Floristic characteristics of the wetland sites on dry southern slopes of the Alborz Mts., N. Iran: The role of altitude in floristic composition

The Alborz Mountains, the second largest range in Iran, is, on its southern slopes, mainly covered by steppe vegetation. These dry slopes also include ‘green islands’ of wetland. Floristic diversity and environmental characteristics of 45 of these little-studied wetland sites have been assessed along an altitudinal gradient using one-way ANOVA, Pearson r and detrended correspondence analysis/canonical correspondence analysis (DCA/CCA) analyses. The wetlands proved to be of conservation importance with 310 plant taxa, including 35 endemics or subendemics. Predictably, and consistent with the phytosociological classification of Klein [2001. La végétation altitudinale de L’Alborz Central (Iran): Entre les régions Irano-Touranienne et Euro-sibérienne. Institut Français de Recherche en Iran, Téhéran], there were parallel changes in vegetation both within wetlands and the surrounding steppes and in DCA/CCA analyses altitude appeared to be the primary determinant of floristic composition. Upper mountain wetlands are particularly species-rich and contain many endemics and other species of a narrow phytogeographical distribution. Soil pH declined with altitude, perhaps in part as a consequence of low salinity (and high pH) in the mountains. Consistent with the work of Raunkiaer [1934. The life forms of plants and statistical plant geography. Clarendon Press, Oxford], hemicryptophytes are mainly restricted to upper mountain areas. Though correlated both directly with altitude and with correlation in DCA/CCA plots, phytogeography, life-form and soil pH fail to adequately explain the ecological processes that maintain the altitudinal gradient in vegetation types and species composition. Further studies on site productivity, soil chemistry and climate-related variables are, therefore, on-going in an attempt to understand more fully the ecosystem processes maintaining the diversity of these important wetland sites.     

Species Diversity and Life-Form Patterns in Steppe Vegetation along a 3000 m Altitudinal Gradient in the Alborz Mountains, Iran

Biodiversity pattern and life-form spectra were studied along a 3,000 m altitudinal gradient from a semi-desert area to the alpine peak of Tochal Mountain. The gradient is located on the southern slopes of Central Alborz with a Mediterranean continental climate. DCA ordination was applied to 1,069 relevés and 7 quantitative variables to discover the relation of diversity and altitude. A biodiversity pattern was obtained by relating values for species richness and Shannon-Wiener’s index to 100-m altitudinal sections. Altitude was determined as the major ecological gradient. Both diversity indices are negatively correlated with altitude and show a decreasing trend beyond a peak in species richness at 1,800–1,900 m a.s.l. towards a very low diversity in the high alpine zone. The biodiversity peak does not match with the potential tree line in the area (2,500–3,000 m a.s.l.). The high diversity in foothills can be related to habitat heterogeneity, longer suitable climatic conditions, and diverse disturbance factors, while unfavorable conditions at high-altitude alpine and low-altitude desert areas reduce the number of species at both extremes. Life-form patterns clearly change along altitudinal gradient. Annuals with decreasing trend, and hemicryptophytes and chamaephytes with increasing trend along the altitudinal gradient are notable patterns of life form in the area. Temperature, soil moisture and nutrients are the main factors that explain the ecological influence of altitude on species diversity and life-form patterns in the semi-arid steppe vegetation of the area.     

Altitudinal zonation of evergreen broad-leaved forest on Mount Lopei,Taiwan

Abstract. Evergreen broad-leaved forest was studied in a transect on the northwestern slope of Mount Lopei in order to reveal altitudinal zonation in structure and floristic composition and the decisive environmental factors. 20 plots of 20 m × 20 m at altitudes from 540 m to 1320 m were analysed. 144 woody species were found. The results of a DCA ordination clearly pointed to a single dominant altitudinal gradient. Nevertheless, wind-exposure associated topography was found to account for additional variation for a given altitudinal range. Along the altitudinal gradient, four dominance-based forest types were recognized. Tree density, species diversity and evenness of the four types differed significantly but total basal area and tree volume were not significantly different. The 95 % turnover range for woody species as measured by the Community Coefficient was calculated as 1030 m, and the 50 % turnover range as 238 m. For the understorey, the change in species composition with altitude was less obvious. Species population structures of 57 sufficiently abundant species revealed four characteristic patterns, but most species showed a good fit to the negatively exponential or power function distribution and thus appeared to have good reproduction and regular recruitment. Both ANOVA and Redundancy Analysis (RDA) showed that significant differences among forest types were found for most soil variables. Organic C, exchangeable Na and K tended to increase with altitude, while pH and available N showed a reverse trend. There was little evidence that the differences in soil pH and available N were responsible for the variation in forest growth.     

