ROOT-GROWTH, AND MICROORGANISMS ASSOCIATED WITH THE RHIZOPLANE AND ROOT-ZONE SOIL OF A NATIVE C-4 GRASS ON BURNED AND UNBURNED SAND PRAIRIES

We investigated the root growth of native Schizachyrium scoparium, little bluestem grass, and the seasonal abundance of rhizoplane and root zone soil microorganisms on burned and unburned sand prairies. Root growth and abundances of rhizoplane and root zone microorganisms were greater in burned than unburned sites. Microbe populations were nearly always higher on the rhizoplane than in the root zone soils, although they were not always significantly different. The seasonal dynamics of total bacteria, total fungi, fluorescent pseudomonads, and microorganisms that decompose chitin, cellulose, and protein varied between burned and unburned sites. Some microbial populations showed significant, though weak, relationships with root growth. Populations of most microorganisms were usually highest from June through August, when roots were being shed following the peak standing crop of root mass in May. The production of fine roots on burned sites early in the growing season and the consequent shedding of fine roots probably have an important effect on microbe population dynamics.