Cyclic succession: Difference between revisions
No edit summary |
No edit summary |
||
| Line 1: | Line 1: | ||
Cyclic succession is a pattern of vegetation change in which in a small number of species tend to replace each other over time in the absence of large-scale disturbance. Observations of cyclic replacement have provided evidence against traditional Clementsian views of an end-state climax community with stable species compositions. Cyclic succession is one of many kinds of ecological succession, a concept in community ecology. |
Cyclic succession is a pattern of vegetation change in which in a small number of species tend to replace each other over time in the absence of large-scale disturbance. Observations of cyclic replacement have provided evidence against traditional Clementsian views of an end-state climax community with stable species compositions. Cyclic succession is one of many kinds of [[ecological succession]], a concept in community ecology. |
||
When used narrowly, ‘cyclic succession’ refers to processes not initiated by exogenous disturbances or physical changes in the environment<ref>Morin, Peter Jay (1999). Community Ecology, Wiley-Blackwell, 342 ISBN 0865423504, 9780865423503 </ref>. However, broader cyclic processes can also be observed in cases of secondary succession in which regular disturbances such as insect outbreaks can ‘reset’ an entire community to a previous stage<ref>Mock, K.E., Bentz, B.J., O’Neill, E.M., Chong, J.P., Orwin, J., Pfrender, M.E. 2007. Landscape-scale genetic variation in a forest outbreak species, the mountain pine beetle (Dendroctonus ponderosae). Molecular Ecology 16: 553–568.</ref>. [[Image:CyclicSuccession.png|frame|right|Graphic Model of Cyclic Succession]]These examples differ from the classic cases of cyclic succession discussed below in that entire species groups are exchanged, as opposed to one species for another. |
When used narrowly, ‘cyclic succession’ refers to processes not initiated by exogenous disturbances or physical changes in the environment<ref>Morin, Peter Jay (1999). Community Ecology, Wiley-Blackwell, 342 ISBN 0865423504, 9780865423503 </ref>. However, broader cyclic processes can also be observed in cases of secondary succession in which regular disturbances such as insect outbreaks can ‘reset’ an entire community to a previous stage<ref>Mock, K.E., Bentz, B.J., O’Neill, E.M., Chong, J.P., Orwin, J., Pfrender, M.E. 2007. Landscape-scale genetic variation in a forest outbreak species, the mountain pine beetle (Dendroctonus ponderosae). Molecular Ecology 16: 553–568.</ref>. [[Image:CyclicSuccession.png|frame|right|Graphic Model of Cyclic Succession]]These examples differ from the classic cases of cyclic succession discussed below in that entire species groups are exchanged, as opposed to one species for another. |
||
Revision as of 18:52, 1 May 2009
Cyclic succession is a pattern of vegetation change in which in a small number of species tend to replace each other over time in the absence of large-scale disturbance. Observations of cyclic replacement have provided evidence against traditional Clementsian views of an end-state climax community with stable species compositions. Cyclic succession is one of many kinds of ecological succession, a concept in community ecology.
When used narrowly, ‘cyclic succession’ refers to processes not initiated by exogenous disturbances or physical changes in the environment[1]. However, broader cyclic processes can also be observed in cases of secondary succession in which regular disturbances such as insect outbreaks can ‘reset’ an entire community to a previous stage[2].
These examples differ from the classic cases of cyclic succession discussed below in that entire species groups are exchanged, as opposed to one species for another.
In the long-term, climate cycles can result in cyclic vegetation changes by directly altering the physical environment [3].
Modeling cyclic succession
The cyclic model of succession can be described in terms of a transition matrix. Based on the Markov chain, the matrix describes the likelihood of future states based on the milieu of present states [4]. The three states in the simplest cyclic model are open substrate (usually a bare patch of land), Species A dominance, and Species B dominance. With respect to facilitation, inhibition, and tolerance models of succession, the key feature of the cyclic model is that A and B are not autosuccessional – that is, they do not facilitate their own growth. Rather, A will either facilitate the succession of B or be eliminated (through mortality) such that the patch occupied becomes open substrate. This results in a cyclic scheme of species dominance.
