Schoenus vegetation and environmental conditions in South and Southeast Sweden

Summary The relations between the Schoenus phytocoena and their site conditions are elucidated by stand and species ordinations (ORDINA, RA) and by comparisons of ordinations of environmental variables alone and ordination of the combined environmental and species variables (RA). Correlations between the environmental variables show that they may be gathered into two contrasting groups, the carbon and the carbonate groupings, respectively. This first direction of variation is related to hydrological conditions causing the differences in thickness of organic soils, content of organic carbon and dry weight of intact soil per unit volume. The second direction of variation is associated with a nutrient factor complex, in this study represented by available phosphate.The carbon grouping and a constantly high level of mainly topogeneous soil water is typical of sites of the Oxycoccus-Schoenus association. The Sesleria group of the Primula-Schoenus association is related to sites with a periodically low table of topogeneous or soligeneous soil water and mineral or mucky soils with high values of carbonate content, pH and CEC and a fairly low nutrient state, while the sites of the Bartsia-Ophrys and Valeriana groups have a fairly high level of mainly soligeneous soil water and mucky soils with variable carbonate content, intermediate pH and CEC and somewhat higher nutrient state. Periodically flooded sites with topogeneous soil water and mineral soils are typical of the Cladium-Schoenus nigricans, Schoenus intermedius-Schoenus ferrugineus and Glaux phytocoena.Nomenclature is the same as in Tyler (1980).This study is part of my doctor's thesis. I am most grateful to Professor Nils Malmer, Head of the Department, for variable advice and discussions. My thanks are also rendered to Dr. E. van der Maarel, University of Nijmegen, The Netherlands, Dr. R.S. Clymo, Westfield College, University of London, Great Britain, Fil kand. Stefan Persson, Dr. Germund Tyler, Mrs Maj-Britt Larsson, Mrs Anita Balogh, Mrs Mimmi Varga, Mrs Kerstin Richter, and Mr Robert Dewsnap.     

Soil acidity and distribution of species on tussocks and interspaces in schoenus vegetation of South and Southeast Sweden

Summary In five South Swedish provinces the vertical distribution of species in Schoenus phytocoenoses, especially bryophytes, were studied by belt transects and analysed by RA. Results indicate that the sequence of bryophyte dominants: Scorpidium scorpioides-Drepanocladus revolvens-Campylium stellatum-Tomenthypnum nitens-Sphagnum fuscum reported by Du Rietz (1949) is distinctly developed in Uppland. A shorter sequence: Scorpidium scorpioides-Drepanocladus revolvens/Campylium stellatum-Ctenidium molluscum, is developed on Öland. In Skåne and Östergötland it is not possible to demonstrate any bryophyte sequence common to all transects and probable reasons for this are discussed. The distribution of the vascular plants confirmed the results of earlier investigations. Several types of relationships between pH and height above interspaces are found and it is assumed that these relationships are due to water fluctuations.I wish to express my gratitude to Nils Malmer, Head of the Department, for valuable advice, to Germund Tyler for help in the field work, to Robert Dewsnap for revision of the English text, and to Mimmi Varga and Brita Billstein for technical assistance.Nomenclature as in Tyler (1980a).The study is the shortened and revised third part of a doctor's thesis.     

松嫩平原南部主要群落植物多样性的比较研究

应用Ｍａｒｇａｌｅｆ（Ｒ１）和Ｍｅｎｈｉｎｉｃｋ（Ｒ２）丰富度指数、Ｈｉｌｌ多样性指数（Ｎ１,Ｎ２）和Ｐｉｅｌｏｕ均匀度指数（Ｅ）比较研究了松嫩平原南部１４个主要群落的植物多样性、生活型多样性及植物多样性与群落演替的关系结果表明,分布于低平原的羊草－蔓萎陵菜群落的植物多样性和丰富度指数最大,Ｒ１为１１．９６,Ｒ２为５．２４,Ｎ１为１３．９２,Ｎ２为８．７６,分布于固定砂丘的榆树疏林和贝加尔针茅等４个群落有较高的植物多样性,而分布于碱化草甸的角碱蓬等群落植物多样性最小,Ｒ１为１．３１,Ｒ２为０７１,Ｎ１为１．８４,Ｎ２为１．４６．具有较高植物多样性的群落其植物生活型多样性指数也较高．在演替系列中,羊草群落的植物多样性指数介于演替初期和中期阶段之间．     

