Intraspecific variation in plant size,secondary plant compounds,herbivory and parasitoid assemblages during secondary succession

During secondary succession on abandoned agricultural fields the diversity and abundance of insect communities often increases, whereas the performance and nutritional quality of early successional plants often declines. As the diversity and abundance of insects on a single plant are determined by characteristics of the environment as well as of the host plant, it is difficult to predict how insects associated with a single plant species will change during succession. We examined how plant characteristics of the early successional plant species ragwort (Jacobaea vulgaris), and the herbivores and parasitoids associated with these plants change during secondary succession. In ten grasslands that differed in time since abandonment (3–26 years), we measured the size and primary and secondary chemistry of individual ragwort plants. For each plant we also recorded the presence of herbivores in flowers, leaves and stems, and reared parasitoids from these plant parts. Ragwort plants were significantly larger but had lower nitrogen concentrations in recently abandoned sites than in older sites. Pyrrolizidine alkaloid (PA) composition varied among plants within sites but also differed significantly among sites. However, there was no relationship between the age of a site and PA composition. Even though plant size decreased with time since abandonment, the abundance of stem-boring insects and parasitoids emerging from stems significantly increased with site age. The proportion of plants with flower and leaf herbivory and the number of parasitoids emerging from flowers and leaves was not related to site age. Parasitoid diversity significantly increased with site age. The results of our study show that ragwort and insect characteristics both change during secondary succession, but that insect herbivore and parasitoid abundances are not directly related to plant size or nutritional quality.     

药用植物绶草(兰科)的菌根真菌群落组成分析

兰科菌根真菌(OMF)被认为是影响兰科植物物种丰度和分布的一个重要因素.对广域分布兰科植物的菌根区系进行研究有助于人们更深入地了解兰科植物分布格局的形成机制.本研究以我国广域分布的兰科药用植物绶草Spiranthes sinensis为材料,采用Illumina Miseq高通量测序技术对北京、上海、江西、广西、云南、...     

Study of the effects of temperature, pH, NaCl, and aw on the proteolytic and lipolytic activities of cheese-related lactic acid bacteria by quadratic response surface methodology

The individual and interactive effects of temperature, pH, NaCl, and a_w on the proteolytic and lipolytic activities of Lactobacillus delbrueckii subsp. bulgaricus B397, Lactococcus lactis subsp. lactis T12, and Lb. plantarum 2739 were studied by quadratic response surface methodology. The effects on enzyme activities depended on the interactions among the independent variables, type of activity, substrate and, especially, species. The proteinase activity of strains B397 and T12 was affected differently by pH as individual or interactive terms depending on the type of substrate _sl- or β-casein. The increase of NaCl concentration (2.5–7.5%) under cheese-like conditions had a negative effect on the proteinase activity of strain T12. The effect of NaCl was related to the corresponding decrease in a_w. Aminopeptidases N and A, iminopeptidase and endopeptidase of Lc. lactis subsp. lactis T12 were strongly inhibited by pH 5–6 and NaCl concentration higher than 3.75%. The negative effects of these independent variables was in several cases enhanced by their interaction and/or by the interaction with the lowest temperatures. In contrast, the same peptidases of Lb. plantarum 2739 retained a high activity under the very hostile environmental conditions. Iminopeptidase and especially endopeptidase activities of strain 2739 were stimulated slightly by NaCl at concentrations up to 5%. Lipase/esterase activity of Lb. delbrueckii subsp. bulgaricus B397 was markedly inhibited under cheese-like conditions.     