History
The cyclic model of succession was proposed in 1947 by British ecologist Alexander Watt. In a seminal paper on vegetation patterns in grass, heath, and bog communities[5], Watt describes the plant community is a regenerating entity consisting of a “space-time mosaic” of species, whose behavior is characterized by patch dynamics. Based on the current composition and its corresponding stage of succession, a community is either be in an ‘upgrade’ phase toward late-successional shrubs or ‘downgrade’ degenerate phase toward grasses. These phases would occur in a predictable cycle. Watt’s study has since become a classic example frequently cited in scientific ecology.
Empirical evidence
Strong empirical evidence for cyclic succession can be found in Watt’s follow-up publication on the bracken system in New Phytologist[6].
Another salient example of cyclic replacement occurs in a two-species plant community in the Sonoran Desert. Even though water availability is limiting such that only one species would be predicted to survive, Larrea tridentata and Opuntia leptocaulis are observed to replace each other in the absence of environmental disturbance[7].
Mechanisms
Cyclic succession is a descriptive phenomenon that can be accounted for by several factors. In Watt’s bog system, he suggested that factors endogenous to the plant species were at play. He writes, “Each patch in this space-time mosaic is dependent on its neighbours and develops under conditions partly imposed by them.”[8] That is, species-specific life history characteristics such as mortality give rise to the cyclic dynamics observed. Exogenous factors, such as depredation by herbivores, can be indirect drivers for cyclic succession by modulating life history characteristics like mortality rate. Density-dependent root gnawing by rodents is proposed as one such mechanism in the Larrea-Opuntia system.
It is important to note that cyclic succession is not intrinsic to a species, as Watt’s Calluna bushes have been observed in non-cyclic systems[9]. Rather, it is the aggregate composition of species that gives rise to the cyclic process.
Notes
- ^ Morin, Peter Jay (1999). Community Ecology, Wiley-Blackwell, 342 ISBN 0865423504, 9780865423503
- ^ Mock, K.E., Bentz, B.J., O’Neill, E.M., Chong, J.P., Orwin, J., Pfrender, M.E. 2007. Landscape-scale genetic variation in a forest outbreak species, the mountain pine beetle (Dendroctonus ponderosae). Molecular Ecology 16: 553–568.
- ^ Utescher T, Ivanov D, Harzhauser M, et al. Cyclic climate and vegetation change in the late Miocene of Western Bulgaria. Palaeogeography, Palaeoclimatology, Palaeoecology [serial online]. February 2009;272(1/2):99-114. Available from: Academic Search Premier, Ipswich, MA. Accessed April 30, 2009.
- ^ Gotelli, Nicholas J. (2008) A Primer of Ecology 4th Edition, Sinauer Associates, Inc., 180-186. ISBN 978-0-87893-318-1
- ^ Watt, Alexander. Pattern and Process in the Plant Community. Journal of Ecology, Vol. 35, No. 1/2 (Dec., 1947), pp. 1-22. http://www.jstor.org/stable/2256497
- ^ Watt, Alexander. Contributions to the Ecology of Bracken (Pteridium aquilinum). VII. Bracken and Litter. 2. Crown Form. New Phytologist, Vol. 68, No. 3 (Jul., 1969), pp. 841-859. http://www.jstor.org/stable/2431462
- ^ Yeaton, Richard. A Cyclical Relationship Between Larrea Tridentata and Opuntia Leptocaulis in the Northern Chihuahuan Desert. Journal of Ecology, Vol. 66, No. 2 (Jul., 1978), pp. 651-656. http://www.jstor.org/stable/2259156.
- ^ Watt, Alexander. Pattern and Process in the Plant Community. Journal of Ecology, Vol. 35, No. 1/2 (Dec., 1947), pp. 1-22. http://www.jstor.org/stable/2256497
- ^ Glenn-Lewin, D.C. and E. van der Maarel. 1992. Patterns and processes of vegetation dynamics. Plant Succession Theory and Prediction, Pp. 11-59. Chapman-Hall.