Are Calcareous Grasslands in the UK under Threat from Nitrogen Deposition?--An Experimental Determination of a Critical Load

Wilson, E. J.; Wells, T. C. E.; Sparks, Tim H.

doi:10.2307/2261419

Cited by 80 publications

(45 citation statements)

References 11 publications

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“…sites on steep south-facing slopes with thin soils) was maintained, even under increased levels of atmospheric N deposition, because such grasslands were co-limited both by phosphorus and by water to a much greater extent than N (see also Carroll et al 2003;Phoenix et al 2003;Maskell et al 2010). They went on to hypothesise that the composition of calcareous grassland was more likely to be affected negatively by changes to management and land use, a view shared by both Wilson et al (1995) and Jacquemyn et al (2003) who found no and minimal effects, respectively, relating to N deposition, with grazing management viewed as the primary means of regulating the composition and diversity of chalk grassland. Van den Berg et al (2011) found no correlation between N deposition and a change in Ellenberg N values, but did find that a decrease in grazing pressure was significantly negatively correlated to a change in diversity (see also Walker et al 2009).…”

Section: Species Richnessmentioning

confidence: 99%

Long-term changes in lowland calcareous grassland plots using Tephroseris integrifolia subsp. integrifolia as an indicator species

2017

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We investigated the changes to calcareous grassland plots within protected sites, and whether Tephroseris integrifolia subsp. integrifolia can act as a useful indicator species for re-visitation studies within vegetation predicted to remain relatively stable. Twenty-two plots located across lowland England and all formerly containing T. integrifolia were resurveyed following the methodology used in the original survey undertaken in the 1960s. Pseudoturnover and between-observer bias were minimised by sampling replicate quadrats at each fixed plot using a single surveyor and at a similar time of year as the original survey. Qualitative details concerning grazing management were obtained for all sites. In contrast to other long-term re-visitation studies, all our study plots were intact and retained diverse, herb-rich vegetation, demonstrating the value of site protection. However, there were clear shifts in vegetation composition, most notably where T. integrifolia was absent, as shown by an increase in Ellenberg fertility and moisture signifying nutrient enrichment, and a decrease in the cover of low-growing, light-demanding specialists, with a change likely to be associated predominantly with grazing management. Whereas in the mid-20th century the greatest threat to calcareous grassland was habitat loss, undergrazing or temporary neglect now appears to pose the principal threat. Distinctive species such as T. integrifolia with marked sensitivity to habitat change provide a potentially useful tool for rapid assessment and monitoring of site quality. Focusing monitoring on such species allows non-expert observers to recognise the early stages of habitat degradation, providing, in effect, a ''health check'' on individual sites and groups of sites.

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Section: Species Richnessmentioning

confidence: 99%

Long-term changes in lowland calcareous grassland plots using Tephroseris integrifolia subsp. integrifolia as an indicator species

2017

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“…As an example, this has been suggested as a partial cause of the spread and increasing dominance by Brachypodium pinnatum in calcareous grasslands (Bobbink et al 1998), although the magnitude of such impacts varies geographically (Wilson et al 1995). Several rare leafhoppers are monophagous on this plant species (e.g.…”

Section: Habitat Change and Land Usementioning

confidence: 99%

Conservation of Grassland Leafhoppers: A Brief Review

et al. 2005

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The leafhoppers, planthoppers and their allies (collectively known as the Auchenorrhyncha) are presented as a group of insects that are highly appropriate for studying grassland ecology and conservation, evaluating the conservation status of sites and monitoring environmental and habitat change. Semi-natural grasslands typically support dense populations and a wide range of species with diverse ecological strategies. Their numerical dominance in many grasslands means that they have considerable functional significance, both as herbivores and as prey for higher trophic levels. Population and assemblage studies are supported by good ecological knowledge about most species and modern identification keys. Hitherto, most studies have focused on the composition and structure of assemblages and how they are affected by conservation management. However, grasslands support many rare species with small and fragmented populations which deserve conservation attention in their own right, and recent work has started to reflect this. The effects of management on the composition and structure of grassland leafhopper populations and assemblages are described and an assessment is given of the main threats facing individual species and overall diversity. There is a need to synthesise the scattered literature on grassland leafhoppers, to provide a model for how the composition and structure of populations and assemblages respond to major environmental and anthropogenic gradients across large biogeographic areas. Such an analysis could help predict the impact of likely future changes in land use and climate.

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“…Several authors have concluded that phosphorus limitation in calcareous soils often prevents a short-term response to nitrogen addition (Morecroft et al . 1994;Wilson et al . 1995;Grime et al .…”

Section: Introductionmentioning

confidence: 99%

Influence of slope and aspect on long‐term vegetation change in British chalk grasslands

Bennie¹,

Hill²,

Baxter³

et al. 2006

Journal of Ecology

302

232

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Summary 1The species composition of fragmented semi-natural grasslands may change over time due to stochastic local extinction and colonization events, successional change and/or as a response to changing management or abiotic conditions. The resistance of vegetation to change may be mediated through the effects of topography (slope and aspect) on soils and microclimate. 2 To assess long-term vegetation change in British chalk grasslands, 92 plots first surveyed by F. H. Perring in 1952-53, and distributed across four climatic regions, were re-surveyed during 2001-03. Changes in vegetation since the original survey were assessed by comparing local colonization and extinction rates at the plot scale, and changes in species frequency at the subplot scale. Vegetation change was quantified using indirect ordination (Detrended Correspondence Analysis; DCA) and Ellenberg indicator values. 3 Across all four regions, there was a significant decrease in species number and a marked decline in stress-tolerant species typical of species-rich calcareous grasslands, both in terms of decreased plot occupancy and decreased frequency within occupied plots. More competitive species typical of mesotrophic grasslands had colonized plots they had not previously occupied, but had not increased significantly in frequency within occupied plots. 4 A significant increase in Ellenberg fertility values, which was highly correlated with the first DCA axis, was found across all regions. The magnitude of change of fertility and moisture values was found to decrease with angle of slope and with a topographic solar radiation index derived from slope and aspect. 5 The observed shift from calcareous grassland towards more mesotrophic grassland communities is consistent with the predicted effects of both habitat fragmentation and nutrient enrichment. It is hypothesized that chalk grassland swards on steeply sloping ground are more resistant to invasion by competitive grass species than those on flatter sites due to phosphorus limitation in shallow minerogenic rendzina soils, and that those with a southerly aspect are more resistant due to increased magnitude and frequency of drought events.

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Are Calcareous Grasslands in the UK under Threat from Nitrogen Deposition?--An Experimental Determination of a Critical Load

Cited by 80 publications

References 11 publications

Long-term changes in lowland calcareous grassland plots using Tephroseris integrifolia subsp. integrifolia as an indicator species

Long-term changes in lowland calcareous grassland plots using Tephroseris integrifolia subsp. integrifolia as an indicator species

Conservation of Grassland Leafhoppers: A Brief Review

Influence of slope and aspect on long‐term vegetation change in British chalk grasslands

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