亚热带树种转换对林地土壤微生物群落结构和功能的影响

通过分析杉木采伐迹地营造阔叶树种尾巨桉和固氮树种黑木相思人工林后土壤微生物群落组成和酶活性,探讨造林树种转换对于改善杉木林地土壤微生物特性的影响.结果表明: 树种转换对土壤微生物群落组成和酶活性的影响主要局限于0～10 cm土壤层.杉木转换为固氮树种黑木相思后,显著提高了0～10 cm土壤层总脂肪酸含量、真菌、革兰氏阳性细菌、革兰氏阴性细菌和放线菌生物量.主成分分析表明,黑木相思人工林土壤微生物群落组成与杉木和尾巨桉人工林具有显著差异,土壤中革兰氏阳性细菌、阴性细菌和放线菌丰度显著提高.在0～10 cm土壤层,黑木相思人工林土壤纤维素水解酶、乙酰氨基-葡萄糖苷酶和酸性磷酸酶活性均显著高于杉木和尾巨桉人工林.研究表明,杉木转变为固氮树种黑木相思后会显著提高微生物生物量和酶活性,有助于土壤有机质的恢复,加快养分循环过程.     

Production of carotenoids by protoplasts of the fungus Acremonium diospyri

Protoplast yields from the fungus Acremonium diospyri, prepared using Novozym 234, were affected by culture age, osmotic stabilizer and its concentration, and incubation time. Protoplasts were released by extension through pores in small hyphal fragments produced by enzyme action on the mycelium, and regeneration was similar to that reported for other fungi. Stabilized protoplasts were shown to synthesize carotenoids on exposure to light, but their carotenoid composition differed from that of mycelium incubated under the same conditions.     

Essential oils of seven Stachys taxa from Croatia

The essential oils of Stachys alpina L., Stachys officinalis (L.) Trevis., Stachys palustris L., Stachys recta L. subsp. recta, S. recta L. subsp. subcrenata (Vis.) Briq., Stachys salviifolia Ten., and Stachys sylvatica L. were obtained by hydrodistillation and analysed by gas chromatography (GC) and gas chromatography–mass spectrometry (GC–MS). Sesquiterpene hydrocarbons were the main group of constituents of all taxa, except S. alpina, which was rich in oxygenated sesquiterpenes. S. alpina and S. palustris had a significant aldehyde fraction and a high amount of alcohols. Some differences in the essential oil composition of two subspecies of S. recta (S. recta subsp. recta and S. recta subsp. subcrenata), growing under almost identical conditions, have been found.     

Diverse epiphyllous fungi on Cunninghamia leaves from the Oligocene of South China and their paleoecological and paleoclimatic implications

The unique co-occurrence of thyriothecia belonging to three fossil genera of epiphyllous fungi, Stomiopeltites Alvin & Muir (Micropeltidaceae), Callimothallus Dilcher, and Trichothyrites Rosendahl (Microthyriaceae), are reported on the leaves of the same host plant, Cunninghamia shangcunica Kodrul, Gordenko & Sokolova from the Oligocene Shangcun Formation of the Maoming Basin, South China. In China, Stomiopeltites is identified for the first time, Callimothallus is known from the Oligocene and Miocene of Guangxi and Zhejiang provinces, and Trichothyrites previously has been found only in the Eocene palynological assemblages of the Maoming Basin. The presence of abundant and diverse epiphyllous micromycetes, together with the taxonomic composition of the Shangcun megaflora and pollen assemblage, as well as quantitative climatic estimates obtained using Climate Leaf Analysis Multivariate Program, confirm the existence of a warm and humid climate in this region during the late early Oligocene. The geographic and stratigraphic distributions, comparisons with extant analogues, as well as ecological and paleoclimatic implications of the fossil fungi are discussed.     

