of the growth curve is larger than the contribution of the median. Therefore, statistical methods using regional information to estimate the growth curve should be considered when estimating design events at large return periods. Keywords: flood frequency analysis, Flood Estimation Handbook, single site, annual maximum series, Generalised Logistic Distribution, uncertainty
Radar rainfall image repair techniques
Authors: Wesson Stephen M. , Pegram Geoffrey G. S.
Published: April 2010

Abstract. There are various quality problems associated with radar rainfall data viewed in images that include ground clutter, beam blocking and anomalous propagation, to name a few. To obtain the best rainfall estimate possible, techniques for removing ground clutter (non-meteorological echoes that influence radar data quality) on 2-D radar rainfall image data sets are presented here. These techniques concentrate on repairing the images in both a computationally fast and accurate manner, and are nearest neighbour techniques of two sub-types: Individual Target and Border Tracing. The contaminated data is estimated through Kriging, considered the optimal technique for the spatial interpolation of Gaussian data, where the "screening effect" that occurs with the Kriging weighting distribution around target points is exploited to ensure computational efficiency. Matrix rank reduction techniques in combination with Singular Value Decomposition (SVD) are also suggested for finding an efficient solution to the Kriging Equations which can cope with near singular systems. Rainfall estimation at ground level from radar rainfall volume scan data is of interest and importance in earth bound applications such as hydrology and agriculture. As an extension of the above, Ordinary Kriging is applied to three-dimensional radar rainfall data to estimate rainfall rate at ground level. Keywords: ground clutter, data infilling, Ordinary Kriging, nearest neighbours, Singular Value Decomposition, border tracing, computation time, ground level rainfall estimation
The construction of confidence intervals for frequency analysis using resampling techniques
Authors: Hall M. J. , van den Boogaard H. F. P , Fernando R. C. , Mynett A. E.
Published: April 2010

Abstract. Resampling techniques such as the Bootstrap and the Jack-knife are generic methods for the estimation of uncertainties in statistics. When applied in frequency analysis, resampling techniques can provide estimates of the uncertainties in both distribution parameters and quantile estimates in circumstances in which confidence limits cannot be obtained theoretically. Test experiments using two different parameter estimation methods on two types of distributions with different initial sample sizes and numbers of resamples has confirmed the utility of such methods. However, care is necessary in evaluating the skewness of the resampled quantiles, especially with small initial sample sizes. Keywords: Bootstrap, Jack-knife, frequency analysis, maximum likelihood method, maximum product of spacings method
Chloride concentrations in Lake Tanganyika: an indicator of the hydrological budget?
Authors: Branchu Ph. , Bergonzini L.
Published: April 2010

Abstract. On a historical time scale, this paper investigates the effect of hydroclimatic variations on the surface water salinity of Lake Tanganyika, the largest African lake and an open freshwater reservoir. Through annual water and chemical budgets, based on original and bibliographic data, a tracer of the water regime is proposed. Chloride, an inert and conservative element, seems to be the best candidate although its contribution to salinity is small; its use as a tracer of the water regime is validated on seasonal and historical time scales. Seasonally, a monthly water and chloride budget, constructed for an average year has been compared with data acquired in 1973. On a historical time scale, bibliographic data of chloride concentrations, compiled since 1939 have been compared with the level variation curve. The relation between lake level and surface water chloride concentration is significant on both time scales. Hence, the surface salinity/chlorinity of this freshwater lake is sensitive to hydroclimatic variations even if level variations are very limited in comparison with its great depth. This sensitivity is due mainly to the permanent thermo-haline stratification of the lake. Keywords: climate, water budget, hydrochemical budget, Lake Tanganyika, limnology, salinity
Seasonal and diurnal hydro-chemical variations in a recreated reed bed
Authors: Stratford C. J. , McCartney M. P. , Williams R. J.
Published: April 2010

