栎属和青冈属的新组合(英文)

<正> 1. Quercus aliena B1. var. pekingensis Schott. f. alticupuliformis (Liouet S. X. Li)H. W. Jen et L. M. Wang comb. nov.—Q. aliena B1. var. jeholensis Liou et S. X. Li in F1. Lign. N. -E.Chin. 219. 1955. —Q. aliena B1. var. alticupuliformis H. W. Jen et L. M.Wang in Bull. Bot. Res. 4 (4):197. f. 3. 1984.2. Quercus serrata Thunb. var. tomentosa (B. C. Ding et T. B. Chao)Y. C. Hsu et H. W. Jen comb. nov.—Q. glandulifera B1. var. tomentosa B. C. Ding et T. B. Chao F1.Honan 《河南植物志》 1:248. 1981.3. Quercus senescens Hand. -Mazz. var. muliensis (Hu)Y. C. Hsu etH. W. Jen comb. nov.     

Determination of amino acids from the leaves of evergreen oak (Quercus ilex L.) at four different stages of decomposition

Summary It was established by weak ion exchange resin chromatography that 17 amino acids in proteins and 15 free amino acids account for almost all of the amino acids present in the leaves of evergreen oak (Quercus ilex L.) in four different stages of decomposition. No significant change in the amounts of these amino acids was observed in the course of decomposition. The amino acid content of evergreen oak leaves is comparable to that in pine needles and beech leaves.     

杨梅根瘤Frankia菌对重金属的抗性

采用生长抑制分析法研究从杨梅根瘤分离的10个Frankia菌菌株对9种重金属元素的抗性。一般所有供试菌株对Hg^2 和Ag^ 敏感，大部分菌株对Pb^2 (5～10mmol／L)、Cr2O7^2-(5～10mmol／L)、AsO2^-(5～10mmol／L)不敏感，部分菌株对Cu^2 、Co^2 、Ni^2 和Cd^2 也不敏感(MICs≥O．5mmol／L，有的菌株达到5mmol／L)。菌株之间对各种重金属的抗性存在较大差异，其中菌株Mda21对所有供试重金属都敏感，而菌株Mpall几乎能抗所有供试重金属，且有几个菌株能同时抗多种重金属。低浓度铅能促进抗铅菌株的生长，而高浓度铅对其生长有一定的抑制；抗铅菌株在含铅的培养基中仍具有固氮酶活性，在一定浓度范围内，随铅离子浓度的升高，固氮酶活性有所增强。Frankia菌的抗铅机理可能是其具有结合或螯合铅离子作用，对其他重金属的抗性机制尚不清楚。     

Fire-vegetation interplay in a mosaic structure of Quercus suber woodlands and Mediterranean maquis under recurrent fires

We examined the effects of fire recurrence on a mosaic structure of Quercus suber and Erica-Cistus shrubland communities of Southeastern France in order to improve the understanding of fire-vegetation interplay. Plant communities that were similar in 1959 (woodlands on shrublands called maquis on acidic soils) were compared along a gradient of fire recurrence, from 0 to 4 fires, with different time intervals between fires. The results showed that understory cover increased roughly with fire recurrence, whereas tree height, cover, density, stand basal area and litter depth decreased. Different fire recurrences along the past decades led to different vegetation types. High fire recurrence corresponded to maquis and sparse cork-oak woodlands while pure oak woodlands established in the absence of fire during the same period. In all, the diversity of tree diameter decreased with fire recurrence. High fire recurrence (3 or 4 fires in 50 years) led to a simple vertical structure of vegetation with a mono-layered shrub cover and few Quercus suber trees. In contrast, spatial connections between plants were maximal at longer time intervals, leading to a multi-layered vegetation. We finally discuss the potential implications of past fires on the behavior of future fires in the perspective of a sustainable management of these Mediterranean ecosystems.     

