翅荚木人工林不同径阶间细根主要功能性状与根际土壤养分的关系

细根能敏感地感知土壤环境变化,对植物生长发育具有重要影响.以6年生翅荚木人工林为对象,对其不同径阶的细根主要功能性状与根际土壤养分特征及两者间关系进行分析.结果表明:细根生物量、根长密度与根体积密度均随径阶增加而增加,比根长与比根面积则随径阶增加呈先升高再下降后升高的趋势,根组织密度则与径阶大小不相关.不同径阶翅荚木根际土壤的pH值及含水率、全碳、全磷、铵态氮、硝态氮和总有效氮含量均存在显著差异,大径阶林木的根际土壤全碳、全氮、硝态氮、总有效氮含量相对较高,小径阶林木的根际土壤含水率、土壤全磷、铵态氮含量相对较高.土壤全氮、全碳、硝态氮和总有效氮含量与林木细根的生物量、根长密度、根体积密度呈显著正相关;土壤全磷与林木细根的根组织密度呈显著正相关,与比根长、比根面积呈显著负相关;土壤含水率与林木细根的生物量和根体积密度均呈显著正相关;根际土壤pH和林木细根的比根长、比根面积呈显著正相关,与根组织密度则呈显著负相关.研究结果可为翅荚木优良种质资源选育提供科学依据.     

不同林龄红锥人工林细根垂直分布和衰老生理特征

以广西桂东和桂南地区3种林龄(7、14和25 a)红锥人工林细根为对象,在红锥生长旺季,采用根钻法,分表层(0～20 cm)和亚表层土壤(20～40 cm)获取细根,研究不同林龄红锥人工林细根在不同土层的形态、生物量以及衰老生理生化指标变化特征,以期深入认识红锥生长发育机制及林分生产力,为红锥人工林可持续经营提供依据。结果表明:在相同土层中,随林龄增加,红锥细根根长密度、根表面积密度、生物量、比表面积、细根活力、可溶性糖和可溶性蛋白含量均显著增加,而比根长、游离脯氨酸和丙二醛(MDA)含量显著减少;在相同林龄下,随土壤深度增加,红椎细根比根长、比表面积、细根活力、各渗透调节物质含量均显著增加,而根长密度、表面积密度、生物量、MDA含量显著减少;林龄和土层的交互作用对细根生物量、可溶性糖、可溶性蛋白和MDA含量有显著影响。细根根长密度、根表面积密度和生物量与各土壤因子间呈显著正相关;细根游离脯氨酸含量与各土壤因子间呈显著负相关;细根活力、可溶性糖和可溶性蛋白仅与土壤含水率、速效氮呈显著正相关。因此,7 a红锥细根易衰老,更新快,14 a林次之,25 a林细根更新慢;表层土(0～20cm)的红锥细根代谢旺盛,周转速率快,寿命较短。     

山西太岳山不同林龄华北落叶松林土壤微生物特性!

本文以山西太岳山3个林龄(18、35和51年生)华北落叶松林为对象,研究其土壤微生物生物量、土壤真菌群落结构多样性特征,并利用通径分析,探讨土壤和凋落物养分含量对土壤微生物的影响。结果表明:随着华北落叶松林年龄的增加,土壤微生物生物量碳逐渐增加,微生物生物量碳占其与可溶性有机碳之和的比例也逐渐增加;土壤微生物生物量碳/氮比在51年生华北落叶松林中最大(13),约为其他两个林龄华北落叶松林的1.6倍;土壤微生物碳熵在35年生华北落叶松林中最低(1.5%),在18年生华北落叶松林中最高(2.8%)。土壤微生物生物量氮、真菌Shannon指数、土壤和凋落物碳/氮比在不同林龄华北落叶松林中的变化趋势均为35年生18年生51年生。通径分析结果表明,真菌群落结构多样性对土壤微生物生物量碳有较大的直接作用,凋落物自身化学组成对土壤微生物生物量氮有显著影响,土壤碳/氮比和微生物生物量碳/氮比是调控真菌群落结构多样性的直接因素。总的来说,35年生华北落叶松林的土壤有机碳活性最小,土壤碳库稳定性较好,养分状况优于另外两个林龄华北落叶松林。     

