Decline in atmospheric sulphur deposition and changes in climate are the major drivers of long-term change in grassland plant communities in Scotland

Ruth J Mitchell; Richard L Hewison; Debbie A Fielding; Julia M Fisher; Diana J Gilbert; Sonja Hurskainen; Robin J Pakeman; Jacqueline M Potts; David Riach

doi:10.1016/j.envpol.2017.12.086

Decline in atmospheric sulphur deposition and changes in climate are the major drivers of long-term change in grassland plant communities in Scotland

Environ Pollut. 2018 Apr:235:956-964. doi: 10.1016/j.envpol.2017.12.086. Epub 2018 Feb 21.

Authors

Ruth J Mitchell¹, Richard L Hewison², Debbie A Fielding², Julia M Fisher², Diana J Gilbert², Sonja Hurskainen³, Robin J Pakeman², Jacqueline M Potts⁴, David Riach²

Affiliations

¹ The James Hutton Institute, Craigiebuckler, Aberdeen, AB15 8QH, UK. Electronic address: Ruth.Mitchell@hutton.ac.uk.
² The James Hutton Institute, Craigiebuckler, Aberdeen, AB15 8QH, UK.
³ The James Hutton Institute, Craigiebuckler, Aberdeen, AB15 8QH, UK; Department of Ecology, University of Oulu, Pentti Kaiteran katu 1, 90014, Oulu, Finland.
⁴ Biomathematics & Statistics Scotland, Craigiebuckler, Aberdeen, AB15 8QH, UK.

PMID: 29358149
DOI: 10.1016/j.envpol.2017.12.086

Abstract

The predicted long lag time between a decrease in atmospheric deposition and a measured response in vegetation has generally excluded the investigation of vegetation recovery from the impacts of atmospheric deposition. However, policy-makers require such evidence to assess whether policy decisions to reduce emissions will have a positive impact on habitats. Here we have shown that 40 years after the peak of SO_x emissions, decreases in SO_x are related to significant changes in species richness and cover in Scottish Calcareous, Mestrophic, Nardus and Wet grasslands. Using a survey of vegetation plots across Scotland, first carried out between 1958 and 1987 and resurveyed between 2012 and 2014, we test whether temporal changes in species richness and cover of bryophytes, Cyperaceae, forbs, Poaceae, and Juncaceae can be explained by changes in sulphur and nitrogen deposition, climate and/or grazing intensity, and whether these patterns differ between six grassland habitats: Acid, Calcareous, Lolium, Nardus, Mesotrophic and Wet grasslands. The results indicate that Calcareous, Mesotrophic, Nardus and Wet grasslands in Scotland are starting to recover from the UK peak of SO_x deposition in the 1970's. A decline in the cover of grasses, an increase in cover of bryophytes and forbs and the development of a more diverse sward (a reversal of the impacts of increased SO_x) was related to decreased SO_x deposition. However there was no evidence of a recovery from SO_x deposition in the Acid or Lolium grasslands. Despite a decline in NO_x deposition between the two surveys we found no evidence of a reversal of the impacts of increased N deposition. The climate also changed significantly between the two surveys, becoming warmer and wetter. This change in climate was related to significant changes in both the cover and species richness of bryophytes, Cyperaceae, forbs, Poaceae and Juncaceae but the changes differed between habitats.

Keywords: Climate change; Grazing; Nitrogen deposition; Species richness; Sulphur deposition.

MeSH terms

Biodiversity*
Bryophyta
Climate Change*
Ecosystem
Grassland*
Nitrogen / analysis
Plants / classification*
Poaceae / classification
Poaceae / growth & development
Scotland
Sulfur / analysis
Sulfur / pharmacology*

Substances

Sulfur
Nitrogen