<正>应用Levins和Shannon-weiner生态位宽度指数，以及Pianka生态位重叠指数、简化Morisita生态位重叠指数对晋西黄土区和土石山区交错地带29个主要灌木树种的生态位特征进行了研究，并对各树种的DCA排序分析结果与生态位特征进行了对比分析。结果表明：1灰栒子Cotoneaster acutifolius、土庄绣线菊Spiraea pubesceus、黄刺玫Rosa xanthina等物种的生态位宽度明显大于其他物种。2多数灌木种之间存在较小的生态位重叠，只有少数种对间生态位重叠值较大。以Pianka生态位重叠指数为例，406个种对之中，有116个种对间不存在生态位重叠，占总种对数的28.57％；指数值在0～0.5间的种对数为276对，占总种对数的67.98％；指数值在0.5～1时种对数只有14对，仅占总种对数的3.45％。3物种DCA排序图第一轴反映了各物种分布生境的水分条件。对比分析表明，生态位宽度小的物种多位于DCA排序图的边缘区域，而生态位宽度较大的种则多位于排序图的中心区域。

Biodegradable nanocomposite is one of the next generation materials. Cellulose fibrils in micro and nano scales, which are environmentally friendly and have potential lightweight and high strength, can be used to make biodegradable nanocomposites. The purposes of this research were to characterize the fibrils isolated from Lyocell fiber by a novel mechanical process and to discover weather the fibril reinforced biodegradable nanocomposites yield greater mechanical properties. The geometrical characteristics of the fibrils were investigated using polarized light microscopy (PLM) and scanning electron microscopy (SEM), and their crystallinity was investigated by wide angle X-ray diffraction (WAXD). The degree of fibrillation of the fibers is evaluated by water retention value (WRV). Fibril-reinforced nanobiocomposites, consisting of a biodegradable polymer (PLA) and fibrils were prepared by compression molding, evaluated by tensile test, and their morphological characteristics were investigated with SEM. The fibrils increased both tensile modulus and strength of polymer matrix, but a poor adhesion between fibrils and the matrix was still observed by SEM.