Plant biodiversity and its conservation strategy in the in-undation and resettlement districts of the Yangtze Three Gorges, China

The investigation on and conservation project of plant biodiversity in the inundation and resettlement districts of the Three Gorges region were carried out with the ongoing construction of the Three Gorges Dam. Based on the first-hand specimens collected for many years and the historical records, we found that there were about 1784 higher plant species, belonging to 762 genera of 170 families, which accounted for 59.19%, 75.30% and 85.85% of the total amount of species, genera and families in the Three Gorges region, including 27 species specific in these two districts. The shrub and grass communities were mostly distributed along the low-altitude river bank zone of the Yangtze River and were largely influenced by the dynamic water level of the Three Gorges reservoir area. The measurement of Shannon-Wiener and Pielou evenness indexes on 21 Pinus massoniana (Masson pine) communities distributed in the Three Gorges reservoir area was carried out, and results showed that the biodiversity of shrub layers was the highest, followed by grass layers, the middle, and tree layers, the lowest. Among the 11 typical shrub communities in this region, the abundance of shrub layers of Form. Rhus chinensis, Form. Cotinus coggygria var. cinerea, Form. Vitex negundo var. cannabifoliaand and Form. Coriaria sinica was relatively higher, which were 16, 26, 29 and 15, respectively. These four shrubs also showed high biodiversity index (H′), which were 1.791, 3.427, 2.949 and 1.718, respectively. Among the 9 grasslands mainly distributed along the river bank zone, 4 grassland communities with higher altitude (Form. Dicranopteris dichotoma, Form. Miscanthus floridutus, Form. Imperata cylindrica var. major and Form. Arthraxon hispidus) showed higher abundance and biodiversity, which were 1.697, 1.354, 1.144 and 1.018, respectively. Considering the inundation and resettlement districts, there were 22 vegetation types threatened by submersion, including 4 woody plant communities, 9 shrub communities and 9 grassland communities. The 6 shrub communities of Form. Securinega wuxiensis, Form. Bauhinia brachycarpa, Form. Geum aleppicum, Form. Distylium chinense, Form. Buxus henryi and Form. Myrsine africana would be fully submerged and part of Adianthum reniforme var. sinensis and Buxus ichangensis would be also submerged. At present, plant species conservation and monitoring stations in the Three Gorges region have been constructed, and more than 200 plant species have already been transplanted and conserved, including 37 threatened species listed in the China Plant Red Data Book and 11 local constructive species.