Drought and fire suppression lead to rapid forest composition change in a forest-prairie ecotone

Altered fire regimes and increased drought can lead to major vegetation changes, especially in ecotones. A decrease in fire can lead to woody species encroachment in prairies and increasing forest stand density. The threat of global climate change raises questions about potential increases in the length, severity, and incidence of droughts substantially altering species composition. Re-measured upland forests in south-central North America's midcontinent forest-prairie ecotone exhibited major changes in woody species composition and structure over fifty years and successional trajectories appeared to favor invasive Juniperus virginiana L. over the previous dominant Quercus species. The objective of this study was to determine whether climate and fire exclusion affected the recruitment history of dominant woody species in these upland forests located near the xeric western edge of the eastern deciduous forest biome of North America. We removed cores and cross-sections from 992 J. virginiana, Quercus marilandica Münchh. and Q. stellata Wangenh. trees from eleven forest stands located across central and northwest Oklahoma, and determined their ages using standard dendrochronological methods. Recruitment of all species increased following a severe mid-20th century drought, but a rapid increase in J. virginiana recruitment and decrease in Quercus recruitment appeared to be linked to a decrease in fire. Future fire regime changes and increased drought due to global climate change could lead to widespread shifts from Quercus- to Juniperus- dominated forests and cause substantial changes to ecosystem services.     

北京地区栓皮栎地上部分生物量的研究

以北京地区栓皮栎人工林为研究对象,应用典型样地调查法和相对生长法对乔木生物量展开研究,结果显示：各器官中生物量大小顺序为树干〉枝条〉叶片,其中树干约占65%,树冠约占35%。通过回归分析探讨了各变量的相关性,并对其各器官的生物量与胸径和树高进行模型拟合。其中树干和树冠的生物量与胸径、树高的拟合方程分别是：W=0.018（D2H）1.09、W=0.9（D）2.128。     

元宝枫栓皮栎苗木水力结构特征的对比研究

元宝枫(Acer truncatum)是散孔材树种,栓皮栎(Quercus variabilis)是环孔材树种,为了解二者在水分运输和耐旱机理方面的特点,该文应用水力结构的基本理论,在正常水分条件下,用改良的冲洗法测定4年生元宝枫、栓皮栎苗木各部位的水力结构参数. 实验和模拟的结果表明,元宝枫和栓皮栎苗木都存在限速区;在非限速区,二者各部分木质部的导水率、比导率、叶比导率和胡伯尔值都随功能木质部直径的增加而增大,但表现出不同的变化趋势,这些变化较好地说明元宝枫和栓皮栎苗木耐旱的生态策略. 在功能木质部直径相同的情况下,栓皮栎苗木的各水力结构参数均较元宝枫苗木大.     

栓皮栎磷素营养动态及转移规律

对45年生栓皮栎磷素营养动态及转移规律进行了研究，结果表明：栓皮栎树干、枝、叶、皮、根等器官中的磷素含量均随季节发生变化，且幼嫩组织变化幅度较老组织大。栓皮栎树叶在凋落前转移出的磷为9.542kg/hm^2，占地上部分转移总量的52.57％；树干每年迁入磷素高达6.909kg/hm^2。根系生长过程中，磷素含量出现锐减而形成的含量曲线呈“V形谷主”，该“V形谷”可作为林木营养诊断和合理施肥的重要参考。     

Protected wading bird species threaten relict centenarian cork oaks in a Mediterranean Biosphere Reserve: A conservation management conflict

Conservation management conflicts frequently arise when an overpopulation of a protected organism has negative effects on other valuable elements in the same ecosystem. We studied the interactions between a colony of protected tree-nesting wading birds and a remnant population of centenarian cork oaks that was part of the formerly dominant forests in the Doñana Biological Reserve (SW Spain). A significant increase in the tree mortality rates has been recorded in areas that are yearly influenced by the bird colony.We analysed a cohort of surviving trees using a gradient of nesting bird influence. Tree-nesting history, bird isotopic signature (δ¹⁵N), tree health-related parameters (defoliation, δ¹³C and leaf surface coverage by faeces) and several soil variables were evaluated. Bird influence was related to increased soil salinity. This increase correlated to increased water-use efficiency for the leaves and to crown defoliation, suggesting that the heavily occupied trees are under higher stress and in poorer health condition than the unoccupied ones. We tested structural equations models (SEM) that were based on hypothesised bird effects on the health of the trees. Soil-mediated effects of the nesting birds best explained the symptoms of the declining health of the trees, whereas the percent of leaves’ surface that was covered by faeces did not improve the fitted SEM model.For the reserve’s managers, a challenging trade-off exists between preserving the relict trees, which have a high genetic diversity and a key ecological role in these savannah-like ecosystems, and maintaining the current nesting area for these protected, but expanding, wading birds.