Nitrogen Isotope Ratios in Different Compartments of a Mixed Stand of Spruce,Larch and Beech Trees and of Understorey Vegetation Including Fungi

Abstract

Natural nitrogen isotope ratios were measured in different compartments (needles or leaves and twigs of different age classes and crown positions, roots and soil of different horizons) of spruce (Picea abies), larch (Larix decidua) and beech (Fagus sylvatica) trees in an 11-year-old mixed stand in the Fichtelgebirge, NE Bavaria, Germany. In addition, samples of understorey vegetation (mainly ericaceous shrubs and grass) and of ectomycorrhizal and saprophytic fungi were analyzed. The δ¹⁵N values found for all samples ranged between ?7.5 and + 4.5‰. No significant differences were found for the nitrogen isotope ratios of the three tree species despite of their evergreen versus deciduous foliage and despite of their different rooting depth. Ericaceous shrubs had the most negative and fungi and soil from the mineral horizon the most positive δ¹⁵N values. Positive δ¹⁵N values of the fungi indicate their ability to utilize organic soil nitrogen, but the data do not unequivocally show that plants forming mycorrhizas profit from this organic nitrogen source.     

光头山南坡的灌木研究

对光头山南坡的灌木采用直接观察法统计并进行分析,结合该地区生境特点得出结论,为有效保护该区域提出具体措施.     

水土保持乔灌混交林N、P养分循环的研究

福建省长汀县河田镇是我国南方红壤区水土流失最严重的地区之一。通过对长汀河田严重侵蚀地采取乔灌木混交治理近20a后林分N、P养分循环的研究，结果表明，乔灌木混交林乔木层地上各组分的N、P含量大小均为叶＞皮＞枝＞干，根系的N、P含量则随径级的减少而增大，乔灌木混交林各组分的N、P含量均比对照的高。混交林林分的N、P总累积量达339.200和2.088/hm^2，分别是对照的100.6倍和69.6倍，其乔木层的N、P积累量分别占林分的93.0%和93.6%；乔灌木混交林苔藓层的养分积累量高于草本层和灌木层。乔灌木混交林的N年存留量、归还量和吸收量分别是对照的33.6、25.9和30.3倍。而P的则分别是对照的81．4倍、35．9倍和63．4倍，乔灌木混交林中乔木层、灌木层、草本层和苔藓层等在N、P养分循环中发挥较好的作用，对退化土壤肥力恢复起到十分积极作用。     

Chemical and Bioactive Characterization of the Essential Oils Obtained from Three Mediterranean Plants

Cupressus sempervirens L., Juniperus communis L. and Cistus ladanifer L. are Mediterranean arboreal and shrub species that possess essential oils (EO) in their leaves and branches. This study aimed at characterizing the EOs obtained by steam distillation from the three species collected in different locations from Spain (Almazán, Andévalo, Barriomartín, Cerezal, Ermitas and Huéscar). For this purpose, volatiles composition was determined by GC-MS, and different bioactivities were evaluated. The highest content in terpenes was observed in C. sempervirens (Huéscar origin) followed by J. communis (Almazán origin), corresponding to 92% and 91.9% of total compounds, respectively. With exception of C. ladanifer from Cerezal that presented viridiflorol as the most abundant compound, all the three species presented in common the α-pinene as the major compound. The EOs from C. ladanifer showed high antibacterial potential, presenting MIC values from 0.3 to 1.25 mg/mL. Concerning other bioactivities, C. ladanifer EO revealed an oxidation inhibition of 83%, while J. communis showed cytotoxicity in the MCF-7 cell line, and C. sempervirens and C. ladanifer EOs exhibited the highest potential on NCI-H460 cell lines. Nevertheless, some EOs revealed toxicity against non-tumoral cells but generally presented a GI₅₀ value higher than that of the tumor cell lines.