The effect of fluctuations in tidal inundation frequency on a salt-marsh vegetation

Over a period of 15 years recordings were made of the species cover in permanent plots on the salt marsh of one of the West Frisian Islands, Schiermonnikoog (The Netherlands). Correlations between annual changes in the cover of the major species, and fluctuations in the monthly frequency of inundation by seawater were studied. First, a spectral analysis was carried out on the inundation frequency data to look for predictable patterns. Subsequently, fluctuations were defined as deviations from these predictable patterns. In a repeated multiple regression model, the effects of the season in which the fluctuations occurred, and the elevational position of the plots on the salt marsh were studied as factors influencing the correlation patterns. The behaviour of various species is discussed in relation to their seed bank characteristics and their salt tolerance.     

中国热带森林植被类型研究历史和划分探讨

热带森林是我国森林植被的重要组成部分,明确其森林植被类型分类对于生物多样性维持机制研究和保护管理等都具有重要意义。该文以中国热带森林植被分类研究中存在的问题为出发点,通过阐述我国各省区植被类型分类的研究历史,在综合考虑多种生物和非生物影响因素的基础上,提出一个新的热带森林植被类型分类框架以供探讨。结果表明:(1)尽管针对我国热带森林的分布范围和群落特征等都已开展了诸多研究,但对我国热带森林植被类型的划分依据和分类体系仍存在争议。(2)尽管我国的热带森林都处于季风气候区带内,但许多热带地区的森林植被类型并不只是受季风影响,而是气候带、关键气候因子、地形、土壤反馈和物种适应等多种因素共同作用的结果。(3)我国的热带森林植被包括5个植被型,即非典型性热带雨林、热带季雨林、热带山地雨林、热带山顶苔藓矮林(热带云雾林)和热带针叶林,其中热带季雨林植被型包含4种植被亚型[热带落叶季雨林、热带半落叶(半常绿)季雨林、热带常绿季雨林和热带石灰岩(石山)季雨林]。(4)阐明了上述热带森林植被型和植被亚型在我国各省区的分布情况,并提出未来有必要对人工恢复后的热带森林进行评估和植被类型划分。综上所述,该文提出一个新的热带森林植被类型分类框架,以期为今后基于不同地区开展热带森林比较研究提供参考。     

大陆东南亚(中南半岛)的主要森林植被类型介绍

大陆东南亚(中南半岛)的植被研究情况鲜为人知,至今仍无系统研究资料。该文依据数次对该地区的野外考察和资料收集,介绍了东南亚植被的研究情况和文献资料以及对该地区主要森林植被的分类和各主要植被类型的特征。大陆东南亚地区在植被分类上包括七个主要的陆生及湿地的森林植被类型:针叶林、针阔混交林、热带山地常绿阔叶林、热带雨林、热带季节性湿润林、热带季风林(季雨林)、干旱刺灌丛/萨王纳植被。其中,针叶林植被型包括温性针叶林和热性针叶林二个植被亚型;针阔混交林包括温性针阔混交林和暖温性针阔混交林二个亚型;热带雨林植被型包括热带低地常绿雨林、热带季节性雨林(热带低地半常绿雨林)、热带山地雨林及泥炭沼泽森林四个植被亚型。该文还对大陆东南亚地区植被研究历史、植被分类系统、类型特征及植物区系组成进行了讨论。     

UAV-based classification of maritime Antarctic vegetation types using GEOBIA and random forest

Development of vegetation communities in areas of Antarctica without permanent ice cover emphasizes the need for effective remote sensing techniques for proper monitoring of local environmental changes. Detection and mapping of vegetation by image classification remains limited in the Antarctic environment due to the complexity of its surface cover, and the spatial heterogeneity and spectral homogeneity of cryptogamic vegetation. As ultra-high resolution aerial images allow a comprehensive analysis of vegetation, this study aims to identify different types of vegetation cover (i.e., algae, mosses, and lichens) in an ice-free area of  Hope Bay, on the northern tip of the Antarctic Peninsula. Using the geographic object-based image analysis (GEOBIA) approach, remote sensing data sets are tested in the random forest classifier in order to distinguish vegetation classes within vegetated areas. Because species of algae, mosses, and lichens may have similar spectral characteristics, subclasses are established. The results show that when only the mean values of green, red, and NIR bands are considered, the subclasses have low separability. Variations in accuracy and visual changes are identified according to the set of features used in the classification. Accuracy improves when multilayer information is used. A combination of spectral and morphometric products and by-products provides the best result for the detection and delineation of different types of vegetation, with an overall accuracy of 0.966 and a Kappa coefficient of 0.946. The method allowed for the identification of units primarily composed of algae, mosses, and lichens as well as differences in communities. This study demonstrates that ultra-high spatial resolution data can provide the necessary properties for the classification of vegetation in Maritime Antarctica, even in images obtained by sensors with low spectral resolution.     

