THE RELATIONSHIP OF FLOODS, DRYING, HOW AND LIGHT TO PRIMARY PRODUCTION AND PRODUCER BIOMASS IN A PRAIRIE STREAM

Factors related to autochthonous production were investigated at sever al sites along a prairie stream at Konza Prairie Research Natural Area . Primary production, algal biomass, litter input, and ability of floo ds to move native substrate were measured. Additional experiments were conducted to establish the influence of light and water velocity on p rimary production rates and recovery of biomass following dry periods. The study period encompassed two extreme (> 50 year calculated return time) floods, thus we were able to analyze the effects of scour on pe riphyton biomass and productivity. Biomass of sedimentary algae was re duced greatly by flooding and did not reach preflood amounts during th e 2 months following the first flood. Rates of primary production asso ciated with sediments recovered to levels above preflood rates within 2 weeks. Biomass of epilithic periphyton was not affected as severely as that of sedimentary algae. Little relationship was observed between water velocity and photosythetic rates. Production reached maximum ra tes at 25% of full sun light. Epilithic chlorophyll levels recovered w ithin eight days following a dry period, and chi a was an order of mag nitude greater on rocks than sediments 51 days after re-wetting. Estim ated annual rates of primary production were 2.6 times greater in the prairie than in the forest reaches of the stream. The ratio of annual autochthonous:allochthonous carbon input was 4.81 for prairie and 0.32 for the forest. Periphyton production in prairie streams is resilient with regard to flooding and drought and represents a primary carbon s ource for the system.