Changes in the Structure of Mammal Communities over Successional Time Scales

Abstract

Multivariate analyses were used to describe graphically the post-fire patterns of change in the structure of forest and heathland small-mammal communities over successional time in Australia. Data were collected from 16 forest sites representing a temporal sequence after fire, and from one heath (shrubland) site which has been followed continuously over a 15 yr period, with regeneration from two successive fire cycles. These small-mammal communities follow a successional trajectory that may be described using factor analysis to represent seven species as factors in two or three dimensions. The trajectory illustrates the shift in community structure from one dominated by species of Pseudomys (native mice), through a period of domination by dasyurid marsupials into the longest period where species of Rattus (native rats) dominate, until they too are reduced in numbers. The strongest factor reflects the differences observed between communities from unburnt or mature seral stages and those in the early stages of regeneration after fire. This form of multivariate analysis is senstitive to the scale of the temporal data analysed and successional patterns are likely to emerge only when data from annual or greater temporal scales are used. The trajectories tend to follow a cycle as they move back towards their unburnt or undisturbed mature state. The order in which species enter the succession appears linked to the functional group to which the species belongs, which is consistent with assembly rules for these functional groups proposed previously for these habitats.