山西太岳山好地方典型植被类型土壤理化特征

以山西太岳山好地方林场4种植被类型(草甸、灌丛、华北落叶松人工林、华北落叶松-白桦混交林)0~60 cm土层土壤为研究对象,采取野外定点取样和实验室分析的方法,研究不同植被类型土壤理化性质特征。结果表明:土壤容重和p H值随土层深度的增加而增加;土壤含水量随土层深度增加而减小;不同植被类型间,土壤含水量大小排序为华北落叶松-白桦混交林草甸华北落叶松人工林灌丛;容重为灌丛华北落叶松-白桦混交林华北落叶松人工林草甸;p H值变化规律为华北落叶松-白桦混交林华北落叶松人工林灌丛草甸;土壤有机质、全氮含量随土层深度增加而减小,各土层之间差异显著;全磷和全钾含量各土层间差异不显著;不同植被类型间,草甸土壤有机质、全氮、全磷含量都高于其他3种植被类型,灌丛土壤全钾含量高于其他3种植被类型;土壤有机质与全氮呈极显著正相关;容重与含水量、有机质、全氮呈极显著负相关;p H值与有机质、全氮、全磷呈极显著负相关。     

樟子松林根际与非根际土壤碳氮磷化学计量特征

为揭示呼伦贝尔沙地樟子松根际与非根际土壤碳氮磷化学计量特征,以不同林龄(28、37、46年生)樟子松人工林为研究对象,以樟子松天然林为对照,研究根际与非根际土壤有机碳、全氮和全磷含量及其化学计量比,分析土壤性质与土壤化学计量特征间的相关性。结果表明：在樟子松人工林中,根际效应显著影响土壤N∶P,林龄显著影响土壤有机碳含量;各林龄人工林的土壤有机碳含量均显著低于天然林。人工林的根际与非根际土壤有机碳、全氮含量均随林龄增加先降低再升高;全磷含量在根际土壤中先升高再降低,在非根际土壤中先降低再升高。C∶N与C∶P在根际土壤中呈显著正相关,但在非根际土壤中不存在显著相关关系,说明根际土壤氮磷限制具有更高的协同性。根际与非根际土壤N∶P均值分别为4.98与8.40,表明樟子松人工林的生长受土壤N限制,且根际土壤受N限制程度更高。根际与非根际土壤碳氮磷化学计量特征受土壤性质的显著影响,其中,速效磷是最主要的驱动因子。呼伦贝尔沙地樟子松生长受N限制,其植物根系对土壤养分的富集与维持有明显作用,建议在樟子松生长阶段适当补充土壤氮素,并根据根际土壤氮磷限制的协同性适当补充磷素。     

不同林龄落叶松人工林土壤微生物生物量碳氮的季节变化

为从土壤微生物生物量角度分析不同林龄落叶松人工林的土壤肥力状况,对辽宁东部山区两种林龄(9年生,幼龄林;43年生,成熟林)落叶松人工林不同土层(腐殖质层和矿化层)微生物生物量碳、氮季节变化进行了监测,并分析了微生物生物量碳氮的季节变化与土壤养分及水分的关系.结果表明:两种林龄落叶松腐殖质层微生物生物量碳、氮含量均高于矿化层;在腐殖质层,幼龄林微生物生物量碳、氮含量高于成熟林.方差分析表明,在春、秋季节,同一土层两林龄土壤微生物生物量碳、氮含量之间差异达到显著水平(P<0.01).在观测的3个季节内,幼龄林腐殖质层的微生物生物量碳基本无变化,而成熟林的微生物生物量碳在秋季达到最高;两种林龄落叶松微生物生物量氮均在夏季达到最高.在矿化层,两种林龄落叶松微生物生物量碳、氮均在秋季达到最大.相关分析发现,微生物生物量碳、氮之间以及土壤微生物生物量碳、氮与土壤有机碳、全氮呈显著正相关,而与土壤水分无相关性;另外,落叶松人工林内的灌木种类和数量以及季节性温度变化对土壤微生物生物量碳氮也有影响.上述结果表明,研究区域土壤微生物生物量碳、氮的季节波动与土壤养分状况密切相关,幼龄林土壤养分状况优于成熟林.     

