The interactions between plant growth, vegetation structure and soil processes in semi-natural acidic and calcareous grasslands receiving long-term inputs of simulated pollutant nitrogen deposition

Nitrogen and phosphorus co-limitation and grazing moderate nitrogen impacts on plant growth and nutrient cycling in sand dune grassland

“…While many bryophytes are highly sensitive to N, the increase in bryophyte biomass here is not surprising as responses are species-specific (Armitage et al, 2012). However, experiments applying much higher loadings of N in calcareous grasslands, low nutrient fens and ombrotrophic bogs have shown a decline in moss cover and an increase in vascular plants, particularly graminoid cover (Carroll et al 2003;Cusell et al, 2014;Wu and Blodau, 2015).…”

“…The similar lack of response in the P treatment, combined with significant responses observed only in the 14 combined NP treatment strongly suggests this dune grassland is NP co-limited. Other low nutrient grasslands have shown a degree of NP co-limitation, with significantly greater above-ground biomass in NP treatments than in the control or with addition of N or P separately (Willems et al, 1993;Carroll et al, 2003). Across grasslands globally NP colimitation is widespread (Elser et al, 2007;Bracken et al, 2015;Fay et al, 2015).…”

“…In addition to plant composition change, N addition can also alter plant available N, nutrient cycling and soil pH (Phoenix et al, 2012) leading to further changes in ecosystem functioning. Phosphorus (P) limitation is common in many semi-natural grassland soils, especially calcareous grasslands (Willems et al, 1993;Carroll et al, 2003;Vitousek et al, 2010) where P availability is partly determined by soil pH, forming complexes with calcium at high pH (Kooijman and Besse, 2002). As a result, plant growth may be limited by P supply (Jeffrey and Pigott, 1973;Morecroft et al, 1994;van den Berg et al, 2005), thereby reducing some of the negative impacts of N deposition mediated through above-ground competition for light (Ten Harkel and van der Meulen, 1996;Vitousek et al, 2010).…”

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

“…In a long-term study of calcareous grasslands in Germany, Diekmann et al (2014) showed that species richness on grassland sites with a low natural supply of N (e.g. 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.…”

Potential Approaches to Developing Lichen-Based Critical Loads and Levels for Nitrogen, Sulfur and Metal-Containing Atmospheric Pollutants in North America

“…Within the first 4 years, they did not observe a significant decline in species composition of vascular plants caused by nitrogen. From the sixth year on, there has been a marked and significant dose-related decline in vascular plant cover with increased nitrogen addition (Carroll et al, 1997;Lee and Caporn, 1999;Carroll et al, 2003). In 1999 there was an increase in grass cover, and a strong dose-related decrease in herbs, legumes, geophytes and monocarpic plants from the lowest nitrogen treatment on (35 kg N ha -1 yr -1 ).…”