四川江津四面山常绿阔叶林永久样地的非线性排序

 本文以四川省江津四面山1 ha永久样地的常绿阔叶林为研究对象,利用样地内20个样方优势乔木种的重要值数据,采用主分量分析(PCA),无偏主分量分析(DPC)和非度量多维调节(NMDS)等方法进行分类和排序。PCA分析结果发现样方坐标数据具有非线性,DPC检测证实其非线性相当明显。通过NMDS分析,经过39次反复迭代,获得结果清楚地反映了群落优势种与环境因子的相互关系,为以后的次生演替研究提供了基础资料。     

青海湖北岸植物群落与环境因子关系的初步研究

依据对青海湖北岸 1 8个群落的样方调查和环境因子原始数据 ,用主分量分析 ( PCA)排序技术和回归模型 ,定量分析湖滨平原植物群落在空间地理上的分布格局 ,以及群落结构特征和环境梯度之间的关系。结果表明 :植物群落的类型分布主要决定于环境中的土壤水分含量及土壤全盐含量。代表植物群落结构特征的生物多样性 ( X1)和生态优势度 ( X2 )分别与环境梯度没有显著的相关性 ,但是 ,这两个指标和第一主分量排序轴 (土壤水分度 ,Y)的二元线性回归关系显著 ,回归模型为 :Y =- 4 .85 1 .4 7X1 1 0 .71 X2 ( P <0 .0 1 )。     

海南岛霸王岭林区低海拔热带林群落数量分类与排序

植物群落分类是依据植物群落的特征或属性对植物群落进行划分,是植被生态学的最基本也是最复杂的研究内容。热带林由于其复杂的环境条件及丰富的物种数量导致了其分类更加困难。本文根据海南岛霸王岭林区低海拔热带林群落的野外调查数据,运用二元指示种分析(TWINSPAN)、主分量分析(PCA)及除趋势对应分析(DCA)对该地区低海拔热带林群落进行了数量分类与排序。结果表明:TWINSPAN将21个样地共分成3组:热带低地雨林(样地9—12)、转化型季雨林(样地1—8)和热带季雨林(样地13—21)。PCA和DCA排序结果也得到了相同的结论,同时也反映了植物群落与环境因子的关系,热带低地雨林与海拔和凋落物厚度呈正相关,而热带季雨林与坡度和岩石裸露度呈正相关,转化型季雨林与环境因子的关系在PCA和DCA中则有所不同。DCA排序结果同时也表明,转化型季雨林是介于热带低地雨林和热带季雨林中间的一种群落类型。     

塔里木河中下游湿地及周边植物群落与环境因子的关系初探

选取塔里木河中下游湿地及周边16个典型植物群落样地调查和环境因子数据,采用主分量分析(PCA)排序技术和回归分析,定量分析湿地及周边植物群落在空间上的分布格局,以及群落结构特征和环境梯度之间的关系.结果表明,影响塔里木河中下游湿地及周边植物群落分布的第1主分量中,土壤水分和盐分影响最大,贡献率为35.70％;在第2主分量中,土壤养分的影响最大,贡献率为25.97％.植物群落分布的生境可分为沼生轻盐中营养生境、湿生中盐中营养生境、中生中盐低营养生境和中旱生重盐低营养生境4种类型.沿不同生境依次分布着沼泽植被、草甸植被、河岸疏林和盐生荒漠 盐化灌丛植被.塔里木河中下游湿地及周边植物群落的生态优势度与土壤水分和盐分复合梯度呈显著的一元线性相关.二元回归分析结果显示,塔里木河中下游湿地及周边土壤水分和盐分复合梯度与多样性指数和生态优势度二元指标呈极显著相关.     

江西省水生维管束植物群落与环境因子关系的初步研究

植物群落与环境因子关系的研究是植物生态学的一个中心议题[1],主要通过直接梯度分析和间接梯度分析的方法进行定量描述和解释。排序是梯度分析的一个主要技术[2 ],如极点排序 (ＰＯ)、相互平均法 (ＲＡ)、主分量分析 (ＰＣＡ)、典范分析 (ＣＣＡ)等排序技术已被广泛应用于植被的梯度分析中[1,3]。对于水生维管束植物的研究已有不少报道 ,其中有许多研究者注意到了水环境 (如水深、底质、水化学性质、流速等 )对水生维管束植物生态分布的影响[4,5],但缺乏对水生维管束植物与水环境关系的数量分析研究。据此 ,作者通过对水生维管束植物群落及…     

