Factors influencing plant community development and wildlife use in small conservation wetlands in southeastern Wisconsin.

摘要

Despite decades of interest in wetland restoration, few studies have been published describing effects of age, design, or landscape placement on development of vegetation or wildlife use on a large sample of restorations. Likewise, no published studies compare the effects of seeding and natural colonization on development of plant communities in replicated wetland sites over 7 years old. A 1991 study described the vegetation in 11 unseeded and 5 seeded wetlands 1-3 years after construction. I was able to resample 9 of those sites at age 12, and I expanded the sample to include additional wetlands ranging from 1 to 17 years post-restoration, for a total wetland sample size of 120. I used quantitative surveys to describe plant communities, general wildlife use and use by birds. For the avian surveys I repeated samples taken on 30 wetlands nine years previously when the wetlands were 2-6 years old. I analyzed the effects of time, design, landscape placement, and the introduction of native wetland seed on the development of biological functions in this large sample of restored and created wetlands.;Plant community diversity and floristic quality increased steadily through time, although the change was most dramatic during the first five years. The bird community shifted dramatically from wetland to old-field habitat guilds over 10 years of succession, and the mean number of birds recorded per wetland per visit increased from 5.5 to 21, primarily due to increases in eight dominant species. Part of this increase may also be due to a change in vegetation structural complexity caused by a large increase in woody plant cover in the oldest wetland age classes. Floristic quality was higher in young wetlands located nearer to woodlands or natural wetlands, however once wetlands were older than five years there were no longer significant differences correlated with landscape placement, with the exception of wetlands with relatively more agricultural land in their drainage basin, which had significantly lower floristic quality. Larger wetlands and those with more open water had higher bird species richness and number of wetland dependant species.;At one and two years old seeded wetlands had higher floristic diversity and quality than unseeded wetlands and also had significantly greater cover of native wetland plants and less of non-native plants. At 12 to 13 years these same seeded wetlands continued to have higher floristic diversity and quality than unseeded wetlands, but no significant differences in the variables summarizing the structure of the plant communities including cover of reed canary grass (Phalaris arundinacea) and cattail (Typha sppj, cover of woody plants, non-native species, or native wetland plants. In short, while the seeded wetlands in this study retained a distinct native wetland plant flora and diversity, seeding did not influence the overall structure of the plant communities over time.