Herb layer response to broadleaf tree species with different leaf litter quality and canopy structure in temperate forests

Question: How do broadleaf tree species affect humus characteristics, herb layer composition and species diversity through their leaf litter quality and canopy structure? Location: Mixed broadleaf forests in Brandenburg, NE Germany. Methods: We studied the herb and tree layer composition in 129 undisturbed stands using a 10‐degree cover‐abundance and percentage scale, respectively. The main floristic gradients were extracted by non‐metric multidimensional scaling. Effects of tree species on the herb layer were analysed with partial Spearman rank correlation. We assessed affinities for specific tree species using indicator species analysis. Results: Both beech and oak influenced herb layer composition mainly through their litter quality, which resulted in deep Ol and Of horizons, respectively. The less dense canopy of oak, in contrast to the dense beech canopy, enhanced species diversity in favour of indifferent herb species (species not closely tied to forests). Lime was correlated with a distinct floristic gradient, but a direct effect on the herb layer cannot be proven with the available data. Effects of hornbeam were less pronounced. Conclusions: The relationship between the tree and herb layer must be partly attributed to pH differences. However, tree species effects on humus characteristics and on light flux to the ground were largely responsible as well. The results suggest that tree species can influence herb layer composition and diversity, but the missing correlation with lime and hornbeam raise questions requiring further detailed investigation.     

Anatomical study of zygotic and somatic embryos of Tilia cordata

A comparative anatomical study was carried out on zygotic and somatic embryos of Tilia cordata Mill. to evaluate the effect of growth conditions on their development. Zygotic embryos (heart-shaped, torpedo, cotyledonary), collected during two autumn periods, were examined to investigate the effect of growing season on embryo development. In comparison, the influence of growth conditions on the development of somatic embryos in vitro was also studied. Treatment with abscisic acid (ABA) and polyethylene glycol-4000 induced the development of somatic cotyledonary embryos similar to zygotic embryos with respect to morphology and anatomy, as illustrated by the differentiation of the apical meristems and of the procambium. The pattern of accumulation of starch and protein was also similar in these embryos. Somatic cotyledonary embryos that developed spontaneously without ABA showed defective accumulation of storage material and a general failure to form the shoot apical meristem, leading to very low germination rates. Vacuolar phenolic deposits were observed along the procambium of both zygotic and somatic embryos regardless of the maturation stage. Tracheid formation was observed only in somatic embryos formed without ABA in the medium and in precociously germinated somatic embryos. Phenolic vacuolar inclusions were frequently observed in epidermal cells of these embryos. This revised version was published online in June 2006 with corrections to the Cover Date.     

Anatomical and morphological characterization of mycorrhizas of five strains of Tuber borchii Vittad

 Tilia platyphyllos Scop. plantlets were inoculated in vitro with five Tuber borchii Vittad. strains (1BO, 17BO, 43BO, 71BO and 10RA) to test their intraspecific variability. The ability of the strains to form mycorrhizas varied, with the mean degree of ectomycorrhizal infection ranging from 50.6% (for 1BO) to 82.1% (for 10RA). The anatomical/morphological characteristics of the resulting mycorrhizas were determined. Although the morphological features of the mycorrhizas and the characteristics of the cystidia were similar for all strains tested, differences were found in the anatomical features of the mantle. The form of the mantle cells was examined in the surface and inner layers (6 and 12 μm deep, respectively) by both conventional and confocal microscopy. These cells were polygonal in 1BO, and 71BO, epidermoid in 43BO and intermediate in 17BO and 10RA. The structure of the mantle also varied and thus provided little information with which to identify T. borchii mycorrhizas. Accepted: 7 July 2000     

长白山红松阔叶混交林紫椴枝条的分解实验

研究了长白山北坡椴树（Tilia amurensis）枝条的分散进程,实验结果揭示,分解率是与各实验地的植被类型,海拔,生长季月平均大于5℃的积温等密切相关。其枝条分解的保存率（Y）与分解年龄（x）的相关,可用指数模型：Y＝e^-kx来拟合,在红松阔叶混交林,红松外叶混交林,岳桦去冷杉林及岳桦林中椴树枝条分解常数K分别为－0.168与－0.127,－0.102和－0.094。枝条原重量50％的分解年龄在上述4个森林中分别是4,5,6和7a。实验还指出,在长白山红松阔叶混交林皆伐迹地的实验条件下适当的蔽荫和浇水对分解有正面影响。而且,枝条的分解率主要是以长白山不同海拔植被类型的温度条件而转移,特别是生长季的积温。     

Thermal constraints on activity patterns in nectar-feeding insects

ABSTRACT.

• 1 All the insects visiting Tilia and Heracleum flowers showed diel patterns of activity, which could best be explained in terms of weather. Of the recorded parameters, solar radiation gave the best correlations with activity.
• 2 Correlations between activity and radiation depended on the size and colour of particular groups of insects; small bright species visited fully insolated flowers, (r high), while large dark forms visited early and late in the day (r low or negative).
• 3 Consequently mean reflectance and mean weight of foragers showed consistent trends through a day and predictable relations with radiation for both flowers, suggesting that thermal costs are a critical determinant of feeding times.
• 4 By contrast, the nectar reward (as sugar amounts) in flowers was poorly correlated with timing of insect visits, indicating that caloric reward is not limiting; although nectar concentration (only measurable for Tilia) did correlate reasonably well with total visitation.
• 5 The exception to this pattern was Bombus. This endothermic species visited early in the day when nectar was abundant. Thus visits correlated well with reward and negatively with radiation, showing a dependence on high rewards to offset thermoregulatory metabolic costs.
• 6 For most insects foraging appeared to be largely determined by the visitors thermal requirements and the restrictions imposed by avoidance of overheating. Nectar rewards were not critical, and nectar concentration, itself dependent upon climatic parameters, was probably only incidentally correlated with diel patterning for all but the largest (endothermic) insects.

     

蒙椴树皮化学成分的研究

为研究蒙椴（Tilia mongolica Maxim.）树皮的化学成分,通过溶剂萃取、硅胶柱色谱、重结晶分离纯化,从蒙椴树皮中分离得到7个化合物,根据其红外光谱、质谱和核磁共振谱数据鉴定为β-香树脂醇乙酸酯（1）,计曼尼醇乙酸酯（2）,羽扇豆醇（3）,二十四碳酸（4）,三棕榈酸甘油酯（5）,β-谷甾醇（6）,胡萝卜苷（7）。其中化合物1-5、7均为首次从椴树属植物中分离得到,化合物6为首次从该植物中分离得到。     

长白山地区不同海拔紫椴枝叶解剖构造比较分析

利用常规石蜡切片法,光学显微镜观察,对长白山地区不同海拔紫椴枝叶解剖构造进行观察并比较分析。结果表明：从600～1100 m范围内紫椴的生长情况良好;紫椴一、二年生枝条和叶片的解剖构造都随海拔的升高呈现一定变化规律;海拔的变化对枝叶不同解剖构造影响不同;综合观察,700～900 m之间应为紫椴在长白山地区的最适宜生长的海拔高度。