Wennian Xu

Construction of heilu soil chronofunction in Luochuan, China

Soil chronofunction is an important way to understand soil forming processes quantificationally, and the foundation for establishment of soil genesis model. To establish soil chronofunction, soil properties and 14C ages in the Holocene of heilu soil profile in Luochuan were researched. Linear, logarithmic, and third order polynomial functions were selected to fit the relationships between soil properties and soil ages. The results indicated that, third order polynomial function was the best to fit the relationships between clay (<0.002 mm), silt (0.002–0.02 mm), sand (0.02–2 mm) and soil ages, and the trend line showed the presence of Ah horizon in the profile. The logarithmic function indicated the variation of soil organic carbon and pH with time perferably. The variation of CaCO3 content, Mn/Zr, Fe/Zr, K/Zr, Mg/Zr, Ca/Zr, P/Zr, and Na/Zr with soil age could be described best by use of three order polynomial functions, and the trend line showed migration of CaCO3 and soil elements.

Holocene Soil Chronofunctions, Luochuan, Chinese Loess Plateau

Since soil genesis can hardly be observed directly over decades and centuries, the research of soil chronosequences is the most suitable way to assess quantitative knowledge on soil development (Bockheim, 1980). A soil chronosequence is a quantitative description of how the soils properties in a given area change with time (Vincent, 1994). Soil chronofunctions have been equated with the mathematical expression of chronosequence data, typically utilizing correlations and curve-fitting, or some derived combination. They are useful for studying pedogenesis, relative dating of surfaces and geologic events, and for predicting recovery rates of disturbed soils.

Quantificational research on the slope development of loess tableland in the Holocene

It is important approach to recognize natural evolution of environment on the Chinese Loess Plateau that researches on evolution of loess landform and soil erosion in the Holocene. In this study, radiocarbon age of soil, loess deposition rate and magnetic susceptibility soil from YCT and YCS profiles which respectively located on loess tableland and an adjacent slope in Yanchang County in northern Shaanxi, were used to reconstruct the landform at about 12000 a B.P. on the slope. The results indicated that the average loess deposition rate of YCT profile in the Holocene was 0.0153 cm/a, and that of YCS profile was 0.0162cm/a during 12295∼20416 a B.P‥ The slope landform had formed before about 12000 a B.P., but its gradient was smaller than the modern slope. So the soil erosion rate greater than the loess deposition rate on the slope, which was the comprehensive result of natural erosion and artificial acceleration erosion. It was proved that this method could be used to quantificational research on loess landform and soil erosion in the geological period, and provided a new idea and method in this study area.

CHRONOFUNCTIONS OF HEILU SOIL DEVELOPED FROM LOESS IN LUOCHUAN, ON THE CHINESE LOESS PLATEAU

Soil chronofunctions are an alternative for the quantification of soil-forming processes and underlie the modeling of soil genesis. To establish soil chronofunctions of a Heilu soil profile on Loess in Luochuan, selected soil properties and the 14C ages in the Holocene were studied. Linear, logarithmic, and third-order polynomial functions were selected to fit the relationships between soil properties and ages. The results indicated that third-order polynomial function fit best for the relationships between clay (< 0.002 mm), silt (0.002-0.02 mm), sand (0.02-2 mm) and soil ages, and a trend of an Ah horizon ocurrence in the profile. The logarithmic function indicated mainly variations of soil organic carbon and pH with time (soil age). The variation in CaCO3 content, Mn/Zr, Fe/Zr, K/Zr, Mg/Zr, Ca/Zr, P/Zr, and Na/Zr ratios with soil age were best described by three-order polynomial functions, in which the trend line showed migration of CaCO3 and some elements.

Applying Ecological Corridor to Promote Eco-landscapes in Hydropower Construction Region

This paper expounds the characteristics of eco-landscapes in hydropower construction region, which is compartmentalized as core disturbance zone, transitional zone and radiated zone according to the degree of construction disturbance. The importance of corridor to eco-landscapes in hydropower construction region is analyzed. It puts forward the principles, modes, steps and measures of building ecological corridor in order to strengthen the bond of isolated patches and between core disturbance zone and surround natural environment, as well as to optimize the ecosystem structure and promote the eco-landscapes in hydropower construction region. Taking the construction region of Xiangjiaba Hydropower Station as an example, through reasonable measures to build corridor network system, the fragmentation of eco-landscapes has been obviously improved, and the core disturbance zone and the peripheral area join to a whole ecosystem.