摘要
该文以塔里木河下游地区为对象,研究了沙漠化过程中土壤性质变化及其规律。结果表明:在地下水位较深时,土壤含水量与土壤不同层次土壤的质地粘重程度呈正相关;在有胡杨林存在条件下,林下灌木生存与否与40cm～60cm深度土壤含水量相关系数最大,当此层土壤水含量低于16%时,胡杨林下灌木开始消亡。作为一种分析手段,在研究中还应用分形理论以及相应的分形模型,对沙化土壤颗粒分形维数的变化特征,以及分形维数与土壤性状的关系进行了研究。结果表明,土壤细颗粒含量越少,土壤分形维数越低,表征沙漠化程度越高。土壤分维数与各粒级颗粒组分间的关系差异较大,分维数与小于0 005mm组分的相关关系最好,因此组分是土壤沙化的重要指示性粒径。土壤有机质和氮含量与土壤分维数成正比关系,表明分维数在一定程度上可以表征土地沙化演变中土壤物理性状和养分状况以及沙化程度,因此土壤分维数可作为评价土壤沙化演变的定量指标之一。对沙漠化土壤结构进行定量化描述研究,分析研究土壤风蚀沙化对土壤结构所产生的影响,对区域生态环境的保护与恢复有着重要的指导意义。
Based on data collected in low reaches of Tarim River,the soil features of desertified land were analyzed. The results show that: from upper section to lower section in low reaches of Tarim River, the average content of silt and clay in soil within a depth 30cm shows a decreasing trend, while the sand' ratio goes higher. The content of silt and clay in soil in upper section are 1.17 times and 2.41 times more than that of content in middle section and lower section. While average content of sand material in soil in upper section is only 98.45% and 94.05% comparing with sand material in soil in middle and lower sections, indicating that wind erosion become severe in middle and lower sections and much more silt and clay materials is eroded away, as vegetation decreasing and degree of desertification increasing. The soil moisture has positive relation with the soil texture at different depth of the soil, especially when the water table is lower than 8m; the survival of shrub in Populus diversifolia forest depends on the soil moisture at depth of 40～60cm, the shrub will die when soil moisture less than 16% and this can be used as a index and threshold indicating vegetation living state and limit. As an analyzing method, the fractal theory and relative model also were used to study the changes of soil granularity and its fractal features for desertified land. The results show that: the soil with less fine particles due to wind erosion has less fractal dimension and vice versa. The contents of particle size less than 0.005 has obvious exponential relation with fractal dimension (y=0.001e^(3.8531x),r^2=0.9819),and which reflects the degree of the land desertification. The greater fractal dimension means lower degree of land desertification and less fractal dimension stand for higher degree of land desertification. There also exist remarkable relation between the organic^2 matter,nitrogen of the soil and fractal dimension. Therefore,the soil fractal dimension can be used as an important and quantitative index indicating the degree of the land desertification and evaluating soil deterioration. The results also suggest that it would be significant to study quantitatively desertified soil structure and its relation with wind erosion, which will be useful for eco-environment protection, important to land and environmental restoration especially in inland arid zone.
出处
《资源科学》
CSSCI
CSCD
北大核心
2004年第5期11-17,共7页
Resources Science
基金
国家重点基础研究发展规划项目"中国西部生态环境演变与调控研究"(编号:G1999043505)。
关键词
沙漠化
土壤结构
分形维数
塔里木河下游
Desertification
Soil structure
Fractal dimension
Lower reaches of Tarim River
