Nitrogen deposition drives loss of moss cover in alpine moss–sedge heath via lowered C : N ratio and accelerated decomposition. Issue 2 (3rd February 2018)

• Record Type: Journal Article
• Authors: Britton, Andrea J.; Mitchell, Ruth J.; Fisher, Julia M.; Riach, David J.; Taylor, Andy F. S.
• Is Part Of: New phytologist. Volume 218:Issue 2(2018)
• Page Start: 470
• Page End: 478
• Publication Date: 2018-02-03
• Subjects: bryophytes -- C : N ratio -- carbon pool -- community composition -- litter decomposition -- nitrogen pool -- nitrogen saturation -- Racomitrium heath; Botany -- Periodicals; 580
• DOI: 10.1111/nph.15006
• Languages: English
• ISSNs: 0028-646X

Abstract

Summary: In alpine ecosystems, nitrogen (N) deposition has been linked to plant community composition change, including loss of bryophytes and increase of graminoids. Since bryophyte growth is stimulated by increased N availability, it has been hypothesized that loss of bryophyte cover is driven by enhanced decomposition. As bryophyte mats are a significant carbon (C) store, their loss may impact C storage in these ecosystems. We used an N deposition gradient across 15 sites in the UK to examine effects of N deposition on bryophyte litter quality, decomposition and C and N stocks in Racomitrium moss–sedge heath. Increasing N deposition reduced C : N in bryophyte litter, which in turn enhanced decomposition. Soil N stocks increased significantly in response to increased N deposition, and soil C : N declined. However, depletion of the bryophyte mat and its replacement by graminoids under high N deposition was not associated with a change in total ecosystem C stocks. We conclude that decomposition processes in Racomitrium heath are very sensitive to N deposition and provide a mechanism by which N deposition drives depletion of the bryophyte mat. Nitrogen deposition did not measurably alter C stocks, but changes in soil N stocks and C : N suggest the ecosystem is becoming N saturated.