A rapid survey method for the estimation of density and cover in desert plant communities

Abstract. The Log-series survey method allows rapid estimates of density and cover and is applicable for studies of perennial vegetation in arid environments. An optical rangefinder is used to determine boundaries of large circular plots. Numbers of individuals of each species within a plot are assessed; this information is used to assign species to logarithmic density classes equivalent to the logarithm base 2 of actual abundances. Each species is then assigned to a logarithmic canopy cover class, equivalent to the logarithmbase 2 of average cover per individual. Log total cover per species per plot is obtained by the addition of logarithmic density and cover classes. Percent cover per species is rapidly computed by taking the antilog of the difference between log total cover per species and log total plot area.     

Alien plant species composition and associations with anthropogenic disturbance in North American forests

A probability-based sampling scheme was used to survey plant species composition in forests of 16 states in seven geopolitical regions of the United States (California, Colorado, Minnesota, and parts of the Pacific Northwest, Southeast, Mid-Atlantic, and Northeast) in 1994. The proportion of alien species relative to the total species number and to canopy cover in the ground stratum (0–0.6 m height) was evaluated in 279 plots. Visually evident anthropogenic disturbances (e.g., artificial regeneration, logging, prescribed burning, and grazing by livestock), if any, were recorded on each plot. In each of the seven regions we quantified (1) the percentage of the number of species and total cover comprised of alien species, (2) the difference in these percentages for disturbed and undisturbed plots, and (3) the origin or native range for the alien species.The percentage of alien species ranged from approximately 4.5% (Colorado) to approximately 13.2% (California). The percentage of alien species cover ranged from approximately 1.5% in Colorado to 25% in California. In five regions, species introduced from temperate Eurasia comprised the largest proportion of alien species and cover. In the Southeast, species introduced from far eastern and subtropical Asia dominated the alien flora. In the Mid-Atlantic, the majority of alien species was Eurasian and the majority of alien species cover consisted of far eastern and subtropical Asian species.The proportion of plots in which at least one alien species was recorded was significantly higher in disturbed than undisturbed plots in the Southeast and marginally significantly higher ($p=0.053$) in the Northeast. These results are consistent with other published studies that indicate that anthropogenic disturbance affects the structure and composition of both the ground stratum and upper canopy of forest habitats. In other regions, however, no significant differences were found.     

流动沙丘区和固定沙丘区丘间低地植物种间关联关系

丘间低地植物种间关联研究对揭示植物对生境变化的响应及植被演替机制具有重要意义。通过χ2检验和AC关联系数对科尔沁沙地22个不同面积的流动沙丘区和固定沙丘区丘间低地植物种间关联进行了比较分析。结果表明:在固定沙丘区,当丘间低地面积<0.5hm2时,|AC|≤0.3的种对数占所有种对数的百分比和|AC|≥0.7的种对数占所有种对数的百分比略大于流动沙丘区,当丘间低地面积>0.5hm2时,|AC|≤0.3的种对数占所有种对数的百分比显著小于流动沙丘区,|AC|≥0.7的种对数占所有种对数的百分比显著大于流动沙丘区;当面积<0.5hm2时,沙丘固定未引起丘间低地植物种间关系发生明显变化;当面积>0.5hm2时,沙丘固定导致丘间低地植物种间关系更加紧密。     

西藏珠峰－卓奥友峰普士拉地区高山稀疏植被的群落特征及小地形的影响

在西藏定日县珠穆朗玛峰-卓奥友峰附近的普士拉地区的-山坡上(海拔5176—5390m),设置13个样方。进行群落调查、小地形测定和土壤剖面调查,分析该地区高寒植被的群落特征及其与小地形的关系。13个样方(面积25—200m^2不等)中,共记载物种80个(含变种和亚种),分别隶属于47个属。出现频度较高的种有高山嵩草(Kobresia pygmaea)、矮兔耳草(Lagottes humilis)、楔叶委陵菜(Potentilla funeata)、华马先蒿(Pedicularis oederi var.sinensis)、高山委陵菜(Potentilla polyjchista)、密生雪灵芝(Arenaria densissima)等;含物种数较多的属有：虎耳草属(Saxifraga)、风毛菊属(Saussurea)、嵩草属(Kobresia)、委陵菜属(Potentilla)、龙胆属(Gentiana)、葶苈属(Draba)等。随着海拔降低,物种和属的丰富度呈现出上升的趋势在该地区,植被盖度能较好地指示生境条件。等级聚类的结果也支持了这一观点：随着植被盖度的增加,转换物种丰富度(TSR)和转换属丰富度(TGR)增加,而物种多样性指数(Shannon-Wiener指数)减小。利用物种矩阵以及海拔、坡度、坡向、土壤深度、植被盖度等环境变量进行CCA排序,结果分出4类生境类型,它们较好地反映了群落特征与地形的关系。     

