Factors influencing species diversity of ferns and fern allies in fragmented forest patches in the Kyoto city area

We investigated the relationship between species diversity of pteridophytes and the environmental factors of 39 fragmented forest patches in the Kyoto city area. There was a significant correlation between the number of species and the micro-landform diversity, artificial habitat diversity, and logarithm of the area of the forest patch. When we performed a multiple regression analysis to identify the best-fit model so as to optimize the amount of variation in species diversity explained by using stepwise selection, three species diversity indices (species richness or Shannon’s diversity index, logarithm of inverse Simpson index) had significant positive partial correlations with the logarithm of area of the forest patch, and negative correlations with the logarithm of isolation distance from mountain forest. Therefore, we conclude that pteridophyte species diversity depends on patch size and isolation distance from mountain forests. Comparison of the woody plant species–area curve with the pteridophyte species–area curve showed that the rate of increase of species number (inclination) with area was the same, but the Y-intercept of the pteridophyte species–area curve was lower than that of the woody plant curve. Therefore, the minimum conservation area required for ferns and fern allies is greater than that for woody plant species.