台湾中部暖温带阔叶林年轮特征、生长与树龄结构

台湾目前对于阔叶树种的生长轮少有研究,尤其对于天然阔叶林的生长趋势与模型的相关研究更是缺乏,许多资料仍相当不足,有鉴于此,本研究将针对台湾中部地区的典型暖温带阔叶林进行生长轮的研究与探讨。神木溪保护林于2003年已设置完成18个长期观察的森林动态样区,本研究采用第13~18共6个样区内所有胸径大于6 cm之阔叶树,依据林分特征调查结果,钻取大于6 cm胸径林木,钻取高度约在胸径位置,共取得22科33属39种合计448支树芯。年轮分析运用实体显微镜配合CCD拍摄,目视各树种内年轮的变异,并加以分类,作为年轮目视判视与计数年轮的依据,并用Velmax系统量测年轮宽度,应用树冠级模式(CCM)、定期生长量模式(PAI)及混合模式(Mixed)建立各冠层生长趋势,并解析各树种树龄结构,以提供台湾最大面积、分布最广之楠槠及栎林带林分经营之参考。年轮特征上,属于散孔材树种占79%;半环孔材树种占18%;环孔材树种占3%。生长趋势上,所有树种的平均生长速率统计结果为3.53 mm/a。冠层产生垂直层次分化作用明显,显示出其生长的趋势,上主冠层直径增长情形最快,平均生长率为4.47 mm/a;主冠层其次,平均生长率为2.95 mm/a;底冠层速率最慢,平均生长率为2.92 mm/a。PAI模式显示大部分树种的生长趋势是呈现年轮宽度随树龄增加而增加或线性常数的情形。树龄估算以树冠级模式、PAI模式和混合模式3种模式估算,全部平均年龄分别为55、60、59年。混合模式的利用可以降低单独使用树冠级模式或PAI模式的误差率。树龄结构上,依树冠级模式、PAI模式及混合模式龄级分布结果,本样区充满耐阴性树种前生苗与灌木,逐渐形成典型的复层林。树龄出现2种分群,第1种大多为耐阴性树种的小苗,树木建立时间为20世纪后期;第2种在1900年左右形成了1个独立的单峰。年轮不明显区别造成类型分类的困难,轮宽不规则也无法明确定年,PAI模式需要大量的各龄阶树芯数据建立回归模式,所得到的模型才具有足够之代表性,混合模式虽解决了部分树龄推估的误差,但仍有其他问题,因此日后应更进一步进行探讨与分析,方能对森林生态系之永续经营与发展产生一定程度的帮助。本研究提供暖温带阔叶林林分径向生长与树龄结构信息,以供森林收获采伐和森林永续经营参考。      

Comparative morphology of Phytophthora species on rubber

Eighty-nine Phytophthora isolates from rubber throughout the world were examined critically. Five species were distinguished: P. palmivora morphological form I (MF1), P. meadii, P. botryosa, P. citricola, P. citrophthora and one currently designated P. palmivora (MF4). P. citrophthora is reported for the first time from rubber in the Ivory Coast and Indonesia, and mating types are given.     

Pathogenic variability amongst isolates of Crinipellis perniciosa from cocoa (Theobroma cacao)

Dry witches' brooms from cocoa were imported from various areas within Bolivia, Brazil, Colombia, Ecuador, Trinidad and Venezuela. Basidiocarps of Crinipellis perniciosa were induced to form on these brooms and seedlings of different types of cocoa were inoculated with basidiospores either on the hypocotyl or cotyledon bud. Host reactions were assessed mainly by recording stem base swelling and broom development at the cotyledon node (hypocotyl inoculations) or the extent of swelling and branching of shoots (cotyledon bud inoculations).
Results from 30 experiments indicated considerable diversity amongst isolates in inducing disease symptoms, but suggested that two groups or populations of C. perniciosa exist on cultivated cocoa. One group (A), comprising isolates from Bolivia and Pichilingue (Ecuador) and most isolates tested from Colombia, induced severe symptoms on cocoa with Scavina 6 as one parent; the other group (B), comprising isolates from Brazil, Trinidad and Venezuela, did not. Within these groupings variants could be further distinguished by particular host reactions. Isolates from Ecuador, especially from the Oriente, a centre of diversity for Theobroma cacao, showed a range of pathogenicity comparable to that found amongst isolates from cultivated cocoa over a much wider area.     

In vitro effects of temperature and wet periods on infection of oilseed rape by Alternaria brassicae

The influence of temperature and duration of wet periods on infection of oilseed rape by Alternaria brassicae was studied on detached leaves and pods, leaf disks and intact seedlings. Infections increased with age of leaf and the interaction between temperature and leaf age was highly significant. On older leaves infection was optimal at 25°C. There were many infections also at 15, 20 and 29 C but relatively few infections at 10°C. On pods most infections were observed at 20 C, the highest temperature studied. Infection at each temperature increased progressively with duration of surface wetness. The minimum wet periods for infection of leaves were 3 h at 20–25°C, 4 h at 15°C, 6–9 h at 10 C and 12–24 h at 5 C and for infection of pods, between 6 h and 9 h at 10°C and 6 h (or less) at 15°C and 20 C. On leaves, dry periods interrupting wet periods limited lesion development to that obtained with the initial wet period only; on pods some further infections developed when pods were re-wetted. Dry periods of 3 h and 6 h following the inoculation of pods reduced subsequent infection but there was no further reduction by longer periods of drying to 48 h.     

