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Peatlands are long term carbon catchments that sink atmospheric carbon dioxide (CO2) and source methane (CH4). In the uplands of the United Kingdom ombrotrophic blanket peatlands commonly exist within Calluna vulgaris (L.) dominated moorland ecosystems. These landscapes contain a range of topographical features that influence local hydrology, climate and plant community composition. In this study we examined the variation in ecosystem CO2 respiration and net CH4 fluxes from typical plant-soil systems in dendritic drainage gullies and adjacent blanket peat during the growing season. Typically, Eriophorum spp., Sphagnum spp. and mixed grasses occupied gullies while C. vulgaris dominated in adjacent blanket peat. Gross CO2 respiration was highest in the areas of Eriophorum spp. (650±140 mg CO2 m−2 h−1) compared to those with Sphagnum spp. (338±49 mg CO2 m−2 h−1), mixed grasses (342±91 mg CO2 m−2 h−1) and C. vulgaris (174±63 mg CO2 m−2 h−1). Measurements of the net CH4 flux showed higher fluxes from the Eriophorum spp (2.2±0.6 mg CH4 m−2 h−1) locations compared to the Sphagnum spp. (0.6±0.4 mg CH4 m−2 h−1), mixed grasses (0.1±0.1 mg CH4 m−2 h−1) and a negligible flux detected from C. vulgaris (0.0±0.0 mg CH4 m−2 h−1) locations. A GIS approach was applied to calculate the contribution of gullies to landscape scale greenhouse gas fluxes. Findings from the Moor House National Nature Reserve in the UK showed that although gullies occupied only 9.3% of the total land surface, gullies accounted for 95.8% and 21.6% of the peatland net CH4 and CO2 respiratory fluxes, respectively. The implication of these findings is that the relative contribution of characteristic gully systems need to be considered in estimates of landscape scale peatland greenhouse gas fluxes. [Copyright &y& Elsevier]

Abstract: Methanotroph community structure and activity was investigated in a peat soil in which the above-ground vegetation was burned repeatedly during the last 50 years, and in soil unburned since 1954. Regular burning (every 10 years) was found to have no obvious impact on the potential methane-uptake capacity; however, a lower abundance of type I methanotrophs relative to type II methanotrophs in the frequently burned soils was observed using pmoA (encoding a key polypeptide of particulate methane monooxygenase) microarray analyses. Denaturing gradient gel electrophoresis of bacterial 16S rRNA genes indicated that the total bacterial community, and not just the methanotrophs, was affected by the burning. The regular burning also resulted in a decreased abundance of Calluna vegetation relative to mixed grasses in the peatland plots. In a separate mesocosm experiment, Calluna plants and their roots were removed from the peat soils for a growing season (from February 2006 to November 2006). It was shown that removal of Calluna from the soil greatly decreased the methane-uptake capacity of the soils, although no obvious impact on the methanotroph population structure was observed. Real-time PCR quantification of pmoA genes showed that the abundance of methanotrophs in barren soil (without Calluna vegetation) was about fivefold less than in the control soil (with Calluna vegetation). These findings indicate that the methanotroph community is strongly influenced by the above-ground vegetation cover. Burning of Calluna seemed to favour the type II methanotrophs, whereas the removal of the Calluna cover did not appear to affect the relative abundance of methanotroph genera but caused a uniform decrease in the size of methanotroph populations. [Copyright &y& Elsevier]

Abstract: Increased plant productivity due to nitrogen pollution increases the strength of the global carbon sink, but is implicated in plant diversity loss. However, modelling and experimental studies have suggested that these effects are constrained by availability of other nutrients. In a survey of element concentrations in Calluna vulgaris across an N deposition gradient in the UK, shoot concentrations of N and more surprisingly phosphorus and potassium were positively correlated with N deposition; tissue N/P ratio even decreased with N deposition. Elevated P and K concentrations possibly resulted from improved acquisition due to additional enzyme production or mycorrhizal activity. Heather occurs on organic soils where nutrient limitations are likely due to availability constraints rather than small stocks. However, if this effect extends to other plant and soil types, effects of N deposition on C sinks and plant competition may not be as constrained by availability of other nutrients as previously proposed. [Copyright &y& Elsevier]

Calluna vulgaris-dominated heaths and moorlands are habitats of international conservation importance. Degradation has occurred throughout their range with Calluna typically being replaced by grass species. The cessation of grazing is often impractical and rarely results in the recovery of Calluna abundance when it is initially present at low cover. Thus the development of restoration methods is required; these should be practical at a large-scale, in remote areas and create suitable conditions for Calluna germination and establishment, whilst still allowing grazing to occur. A replicated field experiment was established on Nardus stricta and Molinia caerulea-dominated moorlands to test the efficacy of different grazing regimes and intervention techniques aimed at establishing Calluna. Disturbance (rotavation and trampling by animals) to create bare ground increased Calluna establishment. On the Nardus site, Calluna establishment was equally successful on rotavated and trampled plots, but rotavation was more successful on the Molinia site. Seeding with Calluna increased Calluna establishment irrespective of whether a seed-bank was present. At the Nardus site, 0.5cow/ha for two months in summer led to Calluna establishment and growth similar to that of ungrazed plots and was more successful than a mixed grazing regime (1ewe/ha plus 0.5cow/ha for 2 months) or a sheep only regime (1.5ewes/ha). The creation of small patches of bare ground, seed addition and low intensity grazing enabled the rapid establishment of Calluna on grass-dominated moorlands; such techniques may also be applicable in other habitats where restoration requires the addition of a single/few species and minimal intervention. [Copyright &y& Elsevier]

