PS 13-121 - Understanding the distribution of biological soil crusts within the coastal dune ecosystems of southern Lake Michigan

Background/Question/Methods

Biological soil crusts (biocrusts) are surface soil communities composed of cyanobacteria, fungi, algae, lichen, and moss. Common to drylands, biocrusts contribute to several ecosystem services, including soil stability, fertilization, and water retention. Although biocrusts are present within temperate biomes, their distribution, ecology, and function within these ecosystems has been understudied. As a result, biocrusts have yet to be integrated into the land management plans within temperate US ecosystems. The purpose of this study was to determine the abundance and distribution of biocrusts within the coastal dune ecosystems of southern Lake Michigan.



A 550 m transect was used to sample biocrusts within the Miller Woods unit of the Indiana Dunes National Park (41.619722, -87.274722), which is composed of linear, parabolic, and forested dunes. Triplicate 1 m² plots were established 5 meters apart, at intervals of 50 m along the transect. Percent cover was measured within each plot for biocrusts, vegetation, leaf litter, and bare soil. Biocrusts were visually identified by type (cyanobacterial and moss), and vegetation was grouped by type. The Kruskal-Wallis test was used to determine differences in biocrust abundance between dune slopes and dune morphologies, and Spearman’s Rho was calculated for correlations between biocrust abundance and other quantitative variables.

Results/Conclusions

Biocrusts were found in 9/32 plots, with 4 in the linear dunes and 5 in the parabolic dunes. Within crusted plots, mean biocrust coverage was 35.89 ± 11.31 %, and was significantly higher in the parabolic than the linear dunes (chi-squared = 4.86, df = 1, p-value = 0.027). More crusts were cyanobacterial-dominated (31.67 ± 12.42 %) than moss-dominated (4.22 ± 2.28 %) Biocrust coverage was positively correlated with distance from shore (Rho = 0.863, p = 0.003), but negatively correlated with vegetation (Rho = -0.77, p = 0.021) and leaf litter cover (Rho = -0.75, p = 0.021).



For the first time, our findings provide information on how biocrusts are distributed within a Midwestern US coastal ecosystem. Competition and shading may explain why biocrust abundance was negatively impacted by vegetation and leaf litter cover. However, the morphological characteristics of coastal dunes can positively impact biocrust abundance, possibly due to their effects on vascular plant distribution. Increased distance from shore diminishes wind energy and sand burial intensity, which may positively impact biocrust distribution. Understanding the ecology of biocrusts within temperate ecosystems is a critical step towards their integration into land management plans.