Developing a trait-based approach to understand Sphagna responses to hydrological stress in the Flow Country

摘要

Blanket bogs are a globally rare type of peatland found in high latitudes and cool, wet, oceanic limates. Blanket bog resilience depends strongly on the traits and plasticity of Sphagnum mosses, which dominate blanket bog vegetation communities. However, the scales at which Sphagna traits vary, and how they translate to ecohydrological function remains unclear. This thesis develops a trait-based perspective for the Flow Country (Scotland) by combining regional
surveys, within-site contrasts, a restoration case study, and a controlled mesocosm water table manipulation experiment.
Across precipitation and elevation gradients, three common species (S. capillifolium, S. papillosum, S. cuspidatum) showed pronounced interspecific differences in morphology, pigmentation, and water-holding capacity consistent with their hummock–lawn–pool strategies. Intraspecific trait differences among sites were generally small and inconsistently related to coarse climatic or edaphic variables, indicating trait conservatism at regional scales. At a finer spatial scale, a centre–margin comparison within a single mesotope across five species
(addition of S. austinii and S. tenellum) revealed clear, species-specific plasticity for S. papillosum, S. tenellum, and S. austinii, implicating local hydrology as primary drivers of withinspecies trait shifts.
In post-intervention forest-to-bog restoration pools, one year of water chemistry and vegetation data from 37 pools showed broadly suitable, seasonally varying but near-natural conditions. Sphagnum cuspidatum recovery was widespread and was not strongly affected by bulk chemistry which was found to already be comparable to near natural sites, with hydrological stability and propagule availability implicated as the most likely factors. Furthermore, translocation appeared to accelerate colonisation where physical conditions were already
favourable but did not result in significantly different outcomes due to the extent of spontaneous recovery at the site.
Finally, a mesocosm experiment on S. papillosum contrasted continuous versus cyclical watertable drawdown. Despite muted physiological responses (chlorophyll and ABA), ecosystemscale CO₂ fluxes were sensitive: droughted cores exhibited higher respiration and more frequent transitions toward net emission relative to high-water controls. Together, the chapters show that (i) species identity dominates trait differences; (ii) plasticity emerges most strongly along sub-mesotope hydrological gradients, rather than regional gradients; (iii) restoration outcomes within the Flow Country likely hinge on hydrology and
propagules more than water chemistry following early post-restoration flushing; and (iv) modest drawdowns can perturb carbon balance even when shoot-level stress is buffered. This thesis extends understanding of Sphagnum functional traits in the Flow Country, showing that plasticity and resilience are expressed most clearly at fine spatial scales. It highlights the need for trait research to carefully consider sampling context and scale, while reinforcing that Sphagnum’s persistence under future stress ultimately depends on restoring and maintaining
the hydrological conditions that allow these mosses to function as ecosystem engineers.

奖励日期	23 2月 2026
源语言	English
奖励机构	University of the Highlands and Islands
赞助人	Leverhulme Trust
导师	Roxane Andersen (Supervisor) & Antonia Thomas (Supervisor)