Abstract: Effects and implications of reduced and oxidised N, applied under ‘real world’ conditions, since May 2002, are reported for Calluna growing on an ombrotrophic bog. Ammonia has been released from a 10m line source generating monthly concentrations of 180–6μg m−3, while ammonium chloride and sodium nitrate are applied in rainwater at nitrate and ammonium concentrations below 4mM and providing up to 56kg N ha−1 year−1 above a background deposition of 10 kg N ha−1 year−1. Ammonia concentrations, >8μg m−3 have significantly enhanced foliar N concentrations, increased sensitivity to drought, frost and winter desiccation, spring frost damage and increased the incidence of pathogen outbreaks. The mature Calluna bushes nearest the NH3 source have turned bleached and moribund. By comparison the Calluna receiving reduced and oxidised N in rain has shown no significant visible or stress related effects with no significant increase in N status. [Copyright &y& Elsevier]

Background: Calluna vulgaris is a woody shrub forming plant communities of economic and international conservation importance. Following winter 2002-2003, there was exceptional Calluna die-back in the central Scottish Highlands. Aim: To understand the effects and causes of this die-back event at Abernethy Forest Nature Reserve, Cairngorms National Park. Methods: Patterns of weather, foliage moisture and microclimate were interpreted in relation to patterns of Calluna vulgaris die-back. Vegetation development was investigated over 4 years, based on pre-existing monitoring plots. Results: February 2003 included a period of exceptionally low air humidity, during which unusually low Calluna shoot moisture readings were made, particularly in areas that subsequently had severe die-back. In monitored areas, Calluna cover declined by a third, with minimal recovery after three growing seasons. Die-back was more severe where Calluna was longer-stemmed and less abundant, and where topography was flatter or more north-facing. These topographical features, and die-back, were correlated with colder winter microclimates. A doubling in Vaccinium myrtillus cover in forest plots was strongly correlated with the pattern of Calluna die-back. Meteorological data showed an eight-fold increase in the variability of winter humidity minima since 1983-1984. Conclusions: Die-back probably followed severe 'winter desiccation', caused by extreme low humidity conditions, combined with low temperatures, lack of snow cover, and Calluna vulnerability due to age. It led to a major vegetation change in the direction of management aims at this site, but contrary to aims at many other Calluna-dominated sites. The importance of climatic variability as a potential driver of major vegetation change is emphasised. [ABSTRACT FROM AUTHOR]

Abstract: A flux chamber experiment employing 15N-NH3 was run for a period of 15 days to quantify uptake of NH3 into the component parts of Calluna vulgaris and peat substrate. The results showed that the total N recovered from the vegetation system correlated extremely well with AMANDA deposition measurement, over the whole 15-day period, accounting for all the deposited NH3. The data showed that NH3 was taken up into the above ground biomass over the 15 days of the experiment; 75% was found in green shoots and leaves and 11% in brown shoots. The larger uptake by green shoots and leaves was presumably related to the presence of stomata and the cuticular surface area. Only 1% was captured by the peat due to the closed C. vulgaris canopy. There was little translocation of N from deposited NH3 into the roots and peat. For C. vulgaris it can be calculated that 75% of the above ground deposition was onto the cuticle and only 25% into the stomata. [Copyright &y& Elsevier]

Understanding the factors that drive successful re-creation and restoration of lowland heaths is crucially important for achieving the long-term conservation of this threatened habitat type. In this study we investigated the changes in soil chemistry, plant community and interactions between Calluna vulgaris and symbiotic ericoid mycorrhizas (ERM) that occurred when improved pasture was subjected to one of three treatments (i) acidification with elemental sulphur (ii) acidification with ferrous sulphur (iii) removal of the topsoil. We found that the soil stripping treatment produced the greatest reduction in available phosphate but did not decrease soil pH. Conversely, acidification with elemental sulphur decreased pH but increased availability of phosphate and potentially toxic cations. The elemental sulphur treatment produced plant communities that most closely resembled those on surrounding heaths and acid grasslands. The most important driver was low pH and concomitant increased availability of potentially toxic cations. Plant community development was found to be little related to levels of available soil phosphate, particularly at low pH. The elemental sulphur treatment also produced the best germination and growth of C. vulgaris over 4–5years. However, this treatment was found to inhibit the development of symbiotic relationships between C. vulgaris and ERM. This may affect the long-term persistence of re-created vegetation and its interactions with other components of heathland communities. [Copyright &y& Elsevier]

Peatlands are important reservoirs of carbon (C) but our understanding of C cycling on cutover peatlands is limited. We investigated the decomposition over 18 months of five types of plant litter ( Calluna vulgaris, Eriophorum angustifolium, Eriophorum vaginatum, Picea sitchensis and Sphagnum auriculatum) at a cutover peatland in Scotland, at three water tables. We measured changes in C, nitrogen (N) and phosphorus (P) in the litter and used denaturing gradient gel electrophoresis to investigate changes in fungal community composition. The C content of S. auriculatum litter did not change throughout the incubation period whereas vascular plant litters lost 30–40% of their initial C. There were no differences in C losses between low and medium water tables, but losses were always significantly less at the high water table. Most litters accumulated N and E. angustifolium accumulated significant quantities of P. C, N and P were significant explanatory variables in determining changes in fungal community composition but explained <25% of the variation. Litter type was always a stronger factor than water table in determining either fungal community composition or turnover of C, N and P in litter. The results have implications for the ways restoration programmes and global climate change may impact upon nutrient cycling in cutover peatlands. [ABSTRACT FROM AUTHOR]

