林分密度对新津文峰山马尾松人工林林下物种多样性和生物量的影响

以四川省新津文峰山马尾松(Pinus massoniana)人工林为研究对象,用典型抽样法探究5种林分密度(A:1000株/hm~2;B:1125株/hm~2;C:1250株/hm~2;D:1375株/hm~2;E:1500株/hm~2)对林下植被物种多样性和生物量的影响及林下植被物种多样性和生物量的相关性。结果显示:(1)共调查到植物124种,隶属于74科115属,灌木层物种少于草本层。(2)灌木或草本层在不同林分密度下的优势种都较一致。(3)灌木层物种丰富度指数D值、Shannon-Wiener多样性指数H值及草本层4个多样性指数均在密度B、E分别有最大和最小值;灌木层D值随密度增大而先增后减,其他3个指数变化规律不明显。灌、草层J_(sw)值较稳定。(4)灌木层生物量比草本层多。总体上灌、草层地上生物量大于地下生物量,都在密度B达最大;灌木地下生物量保持较稳定,而草本层变化幅度较大。(5)除灌木层J_(sw)值与该层各生物量呈负相关外,其余各指标均显示正相关。不同林分密度对马尾松林下植物多样性和生物量产生不同的影响,经综合研究分析认为,林分密度1125株/hm~2相对更利于该地马尾松人工林的可持续健康发展。     

林分密度对尾赤桉人工林群落结构与生态效应的影响研究

对永安市不同经营密度下尾赤桉(Eucalyptus urophylta×E. eamalducensis)人工林的林分结构、群落组成以及林下枯落物和土壤持水性能进行了分析,探讨造林密度对闽西北地区桉树人工林生态效应的影响。结果表明,密度对尾赤桉人工林林分径级结构有极显著影响,密度与平均胸径、树高间存在极显著的负相关,相关系数分别为-0.99和-0.93,对林分蓄积量也存在显著影响(r=0.84)。密度对林下灌草层物种多样性的影响呈现分异现象,与灌木层的相关性达到极显著水平(r=0.94),但与草本层的相关不显著(r=-0.52)。不同密度林分的林下植物种类有较大差异,但低密度林分的林下植被收获量最大。林分密度对枯落物持水率的影响较大(r=0.94)。     

外来树种日本落叶松和日本花柏对鄂西北森林群落的影响

【目的】研究大面积栽植外来树种日本落叶松和日本花柏对鄂西北森林群落物种多样性的影响,为评价外来树种的入侵风险提供依据。【方法】采用样地调查法对比研究外来树种日本落叶松和日本花柏人工林与当地森林群落特征差异。【结果】日本落叶松人工林样地林下植物种类丰富,样地平均物种数与当地天然林样地物种数相比无显著差异;林下灌木层和草本层多样性指数较高,草本层多样性指数与当地天然林相比无显著差异;林下未发现日本落叶松的更新苗。日本花柏人工林样地平均物种数显著少于当地其他人工林样地;乔木层、灌木层和草本层的4个多样性指数值均小于当地其他人工林样地;在3个样地中出现日本花柏更新苗,更新苗数量达479株·hm~(-2)。【结论】引种栽培日本落叶松不会导致当地森林群落的物种多样性降低,不会引起生物入侵风险;但引种栽培日本花柏会明显降低当地森林群落的物种多样性,对当地森林生态系统的稳定构成一定威胁。     

林分密度对云顶山柏木人工林林下物种多样性和土壤理化性质的影响

以成都云顶山柏木(Cupressus funebris)人工林为对象,采用典型样地法研究不同林分密度(1100、950、800、650、500株/hm~2)对林下物种多样性和土壤理化性质及林下物种多样性与土壤理化性质相关性的影响。结果表明:共发现维管植物168种,隶属75科140属。随林分密度的降低,灌木层多样性指数呈先增后减的单峰变化,在密度650株/hm~2出现峰值,草本层多样性指数呈先增后减再增再减的双峰变化,在密度950株/hm~2和650株/hm~2出现峰值。同时发现光照为影响林下植物多样性的重要因素。林分密度对土壤全氮、全钾、速效钾、有机质影响显著,有机质、全氮、全钾、速效钾随林分密度降低呈先增后减的变化趋势。钾、氮、有机质与林下植被物种多样性关系最密切。结论:林分密度650株/hm~2为云顶山柏木人工林最适密度,该密度能较好的提高林下物种多样性和土壤肥力。     