杉木成熟林细根形态与功能特征的海拔梯度变异特点

为探究植物对环境变化的适应策略,在安徽省金寨县天马国家自然保护区,以不同海拔高度(750、850、1000、1150 m)杉木(Cunninghamia lanceolata)成熟林为对象,采用土钻法获取土壤细根样品,分别测定了不同海拔不同土层(0—10 cm、10—20 cm、20—30 cm)土壤细根生物量、形态特征参数和碳氮含量。结果表明:(1)随海拔梯度增加,0—30 cm土层细根生物量、根长密度、比根长、表面积密度、体积密度均呈先减少后增加趋势,在海拔750 m生物量最大,其余指标在海拔1150 m最大;随土层深度增加,同一海拔细根生物量、根长密度、表面积密度、体积密度均呈减少趋势。(2)随海拔梯度增加,0—30 cm土层细根C和N含量呈先增加后减少趋势,C/N比呈先减少后增加再减少趋势;随土层深度增加,同一海拔细根C含量呈先减少后增加趋势,N含量呈降低趋势,C/N比呈上升趋势。(3)细根N含量与生物量、根长密度和体积密度显著正相关,C/N比与生物量、根长密度、表面积密度和体积密度极显著负相关。(4)土壤水分对细根生物量及其形态指标影响显著。     

思茅松人工林根系特征与生物量分配

通过研究不同径级思茅松人工林根系特征、地上部分各器官以及根系生物量分配特征,构建以胸径和树高为变量的思茅松人工林各器官生物量的异速生长方程,为思茅松人工林乔木层碳储量的准确测算提供科学依据。结果表明:思茅松的粗根(根径2.0 cm)、大根(1.0~2.0 cm)、中根(0.5~1.0 cm)和小根(0.2~0.5 cm)的根长和比根长随径级增加而增大,细根(0.2 cm)的比根长降低;中根、小根和细根在根生物量中所占的比例随径级增大先减小后增加,粗根和大根先增加后减小;同一径级中,细根的比根长远高于其他根系类型;思茅松各器官生物量分配大小比例为干枝根叶果,树干生物量均占全株生物量50%以上,各器官生物量随着径级的增大而增加,地上生物量和地下生物量之间呈显著正相关。思茅松单株地上部分生物量在2.23~324.95 kg,根生物量在0.52~41.80 kg,根颈、主根和侧根的生物量随径级增加而增加,根颈/主根、根颈/总根、侧根/主根与胸径和树高呈显著正相关,主根/总根与胸径和树高呈显著负相关;思茅松人工林各器官和总生物量异速生长模型的非线性回归与对数转换后的线性回归的AIC差值都大于2,误差为相乘型,选用线性模型更合适。各器官和总生物量线性模型的R_(adj)~2为0.661~0.992,除球果外,加入树高的模型能较好地拟合各器官与全株生物量。     

干旱胁迫对科尔沁沙地榆树幼苗C、N、P化学计量特征的影响

设置适宜水分、轻度、中度和重度干旱胁迫处理(即80%、65%、50%和35%田间持水量),研究干旱胁迫对榆树幼苗不同器官C、N、P化学计量的影响.结果表明:与适宜水分处理相比,干旱胁迫导致C含量在叶、茎、粗根和细根中增加,N含量在叶、茎和粗根中增加,P含量在叶、茎和粗根中下降,在细根中增加,C:N在叶和茎中下降,C:P及N:P在叶、茎和粗根中增加,在细根中下降.各器官间C含量呈显著正相关,而各器官间N与P相关性均不显著.土壤含水量与各器官C含量,叶N含量,细根P含量及C:N,叶、茎和粗根C:P及N:P呈显著负相关,而与细根N含量,叶、茎和粗根P含量,细根C:P及N:P呈显著正相关.因此,干旱胁迫影响榆树幼苗对N、P的吸收及向上运输,幼苗生长主要受N限制;随着干旱胁迫的加剧,叶、茎和粗根生长受P限制作用增强.     

