Individual Species-Area Relationship of Woody Plant Communities in a Heterogeneous Subtropical Monsoon Rainforest

The spatial structure of species richness is often characterized by the species-area relationship (SAR). However, the SAR approach rarely considers the spatial variability of individual plants that arises from species interactions and species’ habitat associations. Here, we explored how the interactions of individual plants of target species influence SAR patterns at a range of neighborhood distances. We analyzed the data of 113,988 woody plants of 110 species from the Fushan Forest Dynamics Plot (25 ha), northern Taiwan, which is a subtropical rainforest heavily influenced by typhoons. We classified 34 dominant species into 3 species types (i.e., accumulator, repeller, or no effect) by testing how the individual species-area relationship (i.e., statistics describing how neighborhood species richness changes around individuals) of target species departs (i.e., positively, negatively, or with no obvious trend) from a null model that accounts for habitat association. Deviation from the null model suggests that the net effect of species’ interactions increases (accumulate) or decreases (repel) neighborhood species richness. We found that (i) accumulators were dominant at small interaction distances (<10–30 m); (ii) the detection of accumulator species was lower at large interaction distances (>30 m); (iii) repellers were rarely detected; and (iv) large-sized and abundant species tended to be accumulators. The findings suggest that positive species interactions have the potential to accumulate neighborhood species richness, particularly through size- and density-dependent mechanisms. We hypothesized that the frequently disturbed environment of this subtropical rainforest (e.g., typhoon-driven natural disturbances such as landslides, soil erosion, flooding, and windthrow) might create the spatial heterogeneity of species richness and promote positive species interactions.     

A Generalized Approach to the Modeling of the Species-Area Relationship

This paper proposes a statistical generalized species-area model (GSAM) to represent various patterns of species-area relationship (SAR), which is one of the fundamental patterns in ecology. The approach enables the generalization of many preliminary models, as power-curve model, which is commonly used to mathematically describe the SAR. The GSAM is applied to simulated data set of species diversity in areas of different sizes and a real-world data of insects of Hymenoptera order has been modeled. We show that the GSAM enables the identification of the best statistical model and estimates the number of species according to the area.     

Scale, Experimental Design and the Detection of Ineterspecific Competition within Plant Communities

Abstract We report preliminary results of a series of experiments designed to explore the importance of interspecific competition within arable weed communities at different scales. Competition hierarchies were apparent from a pot experiment with different levels of nutrients and water. Two field experiments looked at Bromus sterilis, Galium aparine and Papaver rhoeas in winter wheat in the field, in a range of combinations and management treatments, and a fourth field experiment included a wider variety of species. There was little effect of fertilizer on population behaviour in the the field. Bromus increased around ten fold per year on minimum-tilled plots, regardless of other treatments. Galium increased on organically-fertilized and minimum-tilled plots, but only in the absence of Bromus. Papaver densities remained low, but again were depressed in the presence of high densities of Bromus . Taken together, the experiments demonstrate the existence of competition between weed species. However, as the design of the experiment increased to include greater levels of environmental variation, so competition became more difficult to detect, and less useful for interpreting the results than knowledge of the biology of the individual species. At the scale of interest to the farmer, the level of competition is not a good predictor for weed population dynamics.     

The Effects of Landscape Variables on the Species-Area Relationship during Late-Stage Habitat Fragmentation