基于区域植被类型评估的气候变化对中国森林生态系统的影响

基于中国知网(CNKI)和学术Google主题词为“气候变化”与“森林”的科技文献,根据全国范围的不同区域植被类型,运用整合分析方法就气候变化对森林生态系统的影响进行了系统评估,结果表明:在观测到的影响中,各个区域植被类型的树木物候、森林生产力与森林火灾方面的影响趋势大体相同,但森林地理分布影响趋势存在一定的差异;在预计的可能影响中,各个区域植被类型的树木物候、森林生产力、森林碳储量、森林火灾方面的影响趋势大体相同,但森林地理分布、森林结构方面的影响存在一定的差异.最后对现有研究的不足及未来研究方向等进行了讨论和展望.     

水淹频率变化对鄱阳湖增强型植被指数的影响

水淹状况是湿地植被动态的重要影响因素。该研究基于谷歌地球引擎(GEE)平台, 利用2000-03-01至2020-02-29所有覆盖研究区域的MODIS遥感影像数据, 分析20年间水淹频率(IF)、增强型植被指数(EVI)的时空变化以及湿地植被对IF变化的响应, 得出以下结论: (1) 20年来鄱阳湖水文节律发生了明显改变, 高IF (IF > 75%)水域面积呈现下降趋势, 从2000年1 435.3 km²下降至2019年的510.25 km², 降幅为64.45%; (2)区域平均EVI呈显著上升趋势, 植被扩张主要集中在中部IF下降区域; (3)分析不同总水淹频率区域中平均EVI年际变化, 发现EVI与水淹状况的变化趋势相似, 2009年之后鄱阳湖水域面积萎缩趋势缓解, EVI增长速度出现下降; (4)鄱阳湖湿地植被主要沿水域面积萎缩方向扩张, 基于像元统计20年间IF与EVI的变化趋势, 发现它们在空间分布上高度吻合, 这种空间异质性进一步证实水淹状况起到调节植被动态变化的作用。     

Diversity and physiological characterization of d-xylose-fermenting yeasts isolated from the brazilian amazonian forest

Background

This study is the first to investigate the Brazilian Amazonian Forest to identify new D-xylose-fermenting yeasts that might potentially be used in the production of ethanol from sugarcane bagasse hemicellulosic hydrolysates.

Methodology/Principal Findings

A total of 224 yeast strains were isolated from rotting wood samples collected in two Amazonian forest reserve sites. These samples were cultured in yeast nitrogen base (YNB)-D-xylose or YNB-xylan media. Candida tropicalis, Asterotremella humicola, Candida boidinii and Debaryomyces hansenii were the most frequently isolated yeasts. Among D-xylose-fermenting yeasts, six strains of Spathaspora passalidarum, two of Scheffersomyces stipitis, and representatives of five new species were identified. The new species included Candida amazonensis of the Scheffersomyces clade and Spathaspora sp. 1, Spathaspora sp. 2, Spathaspora sp. 3, and Candida sp. 1 of the Spathaspora clade. In fermentation assays using D-xylose (50 g/L) culture medium, S. passalidarum strains showed the highest ethanol yields (0.31 g/g to 0.37 g/g) and productivities (0.62 g/L·h to 0.75 g/L·h). Candida amazonensis exhibited a virtually complete D-xylose consumption and the highest xylitol yields (0.55 g/g to 0.59 g/g), with concentrations up to 25.2 g/L. The new Spathaspora species produced ethanol and/or xylitol in different concentrations as the main fermentation products. In sugarcane bagasse hemicellulosic fermentation assays, S. stipitis UFMG-XMD-15.2 generated the highest ethanol yield (0.34 g/g) and productivity (0.2 g/L·h), while the new species Spathaspora sp. 1 UFMG-XMD-16.2 and Spathaspora sp. 2 UFMG-XMD-23.2 were very good xylitol producers.

