Detecting general plant functional type responses in fragmented landscapes using spatially-explicit simulations

Habitat loss and increasing landscape fragmentation are known to be key forces driving the ongoing loss of plant species diversity. While the combined effects of increasing isolation and decreasing population size have been studied intensively; it is less understood how plant population performance in heterogeneous landscapes is affected by changes in fragmentation alone.To test whether general rules exist to describe the complex response of plant species to fragmentation, a model is developed to simulate plant populations in a spatially realistic context. The performances of six ruderal plant functional types (PFT), as defined by Grime's CSR scheme, are compared among landscapes varying in their level of fragmentation.In general, increasing fragmentation has a negative but varying effect on the measured set of regional fitness parameters of the PFTs. For several output variables, it is not only the main functional types that differ in their relative competitive, ruderal and stress-tolerance features, but also their subtypes.Strictly ruderal types react most strongly to fragmentation intensity showing high regional extinction vulnerability. In contrast, competitive types are less affected.Some specific traits like having dormant seeds have a positive impact on some regional output variables measured. However, this positive impact is not valid for all output variables simultaneously, suggesting a trait syndrome centred view of PFT's behaviour.Our simulation experiments show that a thorough categorisation based on plant functional types provides a suitable approach for improving our understanding of complex plant species responses in dynamic heterogeneous landscapes.