海南岛热带草地的数量分类和排序研究

本文用一些数量分类和排序的方法对海南岛鹦歌岭热带草地进行了分类和排序。所用的方法包括两种多元等级聚合分类--最近邻体法(NN)和最远邻体法(FN),极点排序(PO)和主分量分析(PCA)排序。结果表明：把19个样地分为三大类型、9个群落,其分布格局与坡度、放牧强度和土壤肥力密切相关。所用的四种方法在热带草地的研究中均有一定的适用性。     

千岛湖岛屿维管植物β多样性及其影响因素

通过样地调查方法、Jaccard相异性指数、Spearman回归分析和非度量多维标度(NMDS)排序分析,研究了千岛湖154个岛屿上不同植物群落β多样性及其主要影响因素。结果表明不同的景观参数对不同植物生长型有不同程度的影响,其中(1)藤本、灌木的β多样性形成的主导因素是面积,即面积差越大的区域间的β多样性越高;(2)乔木的β多样性主要受到岛屿间距离的限制,岛屿间距离越远,β多样性越高;(3)草本植物的β多样性分布与岛屿面积差及岛屿间距离并未呈现出显著相关,即其分布不受这两种因素限制;(4)NMDS分析结果显示岛屿面积、形状、边缘面积比和岛屿到大陆最小距离等特征对千岛湖岛屿上植物β多样性起决定性的作用。千岛湖陆桥岛屿组成的片段化生境中植物β多样性受扩散限制和生态位假说的共同影响。     

承德木本植物不同部位S及重金属含量特征的PCA分析

应用主分量分析(PCA)和排序技术(OA)对承德市10种木本植物的S及重金属含量进行了分析.结果表明,Z₁和Z₂主成份值基本代表了所有元素反应的信息,累积贡献率>98%.S对Z₁贡献最大(元素负荷量>0.96),Fe、Zn、Mn、Ph等对Z₂有较大的影响.表明承德市S污染是最主要的;重金属污染以Zn、Fe、Mn、Ph较显着,而Cu、Ni污染不明显.不同植物器官部位污染物含量的排序表明,城市木本植物的污染物以树皮为最高,其次是枝条,叶最低.     

应用间接排序识别盐沼植被的光谱特征:以崇明东滩为例

遥感技术已成为大尺度植被分类的重要手段,而地面植物群落特征与其光谱特征之间的关系是解译遥感影像的关键。该研究选择上海崇明东滩自然保护区的盐沼植物群落为对象,应用ASD地物光谱仪测定其植物群落的光谱反射率,并采用10个小型机载成像光谱仪(CASI)默认植被波段组,应用主分量分析法和相关分析分析了不同群落光谱特征与生态环境因子之间的关系。分析结果表明,间接排序法PCA能够识别盐沼植被中光滩、海三棱 草(Scirpus mariqueter)群落、芦苇(Phragmites australis)群落和互花米草(Spartina alterniflora)等群落的光谱特征,绝大多数盐沼湿地植物群落组成与光谱特征之间有显著的相关,识别效果最好的波段组是736~744 nm、746~753 nm、775~784 nm、815~824 nm和860~870 nm;对光谱反射率影响最大的生态环境因子分别是植物群落的高度和盖度,高程和其它环境因子的影响次之。研究成果可为遥感监测崇明东滩自然保护区内入侵种互花米草的空间分布和扩散规律提供技术支撑,为高光谱遥感影像的影像判读和解译分类以及盐沼湿地植被制图提供科学依据。     

青海湖北岸植物群落与环境因素关系的初步研究

依据对青海湖北岸１８个群落的术方调查和环境因子原始数据,用主分量分析排序技术和回归模型,定量分析湖滨原植物群落在空间地下上的分布格局,以及群落结构特征和环境梯度之间的关系。结果表明;植物群落的类型分布主要决定于环境中的土壤中水分 含量及土壤全分含量。     

Reconstructing community relationships: the impact of sampling error, ordination approach, and gradient length

