Drought Tolerance Thresholds in Cattail (Typha latifolia): A Test Using Controlled Hydrologic Treatments

Decades of anthropogenic flooding to create wetlands in spring for breeding waterfowl in the Canadian Prairies have produced undesirable successional shifts from open wetlands dominated by endemic Eleocharis palustris L. (spikerush), to habitats dominated by relatively closed communities of Typha latifolia L. (cattail). Using 2 greenhouse experiments, we examined the potential of specific drying regimes to cross moisture thresholds and achieve T. latifolia control while maintaining E. palustris. We assessed the morphologic (leaf density, shoot ratio, biomass) and biochemical (root carbohydrate) responses of transplanted T. latifolia and E. palustris to different soil hydrologic treatments, including continuous flooding (CF), field capacity (FC) moisture, and 5 different drying stress (DS) treatments ranging from 4 to 12 weeks in duration, including recovery during re-inundation. Our results suggest that both plant species are susceptible to low soil moisture, as exemplified by reduced growth and survival. Although T. latifolia recovery during reflooding declined with incremental severity of moisture stress, T. latifolia was more tolerant to drought than E. palustris, with soil moisture below 5% required to induce complete root mortality. We conclude that only very low soil moisture will achieve T. latifolia control, under which E. palustris will have to re-establish from seed.