1. We conducted field experiments to examine factors influencing macroinvertebrate colonization of seasonally flooded marshes. Few macroinvertebrate species were found aestivating in soils within non-flooded wetlands indicating that most taxa colonize these marshes from other flooded habitats. 2. We manipulated amounts of salt grass (Distichlis spicata) to examine how emergent plant cover affects aerial colonization by macroinvertebrates. Areas mowed 3 weeks before flooding had low plant cover, areas mowed 5 and 9 weeks before flooding had medium and high plant cover, respectively, and non-mowed control areas had the most plant cover. Macroinvertebrate numbers and biomass were generally higher in mowed treatment areas than in control areas, but overall diversity was generally higher in high plant cover and control areas than in low plant cover areas. 3. Mosquitoes (Culicidae), brine flies (Ephydridae) and hover flies (Syrphidae) were positively correlated with amount of plant cover, and waterboatmen (Corixidae), midges (Chironomidae) and water scavenger beetles (Hydrophilidae) were negatively correlated with plant cover. Species assemblages changed seasonally among treatment areas because these taxa colonize wetlands at different times in the year. 4. These results demonstrate that invertebrate communities may be different within plant stands with heterogeneous amounts of emergent cover, and management practices that alter the structure of wetland vegetation can influence macroinvertebrate communities colonizing seasonal marshes.

We examined the responses of invertebrates and plants important in waterfowl diets to two management methods (prescribed burning and mowing) commonly used in seasonal wetlands. Experimental plots were constructed in summer 1992 in stands of saltgrass (Distichlis spicata); 50% of the vegetation was removed in treatment areas (10 m x 10 m) by either burning or mowing. After the plots were flooded, we sampled aquatic invertebrates monthly from we sampled plants that grew in areas that had been burned or mowed. Burning and mowing treatments had very different results. Many numerically dominant macroinvertebrates and microinvertebrates had higher densities in burned treatment areas than in unmanipulated control areas, but densities of most taxa were not different in mowed treatment areas and control areas. Copepod densities were lower in burned treatment areas and oligochaete densities were lower in mowed treatment areas than in control areas. Midge (Diptera: Chironornidae) biomass was higher in burned and mowed treatment areas than in control areas. Plant species richness and percent cover of some plant taxa were higher in burned areas than in control areas. Many of the invertebrates and plants we sampled are important in waterfowl diets, and our results indicate that these methods can enhance waterfowl food resources.

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1. We conducted field experiments to examine factors influencing macroinvertebrate colonization of seasonally flooded marshes. Few macroinvertebrate species were found aestivating in soils within non-flooded wetlands indicating that most taxa colonize these marshes from other flooded habitats. 2. We manipulated amounts of salt grass (Distichlis spicata) to examine how emergent plant cover affects aerial colonization by macroinvertebrates. Areas mowed 3 weeks before flooding had low plant cover, areas mowed 5 and 9 weeks before flooding had medium and high plant cover, respectively, and non-mowed control areas had the most plant cover. Macroinvertebrate numbers and biomass were generally higher in mowed treatment areas than in control areas, but overall diversity was generally higher in high plant cover and control areas than in low plant cover areas. 3. Mosquitoes (Culicidae), brine flies (Ephydridae) and hover flies (Syrphidae) were positively correlated with amount of plant cover, and waterboatmen (Corixidae), midges (Chironomidae) and water scavenger beetles (Hydrophilidae) were negatively correlated with plant cover. Species assemblages changed seasonally among treatment areas because these taxa colonize wetlands at different times in the year. 4. These results demonstrate that invertebrate communities may be different within plant stands with heterogeneous amounts of emergent cover, and management practices that alter the structure of wetland vegetation can influence macroinvertebrate communities colonizing seasonal marshes.