Conditions Of Moisture And Its Energy Under Subalpine Abies Faxoniana In Western Sichuan

Soil water can not only affect plant growth and ecological environment of a region, but also has an important influence on soil formation. Savagery Lake in Ganzi Region in Sichuan Province was regarded as the object of study, while the podzol in popular idea was chosen as located site based on route investigation, where terrain was relatively flat, vegetation composition was relatively homogeneous and soil layers were relatively integrated. Soil water and its energy dynamics in study area were studied according to the combination of field survey and laboratory analysis. Results could supply further study on process and characteristics of soil formation in study area and development of basic theory on forest soil science with scientific and experimental data. Moreover, the research was conducive to forestry management and ecological protection in study area. The main research results were as follows:(1) In general, the moisture contents in soil of Layer A2in study region were higher than that of Layer B2. Moisture contents shrank with increased depth, with the characteristic of high in summer and low in winter. The highest moisture contents of Layer A2and B2both appeared in August, respectively reaching35.088%and18.867%, while the lowest respectively appeared in November and in February. From December to next May, about half of the year soil was in the frozen-thaw process. In seasonal dynamics of soil temperature, change of Layer B2lagged behind Layer A2. The maximum soil temperature of Layer A2and B2appeared successively in September and October. In winter, the soil temperature of Layer A2and B2declined to below0℃in December and April successively. From October to next March, soil temperature of Layer B2was higher than Layer A2, while in the other months the results were opposite. Influenced by weather and environment, soil temperature and moisture content of Layer A2waved during a day. While the soil of Layer B2was in deeper position and was less influenced by circumstances outside. The temperature and moisture content in Layer B2were relatively stable during a day, which was more obvious in summer.(2) Studies had shown that soil water energy was composed of the matric potential, gravitational potential and temperature potential, of which the temperature potential was the dominant. And from the view of soil water energy, the movement law of soil water and it’s resulting movement law of the mineral elements were researched. Depending on the analysis of the experiment instrument and relative theories and combining with the data from the obtained continuous locational analysis, the results showed that the soil air humidity was influenced by soil water, soil temperature and soil texture. In addition, on the basis of the existing data, spss17Software was used to create the regression equation of the study region between the soil humidity equivalent and the measured relative soil air humidity and soil temperature. The fitting degree of this equation was high. Through the equation, the continuously measured relative soil air humidity could be converted to soil water content. And then comparing this content with the one measured by drying method, it was found that the predictions were roughly the same with the measured values during the rainy season. The result of mineral elements in other study of this topic had also confirmed this law.(3) Results showed that soil temperature had a large influence on energy of soil water. Combining with other study results of this subject, the movement law of the soil water and mineral elements was founded, namely:In summer, with the thawing of the soil and the arrival of the rainy season, the soil temperature and humidity of Layer A2was relatively high. The soil water energy of Layer A2was larger than Layer B2, and the water would move down. The dissolved mineral elements would be downwardly leached. When winter came, soil temperature of Layer A2rapidly declined, which was lower than Layer B2. Then soil water energy of Layer B2was larger than the Layer A2, and the water would move up. Some mineral elements would be brought back to the top layer. Meanwhile, Soil freezing leading to the flow of water in the soil might also affect the movement of mineral elements.