The conflicting role of pine plantations as a matrix

As the world’s forests are increasingly converted to timber plantations, more changes in land use mean a more complex matrix.  The role of the matrix surrounding remnant habitat fragments is still unclear, particularly when that matrix retains some of the wooded characteristics of the original habitat.  A big question still remains: to what extent does the matrix act as a barrier to movement, if at all?

A new publication in Animal Conservation tackles this question by looking at remnant eucalypt patches embedded in a matrix of pine plantation and grazing land.  Mortelliti et al. take advantage of an impressively large-scale (115 sites over 30,000 ha) and long-term (16 years) natural experiment called Nanangroe in south-eastern Australia to focus on the demography of two native skinks (Hemiergis talbingoensis and Carlia tetradactyla).  They go a step beyond occupancy models by quantifying long-term responses (i.e. colonization and extinction) to the transformation of the matrix from agricultural lands to pine plantations.  This allows them to focus on the effects of the outside matrix on target populations within eucalypt patches.

If you guessed that plantation forest would act as a barrier to both species, you’d be wrong.  But if you guessed that plantation forest enhanced connectivity for both species, you’d also be wrong.  Mortelliti et al. found that the role of the matrix in this setting was actually species-specific: colonization probability of eucalypt patches increased for H. talbingoensis in patches surrounded by plantation, whereas colonization probability was lower for C. tetradactyla in patches surrounded by plantation.  They suggest several hypotheses for the disparity, including differences between the two species in thermoregulation, reproductive mode, and prey availability and predation.  Their take-home message is that individuals who manage plantations alongside remnant habitat should consider corridors through the plantation matrix to get the best of both worlds.  Species that do well in the matrix still benefit, and species that do poorly can take advantage of the more open woodland corridors, so that connectivity is still maintained overall.