新疆博格达山地面生苔藓植被的数量分类与排序研究

 应用数量分类(TWINSPAN)和排序(DCA)方法,对新疆博格达山苔藓植被进行了多元分析。TWINSPAN结果表明,该地区苔藓植被可分为6个主要群落类型,即牛角藓-真藓(Cratoneuron-Bryum)群落、扭口藓-墙藓(Barbula-Tortula)群落、提灯藓-细罗藓(Mnium-Leskeella)群落、对叶藓-提灯藓(Distichium_Mnium)群落、墙藓-连轴藓(Tortula_Schistidium)群落、扭口藓-紫萼藓(Barbula_Grimmia)群落,它们分别分布于山地荒     

山西北部地区沙棘群落的数量分类和排序研究

采用双向指示种分析法对山西北部地区沙棘群落进行分类和排序研究,结果将山西北部地区沙棘群落划分为14个群系,并论述了各群系的特征。DCA排序进一步说明了群系的分布格局与水分和土壤的密切关系,结果表明组成沙棘灌丛的种群对群落生境具有指示作用,能客观反映群落的生境特征．     

Factors Controlling Compositional Changes in a Northern Andean Páramo (La Rusia,Colombia)

In this study, we aimed to assess the processes controlling compositional change in a Northern Andean páramo highly affected by human‐induced disturbances over the last few decades (La Rusia, Colombia). Along the 3000–3800 m asl altitudinal range, we randomly sampled fifty 10 × 10 m plots. Therein, we measured altitude and variables related to soil conditions (i.e., moisture, nutrient contents, bulk density, and texture), occurrence of human‐induced disturbances (i.e., fire, vegetation clearing, potato cultivation, and cattle grazing), and land‐use history. We also recorded richness and abundance of plant species, identifying them as exotic or native. We differentiated four groups of plots according to their species composition. The groups had significant differences in altitude, soil conditions, land‐use history, and particularly, in richness of exotic species and exotic/native cover ratio. They could be ascribed to shrub‐ and grass‐páramo vegetation types based on their relative dominance of woody and herbaceous species; however, these groups were not arranged according to the hypothetical composition of altitudinal belts, but rather formed a mosaic of patches. This mosaic was determined not only by altitude but also by soil conditions and disturbance history of sites. Our results corroborate recent findings which highlight shrub‐ and grass‐páramo vegetation types as patches of contrasting species composition and structure that depend on local environmental variables, as well as human‐induced disturbances as a major determinant of compositional discontinuities in these ‘high mountain’ tropical ecosystems.     

Variations of the germinable soil seed bank along the altitudinal gradient in the northwestern Red Sea region

The variations in the size, composition and diversity of the germinable soil seed bank were studied along an altitudinal gradient in the northwestern Red Sea region. The standing vegetation and the germinable seed bank were studied in 58 stands distributed along the altitudinal range from sea level to coastal mountain peaks. The classification of the germinable seed bank by the two-way indicator species analysis (TWINSPAN) led to the recognition of five groups representing different altitudinal ranges. Detrended correspondence analysis (DCA) shows that these groups are clearly distinguished by the first two DCA axes. The results demonstrate significant associations between the floristic composition of the seed bank and the edaphic factors such as CaCO₃, electrical conductivity, organic carbon and soil texture. Species richness, Shannon index of diversity and the size of the germinable seed bank show a hump-shaped curve along the altitudinal gradient, whereas evenness shows a weak increase with elevation increasing. Beta diversity of the seed bank declines with altitude increasing. The similarity between the standing vegetation and the seed bank approaches a U-shaped pattern along the elevation gradient. About 34.8% of the species that constitute the standing vegetation are vulnerable to elimination from the standing vegetation because they are not represented in the seed bank. Soil seed bank can be used for restoration of the vegetation at some of the degraded sites.     