Few studies have focused explicitly on the later stages of the fragmentation process, or "late-stage fragmentation", during which habitat area and patch number decrease simultaneously. This lack of attention is despite the fact that many of the anthropogenically fragmented habitats around the world are, or soon will be, in late-stage fragmentation. Understanding the ecological processes and patterns that occur in late-stage fragmentation is critical to protect the species richness in these fragments. We investigated plant species composition on 152 islands in the Thousand Island Lake, China. A random sampling method was used to create simulated fragmented landscapes with different total habitat areas and numbers of patches mimicking the process of late-stage fragmentation. The response of the landscape-scale species-area relationship (LSAR) to fragmentation per se was investigated, and the contribution of inter-specific differences in the responses to late-stage fragmentation was tested. We found that the loss of species at small areas was compensated for by the effects of fragmentation per se, i.e., there were weak area effects on species richness in landscapes due to many patches with irregular shapes and high variation in size. The study also illustrated the importance of inter-specific differences for responses to fragmentation in that the LSARs of rare and common species were differently influenced by the effects of fragmentation per se. In conclusion, our analyses at the landscape scale demonstrate the significant influences of fragmentation per se on area effects and the importance of inter-specific differences for responses to fragmentation in late-stage fragmentation. These findings add to our understanding of the effects of habitat fragmentation on species diversity.     

Plant Communities of Western Amazonia

In this review I focus on the socially and ecologically important western Amazon basin and its associated plant communities. I delineate this vast area as between the Andes to the west and the confluence of the Amazon and its first major black-water river, the Rio Negro, to the east. Although scientists have explored here, and local people have lived here for years, we still have—unfortunately—only a most basic understanding of its plant communities. This review is motivated by that lack of knowledge, and attempts both to add a level of organization to what we do know and to suggest future avenues of research. I do this by first realizing that plant communities here must be fundamentally differentiated by the degree of flooding they experience, the kind of water involved, and how regularly that flooding occurs. Within that context, plant communities can then be further defined by such characteristics as soil type, micro-topological relief, and human-induced disturbance regime. After completing the review, I suggest that the diversity of plant communities, not just the plants themselves, is large and likely to grow substantially as we sample more and more, that is to say the peak of the plant community-sampling area curve has not yet been reached. I close with basic questions to help guide future efforts, ideas on how plant communities could be defined quantitatively, and a call for more research funding of the Western Amazon.     

植物群落中生态位重迭的计测

本文阐明了生态位重迭在植物生态学研究中的重要性。指出植物群落中生态位重迭的计测有不同于动物的特殊性,并建议以群落梯度代替生态因子梯度;以生态距离间隔作为生态位重迭计测公式中的加权因子,使生态位重迭的计测简化。以甘肃省马衔山林区的林下草本植物为例,计测各种对间的生态位重迭。计测分两种情况进行：其一,在光照、土壤水分、土壤有机质三维复合生态因子梯度上;其二,在群落梯度上。二者所得结果,进行了比较分析。最后在讨论中指出：计测生态位重迭时,必须区分部分重迭与完全重迭,区分样方和资源位。     

Pitfalls in Small-Scale Species-Area Sampling and Analysis

Analyses of the dependency of species richness (S) on area (A), the so-called species-area relationships (SARs), are widespread approaches to characterize and compare biodiversity patterns. This article highlights – with a focus on small-scale SARs of plants in continuous ecosystems – how inappropriate sampling methods or theoretical misconceptions can create artifacts and thus may lead to wrong conclusions. Most of these problems have been recognized before but continue to appear regularly in the scientific literature. The following main points are reviewed and discussed: i) Species richness values and SARs depend on the measurement method (any-part vs. grid-point system); ii) Species-richness values depend on the shape of the analyzed plots; iii) Many published SARs are not true SARs but instead represent species sampling curves or their data points consist of richness totals for incontiguous subplots; iv) Nested-plot design is the preferred sampling method for SARs (the claim that this approach would cause pseudoreplication is erroneous); v) SARs should be constructed using mean values of several counts for the smaller areas; vi) SAR functions can be fitted and selected both in the S- and the log S-space but this must be done consistently for all compared function types. It turns out that the finding of non-power function SARs in many studies is due to a lack of awareness of one or several of the named points. Thus, power-function SARs are even more widespread than a recent review would suggest. I therefore propose to use the power law as a universal model for all types of SARs but to test whether the slope z varies with spatial scale. Finally, I urge readers to be aware of the many pitfalls in SAR studies, to fully disclose methodology, and to apply a meaningful and consistent terminology, especially by restricting the terms “species-area relationship” and “species density” to situations in which each data point represents a contiguous area.     