Conclusions/Significance

This study demonstrates the promise of using new D-xylose-fermenting yeast strains from the Brazilian Amazonian Forest for ethanol or xylitol production from sugarcane bagasse hemicellulosic hydrolysates.     

The influence of vegetation,salinity, and inundation on seed banks of oligohaline coastal marshes

Sea level rise may alter salinity and inundation regimes and create patches of open water in oligohaline coastal marshes, potentially affecting the composition and germination of seed bank species. We conducted seedling emergence experiments to: (1) examine the effects of standing vegetation on the seed banks of three oligohaline marsh communities in coastal Louisiana (dominated by Paspalum vaginatum Sw., Sagittaria lancifolia L., or Spartina patens (Ait.) Muhl., respectively); and (2) investigate the effects of salinity and inundation regime on germination of seed bank species. We also studied the effect of a temporary increase in salinity (to simulate a salt water intrusion event) on the viability of buried seeds. We found that the presence or absence of vegetation within a community affected the abundance of some species in the seed bank but had little effect on species composition. Also, the seed banks of the three communities exhibited considerable overlap in species composition and had similar species richness (10–11) and diversity (antilog Shannon-Weaver diversity index = 6.5–7.1), despite differences in vegetation type. Higher salinities and flooding reduced seedling emergence for most species; few species emerged at salinities above four parts per thousand (ppt), and only Sagittaria lancifolia and Eleocharis parvula germinated well under flooded conditions. A temporary increase in salinity did not affect species richness or seedling emergence of most species. Our results suggest that differences in vegetation may have little effect on the composition of seed banks of oligohaline marshes. However, higher salinities and greater depth and duration of inundation (anticipated as global sea level continues to rise) may decrease recruitment of seed bank species, reducing their abundance in oligohaline marsh communities.     

Notes on British Boleti: III.

Summary

A key to the British species of the genera Aureoboletus, Boletinus, Gyroporus, Phylloporus, Porphyrellus, Pulveroboletus, Strobilomyces and Uloporus based on habitat, microscopic and macroscopic features is discussed. Four species as yet unrecorded from the British Isles, Boletinus asiaticus, Xerocomus amarellus, Boletus vaccinus, Boletus badiorufus and seven species which could possibly be sought in one of these genera are included in the discussion for completeness; the latter are also included in the key.     

The complexity of forest borders determines the understorey vegetation

Questions

What are the most important drivers of plant species richness (gamma‐diversity) and species turnover (beta‐diversity) in the field layer of a forest edge? Does the tree and shrub species richness structure and complexity affect the richness of forest and grassland specialist species?

Location

Southeast Sweden.

Methods

We sampled 50 forest edges with different levels of structural complexity in agricultural landscapes. In each border we recorded trees, shrubs and herb layer species in a 50‐m transect parallel with the forest. We investigated species composition and species turnover in relation to the proportions of gaps in the border and the diversity of trees and shrubs.

Results

Total plant species richness in the field layer was mainly explained by the proportion of gaps to areas with full canopy cover and tree diversity. Increasing number of gaps promoted higher diversity of grassland specialist species within the field layer, resulting in open forest borders with the highest overall species richness. Gaps did however have a negative impact on forest species richness. Conversely, increasing forest species richness was positively related to tree diversity, but the number of grassland specialist species was negatively affected by tree diversity.

Conclusions

Managing forest borders, and therefore increasing the area of semi‐open habitats in fragmented agricultural landscapes, provides future opportunities to create a network of suitable habitats for both grassland and deciduous forest specialist species. Such measures therefore have the potential to increase functional connectivity and support dispersal of species in homogeneous forest/agricultural landscapes.     

