Habitat specialists and generalists drive homogenization and differentiation of temperate forest plant communities at the regional scale

In European temperate forests, changes in the compositional similarity among local plant communities (beta diversity) have rarely been studied due to the lack of adequate baseline data. Several studies, however, report the spread of common, generalist species or a decline in specialized, rare species. Both processes may lead to increased similarity among communities, i.e., biotic homogenization.To quantify changes in beta diversity, we resampled the herb layer composition of ancient broadleaf forests at 175 semi-permanent plots distributed across the Weser-Elbe region in NW Germany 20 years after first sampling. We hypothesized that beta diversity would have decreased on average as a result of a spread of habitat generalists and a decline in habitat specialists.After two decades, the forest communities did not yet exhibit severe biotic impoverishment, although there was a broad trend towards homogenization. The actual magnitude of change depended on which beta diversity measure was applied. The downward trend was primarily the result of the spread of native species that are able to tolerate broad pH and moisture ranges. A distinction between forest specialists (closely tied to forest habitats) and generalists (also found in open habitats) did not help explain changes in beta diversity. The study shows that on the regional scale and in habitats not yet threatened by the invasion of alien species, shifts in native species can promote biotic homogenization.     

阳泉市草本花卉引种栽培试验

本试验对内蒙赤峰市产的万寿菊、孔雀草、百日草、串红、鸡冠、矮牵牛和北京产的一、二级品质的串红、鸡冠、千日白共9个草本花卉品种在阳泉市进行了引种栽培试验。结果表明,9个品种在阳泉市引种栽培,可用于商品盆花生产和城市绿化美化。通过试验提出了相应的播种基质、种子处理、育苗管理方法和关键技术,并提出今后推广栽培和进一步引种试验的建议。     

两种石蒜中酯酶和苹果酸脱氢酶酶谱分析

对2种石蒜用3种方法提取酶液,采用聚丙烯酰胺凝胶电泳进行酯酶和苹果酸脱氢酶同工酶酶谱分析,同时对提取酶液在白色点滴板上显色.结果表明:从酶谱分析可知,石蒜酯酶有1条谱带,相对迁移率(Rf)为0.17;苹果酸脱氢酶有2条谱带,Rf值分别为0.51和0.69.忽地笑酯酶有1条谱带,Rf值为0.17;苹果酸脱氢酶有4条谱带,Rf值分别为0.43,0.47,0.51和0.69.从显色试验可知,3种提取方法对酶提取的充分性、活性有差异;研磨后,经60%超声的提取方法对酶能够充分提取,而且能更好地保持酶的活性.