黑河中游干旱绿洲土壤盐渍化对大型土壤动物群落的影响

以内陆干旱区黑河中游绿洲边缘区天然沙质草地及其转变的人工梭梭灌木林(21a)、人工杨树林(28 a)、人工樟子松林(33 a)和农田(开垦27 a和100 a)为研究对象,对6种样地土壤盐渍化和大型土壤动物群落特征进行调查,采用多变量排序、多元回归和通径分析及一元回归分析等方法,研究了不同土地覆被和管理措施下土壤动物群落组成及对土壤盐碱环境变化的响应.结果表明:在缺乏管理措施的情况下,单纯改变土地覆被并不会显著影响土壤动物群落结构;而在有管理措施的情况下,土地覆被变化与管理措施耦合可显著改变土壤动物群落结构.土壤动物群落演变受到土壤pH、可溶性盐及Na+、Cl-、HCO3-、Mg2+浓度的共同影响,其中Na+和可溶性盐含量的贡献率最大,是关键影响因子.土壤动物密度和类群丰富度与土壤中的Na+和可溶性盐含量呈显著负指数函数关系,与Mg2+和HCO3-含量呈显著二次曲线关系.研究区土壤动物密度和类群丰富度在Mg2+和HCO3-含量达到生态阈值点(分别为38.7 ～39.4 mg· kg-1和324.9 ～335.3 mg·kg-1)时达到峰值(40 ～ 43只·m-2和13 ～ 14科·m-2).此后,随着Mg2+和HCO3-含量的增加,土壤动物密度和类群丰富度下降.

Influence of soil salinization on soil animal community in an arid oasis of middle Heihe River basin

An investigation was conducted on the status of soil salinization and the structure of soil animal community across six land use/cover types in an arid oasis of middle Heihe River basin, and the methods of redundancy analysis, regression analysis, and path analysis were adopted to analyze the responses of the soil animal community under different land use/cover types and different management modes to the various status of soil salinization. The six land use/cover types were 21-year old shrub land without irrigation and fertilization, 28-year old poplar and 33-year-old pine plantations with irrigation, 27- and 100-year-old farmlands with irrigation and fertilization, and natural grassland, from which all the other five land use/cover types were converted. The results demonstrated that land cover change in the absence of management practices did not lead to a significant change in the abundance and group richness of the soil animal community, while land cover change in the presence of management practices resulted in a significant change in the soil animal community. The evolvement of the soil animal community structure was co-affected by soil pH, soluble salt content, and Na+, Cl, HCO3-, and Mg2+ concentrations, among which, soil soluble salt and Na had the greatest contribution, being the key affecting factors. The abundance and group richness of the soil animal community had significant negative exponential correlations with soil soluble salt content and Na+ concentration, and significant quadratic correlations with soil Mg2+ and HCO3- concentrations. The calculated ecological threshold values of soil Mg2+ and HCO3- concentrations for the abundance and group richness of the soil animal community were 38.7-39.4 mg x kg(-1) and 324.9-335.3 mg x kg(-1), at which, the abundance and group richness reached their peaks 40-43 individuals x m(-2) and 13-14 families x m(-2), respectively. When the Mg2+ and HCO3- concentrations increased further, the abundance and group richness decreased.