Old-field colonization by Daphne gnidium: seedling distribution and spatial dependence at different scales

Abstract. This paper deals with the spatial distribution pattern of the bird-dispersed plant Daphne gnidium in a 10-yr abandoned field under Mediterranean conditions. Colonization of Mediterranean old-fields by bird-dispersed plants is expected to fit a theoretical model in which (1) seed dispersal follows a negative exponential curve with the distance from the seed source and (2) seedlings are better established under perches (nucleation sensu Yarranton & Morrison 1974). However, post-dispersal processes such as seed predation, seed germination and seedling establishment are also spatial-dependent and can lead to spatial autocorrelation in the seedling distribution within an old-field. Results show that both processes in the model (curve of seed dispersal and nucleation) significantly explained the spatial distribution of the seedlings, but some spatial variance remained unexplained. The semivariogram with the statistical residuals of the model detected spatial dependence at small (< 20 m) and large (> 250 m) distance intervals, indicating that some mechanisms with spatial components, apart from the curve of seed dispersal and nucleation under perches, also determined the distribution of seedlings colonizing fields. At scales below 20-m intervals, semivariance increased indicating that similarity between plots is lost when distance increases between them. This pattern may be explained because the favourable micro-environmental conditions for establishment produced under perches could be extended towards neighbour plots where perches were absent. A flat semi-variogram between 20-m and 250-m intervals shows spatial independence along this range. From 250 m on, the semivariance increased again, indicating spatial dependence at coarse-scale. It is possible that the colonization model failed at this scale because different spatial processes to those included in the model (perch presence and distance to the shrubland) could be controlling seed colonization at coarse-scale.     

关于蒙古绣线菊毛枝变种及回折绣线菊的学名订正

支持将蒙古绣线菊毛枝变种提升为种的等级且于宁夏绣线菊同种,但其合法学名应为Spiraea tomentulosa(Yu)Y.Z.Zhao。与此同时,本文发现了真正的蒙古绣线菊的毛枝变种--S. mongolica Maxim.var.pubescens Y.Z.Zhao et T.J.Wang。     

Kulikovskiyia gen. nov. (Bacillariophyceae) from the lateritic rock pools of the Western Ghats,India and from Hainan Province,China

A new triundulate naviculoid diatom genus is described from the Western Ghats of Peninsular India and Hainan Province, China. The new taxon, Kulikovskiyia gen. nov. has robust conical spines along its margin and at the apices and the external valve face has longitudinally‐oriented siliceous slat system extending the length of the valve. The external distal raphe ends bifurcate and terminates on the valve face. There appear to be superficial similarities between this Asian genus and species and Playaensis, a genus comprised of two species found only in the western USA. The systematic position of Kulikovskiyia is discussed, and other than noting its similarities to other biraphid naviculoid diatoms due to symmetry features and the position of the raphe, we are uncertain about its systematic placement at finer levels of classification.     

领春木体细胞胚胎发生及植株再生

以领春木（Eupteleapleiospermum Hook．f.etThoms．）种子幼胚为试验材料,对领春木体细胞胚胎发生进行了研究。结果表明：在附加1．0mg·L-1 2,4．D＋0．5mg·L-1 6-BA＋3％蔗糖＋0．8％琼脂的Ms培养基上可诱导出愈伤组织。愈伤组织在附加0．5mg·L-1 NAA＋0．5mg·L-1 6．BA的培养基上可形成体细胞胚;体胚在附加0．5mg·L-1 6-BA＋0．05mg·L-1 NAA＋0．1％PVP的1／2MS培养基上能大量增殖;将成熟体胚转移到不添加任何植物生长调节剂的MS培养基上,培养60d,形成正常植株。     

濒危植物大果木莲种群格局及濒危原因分析

采用径级结构代替年龄结构以及方差均值比率法对木兰科(Magnoliaceae)木莲属(Manglietia Bl.)濒危植物大果木莲(Manglietia grandis Hu et Cheng)种群的年龄结构和种群格局进行了研究,并编制了大果木莲种群的特定时间生命表和存活曲线;结合生殖生物学特征以及遗传多样性研究结果,分析了导致大果木莲濒危的主要原因.根据株高和胸径可分别将大果木莲种群的年龄结构分为5级、高度结构分为6级;在大果木莲的5个年龄结构分级中,成年个体较多,幼年个体较少;其高度结构完整,个体高度主要在20 m以下.种群的方差均值比率为0.838 3,其空间分布格局属于随机分布.根据特定时间生命表可将大果木莲种群的发育分为3个阶段:幼树阶段(年龄级为Ⅱ～Ⅲ级)、成树阶段(年龄级为Ⅲ～Ⅳ级)、老树阶段(年龄级为Ⅳ～Ⅴ级),其中成树阶段个体死亡率最低.大果木莲种群存活曲线接近Deevey Ⅰ型,属于衰退型种群.种群自我更新能力差、种子生产力低下、有性生殖困难、生境片断化导致的基因流受限以及人为干扰是大果木莲濒危的主要原因.针对大果木莲濒危现状和致危原因,提出了相应的保护对策和建议.     