Abstract. To help stem this decline, wetland areas are now being preserved and where possible created. This study investigated water quality in a recreated reed bed in south-west England designed specifically to provide habitat for birds. Since June 2000, continuous measurements of temperature, pH, electrical conductivity and dissolved oxygen have been logged. These data enable the partial pressure of CO2 to be calculated. This paper looks at the data collected up to November 2001. Despite similar solar radiation and water temperature conditions in both 2000 and 2001, peak summertime values of dissolved oxygen dropped from >100% to <50% and pH values dropped from >7.7 to <7.2. Both also show a reduction in diurnal variation. Over the same period, the average partial pressure of CO2 increased from 19.7 to 56.1. Analysis of the diurnal dissolved oxygen curves indicates a decrease in photosynthesis which, in the absence of a change in nutrient concentrations in the water, may result from surface plant growth or from a reduction in submerged plant cover. The implications of these changing hydro-chemical conditions are that the site will be less able to support such a wide diversity of aquatic fauna, which will reduce the effectiveness of the site as a habitat for some bird species. Keywords: wetland, reed bed, hydrochemistry, dissolved oxygen, pH, continuous monitoring, Hamwall, Somerset Levels
An overview of forest management and change with respect to environmental protection in the UK
Authors: Farmer R. A. , Nisbet T. R.
Published: April 2010

Abstract. This paper overviews changes in forest management in the UK with respect to environmental protection. The evolution of policy is explained from historical and sustainability perspectives and covers developments in forest planning, accreditation, devolution and future challenges and opportunities. Keywords: forest management, best practice, sustainable forestry, environmental protection, land use change
The effects of riparian forest management on the freshwater environment: a literature review of best management practice
Authors: Broadmeadow S. , Nisbet T. R.
Published: April 2010

Abstract. National Forests and Water Guidelines require the establishment of riparian buffers to help protect the freshwater environment from disturbance by silvicultural operations on the adjacent land. The main functions of the riparian buffer are considered to be sediment removal and erosion control, protection of water quality, moderation of shade and water temperature, maintenance of habitat structural diversity and ecological integrity, and improvement of landscape quality. This review paper assesses how these functions are affected by the design and management of the riparian forest zone, with a focus on the width of the buffer, the structure of the vegetation and species choice. It is not possible to specify a definitive riparian buffer width that will protect the freshwater environment from every potential threat. Forestry agencies usually recommend widths between 10 and 30 m. Buffer widths towards the lower end of this scale tend to protect the physical and chemical characteristics of a stream, while the maintenance of ecological integrity requires widths at the upper end. In terms of structure and species, the benefits are greatest where the riparian buffer replicates native riparian woodland with an open canopy of mixed species of varied age class. The optimum level of shade is difficult to quantify but limited work suggests that a good balance is achieved where around 50% of the stream surface is open to sunlight and the remainder covered by dappled shade. Within the management of riparian woodland there is a need to consider a stream’s sensitivity and intrinsic value. Some sites will benefit from active intervention such as thinning, coppicing or pollarding, while others will be favoured by a hands-off approach. Long-term continuity of management is important to ensure that the potential benefits to the freshwater environment are realised. Keywords: riparian woodland, riparian buffer, woodland management, freshwater environment, water quality
Anatomy of a catchment: the relation of physical attributes of the Plynlimon catchments to variations in hydrology and water status
Authors: Brandt C. , Robinson M. , Finch J. W.
Published: April 2010

Abstract. The Plynlimon headwater catchments in mid-Wales have been a landmark study of water resources in the UK uplands for over 30 years. The main physical features of the catchments have been digitised as the basis for linking new model developments and process understanding. Examples are given of how the main physical attributes are related to land management, hydrology and water quality. These data are also being used to provide insights into catchment processes that may underpin the development of new research. This work is particularly relevant given the need for the assessment of water status under the Water Framework Directive. The paper presents hypothetical management scenarios for the catchments, to show how ecological status may be improved, for example, by selectively restructuring areas of commercial forest. Keywords: Plynlimon, GIS, catchment study, forestry, hydrology, WFD
Effects of five years of frequent N additions, with or without acidity, on the growth and below-ground dynamics of a young Sitka spruce stand growing on an acid peat: implications for sustainability
Authors: Sheppard L. J. , Crossley A. , Harvey F. J. , Skiba U. , Coward P. , Ingleby K.
Published: April 2010

