There is growing interest in using biocrusts (assemblages of cyanobacteria, lichens, mosses, and other taxa in various proportions covering the upper few millimeters of the soil surface) to assist in restoring ecosystem function and native plant communities in dryland ecosystems. Biocrusts can be transplanted and established using jute or thatch, but these methods are difficult to expand for restoration at a landscape scale. Tackifiers are organic or synthetic long-chain carbon compounds used for soil stabilization and hydroseeding and could provide a more scalable option for biocrust restoration. We examined the sensitivity of two dryland mosses, Bryum argenteum and Syntrichia ruralis, to three common tackifiers - guar, psyllium, and polyacrylamide (PAM) - at 0.5x, 1x, and 2x of recommended concentrations for erosion control and revegetation. We measured moss shoot, gemma, and protonema production as well as moss organic matter and bound substrate masses as indicators of growth. Groups of ten fragments from field-collected mosses were grown on sand in petri dishes arranged in a growth chamber in replicated blocks containing each tackifier-concentration treatment. Ten replications of Bryum and nine replications of Syntrichia were measured at the end of six and five weeks, respectively. The growth responses of fragments in each tackifier-concentration combination were compared with those of a control treatment (fragments grown on sand with distilled water) as well as by concentration within tackifier type and by tackifier type. Overall model tests yielded statistically significant results (p<0.001) for every variable in both species. When compared to water, guar tended to decrease growth, psyllium tended to increase growth, and PAM’s effects were generally neutral to positive. Within tackifier types, increasing concentrations of guar tended to decrease moss growth, while increasing concentrations of psyllium tended to increase growth. Varying concentrations of PAM had little effect on growth. Further research should examine impacts of this suite of tackifiers on moss growth and biocrust establishment in the field.
Funding Statement (additional comments about funding)
We thank for partial funding of this project: U.S. Geological Survey's Coordinated Intermountain Restoration Project; U.S. Forest Service, National Invasive Species Program; U.S. Fish and Wildlife Service, Nevada State Office; Bureau of Land Management; Oregon State University Department of Botany & Plant Pathology; and the Portland Garden Club.