Effects of fire and agricultural practices on neotropical ant communities

Fire is extensively used in agricultural management in Mexico. There is little information on the effects of those practices on the abundance and diversity of animals that live within these forest soils. We studied the effect of slashing, burning and land use in a tropical deciduous forest on ant communities in the State of Jalisco, Mexico. The original vegetation (tropical deciduous forest) was modified into a corn field. Sampling was carried out in five stages: before slashing, after slashing, after burning, after seeding and after harvest. We found that very severe fires greatly reduced ant diversity. The most important effect of fire was the reduction of ant density, and the change of species composition and trophic guilds. These changes are relevant in the recycling process of energy in the ecosystem.     

Species-area curves and estimates of total species richness in an old-field chronosequence

Average species-area curves were generated for vascular plants in 20 old-fields that were sampled in 1983, 1989, and 1994. These curves were fit with a saturating function to estimate total species richness for each old-field. Additional estimates of total species richness were generated by fitting the same saturating function to subsets of the species area curves and with a first-order jackknife procedure. Estimates of total species richness were strongly correlated with observed species richness. There was limited evidence suggesting that greater sampling was necessary to identify the same proportion of species in older, more species-rich old-fields.     

Phylogenetic analysis of the succession of bacterial communities in the Great South Bay (Long Island)

Bacterial community composition and succession were examined over the course of the summer season in the Great South Bay, Long Island, NY, USA, using a 16S rDNA clone library approach. There was a progression of changes in dominant species in the libraries during the summer of 1997. The July library had several groups dominant, the SAR407 relatives of the alpha-Proteobacteria (24%) and the SAR86 (18%), sulfur-oxidizing symbiont relatives (8%) of the gamma-Proteobacteria, and unidentified Cytophaga-Flexibacter representatives (22%). In August, the Cytophaga-Flexibacter (Gelidibacter sp. and unidentified Cytophaga-Flexibacter representative) and Cyanobacteria (Synechococcus sp.) increased to 28% and 14%, respectively. High GC Gram-positives appeared at 18%, and beta-Proteobacteria (Ralstonia sp.) at 10%. By September these groups had either declined or were absent, while the SAR86 cluster, Pseudoalteromonas and Alteromonas of the gamma-Proteobacteria were dominant in the community (61%). The dominance of open ocean bacteria along with the presence of Aureococcus anophagefferens (Pelagophyceae) in July suggests possible open ocean coupling to bloom events. Many clones in this study were related to previously described clones from a wide distribution of marine environments, substantiating the cosmopolitan nature of pelagic bacteria. Only one isolated bacterium was closely related to 16S rDNA found in the August library.     

Progressive effects of shading on experimental wetland communities over three years

To investigate how the composition of wetland communities changes over time in response to altered light regimes, experimental communities of five Carex and four grass species were subjected to artificial shading (continuous or seasonal) in a three-year field experiment. Shoot number and size was measured after six weeks, and shoot biomass was harvested five times during the experiment. Communities were initially dominated by three grass species in all treatments, but subsequently, the Carex species increased and reached dominance in the control plots, whereas grasses remained dominant in the shaded plots. Shading had no effect on the biomass of communities or of single species in the first year. In the second year, community biomass was still unaffected, but shading reduced the biomass of three Carex species and also reduced species diversity. In the third year, shading reduced community biomass and all Carex species, but not species diversity. The greater shade tolerance of the grasses could not be explained by differences in morphological plasticity: after six weeks of growth all species had increased shoot height in response to shade by 40–70%. Grasses were hardly more plastic than Carex species. We propose that the long-term success of the Carex species in full light was due to a high allocation of biomass to belowground parts, which may have reduced losses caused by repeated harvesting of shoots (a simulation of management in productive wet meadows). Shading probably caused the Carex plants to change their allocation pattern, and thus prevented their progressive increase.     

