On the dynamics of vegetation: Succession in model communities
- 60 Downloads
Successional change is thought to be at least partially driven by forees originating from within the community, namely by ‘reaction’ and competition. Both processes operate through changes in the environment, but from the literature on the subject it is not clear how they differ.
To clarify these issues successiens of model communities are studied. This leads us to conclude that competition represent an instantaneous interaction, whereas reaction has historical aspects since it relies on cumulative changes in the environment. The three models considered-one relying on reaction to cause vegetational change, one relying on competition and differential growth rates, and a hybrid third one-yield very similar predictions: roughly bell-shaped curves displaced along the time axis. This shows that the mere fit of a certain model to successional data may easily be spurious (recently some workers have empirically fitted models identical to one derived here from first principles). The three models do behave radically different under perturbation, however: any model relying completely or partially on historical interactions cannot account for the well known possibility of artificially arresting succession. Even if the importance of historical interactions in succession (i.e. the Markovian character of succession) cannot easily be ascertained, one can nevertheless ask whether historical interactions are at all necessary for the explanation of successional change. It is argued here that succession can be entirely understood in terms of instantaneous interactions, notably competition. The argument rests upon the well known relationship between colonizing and competitive ability, and on the fact, proven here, that stress, defined as expressing itself in severe random fluctuations in the growth parameters, is negatively correlated with competition intensity.
KeywordDynamics Models Succession Vegetation
Unable to display preview. Download preview PDF.
- BellmanR. 1970. Introduction to Matrix Analysis. McGraw-Hill, New York. 403 pp.Google Scholar
- Bharucha-ReidA.T. 1960. Elements of the Theory of Markov. Processes and Their Applications. McGraw-Hill, New York, 468 pp.Google Scholar
- Clements, F.E. 1916. Plant Succession. Carnegie Inst. Wash. Publ. 242. 512 pp.Google Scholar
- DaubenmireR. 1968. Plant Communities. Harper & Row, New York, 300 pp.Google Scholar
- DruryW.H. & I.C.T.Nisbet. 1973. Succession. J. Arnold Arb. 54: 351–368.Google Scholar
- EmienJ.M. 1973, Ecology: An Evolutionary Approach. Addison-Wesley, Reading, Mass. 493 pp.Google Scholar
- Hulst, R. van 1979 On the dynamics of vegetation: Markov chains as models of succession. Vegetation 39 (in press)Google Scholar
- MayR.M. 1973. Stability and complexity in model ecosystems. Princeton Univ. Press, Princeton, N.J. 235 pp.Google Scholar
- Maynard SmithJ. 1974. Models in Ecology. Cambridge University Press, Cambridge. 146 pp.Google Scholar
- OdumE.P. 1971. Fundamentals of Ecology. Saunders, Philadelphia, 574 pp.Google Scholar
- PielouE.C. 1969. Introduction to Mathematical Ecology. Wiley, New York. 286 pp.Google Scholar
- ShugartH.H.Jr., T.R.Crow & J.M.Hett. 1973. Forest succession models: a rationale and methodology for modelling forest succession over large regions. Forest Sci. 19: 203–212.Google Scholar
- WalterH., 1973, Vegetation of the Earth in Relation to Climate and the Eco-physiological Conditions. Springer, New York. 237 pp. (Joy Wieser (translator), Vegetationszonen und Klima, Verlag Eugen Ulmer, Stuttgart, 2nd., 1973).Google Scholar