Model comparison.

The best models (lowest AICc) are indicated in boldface type. A ‘+’ or ‘-’ sign indicates the inclusion or exclusion of that factor in the model, respectively. The number of categories included in each model for the analyzed factor is listed under rock-soil and grazing effects and the functional form used is listed for all other effects.
*Mean R2 – average of 10,000 R2 calculations of a subset of the dataset that includes all results with pines and a randomly drawn subset of the results with zero pine colonization as determined by the zero-inflated distribution of the data (1 – pz).
†Regional propagule pressure (Preg) bounded to be <100 or bounded to <1000.
Landscape propagule pressure (Plan) modeled using either spatially explicit distance-dependent models: an exponential (“Exp-Distance”) Weibull kernel, with or without the effect of the age of pines in the seed source (“+ age”), an isotropic or an anisotropic lognormal (“LN-Distance”) kernel, or an anisotropic exponential kernel skewed in 8 wind directions (“Anistropic-Exp-Distance”); or a spatially implicit (“S.I.”) distance independent model in which regional pressure is a linear function of total pine cover in 500 m distance from sample.
§Number of rock or soil categories. Soil categories include Terra-Rosa and Rendzina (2 categories) or Terra-Rosa, light Rendzina and Brown Rendzina (3 categories). Rock categories include Chalk, Marl, Dolomite and Limestone.
¶Resistance by woody cover modeled as an exponential or a lognormal (“LN-threshold”) with a lower threshold for which f (V  =  0.