PARENT SESSION
Oral Session #25: Soil Ecology: Microbial and Invertebrate. Presiding: W. Parsons.
Tuesday, August 7, 2001. 8:00 AM to 12:00 PM. Hall of Ideas G.
Microbiotic crusts and surface soil characteristics affect water and N infiltration in American beachgrass stands .
Thiet, Rachel1, Boerner, Ralph1, 1
ABSTRACT- Colonization by Ammophila breviligulata (American beachgrass) is the principal mechanism by which coastal dunes are stabilized. Microbiotic crusts composed of bryophytes and cyanobacteria often colonize spaces between grass culms. To determine whether this crust affects beachgrass vigor, we conducted a greenhouse experiment utilizing intact soil cores from the Indiana Dunes National Lakeshore. We subjected soil cores to artificial rainfall over a full growing season with rainfall patterns typical for the site. We quantified the volume and N content of leachate in relation to the degree of crust development, rainfall volume, rainfall intensity, the presence of litter, and light intensity. At rainfall volumes of <2.5 cm, little or no rainfall leached through the cores, regardless of crust cover. The extent of crust development did not affect the amount of rainfall or N that leached through cores. Relatively intense rainfall resulted in greater leachate volume, but not leachate N, than diffuse rainfall. The addition of grass litter to the surface of soil cores increased the amount of N in leachate. Less leachate (p < 0.01) and NH4 (p < 0.10) moved through cores exposed to full sun than through shaded cores. The movement of water and the transfer of N to the Ammophila rooting zone appear to be affected by different properties of the soil surface. We will discuss how this influences the persistence of beachgrass in the Indiana Dunes ecosystem.
KEY WORDS: microbiotic crust, dunes, Ammophila, nutrient relations