Project Report
Project Lead/Researchers:
Janette Thompson, Morrill Professor, Natural Resource Ecology and Management
The landscape of Iowa currently has just over 2.85 million acres of forest land, with contiguous areas of forest concentrated in the eastern third of the state and along major rivers and streams distributed throughout the state. Plant communities, especially spring-flowering herbaceous plants in the understory of Iowa’s forests, have important ecological functions (providing a reservoir of biological diversity as well as nutrient capture and recycling) and have changed over time as patterns of land use within and around them have changed.
This project was designed to reassess plant community characteristics first measured 25 years ago in forests located in seven central Iowa counties that had been influenced by different land uses, including privately-owned forests that were grazed along with nearby areas not used for grazing and compared to relatively pristine forest preserves. Our objectives were to determine if the characteristics of these plant communities have continued to change over time, and whether other contemporary changes (e.g., climate, nutrient enrichment) have led to greater numbers of invasive and native generalist species.
During spring and summer 2024 a team of faculty, graduate students and undergraduate students assessed forest plant communities present on 40 of the plots that had been first examined in the summer of 2000 (we visited 10 plots each on grazed and un-grazed forests, and 20 plots in preserved forests) located at 10 different sites. We assessed each plot twice to identify all species present in the forest, including spring ephemerals, spring-flowering, and late-flowering species as well as shrubs and vines. We collected soil samples on each plot for analysis of nitrogen and phosphorus concentrations and soil density. Overall, we catalogued 30 species of spring-flowering and 79 species of summer-flowering herbaceous plants, 30 species of native woody plants (shrubs, vines, small trees) and 32 non-native plants (both herbaceous and woody). Preliminary analyses indicate important differences in numbers of spring-flowering and total herbaceous species among plot types (both were greatest in pristine forest plots and lowest in formerly grazed forest plots). Analyses of data describing changes in plant community composition over time as well as possible differences among soil characteristics are ongoing. By re-sampling plots first analyzed 25 years ago we are able to investigate questions about plant community composition and ecosystem function changes in these important landscape features of Iowa, and to determine which sites and species should be targeted for restoration efforts in degraded forest areas.
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