Abstract: To understand the effects of environmental factors on Machilus thunbergii community in Mountain Longchi Nature Reserve, the classification, ordination and vertical distribution pattern of species diversity in this community were investigated using the Multiple Regression Tree (MRT) and the Canonical Correspondence Analysis (CCA) method, with data from 64 plots. The results showed that: (1) The Mountain Longchi Nature Reserve consisted of 153 species, 129 genera and 72 families, which belonged to midtropical evergreen broad-leaved forest, with M. thunbergii being the predominant species. The arbor layer had an absolute advantage, and the seedlings of M. thunbergii were in a disadvantaged status. (2) According to MRT results, the community could be divided into four groups: Ⅰ. Quercus acutissima+Platycarya strobilacea-Ilex chinensis+Camellia oleifera-Ophiopogon bodinieri+Lophatherum gracile, Ⅱ.Machilus thunbergii+Nyssa sinensis-Litsea cubeba+Eurya muricata-Parathelypteris glanduligera+Lophatherum gracile, Ⅲ. Cyclobalanopsis glauca+Quercus variabilis-Eurya rubiginosa+Rubus swinhoei-Parathelypteris glanduligera+Woodwardia japonica, Ⅳ. Castanopsis carlesii+Sassafras tzumu-Symplocos lucida+Rhododendron ovatum-Ardisia japonica+Ophiopogon bodinieri. The classification results reflected the trend of succession of M. thunbergii community. (3) The CCA results verified the classification results of MRT, and showed that elevation and soil moisture content were the important factors affecting the distribution and development of the M. thunbergiicommunity. (4) The species diversity of M. thunbergii community showed a unimodal distribution pattern with elevation, with a maximum value at 150 m.

Key words: elevated UV-B radiation, silicon fertilizer, rice, methane emission, paddy soil.