Abstract: Nitrogen deposition is a continuing problem in European alpine regions. We hypothesised that, despite climatic limitations, low-alpine Calluna heathland would respond to nitrogen addition with increased shoot growth and flowering and that fire and grazing would modify responses. In a five-year study, 0–50kgNha−1 y−1 were added, combined with burning (+/−) and clipping (+/−). Calluna vulgaris responded with increased shoot extension, but effects on flowering were variable. Burning enhanced the positive effect of nitrogen addition and negative effects of clipping. Sub-dominant shrubs generally did not respond to nitrogen. C. vulgaris shoot extension was stimulated by nitrogen addition of 10kgNha−1 y−1 (above background) supporting suggestions that alpine heathlands are sensitive to low levels of nitrogen deposition. Increased C. vulgaris growth could negatively impact on important lichen components of this vegetation through increased shading and competition. Climatic factors constrain productivity in this community, but do not prevent rapid responses to nitrogen deposition by some species. [Copyright &y& Elsevier]

We present a simple non-destructive technique for assessing fuel load and critical aspects of vegetation structure that play important roles in determining fire behaviour. The method is tested in a Scottish Calluna vulgaris (L.) Hull heathland but could be applied to any vegetation up to ~1 m high. Visual obstruction of a banded measurement stick (the FuelRule) placed vertically through a stand of vegetation is governed by a combination of the height of the vegetation and its density. The vertical distribution of visual obstruction is calibrated to give estimates of total fuel loading, the loading of separate size categories and the vertical distribution and horizontal heterogeneity of fuels. The present paper provides a quick and simple method for estimating total aboveground biomass and structure that may be useful not just in studies of fire behaviour but where non-destructive assessment of biomass, vegetation density or canopy structure is needed. Calibration equations can be rapidly created for use in other vegetation or fuel types. [ABSTRACT FROM AUTHOR]

We studied the short- and medium-term effects of experimental nitrogen fertilization (3 and 15 months after the treatment) on the arthropods of Calluna vulgaris heathlands in NW Spain. Three heathland sites were selected with two permanent plots per site: control and fertilized. Ammonium nitrate fertilizer (56kgNha−1 yr−1) was applied monthly and insects were caught using pitfall traps. We found mainly species-level responses to nitrogen addition. Seven species (e.g. Lochmaea suturalis) showed a consistent trend (benefited or harmed) in both periods and were proposed as possible reliable indicators of the effects of nitrogen deposition in these ecosystems. We also found variable arthropod trophic-group responses: (a) herbivores (leaf beetles, true bugs) increased in abundance on a short-term scale; (b) predators (carabid beetles, true bugs) showed opposite and less clear responses in both periods. Further long-term studies are needed to determine the mechanisms underlying the observed arthropod responses. [Copyright &y& Elsevier]

The transfer of 137Cs and 40K from soil to vegetation was studied in an Atlantic blanket bog ecosystem along the Atlantic coast of Ireland where the dominant vegetation is a mixture of Calluna vulgaris, Eriophorum vaginatum and Sphagnum mosses. The impact of soil chemistry and nutritional status of vegetation on the uptake of both radionuclides was also examined. Cesium-137 transfer factors values ranged from 1.9 to 9.6 and accumulation of 137Cs was higher in the leaves of C. vulgaris than in the stems. Transfer factors values for 137Cs in both C. vulgaris and E. vaginatum were similar indicating that for the vegetation studied, uptake is not dependent on plant species. The uptake of 137Cs in bog vegetation was found to be positively correlated with the nutrient status of vegetation, in particular the secondary nutrients, calcium and magnesium. Potassium-40 transfer factors ranged from 0.9 to 13.8 and uptake was higher in E. vaginatum than in C. vulgaris, however, unlike 137Cs, the concentrations of 40K within the leaves and stems of C. vulgaris were similar. The concentration of both 137Cs and 40K found in moss samples were in general lower than those found in vascular plants. [ABSTRACT FROM AUTHOR]

A technique using fresh feeding signs as an index of density was validated and used to survey the effects of sheep grazing on vole population densities in four upland habitats in the northern Peak District National Park, UK. In grazed areas Molinia caerulea grasslands supported most voles, Nardus stricta grasslands supported fewer and Eriophorum vaginatum and Calluna vulgaris-dominated areas supported least. There were highly significant negative relationships between vole sign density and sheep numbers in these habitats. Where sheep were excluded, these same habitats had between three and nine times higher sign densities, corresponding to between 1.5 and 2.5 times greater field vole densities. Population estimates of voles and predators such as short-eared owl approximately doubled under reduced grazing. Reducing sheep numbers in upland areas may therefore be critical in encouraging the recovery of predatory birds in the uplands. [Copyright &y& Elsevier]