Factors influencing the production of basidiocarps and the deposition and germination of basidiospores of Crinipellis perniciosa, the causal fungus of witches' broom on cocoa (Theobroma cacao)

The production of basidiocarps by Crinipellis perniciosa on detached, dead witches'brooms from cocoa was assessed in relation to temperature, light, cocoa clone, age of broom and type of tissue, in cabinets with a daily cycle of 8 h wet and 16 h dry. More basidiocarps formed and matured at 20–25°C than at 25–30°C. In the latter regime the pilei were smaller and white, instead of the usual crimson colour, and the stipes were longer. No basidiocarps formed at 30–35°C. At 20–25°C. more basidiocarps formed and matured with light at 100 μE m^-2 s^-1 during the wet period than at 10 μE m^-2 s ^-1. Only one basidiocarp and five primordia developed on 20 brooms kept in the dark. Brooms from 10 cocoa clones at Pichilingue. Ecuador, differed in basidiocarp productivity. most basidiocarps forming on brooms from Seavina and least on ICS clones. The numbers of basidiocarps produced on brooms aged 1.2.3 or 4 months when detached from cocoa trees were similar but time to initiation of the first primordium differed considerably. More basidiocarps formed at nodes than internodes.
The discharge of basidiospores was optimal at 20–25°C and 80% RH: germination was optimal in water agar films. Neither process was dependent on light.     

Relationships between establishment of Erysiphe cruciferarum and soluble amino-acids in leaves of Brussels sprouts

The ability of Erysiphe cruciferarum to establish infections on detached foliage and button leaves of two F_l cultivars of Brussels sprouts grown in the field was examined under standard conditions. Consistently more infections developed on Goldmine than on Ulysses. On foliage leaves of both cultivars the numbers of infections fluctuated from week to week but generally increased with time on samples taken from September to December. On Goldmine, more infections developed on the oldest foliage leaves than on those of intermediate position on the stem and only infections on the mature leaves sporulated well. The number of infections increased progressively on leaves further into the sprout buttons of both cultivars. Fungal establishment on foliage and button leaves of Goldmine was related to the amino-acid content of comparable uninoculated leaves.     

Assessing resistance to Crinipellis perniciosa using cocoa callus

Callus cultures from cocoa clones reported to have different susceptibilities to Brazilian isolates of Crinipellis perniciosa , causal fungus of witches' broom disease, including Catongo (susceptible). Scavina-6, CAB 64 and CAB 67 (resistant) were inoculated with basidiospores of C. perniciosa and the subsequent development of mycelia was assessed. Generally, on Catongo callus, mycelium similar to that found in green brooms (parasitic type), developed abundantly but on callus from Scavina-6 and the two CAB clones, mycelial growth was relatively poor and tended to be similar to that in dry brooms and on agar media (saprotrophic type). There was often considerable variation in fungal development on individual callus cultures from the same clone, but there was an overall consistency between successive experiments in ranking the callus material in terms of fungal development. However, growth of isolates from Colombia and Trinidad was similar on callus from Scavina-6 which in the field is known to reac differentially to these two isolates. Experiments with isolates from Colombia indicated that inoculum from basidiocarps produced on brooms which were kept for long periods in cabinets to induce fruiting had a decreased ability to colonize callus.     

The status of the recently introduced fish Leucaspius delineatus (Cyprinidae) in Great Britain

Abstract The fish Leucaspius delineatus (Heckel) (Cyprinidae) has been introduced to southern England as a result of importation as an ornamental fish. It is now established at several waters (lakes, canals, and lowland rivers) in Hampshire and Somerset. It appears to be well adapted to spread beyond these centres as a result of its small size at sexual maturity and reproductive biology. A preliminary assessment of its diet and fecundity, and notes on its breeding habits are given.     

Methanotrophy-driven accumulation of organic carbon in four paddy soils of Bangladesh

Biological methane oxidation is a crucial process in the global carbon cycle that reduces methane emissions from paddy fields and natural wetlands into the atmosphere.However,soil organic carbon accumulation associated with microbial methane oxidation is poorly understood.Therefore,to investigate methane-derived carbon incorporation into soil organic matter,paddy soils originated from different parent materials(Inceptisol,Entisol,and Alfisol) were collected after rice harvesting from four major rice-producing regions in Bangladesh.Following microcosm incubation with 5%(volume/volume)¹³ CH₄,soil¹³ C-atom abundances significantly increased from background level of 1.08% to 1.88%–2.78%,leading to a net methane-derived accumulation of soil organic carbon ranging from 120 to 307 mg kg^-1.Approximately 23.6%–60.0% of the methane consumed was converted to soil organic carbon during microbial methane oxidation.The phylogeny of¹³ C-labeled pmoA(enconding the alpha subunit of the particulate methane monooxygenase) and 16 S rRNA genes further revealed that canonical α(type II) and γ(type I) Proteobacteria were active methane oxidizers.Members within the Methylobacter-and Methylosarcina-affiliated type Ia lineages dominated active methane-oxidizing communities that were responsible for the majority of methane-derived carbon accumulation in all three paddy soils,while Methylocystis-affiliated type IIa lineage was the key contributor in one paddy soil of Inceptisol origin.These results suggest that methanotroph-mediated synthesis of biomass plays an important role in soil organic matter accumulation.This study thus supports the concept that methanotrophs not only consume the greenhouse gas methane but also serve as a key biotic factor in maintaining soil fertility.