| The inhibition model of vegetation succession states that disturbance is a feature of all vegetation communities. Strong winds may topple trees or fires may clear large areas of forest cerat8ing gaps through which any species may enter purely by chance.Once a species enters there is a race to maintain the lead. Some ecologists even say that there is no lasting climax and that successing leads nowhere. Individual species make temporary alliances so that succession may run in any or several directions. This is the disequilibrium view of succession. The Krakatoa islands in Indonesia are studied and seem to support this theory. The eruption of the volcano sterilised the three surounding islands in 1883 and a new island appeared in 1930. About 150 years have passed since the beginning of the observation of vegetation succession on the islands. The three islands exhibited similar growth and species in the first 50 years but afterwards they changed pace and the species begun to diversify in proportion to each other. Two of the islands exhibited rapid growth while one had slow growth. The vegetation change is patchy because of tree fall, fires and deseases that affect the islands' vegetation. The opportunities for dispersal of seedlings etc. are also different on the islands so the islands developed differently. The islands changed pace at different times with multidirectional change rather than Clements unidirectional model. |