化香树果序总黄酮提取动力学研究

以化香树果序为原料,60%的乙醇水溶液为溶剂提取黄酮类化合物,在不同温度下对总黄酮的传质动力学进行了研究。采用平板模型,以Fick第二定律为基础,建立了化香树果序总黄酮提取的动力学方程,求得了速率常数、活化能、相对萃余率等一系列动力学参数。研究结果可为化香树果序总黄酮提取工程放大和深入理论研究提供一定的依据。     

巧花兜兰——越南中部兰科一新种

在今年年初的一次访问云南南部的旅行中,笔者曾购得数苗小型的兜兰,据兰商称系采自越南中部,又叫越南黄花仔。此种兜兰的叶甚似小叶兜兰ＰａｐｈｉｏｐｅｄｉｌｕｍｂａｒｂｉｇｅｒｕｍＴａｎｇｅｔＷａｎｇ和海伦兜兰Ｐａｐｈ.ｈｅｌｅｎａｅＡｖｅｒｙａｎｏｖ,但花却有着明显的不同。小叶兜兰的花大,直径达5.5～7ｃｍ;合萼片狭窄,其宽度仅为中萼片的1/2～3/5。海伦兜兰花纯黄色;花瓣线形或宽线形。而此种兜兰的花直径3～3.5ｃｍ,呈淡黄绿色,唇瓣表面、合萼片中脉下半部和花瓣的中脉及中脉上方一侧均有枣红色晕;合萼片宽度为中萼片的4/5;…     

Germination and regeneration mechanisms in Mediterranean degenerate forests

Abstract. Germination and developmental behaviour during juvenile stages are of importance in relation to succession mechanisms acting on plant communities. This is particularly so in the Mediterranean region, where the climatic summer drought causes stress. We investigated and compared germination and development of four tree species in two parts of the French Mediterranean region where the original dominant tree species (Quercus pubescens) has been largely replaced by Quercus ilex in the southern part, and Castanea sativa in the northern part. Observed differences in germination rates and developmental behaviour, especially shootroot ratio and the role of water supply, suggest that other species may eventually replace the current dominant species.     

A vegetation analysis of the pastoral landscapes of upland Wales,UK

Abstract. The upland moorlands of Wales are situated on the oceanic fringe of western Europe, and have experienced a long history of pastoral management. Recent vegetation data are analysed to assess the relative contribution of abiotic and anthropogenic factors to variation in habitat composition among the major upland ranges of this region. From a numerical analysis of plant community cover data, recorded from 65 sites covering 260 000 ha, a six‐cluster site classification emerged with striking biogeographical coherence. Direct gradient analysis and variance partitioning revealed strong correlation between vegetation composition and spatially‐structured climatic gradients, in particular temperature, rainfall and oceanicity; differences in bedrock geology appear to have a lesser role. The analysis also indicates a close correlation between habitat variation and anthropogenic parameters, especially grazing intensity, burning frequency, and sulphur and nitrogen deposition levels. At this regional scale, anthropogenic impacts appear to have accentuated, rather than obscured, vegetation patterns which are primarily determined by climate and other abiotic variables. The findings have considerable relevance for conservation planning and also for predictive studies on the consequences of climatic change for the biota of the uplands of southern Britain.     

天目山山胡椒不同部位内生真菌组成及多样性分析

采用表面消毒法,从浙江天目山野生山胡椒[ Lindera glauca( Sieb.et Zucc.) Blume]的茎、叶和树皮中分离出内生真菌,基于ITS序列分析进行分类鉴定;并以内生真菌的分离率、定殖率、分离频率、多样性指数(H')及相似性系数为指标,分析了山胡椒内生真菌的菌群组成及多样性.结果显示:在26株山胡椒样株的728块组织块中共分离得到328株内生真菌(茎、叶和树皮中分别有161、40和127株);共鉴定出44个分类单元(茎、叶和树皮中各有19、18和28个),其中25个分类单元鉴定到种、17个鉴定到属、2个鉴定到科,ITS序列的GenBank登录号从JF502420至JF502462.在44个分类单元中,有40个分类单元属于子囊菌(310株),存在于山胡椒的各个部位;仅有4个分类单元属于担子菌(18株),且仅存在于茎和树皮中.山胡椒茎、树皮和叶中内生真菌的定殖率分别为65％、60％和15％,分离率分别为0.77、0.61和0.19;叶和树皮中内生真菌的多样性指数均为2.63,远大于茎(H’=1.83).山胡椒内生真菌的优势属为Phomopsis、Paraconiothyrium、Phoma和Colletotrichum,大量存在于叶、茎和树皮中.山胡椒茎与树皮、茎与叶及叶与树皮间内生真菌的相似性系数分别为0.27、0.19和0.18,显示树皮和叶之间以及树皮和茎之间内生真菌的组成极不相似.研究结果表明:山胡椒体内存在大量的内生真菌,其茎、叶和树皮的内生真菌菌群组成具有一定程度的多样性和差异性,且内生真菌的分布具有组织特异性.