Much of the soils in the Sikhote-Alin Mountains are cambisols. Among other types, a soil tentatively termed as "dark colored soil", has an unknown genesis. Its distribution, though poorly studied, seems to be patchy, and it bears other traits of a relict soil. Hypotheses placed ts origin from Kamchatka to the loess plateaus of China. The characteristics and genesis of this soil type were the focus of our study which utilised phytolith analysis. Also, our goal was to investigate phytolith assemblages in various types of soil in the area and compare them with those from "dark colored soils". Silica phytoliths are microscopic formations produced in cells of many plants. They are often identifiable, and are chemically stable and immobile in most types of soils. These features make them a valuable source of information on the past and recent history of soils, vegetation, and land use at a very fine spatial scale, particularly when other techniques, such as pollen analysis, can not be applied. The content and distribution of phytoliths reflect the geographic origin of soil, plant composition, slope position, and processes involved in phytoliths accumulation and distribution in the soils. This work is the first study of phytoliths in the Pacific Russia.
More than 40 silica phytolith spectrum forms were recorded in the moutain soils of Sikhote-Alin. Cluster analysis of sedge and grass phytoliths demonstrated that phytoliths assemblages from the upper horizons of "dark colored soil " under meadows are homogeneous. Phytolith spectra of the horizon A1B1 of this soil are similar to those of the upper horizon of cambisols under oak forests, which possibly means that some of the "dark colored soils" had a forest stage. Upper soil horizons under spruce forests were found fairly homogeneous, which indicate that the development of upper horizons of this soil proceeded with little vegetation change. The phytoliths of buried horizons under spruce forests are found to be similar to those of upper soil horizons under oak forests. This may imply the shift of forest composition in the past from oak to spruce in the studied sites. Homogeneous phytolith assemblages in soils under oak forests demonstrate that there were no remarkable changes in forest composition within these areas during the past 100-150 years. The geographic distribution, position within the landscape, and phytolith composition of "dark coloured soils" may support the notion that the formation of these soils was influenced by the deluvial and aeolic transport of fine mineral particles. However, more studies of the phytolith assemblages from the alleged source areas are needed to solve the problem of their geographical origin.
Anatoly Bobrov and Elena Bobrova School of Soil Science Moscow State University Moscow, Russia 119899 Phone: +7 (095) 243-1079 Fax: +7 (095) 939-0989 E-mail: anatoly@bobrov.soils.msu.su