Abstract
Living moss biomass and archival peat deposits represent key indicators of present and past climatic conditions, but prediction of future climatic impacts requires appropriate marker species to be characterized under a range of contemporary conditions. Stable isotope signals in high latitude moss deposits offer potential climatic proxies. Seasonal changes in δ13C and δ18O of organic material (cellulose) in representative functional groups, and associated photosynthetic activity (as chlorophyll fluorescence) have been compared across East Anglia, UK, as a function of tissue water content. Representative species from contrasting acid bog, heathland, and fen woodland habitats were selected for monthly sampling of recent growth tissues between spring 2017 and autumn 2018, with isotopic signals in purified cellulose compared with tissue water, precipitation, and nearby groundwater signals. Sphagnum and Polytrichum groups, which tend to dominate peat formation, provided contrasting and complementary indicators of seasonal variations in carbon assimilation. Cellulose δ18O signals from Sphagnum spp. demonstrate seasonal variations in source precipitation inputs; carbon isotope signals in Polytrichum spp. indicate evaporative demand and photosynthetic limitation.
Highlights
A better understanding of the timing and extent of active moss metabolism is crucial for the interpretation of peatland palaeoclimate archives [1], for the improved accuracy of global vegetation models [2], and for predicting ecosystem responses to climate change [3]
In order to interpret the high resolution stable isotope data preserved over thousands of years in both Antarctic moss banks (e.g. [5,6]) and northern peatlands (e.g. [7,8]), it is crucial to identify, for representative marker species, how preserved proxies are coupled with the environmental conditions when mosses are physiologically active
For Sphagnum species, which dominate northern boreal ecosystems, the highly hydrated tissues capture and hold precipitation inputs, and transfer the signal into δ18OC to represent a marker for changing frequency and intensity of precipitation events across maritime relative to continental landscapes [43,44,45]
Summary
A better understanding of the timing and extent of active moss metabolism is crucial for the interpretation of peatland palaeoclimate archives [1], for the improved accuracy of global vegetation models [2], and for predicting ecosystem responses to climate change [3]. [7,8]), it is crucial to identify, for representative marker species, how preserved proxies are coupled with the environmental conditions when mosses are physiologically active. Sphagnum mosses maintain a high, constant, water content, with maximum assimilation rates occurring at 70–100 times dry weight [12]. Even mosses that co-occur, such as Sphagnum and Polytrichum spp., may be metabolically active at different times and respond differently to the prevailing environmental conditions
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