Root dynamics of tallgrass prairie in wet and dry years

Abstract

Root dynamics were studied using root windows at Konza Prairie, a tallgrass prairie [dominated by Andropogon gerarsdii] in north central Kansas [USA] during dry (1984) and wet (1985) years. Amounts production, and disappearance of root length decreased during drought but increased when rains resumed; however, standing crop remained low. The 1985 root lengths increased throughout the growing season, while production and disappearance remained constant. Yearly summaries of amounts, productivity, and decomposition by 10-cm increments in soil depth show that the effect of drought on these variables decreased with increasing soil depth. Turnover rates of root length averaged 564 in the dry year versus 389% in the wet year, with the largest difference noted in the 0- to 10-cm depth (800 in 1984 versus 540% in 1985). Production and decay patterns observed using root windows were also noted in root biomass data (obtained from soil cores). The average total root biomass turnover rate was 31%. Failure to sort belowground materials into tissue types (rhizomes, roots) and live versus dead status results in reduced estimates of biomass turnover rates. The greatest possible separation of plant components presents the most comprehensive picture of (belowground) growth dynamics.