塔克拉玛干沙漠腹地人工植被土壤肥力变化

Changing of Eolian Soil Fertility in Central Taklimakan Desert Under Impact of Artificial Vegetation

在极端干旱的塔克拉玛干沙漠腹地 ,利用地下咸水 (矿化度 4～ 5 g/L)灌溉建立人工植被后 ,不仅改善了当地的生态环境 ,也促进了风沙土的成土发育 ,使土壤内部发生了一系列的变化 ,通过分析测定 ,结果表明人工植被建立对流沙的固定和成土发育产生了深刻的影响 ,它使土壤内部的各个性质都发生了显著的变化 ,土壤物理、化学性质得到改善 ,土壤的肥力提高 ,这种变化是随着植被建立时间的延长而逐渐增大的。同时由于受到不同植被类型和人为措施的影响 ,使得相同种植时间的不同样地 ,土壤性质的变化有差异。另外从土壤物理、化学和生物因子等方面出发 ,建立了土壤肥力综合评价指标体系 ,并利用多元统计方法 ,对塔克拉马干沙漠腹地人工植被建立过程中土壤肥力的变化特征进行综合评价。结果表明 ,随着人工植被建立时间的延长 ,土壤肥力呈增长趋势 ,但由于植被类型和人为措施的不同 ,相同种植时间的植被样地 ,土壤肥力的变化不同 ,变化最为显著的是蔬菜地、花卉地和草地 ,IFI值分别为 0 .689、0 .72 9和 0 .

Artificial plantations were set up by irrigating saline groundwater (salt content is 4~5g/L ) in central Taklimakan desert of extremely arid area. Four years later, it changed the ecology environment and landscape of desert, at the same time, soil properties of artificial vegetation have been changed greatly. Obviously, soil has begun formation processes during the foundation of artificial vegetation, we analysed all changes of soil properties. First, compared with drifting sand dune, the soil profile of vegetation has been changed some: (1) more organic matters accumulate in topsoil; (2) the color of topsoil is more darker because of the influence of root, irrigation and organic fertilizer; (3) more roots throughout the soil profile. By analyzing the soil particle component of typical plots, the results showed that the soil texture did not change greatly because the time of vegetation building was too short, fine sand (0 25~0 05mm) was still dominant in soil. Different from the drifting sand dune, the content of clay (<0.001mm) and physical clay (<0 01mm) of vegetation soil was more than that of motive sand. Clay is significant important to improve the soil fertility. Compared with drifting sand dune, the soil bulk density, porosity and saturated water content all were changed, it means that sand dune developed forward to the good structure soil after the vegetation has been set up. Saline water irrigating can settle the problem of fresh water pinch in desert. But the saline water can bring the physiological drought to plant root, which affect the plant growth and even cause the plant to die, so the change of salt content in the soil profile is essential to plant and land sustainable development. In central Taklimakan desert, after the artificial vegetation was set up by irrigating the saline water (salt content is 4~5 g/L), the eolian soil salt content in the profile of 50cm has not increased (except topsoil of some plots, such as irrigation experiment field), by contrary, the irrigation water played a salt eluviation part. This is mainly because of the facile transportation of water and air in the sand. Salt accumulated below the depth of 100cm in the profile commonly. Otherwise the change of soil pH is different, the vegetation soil pH is higher than that in drifting sand dune. The change of salt content in soil is important to set up artificial vegetation using saline water in arid areas and to rebuild the degenerative ecosystem. After the artificial vegetation was set up, the most obvious character of sand is the increasing of soil fertility which indicate the sand begun the process of soil evolution. This paper analyzed the dynamic change of soil fertility after the artificial vegetation was set up from plant nutrient content, amount of microorganisms and soil enzyme activities. By analyzing the content of nutrients, the author found that there were more organic matter, total N, available N, available P than in parent material, but the content of available K was lower than that in parent material. As a whole, after the artificial vegetation was set up, the content of nutrient increased and the fertility advanced, this is coherent with the analysis results of soil microorganism and soil enzyme activities. After the artificial vegetation was set up, the water and organic matter content increased. So the results showed that soil microorganisms bacteria, fungi, actinomyces are more abundant than those of original soil obviously, the longer the artificial vegetation was set up, the more the microorganisms were. But in the plots which were planted in the same time, the amount of microorganisms were variable because the vegetation, the change of soil physical chemical properties, the density and type of plant, the growth of plant and the manage measures were different. On the other hand, bacteria were predominant in soil, actinomyces were the second, and fungi the least. The microorganisms in the topsoil were much more than those in subsoil. The biology process is very faint in drifting sa