CONSEQUENCES OF NONEQUILIBRIUM RESOURCE AVAILABILITY ACROSS MULTIPLE TIME SCALES - THE TRANSIENT MAXIMA HYPOTHESIS

Nonequilibrium biotic responses to changes in resource limitation domi nate the behavior of tallgrass prairic ecosystems. Rates of leaf photo synthesis on a time scale of minutes, amounts of annual plant producti vity, patterns in the productivity of certain consumer groups, and amo unts of soil organic matter accumulation over millennia all reflect bi otic responses to frequent and recurring shifts in limiting resources. Productivity is higher during a transition period when the relative i mportance of an essential resource is changing than during an equilibr ium interval generated by single resource limitation. These ''transien t maxima'' are both characteristic and easily measurable in the tallgr ass prairie because of the unpredictable climate and ecological constr aints such as grazing and recurrent fires that modify water, nitrogen, and light availability. Such diverse phenomena as overcompensation fo r herbivory, the intermediate disturbance hypothesis, maximum levels o f productivity observed in successional ecosystems, and widespread nit rogen limitation in terrestrial and aquatic ecosystems can be explaine d by biotic response to shifts in limiting resources.