Mining for mosses: Metacommunity dynamics following wildfires at Red Rock Canyon, Nevada (Mojave Desert)

Background/Question/Methods

Dispersal is often proposed as a mechanism for maintaining regional diversity in desert plant metacommunities, and is assumed to be important for recolonization following local disturbances such as wildfire. Post-fire colonization of Mojave Desert mosses originates from plants or propagules sourced from one of three spatial profiles: (1) soil spore-banks, (2) aerial spore rain, and (3) existing surface communities. While desert mosses are particularly sensitive to fire disturbances, it is not yet known how dispersal shapes post-fire colonization across landscapes, or if fires directly impact latent propagules within regional soil-banks. I used a ‘mining for mosses’ community analysis approach to quantify propagule availability and assess the relative colonization potential of each of the three spatial profiles following wildfire disturbances. At 480 sample points representing 24 fire-disturbed and 24 undisturbed sites across a Mojave Desert landscape, I collected and germinated propagules from soil cores and aerial spore-traps, in addition to measuring species abundances and microsite factors in corresponding surface communities. I calculated diversity and community similarity measures for each of the three spatial profiles, and compared communities using multi-response permutation procedures (MRPP) and non-metric scaling (NMS) ordination. Multivariate species abundances were regressed on microsite environmental variables using non-parametric multiplicative regression.

Results/Conclusions

The soil spore-bank was more important than aerial spore dispersal for maintaining diversity in a desert moss metacommunity subjected to wildfires, although continuous spore rain likely contributed to the accrual of soil spore-banks across larger time frames. Soil bank profiles possessed species not otherwise observed in corresponding surface plant communities, and exhibited high β-diversity, although abundances were negatively affected by increasing fire severity. By comparison, the aerial spore rain exhibited lower β-diversity across collection points, regardless of disturbance history. Microsite topography and shrub availability had influential local effects on surface communities, likely serving as ‘ecological filters’ during spore establishment. These results collectively suggest that colonization of desert mosses after wildfires depends on regional dispersal both in space (aerial) and in time (soil), but that further development of local communities is guided both by the severity of the fire disturbance as well as deterministic factors of specific microsites. Given projections of increased fire frequency and severity in the Mojave Desert, this information has applications for guiding fire suppression and restoration activities that can promote patterns of local colonization and maintain regional diversity in desert plant metacommunities.