Modelling the habitat preference of two key <i>Sphagnum</i> species in a poor fen as controlled by capitulum water content

Current peatland models generally treat vegetation as static, although plant community structure is known to alter as a response to environmental change. Because the vegetation structure and ecosystem functioning are tightly linked, realistic projections of peatland response to climate change require the inclusion of vegetation dynamics in ecosystem models. In peatlands, Sphagnum mosses are key engineers. Moss community composition primarily follows habitat moisture conditions. The known species habitat preference along the prevailing moisture gradient might not directly serve as a reliable predictor for future species compositions, as water table fluctuation is likely to increase. Hence, modelling the mechanisms that control the habitat preference of Sphagna is a good first step for modelling community dynamics in peatlands. In this study, we developed the Peatland Moss Simulator (PMS), which simulates the community dynamics of the peatland moss layer. PMS is a process-based model that employs a stochastic, individual-based approach for simulating competition within the peatland moss layer based on species differences in functional traits. At the shoot-level, growth and competition were driven by net photosynthesis, which was regulated by hydrological processes via the capitulum water content. The model was tested by predicting the habitat preferences of Sphagnum magellanicum and Sphagnum fallax – two key species representing dry (hummock) and wet (lawn) habitats in a poor fen peatland (Lakkasuo, Finland). PMS successfully captured the habitat preferences of the two Sphagnum species based on observed variations in trait properties. Our model simulation further showed that the validity of PMS depended on the interspecific differences in the capitulum water content being correctly specified. Neglecting the water content differences led to the failure of PMS to predict the habitat preferences of the species in stochastic simulations. Our work highlights the importance of the capitulum water content with respect to the dynamics and carbon functioning of Sphagnum communities in peatland ecosystems. Thus, studies of peatland responses to changing environmental conditions need to include capitulum water processes as a control on moss community dynamics. Our PMS model could be used as an elemental design for the future development of dynamic vegetation models for peatland ecosystems.

Long-term responses of forest-floor bryophytes buried by tephra in the 1980 eruption of Mount St. Helens

Responses in bryophyte communities following volcanic disturbance are not well understood. The eruption of Mount St. Helens on May 18, 1980 deposited large amounts of tephra (aerially transported volcanic ejecta) on nearby forests in southwestern Washington and presented an opportunity to examine bryophyte succession, with a focus on mosses. We examined moss community changes over 36 years following this disturbance using permanent plots located in old-growth conifer forests. We used an experimental design where some of the plots had tephra removed shortly after the eruption. Initial dramatic decreases in total bryophyte cover, moss species richness and diversity in plots with intact tephra were followed by increases by 2016. Community profiles also shifted through time but were somewhat site-specific. Moss community change was related to changes in vascular plant species and was driven by changes in a few key moss species with distinct growth strategies. Bryophyte change through time was most pronounced in tephra-impacted plots, but differed among sites. Overall, total bryophyte cover had recovered, reaching our estimate of pre-disturbance levels at all sites after 36 years, but trajectories of change differed among sites, demonstrating the importance of idiosyncratic site factors and dynamics of the vascular plant species.

Ludovic McLellan Mann and the Cambusnethan bog body

This article considers the circumstances, aftermath and legacy of the discovery of a bog body near Cambusnethan in North Lanarkshire in 1932. The body of a man and a unique jacket were assessed by Ludovic McLellan Mann soon thereafter and removed to Glasgow Museums where they remain today. The body was popularly perceived to be a Scottish Covenanter although there is no scientific or historical evidence of this, and Mann himself was vague. In an attempt to provide some clarity, this article traces the interplay between archaeological and historical evidence, as well as contemporary popular memory around the find. There is an enduring belief the body was a Covenanter, exemplified by a cairn in Greenhead Moss Community Nature Park in Lanarkshire which has displayed the story since 1997. In the last 25 years, there have been repatriation claims for the remains and the story was raised in the Scottish Parliament. Thus, Mann's archaeological practice continues to shape opinion today although in this case his work was exemplary. Whilst the ‘Covenanter in the bog’ was not Mann's myth, this article reveals how the story evolved and why it remains in the popular consciousness across Scotland.

Effect of crustose lichen (<i>Ochrolecia frigida</i>) on soil CO₂ efflux in a sphagnum moss community over western Alaska tundra

Soil CO2 efflux-measurements represent an important component for estimating an annual carbon budget in response to changes in increasing air temperature, degradation of permafrost, and snow-covered extents in the Subarctic and Arctic. However, it is not widely known what is the effect of curstose lichen (Ochrolecia frigida) infected sphagnum moss on soil CO2 emission, despite the significant ecological function of sphagnum, and how lichen gradually causes the withering to death of intact sphagnum moss. Here, continuous soil CO2 efflux measurements by a forced diffusion (FD) chamber were investigated for intact and crustose lichen sphagnum moss covering over a tundra ecosystem of western Alaska during the growing seasons of 2015 and 2016. We found that CO2 efflux in crustose lichen during the growing season of 2016 was 14 % higher than in healthy sphagnum moss community, suggesting that temperature and soil moisture are invaluable drivers for stimulating soil CO2 efflux, regardless of the restraining functions of soil moisture over emitting soil carbon. Soil moisture does not influence soil CO2 emission in crustose lichen, reflecting a limit of ecological and thermal functions relative to intact sphagnum moss. During the growing season of 2015, there is no significant difference between soil CO2 effluxes in intact and crustose lichen sphagnum moss patches, based on a one-way ANOVA at the 95 % confidence level (p

A novel mesocosm set-up reveals strong methane emission reduction in submerged peat moss Sphagnum cuspidatum by tightly associated methanotrophs

Wetlands present the largest natural sources of methane (CH4) and their potential CH4 emissions greatly vary due to the activity of CH4-oxidizing bacteria associated with wetland plant species. In this study, the association of CH4-oxidizing bacteria with submerged Sphagnum peat mosses was studied, followed by the development of a novel mesocosm set-up. This set-up enabled the precise control of CH4 input and allowed for monitoring the dissolved CH4 in a Sphagnum moss layer while mimicking natural conditions. Two mesocosm set-ups were used in parallel: one containing a Sphagnum moss layer in peat water, and a control only containing peat water. Moss-associated CH4 oxidizers in the field could reduce net CH4 emission up to 93%, and in the mesocosm set-up up to 31%. Furthermore, CH4 oxidation was only associated with Sphagnum, and did not occur in peat water. Especially methanotrophs containing a soluble methane monooxygenase enzyme were significantly enriched during the 32 day mesocosm incubations. Together these findings showed the new mesocosm setup is very suited to study CH4 cycling in submerged Sphagnum moss community under controlled conditions. Furthermore, the tight associated between Sphagnum peat mosses and methanotrophs can significantly reduce CH4 emissions in submerged peatlands.