民间植物分类系统与区域性物种多样性快速评估--以西双版纳傣族为例

生物多样性的快速流失 ,使传统分类工作在热带物种多样性评估中显出不足 ,而民间分类系统在区域性物种多样性快速评估中的作用已经引起人们的重视。前人对西双版纳傣族民间植物命名和分类系统已做过研究 ,该文在此基础上 ,探讨能否将这种知识用于区域性物种多样性快速评估。利用生物多样性快速编目、样方调查及民族植物学中民间访谈的方法 ,考察了三个傣族村寨原住民的植物识别能力。结果表明 ,傣族原住民的植物识别程度与其年龄呈显著正相关 ,中年以后识别能力趋于稳定 ,识别率高达 91 %以上。通过与长期在西双版纳地区工作的野外植物分类学家相比较 ,我们发现傣族原住民的植物识别率不低于分类学家 ,且所需时间比分类学家少。作者认为 ,民间植物分类系统可以用于局部地区的物种多样性快速评估。     

宁乡猪实验动物化研究及在生物医学研究中的应用

宁乡猪为脂肪型猪种,具有遗传性稳定、食用价值高、生长快、适应性强及繁育力强等特征,已逐渐被应用于生物医学研究领域。本文对宁乡猪在封闭群培育、近交系培育、生物学特性及在生物医学研究领域中的应用等研究进展进行了综述。实验宁乡猪已封闭繁殖14年,可能是研究动脉粥样硬化、糖尿病有利模型。     

高寒草甸不同草地类型功能群多样性及组成对植物群落生产力的影响

对不同类型草地功能群多样性和组成与植物群落生产力之间的关系进行了探讨。结果表明：(1)在矮嵩草(Kobresia humlis)草甸和金露梅(Potentilla froticosa)灌丛中,豆科植物的作用比较明显,而其他功能群植物的作用较弱。(2)在藏嵩草(Kobresia tibetica)沼泽化草甸和小嵩草(K．pygmaca)草甸中,虽然杂类草、C3植物和莎草科植物功能群的生产力占群落初级生产力的比例较大,但二者在统计上没有显著性差异,这表明群落生产力除受物种多样性的影响外,也受物种本身特征和环境资源的影响,更主要的是受到功能群内物种密度和均匀度的影响,即功能群组成比功能群多样性更能说明对生态系统过程的影响。(3)不同类型草地群落植物功能群盖度与群落初级生产力呈显著的线性相关。(4)不同类型草地群落生产力与功能群内物种数的变化均表现为单峰曲线关系,即功能群内物种数处于中间水平时,群落生产力最高。     

北京城市生态系统植物种类构成及其分布特征

为了认识北京城市生态系统植物的构成特点、变化趋势及保护城市植物多样性 ,进而为北京城市绿化提供科学基础 ,对北京城区五环内各功能类型的植物进行了抽样调查、标本采集、鉴定和研究。结果表明 :(1)北京城区五环内共有维管束植物 99科30 7属 5 36种 ,其中北京本地种 2 79种 ,占总种数的 5 2 .0 5 % ,国内引进种 15 0种 ,占总种数的 2 7.99% ,国外引进种 10 7种 ,占总种数的 19.96 %。 (2 )北京城区植物属的区系地理成分以北温带成分为主 ,占城区总属数的 2 1.0 5 % ,远低于全北京植物北温带成分占 30 .30 %的比例 ;温带亚洲物种、旧世界温带物种、世界分布物种的比例都呈减少趋势 ;除旧世界热带物种成分外 ,其它热带物种成分的比例都有所增加。(3)城区各功能区物种丰富度从大到小的顺序为公园、学校校园、居民小区、道路、体育中心及单位场院、广场及公共建筑。公园、学校校园植物的总种数都占城区五环内植物总种数的 5 0 %以上 ,是城区植物的物种库。但本地植物物种比例在所有的功能区中均较低 ,甚至在公园与学校校园 ,本地物种的比例也分别只有 5 3.86 %与 5 2 .5 2 % ,居民小区和广场及公共建筑的北京本地种比例分别只有 4 1.39%和 4 0 .2 3%。 (4 )公园的乔、灌木植物多样性最高 ,荒地的草本植物     

Enhanced allelopathy and competitive ability of invasive plant Solidago canadensis in its introduced range