小叶锦鸡儿灌丛化对典型草原群落结构与生态系统功能的影响

草原灌丛化是全球干旱半干旱地区面临的重要生态问题。灌丛化对草原生态系统结构与功能的影响较为复杂, 有待于在更广泛的区域开展研究。该研究在内蒙古锡林郭勒典型草原选择轻度、中度和重度灌丛化草地, 通过群落调查, 结合植物功能性状和土壤理化性质观测, 研究了小叶锦鸡儿(Caragana microphylla)灌丛化对草原群落结构(物种多样性、功能多样性和功能群组成)和生态系统功能(初级生产力、植被和土壤养分库)的影响。结果表明: 1)不同程度灌丛化草地的物种丰富度、功能性状多样性和群落加权性状平均值差异显著, 其中, 中度灌丛化草地的物种多样性和功能多样性较高, 表明一定程度的灌丛化有利于生物多样性维持。2)重度灌丛化草地的地上净初级生产力(ANPP)显著高于轻度和中度灌丛化草地, 其原因主要是随着灌丛化程度加剧, 群落内一/二年生草本植物显著增加, 而多年生禾草和多年生杂类草显著减少。三个灌丛化草地的植被叶片和土壤碳、氮库差异均不显著。3)灌丛化对草原生态系统功能包括ANPP、植被和土壤养分库均没有直接的影响, 而是通过影响功能群组成、土壤理化性质和功能多样性, 间接地影响生态系统功能; 灌丛化导致功能群发生替代和土壤旱碱化是最重要的生物和非生物因素。     

Plant diversity and seasonal dynamics in forest gaps of varying sizes in Pinus massoniana plantations

人工林目前存在结构单一、土壤退化、生物多样性降低等人类普遍关注的生态问题。马尾松(Pinus massoniana)是长江上游低山丘陵区退耕还林的主要人工林树种。研究采伐林窗对植物物种组成和更新的影响, 对马尾松低效人工林的改造, 提升其生态服务功能具有重要的意义。该文以采伐39年生的马尾松人工林形成的7种不同大小的林窗为研究对象, 分析了不同季节林窗内的植物生活型组成及多样性变化。结果表明: 1)马尾松人工林林下植物以高位芽植物居多, 其次是地面、地下芽植物, 一年生植物较少而缺少地上芽植物。在林窗形成初期, 林窗的高位芽植物比例明显低于林下, 大林窗的高位芽植物比例稍高于小林窗, 地下芽和一年生植物的比例低于小林窗。2)林下的物种丰富度和物种多样性指数显著低于大林窗。不同林窗下植物的丰富度指数、优势度指数、多样性指数也存在显著差异。3)夏季林窗下植物多样性最高, 其次是秋季, 春季多样性最低。1225-1600 m²的大林窗能够促进马尾松人工林植物多样性恢复和植被更新。     

密云水库上游油松人工水源涵养林林下植物多样性与土壤理化特性

以密云水库上游丰宁县4种油松人工水源涵养林(油松×落叶松混交林、油松×蒙古栎混交林、油松×山杏混交林、油松纯林)为对象,研究林下植物多样性与土壤理化性质特征,分析林下植物多样性与土壤因子的相关关系。结果表明: 4种人工水源涵养林林下植物群落组成结构差异显著,油松×山杏混交林林下植物群落物种组成最为丰富,绣线菊、虎榛子和披针薹草为主要优势种。从物种丰富度指数、Simpson优势度指数、Shannon多样性指数、Pielou均匀度指数来看,油松×山杏混交林林下整体植物多样性水平最高,灌木层和草本层植物多样性分别以油松×蒙古栎混交林和油松×山杏混交林最高。4种人工水源涵养林之间除全磷外其他各理化指标均差异显著,油松×山杏混交林土壤理化性质总体最优,油松×蒙古栎混交林最差。土壤毛管孔隙度、pH、有机质为灌木层植物多样性的主要影响因子,土壤pH、毛管持水量为草本层植物多样性的主要影响因子。营造油松×山杏混交林更有利于提高林下植物多样性并促进土壤改良,土壤pH、有机质、毛管孔隙度、毛管持水量为影响研究区林下植物多样性的主导土壤因子。     

The Influence of Tropical Plant Diversity and Composition on Soil Microbial Communities