芝麻香型白酒发酵过程中乳酸菌多样性及其演替规律

【背景】乳酸菌是白酒发酵过程中一类非常重要的微生物,其种类及动态变化对于白酒品质具有重要影响。然而,目前对于芝麻香型白酒发酵过程中乳酸菌群落结构及其演替规律的认识并不全面。【目的】揭示芝麻香型白酒发酵过程中乳酸菌的多样性及菌群的演替规律,为更好地探索白酒酿造机理和控制白酒品质提供生物学依据。【方法】利用高通量测序技术对芝麻香型白酒发酵过程中乳酸菌菌群演替进行跟踪分析,同时采用实时荧光定量PCR对发酵过程中乳酸菌的生物量进行定量分析。【结果】高通量测序结果显示,芝麻香型白酒发酵过程涉及5个属的乳酸菌:魏斯氏菌属(Weissella)、片球菌属(Pediococcus)、乳杆菌属(Lactobacillus)、明串珠菌属(Leuconostoc)和乳球菌属(Lactococcus),共计43种乳酸菌。其中,在发酵过程中平均相对丰度大于0.5%的乳酸菌有10种,分别是类肠膜魏斯氏菌(Weissella paramesenteroides)、食窦魏斯氏菌(Weissella cibaria)、融合魏斯氏菌(Weissella confusa)、戊糖片球菌(Pediococcus pentosaceus)、假肠膜明串珠菌(Leuconostoc pseudomesenteroides)、发酵乳杆菌(Lactobacillus fermentum)、植物乳杆菌(Lactobacillus plantarum)、副干酪乳杆菌(Lactobacillus paracasei)、耐酸乳杆菌(Lactobacillus acetotolerans)和Lactobacillus sp.。在堆积发酵过程中,Weissella属占细菌总量的50%以上,其次是Pediococcus属和Lactobacillus属,而Leuconostoc属和Lactococcus属相对较少。在窖池发酵过程中Lactobacillus属的乳酸菌逐渐成为优势细菌,尤其是Lactobacillus sp.在窖池发酵中后期相对丰度达到80%以上。实时荧光定量PCR结果显示,在堆积发酵和窖池发酵前期乳酸菌总量变化不大;从窖池发酵5 d开始,乳酸菌总量迅速上升,30 d时达到最大值。【结论】对白酒发酵过程中乳酸菌种类及动态变化的研究有助于探究白酒酿造过程中乳酸菌功能,进而解析白酒酿造机理,最终达到控制白酒品质的目的。     

Vegetation development after the exclusion of grazing cattle in a meadow area in the south of Sweden

A study of 24 years of secondary succession was based on data from semi-permanent quadrats from investigations in 1952, 1955, 1968 and 1976, involving two exclosures, the first in a meadow grazed for hundreds of years but now abandoned, the second in a meadow mowed for hundreds of years and grazed for the last 50 years. A first order classification of quadrats produced units, which formed distinct spatial patterns indicating similar gradients, but also differences in response to the ceased grazing, in the two exclosures. A second order classification of units into groups revealed a rather simple structure of spatial and temporal relations. Eleven groups of species with similar behaviour could be recognized within a system of spatial and temporal species distributions. The vegetation in both exclosures developed towards an increased differentiation and heterogeneity or patchiness. The border between two soil types was clearly reflected in the spatial pattern of units. Rates of change were greatest in the beginning and were shown to closely follow logarithmic functions of time. The average number of species per m² decreased in all plots, in some cases as much as 50%. It was concluded that the diversity had decreased as a consequence of decreased species richness, decreased evenness and decreased pattern diversity. Many individual species distributions showed a pattern of nuclei surrounded with marginal belts. Differences in rate of change and persistence of spatial patterns between the plots, could be attributed to the differences in management history. These differences have disappeared as the succession has proceeded. The two exclosures have instead both conformed to the same floristic gradient, in turn based on a similar pattern of environmental gradients, primarily moisture. In the observed changes the emphasis was on the shifting importance of competing species populations, as some gained in importance at the expense of others. Competition has so far been a more important process in the vegetation development than immigration/extinction rates.Nomenclature follows Lid (1974) for vascular plants and Nyholm (1954–69) for mosses.This paper is the third part of a doctor's thesis from the Department of Plant Ecology, University of Lund. I wish to thank Prof. Nils Malmer for valuable advice and discussions, Mrs Mimmi Varga for drawing the figures and all my colleagues at the Department for their help and support.     

