Colonization by woody plants in fragmented habitats of a suburban landscape

Many studies have estimated the parameters of metapopulation dynamics by assuming a steady-state habitat-occupation pattern by organisms. However, metapopulations of woody plants in suburban landscapes rarely attain a steady state owing to the long life spans of individuals. We constructed a colonization model for woody plants based on the distance from a seed-source patch containing mother trees. It is easy to determine colonization parameters with this method, which makes the method useful for conservation planning. Distance from the seed source was the most important factor for predicting the presence of juveniles in a destination patch. The probability of colonization was estimated as a logistic function of the distance from the nearest seed source. Patch-level simulations using actual colonization parameters and forest distributions (based on field measurements) showed that about half the species studied in Yokohama (Japan) would fail to recolonize the studied region for at least 20 generations. Moreover, patch density was too sparse for 30% of the studied species, which will thus be unable to expand their distributions and reverse local extinctions. Dominant species of the region's climax forest will not reach vacant patches, and normal vegetation succession will be obstructed.