Effectively summarizing complex community relationships is an important feature in studies such as biodiversity, global change, and invasion ecology. The reliability of such community summaries depends on the degree of sampling variability that is present in the data, the structure of the data, and the choice of ordination method, but the relative importance of these factors is not understood. We compared the validity of results from different ordination methods by applying five levels of sampling error to a simulated coenoplane model at two gradient lengths using two types of data (abundance and presence–absence). The multivariate methods we compared were correspondence analysis (CA), detrended correspondence analysis (DCA), non-metric multidimensional scaling (NMDS), principal component analysis (PCA) and principal coordinates analysis (PCoA). Our results showed CA and PCA using presence–absence data were the most successful methods regardless of sampling error and gradient length, closely followed by the other methods using presence–absence data. With abundance data, PCA and CA were the most successful approaches with the short and long gradients, respectively. Approaches based on PCoA and NMDS using abundance data did not perform well regardless of the choice of distance measure used in the analysis. Both of these methods, along with the PCA using abundance data, were strongly affected by the longer gradient, leading to more distorted results.     

Illumina Sequencing of 16S rRNA Tag Revealed Spatial Variations of Bacterial Communities in a Mangrove Wetland

The microbial community plays an essential role in the high productivity in mangrove wetlands. A proper understanding of the spatial variations of microbial communities will provide clues about the underline mechanisms that structure microbial groups and the isolation of bacterial strains of interest. In the present study, the diversity and composition of the bacterial community in sediments collected from four locations, namely mudflat, edge, bulk, and rhizosphere, within the Mai Po Ramsar Wetland in Hong Kong, SAR, China were compared using the barcoded Illumina paired-end sequencing technique. Rarefaction results showed that the bulk sediment inside the mature mangrove forest had the highest bacterial α-diversity, while the mudflat sediment without vegetation had the lowest. The comparison of β-diversity using principal component analysis and principal coordinate analysis with UniFrac metrics both showed that the spatial effects on bacterial communities were significant. All sediment samples could be clustered into two major groups, inner (bulk and rhizosphere sediments collected inside the mangrove forest) and outer mangrove sediments (the sediments collected at the mudflat and the edge of the mangrove forest). With the linear discriminate analysis scores larger than 3, four phyla, namely Actinobacteria, Acidobacteria, Nitrospirae, and Verrucomicrobia, were enriched in the nutrient-rich inner mangrove sediments, while abundances of Proteobacteria and Deferribacterias were higher in outer mangrove sediments. The rhizosphere effect of mangrove plants was also significant, which had a lower α-diversity, a higher amount of Nitrospirae, and a lower abundance of Proteobacteria than the bulk sediment nearby.     

Primary Study on Interrelation Between Plant Communities and Environmental Factors in the North Shore of Qinghai Lake

Eighteen plant communities were surveyed by quaduats in the north shore of Qinghai Lake. The communities were analyzed using PCA (principal component analysis) ordination and regression procedure to determine the distribution patterns of the plant communities and relationship between the communities and environmental factors. The results showed that the distribution of the plant communities were closely related to the moisture and salt content of soil. The correlation between species diversity or ecological dominance of the communities and gradient of environmental factors was not significant, but the two indexes of community showed multivarient line relationship with the first principal component, or the gradient of soil water, and the regression model as below: Y =- 4.85 4–1.47X1 4- 10.71X2 (P<0. 01).     

A comparison of fungal communities from four salt marsh plants using automated ribosomal intergenic spacer analysis (ARISA)

Fungal decomposers are important contributors to the detritus-based food webs of salt marsh ecosystems. Knowing the composition of salt marsh fungal communities is essential in understanding how detritus processing is affected by changes in community dynamics. Automated ribosomal intergenic spacer analysis (ARISA) was used to examine the composition of fungal communities associated with four temperate salt marsh plants, Spartina alterniflora (short and tall forms), Juncus roemerianus, Distichlis spicata and Sarcocornia perennis. Plant tissues were homogenized and subjected to a particle-filtration protocol that yielded 106 microm particulate fractions, which were used as a source of fungal isolates and fungal DNA. Genera identified from sporulating cultures demonstrated that the 106 microm particles from each host plant were reliable sources of fungal DNA for ARISA. Analysis of ARISA data by principal component analysis (PCA), principal coordinate analysis (PCO) and species diversity comparisons indicated that the fungal communities from the two grasses, S. alterniflora and D. spicata were more similar to each other than they were to the distinct communities associated with J. roemerianus and S. perennis. Principal component analysis also showed no consistent, seasonal pattern in the composition of these fungal communities. Comparisons of ARISA fingerprints from the different fungal communities and those from pure cultures of selected Spartina ascomycetes supported the host/substrate specificity observed for the fungal communities.     

