Primary production and management of seasonally flooded prairie marshes harvested for wild hay

Abstract

Experimental spring-flooded and nonflooded water regimes were applied to prairie marshes dominated by whitetop grass (Scolochloa festucacea) in Manitoba, Canada, to examine their effects on aboveground and belowground primary production and to evaluate flooding management for wild hay production. Spring flooding increased marsh aboveground and belowground production. Annual and perennial forbs comprised a greater portion of aboveground production in nonflooded marsh. Two methods (soil coring and ingrowth into mesh bags) showed earlier commencement of belowground growth and greater belowground production in flooded marsh. Higher rhizome ingrowth in flooded marsh indicated that spring flooding increased plants' ability to replenish belowground reserves. The percentage of plant production allocated aboveground was greater in flooded marsh, but shifts in allocation were small compared with the absolute increases in production caused by flooding and could not account for the observed differences in aboveground production between flooding regimes. The strong plant growth response to flooding indicates that management that conserves or mimics the natural spring-flooded hydrologic regime can increase whitetop forage production and control invasion by undesirable species. Key words: belowground, hydrologic regime, prairie marsh, primary production, rhizomes, roots.