Background: Variety protection is of high relevance for the horticultural community and juridical cases have become more frequent in a globalized economy due to essential derivation of varieties. This applies equally to Calluna vulgaris, a vegetatively propagated species from the Ericaceae family that belongs to the top-selling pot plants in Europe. We therefore analyzed the genetic diversity of 74 selected varieties and genotypes of C. vulgaris and 3 of Erica spp. by means of RAPD and iSSR fingerprinting using 168 mono- and polymorphisms. The same data set was utilized to generate a system to reliably identify Essentially Derived Varieties (EDVs) in C. vulgaris, which was adapted from a method suggested for lettuce and barley. This system was developed, validated and used for selected tests of interest in C. vulgaris. Results: As expected following personal communications with breeders, a very small genetic diversity became evident within C. vulgaris when investigated using our molecular methods. Thus, a dendrogram-based assay to detect Essentially Derived Varieties in this species is not suitable, although varieties are propagated vegetatively. In contrast, the system applied in lettuce, which itself applies pairwise comparisons using appropriate reference sets, proved functional with this species. Conclusion: The narrow gene pool detected in C. vulgaris may be the genetic basis for juridical conflicts between breeders. We successfully tested a methodology for identification of Essentially Derived Varieties in highly identical C. vulgaris genotypes and recommend this for future proof of essential derivation in C. vulgaris and other vegetatively propagated crops. [ABSTRACT FROM AUTHOR]

Currently, in operational modelling of NH3 deposition a fixed value of canopy resistance (R c) is generally applied, irrespective of the plant species and NH3 concentration. This study determined the effect of NH3 concentration on deposition processes to individual moorland species. An innovative flux chamber system was used to provide accurate continuous measurements of NH3 deposition to Deschampsia cespitosa (L.) Beauv., Calluna vulgaris (L.) Hull, Eriophorum vaginatum L., Cladonia spp., Sphagnum spp., and Pleurozium schreberi (Brid.) Mitt. Measurements were conducted across a wide range of NH3 concentrations (1–140μgm−3). NH3 concentration directly affects the deposition processes to the vegetation canopy, with R c, and cuticular resistance (R w) increasing with increasing NH3 concentration, for all the species and vegetation communities tested. For example, the R c for C. vulgaris increased from 14sm−1 at 2μgm−3 to 112sm−1 at 80μgm−3. Diurnal variations in NH3 uptake were observed for higher plants, due to stomatal uptake; however, no diurnal variations were shown for non-stomatal plants. R c for C. vulgaris at 80μgm−3 was 66 and 112sm−1 during day and night, respectively. Differences were found in NH3 deposition between plant species and vegetation communities: Sphagnum had the lowest R c (3sm−1 at 2μgm−3 to 23 at 80μgm−3), and D. cespitosa had the highest nighttime value (18sm−1 at 2μgm−3 to 197sm−1 at 80μgm−3). [Copyright &y& Elsevier]

Questions: What effect does sheep grazing have on the nutrient budgets of heathlands? Can grazing compensate for atmospheric nutrient loads in heathland ecosystems? What are the conclusions for heathland management? Location: Lüneburg Heath, NW Germany. Methods: During a one-year grazing experiment (stocking rate 1.1 sheep/ha) nutrient balances for N, Ca, K, Mg and P were calculated by quantifying input rates (atmospheric deposition, sheep excrement) and output rates (biomass removal, leaching).Results: Atmospheric nutrient deposition amounted to 22.8 kg·ha-1·a-1 for N and < 0.2 kg·ha-1·a-1 for P. Sheep excrement increased the inputs for N and P by ca. 3.5 and 0.2 kg·ha-1·a-1, respectively. Grazing reduced N- and P-stores in the above-ground biomass by 25.6 and 1.9 kg·ha-1·a-1, respectively. N- and P-losses via leaching amounted to 2.2 and < 0.2 kg·ha-1·a-1. Output:input ratios for P were high, indicating that grazing severely affected P-budgets of heaths. Conclusions: Our results suggest that sheep grazing has the potential to compensate for atmospheric nutrient loads (particularly for current N deposition rates). However, in the long term the combination of elevated N-deposition and P-loss due to grazing may cause a shift from N-(co-) limited to more P-(co-) limited plant growth. To counteract an aggravation of P-deficiency in the long term, grazing may be combined with management measures that affect P-budgets to a lesser extent (e.g. prescribed burning). [ABSTRACT FROM AUTHOR]

A long-term fertilizer experiment (the Rengen Grassland Experiment, RGE) was established in 1941 in the Eifel Mountains of Germany on low productive grassland naturally dominated by Calluna vulgaris and Nardus stricta. Six treatments combinations of Ca, N, P, and K fertilizer were applied annually: an unfertilized control, Ca, CaN, CaNP, CaNP–KCl, and CaNP–K2SO4. In mid-June 2005, plant cover was visually estimated and sward height was measured aiming to detect changes in floristic composition caused by long-term fertilization. Calculated by redundancy analysis (RDA), the effect of treatment was found to be a significant predictor of sward structure in the experimental area and explained 62% of cover data variability. The largest difference in vegetation structure and composition was between the treatments without and with P application. Briza media was the dominant short grass in the control, Ca, and CaN treatments. Lathyrus linifolius was the dominant legume in the control and Carex panicea was dominant in the CaN treatment. Among treatments with P application, plant species composition was similar with tall grasses such as Alopecurus pratensis, Arrhenatherum elatius, and Trisetum flavescens dominating in the sward. Sward heights were lowest in treatments without P addition in contrast to tall canopies in the P fertilized treatments. Cover of the moss layer was continuously developed in treatments without P application only and was negatively correlated with sward height as was species richness of vascular plants. Long-term fertilization caused significant diversification of plant communities. Species indicative of low productivity grasslands (short grasses, orchids, and sedges) survived in the CaN treatment but not in plots with P or K fertilizer. It was often thought that N enrichment is detrimental to vascular plant richness. [Copyright &y& Elsevier]