漓江水陆交错带典型立地根系分布与土壤性质的关系

研究根系与土壤关系是发掘河岸带生态退化等问题内在原因的重要途径。在漓江流域水陆交错带选取缓坡、陡坡、江心洲、人工岸坡4种典型立地类型,对不同土层深度的根长密度、根系生物量、比根长,以及根系特征与土壤有机质、全氮、有效磷的关系进行了研究,旨在为漓江流域生态修复过程中植被恢复、植被配置、快速绿化材料选取提供科学依据。结果表明:(1)同一立地类型0—10 cm土层和10—20 cm土层比根长差异性不显著。0—10 cm到10—20 cm土层,各立地类型根长密度和根系生物量密度均减小,但不同立地类型根长密度和根系生物量密度的差异程度逐渐缩小,表明地形、地表植物类型及生长状况对根长密度分布的影响也随土层深度的增加而逐渐减小。细根根长和生物量随着土壤深度的增加而减小。(2)土壤有机质含量差异性显著,分布规律为人工岸坡陡坡江心洲缓坡;土壤全氮含量从大到小依次是人工岸坡、陡坡、缓坡、江心洲,其值分别为:3.12、2.33、1.56、1.32 g/kg;土壤全氮与土壤有机质呈显著正相关。江心洲和缓坡有效磷含量远远大于人工岸坡和陡坡,原因是漓江水长期受人为洗漱影响,导致受江水干扰大的立地类型有效磷含量高。(3)根长密度、比根长、根系生物量与有机质、全氮含量呈正相关,与有效磷含量呈负相关,说明土壤根系越丰富,越有利于增加土壤有机质和全氮含量,但遏制了土壤有效磷。细根长度、生物量与根长密度在0.01水平(双侧)上显著正相关,与根系生物量密度呈负相关。     

Foreign exploration for Scirtothrips perseae Nakahara (Thysanoptera: Thripidae) and associated natural enemies on avocado (Persea americana Miller)

Scirtothrips perseae Nakahara was discovered attacking avocados in California, USA, in 1996. Host plant surveys in California indicated that S. perseae has a highly restricted host range with larvae being found only on avocados, while adults were collected from 11 different plant species. As part of a management program for this pest, a “classical” biological control program was initiated and foreign exploration was conducted to delineate the home range of S. perseae, to survey for associated natural enemies and inventory other species of phytophagous thrips on avocados grown in Mexico, Guatemala, Costa Rica, the Dominican Republic, Trinidad, and Brazil. Foreign exploration efforts indicate that S. perseae occurs on avocados grown at high altitudes (>1500 m) from Uruapan in Mexico south to areas around Guatemala City in Guatemala. In Costa Rica, S. perseae is replaced by an undescribed congener as the dominant phytophagous thrips on avocados grown at high altitudes (>1300 m). No species of Scirtothrips were found on avocados in the Dominican Republic, Trinidad, or Brazil. In total, 2136 phytophagous thrips were collected and identified, representing over 47 identified species from at least 19 genera. The significance of these species records is discussed. Of collected material 4% were potential thrips biological control agents. Natural enemies were dominated by six genera of predatory thrips (Aeolothrips, Aleurodothrips, Franklinothrips, Leptothrips, Scolothrips, and Karnyothrips). One genus each of parasitoid (Ceranisus) and predatory mite (Balaustium) were found. Based on the results of our sampling techniques, prospects for the importation of thrips natural enemies for use in a “classical” biological control program in California against S. perseae are not promising.     

