Patch Dynamics and Animal Responses

The dynamics of a mosaic may depend on many factors (see for instance Levin 1976). Recently, the theme of patch dynamics, especially fragmentation, has been attracting the interest of ecologists. Patch dynamics can be experimentally duplicated and tested on natural populations. For this not only fragmentation per se but also network design and patch corridors are under study through the use of different groups of plants and animals (Fig. 4.7). For instance, Summerville and Crist (2001) in an old field tested the effect of induced fragmentation on the butterfly population (see Fig. 4.8), finding a direct effect of treatment on the populations.

Fig. 4.6 Map of the history of fires for the petran chaparral vegetation in Mesa Verde National park in 1998 (from Floyd et al. 2000)

Fig. 4.6 Map of the history of fires for the petran chaparral vegetation in Mesa Verde National park in 1998 (from Floyd et al. 2000)

Fig. 4.7 The interception of moving organisms in a continuous landscape is higher than in the fragmented one

Community and species were linearly related to the remaining habitat according to the proposed model. Plots with a higher number of forbs were visited more than poor plots demonstrating independence between patch structure and quality of patch per se. This could suggest that even modest areas can provide enough resources of quality if managed in terms of richness and may be equivalent to larger patches of modest quality. Species respond differently to fragmentation. Rare species are especially sensitive to fragmentation but other species seem not to be affected by fragmentation treatment.

Fig. 4.8 Histogram showing the effect of fragmentation treatment on a butterfly community. Rare species are present in large numbers only in unfragmented patches (15 x 15 m) of the experimental area (from Summerville and Crist 2001)

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Fragmentation treatment

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Fragmentation treatment

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