Regular grids or lattices are frequently used to study ecosystems, for observations, experiments and simulations. The regular rectangular or square grid is used more often than the hexagonal grid, but their relative merits have been little discussed. Here we compare rectangular and hexagonal grids for ecological applications. We focus on the reasons some researchers have preferred hexagonal grids and methods to facilitate the use of hexagonal grids. We consider modelling and other applications, including the role of nearest neighbourhood in experimental design, the representation of connectivity in maps, and a new method for performing field surveys using hexagonal grids, which was demonstrated on montane heath vegetation. The rectangular grid is generally preferred because of its symmetrical, orthogonal co-ordinate system and the frequent use of rasters from Geographic Information Systems. Cells in a rectangular grid can also easily be combined to produce new grids with lower resolutions. However, efficient co-ordinate systems and multi-resolution partitions using the hexagonal grid are available. The nearest neighbourhood in a hexagonal grid is simpler and less ambiguous than in a rectangular grid. When nearest neighbourhood, movement paths or connectivity are important, the rectangular grid may not be suitable. We also investigate important differences between visualizations using hexagonal and rectangular grids. A survey of recent uses of grids in Ecological Modelling suggested that hexagonal grids are rarely used, even in applications for which they are more suitable than rectangular grids, e.g. connectivity and movement paths. Researchers should consider their choice of grid at an early stage in project development, and authors should explain the reasons for their choices. [Copyright &y& Elsevier]

On an upland moor dominated by pioneer Calluna vulgaris and with an understorey of mosses and lichens, experimental plots were treated with factorial combinations of nitrogen (N) at +0 and +20kg Nha−1 yr−1, and phosphorus (P) at +0 and +5kg Pha−1 yr−1. Over the 4-year duration of the experiment, the cover of the Calluna canopy increased in density over time as part of normal phenological development. Moss cover increased initially in response to N addition but then remained static; increases in cover in response to P addition became stronger over time, eventually causing reductions in the cover of the dominant Calluna canopy. Lichen cover virtually disappeared within 4 years in plots receiving +20kg Nha−1 yr−1 and also in separate plots receiving +10kg Nha−1 yr−1, but this effect was reversed by the addition of P. [Copyright &y& Elsevier]

We measured net ecosystem CO2 flux ( F n) and ecosystem respiration ( R E), and estimated gross ecosystem photosynthesis ( P g) by difference, for two years in a temperate heath ecosystem using a chamber method. The exchange rates of carbon were high and of similar magnitude as for productive forest ecosystems with a net ecosystem carbon gain during the second year of 293 ± 11 g C m−2 year−1 showing that the carbon sink strength of heather-dominated ecosystems may be considerable when C. vulgaris is in the building phase of its life cycle. The estimated gross ecosystem photosynthesis and ecosystem respiration from October to March was 22% and 30% of annual flux, respectively, suggesting that both cold-season carbon gain and loss were important in the annual carbon cycle of the ecosystem. Model fit of R E of a classic, first-order exponential equation related to temperature (second year; R 2 = 0.65) was improved when the P g rate was incorporated into the model (second year; R 2 = 0.79), suggesting that daytime R E increased with increasing photosynthesis. Furthermore, the temperature sensitivity of R E decreased from apparent Q 10 values of 3.3 to 3.9 by the classic equation to a more realistic Q 10 of 2.5 by the modified model. The model introduces R photo, which describes the part of respiration being tightly coupled to the photosynthetic rate. It makes up 5% of the assimilated carbon dioxide flux at 0°C and 35% at 20°C implying a high sensitivity of respiration to photosynthesis during summer. The simple model provides an easily applied, non-intrusive tool for investigating seasonal trends in the relationship between ecosystem carbon sequestration and respiration. [ABSTRACT FROM AUTHOR]

1. World-wide, the controlled use of fire is an important ecological management tool and is essential for the continuance of many communities. It is used extensively in upland regions of England to maintain dwarf shrub habitats for game-bird rearing. Inappropriate burning, however, is now cited as the second most important reason for the poor condition of conservation sites in these areas. Despite this there are few data on the extent and frequency of its use to help judge its potential impact on biodiversity. 2. This study, using aerial photography of a 2% sample (208 km2) of the English uplands, surveyed the national scale of fire management for the first time, and used historical photography to identify medium-term trends in its use. 3. Management burning in the English uplands is now widespread on ericaceous-dominated moorland; in the year 2000 17% of the area of this habitat had been burned within the previous 4 years, equivalent to 114 km2 year−1. The present median burn repeat time of consistently managed sites is approximately 20 years. 4. Within most of the English national parks there has been a significant increase in the extent of new burns (from 15·1% to 29·7%) over this period, indicating an intensification of burning regimes in some areas. 5. Synthesis and applications. The extent and frequency of burning, and the habitats in which this management occurs, are contentious issues. Reconciling the differing objectives of conservation, game rearing and agricultural stakeholders to allow the development of both strategic and local management planning to address these issues requires information on the extent and history of burning practices. This study provides a much needed first national estimate of burning practices in England and serves as a baseline against which changes in management regimes and their impacts on habitats can be judged. [ABSTRACT FROM AUTHOR]

The article presents abstracts of several studies on environmental geochemistry. Some of the abstracts presented include "Biogeochemical Cycling of Nutrients in Karstic Catchments, Southwestern China: Linkages to Changes of Eco-Environments," by Congqiang Liu and "Emerging Organic Contamination in China," by Guibin Jiang and colleagues.

