Predicting effects of N pollutant load on plant species based on a dynamic soil eutrophication indicator. Final report on Nitrogen Effects on Dune Species (NEDS) project

The effects of nitrogen (N) pollution on dune grassland were explored using a model chain that predicts how plant species are likely to respond to changes in soil chemistry. The model chain was calibrated to data from an N addition and grazing experiment at Newborough in Anglesey. The N14C soil model predicted increases in plant productivity and plant litter carbon (C) inputs with more N addition, resulting in an initial and persistent increase in soil C/N ratio. This contrasts with predictions of decreasing C/N ratio from the simpler N saturation model currently used to calculate nutrient-N critical load exceedance. All N addition rates also caused persistent increases in plant-available N. Using the MultiMOVE niche models for plant species typical of dune grassland, these soil changes were related to changes in the overall nutrient enrichment of the flora, as indicated by mean Ellenberg N score, and thereby to the habitat’s suitability for particular species. Declines in Habitat Suitability were interpreted as increasing risk to the species. At rates above 30 kg N ha-1y-1, the more sensitive species were placed at risk almost immediately, but at smaller rates species were placed at risk later on, with an increasing delay with less N addition. At rates lower than the critical N load for calcareous fixed dunes, more mesotrophic species were placed at risk. Species viewed as positive indicators of habitat condition were placed at risk under both high and low rates of N addition. Changes in Habitat Suitability due to changed grazing regime had greater simulated effects on Habitat Suitability. For more confidence in the model chain, differences between the spatial and temporal effects of N addition need to be addressed. More information on the effects of N on vegetation structure and litterfall would be very useful, and objective measurements of vegetation height should be included in monitoring schemes alongside floristic recording. Management was shown to be critical for mitigating the effects of N. Although N removal through grazing or mowing is unlikely to export sufficient N to prevent enrichment, reducing vegetation height can prevent competitive species shading out the more distinctive low-growing, light-demanding dune species

Ecohydrological conditions at Braunton Burrows : activities to date including work supported by BGS Opportunity Funds FY 2011/2012

Ongoing investigation of the ecohydrological conditions at four west coast dunefields (Ainsdale, Newborough Warren, Whiteford Burrows and Braunton Burrows) has recently been focused at Braunton in North Devon. BGS Opportunity Funds, coupled with the acquisition by CEH of a pneumatic portable auger, has enabled investigation and sampling from cores taken from ‘deep’ boreholes beneath the high dunes at Braunton along the existing Sandy Lane Shore Slack transect. Work has previously focused on the slack floors and the shallow water table beneath them. Analyses of chemistry, stable isotopes, SF6, as well as grain size and falling head permeability will, in due course, enable a better understanding of groundwater provenance in the dune fields and of the recharge processes away from the dune slack floors. Preliminary results are described. Further data are still awaited and will be incorporated in a future report. A way forward is described which will deliver peer reviewed papers on the deep drilling work at Braunton, a paper on work at Whiteford and detailed investigation funded largely by Natural England and CEH at four new sites. These sites are likely to include two acid coastal dunes on the North Sea Coast, which will contrast with the alkaline sites on the west coast, one in Cumbria and one elsewhere

Nitrogen mediates above-ground effects of ozone but not below-ground effects in a rhizomatous sedge

Ozone and atmospheric nitrogen are co-occurring pollutants with adverse effects on natural grassland vegetation. Plants of the rhizomatous sedge Carex arenaria were exposed to four ozone regimes representing increasing background concentrations (background-peak): 10–30, 35–55, 60–80 and 85–105 ppb ozone at two nitrogen levels: 12 and 100 kg N ha−1 yr−1. Ozone increased the number and proportion of senesced leaves, but not overall leaf number. There was a clear nitrogen × ozone interaction with high nitrogen reducing proportional senescence in each treatment and increasing the ozone dose (AOT40) at which enhanced senescence occurred. Ozone reduced total biomass due to significant effects on root biomass. There were no interactive effects on shoot:root ratio. Rhizome tissue N content was increased by both nitrogen and ozone. Results suggest that nitrogen mediates above-ground impacts of ozone but not impacts on below-ground resource translocation. This may lead to complex interactive effects between the two pollutants on natural vegetation