Abstract. A field manipulation study was established to demonstrate effects of simulated wet N and S deposition on a young (planted 1986) stand of Sitka spruce growing on a predominantly organic soil in an area of low (8–10 kg N ha-1 yr-1) background N deposition in the Scottish borders. From 1996, treatments (six) were applied to the canopies of ten-tree plots in each of four blocks. N was provided as NH4NO3, either with H2SO4 (pH 2.5) at 48 or 96 kg N ha-1 yr-1 inputs or without, at 48 kg N ha-1 yr-1 along with wet (rain water) and dry controls (scaffolding) and a S treatment (Na2SO4). Positive responses (+ >20% over 5 years) with respect to stem area increment were measured in response to N inputs, irrespective of whether acid was included. The positive response to N was not dose related and was achieved against falling base cation concentrations in the foliage, particularly with respect to K. The results suggest young trees are able to buffer the low nutrient levels and produce new growth when there is sufficient N. Inputs of 96 kg N ha-1 yr-1, in addition to ambient N inputs, on this site exceeded tree demand resulting in elevated foliar N, N2O losses and measurable soil water N. These excessive N inputs did not reduce stem area growth. Keywords: acid, canopy application, nitrogen, acid organic soil, simulated wet deposition, soil water, sulphur, young Sitka spruce
The effects of H2SO4 and (NH4)2SO4 treatments on the chemistry of soil drainage water and pine seedlings in forest soil microcosms
Authors: Stutter M. I. , Alam M. S. , Langan S. J. , Woodin S. J. , Smart R. P , Cresser M. S.
Published: April 2010

Abstract. An experiment comparing effects of sulphuric acid and reduced N deposition on soil water quality and on chemical and physical growth indicators for forest ecosystems is described. Six H2SO4 and (NH4)2SO4 treatment loads, from 0 – 44 and 0 – 25 kmolc ha-1 yr-1, respectively, were applied to outdoor microcosms of Pinus sylvestris seedlings in 3 acid to intermediate upland soils (calc-silicate, quartzite and granite) for 2 years. Different soil types responded similarly to H2SO4 loads, resulting in decreased leachate pH, but differently to reduced N inputs. In microcosms of calc-silicate soil, nitrification of NH4 resulted in lower pH and higher cation leaching than in acid treatments. By contrast, in quartzite and granite soils, (NH4)2SO4 promoted direct cation leaching, although leachate pH increased. The results highlighted the importance of soil composition on the nature of the cations leached, the SO4 adsorption capacities and microbial N transformations. Greater seedling growth on calc-silicate soils under both treatment types was related to sustained nutrient availability. Reductions in foliar P and Mg with higher N treatments were observed for seedlings in the calc-silicate soil. There were few treatment effects on quartzite and granite microcosm tree seedlings since P limitation precluded seedling growth responses to treatments. Hence, any benefits of N deposition to seedlings on quartzite and granite soils appeared limited by availability of co-nutrients, exacerbated by rapid depletion of soil exchangeable base cations. Keywords: acidification, manipulation, nitrogen, ammonium, deposition, soil, drainage, pine, microcosms, forest
The hydrochemistry of plantation spruce forest catchments with brown earth soils, Vyrnwy in mid-Wales
Authors: Neal C. , Reynolds B. , Neal M. , Williams B.
Published: April 2010

Abstract. At Vyrnwy, in mid-Wales, a study of the hydrogeochemistry of two small spruce forested catchments, one a control and one felled midway through the study, shows a classic picture of rainfall inputs damped by the catchment and stream waters the chemistry of which varies as functions of flow and particularly of the supply of more acidic and aluminium-bearing soil water and of more basic and calcic ground waters from the zone where weathering reactions with the bedrock are high. The ground waters are most alkaline although pH may be depressed due to high dissolved carbon dioxide pressures. Nitrate concentrations increase in the first year after felling and decrease thereafter below those of the control. Water quality changes due to the dominant hydrogeochemical processes show that harvesting raises no significant water quality management issues. Keywords: Gran alkalinity, aluminium, spruce, harvesting, forestry, nutrients, trace elements, Vyrnwy, water quality
The response of macroinvertebrates to artificially enhanced detritus levels in plantation streams
Authors: Pretty J. L. , Dobson M.
Published: April 2010

Abstract. The leaves and wood from vegetation surrounding headwater streams constitute a major food source for aquatic invertebrates, providing they are retained upon the streambed and not transported downstream. This study investigated the response of aquatic invertebrates to artificially increased detritus retention, in an effort to reproduce the naturally occurring build up of dead organic matter associated with streams in old-growth forest. The background detrital standing stock in streams in Kielder Forest (Northumberland, UK) was low, approximately 32 gm-2. Two streams flowing through dense conifer plantation and one in open broadleaved woodland were manipulated by the addition of logs over a 10 m stream reach. After several months, log addition significantly enhanced detrital standing stocks in both conifer and broadleaved streams. Total invertebrate abundance, taxon richness and the numbers of certain numerically dominant families were significantly higher in experimental than reference reaches in both conifer and broadleaved streams. This response was most marked for detritivores, whilst non-detritivore groups often showed no response to the manipulation. Whilst in the short term the responses to enhanced retention may reflect a redistribution of the local fauna, it is argued that over a longer time-scale, a genuine increase in invertebrate density and diversity could occur. Allowing old-growth forest to develop in planted valley bottoms may be a viable management option for conservation. If established alongside streams, it would ensure continuous input of woody material and the fauna may benefit from the resulting increase in detritus retention. Keywords: forestry, detritivores, old-growth conifers, river management, woody debris
Processing of pine (Pinus sylvestris) and birch (Betula pubescens) leaf material in a small river system in the northern Cairngorms, Scotland
Authors: Collen P. , Keay E. J. , Morrison B. R. S.
Published: April 2010