Phytostructural characterization of several vegetation types in northern Portugal. II. The structural expressivity and the resistance of the vegetation

Abstract

The encouraging results obtained in a previous work induced the authors to pursue here the characterization of the structure of the vegetation in northern Portugal, using the phytostructural methodology proposed earlier by the authors. With this objective, eight different types of vegetal communities, representative of the apparent states of the successional process present in this area, and representing the diversity of plant community types in the same area, were selected. The phytostructural method was elaborated on the basis of three types of structural basic matrices regarding diversity, abundance and cover. The data obtained were collected in a contingency matrix, which was then treated by means of a statistical multivariate analysis. Three structural tendencies emerged from this analysis. With the aim of studying their stability, the results are discussed in terms of resistance and resilience, according to the Highest Expressive Amplitude (HEA) concept, and by considering the intra- and inter-community structural dynamics as structural parameters. The data obtained suggest structural situations with different degrees of non-equilibrium that reflect resistance to environmental factors. The resistance of the vegetation is correlated with the apparent functional connectivity detected for the communities analysed.     

青藏高原各主要植被类型特征及环境差异

青藏高原高海拔引起的地形、气候和土壤空间差异造就了其独特的植被类型及其空间变化,当前研究缺乏针对青藏高原全域范围内各植被类型特征和环境差异的定量与系统性分析。针对青藏高原特殊的地理环境和植被类型,选用植被、地形、土壤、气候4个维度共计58个空间化指标,采用频数分布统计方法对这些指标开展了定量分析,系统揭示了青藏高原全域范围内各主要植被类型的特征及环境差异。通过定量分析发现,大部分的环境及植被特征指标对青藏高原各主要植被类型的区分度较高,其中,遥感归一化植被指数、植被净初级生产力、裸地覆盖度、海拔、土壤温度、年最低温度、年总蒸散发7个指标对青藏高原各主要植被类型的区分度较高。揭示的青藏高原各主要植被类型的特征及环境差异,可提高灌丛和草地之间、各草地类型之间、高山苔原-垫状-稀疏植被与其他植被类型之间的可区分性,有助于解决青藏高原植被精细分类中广泛存在的灌丛和草地区分、草地类型细分、高山苔原-垫状-稀疏植被识别和山地垂直地带植被识别四个难点问题。研究结果一方面可服务于青藏高原的植被精细分类,另一方面也可服务于青藏高原的自然地带划分、生物多样性和生态系统功能评估、地表物质循环研究等。     

不同火灾强度下森林植被的自然恢复

按照与火灾发生区的方位将森林划分为火灾核心区、火灾边缘区、地下火发生以及对照(未发生火灾)等四类;同时,按照树种将其划分为兴安落叶松纯林、白桦纯林及兴安落叶松、白桦混交林等三类,对阿尔山地区1998年"5.13"雷击火发生迹地林下植被的自然恢复状况进行了调查.结果表明:提出的分级标准能够反映林分遭受不同强度火灾后植被恢复状况的差异.火灾核心区受害程度最重,在物种丰富度、物种多样性、灌草地上生物量等方面均居于最低水平;地下火发生区林受害部分多在地下,各项指标位居次要地位;火灾边缘区林分虽受到一定的危害,但各项指标在所有受害林分中居最高水平.不同程度受害区域内的乔灌木年轮数呈现随危害程度增加而减少的趋势.混交林的恢复力强于纯林,兴安落叶松也显示了比白桦更强的恢复力.通过林下阳性植物与阴性植物代表种相对盖度的比值变化,对林下植被的灾后演替进行了研究,结果表明,火灾核心区林位于林窗阶段,地下火发生林处于建立阶段,而火灾边缘区林与对照均处于成熟阶段.对火灾后的人工改善措施进行探讨.文章提出从年轮的宽度与分布规律、林分初级生产力与灌草地上生物量的关系及林分节肢动物群落等方面做深入分析.     

子午岭次生植被下土壤蓄水性能及有效性研究

通过土壤水分特征曲线的测定,研究了子午岭北部黄土丘陵区不同次生植被群落类型下土壤蓄水性能及水分有效含量的变化。结果表明：撂荒地的土壤蓄水量最小,草地和灌木地的土壤蓄水量有所提高,增幅为17％～65％,而乔木林地土壤蓄水量最大,分别较撂荒地和草地、灌木地增加明显,其增加幅度分别达68％～79％、41％～50％和15％～20％;土壤田间持水量在0～20cm土层从撂荒地、草地、灌木林地到乔木林地,土壤田问持水量逐步提高,而20～50cm土层则变化不大;土壤有效水含量在两个土层中的变化均随着植被的进展演替呈现增加的趋势。讨论了植被与土壤互动关系中应进一步研究的问题。