Changes in soil and vegetation during dune slack succession

Many rare plant species occur in Dutch wet dune slacks, particularly in the Junco baltici‐Schoenetum nigricantis. For nature management it is important to understand the processes controlling the presence of these basiphilous early successional communities, which is why we investigated vegetation and soil development during succession in coastal dune slacks. We compared 12 chronosequential stages of 0, 2, 4, 9, 10, 13, 25, 30, 43, 60, 70 and 85 yr in five different dune slack systems. In four of these locations turf had earlier been removed in order to restore the basiphilous pioneer stage. The main variation in the vegetation is related to the acidification/soil enrichment gradient and the salinity/maritime gradient. During succession, organic matter accumulates and acidification takes place. Maritime influence can buffer the soil and postpone the succession of basiphilous pioneer communities for many years. A significant correlation with age was found for 18 variables. Multiple regressions predicted changes in the vegetation (dependent variables: biomass, cover of Salix repens, Calamagrostis epigejos and Schoenus nigricans) as a function of acidification, organic matter accumulation, increase in available P and presence of Na in the soil. We conclude that natural ageing of the vegetation and the associated process of accumulation of biomass drive succession in this hydrosere. The underlying soil processes are acidification and organic matter accumulation. During succession dominance shifts from S. nigricans to S. repens or C. epigejos. Maintenance of the pioneer character of the habitat is only possible by local intervention or by natural or man‐induced dune forming. The effect of sod‐stripping depends on the environmental conditions and, in case of acidification, success is limited. Succession can be postponed by mowing.     

甘肃兴隆山自然保护区森林演替对鸟类群落结构的影响

运用固定面积法调查了青林三个主要演替阶段森林(阔叶林、混交林和针叶林)的鸟类群落结构。结果表明,混交林中鸟类物种数、鸟类物种多样性和种团多样性最高,阔叶林最低。方差分析和聚类分析均表明,三种演替阶段森林的鸟类群落组成差异显著。所记录到的35种鸟类中有11种差异显著。其中,山雀科和科在阔叶林中占优势,而柳莺亚科在混交林和针叶林中占优势。食性种团中,阔叶林以食虫鸟和食果食虫鸟为主;混交林和针叶林均以食虫鸟、食果食虫鸟、食谷鸟和食果鸟为主。鉴于阔叶林和混交林有向顶级群落(针叶林)演替的趋势,建议采取人为干扰来维持三种演替阶段森林的面积,以便从景观水平上保护鸟类物种多样性。     

Species diversities analyzed by density and cover in an early volcanic succession

To evaluate alpha diversities, various variables such as density, cover, volume, and weight have been used. However, density is often a distinct variable from the remaining three. To clarify differences in diversity measured by those two kinds of variables, the data collected in fourteen 2×5 m permanently-marked plots on Mount Usu, Japan, which erupted during 1977 and 1978 in growing seasons from 1983 to 1989 was analyzed, using Shannon's species diversity (H) that is represented as a result of combination of species richness and evenness (J). H and J were evaluated by density (density H and J) and cover (cover H and J). Cover H and J were significantly lower than density H and J, indicating that cover H has different characteristics from density H. Those differences are due to differences in evenness, because species richness is the same. The rank orders of species density are different from those of cover. The predominance of a few perennial herbs greatly decreases cover evenness, while seedling establishment success influences density evenness. Therefore, I propose that, during the early stages of succession on harsh environments such as volcanoes, density diversity represents seedling establishment success rate while cover diversity expresses vegetative reproduction success rate.     