Abstract. Processing rates, and macroinvertebrate colonisation, of pine needles and birch leaves were studied at eight sites on the river Nethy, a small river system in the Cairngorm region of north-eastern Scotland. Throughout this river system, processing rates were slow for pine (k values 0.0015-0.0034 day-1) and medium to fast for birch (k values 0.0085-0.0331 day-1). Plecopteran shredders dominated both pine and birch leaf packs during the early part of the experiment while chironomids were more important in the latter stages. It is suggested that the slow processing rate of pine needles could adversely affect the productivity of streams, particularly where needles provide the major allochthonous energy source and retentive features are limited. Forest managers should consider this when creating new pinewoods in treeless areas as it will take many years for the trees to reach a size at which they can effectively contribute retentive features, in the form of woody debris, to streams. Keywords: leaf processing, pine needles, shredders, Pinus sylvestris, Betula pubescens, Scotland.
Sustainability of UK forestry: contemporary issues for the protection of freshwaters, a conclusion
Authors: Neal C. , Ormerod S. J. , Langan S. J. , Nisbet T. R. , Roberts J.
Published: April 2010

Abstract. This paper closes the Special Issue of Hydrology and Earth System Sciences entitled "Sustainability of UK forestry: contemporary issues for the protection of freshwaters" by presenting conclusions from the contributions together with associated research findings. The volume deals largely with issues of upland water quality and biology in the context of environmental research and management. The studies are linked to an array of issues which affect the sustainability of UK forestry in the context of the protection of freshwaters, freshwater ecosystems and freshwater organisms. These issues include atmospheric and climate driven factors (acidification from atmospheric pollutants, critical loads, climate-change and climate variability), forestry practice and hydrobiogeochemical processing both within-catchments and within-rivers. The findings lie within the context of the science and relate to environmental management. Keywords: water quality, forestry, stream ecology, acidification, critical loads, nutrients
Rainfall and runoff water quality of the Pang and Lambourn, tributaries of the River Thames, south-eastern England
Authors: Neal C. , Skeffington R. , Neal M. , Wyatt R. , Wickham H. , Hill L. , Hewitt N.
Published: April 2010

Abstract. The water quality of rainfall and runoff is described for two catchments of two tributaries of the River Thames, the Pang and Lambourn. Rainfall chemistry is variable and concentrations of most determinands decrease with increasing volume of catch probably due to "wash out" processes. Two rainfall sites have been monitored, one for each catchment. The rainfall site on the Lambourn shows higher chemical concentrations than the one for the Pang which probably reflects higher amounts of local inputs from agricultural activity. Rainfall quality data at a long-term rainfall site on the Pang (UK National Air Quality Archive) shows chemistries similar to that for the Lambourn site, but with some clear differences. Rainfall chemistries show considerable variation on an event-to-event basis. Average water quality concentrations and flow-weighted concentrations as well as fluxes vary across the sites, typically by about 30%. Stream chemistry is much less variable due to the main source of water coming from aquifer sources of high storage. The relationship between rainfall and runoff chemistry at the catchment outlet is described in terms of the relative proportions of atmospheric and within-catchment sources. Remarkably, in view of the quantity of agricultural and sewage inputs to the streams, the catchments appear to be retaining both P and N. Keywords: water quality, nitrate, ammonium, phosphorus, ammonia, nitrogen dioxide, pH, alkalinity, nutrients, trace metals, rainfall, river, Pang, Lambourn, LOCAR
Adaptation of the Integrated Nitrogen Model for Catchments (INCA) to seasonally snow-covered catchments
Authors: Rankinen K. , Kaste Ø. , Butterfield D.
Published: April 2010

