广西南丹县江南油杉天然林群落结构特征

在广西南丹县江南油杉(Keteleeria fortunei var. cyclolepis)天然林设置20 m×20 m的标准样地5个,10 m×10 m的单位样方20个,调查样地中群落物种种类组成、层次结构、物种多样性及群落径级和高度级结构。结果表明:江南油杉天然林群落植物种类丰富,2 000 m~2的样地中共有维管束植物41科69属74种。群落以高位芽植物占优势地位,占总数的74.24%。群落层次结构可分为乔木层、灌木层和草本层及层间植物,灌木层的物种种类最丰富,个体数量分布也最均匀,该层的物种丰富度(S)、Shannon-Wiener指数(H')、Simpson指数(D)、群落均匀度(J)均大于草本层和乔木层。乔木上层的主要树种有江南油杉、杉木(Cunninghamia lanceolata)、枫香(Liquidambar formosana)、冬青(Ilex chinensis),江南油杉的重要值、相对频度、相对多度、相对显著度均居乔木层的首位,说明江南油杉是群落中绝对的优势种,决定群落的性质。     

福建光泽江南油杉群落结构与植物多样性

通过对福建光泽江南油杉群落结构与植物多样性进行调查与分析,结果表明:江南油杉群落(2 000m2)有维管束植物48科72属92种;江南油杉群落以高位芽植物占据优势(80.44%),生活型谱具有典型的中亚热带气候特点;群落径阶和树高结构复杂,物种多样性丰富,不同层次物种多样性指数和均匀度指数均为灌木层乔木层藤本层草本层,体现了的亚热带常绿阔叶林的典型特征;群落中江南油杉在乔木层占绝对优势,但幼苗幼树数量较少,在灌木层受到其他植物(主要是木本植物)的强烈竞争,种群有衰退的趋势。     

滇中地区麻栎天然次生林的林分特征研究

2007年3月对滇中禄丰村林场具有代表性的3 hm2麻栎次生林的组成及生长状况进行了调查,分析其林分类型,主要乔木树种的径阶分布及其在群落中的重要值,进而对林分的生态效能进行评价.研究结果表明,该麻栎次生林划分为麻栎—云南松和麻栎—云南松—滇油杉2种林分类型,林木株数分布分别集中于径阶8 cm和6 cm处,以麻栎为优势树种,云南松为伴生树种.麻栎林木的优势度达50.77,重要值为71.71.林分主要乔木树种麻栎、云南松及滇油杉的林木密度分别为1 825株/hm2、650株/hm2和325株/hm2,其中伴生树种云南松和滇油杉优势较为明显.林分中乔木层最大树高20.1 m,最大胸径40 cm,均为云南松植株.其群落结构简单,物种较少,生态功能差,为低质低效林分,急需改造.     

浙江高姥山金缕梅群落特征及种群结构的研究

在全面踏查的基础上,于2016年7月对浙江高姥山金缕梅Hamamelis mollis群落结构特征以及金缕梅种群结构进行调查研究。研究表明,群落中以金缕梅和四照花Dendrobenthamia japonica var. chinensis为主要优势种,其重要值分别为20.126%和17.737%,两者的重要值比例为37.863%;乔木层的物种丰富度指数最高,灌木层的物种均匀度指数最高,而乔木层、灌木层和草本层的优势度指数均较高且极为接近,说明该群落为相对不成熟群落;群落的乔木层高度主要集中在5～6 m。群落中金缕梅的高度虽然并不占优势,但通过根出条萌枝扩大冠幅,从而争夺群落资源;由于萌枝作为其主要更新方式,金缕梅种群整体呈聚集分布。金缕梅种群的大小结构以III级小树和IV级中树为主,由此认为该种群目前尚处于稳定阶段。     