林分因子对成都绕城高速路域不同人工林群落物种多样性的影响

【目的】为探究林分因子对不同路域人工林群落物种多样性的影响,为成都路域人工林营造与管理提供参考。【方法】研究采用典型样地法对成都绕城高速路域现种植的5种不同人工林群落（Ⅰ,加杨纯林;Ⅱ,樟树、加杨混交林;Ⅲ,樟树纯林;Ⅳ,樟树、巨桉混交林;Ⅴ,巨桉纯林）进行全面踏查,调查林分因子及林下植被物种多样性。【结果】（1）研究区共记录植物184种,隶属于72科132属。5种不同人工林群落乔-灌-草三层的植物科属种数量均为草本层＞灌木层＞乔木层,其中樟树纯林记录到的林下物种数最多。（2）构树（Broussonetia papyrifera）和葎草（Humulus scandens）重要值占比大,分别占据不同人工林群落灌木层与草本层的优势地位。（3）在5种不同人工林群落中,樟树纯林的灌木物种丰富度指数D显著高于其他群落（P<0.05）;草本层的Shannon-Wiener指数H、Simpson指数H′和D大小变化趋势一致,表现为群落Ⅲ>Ⅳ>I>I>V,其中樟树纯林的H显著高于樟树、巨桉混交林外其他群落（P<0.05）。（4）冗余分析结果表明：乔木层平均冠幅与灌木层的D和H、草本层的H、H''、D、Jsw均呈显著正相关（P<0.01）,与灌木层的H''和Jsw均呈显著负相关（P<0.01）;乔木层平均枝下高与灌木层的H、H''、D、Jsw均呈显著正相关（P<0.01）。【结论】乔木层的树种组成、平均枝下高和平均冠幅显著影响路域人工林群落的物种多样性,选择合适树种并定期修枝管理,将有利于路域人工林良好乔灌草群落结构形成和林下植被物种多样性维持。 关键词 林分因子;路域人工林;林下植被;物种多样性     

马尾松人工林林分密度对林下植被及土壤性质的影响

采用样方调查及取样分析方法,研究广西大青山南亚热带不同密度马尾松人工林林下植被及土壤特征.结果表明:马尾松人工林自然发育14 a后,林分密度从1050 株·hm^-2增加到1800株·hm^-2,林下灌木层物种多样性指数增高.密度为1800 株·hm^-2时,多样性指数最高.当林分密度继续增大到2250 株·hm^-2,灌木层物种多样性指数却呈降低趋势.林下草本物种多样性指数对林分密度变化的响应不敏感;在林分密度影响下,林下灌木生物量与灌木层物种多样性指数变化规律一致.随着林分密度的增大,林下草本生物量呈降低趋势;不同密度马尾松人工林土壤理化特性差异显著(P<0.05).除全K、速效K和速效P外,土壤表层(0～20 cm)养分含量与林下灌木层物种多样性指数变化趋势一致.不同密度林地速效K和速效P含量变化波动较大.密度为2100 株·hm^-2的林分土壤 全P含量较高.中密度(1800 株·hm^-2)林地的土壤持水量和孔隙度均较高,土壤容重较低.     

中亚热带不同林龄杉木人工林径级结构与林下物种多样性分析

采用典型抽样法,以位于中亚热带的福建省将乐县的杉木〔Cunninghamia lanceolata ( Lamb.) Hook.〕人工林为研究对象,对10、15、20、25、30和40 a林分的径级结构、林下植被组成以及物种多样性变化进行调查和分析。结果表明：不同林龄杉木人工林的径级结构均呈正态分布,均在接近平均胸径的径级上植株数量最多;径级和密度间的关系可以用3参数的Gaussian函数表征;不同林龄间胸径差异显著。杉木人工林林下分布有45科80属97种植物,其中灌木层69种、草本层28种,物种丰富,但不同林龄的林分内各种类的重要值差异较大,且不同林龄的林分间优势种、共有种和独有种均明显不同。随林龄的增加,林下灌木层和草本层的物种组成、丰富度指数( R0)、Simpson多样性指数( D)和Shannon-Wiener多样性指数( H′)、Pielou均匀度指数( Jsw )和Alatalo均匀度指数( Ea )均有明显变化。10 a林分的林下物种数量最少(18种),而20 a林分的林下物种数量最多(40种)。林下灌木层的D和H′值分别为0.827~0.923和1.956~2.917,且随林龄的增加均呈“上升—下降—平稳”的变化趋势;灌木层的Jsw和Ea值分别为0.876~0.959和0.686~0.890,随林龄增加均呈“降低—升高—降低—升高”的变化趋势,且均在20 a林分中最小、在25 a林分中最大。林下草本层的D和H′值分别为0.639~0.898和1.274~2.435,并随林龄增加均呈波动的变化趋势;草本层的Jsw和Ea值分别为0.775~0.949和0.663~0.896,随林龄增加均呈“降低—升高—降低—升高—降低”的变化趋势,且均在15 a林分中最小、在10 a林分中最大。总体上看,林龄对杉木人工林林下灌木层和草本层的物种丰富度指数和多样性指数以及草本层的均匀度指数均有显著影响。根据研究结果,建议在杉木人工林的经营过程中对林下物种进行合理配置,并进行合理间伐,以促进林下植被的生长发育。     

