Heterogeneity begets heterogeneity: Increasing soil heterogeneity increases plant diversity and richness

Link To Share This Poster: https://cdmcd.co/6ZqxrA
Live Discussion Link: https://cdmcd.co/LdDg7v

Ashley Wojciechowski and Sara Baer, Kansas Biological Survey and Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS, John Blair, Division of Biology, Kansas State University, Manhattan, KS, Scott Collins and Scott Collins, Department of Biology, University of New Mexico, Albuquerque, NM

Background/Question/Methods
The ‘environmental heterogeneity hypothesis’ (EHH) predicts that variability in the environment increases niche availability to allow more species to coexist, but few studies have supported this hypothesis within plant communities. An experimental prairie was established in 1997 to test the applicability of this hypothesis to restoration. The experiment contains replicated plots of prairie restored with no soil manipulations and prairie restored under a factorial combination of altered nutrient availability and soil depth. Two decades of study showed support for the EHH when plant diversity was compared between the control and maximum heterogeneity plots, representing two of the four heterogeneity treatments in the experiment. We measured plant diversity in all four heterogeneity treatments, including plots with either only nutrients or soil depth manipulations in addition to control and maximum heterogeneity treatments to determine which factor drives higher diversity in the maximum heterogeneity treatment. The percent cover of each species was estimated in 12 subplots within each experimental plot during the twenty-third year of restoration. Maximum cover of each species was averaged over 12 subplots in each plot to calculate plot-level richness, Shannon’s diversity, and evenness along with forb cover. We analyzed data according to a randomized complete block design.
Results/Conclusions
We recorded 59 species across all plots and the maximum heterogeneity treatment had the highest number of unique species. Maximum heterogeneity plots continued to contain higher richness than the control plots and higher richness than the nutrient heterogeneity plots, but not soil depth heterogeneity plots. The maximum heterogeneity treatment also maintained higher diversity than control plots, but similar diversity to nutrient and soil depth heterogeneity treatment. Diversity and richness variance were lower in maximum heterogeneity plots compared to control plots. Evenness was similar among all heterogeneity treatments. Forbs contributed most to diversity, but forb cover did not differ among the heterogeneity treatments due to the growth of one species in relation to sampling quadrats in control plots. Variance in forb cover was the greatest in control plots and lowest in maximum heterogeneity plots. These results were consistent with the long-term documented pattern of higher diversity in restored prairie where two soil factors were manipulated, but this pattern was not observed in plots with heterogeneity in a single soil resource. Thus, heterogeneity begets heterogeneity and the EHH has application to restoring higher diversity on a decadal time scale due to interactive effects of imposing variation in multiple soil resources.