Biodiversity Changes of the Fragmented Tropical Rain Forest in Yunnan

Tropical habitats and tropical forests have been fragmented, the effects of fragmentation of tropical seasonal rain forests on ecology and biodiversity were summarized with previous studies. The findings indicated that with fragmentation of the forest, species diversity is usually reduced, and the smaller of the fragment and the greater of the disturbance, the greater of the species diversity reduction. In life form composition, the liana and microphanerophyte species increased in the fragmented forests, but epiphyte, megaphanerophyte, mesophanerophyte and chamaephyte species decreased. Tree species with small populations are lost first in the process of fragmentation. The species of different ecological species groups changed greatly, heliophilous or pioneer tree species increased, and shade-tolerant species were reduced. Phylogenetic structure changed distinctly from clustering to dispersion with fragmentation of the forest. In addition, in fragmented habitats, the edge-related changes in environment and plant diversity, that is edge effects, arose on the margin of forest. The plant species and individual numbers are higher in the forest edge than in the interior, and especially lianas increase conspicuously in the edge. The greater of the disturbance to the forest, the more light-demanding species appear both in the edge and the interior. The number of families with abundant species increased in the edge, while the families with less species abundance were more in the interior. Tropical seasonal rain forests are mainly regenerated through understory seedlings and sapling, the damage of it caused by understory crop planting, which suppresses the regeneration of tropical rain forests. The decrease in area and the consequent fragmentation of the seasonal rain forest mainly due to the expansion of rubber have been obviously the principal factors leading to loss of biodiversity.