晋西黄土区不同密度油松人工林林下植物多样性及水文效应

通过野外调查与室内实验相结合的方法,以晋西黄土区不同林分密度的油松人工林为对象,以林下植物多样性、枯落物蓄水、土壤物理性质和土壤蓄水能力为指标,分析了不同密度油松林对这些指标的影响,以期为油松林合理密度的确定提供科学依据。结果表明:油松林内灌木层物种丰富度指数、多样性指数随油松林密度的增大而减小,而均匀度指数无明显规律;草本层物种丰富度指数与灌木层变化规律一致,但多样性指数和均匀度指数均先增后减;油松林密度为1675株·hm-2时草本的多样性和均匀度为最大,整个群落的多样性指数和均匀度指数也最大;油松林灌木层的多样性指数及均匀度指数均大于草本层;不同密度油松林枯落物自然含水率无显著差异,而枯落物蓄积量、最大持水率以及持水量、有效拦蓄率和拦蓄量在一些林分密度间差异显著;密度为1300株·hm-2时,土壤容重最小,总孔隙度、毛管孔隙度及所对应的贮水量均最大;密度为1675株·hm-2时枯落物蓄积量、持水量最大,表层(0～20cm)土壤容重(1.07g·cm-3)相对较低,非毛管孔隙度(17.45%)及滞留贮水量(87.25mm)最大。综合来看,30年生左右的油松人工林,当密度约为1675株·hm-2时林下植物多样性及生态水文效应最好。     

草海国家级自然保护区华山松群落特征及物种多样性研究

为探讨喀斯特地区森林群落的演替动态和生物多样性维持机制,采用样地调查法对草海国家级自然保护区的华山松(Pinusarmandii)群落的物种组成、植物区系特征、种群结构和物种多样性等进行了分析。结果表明,样地内共有种子植物37科69属81种,其中乔木11种、灌木32种、草本38种;群落内植物的科、属区系成分类型多样,以温带成分为主;生活型谱主要以高位芽植物(46.91%)和地面芽植物(27.16%)为主;乔木层华山松的重要值达58%,为群落的单优势种;径级结构呈左偏正态型分布,树高分布集中在12～21 m,冠幅分布呈V型;乔木层与灌木层、草本层间的多样性差异显著(P0.05),物种丰富度指数S和D_M、多样性指数H和D_S均为草本层灌木层乔木层,物种均匀度指数J为灌木层草本层乔木层。因此,草海国家级自然保护区内的华山松群落特征和物种多样性具有明显的地域特点。     

林分密度对马尾松林下植物与土壤种子库多样性的影响

林分密度是影响林下植物多样性的重要因子。本研究以马尾松人工林为对象,设置低密度(1575株·hm^-2,D₁)、中密度(2474株·hm^-2,D₂)和高密度(3550株·hm^-2,D₃)3个林分密度,分析林下植物和土壤种子库多样性及二者的关系,为马尾松人工林实现多目标可持续发展提供科学依据。结果表明: 3种林分密度林下草本与灌木植物共有42科62属70种,D₁密度以喜光植物种类分布较多,而D₂、D₃密度以耐阴植物为主;3种林分密度间的草本、灌木的Margalef (M)、Shannon (H)、Simpson (D)、Pielou (J_sw)、Alatalo (Al)指数均随林分密度增加而呈下降趋势,且在草本与灌木层中对密度的响应不同。在草本层中,D₁与D₃的H、D、J_sw、Al指数均存在显著差异;在灌木层中,不同林分密度J_sw和Al指数存在显著差异,H和D指数差异不显著。土壤种子库H、D、J_sw和Al指数均随林分密度增加呈先下降后升高趋势,D₁密度的物种丰富度及多样性最高;不同林分密度下土壤种子库Jaccard与Sorensen相似性系数均较低。草本层M与J_sw指数呈显著正相关;灌木层林分密度与H、D、J_sw、Al指数的相关性大于草本层,而草本、灌木层的林分密度与J_sw指数均呈显著负相关。林分密度1575株·hm^-2是马尾松林下植被生长发育较为合适的密度,能够维持林下植物多样性,有利于马尾松人工林的可持续经营。     