滹沱河流域湿地植被的数量分类和排序

应用TWINSPAN和DCA相结合的方法,对滹沱河流域湿地植被74个样方进行分类和排序,将湿地植被分为16个群丛。DCA排序第一轴反映土壤含水量梯度,第二轴反映土壤类型的变化。主要优势种的DCA排序图与样方的DCA排序图有很大的相似性,优势种的分布格局在很大程度上决定着植物群丛的分布格局。     

中条山东段森林乔木树种分布的环境梯度分析与种组划分

利用CCA排序和TWINSPAN分类,探讨了中条山东段森林植被中乔木树种分布与环境梯度的关系,并根据树种在排序图上的相对位置,同时参考相关文献资料,进行了种组划分。结果表明,海拔梯度是影响乔木树种分布的最重要的环境因子,土壤肥力和土壤湿度指数也具有较大的作用。72个树种（含变种）归纳划分为6个种组,即低海拔暖湿型、中低海拔暖燥型、中低海拔温润型、中海拔湿沃型、中高海拔燥瘠型和高海拔冷湿型。每个种组内的树种在生态习性特别是在分布特征上显示出较大的相似性,介绍了各种组分布的生境特征。TWINSPAN分类结果与种组划分吻合较好。     

博斯腾湖湖滨湿地植被数量分类与排序

应用双向指示种分析(TWINSPAN)方法对湿地植物群落进行分类,采用除趋势对应分析(DCA)、典范对应分析(CCA)对群落进行排序,以明确博斯腾湖湖滨湿地的主要植物群落类型及影响植被类型变化和分布的主要环境因子。结果表明,博斯腾湖湖滨湿地植被可分为7个主要群丛,分别为长苞香蒲(Ass.Typha angustata)、芦苇+长苞香蒲(Ass.Phragmites australis+Ty.angustata)、芦苇+水烛(Ass.P.australis+Ty.Angustifolia)、多枝柽柳-芦苇(Ass.Tamarix ramosissima-P.australis)、胡杨-多枝柽柳(Ass.Populus euphratica-Ta.ramosissima)、旱柳-多枝柽柳(Ass.Salix matsudana-Ta.ramosissima)和多枝柽柳(Ass.Ta.ramosissima),它们分布于湖滨浅水带、湖滨沼泽带、湖岸乔灌林带和旱生灌丛带;TWINSPAN分类产生的7个主要群丛在DCA排序图上被很好地反映出来。CCA排序与DCA排序结果基本一致,说明土壤含水量和土壤总含盐量是决定该地区植被分布格局的主要环境因子。博斯腾湖湖滨湿地植被种类单一,生态结构简单,水盐动态及其相互作用是影响该地区植被分布的主要因素之一。因此,在对博斯腾湖湖滨湿地进行植被保护与重建过程中,需重点考虑土壤含水量和土壤总含盐量这2个主要环境因子的影响,合理开发、利用水资源,防止土壤盐渍化的发生。     

Searching for Altitudinal Zonation: Species Distribution and Vegetation Composition in the Superpáramo of Volcán Iliniza, Ecuador

Altitudinal variation of the zonal superpáramo vegetation was studied between 4300 and 4630 m to test a possible occurrence of a fine altitudinal zonation within the superpáramo belt. A rectangular grid of 1 m² sample plots was established; 25 replicate plots separated by a 3 m space were located along a 100 m long transect parallel to the contours, and there were 17 such transects separated by 20 m of altitude. Species were scored using a 7-grade cover scale and basic environmental data were gathered for each sample. Major changes occur over a short altitudinal range, at around 4400 m, which corresponds to a transition between the lower and upper superpáramo. Species richness sharply declines but species turnover (per altitude) increases along the altitudinal gradient. The correlation between richness and bare ground or rock cover is negative, but the correlation to rocks becomes positive above 4500 m. Species from lower altitudes tend to have narrower altitudinal range, although a large number of species appear to be indifferent to altitude. Direct ordination analyses indicate that high-altitude species show stronger correlation to environmental variables, especially rock, than species from lower altitudes. TWINSPAN cluster analysis delimited 15 groups of samples. There is a change in the clustering pattern along the altitudinal gradient from a horizontal (i.e., within altitude) to vertical (i.e., across altitude) arrangement of the cluster groups, although this pattern is partly obscured at the highest altitudes due to a large number of empty samples. MANOVA tests for samples from adjacent altitudinal levels indicate two distinct altitudinal breaks at lower altitudes, corresponding to the Loricaria-belt in lower superpáramo and the transition between lower and upper superpáramo, while no indication of a zonation was found in upper superpáramo.     

