How does water move in mosses ? Liquid and vapour flow in living sphagnum mosses

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Peatlands comprise 14% of Canada's land area. The accumulation of peat (a major carbon sink) is largely due to the presence of Sphagnum mosses. Sphagnum mosses lack roots and a vascular structure to deliver water to the growing part of the plant (top). It has generally been assumed that water is wicked up from the water table below through the small capillary spaces that are formed between adjacent strands of moss, as they cluster together in a community. The amount of water they can retain or draw from below is an important control on the rate of growth, but also the rate of decomposition of plant material. While liquid flow through capillary spaces has been assumed, the process has not been well documented because of the inability of standard methods to measure it, and a poor understanding of the process relating to the structure of the plant. In my laboratory we have just developed instrumentation to measure the properties of the moss that control liquid flow. We are now set to perform a series of experiments to investigate the migration and storage of water through the mosses to test its ability to sustain moisture in the critical growing part of the plant. This proposal also aims to test this for various species of Sphagnum, which have distinctly different community structures, and therefore occupy different niches in the wetland. In a related set of experiments we want to find if vapour flow is important in keeping the upper part of the mosses hydrated - even though we know the amount of water in vapour is relatively small. Understanding these processes is important for the restoration of mined peatlands, where the substrate restricts water flow to mosses that could potentially regenerate there. The above experiments will be directed at understanding this process, so that we can better manage disturbed peatlands, or at least manage our expectation for their recovery. The overall (long-term) objectives of my research, therefore, are to use lab and field tests to measure and understand the water stores and fluxes within Sphagnum mosses, between mosses and mined peat substrates, and to model these processes.