Forest vegetation as related to climate and soil conditions at varying altitudes on a humid subtropical mountain, Mount Emei, Sichuan, China

摘要

Altitudinal variations in temperature and soils were analysed on a humid subtropical mountain, Mt Emei (3,099 m a.s.l., 29°34.5′N, 103°21.5′E), in Sichuan, China, to see how the vegetation varies with the environmental factors. As a principal rinding, the coldest mean monthly temperature — 1℃, rather than the warmth index of 85℃·months, emerged as the primary factor that delimited the evergreen broadleaved forest. With regard to soils, properties such as organic C, total N, available P, exchangeable K tended to increase with altitude. The highest values in organic C (26.6%), total N (1.34%) and available P (45.39 ppm) were recorded in surface soils of the mixed forest (2,210 m a.s.l.) including all three tree life forms, i.e. evergreen/deciduous broad-leaved and coniferous trees. The high pH and contents of exchangeable Ca and Mg in the surface soils derived from the parent material, limestone and dolomite, between 900 and 1,200 m, where several Tertiary tree species existed. The C/N ratios of surface soils in the coniferous forests (2,500-3,099 m) were higher than those of the evergreen broadleaved forests (600-1,500 m) and the mixed forests (1,500-2,500 m).