陕西米仓山自然保护区铁杉天然林群落结构及植物组成

通过样地调查法研究了陕西米仓山自然保护区铁杉天然林植物组成和群落结构特征,结果显示,铁杉天然林树龄40~200a,其中60~90a林木居多,林木平均高度19.6m、胸径29.9cm,为纯林。乔、灌、草三层结构,乔木层郁闭度0.8,灌木层平均高度为1.2m、盖度90%,草本层盖度8%;林分密度为390株·hm-2,以22~26、26~30cm径级和24~26、26~28m高度级所占比例较大;乔木层8个树种的重要值为0.02%~97.91%,其中铁杉最高,为建群种,其它树种很低,基本以单株形态存在;灌木层15种植物重要值为0.81%~48.38%,秦岭箭竹最高,为优势种;草本层11种植物都有一定的荫生性特征,重要值为1.69%~35.59%,犁头草最高,为优势种。     

濒危植物广西火桐群落特征研究

采用样地调查法,对广西特有的珍稀濒危植物广西火桐(Erythropsis kwangsiensis)群落特征进行分析,结果表明:在3个样点共1 200 m2的样方中,含维管束植物68科122属152种,这些属可划分为11个分布区类型,其中热带分布的属优势明显,占81.1%;群落生活型以高位芽植物为主,地上芽植物次之;叶的性质以中型叶、单叶、纸质、全缘为主;广西火桐群落结构复杂,可分为乔木层、灌木层和草本层,层间植物丰富,广西火桐在乔木层中处于单优势种地位;由于人类活动的干扰,群落表现出明显的次生性质。     

云南九龙山自然保护区水青冈群落物种多样性及群落特征

采用典型样方调查法,对云南九龙山自然保护区内的水青冈群落生物多样性及群落特征进行研究,共设置7个30 m×30 m的样方,从群落的物种组成、重要值、物种多样性、种群年龄结构等方面进行分析。结果表明:云南九龙山水青冈群落中共有维管束植物81种,隶属48科71属,其中蔷薇科为优势科;物种丰富度、多样性、均匀度和优势度在所有群落中均表现为草本层>灌木层>乔木层;在水青冈种群年龄结构中,Ⅳ级和V级所占比例为21.4%、78.6%,未发现幼苗、幼树分布,表明种群自然更新不良,表现为衰退型。提出减少人为干扰因素,促进群落自然更新,建立种群动态数据库,在保持群落物种多样性的同时注重维持群落稳定性等保护建议。     

广东银瓶山森林公园浙江润楠群落结构与物种多样性研究

通过样方调查,对广东银瓶山森林公园的浙江润楠(Machilus chekiangensis)群落的群落特征和物种多样性进行分析。结果表明:(1)在1600m2的样地内共有维管束植物58科85属107种;(2)群落以浙江润楠为建群种,优势地位明显;年龄结构显示其种群可能处于受干扰后的恢复阶段;(3)群落植物以小高位芽植物为主,叶以单叶、纸质、全缘叶、中小型叶为主;按Raunkiaer标准,群落内的种群频度为1%～20%的种类占优势;(4)群落成层现象明显,可分为乔木层、灌木层、草本层及藤本层,对群落物种多样性分析发现,Margalef指数的大小顺序为:灌木层>乔木层>草本层>藤本层,Simpson指数和Shannon-Wiener指数的的大小顺序均为:灌木层>乔木层>藤本层>草本层,Pielou指数的大小顺序为:藤本层>灌木层>草本层>乔木层。     

人为干扰对闽楠群落结构及物种多样性的影响

闽楠是国家Ⅱ级重点保护植物,是我国特有树种。为揭示人为干扰对闽楠群落的影响,选择广西富川县蚌贝村2个闽楠群落,研究了在不同干扰强度下其植物种类组成和物种多样性。结果表明:(1)从群落结构上看,随着干扰强度变大,中小径级(DBH40cm)个体密度变大,而大径级(DBH≥40cm)个体密度变小,但人为干扰对群落径级分布的总趋势影响不显著(P=0.1030.05)。重度干扰群落个体多分布在中高度级(15m≤H30m),轻度干扰群落则多分布在低高度级(H15m)和高高度级(H≥30m)。(2)物种相似性分析表明,人为干扰对灌木层物种组成的影响最大。随着干扰强度增大,灌木层个体密度和物种数分别表现出减小和增大的不同趋势。重度干扰明显改变了乔木层和灌木层优势种的物种组成。(3)随着干扰强度增加,灌木层各物种多样性指数均出现显著提高,但乔木层和草本层的变化不显著(P0.05)。     

