Henry Chandler Cowles and Succession Benjy Longworth 4/26/12

Outline Biography Cowles’ work Plant succession since Cowles – relay floristics vs. initial floristic composition

Biography Born in Kensington, Connecticut 1893 – BA from Oberlin College 1898 – PhD in Botany from University of Chicago – Faculty at U Chicago until retirement 1914 – Helps found Ecological Society of America

Main Contributions Pioneered ecology in America “Dynamic” approach to ecology Described in detail the stages of dune succession Autogenic vs. Allogenic

A selfless career Few publications Invested much of his time teaching – His largest impact may have been through the work of his students (46/77 influential ecologists between 1900 and 1950) Also spent time advocating conservation Research was very descriptive, no numbers in his papers

Publications The ecological relations of the vegetation on the sand dunes of Lake Michigan. Botanical Gazette The plant societies of Chicago and vicinity. Botanical Gazette The influence of underlying rocks on the character of the vegetation. Bulletin of the American Bureau of Geography An ecological aspect on the conception of species. The American Naturalist The Trend of ecological philosophy. The American Naturalist A Textbook of Botany for Colleges and Universities The fundamental causes of succession among plant associations The causes of vegetation cycles. Botanical Gazette The economic trend in botany. Science The succession point of view in floristics The persistence of praries. Ecology

Ecological relations … Dissertation became his most widely known publication Stages of succession = distance from the lake Described abiotic and biotic characteristics of each stage

grasses/shrubs cottonwood/poplar/basswood pine oak/maple Noticed unique vegetation at different stages

Embryonic dunes Wandering dunes Stabilized dune Impact of vegetation on physiography

Xeric, sunny, windy, sandy Mesic, shaded, less windy, soil Impact of physiography on vegetation

View of Succession Succession = mesophication process Shallow pond succession

Biotic succession (autogenic) Process driven from within Facilitation/Inhibition Humus formation – Water – Soil organisms – Temperature and aeration Shade Topographic succession (allogenic) Process driven from without Create heterogeneity of succession Disturbance due to erosion and deposition

Contemporaries Frederic Clements – Clements saw succession as a much more deterministic process than Cowles – Driven by facilitation (autogenic)

Clements Directional change from one plant community to the next until arrival at the climax community Climax

Cowles Made fewer generalizations Found plant plasticity (presence at several stages) Variable “climax” community Oak Maple

Plant succession since Cowles Clements 1916 Relay Floristics Odum 1971 Information theory Egler 1954 Initial Composition Connell and Slayter 1977 Equilibrium Holistic Dynamic Reductionist “Succession is a variable approaching a variable, not a constant.” - Cowles 1901

Relay Floristics Model Only one set of species can colonize at a time

Initial Floristic Composition Egler 1954 Succession depends on the species that establish initially All species able to establish early Different growth rates, life spans determine succession

Initial Floristics

Hibbs 1983

Model of succession depends on study system Connell and Slayter 1977 Facilitation Inhibition Neutral

Alternative Successional Pathways Impact of land use early establishment Mesquita 2001

Alternative Pathways 7 years 12 years 17 years 22 years Blue= Vismia Green = Cecropia