2 Methods
2.1 Study area
Our study area consists of two nature reserves (Heizhugou Nature Reserve, 28°40′-29°10′N, 102°50′-103°10′, and Meigu Dafengding Nature Reserve, 28°30′-28°50′ N, 102°52′-103°20′E) in Mt. Liangshan (Fig. 1). This area is within a global biodiversity hotspot (i.e. the Hengduan Mountains, Mittermeier et al., 2005) and features a subtropical monsoon humid climate with elevations ranging from 1054–4288 m.
Our study region has large areas of primary, secondary and plantation forests. Primary forests are scattered along the mountain ridges in the Heizhugou Nature Reserve and in the northeastern core area of the Meigu Dafengding Nature Reserve. Secondary forests, consisting mainly of second-growth broad-leaved trees, were allowed to recover naturally. Tree species of Pinaceae, Fagaceae and Cornaceae are dominant in the old-growth and secondary forests. Plantation forests were first planted on the land after large-scale deforestation during the 1970s and are now distributed throughout the Meigu Dafengding Nature Reserve and Heizhugou Nature Reserve. The predominant plant species in the plantation forests are Cunninghamia lanceolata, Picea asperata and Abies fabri .