Relationships between speciesrichness, community evenness, and invasibility through time inMichigan successional old fields

Emery, S. and K.L. Gross

Presented at the ASM in Seattle (2003-09-18 to 2017-12-05 )

Growing concern over the potential loss of native biodiversity due to invasion by non-native species has resulted in a need for ecologists to better understand the relationship between community diversity and invasibility.  A number of studies have investigated the relationship between species richness and invasibility at single points in time, but very few have examined the role of evenness, or the dynamics of these relationships across time.  Kellogg Biological Station LTER provides a good system for quantifying such relationships, as species richness and abundance have been monitored over the past 14 years in old fields of varying ages.  In this study, we examined relationships between community invasibility (changes in total and non-native species richness over time), invader impact (relative abundance of non-native species), species richness, biomass, and community evenness in successional communities at KBS.  In early successional fields, total species richness has been increasing and evenness has been decreasing since the fields were last plowed in 1988, though the rates of invasion slowed after the first five years. Communities with high initial evenness had fewer non-native invasions and the higher native species richness over time, though evenness was not generally a good predictor of invasibility.  In the three older successional fields, non-native abundance decreased while native species richness increased over ten years of monitoring. Evenness did not significantly change across the ten years.  These patterns are in contrast to earlier studies that predicted that total species richness and evenness should increase with successional time, and that species richness, evenness, and invasibility are related in predictable ways. The identity and abundance of the dominant non-native species in this system, as well as past land use history, may explain some of the differences in relative invasibility and successional trajectories of these communities.

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