大丰麋鹿保护区不同生境梯度下滩涂湿地植被的群落特征

以江苏大丰麋鹿国家级自然保护区第三核心区内的滩涂湿地植被为对象,采用样线法结合样方法进行野外调查,并采用等级聚类分析、主成分分析(PCA)和Shannon-Wiener物种多样性、Simpson生态优势度、Pielou群落均匀度等指数分析群落特征。结果表明,34个样地共有植物5科11属11种,划分为5种群落类型,群落优势种明显,伴生种较少,种类组成单调,均为草本植物;从近海至近岸滩涂湿地植被的分布呈现出较为明显的规律性变化:互花米草群落→碱蓬群落→大穗结缕草群落→芦苇群落→白茅群落,其物种多样性、生态优势度和群落均匀度均较低,物种丰富度呈现出由低到高再降低的趋势;PCA和植物生理特性分析结果暗示,土壤盐分梯度是影响植物群落分布的主要因素。     

An approach to incorporate linkage disequilibrium structure into genomic association analysis

In this study, we propose to use the principal component analysis (PCA) and regression model to incorporate linkage disequilibrium (LD) in genomic association data analysis. To accommodate LD in genomic data and reduce multiple testing, we suggest performing PCA and extracting the PCA score to capture the variation of genomic data, after which regression analysis is used to assess the association of the disease with the principal component score. An empirical analysis result shows that both genotype-basod correlation matrix and haplotype-based LD matrix can produce similar results for PCA. Principal component score seems to be more powerful in detecting genetic association because the principal component score is quantitatively measured and may be able to capture the effect of multiple loci.     

重金属污染对珠江口红树林表层沉积物碳含量的影响

湿地沉积物是红树林生态系统中重要的组成部分,其总有机碳储量的变化对红树林生态系统的固碳能力有着重要影响。现有对红树林湿地重金属的研究多集中于污染评价,鲜有涉及重金属含量对沉积物总有机碳（TOC）含量影响的研究。于2018-2019年期间4次前往珠江口典型红树林湿地,采集了0-30 cm表层土壤沉积物的样品,并测定其重金属含量和TOC含量,以探讨重金属含量变化对TOC的影响。结果表明,与广东地区的背景值相比,研究区沉积物重金属含量超标较为严重,重金属来源应是人类活动;沉积物的重金属含量能够显著影响TOC含量（P<0.01,R²=0.39）,间接对红树林湿地的固碳能力、甚至全球变暖产生一定影响;Cd、As、Zn含量高的沉积物环境有利于TOC的积累,Cu、Cr、Ni、Hg含量低的沉积物环境则不利于TOC的积累。沉积物的重金属对TOC的影响的机制是非常复杂的,它们可以通过影响土壤结构、土壤化学组分、土壤内微生物、上部植被群落的生长以及凋落物归还等一系列过程,导致沉积物TOC和固碳能力的变化。     

Using T-RFLP to Assess the Impact on Soil Microbial Communities by Transgenic Lines of Watermelon Rootstock Resistant to Cucumber Green Mottle Mosaic Virus (CGMMV)

To establish quantitative methods for ecological risk assessment, we assessed the impacts of transgenic watermelon rootstock (Citrullus lanatus (Twinser) cv. Gongdae) that was resistant to cucumber green mottle mosaic virus. The diversity of soil bacteria and fungi was monitored from May to July of 2005. Terminal restriction fragment length polymorphism (T-RFLP) was used with 16S ribosomal RNA (rRNA) coding genes for bacterial communities and with internal transcribed spacer (ITS) regions of rRNA coding genes for fungal communities. Multivariate analysis of variance (MANOVA) on the principal component analysis (PCA) scores of T-RF profiles detected no significant difference between microbial communities with transgenic or non-transgenic watermelon. Likewise, the results of our multi-response permutation procedure (MRPP) tests on non-metric multidimensional scaling (NMS) showed no significant difference between plant types. However, both MANOVA on PCA and MRPP on NMS revealed significant changes in the microbial community during the growing season. We used loading values of PCA to rank the abundances of bacterial species and found increases of some species in June and July.