Atmospheric deposition of nitrogen is responsible for widespread changes in the structure and function of sensitive seminatural ecosystems. The proposed reduction in emissions of nitrogenous pollutants in Europe under the Gothenburg Protocol raises the question of whether affected ecosystems have the potential to recover to their previous condition and, if so, over what timescale. Since 1998, we have monitored the response of a lowland heathland in southern England following the cessation of a long-term nitrogen addition experiment, and subsequent management, assessing changes in vegetation growth and chemistry, soil chemistry and the soil microbial community. Persistent effects of earlier nutrient loading on Calluna growth and phenology, and on the abundance of lichens, were apparent up to 8 years after nitrogen additions ceased, indicating the potential for long-term effects of modest nutrient loading (up to 15.4 kg N ha−1 yr−1, over 7 years) on heathland ecosystems. The size and activity of the soil microbial community was elevated in former N-treated plots, 6–8 years after additions ceased, suggesting a prolonged effect on the rate of nutrient cycling. Although habitat management in 1998 reduced nitrogen stores in plant biomass, effects on belowground nitrogen stores were small. Although some parameters (e.g. soil pH) recover pretreatment levels relatively rapidly, others (e.g. vegetation cover and microbial activity) respond much more slowly, indicating that the ecological effects of even small increases in nitrogen deposition will persist for many years after deposition inputs are reduced. Indeed, calculations suggest that the additional soil nitrogen storage associated with 7 years of experimental nitrogen inputs could sustain the observed effects on plant growth and phenology for several decades. Carry over effects on plant phenology and sensitivity to drought suggest that the persistence of vegetation responses to nitrogen deposition should be integrated into long-term assessments of the impact of global climate change on sensitive ecosystems. [ABSTRACT FROM AUTHOR]

Abstract: Across large areas of upland Britain Molinia caerulea and Nardus stricta are replacing Calluna vulgaris as the dominant plant species of the vegetation assemblage. Associated changes in the composition of the whole plant assemblage and a phytophagous insect group, the Hemiptera, were investigated. Vegetation and hemipteran assemblages were sampled at six moorland sites in northern England and Scotland. Sampling at each site was carried out in Calluna vulgaris-dominated areas and grass-dominated areas that had previously been dominated by C. vulgaris. Vegetation assemblages of heath and grass sites differed significantly even when species by which sites were selected for sampling (C. vulgaris, M. caerulea and N. stricta) were removed from the analysis with the highest species richness in dry grassland sites. Hemipteran assemblages differed significantly between heath and grass sites with greater species richness also being in grass sites. Plant species composition was the most important explanatory variable of hemipteran assemblages with temperature, latitude, soil loss on ignition and vegetation height also explaining a significant proportion of the variation. Overall a range of vegetation composition and structural variables explained 40.8% of variation in the Hemiptera species data with ranges of soil and biogeographic variables explaining an additional 8.7%. This research demonstrates that the replacement of one dominant plant species by another is associated with a change in other aspects of moorland biodiversity. In particular the loss of C. vulgaris actually leads to an increase in the species richness of Hemiptera and plants although the number of specialist species declines. [Copyright &y& Elsevier]

Abstract: Ericoid mycorrhizal fungi are symbiotically associated with the roots of members of the Ericaceae which include genera such as Calluna, Epacris, Erica, Rhododendron and Vaccinium. These ericoid mycorrhizal associations have adapted to a broad range of habitats, from mor humus soils of the northern hemisphere to sandy soils occurring in the southern hemisphere. They also play an important part in enabling plants like Calluna vulgaris (L.) Hull in the northern hemisphere to colonize mine spoils which are inhospitable environments of toxic waste for growth of most plants. The mechanisms of utilizing complex forms of nitrogen and phosphorus and providing protection against toxic metals are described. These mechanisms carried out by ericoid mycorrhizal associations enable host plants to establish in diverse habitats. [Copyright &y& Elsevier]

Abstract: The %N and δ 15N signals in foliar nitrogen (N) from four heathland species have been monitored in a blanket bog plant community subjected to different experimental inputs of wet and dry N deposition. Interactions with combined additional treatments of phosphorus (P) and potassium (K) were also investigated. Calluna vulgaris, Cladonia portentosa, Sphagnum capillifolium and Hypnum cupressiforme were harvested for 15N analysis prior to wet and dry treatment applications and again after 16 months field exposure. A significant increase was observed in both %N and δ 15N values for all plant species in response to both wet and dry treatments whilst PK additions also produced significant decreases in foliar %N and associated δ 15N values for several of the species sampled. These enrichments in the δ 15N signals for post-treatment shoot tissue were attributable to the δ 15N signal in the source application, a finding of potential value in using bio-monitors for assessment of N deposition. [Copyright &y& Elsevier]

Abstract: Ring diameters and ring number counts were recorded from Calluna stem cross-sections harvested during an N manipulation experiment. The application of dendrochronological methods permitted accurate ageing of shrubs growing in a heathland of known age. Linear regression analyses demonstrated a highly significant association between increasing levels of N input and stem diameter in both watered and droughted plots (droughted in 1997 only). N inputs were identified as the most significant environmental stressor, appearing to speed ageing vis the Calluna growth cycle. Drought sensitivity was noted in the high N treatment plots (120kgNha−1 yr−1) with decreased stem diameters. This may have implications in the response of Calluna growth under current climate change scenarios. [Copyright &y& Elsevier]