澳门松山阴香群落特征及物种多样性研究

采用样方调查法,对澳门松山阴香(Cinnamomum burmannii)群落的种类组成、区系、外貌、群落结构特征、物种多样性和群落优势种的物候进行调查分析。结果表明,澳门松山阴香群落为南亚热带次生性常绿阔叶林,1200 m2样方中有维管植物87种,隶属于46科78属,其中占绝对优势是热带成分。阴香为群落优势种,重要值77.45。群落可分为乔木层、灌木层和草本层,3个层次多样性格局基本表现为灌木层>乔木层>草本层,终年常绿,成层现象明显,且层间植物丰富。对优势种群的年龄结构进行分析表明,该群落处于增长状态。群落频度分布规律为A级>B级>C级>D(E)级,与Raunkiaer的L形频度定律曲线相一致。澳门松山阴香群落是澳门较少有的天然近顶级群落,建议对松山的植被进行适当的保护。     

Improving the evaluation of multiple-dowel-type connection strength

Our study focuses on predicting the ultimate short-term load carrying capacity of timber-to-timber connections with dowel-type fasteners. The wide range of possible configurations in practice makes the resolution of these values by tests unrealistic. Moreover, different current regulations do not consider some specific failure mechanisms. In many countries, the reduction of resistance involved by this phenomenon is taken into account by considering an effective number of dowels (n_ef) smaller than the actual number of dowels (n) in the connection. However, these different regulations disagree on the values of n_ef and on other points (spacing, partial coefficient of security, formulas). These discrepancies in design rules invite the fundamental research on this topic and, therefore, new methods are sought in order to estimate the load carrying capacities of the connections. In the light of these, our approach consists of predicting the load carrying capacity with the neural network numerical tool. The results obtained by this analysis tool are satisfactory, although the model remains complex. Subsequently, we focus on the simplification of this numerical model with classical regression techniques in order to implement it in a design code.     

<Emphasis Type="Italic">Ophiostoma</Emphasis> species associated with bark beetles infesting three <Emphasis Type="Italic">Abies</Emphasis> species in Nikko,Japan

Ophiostoma species were isolated from bark beetles and Abies mariesii, A. veitchii and A. homolepis attacked by the beetles in Nikko, Tochigi, central Honshu, Japan. One to two Ophiostoma species were frequently isolated from each species of bark beetle. Ophiostoma subalpinum was the most common associate of Cryphalus montanus. Ophiostoma sp. B as well as O. subalpinum was a common fungus associated with Polygraphus proximus. Ophiostoma europhioides was isolated from Dryocoetes hectographus and D. autographus as one of the common associates. Ophiostoma sp. J and Ophiostoma sp. S were frequently isolated from D. autographus and D. striatus, respectively. These fungi seem to have specific relationships with particular bark beetles. Ophiostoma sp. B, Ophiostoma sp. J and Ophiostoma sp. S have unique morphological characteristics and appear to be new species. Five trees of A. veitchii, approximately 43 years old, were inoculated with five Ophiostoma species to assess the relative virulence of the fungi. Ophiostoma subalpinum, Ophiostoma sp. B, and O. europhioides had relatively higher virulence than the other species studied.     

Parasitic Ichneumonoidea on the horse chestnut leaf miner, Cameraria ohridella (Lepidoptera: Gracillariidae) in Slovakia

Parasitic Hymenoptera from the suprafamily Ichneumonoidea attacking the horse chestnut leafminer Cameraria ohridella Deschka & Dimic (Lepidoptera: Gracillariidae) were studied in southwest Slovakia during 2000 and 2001. The search for such species resulted in the determination of eight ichneumonid species, Gelis agilis (Fabricius), Itoplectis alternans (Gravenhorst), I. clavicornis (Thompson), I. maculator (Fabricius), Scambus annulatus (Kiss), S. brevicornis (Gravenhorst), Zatypota percontatoria (Müller), Adelognathus sp. and a braconid Colastes braconius Haliday. The most abundant species was S. annulatus. All these species recorded are polyphagous and often facultative hyperparasitoids, except C. braconius, which departs from this norm in not being hyperparasitic. The presence of more diversified native parasitoids and hyperparasitoids from the Ichneumonoidea predicate a slow successive adaptation of the parasitoid fauna to the invasive host, Cameraria ohridella.     