Abstract. Testing of the Integrated Nitrogen model for Catchments (INCA) in a wide range of ecosystem types across Europe has shown that the model underestimates N transformation processes to a large extent in northern catchments of Finland and Norway in winter and spring. It is found, and generally assumed, that microbial activity in soils proceeds at low rates at northern latitudes during winter, even at sub-zero temperatures. The INCA model was modified to improve the simulation of N transformation rates in northern catchments, characterised by cold climates and extensive snow accumulation and insulation in winter, by introducing an empirical function to simulate soil temperatures below the seasonal snow pack, and a degree-day model to calculate the depth of the snow pack. The proposed snow-correction factor improved the simulation of soil temperatures at Finnish and Norwegian field sites in winter, although soil temperature was still underestimated during periods with a thin snow cover. Finally, a comparison between the modified INCA version (v.1.7) and the former version (v.1.6) was made at the Simojoki river basin in northern Finland and at Dalelva Brook in northern Norway. The new modules did not imply any significant changes in simulated NO3- concentration levels in the streams but improved the timing of simulated higher concentrations. The inclusion of a modified temperature response function and an empirical snow-correction factor improved the flexibility and applicability of the model for climate effect studies. Keywords: inorganic N leaching, degree-day snow model, snow pack, catchment scale model
Testing the INCA model in a small agricultural catchment in southern Finland
Authors: Granlund K. , Rankinen K. , Lepistö A.
Published: April 2010

Abstract. Nutrient leaching from agricultural production is still recognised as a major environmental problem in Finland. To estimate agricultural nitrogen loading under changing land-use and climate conditions, the Integrated Nitrogen Model for Catchments (INCA) was applied in Savijoki, a small (15.4 km2) agricultural catchment, which represents the intensively cultivated areas in south-western Finland. Hydrological calibration and testing of the INCA model was first carried out in Savijoki during 1981–2000. In spite of heterogeneous soil and land-use conditions, INCA was able to reproduce the overall hydrological regime in the stream. The model was calibrated further in respect of nitrogen processes during 1995–2000. The model was able, reasonably well, to simulate the overall annual dynamics of the inorganic N concentrations in the stream water and the annual N export from the catchment. The average simulated NO3-N export was 550 kg N km–2 yr–1 and the observed one (constituting more than half of the annual total N export) was 592 kg N km–2 yr–1. For NH4-N, the simulated export was somewhat higher than that measured but NH4-N was only 4% of the total N export. In spite of some underestimation of flow and N concentration during extreme hydrological conditions, the INCA model proved to be a useful tool for analysing flow pattern and inorganic nitrogen leaching in a small agricultural catchment, characterised by a rapid response to rainfall. Keywords: nitrogen, integrated modelling, hydrology, catchment, agriculture
Towards reduced uncertainty in catchment nitrogen modelling: quantifying the effect of field observation uncertainty on model calibration
Authors: Raat K. J. , Vrugt J. A. , Bouten W. , Tietema A.
Published: April 2010

Abstract. The value of nitrogen (N) field measurements for the calibration of parameters of the INCA nitrogen in catchment model is explored and quantified. A virtual catchment was designed by running INCA with a known set of parameters, and field "measurements" were selected from the model run output. Then, using these measurements and the Shuffled Complex Evolution Metropolis algorithm (SCEM-UA), four of the INCA model parameters describing N transformations in the soil were optimised, while the measurement uncertainty was increased in subsequent steps. Considering measurement uncertainty typical for N field studies, none of the synthesised datasets contained sufficient information to identify the model parameters with a reasonable degree of confidence. Parameter equifinality occurred, leading to considerable uncertainty in model parameter values and in modelled N concentrations and fluxes. Fortunately, combining the datasets in a multi-objective calibration was found to be effective in dealing with these equifinality problems. With the right choice of calibration measurements, multi-objective calibrations resulted in lower parameter uncertainty. The methodology applied in this study, using a virtual catchment free of model errors, is proposed as a useful tool foregoing the application of a N model or the design of a N monitoring program. For an already gauged catchment, a virtual study can provide a point of reference for the minimum uncertainty associated with a model application. When setting up a monitoring program, it can help to decide what and when to measure. Numerical experiments indicate that for a forested, N-saturated catchment, a fortnightly sampling of NO3 and NH4 concentrations in stream water may be the most cost-effective monitoring strategy. Keywords: INCA, nitrogen model, parameter uncertainty, multi-objective calibration, virtual catchment, experimental design