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S.F. Thrush and R.B. Whitlach
disturbance/recovery dynamics are frequently assessed. Essentially, close to
the disturbance, small, fast growing and rapidly colonising opportunistic
species reach high densities. Moving further from the disturbance a transition
zone occurs which is still dominated by opportunistic species although not at
such high densities. Some larger and more mobile species are also found. At
the end of the successional trajectory, a diverse assemblage dominated by
large and slow growing deeper burrowing organisms is found. Important over
this trajectory is habitat modification by species that influence the success of
other colonists (e.g., Rhoads 1974). When comparing locations it is important
to remember that Pearson and Rosenberg (1978) recognised both the contribution of adult life-stages as early colonisers and the hydrodynamic regime in
controlling the recovery processes. Their later research also emphasised the
importance of food supply in affecting broad-scale variations in benthic
successional processes (Pearson and Rosenberg 1987). These factors can
account for many of the exceptions to the predictions of these classical successional models.
In order to find generality between different locations and/or times we seek
to identify processes that might influence broad-scale differences (i.e. those
that operate over large scales) and use these to explain the variability between
studies. Hierarchy theory is often advocated as an approach to help deal with
scale (Allen and Starr 1982, but see Schneider 1994). A hierarchical approach
to understanding the relative importance of environmental processes, life
history and species interactions was developed by Zajac and Whitlatch (1985).
Although this model was not originally designed to be spatially explicit, more
recent work has refined this framework to better understand how recovery
processes may vary with increasing scale of disturbance (Zajac et al. 1998).
The hierarchy of Zajac and Whitlatch (1985) dictates the importance of
environmental factors in broad-scale comparisons: with increasing spatial
extent we expect to encompass a greater range of environmental conditions.
While this type of conceptualisation warrants further investigation, hierarchical approaches can be problematic in that it is often difficult to isolate
processes to individual scales (Thrush 1991). Furthermore, interactions between processes classified at different levels in the hierarchy can be important
determinants of the recovery processes.
S.F. Thrush and R.B. Whitlach
disturbance/recovery dynamics are frequently assessed. Essentially, close to
the disturbance, small, fast growing and rapidly colonising opportunistic
species reach high densities. Moving further from the disturbance a transition
zone occurs which is still dominated by opportunistic species although not at
such high densities. Some larger and more mobile species are also found. At
the end of the successional trajectory, a diverse assemblage dominated by
large and slow growing deeper burrowing organisms is found. Important over
this trajectory is habitat modification by species that influence the success of
other colonists (e.g., Rhoads 1974). When comparing locations it is important
to remember that Pearson and Rosenberg (1978) recognised both the contribution of adult life-stages as early colonisers and the hydrodynamic regime in
controlling the recovery processes. Their later research also emphasised the
importance of food supply in affecting broad-scale variations in benthic
successional processes (Pearson and Rosenberg 1987). These factors can
account for many of the exceptions to the predictions of these classical successional models.
In order to find generality between different locations and/or times we seek
to identify processes that might influence broad-scale differences (i.e. those
that operate over large scales) and use these to explain the variability between
studies. Hierarchy theory is often advocated as an approach to help deal with
scale (Allen and Starr 1982, but see Schneider 1994). A hierarchical approach
to understanding the relative importance of environmental processes, life
history and species interactions was developed by Zajac and Whitlatch (1985).
Although this model was not originally designed to be spatially explicit, more
recent work has refined this framework to better understand how recovery
processes may vary with increasing scale of disturbance (Zajac et al. 1998).
The hierarchy of Zajac and Whitlatch (1985) dictates the importance of
environmental factors in broad-scale comparisons: with increasing spatial
extent we expect to encompass a greater range of environmental conditions.
While this type of conceptualisation warrants further investigation, hierarchical approaches can be problematic in that it is often difficult to isolate
processes to individual scales (Thrush 1991). Furthermore, interactions between processes classified at different levels in the hierarchy can be important
determinants of the recovery processes.