Recovery Dynamics in Benthic Communities: Balancing Detail with Simplification
Attempting to match pattern with dynamic processes has a long history in ecology (Kitching 1937 ; Watt 1947 ). For marine soft-sediment macrobenthic communities, the disturbance mosaic model (Johnson 1970 , 1973 ) has provided a dynamic framework in which
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14.1 Introduction Attempting to match pattern with dynamic processes has a long history in ecology (Kitching 1937; Watt 1947). For marine soft-sediment macrobenthic communities, the disturbance mosaic model (Johnson 1970, 1973) has provided a dynamic framework in which to describe patterns of spatial heterogeneity and biodiversity. The model describes the role of local disturbance events in producing patches containing benthic assemblages with different compositions at different successional stages. The perspective provided by this conceptual model emphasises that benthic communities are complex and dynamic. Spatial heterogeneity created by local disturbance events can account for resource patchiness (Thistle 1981; Van Blaricom 1982), communities with mixed trophic structure (Probert 1984) and ubiquity of opportunistic species. Thus, local disturbance events frequently playa central role in influencing the structure and function of benthic communities. Field experiments that involve monitoring macrobenthic recolonisation in previously defaunated sediments have provided insights into the nature of benthic succession and the relative importance of various biotic and abiotic factors affecting the recovery process. These experimental studies are often interpreted and generalised within the patch -dynamic conceptual framework developed by Johnson (1970, 1973). This information is also often used to help understand or predict the ecological consequences of much larger scale disturbance events. Practical and ethical considerations limit the scales over which field experiments are feasible (Kareiva and Andersen 1988; Schneider 1994; Thrush et al. 1996a, 1997a, 2000). Since experimentally defaunated sediment patches used in experiments are typically restricted to spatial scales of centimetres to metres, we must be cautious about scaling-up. Scaling-up is not as straightforward as directly extrapolating from results at smaller scales. Non-linear processes are most likely to be important in organising the shift from one range of scales to another. Not only can broadEcological Studies, Vol. 151 K. Reise (ed.) Ecological Comparisons of Sedimentary Shores © Springer-Verlag Berlin Heidelberg 2001
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S.P. Thrush and R.B. Whitlach
scale large and slow processes control smaller scale events but also nature can surprise us and the latter can affect the former (Holling 1996). However, despite the scale dependence of their results, field experiments are still powerful tools in developing a mechanistic understanding and revealing the importance of life and natural history characteristics of component species. For example, general predictions of the consequences of habitat disturbance by commercial fishing, based on the results of field experiments and natural history characteristics (e.g., changes in biodiversity, density of epifauna and large and long -lived species), have been tested and largely validated by broadscale surveys (Thrush et al. 1998). The power of inference drawn from such broad-scale surveys is greatly increased by
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