Research On Quercus Aquifolioides Forest Of Balangshan Mountain In West Sichuan, Southwest China

(1) Sclerophyllous forest is an important vegetation type, extensively distributed in Mediterranean coasts, southwestern Australia, southern North America, and southern North Africa as well. The communities are characterized by drought tolerant features such as sclerophyllous leaves, evergreen and hairs, indicating warm and dry environments in distributed regions. The flora, distributional environment and development of communities across the world vary greatly. The sclerophyllous forest is a typical forest type in western sub-tropic and southeastern Qinghai-Tibetan Plateau, distributed mainly from 2600 to 3300 m a.s.l. It is also the endemic type of subalpine vegetation in montane vertical belts in southwestern China. The sclerophyllous oak forests are relics of Tertiary and develop and evolve through several geological changes. There are more than 20 species of sclerophyllous oak in China, of which 16 species can constitute sclerophyllous oak forests.(2) There exist 436 vascular plant species, belonging to 219 genera and 73 families in the sunny slope of Balangshan Mountain. Of all the vascular species, ferns share 14 species, 12 genera of 8 families, accounting for 10.96%, 5.48% and 3.21% of the total respectively. Gymnosperm has 4 species, 4 genera of 4 families, making up 2.74%, 1.83% and 0.92% of the total respectively. Angiosperm has 418 species, 203 genera of 63 families, amounting to 86.30%, 92.69% and 95.87% of the total. Dicotyledon plants occupy 368 species, 174 genera of 56 families, accounting for 76.71%, 79.45% and 84.40% respectively of the total. Monocotyledon plants have 50 species, 29 genera of 7 families, occupying 9.59%, 13.24% and 11.47% respectively of the total. The number of plant families in lower altitudes is less than in higher altitudes. The number of plant families increase little above 3100 m elevation. World-widely distributed families dominate the flora of the Balangshan Mountain, followed by tropically and temperately distributed families. The number of tropically distributed families declines with the increase of elevation. Temperate families present double peaks along the altitudinal gradient, corresponding closely to the environmental gradient. The distribution types of plant genera in Quercus aquifolioides communities follows the order: TempG (168 genera) > PG (28 genera) > TG (23 genera) > ECHG (3 genera). In the temperate genera, northern temperate genera cover 78 genera, accounting for 47.27%. In the tropical genera, TATAG occupies 13 genera, making up 46.43%. In the flora of sunny...