Habitat fragmentation impacts on biodiversity of evergreen broadleaved forests in Jinyun Mountains, China

Abstract

The plant communities and their microclimates were surveyed and observed, and the soil fertilities were determined in six plots of evergreen broadleaved forests of different sizes and similar slope aspects on Jinyun Mountains of Chongqing in China from April to October, 2003. The relationships of biotic and abiotic factors were analyzed using the Simpson, Shannon Wiener, and Hill diversity indices, and stepwise multilinear regression analyses techniques. The results showed that compared with continuous evergreen broadleaved forests, five fragmentations had a lower species diversity index, and different life forms showed differences in diversity index. With the decrease in patch areas, the daily differences in air temperature (ΔTa), ground surface temperature (ΔTs), daily differences in relative humidity (ΔRH), maximum wind velocity (Vmax), differences in photosynthetic available radiation (ΔPAR) (at noon) of both edges and interiors, all tended to increase. Maximum wind velocity (Vmax) and photo effective radiation in forest edges were higher than those in interior forest, which presented a stronger temperature-gained edge effect. In all the fragmentations of evergreen broadleaved forests, the depth of the edge effect was the nearest from interior forest in the biggest patch (about 15 meters away from interior forest), while the depth of the edge effect was the farthest from interior forest in the smallest patch (about 25 meters away from interior forest). With regard to the water conservation function, soil water content improved along with increasing species diversity. Some of the nutritional function substances of soil increased with increasing species diversity. The elements of microclimate, such as Ta, ΔTa, ΔTs, ΔRH, Vmax, and PAR, changed along with the extent of fragmented forest.