土壤盐碱化程度及非毛管孔隙度对羊草群落生物量及优势度的影响

通过对不同盐碱化土壤上的羊草群落进行及定位连续观测，分析了它和土壤盐碱化程度及非毛管孔隙度之间的相互关系，探讨了盐碱生境下羊草群落生物量的形成规律以及土 盐碱化程度对其影响，结果证明，盐碱生境对羊草群落在一个生长季内的生物量形成过程无本质影响；群落的生物量随返青后天数增加而呈S型曲线上升，二者间的数学关系可用修改的Logistic方程Y＝Y m/1 Ae-bx C描述。土壤盐碱化程度可影响该方程的各参数，随土 盐碱化程度加剧，生物量最大增长值Ym和本底生物量C明显变小，到达S型曲线拐点的天数减少，羊草群落生态优势度随土壤盐度增大呈倒S型曲线下降，随土壤非毛管孔隙度增大而呈正S型曲线上升，三者之间的回归分析结果表明，土壤盐度和非毛管孔隙度都是影响优势度的不同忽略的重要因素，但前者的重要性大于后者。用方程可获得最佳拟合结果及3个生态因子相互关系的总体模型。

EFFECTS OF SOIL SALINIZATION AND NONCAPILLARY POROSITY ON THE BIOMASS FORMING AND ECOLOGICAL DOMINANCE OF LEYMUS CHINENSIS COMMUNITY

The biomass forming law of Leymus chinensis community in salinized habitat and the effects of the soil salinization extent were explored by investigating the L. chinensis communities growing on the soil with different level of salinization, and continually monitoring at fixed sample plots, and then the relationship among soil salinization extent, noncapillary porosity the biomass and ecological dominace of the L. chinensis community were analysed. The results showed that no essential change appeared in salinized habitat for the biomass forming process of L. chinensis community during a whole growing season. The biomass of the community was increasing with as-shaped curve as the number of days increased after turning green. The mathematical relation between them both could be expressed by a modified logisticformula Y . The different salinizatiton extents of soil madesome changes of parameters in the formula. As the salinization of soil became serious, Ym (maximum increment of biomass allowed by environment) . and C (background biomass at the start, of turning green) became smaller,the number of days reaching the point of Y = Ym/2+ C tended to decrease.The dominance of L. chinensis community was decreasing with an inverse S-shaped curve as the natural logarithm of salinity was increasing, and was increasing with a S-shaped curve as the noncapillary analysis showed that the salinity and noncapillary porosity of soil were the all important factors affecting the dominance which, should not be neglected but the effect of salinity was greater than that of noncapillary porosity. A perfect result of regression and a mathematical space model of the threa factors were gained byusing a formula Y = .