Composition and characteristics of natural secondary forests in Shenzhen,South China

The composition and structure of five natural secondary forests in Shenzhen were studied based on data of plots and were compared with Hong Kong zonal forest, so as to detect their succession stage and species diversity level. According to succession process of subtropical forest and ecological characteristics of dominant species, the authors speculate that five communities are at different stages. Sinosideroxylon community dominated by heliophilous evergreen broad-leaved tree (Sinosideroxylon wightianum) and conifer tree (Pinus massoniana) is at the third stage. Itea Acronychia community dominated by two evergreen broad-leaved heliophytes (Itea chinensis and Acronychia pedunculata) is at the fourth stage. The others, i.e., Schefflera,Sterculia and Cleistocalyx Sterculia community are at the fifth stage where some mesophytes are dominant but heliophytes have a weighed percentage of importance value. Due to succession stage and different forest management and conservation models, the species diversity of five communities is significantly lower than that of Endospermum community in Hong Kong. The values of Shannon-Wiener index and Pielous evenness index of five communities are 2.04-2.953 and 64.2%-74% respectively, but those of the Endospermum community are 4.74 and 79％ respectively. The current situation of these communities suggests that the necessary measures should be taken to protect and restore the communities.     

民勤少区主要植物的物候特征

选择在民勤沙区有代表性的48种植物,利用1985--2004年的观测资料,先就48种植物的9个主要物候期按平均期距进行系统聚类,进而对聚类结果按中生、旱生和沙地旱(中)生植物归并为类群.研究结果表明:从中生植物到旱生植物再到沙地旱(中)生植物,同一物候期的多年变幅增大;从旱生植物到沙生植物的物候期的多年变幅大于从中生植物到旱生植物的多年变幅;不同植物的物候期差异主要表现为从花蕾花序期开始到果实脱落末期的各个物候期,从中生植物到旱生植物再到沙地旱(中)生植物,这些物候期表现出逐渐延迟的趋势;当地冬季漫长,夏季持续日数较长,秋季最短,春季和秋季物候频数分布较多,植物活动日数相对较短;运用聚类分析方法研究包括中生植物、旱生植物和沙地旱(中)生植物的物候特征,能更好的从不同植物类型来揭示植物物候特征.     

牛蒡叶解剖结构的研究

采用石蜡切片的方法,对牛蒡叶的解剖结构进行了研究。结果表明,牛蒡叶为典型异面叶。上表皮具极少的表皮毛和多数棒状的粘液毛,气孔数较下表皮少,气孔与表皮细胞平齐,同时存在拱起气孔;下表皮密被绒毛。叶肉有栅栏组织和海绵组织之分,两者厚度比为5∶3,栅栏组织2层。中脉具3个维管束,小脉外具一层维管束鞘,具有典型的C4植物特征。     

大兴安岭林区野生榛子驯化栽培技术

内蒙古大兴安岭林区位于自治区东北部,最高海拔1745.2米,最低海拔268米。年平均气温-2℃左右,极端最低气温-52℃,无霜期76~120天;年降水量350~500毫米。一、野生榛子概况野生榛子即平榛(Corylus heterophylla Fisch ex Bess),属中生植物,主要生于山坡、山岗或柞树林间的阳坡或平地上。具有喜光、抗寒、适应性强、根蘖繁殖能力极强等特性。