Molecular diversity of soil basidiomycete communities in northern-central New South Wales, Australia

Basidiomycete communities were profiled using terminal RFLP (TRFLP) and amplified ribosomal DNA restriction analysis (ARDRA) approaches at seven field sites under differing land use in northern-central New South Wales (NSW), Australia. TRFLP data indicated greater basidiomycete species richness at sites with natural vegetation. Sixty-seven basidiomycete ARDRA-types were detected. Various putatively ectomycorrhizal fungi were detected at all sites with native vegetation. Most ectomycorrhizal taxa had affinities to the genus Tomentella, while two Pisolithus taxa and putatively ectomycorrhizal Cantharellales taxa were also detected. Although soils under woodland or grassland communities supported a range of putatively saprotrophic taxa, only members of the Ceratobasidiales were detected in soils under agricultural land use. This study is the first investigation of fungal communities in soils of northern-central NSW, Australia.     

Vegetation development in dune slacks: the role of persistent seed banks

Abstract. The soil seed bank composition was determined at four sites in the dune slack ‘Koegelwieck’ on the Dutch Wadden Sea island of Terschelling. At three different sites in the slack, where sod-cutting experiments down to the mineral sand had been carried out, the established vegetation and seed bank were assessed after 5, 9 and 39 yr of undisturbed development, respectively. In addition, a fourth site in the slack was investigated, where vegetation development had proceeded for 80 yr since plant colonization of bare soil and where nowadays a vegetation dominated by Calamagrostis epigejos and Salix repens occurs. Together these four sites can be regarded as a chronosequence of dune slack formation. Clear time sequences were detected in the seed bank data. Many late successional species showed a significant increase in the number of seeds during the succession. Some of the early successional basiphilous pioneer species such as Anagallis minima, Centaurium littorale, Littorella uniflora, Radiola linoides and Samolus valerandi, showed either a decrease during the time of succession or an optimum in the vegetation while remaining present in the seed bank in low but detectable numbers. They could, therefore, play a role in re-establishment of the vegetation after sod-cutting. One of the target species, Schoenus nigricans, established within a few years after removal of the sod. However, no seeds of this species have been detected in the soil below either of the successional stages. Based on the species disappearance from the established vegetation and based on the independent data of Thompson et al. (1997) an estimation of seed longevity could be made for several Red List species of wet dune slacks.     

On the dynamics of vegetation: Succession in model communities

Summary Successional change is thought to be at least partially driven by forees originating from within the community, namely by reaction and competition. Both processes operate through changes in the environment, but from the literature on the subject it is not clear how they differ.To clarify these issues successiens of model communities are studied. This leads us to conclude that competition represent an instantaneous interaction, whereas reaction has historical aspects since it relies on cumulative changes in the environment. The three models considered-one relying on reaction to cause vegetational change, one relying on competition and differential growth rates, and a hybrid third one-yield very similar predictions: roughly bell-shaped curves displaced along the time axis. This shows that the mere fit of a certain model to successional data may easily be spurious (recently some workers have empirically fitted models identical to one derived here from first principles). The three models do behave radically different under perturbation, however: any model relying completely or partially on historical interactions cannot account for the well known possibility of artificially arresting succession. Even if the importance of historical interactions in succession (i.e. the Markovian character of succession) cannot easily be ascertained, one can nevertheless ask whether historical interactions are at all necessary for the explanation of successional change. It is argued here that succession can be entirely understood in terms of instantaneous interactions, notably competition. The argument rests upon the well known relationship between colonizing and competitive ability, and on the fact, proven here, that stress, defined as expressing itself in severe random fluctuations in the growth parameters, is negatively correlated with competition intensity.The author gratefully acknowledges the critical support be received from Professor László Orlóci. This paper forms part of a wider research program supported by a NCR grant to Proc. Orlóci.     