Aims Why invasive plants are more competitive in their introduced range than native range is still an unanswered question in plant invasion ecology. Here, we used the model invasive plant Solidago canadensis to test a hypothesis that enhanced production of allelopathic compounds results in greater competitive ability of invasive plants in the invaded range rather than in the native range. We also examined the degree to which the allelopathy contributes increased competitive ability of S. canadensis in the invaded range.Methods We compared allelochemical production by S. canadensis growing in its native area (the USA) and invaded area (China) and also by populations that were collected from the two countries and grown together in a 'common garden' greenhouse experiment. We also tested the allelopathic effects of S. canadensis collected from either the USA or China on the germination of Kummerowia striata (a native plant in China). Finally, we conducted a common garden, greenhouse experiment in which K. striata was grown in monoculture or with S. canadensis from the USA or China to test the effects of allelopathy on plant–plant competition with suitable controls such as adding activated carbon to the soil to absorb the allelochemicals and thereby eliminating any corresponding allopathic effects.Important findings Allelochemical contents (total phenolics, total flavones and total saponins) and allelopathic effects were greater in S. canadensis sampled from China than those from the USA as demonstrated in a field survey and a common garden experiment. Inhibition of K. striata germination using S. canadensis extracts or previously grown in soil was greater using samples from China than from the USA. The competitive ability of S. canadensis against K. striata was also greater for plants originating from China than those from the USA. Allelopathy could explain about 46% of the difference. These findings demonstrated that S. canadensis has evolved to be more allelopathic and competitive in the introduced range and that allelopathy significantly contributes to increased competitiveness for this invasive species.     

黄土丘陵区植物群落多样性及生物量随土壤水分梯度变化特征

了解土壤水分与物种多样性及生物量的关系对探究植物群落特征与分布具有重要意义.以陕北黄土丘陵区吴起、米脂、府谷、定边4个典型区域为研究对象,对比分析降水量影响下的土壤水分梯度对自然恢复植物群落多样性、生物量的影响,为黄土丘陵区植被恢复和生物多样性管理提供科学依据.结果表明:随降水量自东南向西北逐渐减少土壤水分呈降低趋势,...     

Biological control of plant pathogens in Brazil: application and current research

There are several examples of successful isolation, selection and development of antagonists of plant pathogens available for commercial use: mild strains of Tristeza virus of citrus for the control of Tristeza virus of citrus through preimmunization; Acremonium alternatum and A. persicinum for the control of tar spot of coconut (Catacauma torrendiella and Coccostroma palmicola); Trichoderma spp. for the control of Phytophthora cactorum on apple after soil treatment with formaldehyde and Dicyma pulvinata for the control of South American leaf blight (Microcyclus ulei) on rubber trees (Hevea brasiliensis) associated with polyclone plantations, are just a few. In an advanced stage of development there are for example: Bacillus subtilis for seed treatment and control of Sphaerotheca fuliginea on zucchini squash; Trichoderma spp. for soilborne pathogens; and Gliocladium roseum for the control of Botrytis cinerea in greenhouse cultivated strawberry.The author is with EMBRAPA/CNPMA, C.P. 69, 13820-000, Jaguariúna, SP-Brazil     

Relative importance of water, energy, and heterogeneity in determining regional pteridophyte and seed plant richness in China

Environmental variables, such as ambient energy, water availability, and environmental heterogeneity have been frequently proposed to account for species diversity gradients. How taxon-specific functional traits define large-scale richness gradients is a fundamental issue in understanding spatial patterns of species diversity, but has not been well documented. Using a large dataset on the regional flora from China, we examine the contrast spatial patterns and environmental determinants between pteridophytes and seed plants which differ in dispersal capacity and environmental requirements. Pteridophyte richness shows more pronounced spatial variation and stronger environmental associations than seed plant richness. Water availability generally accounts for more spatial variance in species richness of pteridophytes and seed plants than energy and heterogeneity do, especially for pteridophytes which have high dependence on moist and shady environments. Thus, pteridophyte richness is disproportionally affected by water-related variables; this in turn results in a higher proportion of pteridophytes in regional vascular plant floras (pteridophyte proportion) in wet regions. Most of the variance in seed plant richness, pteridophyte richness, and pteridophyte proportion explained by energy is included in variation that water and heterogeneity account for, indicating the redundancy of energy in the study extent. However, heterogeneity is more important for determining seed plant distributions. Pteridophyte and seed plant richness is strongly correlated, even after the environmental effects have been removed, implying functional linkages between them. Our study highlights the importance of incorporating biological traits of different taxonomic groups into the studies of macroecology and global change biology.     

Patterns of plant diversity in Africa south of the Sahara and their implications for conservation management

Plant species richness and range-size rarity in Africa south of the Sahara is concentrated in centres of plant diversity and endemism. Distribution patterns of plants mapped in the Distributiones Plantarum Africanum series and selected taxonomic monographs are analysed using the computer programme WORLDMAP. The plants are divided into four groups: herbaceous geophytes, mesophytic herbs, light-demanding shrubs and woody genera. Each group has peaks of species richness and range-size rarity at locations different to the other groups. Herbaceous geophytes and mesophytic herbs have their peaks of species richness and range-size rarity in the same location, the western Cape for geophytes and the Crystal Mountain for mesophytic herbs, whereas light-demanding shrubs and woody genera have peaks in different places. The results are discussed in relation to possible factors determining species richness and endemism and their likely conservation significance.     

