Biocrust mosses from diverse localities exhibit plastic response to watering and may be successfully cultivated ex situ
Wide-scale restoration of biocrust, a living matrix of soil-dwelling dust and nutrient fixers, could mitigate dust storms, and resulting deposition on snowpack, which threatens quality of life, safety, and water supplies in arid regions. Mosses are common and vital members in many biocrust communities. We investigated feasibility and means to optimally grow a widespread biocrust moss, Syntrichia ruralis, in a greenhouse setting. We cultivated five populations collected from across the Colorado Plateau. The collections captured a precipitation modality gradient along which some mosses received the majority of their water from snowmelt, while others saw the majority in the form of summer monsoon rains. We subjected all populations to four different watering treatments, varying in duration of hydration from 2 days to 5 days weekly. We hypothesized that mosses collected from sites that primarily received water from snowmelt would be most successful under a longer hydration scenario, and that there would be a point of diminishing returns where additional water inputs would not yield more moss tissue. Homogenized tissue from each population was inoculated on sterilized sand and we recorded percent cover of the resulting growth over a five-month period.
By two months we observed differences between populations. The population that had previously received the most moisture from snowmelt had achieved greatest cover irrespective of hydration length. The more monsoonal populations achieved lesser cover. By four months, cover was comparable across all populations; the monsoonal populations had caught up. Data from the four watering treatments revealed optimal moss cover developed when tissues were subjected to three consecutive days of hydration per week. Substantial cyanobacterial and other microbial cover also developed over the course of the experiment, with increasing water inputs leading to greater total biocrust cover. Non-metric multidimensional scaling revealed cover of microorganisms unique to certain populations of moss. We demonstrated that mosses are plastic in their ability to adapt to a watering modality of continuous hydration. Our data suggest that Syntichia ruralis may be sourced from diverse localities and increased off site via this method. Initial differences in growth rates may be attributed to starting tissue quality. Interestingly, site-specific associates may be cultivated from moss propagules. Further study of stressful watering modalities, mimicking the brief hydration of monsoon rains, could evaluate the resiliency of populations to climate change, and the potential for assisted migration of biocrust mosses.