Bracken ( Pteridium aquilinum) is a major weed of seminatural vegetation in Great Britain, as in many other countries. As a consequence, large areas have been subject to control with the intention of restoring the former vegetation. The use of aerial spraying with asulam, a narrow spectrum, carbamate herbicide, has become a common method of control. However, its long-term efficacy has not been assessed in terms of either controlling the bracken or in producing suitable restored habitats. This study undertook such an assessment by comparing the results of a 2002 survey of the sites subject to bracken control by aerial spraying of asulam with previous (1990/1991 and 1994) surveys of the same sites. This showed that a single application of asulam was effective in eradicating bracken (<1% cover remaining) on a third of sites. However, on 10% of the sites, the bracken had regenerated completely (cover >80%) and on the remainder it was still present in patches (>20% of quadrats), often at high density. More than half the sprayed sites had seen good recovery of moorland vegetation, the target of the restoration, because they were now classified as having upland heathland vegetation within the National Vegetation Classification. Considerable amounts of bracken control are grant aided as part of agri-environment schemes. These schemes should be adapted to encourage good practice, namely, intensive follow-up treatment by spraying any emerging fronds, and to encourage treatment of previously sprayed areas rather than spraying of new areas in order to protect previous investment of grant aid. [ABSTRACT FROM AUTHOR]

The article discusses the effects of fire on population growth rate and invasive spread of the perennial tussock grass Molinia caerulea. This species has extensively invaded heathland communities in Western Europe. It has displaced typical heathland species including Calluna vulgaris and Erica tetralix. Molinia caerulea is a deciduous grass species that produces large amounts of litter each year. It is considered a huge threat to heathland conservation. Monalina caerulea is a deciduous grass species that produces large amounts of litter each year. It is considered a major threat to heathland conservation. In 1996, an unintended fire destroyed one-third of a large heathland area in northern Belgium. Permanent monitoring plots were established to study the impact of this fire on the population dynamics and invasive spread of Molinia caerulea. A life table response experiment analysis revealed that the effect of fire was mainly contributed by increases in seed production and germination. The analysis showed increased invasive spread of Molinia caerulea after fire.

1 Experimental studies of the combined effects of herbivory and the availability of nutrients on semi-natural communities remain relatively scarce. Here we report the effects of 6 years of nutrient addition (N, P and K) and protection from grazing on moorland plant communities in the Scottish uplands, particularly on the cover of the dominant Calluna vulgaris. We also recorded the cover of vascular plants and bryophytes, to assess the impact of changes in Calluna dominance on competing species. 2 Grazing in combination with nitrogen addition caused the greatest decline in Calluna cover, typically 40–50%, but nitrogen addition did not cause a significant decline in Calluna on plots protected from grazing. More Calluna shoots were browsed on nitrogen-treated plots than on unfertilized ones, presumably because grazing animals preferred fertilized Calluna. 3 Nitrogen addition allowed grasses to increase in cover, especially on grazed plots. However, Nardus stricta, Festuca ovina and Agrostis sp. all declined in fenced areas but increased in grazed plots, whereas Deschampsia flexuosa and Festuca rubra increased in fenced plots. 4 The effects of grazing and nutrient addition varied markedly between sites, possibly because of differences in soil moisture and organic matter. Nitrogen addition, however, increased soil nitrogen mineralization rates in both glens. 5 Fencing increased the cover of grazing-intolerant plants with low nutrient demands (as classified by Ellenberg and suited species scores) that were categorized as competitive plants by Grime's CSR model. Plots receiving nitrogen and phosphorus had more nutrient-demanding plants able to tolerate high grazing pressure that were often classified as ruderals. 6 The impact of nitrogen addition on the cover of Calluna and on competing grass species in the community critically depends on the level of grazing. Changes in community composition caused by grazing and fertilizer addition can be explained in terms of the ecological tolerances of individual species, allowing us to predict the types of plants that are likely to increase or decrease in cover. [ABSTRACT FROM AUTHOR]

Abstract: A key management objective for native Scots pine (Pinus sylvestris) forests in Scotland is to extend the forest onto treeless moorland, below the natural tree line, dominated by the dwarf shrub, heather (Calluna vulgaris). At Abernethy Forest, Scotland''s largest native pinewood remnant, establishment of new tree seedlings on moorland has recently slowed despite the low grazing pressure. To investigate whether fire would be a useful management tool to improve the rate of regeneration of Scots pine, an experiment was carried out in 10 plots, on open moorland, on shallow peat soil, c 300m from the forest edge. At each plot, 10 small exclosures were established, two for each of four burning treatments, and two controls. Within each exclosure, 100 Scots pine seeds were sown and the numbers of seedlings resulting were counted after 2, 11 and 30 months. Exclosures substantially reduced seed and seedling predation by mammals and invertebrates. The four burning treatments were single and double burns in the year of sowing, and single and double burns 1 year before sowing. Single burns removed largely heather, whilst second burns removed more of the moss. Burnt areas had 3.5 times (95% confidence limits 1.5–8.1) the number of seedlings established as controls, 2 months after sowing. There was no significant additional effect on seedling numbers of either double burning or year of burn. Slower-moving fires and, to some extent, shallower post-fire moss/litter depths, were associated with more seedlings establishing. Seedling numbers declined by 18% between months 2 and 11 and by 27% between months 11 and 30. The pattern of these declines was not significantly affected by treatment, post-fire moss/litter depth, or fire characteristics. The results have wide application at sites where Scots pine regeneration is a management aim, particularly on heather moorland, and where techniques which mimic natural processes are preferred. Managers at such sites should include prescribed burning, in conditions that produce slow-moving fires and shallow post-fire moss/litter depths, as a management option for improved Scots pine seedling establishment. [Copyright &y& Elsevier]

