Spatial modelling of landscape composition and pattern in a maquis–forest complex, Mont Do, New Caledonia

The endemic conifer species Araucaria laubenfelsii forms a characteristic component of the various forest and non-forest vegetation assemblages present on Mont Do, New Caledonia. It is the only tree species in the landscape to be found in both maquis (shrubland) and forest patches. Adult density ranges from zero in some parts of the maquis to extremely high in others, forming an Araucaria woodland. The current landscape structure on Mont Do appears to be the result of recurrent disturbance, especially by fire. However, it is uncertain whether this structure is the result of recent changes in the fire regime (as a result of Melanesian and European phases of human colonisation of New Caledonia) and is therefore transient, or represents a more stable formation. A spatially explicit grid-based model was developed to explore some of these issues. The model is primarily concerned with understanding how alterations to the disturbance regime (past and future) may influence the landscape structure and, in particular, whether the current landscape pattern is a result of increased fire frequencies over the last century and whether certain unusual vegetation assemblages in the landscape, such as maquis with emergent Araucaria, are likely to persist in the long-term. The ecological context of the spatial landscape model is described as is a simple sensitivity analysis of the model and an example of its use under ‘baseline’ conditions.