There is growing interest in understanding the linkages between above- and belowground communities, and very little is known about these linkages in tropical systems. Using an experimental site at La Selva Biological Station, Costa Rica, we examined whether plant diversity, plant community composition, and season influenced microbial communities. We also determined whether soil characteristics were related to differences in microbial communities. Phospholipid fatty acid (PLFA) composition revealed that microbial community composition differed across a plant diversity gradient (plots contained 1, 3, 5, or over 25 species). Plant species identity also was a factor influencing microbial community composition; PLFA composition significantly varied among monocultures, and among three-species combinations that differed in plant species composition. Differences among treatments within each of these comparisons were apparent in all four sampling dates of the study. There was no consistent shift in microbial community composition between wet and dry seasons, although we did see significant changes over time. Of all measured soil characteristics, soil C/N was most often associated with changes in microbial community composition across treatment groups. Our findings provide evidence for human alteration of soil microbial communities via the alteration of plant community composition and diversity and that such changes are mediated in part by changes in soil carbon quality.     

The significance of precipitation and substrate chemistry for epiphytic lichen diversity in spruce-fir forests of the Salish Mountains, northwestern Montana

The relevance of chemical site factors for the abundance of epiphytic lichens was studied in Picea engelmannii-Abies lasiocarpa forests of the Salish Mountains, northwestern Montana, USA. The Salish Mountains are an area with relatively low atmospheric pollutant load and low precipitation. Canonical correspondence analysis (CCA) suggests that cover of several lichen species was limited by high Mn concentrations of bark or by high ratios of Mn to Ca, Mg and Fe. Mn in the bark is known primarily to derive from the soil. An effect of Mn concentration or Mn/Ca and Mn/Mg ratios was not found on A. lasiocarpa. This suggests that A. lasiocarpa deposits Mn in the bark in a physiologically inactive form as already known from A. balsamea. Precipitation chemistry was apparently less relevant for epiphytic lichen distribution in the Salish Mountains, as no correlations between element concentrations in stemflow and cover values were found and as amounts of stemflow were small. However, precipitation in the study year was less than average. The lacking significance of precipitation chemistry is probably the cause why epiphytic lichen vegetation differed less between living and dead trees in the Salish Mountains than in highly polluted coniferous forests studied by our group in Germany; in Germany, the difference between living and dead trees was attributed to reduced interception of pollutants from the atmosphere by trees with reduced crown surface. The result of the present study that small-scale variation of epiphytic lichen abundance is only partly explainable by chemical parameters gives rise to the assumption that microclimate (e.g., moisture), which has not been systematically explored, could be an important site factor for epiphytic lichens in the Salish Mountains. Furthermore, tree age was identified by CCA as a relevant site factor for lichens on P. engelmannii.     

外生菌根真菌土生空团菌种群遗传多样性与结构研究

土生空团菌Cenococcum geophilum是生态系统中广泛分布的外生菌根真菌,具有丰富的遗传多样性和重要的生态功能.为揭示土生空团菌的种群遗传多样性和结构,本研究对采集自中国10个森林地点的桦木科Betulaceae、壳斗科Fagaceae和松科Pinaceae植物根系219份样品高通量测序的土生空团菌ITS2...     

Distribution of secondary metabolites in two subspecies of Todaroa aurea

When Todaroa aurea, endemic to the Canary Islands, was studied, the substances found in the plant from Tenerife proved to be different from those in the plant gathered in La Palma and it seems likely that two subspecies are involved: T. aurea subspq aurea (Tenerife) and T. aurea subsp, suaveolens (La Palma).     

Biosystematics of the genus Pinus, subsection contortae

Gene frequency data from 42 isoenzyme loci were used to assess the phylogeny of taxa in the genus Pinus, subsection Contortae. The classification inferred from a phenogram based on Nei's genetic distance measure (D_N) was generally in good agreement with the current taxonomic treatment of the subsection. Pinus contorta appears to most closely resemble the ancestral taxon from which all other taxa in the subsection are derived. An alternative classification based upon Mahalonobis squared distances (D_R) obtained from seed and cone measurements differed from the isoenzyme treatment by placing P. contorta subsp. murrayana in close association with P. virginiana.     