Molecular phylogeny of Phebalium (Rutaceae: Boronieae) and related genera based on the nrDNA regions ITS 1+2

Parsimony analyses of the internal transcribed spacer regions of nuclear ribosomal DNA (ITS 1 & ITS 2) for 38 taxa sampled from the Phebalium group (Rutaceae: Boronieae) and two outgroups confirm that, with the exception of Phebalium sensu stricto and Rhadinothamnus, six of the currently recognised genera within the group are monophyletic. The data indicate that Phebaliums. str. is paraphyletic with respect to Microcybe, and Rhadinothamnus is paraphyletic with respect to Chorilaena. Rhadinothamnus and Chorilaena together are the sister group to Nematolepis. Drummondita, included as an outgroup taxon, clustered within the ingroup as sister to Muiriantha and related to Asterolasia.The phylogeny suggests that the evolution of major clades within a number of these genera (e.g. Phebalium) relates to vicariance events between eastern and south-western Australia. Leionema is an eastern genus, with the most basal taxon being the morphologically distinct Leionema ellipticum from northern Queensland. Leionema also includes one species from New Zealand, but this species (as with some others) proved difficult to sequence and its phylogenetic position remains unknown. Taxonomic changes at the generic level are recommended.The authors wish to thank Paul G.Wilson, PERTH, for advice and discussion, and Paul Forster, BRI, for collecting and providing material of Leionema ellipticum. The project was supported by a Melbourne University Postgraduate Award (to BM), the Australian Biological Resources Study (ABRS), Australian Systematic Botany Society and Wolf Den (Australia) Investments.     

New species and new combinations in Peruvian Orchidaceae

seventeen new species and combinations are proposed in the generaChondrorhyncha, Cischweinfia, Cochlioda, Eloyella, Encyclia, Kefersteinia, Koellensteinia, Macroclinium, Rodriguezia, Solenidiopsis, andStenia. All new species are illustrated. A key is provided for 2-flowered species ofMacroclinium, PeruvianSigmatostalix, and PeruvianStenia. Solenidium (Solenidiopsis) peruvianum Schltr. is lectotypified.     

Entwicklungsgeschichte und Ultrastruktur von Pollenkitt und Exine bei nahe verwandten entomophilen und anemophilen Angiospermensippen derAlismataceae,Liliaceae, Juncaceae,Cyperaceae, Poaceae undAraceae

Some closely related members of the monocotyledonous familiesAlismataceae, Liliaceae, Juncaceae, Cyperaceae, Poaceae andAraceae with variable modes of pollination (insect- and wind-pollination) were studied in relation to the ultrastructure of pollenkitt and exine (amount, consistency and distribution of pollenkitt on the surface of pollen grains). The character syndromes of pollen cementing in entomophilous, anemophilous and intermediate (ambophilous or amphiphilous) monocotyledons are the same in principal as in dicotyledons. Comparing present with former results one can summarize: 1) The pollenkitt is always produced in the same manner by the anther tapetum in all angiosperm sub-classes. 2) The variable stickiness of entomophilous and anemophilous pollen always depends on the particular distribution and consistency of the pollenkitt, but not its amount on the pollen surface. 3) The mostly dry and powdery pollen of anemophilous plants always contains a variable amount of inactive pollenkitt in its exine cavities. 4) A step-by step change of the pollen cementing syndrome can be observed from entomophily towards anemophily. 5) From the omnipresence of pollenkitt in all wind-pollinated angiosperms studied one can conclude that the ancestors of anemophilous angiosperms probably have been zoophilous (i.e. entomophilous) throughout.

     

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.     