Biogenic Silica Production in Selected Alpine Plant Species and Plant Communities

The biogenic silica extracted from samples of 28 alpine plantspecies belonging to 23 genera and nine families collected inthe Swiss Alps (Valais) accounted for between 0.01 and 5.9%of the dry biomass of leaves and wood. Silica content, and plantcontribution to the soil biogenic silica pool, varied widelyamong taxa. Plant net productivity and biogenic silica productionfrom this study and from the literature have been used to predictthe input made by different subalpine and alpine plant communitiesto soil-borne phytolith assemblages, and their contributionto the silicon biocycle. Copyright 2001 Annals of Botany Company Silicon, productivity, phytoliths, subalpine, alpine, grasslands, heaths, forests, Gramineae, Cyperaceae, Ericaceae, Coniferae     

Crown Architecture and Species Coexistence in Plant Communities

The relationships between crown architecture and species coexistencewere studied using the diffusion model and the canopy photosynthesismodel for multi-species plant communities. The present paperdeals with two species having different crown shapes [conic-canopyplant (CCP) and spheroidal-canopy plant (SCP)], for variousinitial mean sizes at the establishment stage and physiologicalparameter values (photosynthetic rate, etc.). Recruitment processeswere not incorporated into the model, and thus simulations weremade for the effects on the pattern of species coexistence ofeither sapling competition starting from different sapling banksor competition in single-cohort stands with little continualestablishment of species until a stand-replacement disturbance.The following predictions were derived: (1) SCPs can establishlater/slowly in the lower canopy layer even if they are overtoppedby a CCP which established first/rapidly; (2) if SCPs establishedfirst/rapidly and occupy the upper canopy layer, a CCP can rarelyestablish later/slowly in the lower canopy layer; (3) smallest-sizedCCPs can persist well in the lowermost canopy layer overtoppedby a SCP, suggesting a waiting strategy of CCP's saplings inthe understorey of a crowded stand; (4) even if CCPs establishedfirst/rapidly and occupy the upper canopy layer, an SCP canestablish later/slowly in the lower canopy layer. Therefore,the species diversity of SCPs which established first/rapidlyand occupy the upper canopy layer limits the number of CCP specieswhich can establish later/slowly. In contrast, the species diversityof CCPs which established first/rapidly and occupy the uppercanopy layer does not affect the number of SCP species whichcan establish later/slowly. The combination of initial sizesof a CCP and an SCP at the establishment stage (i.e. establishmenttiming) affects the segregation of vertical positions in thecanopy between the two species with different crown shape, andnot only species-specific physiological traits but also crownarchitecture greatly affects the coexistence pattern betweenspecies with different crown architectures. The theoreticalpredictions obtained here can explain coexistence patterns foundin single-cohort conifer-hardwood boreal and sub-boreal forests,pointing to the significance of crown architecture for speciescoexistence. Diffusion equation model; canopy photosynthesis model; conifer-hardwood boreal/sub-boreal forest; sapling establishment; vertical foliage profile     

Ecological Communities Plant Mediation in indirect interaction Webs

Takayuki Ohgushi, Timothy P. Craig and Peter W. Price (Eds)Cambridge University Press ISBN: 9780521850391 £80.00 458pp Reviewed by Patricia Sang

Oxford University PressKing, Stansfield, Mulligan ISBN: 9780195307610 £19.99 596pp Reviewed by Ian Carter

Pallgrave Macmillan Anthony J.F. Griffiths, Susan R. Wessler,Richard C. Lewontin, and Sean B. Carroll ISBN: 9780716799023 £44.99 838pp Reviewed by Olivier Sparagano