Potential for woody plant control by Spanish goats in the sagebrush steppe

Botanical composition of the diet of eight Spanish goats was studied on the Northern Great Basin Experimental Range during two stages of plant phenology (active growth in early July and cured forage in mid-August) to assess their potential for the control of sagebrush (Artemisia tridentata sspp. wyomingensis Nutt.) and western juniper (Juniperus occidentalis Hook.) and their nutritional status on sagebrush-steppe rangelands. Diets were quantified by documenting the number of visits to each species, the bites harvested and time expended grazing each forage over 4 consecutive days in each period. Forage chemical characteristics evaluated included: CP, NDF, ADF, ADL and IVDMD. Diet composition and forage quality indices varied significantly (P < 0.05) with changes in plant phenology. Vegetation cover averaged 52% in the pasture and consisted of 36% grasses, 8% forbs, 7% shrubs and 0.6% trees. Available herbage (excluding woody plants) was 534 kg ha⁻¹ during active growth trials and 572 kg ha⁻¹ when forages had cured. When forages were green goats acquired 28% of their total bites from grasses, 71% from forbs, 0.3% from shrubs and 0.9% from juniper trees. After forages had cured values were 35% from grasses, 56% from forbs, 0.1% from shrubs and 8.8% from juniper. The browsing of juniper (both foliage and bark), after herbaceous forages had cured, was the only substantive use of woody plants. Sagebrush was only lightly used (0.2% of total bites) when herbaceous forages were actively growing. Available herbage was of relatively high quality during both trials. When forages were actively growing, CP of grasses ranged from 8.9 to 5.6%, forbs from 17.7 to 8.5%, sagebrush scored at 8.5%, juniper foliage at 8.1% and juniper bark at 3.2%. After herbaceous forages had cured, grass CPs ranged between 6.2 and 3.1%, forbs from 10.4 to 4.4%, shrubs were not sampled and juniper foliage averaged 7.6%. Given the low levels of browsing exhibited by goats on sagebrush and juniper we see little opportunity for control of these woody plants when pastures provide a diverse (N = 25 species) array of readily available (534–572 kg ha⁻¹) and nutritious forages and pastures are lightly stocked (0.63 goats ha⁻¹ month⁻¹). We do need, however, to further explore their potential for control of these species under several other regimes. These include extended trials on more deteriorated rangelands, trials during seasons or conditions where forage is limited and the animal's selective opportunity is restricted and trials in high quality environments on newly established sagebrush and juniper seedlings.     

漓江河岸带植物功能性状变异与关联

研究植物功能性状随环境梯度的变异和关联格局, 对于认识不同环境梯度下群落构建和植物适应型具有重要意义。该研究以漓江河岸带不同河段植物群落为研究对象, 调查了研究区内36个样方的物种组成, 测量了样方内42种木本植物的叶面积(LA)、比叶面积(SLA)和木材密度(WD)的功能性状值, 并运用性状梯度分析法对3个功能性状进行群落内(α组分)和群落间(β组分)组分分解及相关性分析。结果表明: (1)群落平均LA表现为中游最小且和下游差异显著, 群落平均WD则表现为中上游显著高于下游, 群落平均SLA在两两河段间均差异显著。(2)不同河段的3个植物功能性状β组分差异显著且实际观测值均小于随机模拟的零模型分布, 但α组分在河岸带不同河段均差异不显著且3个功 能性状的α组分分布范围均小于β组分, 说明在河岸带不同河段的群落构建过程中环境筛选的作用要大于群落内种间的相互作用。(3)性状SLA与LA在群落间和群落内呈现出实际观测和随机模拟的相关性均较低, 暗示了LA和SLA各自代表了植物在不同生态策略上的维度; 但SLA和WD实际观测值和随机模拟值呈现出较强的负相关关系, 暗示这2个性状对于环境筛选表现出较高的整体趋同适应性, 体现了植物功能性状对群落间环境变异的依赖性大于群落内种间相互作用的依赖性。     