Large-scale manipulation of plant litter and fertilizer in a managed successional temperate grassland

Plant litter may play an important role in herbaceous plant communities by limiting primary production and influencing plant species richness. However, it is not known how the effect of litter interacts with fertilization. We tested for the role of litter and fertilization in a large-scale experiment to investigate effects on diversity and biomass of plant species, growth forms, native vs. non-native groups, and abiotic ecosystem components (e.g., soil moisture, PAR). We manipulated plant litter (removed vs. left in situ) and nutrient availability (NPK-fertilized vs. unfertilized) for 4 years in 314-m² plots, replicated six times, in an old-field grassland. While many of our species-level results supported previously published studies and theory, our plant group results generally did not. Specifically, grass species richness and forb biomass was not affected by either fertilization or plant litter. Moreover, plant litter removal significantly increased non-native plant species richness. Relative to native plant species, all of our experimental manipulations significantly increased both the biomass and the species richness of non-native plant species. Thus, this grassland system was sensitive to management treatments through the facilitation of non-native plant species. We coupled biotic and abiotic components within a nonmetric multidimensional scaling (NMS) analysis to investigate treatment effects, which revealed that specific treatments altered ecosystem development. These results suggest that fertilization and plant litter may have larger impacts on plant communities and on ecosystem properties than previously understood, underscoring the need for larger-scale and longer-term experiments.     

恢复方式和地形对晋西黄土区退耕林分物种多样性的影响

运用样带样方调查法,对比不同恢复方式和地形条件下退耕林分的物种多样性,以期为晋西黄土区植被恢复效果评价和经营管理提供参考.结果表明: 恢复方式对退耕林分物种多样性具有显著影响.自然恢复林物种数为刺槐人工林的 1.6倍,Shannon 指数大于刺槐人工林,Pielou 指数小于刺槐人工林.物种多样性受坡位影响显著,各指数均表现为沟底>沟坡>梁峁坡>梁峁顶;坡向对退耕林分物种多样性影响不显著,各指数均表现为阴坡>阳坡.物种多样性受地形和恢复方式综合作用影响显著,在自然恢复林阴坡沟底处最高,物种均匀度在刺槐人工林阴坡沟底处最高.从提高物种多样性角度,黄土区植被恢复在遵循适地适树原则的同时,应参照自然恢复林分,在不同地形部位采用不同的造林设计.     

Chemical regulators of plant hormones and their applications in basic research and agriculture*

Plant hormones are small molecules that play versatile roles in regulating plant growth, development, and responses to the environment. Classic methodologies, including genetics, analytic chemistry, biochemistry, and molecular biology, have contributed to the progress in plant hormone studies. In addition, chemical regulators of plant hormone functions have been important in such studies. Today, synthetic chemicals, including plant growth regulators, are used to study and manipulate biological systems, collectively referred to as chemical biology. Here, we summarize the available chemical regulators and their contributions to plant hormone studies. We also pose questions that remain to be addressed in plant hormone studies and that might be solved with the help of chemical regulators.     

Patterns in the distribution of freshwater fishes in rivers of Central Western Ghats, India and their associations with environmental gradients

The community ecology of freshwater fishes in four river systems (Sharavati, Aghanashini, Bedti and Kali) of the central Western Ghats (India) has been studied for the first time. Patterns of fish species distributions were analysed and important stream and environmental parameters determining the species richness and composition of this region were identified. Upstream--downstream trends in species richness and diversity as well as changes in stream characteristics were studied using univariate correlation analyses. Preliminary analyses on changes in species composition and feeding guilds showed the presence of a gradual species turnover along the stream gradient. There were associated changes in the major feeding guild compositions, with a higher proportion of insectivore and algivore/herbivore composition in the upper reaches shifting to a predominance of omnivores and carnivores downstream. Pearsons product--moment correlation analyses along with stepwise multiple regression analyses identified stream depth and altitude as the important parameters determining species richness. Canonical correspondence analysis was performed to study species associations with environmental parameters. The analysis showed a strong species environmental correlation to the CCA axes, a high significance for the CCA axis 1 as well as for the overall test. The plots of the species and site scores on the CCA axes showed a clear segregation of species based on their relations with environmental and stream properties. This study is an important step in our understanding of the community structure of fish species of these rivers and would be helpful in future efforts on the conservation of aquatic communities and their habitats.