First-year regrowth of three marsh plant communities after fall and spring fires in the Delta Marsh, Manitoba

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Greenall, Jason Andrew
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This study examined the effects of fall (1990) and spring (1991) burns on neighbouring marsh plant communities dominated by Typha x glauca, Phragmites australis, or Scolochloa festucacea in the Delta Marsh, Manitoba. The focus was on plant regrowth in the first post-burn season. Two study plots 25 m x 25 m were laid out in areas where Typha, Phragmites, or Scolochloa had previously been dominant in fall-burned, spring-burned and unburned sites. Within these plots, subplots were randomly selected and the regrowth, in terms of shoot height, density, flowering, and aboveground biomass of the dominant species was monitored. The composition and aboveground biomass of the understorey was also monitored. In all plots, the position of the water table was determined and soil samples collected for moisture, organic, conductivity and pH measurements. Temperature and humidity were recorded from May to August in fall-burned and unburned Phragmites stands. In Typha communities, regrowth began earliest in plots that had been burned, but by the end of the season unburned plots produced the tallest shoots... In Phragmites communities, regrowth also began earlier in burned plots than in unburned plots...Both fall-burned and spring-burned Phragmites communities exhibited increased production over unburned areas. Significant differences in water levels, both within and between burn treatments, appeared to affect a number of regrowth parameters in this community. In Scolochloa communities, there were no significant differences between burn treatments because there was significant variability within the fall-burned treatment for all measured vegetation parameters...Both fall and spring burning led to increases in the mean species richness and aboveground biomass of understorey species. High soil conductivity in fall-burned plots appeared to affect the vegetation, with poor performance of Scolochloa and high abundance Atriplex patula. Vegetation regrowth in the three communities did not occur in a consistent or predictable manner.