Long-term studies of secondary succession and community assembly in the prairie-forest ecotone of eastern Kansas, Old-field succession experiment

Local and regional-scale processes interact to govern the assembly, diversity and
functioning of ecological communities. Evaluating the interplay of these differently-scaled
processes in the regulation of ecological systems is a challenging problem, but is crucial
towards understanding and predicting the potential effects of accelerated human activity on
biological diversity and ecosystem sustainability. Since 2000, two long-term field
experiments have been underway in grasslands of eastern Kansas to investigate the interplay
of soil resource availability, species interactions and regional processes governing plant
secondary succession, community assembly, biodiversity, and ecosystem functioning. Both
experiments involve manipulations of soil nutrients in permanent grassland study plots and
employ multi-species seed addition treatments to evaluate the contribution of dispersal
limitation and regional constraints on local species pools to the regulation of plant
community dynamics.
Old-field succession experiment, previously funded by the National Science Foundation,
was initiated in 2001 in a section of the abandoned hay field that was sprayed with
herbicide, plowed and disked prior to the start of the study to investigate plant community
dynamics in the context of old-field succession initiated on bare soil. The experimental
design involves factorial experimental gradients of nitrogen (N) supply (four levels of N
fertilization), phosphorus (P) supply (two levels of P fertilization) and plant propagule
input achieved by adding seeds of 50+ native and naturalized species to half of the study
plots. With annual sampling this experiment allows us to examine old-field succession and
community assembly unfolding along gradients of N and P fertilization and under conditions
of ambient and experimentally-enriched species pools.