Decomposition and nutrient loss from prunings of different contour hedgerow species in tea plantations in the sloping highlands of Sri Lanka

Contour hedgerows of multipurpose tree species in the sloping tea lands of Sri Lanka are expected to reduce soil erosion and also add significant amounts of plant nutrients to the soil via periodic prunings. The objective of this experiment was to characterize the biomass decomposition pattern and quantify the amount of nutrients added through prunings of six tree species (Calliandra calothyrsus, Senna spectabilis, Euphatorium innulifolium, Flemingia congesta, Gliricidia sepium and Tithonia diversifolia) currently being used in hedgerows associated with tea. Withered leaf and stem prunings (50 g) were enclosed in 2-mm litter bags, placed at 5-cm depth and retrieved after one, three, six, nine and 12 weeks. Loss of initial dry weight, N, P and K was measured. Single exponential decay function adequately described both dry weight and nutrient loss. Tree species differed significantly in their rate of breakdown with decomposition constants (k) varying from 0.0299 to 0.2006 week⁻¹ for leaves and from 0.0225 to 0.0633 week⁻¹ for stems. Gliricidia showed the highest k for leaves with the rest in the following descending order: Senna > Tithonia ≥ Euphatorium > Calliandra > Flemingia. A similar pattern was observed for loss of all nutrients with Calliandra and Flemingia always having lower k values than the rest. Although N immobilization was not observed, immobilization of P and K was observed during the first week of incubation in some species, particularly in stem prunings. Annual biomass of prunings differed significantly between tree species in the following descending order: Calliandra > Senna > Flemingia > Tithonia > Gliricidia > Euphatorium. Calliandra added the greatest amount of nutrients annually to the soil with Euphatorium adding the least. Calliandra prunings provided the annual total K requirement and 49% of the N requirement of mature tea. However, none of the species provided more than 5% of the P requirement. It is concluded that among the tree species tested, Calliandra and Flemingia are the most suitable for contour hedgerows in tea plantations of this agroclimatic region because of their higher soil nutrient enrichment capacity and slower decomposition rates which would minimize leaching losses. This revised version was published online in June 2006 with corrections to the Cover Date.     

Potential to harness superior nutritional qualities of exotic baobabs if local adaptation can be conferred through grafting

Baobab leaves form an important part of the local diet in Sahel countries and elsewhere in Africa. Existing leaf nutritional data and agroforestry performance information are based solely on Adansonia digitata L., the baobab of continental Africa. The introduction potential of Adansonia species from the center of diversity in Madagascar and from Australia remains untapped. To assess this potential, the mineral contents and B₁ and B₂ vitamin levels of dried baobab leaves were determined for five-year old trees of A. digitata, A. gibbosa (A. Cunn.) Guymer ex D. Baum, A. rubrostipa Jum. & H. Perrier (syn. A. fony Baill.), A. perrieri Capuron and A. za Baill. grown in an introduction trial in Mali. Nutritional data were evaluated against survival and vigor to identify promising germplasm. Leaf vitamin and crude protein contents were highest in the Madagascar species, especially A. rubrostipa (B₁ 88 mg 100 g⁻¹, B₂ 187 mg 100 g⁻¹, protein 20.7% dry weight). However, the local species far outperformed the introductions in survival, tree height, basal diameter and resistance to termites. We suggest grafting as a way of harnessing the vigor of well-adapted local baobab varieties to the superior nutritional profiles of A. rubrostipa and others. Cross-species grafting tests in Adansonia were successful, thus creating new agroforestry possibilities with different scion/rootstock combinations.     

