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 cov..., Study Site 
Our research was conducted on MPG Ranch in the Bitterroot Valley of Montana, in an experimental enclosure fenced to exclude herbivores (46.667°N, -114.007°W, 998 m). The mean annual temperature across the ranch is 7°C, and annual precipitation is 356 mm (modeled 30-year normals; Daly & Bryant 2013) mostly falling as rain and snow during cold winters. During our experimental period nearby the enclosure, the average annual temperature was 7.9° and annual precipitation was 233 mm. Vascular plant communities across the property range from shrub steppes, grasslands, and coniferous forests, in addition to former agricultural land. Biocrusts are ubiquitous across the ranch, averaging 19% cover across all sites (Durham et al., 2018). Biocrusts are variable and may be diverse, but in most locations are dominated by the moss Syntrichia ruralis and several lichens of the genus Cladonia (Durham et al., 2018).
Moss materials
We grew biomass of the moss Syntrichia ruralis, using three...,