Moss establishment in restoration: The role of moss production method and short-term benefits of abscisic acid

Mosses may be useful in ecological restoration activities but are excluded from most native plant materials programs. Recent efforts have attempted to propagate mosses in controlled environments for deployment to boost the recovery of degraded field sites. Field re-entry and establishment have proven challenging, possibly because the moss materials are not field-ready. We compared the field establishment rates of mosses of the same species propagated using three methodologies carried out either in greenhouses or outdoors. In an attempt to chemically boost field-readiness, we amended each with either sucrose, an osmoprotectant, or abscisic acid, a stress response phytohormone, or neither. Mosses grown outdoors with only one initial fall irrigation event lost at least 30% less cover than outdoor-grown moss that was irrigated in spring and moss tissue grown in a fog chamber inside of a greenhouse. The addition of abscisic acid also induced a subtle difference, leading to about 10% less cover loss compared to controls. Ultimately, all treatments declined to only trace level moss cover at most after 3 years. From these results, we put forward the working hypothesis that growing methodologies more similar to field conditions and exposing mosses to environmental fluctuations are more likely to produce field-ready moss materials. Abscisic acid addition is promising as a way to delay the mortality of mosses introduced into a desiccating environment. To translate short-term relative differences to long-term success, these practices may need to be combined with techniques that reduce the stress experienced in the field.