Sensitive and specific detection of Xanthomonas campestris pv campestris by PCR using species-specific primers based on hrpF gene sequences

A sensitive and specific assay was developed to detect bacterial black rot of crucifers caused by Xanthomonas campestris pv. campestris (X. c. pv. campestris), in cabbage seed and plant. Primers XCF and XCR from hrpF homologous to nolX, host recognition protein, were used to amplify a 525 bp DNA fragment. PCR technique was applied to detect the pathogen in naturally infected seed and plant of cabbage. The PCR product was only produced from X. c. pv. campestris among 40 isolates of Xanthomonas strains, Escherichia coli (O157:H7), Pectobacterium carotovorum subsp. carotovorum, and other reference bacteria.     

植株大小、枝龄和环境共同驱动红松枝性状的变异

许多枝性状的变异受植株大小、枝龄或环境的影响, 但少有研究同时评估这些因素对枝性状种内变异的重要性。该研究以红松(Pinus koraiensis)为研究对象, 通过测定69株胸径(DBH) 0.3-100.0 cm范围内植株不同年龄枝的形态性状、化学性状和解剖性状, 探讨植株大小(DBH或树高)、枝龄与环境因素(光照强度、土壤养分及土壤含水率)对枝性状的影响。结果表明: (1) DBH与树高对枝性状的影响存在差异: 木质密度(WD)、木质部面积占比(R_XA)、韧皮部面积占比(R_PHA)及髓面积占比(R_PA)对DBH更敏感, 而树脂道总面积占比(R_RC)和枝氮含量(WN)受树高影响更大; (2)枝龄是导致红松枝性状种内变异的最主要因素, 植株大小次之, 而环境因素的影响最小; (3) WD、R_PHA与DBH显著正相关, R_PA与DBH显著负相关, R_RC、WN与树高显著正相关; 除WN外, 其余枝性状与枝龄均显著相关, 且随着树木生长, R_RC随枝龄增大而减小的速率加剧, 相反, R_PA随枝龄增大而减小的速率减缓。研究结果有助于了解局域尺度上枝性状种内变异的影响因素以及枝条应对环境变异的适应机制。     

新疆北部拟南芥自然居群表型变异与协变

拟南芥(Arabidopsis thaliana)自然居群的表型特征代表其在自然环境下的适应状况, 不同居群间特征的对比可以为了解拟南芥表型变化规律, 进而分析其形成过程和机制提供重要线索。本研究以分布于新疆北部天山、塔尔巴哈台山和阿尔泰山的10个种群的9个表型性状为基础, 对比分析了小尺度、局域尺度和区域尺度环境下原生境拟南芥种群表型性状的变化。结果发现, 不同性状对环境变化的反应不同, 其中株高、株重、根重、根长、单个果实重、果实开裂力度在3种环境尺度下种群间的差异均达到极显著水平, 而分枝数、果实长度的种群间变化不显著, 种群间的表型分化系数较低。不同环境尺度下株重、根重、单株果数均表现出一致的协变格局, 反映了生理功能性状之间整合对拟南芥适应环境的重要性。同时, 各种群间整体的性状协变差异性明显, 根长、单个果实重、分枝数、果实长度、果实开裂力度等特征与其他特征协变具有明显的局部性, 局域尺度和区域尺度环境之间的变化较大。聚类分析发现区域尺度上的不同种群聚合在一起的现象非常突出, 进一步表明拟南芥的表型特征受微环境的强烈影响。Mantel检验表明, 小尺度上10个种群株高、株重、根重、单个果实重、果实长度、果实开裂力度6个性状变化存在显著的空间相关性, 而分枝数、根长的相关性却不显著。因此, 我们认为拟南芥表型变化受小尺度环境的影响强烈, 但在表型层面并非所有性状都与原生境气候存在遗传关联。