Systematic significance of mature embryo of bamboos

The mature embryo of seven species belonging to five genera of Indian bamboos is described. In all these the basic pattern of embryo organisation is same: the scutellar and coleoptilar bundles are not separated by an internode, the epiblast is absent, the lower portion of the scutellum and the coleorhiza are separated by a cleft and the margins of embryonic leaves overlap. The features unique to fleshy fruited bamboos are: presence of a massive scutellum, the juxtaposition of plumule and radicle and the occurrence of a bud in the axil of the coleoptile. The fleshy fruit bearing bamboos should be classified into one group, the tribeMelocanneae. Evidence is provided to recognise additional groups in the subfamilyBambusoideae.     

Taxonomic status of the species of the green algal genusNeochloris

Komárek has recently reviewed the various species assigned to the green algal genusNeochloris Starr (Chlorococcales, Chlorococcaceae) and removed those with uninucleate vegetative cells to a new genus,Ettlia. Watanabe & Floyd, unaware ofKomárek's work, also reviewed the species ofNeochloris and distributed them among three genera—Neochloris, Chlorococcopsis gen. nov., andParietochloris gen. nov.—on the basis of details of the covering of the zoospore and the arrangement of the basal bodies of the flagellar apparatus. This paper reconciles these two treatments and makes additional recommendations at the ranks of genus, family, order, and class.     

Phylogeny of cardinalfishes (Teleostei: Gobiiformes: Apogonidae) and the evolution of visceral bioluminescence

The cardinalfishes (Apogonidae) are a diverse clade of small, mostly reef-dwelling fishes, for which a variety of morphological data have not yielded a consistent phylogeny. We use DNA sequence to hypothesize phylogenetic relationships within Apogonidae and among apogonids and other acanthomorph families, to examine patterns of evolution including the distribution of a visceral bioluminescence system. In conformance with previous studies, Apogonidae is placed in a clade with Pempheridae, Kurtidae, Leiognathidae, and Gobioidei. The apogonid genus Pseudamia is recovered outside the remainder of the family, not as sister to the superficially similar genus Gymnapogon. Species sampled from the Caribbean and Western Atlantic (Phaeoptyx, Astrapogon, and some Apogon species) form a clade, as do the larger-bodied Glossamia and Cheilodipterus. Incidence of visceral bioluminescence is found scattered throughout the phylogeny, independently for each group in which it is present. Examination of the fine structure of the visceral bioluminescence system through histology shows that light organs exhibit a range of morphologies, with some composed of complex masses of tubules (Siphamia, Pempheris, Parapriacanthus) and others lacking tubules but containing chambers formed by folds of the visceral epithelium (Acropoma, Archamia, Jaydia, and Rhabdamia). Light organs in Siphamia, Acropoma, Pempheris and Parapriacanthus are distinct from but connected to the gut; those in Archamia, Jaydia, and Rhabdamia are simply portions of the intestinal tract, and are little differentiated from the surrounding tissues. The presence or absence of symbiotic luminescent bacteria does not correlate with light organ structure; the tubular light organs of Siphamia and chambered tubes of Acropoma house bacteria, those in Pempheridae and the other Apogonidae do not.     

Analysis of twin of eyeless regulation during early embryogenesis in Drosophila melanogaster

The Drosophila Pax6 homolog twin of eyeless (toy) is so far the first zygotically expressed gene involved in eye morphogenesis in Drosophila. The study of its expression during embryogenesis is therefore informative of the initial events of eye development in Drosophila. We have analyzed how the initial expression domain of toy at cellular blastoderm is regulated. We show that the three maternal patterning systems active in the cephalic region (the anterior, terminal and dorsal-ventral systems) cooperate with zygotically activated gap genes to shape the initial expression domain of toy. Whereas Bicoid, Dorsal and Torso signaling synergistically act as activators, Hunchback, Knirps and Decapentaplegic act as repressors.     