Changes in landscape and vegetation of coastal dunes in northwest Europe: a review

In coastal dunes, landscape changes are a rule, rather than an exception. This paper gives an overview of changes in landscape and vegetation with a focus on the past century. The history of dunes is characterised by phases of sand drift, alternated with geomorphological stability. The historical development of dune woodland during these stable phases has been documented for sites all over Europe. Vegetation reconstructions of historical open dune habitats however is very difficult due to limited preservation of fossil remains. People have drastically altered coastal dune landscapes through centuries of exploitation and more recently development of the coast. Historical land use has generally pushed vegetation back into a semi-natural state. During roughly the past century a tendency of increasing fixation and succession is observed on coastal dunes throughout northwest Europe. Six causes of change are discussed. 1) Changes in land use, mainly abandonment of agricultural practices, have led to the development of late successional stages such as scrub and woodland. 2) Crashing rabbit populations due to myxomatosis in the 1950s caused vigorous grass growth and probably stimulated scrub development. 3) A general tendency of landscape fixation is observed due to both natural and anthropogenic factors. 4) Eutrophication, mainly due to atmospheric nitrogen deposition is clearly linked to grass encroachment on acidic but also on some calcareous dunes. 5) The impact of climate change on vegetation is still unclear but probably lengthening of growing season and maybe enhanced CO2 concentrations have led to an acceleration of succession. 6) A general anthropogenisation of the landscape occurs with rapid spread of non-native species as an important consequence. The reconstruction of a natural reference landscape is considered largely unattainable because of irreversible changes and the long tradition of human impact, in many cases since the development of the dunes. Two contradictory elements need reconciliation. First, the general acceleration of succession and scrub and woodland development in particular is partly caused by a decreased anthropogenic interference in the landscape and deserves more appreciation. Second, most biodiversity values are largely linked to open, early succession dune habitats and are threatened by the same tendency. Apart from internal nature management, in which grazing plays an important part, re-mobilisation of stable, senescent dunes is an important challenge for dune management

Identifying ozone-sensitive communities of (semi-)natural vegetation suitable for mapping exceedance of critical levels

Using published data on the responses of individual species to ozone, 54 EUNIS (European Nature Information System) level 4 communities with six or more ozone-sensitive species (%OS) and c. 20% or more species tested for ozone sensitivity, were identified as potentially ozone-sensitive. The largest number of these communities (23) was associated with Grasslands, with Heathland, scrub and tundra, and Mires, bogs and fens having the next highest representation at 11 and 8 level 4 communities each respectively. Within the grasslands classification, E4 (Alpine and sub-alpine grasslands), E5 (Woodland fringes and clearings) and E1 (Dry grasslands) were the most sensitive with 68.1, 51.6 and 48.6%OS respectively. It is feasible to map the land-cover for these and other communities at level 2, but it may not be currently possible to map the land-cover for all communities identified to be ozone-sensitive at levels 3 and 4. Grassland communities such as alpine and sub-alpine grasslands have the highest potential sensitivity ozone, based on the responses of their component species

Meta-analysis of the relative sensitivity of semi-natural vegetation species to ozone

This study identified 83 species from existing publications suitable for inclusion in a database of sensitivity of species to ozone (OZOVEG database). An index, the relative sensitivity to ozone, was calculated for each species based on changes in biomass in order to test for species traits associated with ozone sensitivity. Meta-analysis of the ozone sensitivity data showed a wide inter-specific range in response to ozone. Some relationships in comparison to plant physiological and ecological characteristics were identified. Plants of the therophyte lifeform were particularly sensitive to ozone. Species with higher mature leaf N concentration were more sensitive to ozone than those with lower leaf N concentration. Some relationships between relative sensitivity to ozone and Ellenberg habitat requirements were also identified. In contrast, no relationships between relative sensitivity to ozone and mature leaf P concentration, Grime's CSR strategy, leaf longevity, flowering season, stomatal density and maximum altitude were found. The relative sensitivity of species and relationships with plant characteristics identified in this study could be used to predict sensitivity to ozone of untested species and communities