Rehabilitation of diseased cacao fields in Peru through shade regulation and timing of biocontrol measures

The objective of this case study was to test the effectiveness of biocontrol for the rehabilitation of abandoned, diseased (moniliasis, witches' broom and black pod) cocoa and to develop testable hypotheses regarding the effect of shade and biocontrol timing. Three trial fields differed in their shade regimes. Biocontrol was administered starting either at flowering or pod filling. Disease incidence and yield were compared with cultural control alone. Biocontrol reduced moniliasis from 49% to 25%, independent of the shading regime and application time. Witches' broom was most severe without shade and unaffected by biocontrol. No significant effects on black pod were observed. Although biocontrol increased percentage healthy fruit independent of shading and timing, only the shaded plot with biocontrol from flowering onwards responded with increased yield. Our hypothesis is: 'In the rehabilitation of abandoned cacao, only fields under sustainable shade management and early onset of biocontrol can realise their production potential.' This revised version was published online in June 2006 with corrections to the Cover Date.     

Populations of adult fungus gnats and shore flies in British Columbia container nurseries as related to nursery environment,and incidence of fungi on the insects

Adult fungus gnat and shore fly populations were monitored in four container nurseries near Victoria, British Columbia. In general, populations of both insects were larger in summer than in winter. Also, both insects were more abundant in the nursery with a plastic-covered, soil floor, which favored moisture accumulation and build up of algae, liverworts and mosses, than in nurseries with other types of floors such as cement. Results of fungus isolations revealed that gnats and flies both harbor the seedling pathogens Botrytis cinerea and species of Fusarium and Phoma, plus several non-pathogenic fungi. The results are discussed in relation to nursery sanitation practices, their effects on gnat and fly populations, and some possible roles of these insects in seedling disease epidemiology.     

Insecticidal activity of certain medicinal plants

The methanol extracts of eight species of medicinal plants were tested for insecticidal activity in third instar larvae of Egyptian cottonworm (Spodoptera littoralis). All extracts showed a certain degree of larval toxicity. The extracts of Ocimum basilicum, Origanum majorana and Salvia officinalis appeared to be highly toxic. The extracts significantly affected the growth indexes [relative growth rate (RGR), efficiency of conversion of ingested food (ECI), efficiency of conversion of digested food (ECD)].     

A new norlignan from Taxodium ascendens

A new norlignan, (2R,3R,4S,5S)-2,4-bis(4-hydroxyphenyl)-3,5-dihydroxy-tetrahydropyran (1), together with 9 known compounds were isolated from the branches and leaves of Taxodium ascendens. Their structures were mainly determined on the basis of MS, IR, 1D and 2D NMR spectral evidences. Methanol extract showed inhibitory activity on carbonic anhydrase II with an IC₅₀ value of 4.27 µg/ml, acetone extract and methanol extract inhibited activity of cathepsin B with IC₅₀ values of 2.12 and 3.71 µg/ml, respectively.     

Pinus contorta growth in northern Sweden as affected by soil scarification

The aim of this study was to quantify the effects of different soil scarification methods on tree growth. Soil scarification influenced stem volume and stem biomass yield of lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) in a 17-year-old field trial in boreal Sweden. Soil scarification (disc trenching, mounding and ploughing) resulted in an average stem volume yield of 3.1 and 34.2 m³ ha^–1 on the poor and intermediate sites, respectively, while corresponding values for no soil scarification were 0.9 and 16.7 m³ ha^–1. In comparison to no scarification, ploughing increased volume yields by 500% on the poor site and by 200% on the intermediate sites. The ranking according to stem volume yield was ploughing > disc trenching = mounding no soil scarification. Averaged over the two sites, the mean annual increment of stem biomass was 219% and 145% higher (in d.w., 0.26 kg and 0.34 kg per sample tree) after ploughing compared with no soil scarification, for the average and dominant sample trees, respectively. Although not significant, the increased growth rate after soil scarification decreased the average stem basic wood density of the sample trees with 1.6% and 5.3%, at the poor and intermediate sites, respectively. In conclusion, soil scarification significantly increased the 17-year stem volume yield compared with no scarification. The results also indicate that the difference in stem biomass yield between ploughing and the other methods, especially no soil scarification, will increase even more in the near future.