Abstract: Seventeen sampling plots were established along an altitudinal gradient in northern Mt. Gaoligong, and the vertical distribution patterns of plant community, species composition, and species diversity were studied by using quantitative classification. The results showed that with the increase of altitude, the forest community had a transit of evergreen broad-leaved forest (2 000-2 300 m) to mixed coniferous and broad-leaved forest mainly composed by broad-leaved trees (2 300-2 600 m), mixed coniferous and broad-leaved forest mainly composed by coniferous-leaved trees (2 600-3 000 m), and coniferous forest (3 000-3 100 m). The species richness and β diversity of woody plants decreased obviously with increasing altitude, while the species richness of herbaceous plants had an increase after an initial decrease with increasing altitude, and increased obviously over timberline. The lowest β diversity of herbaceous plants was found in mid-altitude region. With the increase of altitude, the proportion of tropical and subtropical components decreased, while that of temperate and cosmopolitan components increased. China endemic elements were limited in mid-altitude region. As a whole, temperate plants dominated the flora, and the floral balance point existed at 2 100-2 200 m.

Key words: Tillage system, Paddy field, Ridge-no-tillage, Soil animal, Soil microorganism, Soil enzyme activity