British Psychological Society/Blackwell Publishing Julia C. Berryman, Elizabeth Ockleford, Kevin Howells, David J. Hargreaves, and Diane J. Wildbur ISBN: 9781405126984 £18.99 272pp Reviewed by N Souter

Lafferty & Panella Pearson: Benjamin-Cummings ISBN: 9780805395747 £12.12 206pp + CDROM Reviewed by J Mynett     

Diverse Honeydew-Consuming Fungal Communities Associated with Scale Insects

Sooty mould fungi are ubiquitous, abundant consumers of insect-honeydew that have been little-studied. They form a complex of unrelated fungi that coexist and compete for honeydew, which is a chemically complex resource. In this study, we used scanning electron microscopy in combination with T-RFLP community profiling and ITS-based tag-pyrosequencing to extensively describe the sooty mould community associated with the honeydews of two ecologically important New Zealand coelostomidiid scale insects, Coelostomidia wairoensis and Ultracoelostoma brittini. We tested the influence of host plant on the community composition of associated sooty moulds, and undertook limited analyses to examine the influence of scale insect species and geographic location. We report here a previously unknown degree of fungal diversity present in this complex, with pyrosequencing detecting on average 243 operational taxonomic units across the different sooty mould samples. In contrast, T-RFLP detected only a total of 24 different “species” (unique peaks). Nevertheless, both techniques identified similar patterns of diversity suggesting that either method is appropriate for community profiling. The composition of the microbial community associated with individual scale insect species varied although the differences may in part reflect variation in host preference and site. Scanning electron microscopy visualised an intertwined mass of fungal hyphae and fruiting bodies in near-intact physical condition, but was unable to distinguish between the different fungal communities on a morphological level, highlighting the need for molecular research. The substantial diversity revealed for the first time by pyrosequencing and our inability to identify two-thirds of the diversity to further than the fungal division highlights the significant gap in our knowledge of these fungal groups. This study provides a first extensive look at the community diversity of the fungal community closely associated with the keystone insect-honeydew systems of New Zealand’s native forests and suggests there is much to learn about sooty mould communities.     

On the Ordered Development of Plants 2. Self-thinning in Plant Communities

It is shown that the hypothesis that a growing point on a vegetativeplant requires a minimum rate of supply of assimilate to continuegrowth can quantitatively describe self-thinning in communitiesof Trifolium subterraneum. The hypothesis can also be used toexplain the different relationships observed between mean plantweight and plant density when plants are grown in full daylight,70 per cent shade, and transferred between the two light environments.The implications of the hypothesis to self-thinning in naturalplant communities are discussed. Self-thinning, assimilate, plant development     

北京松山自然保护区典型植物群落物种多样性研究

基于2017年对北京松山自然保护区6种典型植物群落物种调查数据,选取α、β多样性指数描述植物群落乔、灌、草本层植被多样性特征,分析影响植物群落多样性的主导因素。结果表明：(1)研究区内共有40科58属75种植物种;主要乔木优势种为油松(Pinus tabulaeformis)、蒙古栎(Quercus mongolica)、毛白杨(Populus tomentosa)和山杨(Populus davidiana);灌木层优势种为土庄绣线菊(Spiraea pubescens Turcz.)和扁担杆(Grewia biloba G. Don);林下草本多以菊科植物(Compositae)为主。(2)不同植物生长型间Shannon Wiener多样性与丰富度指数排序均为草本层＞灌木层＞乔木层;随着山体高度的增加,林下草本α多样性指数增大,草本物种丰富度、均匀度都对其α多样性影响较大。(3)分析从山底到山顶草本β多样性指数的变化趋势发现,草本共有种经历先减少后增加,物种替代率则呈先增大后降低的变化模式。研究认为,在今后生物多样性保护实施过程中,需按照自然演替规律,综合考虑冠层物种组成与结构、微地形的调控作用,制定合理可行的保护经验和技术,为森林群落多样性保护及其生态功能的发挥提供科学支撑。