Questions: How does Calluna vulgaris regenerate after burning wet and dry heaths of different age? Location: Central Norway. Methods: Patches of Calluna dominated old and young wet heath and old dry heath were burned. The mean temperatures reached in the categories of heath were measured. Cover, frequency, height and number of seedlings of Calluna were studied in plots. Results: The mean burning temperatures varied from 680 to 740 °C, and were highest in wet heath that had not been burned for at least 50 years. Regeneration of Calluna was evident in the year of burning, but only from seeds. Even heath with a short burning interval lacked vegetative regeneration. Calluna cover increased yearly and exceeded 50 % three years after burning. Regeneration was evident in the year of burning, and was highest in heath with a short burning interval. The height increased regularly at all sites, but was most rapid in dry heath, probably because of better microclimatic conditions. There were more seedlings in the heath with a short burning interval. Conclusions: Calluna only regenerates from seeds after burning in central Norway. The density of Calluna increased rapidly, which is positive for the conservation and management of coastal heaths in central Norway. [ABSTRACT FROM AUTHOR]

A field ammonia (NH3) release experiment and open top chambers containing moorland monoliths continuously fumigated with NH3 or sprayed with NH4Cl were used to assess the potential for using d15N values in determining the area of influence around a point NH3 emission source. d15N values are being increasingly used as environmental tracers and we tested the hypothesis that the d15N signal from an NH3 emission source is observable in nearby vegetation. Using modified monitoring devices, atmospheric NH3 concentrations were found to decrease with distance from source, with d15N values also reflecting this trend, producing a signal shift with changing concentration. Open top chamber studies of d15N values ofCalluna vulgaris(L.) Hull indicated a correlation with deposition treatments in current year shoots. Analysis ofCallunashoots from the NH3 release showed a similar trend of d15N enrichment. Significant linear correlations between d15N and percent N in plant material were found, both in the controlled conditions of the open top chambers and at the NH3 release site, illustrating the possible use of this technique in N deposition biomonitoring. [ABSTRACT FROM AUTHOR]

The UK Biodiversity Action Plan has identified the creation of lowland heathland as an important objective. Heathland restoration studies have identified soil pH, elevated soil nutrients and large weed seed banks as major problems in the restoration of heathland vegetation on ex-arable land. Heathland vegetation is usually found on nutrient-poor acidic soils. Creating acidic soil conditions on ex-arable sites thus may produce a suitable environment for the establishment of heath vegetation. Soil acidification by the addition of sulphur has been shown to reduce the soil pH and the availability of nutrients in arable soils. A series of experiments was established to investigate the effects of soil acidification using sulphur on the establishment of Calluna vulgaris and the development of weed vegetation. The application of sulphur at 0.24 kg m-2 to an arable soil was found to increase the survival rate of C. vulgaris cuttings planted in it. The mechanism of increased C. vulgaris survival appeared to be by sulphur application significantly reducing the cover of arable weeds arising from the soil seed bank. Higher rates of sulphur application (0.36 and 0.48 kg m-2) resulted in the death of many C. vulgaris plants. However C. vulgaris seedlings were able to establish successfully on these ex-arable soils within 18–24 months following the addition of these levels of sulphur. The application of sulphur appears to offer a practical solution to heathland creation on ex-arable land. However, it may be necessary to provide an interval of between 18 and 24 months between the application of sulphur and the addition of C. vulgaris plants or seeds for the successful establishment of heathland vegetation. [Copyright &y& Elsevier]

A palaeoecological investigation in the Bodø area (Salten, Nordland) records a shift from Betula -dominated forest to mostly treeless vegetation during the last 4000 years. Corylus avellana , now at its northern limits in this region, was previously more abundant within the area. Deforestation started c. 3500-3000 BP, most likely connected to human activity during the early Bronze Age. After the onset of anthropogenic disturbance, heathland was established, initially with a dominance of Calluna vulgaris and Empetrum . Later on, c. 900 BP, Calluna was dominant. The heathland was probably subject to management, including burning. It should be viewed as a part of a northern extension of the western European heathland vegetation of the coast of SW Norway. [ABSTRACT FROM AUTHOR]

Studies were conducted to examine the host range of a select isolate of the ericoid mycorrhizal fungus Hymenoscyphus ericae (Read) Korf and Kernan [American Type Culture Collection (ATCC) #32985]. Host status was tested for 15 ericaceous species, including: Calluna vulgaris (L.) Hull, Enkianthus campanulatus (Miq.) Nichols, Gaultheria procumbens L., Kalmia latifolia L., Leucothoe fontanesiana Sleum., Oxydendrum arboreum (L.) DC., Pierisfioribunda (Pursh) Benth. & Hook., Rhododendron calendulaceum (Michx.) Torn, Rhododendron carolinianum Rehd., Rhododendron catawbiense Michx., Rhododendron maximum L., Rhododendron mucronulatum Turcz., Vaccinium corymbosum L., and Vaccinium macrocarpon Ait. Arbutus unedo L., an ericaceous species that forms arbutoid, not ericoid, mycorrhizae, was used as a negative control. All of the species were colonized by the ericoid isolate with the exception of Enkianthus campanulatus and the negative control. Inoculation with this isolate of H. ericae resulted in a significant increase in shoot growth. However, intensity of root colonization was not correlated to amount of shoot growth. In fact, an increase in growth was observed in the two species that lacked fungal colonization. [ABSTRACT FROM AUTHOR]