安徽牯牛降的丝孢菌Ⅰ

本文报导作者采自安徽枯牛降自然保护区的18种丝孢菌,分属于5个属,其中有3个新种:牛皮冻生尾孢(Cercospora paederiicola),山鸡椒假尾饱(Pseudocercospora litseae-cubebae),鸡血藤生假尾孢(P. millettiicola)和2个中国新纪录。文中对新种进行了描述及绘图,新记录种作了简要说明。研究的标本保存在中国科学院微生物研究所真菌标本室(HMAS)。     

Changes of dung beetle communities from rainforests towards agroforestry systems and annual cultures in Sulawesi (Indonesia)

Little is known about how tropical land-use systems contribute to the conservation of functionally important insect groups, including dung beetles. In a study at the margin of Lore Lindu National Park (a biodiversity hotspot in Central Sulawesi, Indonesia) dung-beetle communities were sampled in natural forest, young secondary forest, agroforestry systems (cacao plantations with shade trees) and annual cultures (maize fields), each with four replicates (n = 16 sites). At each site we used 10 pitfall traps, baited with cattle dung, along a 100 m transect for six 3-day periods. The number of trapped specimens and species richness at the natural forest sites was higher than in all land-use systems, which did not significantly differ. Each land-use system contained, on average, 75% of the species richness of the natural forest, thereby indicating their importance for conservation. However, a two-dimensional scaling plot based on NESS indices (m = 6) indicated distinct dung beetle communities for both forest types, while agroforestry systems and annual cultures exhibited a pronounced overlap. Mean body size of dung beetles was not significantly influenced by land-use intensity. Five of the six most abundant dung beetle species were recorded in all habitats, whereas the abundance of five other species was significantly related to habitat type. Mean local abundance and number of occupied sites were closely correlated, further indicating little habitat specialisation. The low dung beetle diversity (total of 18 recorded species) may be due to the absence of larger mammals in Sulawesi during historical times, even though Sulawesi is the largest island of Wallacea. In conclusion, the dung beetle fauna of the lower montane forest zone in Central Sulawesi appears to be relatively robust to man-made habitat changes and the majority of species did not exhibit strong habitat preferences.     

Phylogenetic investigations of Sordariaceae based on multiple gene sequences and morphology

The family Sordariaceae incorporates a number of fungi that are excellent model organisms for various biological, biochemical, ecological, genetic and evolutionary studies. To determine the evolutionary relationships within this group and their respective phylogenetic placements, multiple-gene sequences (partial nuclear 28S ribosomal DNA, nuclear ITS ribosomal DNA and partial nuclear β-tubulin) were analysed using maximum parsimony and Bayesian analyses. Analyses of different gene datasets were performed individually and then combined to generate phylogenies. We report that Sordariaceae, with the exclusion Apodus and Diplogelasinospora, is a monophyletic group. Apodus and Diplogelasinospora are related to Lasiosphaeriaceae. Multiple gene analyses suggest that the spore sheath is not a phylogenetically significant character to segregate Asordaria from Sordaria. Smooth-spored Sordaria species (including so-called Asordaria species) constitute a natural group. Asordaria is therefore congeneric with Sordaria. Anixiella species nested among Gelasinospora species, providing further evidence that non-ostiolate ascomata have evolved from ostiolate ascomata on several independent occasions. This study agrees with previous studies that show heterothallic Neurospora species to be monophyletic, but that homothallic ones may have a multiple origins. Although Gelasinospora and Neurospora are closely related and not resolved as monophyletic groups, there is insufficient evidence to place currently accepted Gelasinospora and Neurospora species into the same genus.     

Die GattungKarschia — Bindeglied zwischen bitunicaten Ascomyceten und lecanoralen Flechtenpilzen?

The genusKarschia, in the earlier sense, including saprophytes and parasites on lichens, has been thought to be a non-lichenized parallel genus of the lichen genusBuellia. Modern workers included it on the one hand inBuellia, on the other hand combined it with bitunicate ascomycetes. It is now proved thatKarschia is heterogeneous and contains but superficially similar members both of the genusBuellia of theLecanorales and of typical or masked bitunicateAscomycetes. Therefore, it can not be regarded as a link betweenLecanorales andDothideales. The type species ofKarschia belongs to theDothideales.