Assistant Professor Purdue University West Lafayette, Indiana, United States
Background/Question/Methods
Background/Question/Methods
Disagreement of successional theory has been ongoing for nearly a century. Many ideas stem from Clements and Gleason. While many theories have been considered, they generally can be categorized using Connel and Slayter’s Inhibitions, Facilitation, and Tolerance models. In our 80-year-old forest system we hypothesized that 1) abundance of early, mid, and late successional species change over time 2) alpha diversity is high at the beginning and end of succession, beta diversity is low at the beginning and end of succession, and gamma diversity increases over time (3) certain species are more associated with certain years of our census. Our study site is the Purdue Ross Biological Reserve. It is an old growth forest that has been untouched and allowed to progress through the stages of succession since 1949. Since 1949, a census has occurred every ten years to measure the abundance of species and the related species biomass. The historical census included measurement of diameter at breast height (DBH) measurements of every tree greater than 10 cm diameter. Prior to 1979, we have only total stem counts and species abundances, but starting in 1979 we also have detailed spatial data of tree locations.
Results/Conclusions
Results/Conclusions
(1) found that relative species abundance matches that of previously studied oak-hickory forest succession with ash and elms as early successional species, oak and hickory as mid successional species, and an increase of sugar maple as a late successional species. (2) diversity results show a rise of alpha diversity during the 1950-60s, a dip between 1970-1999 and another rise in the 2000s-2010. This cyclical pattern has also been described in previous studies. (3) ordination showed certain species are more associated with certain years, but an index of co-occurrence (checkerboard score) shows that the community has been becoming increasingly random over time. Rank abundance curves show minor changes in evenness over time. Our results support Connel and Slayter’s Facilitation model of succession, which expanded on Clements’s ideas, with our abundance and diversity data of certain species following a pattern of assembly when disturbance is not present. But our ordination supports the ideas of Connel and Slayter’s Inhibition and Tolerance models which are an expansion of Gleason’s ideas. Succession is becoming an increasingly important topic for connecting ideas of community assembly. This project is a valuable resource for understanding and modeling succession and community assembly in midwestern oak hickory forests.
