Linking Restoration and Ecological Succession (Springer ... - Inecol

152 Richard J. Hobbs, Anke Jentsch, and Vicky M. Temperton
System variable
(a) Deterministic (b) Stochastic
(c) State and transition
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(d) Combined
Time/stage of development
Figure 7.1 Ecosystem dynamics can be depicted as (a) deterministic, (b) stochastic, or
(c) state and transition. In reality a combination of all three is likely (d).
from one stable state to another, with these changes being driven by particular
events, such as various types of disturbance. Disturbance events of extreme
magnitude can cause deterministic and stochastic dynamics to be nonlinear in
the sense that no return to prior reference conditions or reference dynamics is
possible.
The age-old debate has been whether ecosystem development is stochastic
or deterministic or something in between these two. Temperton and Hobbs
(2004) came to the conclusion that most ecologists would agree that simple
deterministic models are just that—too simple to describe the complexity of
dynamics actually observed in most situations. While some apparently deterministic
patterns are observable, there are usually variations around these and
often multiple developmental pathways are possible (Jentsch and Beyschlag
2003, Suding et al. 2004, Cramer in press, Hobbs and Walker in press). These
variations often relate to the timing and severity of particular disturbances,
climatic events, or soil- and resource-related phenomena.
It is increasingly clear that no one model of ecosystem dynamics is completely
appropriate in all situations and for all systems. As indicated in Fig. 7.1(d), the
same system may exhibit all three types of dynamics at different times, at different
phases of development, or under different conditions. A further emerging
realization is that whether we find stochastic, deterministic, or intermediate dynamics
depends on the level of focus and on the temporal frame of reference.
Fukami et al. (2005), for example, found community assembly rules over time
when looking at plant traits but not plant species in an old field sowing experiment.
Nevertheless, the recognition that different dynamic types are possible
is an important one in the context of the discussion of the linkage among the
different ideas surrounding succession, assembly, disturbance, and restoration.
We first discuss recent developments in ideas concerning ecosystem assembly,
and then return to the ideas of succession and disturbance.
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