A COMPARISON OF MODERN POLLEN RAIN AND VEGETATION IN SOUTHWESTERN SICHUAN PROVINCE, CHINA

Modern pollen rain samples were collected from surface sediment samples at 13 small lakes, 0.5 to 10 ha, along an elevational transect between 1800 and 3900 m using a modified Phleger sampler. A synthesis of the results from the modern pollen rain study here and other pollen rain studies of southwestern China revealed that major forest types were reflected by their pollen rain. High pollen percent values for Pinus and evergreen oaks were found at almost all elevations regardless of whether these taxa were in the surrounding vegetation. Rhododendron, Abies and Lithocarpus/Castanopsis were extremely under-represented by their pollen rain. Tsuga, Betula and deciduous oaks contained comparable or roughly equal percentages for cover values in the vegetation and modem pollen rain. The percentage of Abies and Rhododendron pollen was greatest at high elevation sites where these taxa have their highest percent coverage in the vegetation. A significant number of important taxa in the region were under-represented by their pollen rain. Two methods were effective in dealing with such a large number of under-represented taxa: (1) pollen percentage values for low pollen producing taxa of similar autecological features (e.g. mesic deciduous, sclerophyllous evergreen broadleaved) were summed and examined as a unit, and (2) noting the presence of key pollen types representative of a particular climatic regime, such as Schima, Symplocos and Mallotus whose pollen and plants were found only in lower elevation sites.