Biological Soil Crusts Inhibit Seedling Germination in an Inland Sand Plain

Biological soil crusts (BSCs) are soil aggregations of diverse biotic organisms like cyanobacteria and algae that are often topped off with a layer of lichen and/or moss. These crusts are best-known in arid to semi-arid regions where they can play a key ecological role, whether by physical or biological means. BSCs can stabilize the soil against wind and water erosion, be important nitrogen fixers, and promote or inhibit the growth of vascular plants. The literature has been heavily biased towards studying crusts in arid and semi-arid regions, despite the fact that they are present even in our temperate northeast. This experiment sought to investigate the constituents of these northeastern crusts and their impact on seedling germination. Crust and bare soil samples were excised from the Albany Pine Bush Preserve (NY) using petri dishes. Twenty seeds of Round-headed Bush Clover (Lespedeza capitata) and Sundial Lupine (Lupinus perennis) were scattered onto each dish and then placed under white light. There were ten replicates of each soil treatment (crust and bare sand). Germination was recorded at emergence of the radicle, and the sprout was subsequently plucked to avoid intra-species interaction. Bush Clover and Lupine had a significantly greater amount of seeds germinate on bare soil than crusted dishes, three and five times, respectively (P < 0.0001). Thus, we conclude that BSCs inhibit plant germination at the Albany Pine Bush and therefore can influence the spatial patterning of the plant community. Heterogeneity is likely increased in these systems due to the presence of BSCs, as the literature shows that often different species are able to germinate and establish with different rates of success. Finally, we emphasize that crusts are an under-appreciated component of northeastern barren habitats that play a larger ecological role in our region than has been recognized.