Saturday, 15 July 2006

Preliminary Study on Vertisols and Vertic Soils in Heilongjiang Province, NE China.

Shanmei Wu, Nanjing Agricultural Univ/Univ of California, Berkeley, CA 94705, Xainzhou Long, Heilongjiang Water Conservancy and Hydropower Inst, Haerbing, 150080, China, Shengrong Xu, Nanjing Agricultural Univ, San Pablo Ave., Albany, CA 94706, and Qing Xu, Cotra Costa College, San Pablo Ave., San Pablo, CA 94806.

While evidence from previous literature indicated that there are favorable conditions for the occurrence of Vertisols in NE China, little attention has been paid to that region. Clayey parent materials,lacustrine sediment, clayey loessial (Pleistocene) and fluvial (Holocene), and the sediment of Tertiary and Quaternary basalts are wild distributed on depressions and plains. The montmorillonite and illite are two dominant secondary clay minerals. Also, the monsoon and north temperate climate is characteristic with distinct alternating dry and wet seasons. In this preseentation we intend to show the new findings on distribution and diagnostic characteristics. The classification is based on Keys to Soil Taxonomy (USDA, 2003).The cryic soil temperature regime is above about 46.5 degree of N. Latitude and the frigid is in the south of the province. The mean annual precipitation is between 400 to 660 mm and about 70% of the rainfall is concentrated in the summer. The soil starts to freeze between October or November, and does not melt until until late June or August. Preliminary results showed that some Cryerts are derived from loess-like deposits and lacustrine sediment in low positions of the landscape. The maximum depth of frozen soil is about 2.5 to 2.8 m, or more. The clay content (<0.002mm) for the entire soil horizon of representative pedons of Typic Haplocryerts from Yian, Nahe, Minshui is, on average, 34.68%, and 41.97 % for Typic Humocryerts in Fujin county. Angular/wedged-shaped structures can be found at 35-58 cm in depth and thicknesses between 55-80 cm. Soil shrinking in late spring creates cracks 1-3 cm in width and the depth may reach between 1 and 1.8 m, or more. Some Sodic Haplocryerts can be found in Fuyu-Lindian area within the SW alluvium-lacustrine basin. In the south, the most extensive suborder is Aquert, which is derived from various clayey deposits. There are Salaquerts, Natraquerts, and Calciaquerts formed from the lacustrine deposits in Anda-Zhoudong area where the maximum thickness of frozen soil is about 2.0 to 215 m. Some Epiaquerts and Endaquerts can be found in the SanJiang plain, where some soils have an expanding potential 2 to 3 times higher than that of the Mollisols. Hydromorphic process and degleyfication play important roles in the formation and land use of Aquarts. Some Calciusterts are formed in the SW of the province. On the whole, the common characteristics and morphologies of the Vertisols in the study areas are clay texture, with its content consisting of more than 30%. angular block/wedge-shaped structure in subsoil with high bulk density, and cracks from soil surface by soil shrinking and frost both common in Vertisols and Vertic soils. In addition, the Fe-Mn spots/concretions in subsoil horizons are common. The main programs are soil dryness in late spring-early summer, extra soil water during melting and after raining season, high plasticity, and the secondary soda-salinization. The long period frost-melting cycling has great impact on soil morphology and needs to be studied further. Also, soil micro-morphology needs to be studied more.

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