Host plants of someRhinanthoideae (Scrophulariaceae) of eastern North America

Twenty three species in 11 genera were examined in the field to determine hosts. OnlyStriga asiatica andSeymeria cassioides have a narrow host range being restricted to grasses and pines, respectively. These are the only species which cause pronounced and sometimes serious host damage. The other species attach to a great diversity of hosts.     

Apoptotic Regulation of Caspase Activity

Intracellular cysteine aspartate-specific proteases (caspases) play both signaling and effector roles in realizing the program of cell death. Caspases function as proteolytic cascades unique for each cell type and signal triggering apoptosis. All parts of the proteolytic cascades are duplicated and controlled by feedback signals. Amplification cycles between pairs of caspases (the third and the sixth, the ninth and the third, the twelfth and the sixth, and others) help multiply the initial apoptotic signal. The presence of physiological inhibitors of apoptosis that directly interact with caspases creates a multilevel regulatory network of apoptosis in cell. The caspase proteolytic cascades are also regulated by sphingolipid secondary messengers, among them ceramide, sphingosine, and their phosphates. Moreover, an association of the caspase signaling with ubiquitin-dependent proteolysis is shown in cells. In particular, the use of extracellular activators and inhibitors of caspases allows irreversible activation of apoptosis in tumor cells or the prevention of apoptosis in cortical neurons under neurodegenerative diseases.     

广西青藓科分类学修订

通过对采自广西24个县(市)的1 147份青藓科植物标本的逐一鉴定及相关文献的查阅,确认有广西青藓科植物11属、44种,其中包括广西青藓科植物新记录属1属,即拟异叶藓属(Pseudokindbergia),新记录种7种,分别为匐枝青藓(Brachythecium procumbens)、阔叶尖喙藓(Oxyrrhynchium latifolium)、泛生尖喙藓(O. vagans)、拟异叶藓(Pseudokindbergia dumosa)、华东细喙藓(Rhynchostegiella sinensis)、长肋拟青藓(Sciurohypnum populeum)和弯叶拟青藓(S. reflexum)。该文提供了修订后的广西青藓科植物名录,并对其中的新记录属、种的主要形态学识别特征、生境和地理分布等进行了详细描述。     

In vitro appraisal of the probiotic value of intestinal lactobacilli

Lactobacilli play a distinctive role in the microbial balance of the chicken gut. In experiments simulating the chicken crop, the antagonism of lactobacilli against Enterobacteriaceae and Salmonella typhimurium was demonstrated and was attributed to lactic acid production. Moreover, adhesion to the crop epithelium was a common characteristic of intestinal lactobacilli. As opposed to salmonellas, lactobacilli were sensitive to deconjugated bile salts at 2.5mm. This sensitivity could lower their chance of proliferation in the small bowel of the chicken tract.The authors are at the Laboratory of Microbial Ecology, Faculty of Agricultural Sciences, State University of Gent, Coupure L., 653, B-9000 Gent, Belgium.     

Evaluation of antiprotozoal and antimycobacterial activities of the resin glycosides and the other metabolites of Scrophularia cryptophila

Resin glycosides are secondary metabolites exclusive to the convolvulaceous plants. In this study, crypthophilic acids A–C (1–3), the first resin glycosides occurring in another family (Scrophulariaceae), and the other constituents of Scrophularia cryptophila were examined for in vitro antiprotozoal and antimycobacterial potentials. Except for crypthophilic acid B (2), all tested compounds exhibited growth-inhibitory effect against Trypanosoma brucei rhodesiense, with l-tryptophan (6) and buddlejasaponin III (7) being the most potent ones (IC₅₀'s 4.1 and 9.7 μg/ml). In contrast, the activity towards Trypanosoma cruzi was poor, and only crypthophilic acid C (3), 6 and 7 were trypanocidal at concentrations above 40 μg/ml. With the exception of 2 and 6, all compounds were active against Leishmania donovani. Harpagide (4) and 3 emerged as the best leishmanicidal agents (IC₅₀'s 2.0 and 5.8 μg/ml). Only compounds 3, 6 and 7 showed antimalarial activity against Plasmodium falciparum with IC₅₀ values of 4.2, 16.6 and 22.4 μg/ml. Overall the best and broadest spectrum activity was presented by compounds 3 and 7, as they inhibited all four parasitic protozoa. None of the isolates had significant activity against Mycobacterium tuberculosis (MICs >100 μg/ml) or were toxic towards mammalian (L6) cells. This is the first report of antiprotozoal activity for natural resin glycosides, as well as for harpagide (4), acetylharpagide (5), tryptophan (6) and buddlejasaponin III (7).