Figure 9-1: Succession of plant species on abandoned fields in North Carolina. Pioneer species consist of a variety of annual plants. This successional stage is then followed by communities of perennials and grasses, shrubs, softwood trees and shrubs, and finally hardwood trees and shrubs. This succession takes about 120 years to go from the pioneer stage to the climax community. From:
Disturbance Ecology Another whole field Disturbance: any physical force, such as fire, wind, flood, extremely cold temp., or epidemic, that damages natural systems and results in mortality of organisms or loss of biomass [1997 Ecology & Field Biology] Do we define disturbances differently in the field of restoration ecology?
Ecological Succession generally defined as the continuous, more or less sequential change in the species composition of communities over time Seral stages (e.g., eastern old field early successional annual community, shrub, pine forest, late-successional [climax] hardwood forest) Climax community: mature, relatively self- sustaining seral stage State-transition models
Cooper 1913 Bot Gaz
Ecological Succession 1 o : succession that begins on areas prev. unoccupied by organisms (e.g., new oceanic island – interesting situation with Lake Mead shoreline, even sand dunes) 2 o : succession that proceeds on areas where organisms were present (e.g., ag. field, even desert bulldozed area b/c soil microbes present) Aquatic succession is 1 o – new water body open for colonization
Ecological Succession Generally, during succession, communities shift from short-lived, fast growing and reproducing species early in succession, to long-lived, infrequently reproducing species late in succession Pioneer, opportunistic spp – r-selected spp Longer lived spp – K-selected spp
Ecological Succession Two main views of succession developed in 1900s, differentiated by the degree of order assumed Clements – species modify envt; orderly replacement of one community by another, with the next more well adapted, culminating in 1 climax community type per climatic region (w/ disclimaxes – pyric climaxes, etc.) Gleason – spp respond individually
Ecological Succession Frank Egler’s (1954) initial floristics: propagules of early + late succ. spp on site Which spp become dominant depends on life-history characteristics and competitive interactions Short-lived spp are eventually replaced by long-lived, though not necessarily climax, spp
Ecological Succession Within a climatic region, consider two main concepts: Development of community parallels (causes) development of envt (and hence facilitates colonization by other spp) Physical landscape modifies the envt independent of organisms (e.g., flood, soil movement) Another view is to consider limiting resources and how they change during succession
Ecological Succession When there is a disturbance, what are factors that could affect the course of succession?
Multiple Successional Pathways Not only can a given climatic region have multiple stable states (prev. recognized, e.g., pyric climax), a given site can have multiple stable states and multiple pathways to get to these different states productivitydisturbance productivity “climax” We must not take things too far, however, as ecological systems are organized to varying degrees
Multiple Pathways Within reason, there do appear to be multiple ways to both arrive at 1 climax community type, and to multiple climax community types Different successional pathways, and different possible “end points” to succession could offer challenges and opportunities for restoration
Examples of Multiple Pathways
DEPRESSIONAL WETLAND VEGETATION TYPES: A QUESTION OF PLANT COMMUNITY DEVELOPMENT WETLANDS, Vol. 20, No. 2, June 2000, pp. 373–385
Multiple Pathways Applying succession concepts to deserts and restoration Do deserts follow the same patterns? First, are early successional communities dominated by annuals? Are late? Relative time periods required for reaching successional stages Does succession even occur in deserts?
How can successional concepts be applied for restoring disturbed areas? Initial floristics – tip balance by seeding, planting Resource limitation theory – manipulate resource levels to guide succession Work with succession, not against it Accept multiple pathways/end points – build sequentially Consider ecosystem function of multiple pathways – try to select pathways for speed, chosen functions (e.g., N-fixing spp)
Supplemental references FYI Sheley, R.L., J.M. Mangold, and J.J. Anderson Potential for successional theory to guide restoration of invasive plant dominated rangeland. Ecological Monographs 76: Cox, R.D., and V.J. Anderson Increasing native diversity of cheatgrass-dominated rangeland through assisted succession. Journal of Range Management 57: Pickett, S.T.A., S.L. Collins, and J.J. Armesto Models, mechanisms and pathways of succession. Botanical Review 53: Egler, F.E Vegetation science concepts. I. Initial floristic composition – a factor in old-field vegetation development. Vegetatio 4: Bartha, S., S.J. Meiners, S.T.A. Pickett, and M.L. Cadenasso Plant colonization windows in a mesic old field succession. Applied Vegetation Science 6: Cattelino, P.J., I.R. Nobel, R.O. Slatyer, and S.R. Kessell Predicting the multiple pathways of plant succession. Environmental Management 3: Fastie, C.L Causes and ecosystem consequences of multiple pathways of primary succession at Glacier Bay, Alaska. Ecology 76:
Supplemental references FYI Kirkman, L.K., P.C. Goebel, L. West, M.B. Drew, and B.J. Palik Depressional wetland vegetation types: a question of plant community development. Wetlands 20: Lecomte, N., and Y. Bergeron Successional pathways on different surficial deposits in the coniferous boreal forest of the Quebec Clay Belt. Canadian Journal of Forest Research 35: Inouye, R.S., N.J. Huntly, D. Tilman, J.R. Tester, M. Stillwell, and K.Z. Zinnel Old-field succession on a Minnesota sand plain. Ecology 68: Meiners, S.J., S.T.A. Pickett, and M.L. Cadenasso Exotic plant invasions over 40 years of old field successions: community patterns and associations. Ecography 25: Pickett, S.T.A., M.L. Cadenasso, and S. Bartha Implications from the Buell-small succession study for vegetation restoration. Applied Vegetation Science 4:41-52.