Deterministic processes have limited impacts on foliar fungal endophyte communities along a savanna-forest successional gradient

Patterns and drivers of succession provide insight into the mechanisms that govern community assembly, but remain poorly understood for microbial communities. We assess whether successional trends of trees are mirrored by foliar endophyte communities of three tree species across a deterministic woody successional gradient. Additionally, we test the relative contribution of abiotic predictors, biotic factors, and spatial distance between sites in predicting composition and richness of endophyte communities. Unlike the tree community, endophyte communities showed no consistent evidence of deterministic succession. Host identity was the most important factor structuring endophyte community composition; within hosts, spatial distance from the indigenous forest and between samples was important, while environmental predictors had small and inconsistent effects. Much variation in endophyte composition remained unexplained. In contrast, endophyte richness was well-explained by predictor variables. Host identity was most important in predicting endophyte richness, while the effect of other predictors on richness differed between host species. We conclude that deterministic succession in trees did not result in deterministic succession in endophyte communities; instead community assembly was most strongly influenced by host identity; while within hosts, neutral processes may be more important for endophyte assembly than deterministic factors.     

用Amp-FLP方法分析江浙沪汉族人群DIS80位点多态性

采用PCR结合PAGE电泳及银染技术,即Amp-FLP方法,分析了148名江浙沪汉族人中D1S80位点的多态性分布,观察到20种等位基因,53种基因型。首次在国际上发现重复单元数为39的等位基因。该位点观察杂合性为0.86,个体鉴别力为0.96,多态性信息含量为0.83,基因频率分布符合Hardy-Weinb erg法则。本文结果提示,采用Amp-FLP技术分析D1S80位点多态性,样本分型具有较高的准确性及灵敏度,适用于人类民族演变、法医学个体指认、亲子鉴定、遗传病基因连锁分析等研究领域。     

人体鼻咽部微生物群落多样性研究进展

定殖于鼻咽部的微生物与人体始终处于动态生态平衡,对于维持人体健康发挥着重要作用,也与多种上呼吸道疾病的发生发展有密切关系。鼻咽部微生物之间及其与宿主之间的相互作用是引发人体上呼吸道疾病的重要因素。微生物的培养方法与分子生物学技术的结合使人们越来越深入地了解人体鼻咽部微生物群落的组成和结构。定殖于人体鼻咽部的微生物以肺炎链球菌(Streptococcus pneumoniae)和流感嗜血杆菌(Haemophilus influenzae)等潜在致病菌为主。本文将分别从鼻咽部微生物与机体的平衡关系、鼻咽部微生物群落的研究方法以及鼻咽部微生物群落的组成及其相互关系三个方面,综述近年来鼻咽部微生物群落结构的相关研究进展,从而为指导实践提供可靠的理论依据。     

Structure of biological soil crust communities in Callitris glaucophylla woodlands of New South Wales,Australia

Question: What is the nature of the relationships between cover, diversity and abundance of biological soil crusts, cover and diversity of vascular plants, and annual rainfall, soil texture and forestry practices in Callitris glaucophylla woodlands? Location: Arid and semi‐arid Callitris glaucophylla‐domi‐nated woodlands of eastern Australia. Methods: We documented soil crust‐forming mosses, lichens and liverworts at 83 woodland sites along a gradient of declining rainfall. Linear and non‐linear regression were used to examine relationships between soil crust species and attributes of vascular plant communities, and a similarity matrix (species abundance X sites) was subjected to Non‐metric Multi‐Dimensional Scaling (MDS), and Analysis of Similarities (ANOSIM) to show the degree of association between groups of taxa, and soil texture, rainfall classes and forestry practices. Results : We collected 86 taxa. Mosses were dominated by the family Pottiaceae, and lichens were dominated by squamulose forms. Average annual rainfall was highly correlated with soil crust community composition, and loamy soils supported a greater cover and diversity of taxa compared with sandy soils. Increases in tree cover were associated with significant, though weak, increases in abundance, but not diversity, of crusts. Crusts tended to be more diverse in areas that (1) had a sparse cover of ground‐storey plants; (2) were relatively stable ‐ as indicated by the proportion of perennial and/or native plants; (3) had more stable soil surfaces; and (4) were unlogged. Litter cover, overstorey thinning, and livestock grazing had no appreciable effect on crust diversity or cover. Conclusions : Callitris glaucophylla woodlands provide substantial habitat for soil crust organisms, and the dense tree cover and closed canopies of Callitris do not appear to have a major influence on the structure of biological crust communities. Unlike other woodland systems, relatively few patches would be required to reserve a high diversity of crust species.