Multivariate statistical analysis of the Pteridophytic diversity of District Battagram,Khyber Pakhtunkhwa,Pakistan

The Pteridophytes represent a great but poorly explored potential as an ecological indicators. Ecological indicator is a useful tool to link empirical results, models and theories with environmental applications. Habitat diversity, precipitation, moisture and rainfall have a high influence on species richness with altitudinal gradients. From 15 different habitats 45 species belonged to 25 genera and 13 families were documented. The leading family were Pteridaceae with 14 taxa, Dryopteridaceae were the second largest family with 7 taxa, followed by Thylepteridaceae with 6 taxa and Aspleniaceae with 5 taxa. Adiantum capillus-veneris and Diplazium esculentum survive in a wide range of habitats while Pellaea calomelanos have a narrow range of habitat. Five plant associations were sorted out through cluster analysis and two ways indicator species analysis. In Bray Curtis ordination the maximum Regression coefficient were recorded for axis 1 (?10.66) with a variance of 0.61. The response data were compositional and have a gradient of 3.2 SD units long. In DCA ordination maximum Eigenvalue and gradient length were recorded for axis 1. Species grouped on the basis of habitat types and habitats having common species. CCA ordination showed that the plants have a linear relationship with environmental variables. The permutation test results on all axis were pseudo-F = 2.4, P = 0.002 indicating the significance value. CCA ordination showed that the environmental variables had a great impact on the association and distribution of majority of the species.     

历山自然保护区猪尾沟森林群落植被格局及环境解释

应用TWINSPAN、DCA和DCCA,从植物种,植物群落与环境的生态关系方面,研究历山自然保护区猪尾沟森林群落的植被分布格局,并给予合理的环境解释。结果如下：（1）采用TWINSPAN数量分类方法,将植被划分为9个群落类型。（2）对于特定的研究区域猪尾沟,制约森林群落类型,植物种分布格局的主要因素是海拔梯度,即水、热两个环境因子。（3）DCCA排序图明显反映出排序轴的生态意义,第一轴基本上突出反映了各植物群落所在环境的海拔梯度,即热量因素,沿第一轴从左到右,海拔逐渐升高,植物群落或植物种对热量要求降低;第二轴主要表现了各植物群落或植物种所在环境的坡度,坡向,即水分和光照因素,沿第二轴从下到上,坡度渐缓,坡向渐向阳。     

Detection of Climate-Sensitive Zones and Identification of Climate Change Indicators: A Case Study from the Bavarian Forest National Park

We determined the climate-sensitive zones along an altitudinal gradient in a low mountain range forest, the Bavarian Forest National Park in south-eastern Germany, and studied which vascular plant species are likely to respond to climate change. Plants were recorded on 273 plots along four straight transects. The composition of the plant species and their environmental correlates were detected using unconstrained correspondence analysis (DCA) with post-hoc correlation of axes against site variables. We tested the effect of site variables on species composition using maximally selected rank statistics, which allow the simultaneous identification of a threshold and assessment of its significance. Species turnover within the vascular plant community along the altitudinal gradient was assessed using the same method on the basis of the DCA sample scores. Using geostatistical models of local temperature and Bayesian methods with binomial errors that account for spatial structure, we tested the influence of temperature on selected single vascular plant species and assessed the suitability of the species as climate change indicators. Temperature was the most important factor explaining the variability in vascular plant community composition, which changed discretely along the altitudinal gradient, with a climate-sensitive zone found between 1,100 and 1,200 m a.s.l. The distribution of ten species with their lower or upper altitudinal limit in this zone was significantly driven by temperature. To track vegetation responses to climate change effectively, we suggest a three-level monitoring program, flexible with regard to the volume of required sampling effort.     

Environmental factors and vegetation composition, Lefka Ori massif, Crete, S. Aegean

Aim The aim of this study was to explore the environmental factors that determine the spatial distribution of oro‐mediterranean and alti‐mediterranean plant communities in Crete. Location The paper provides a quantitative analysis of vegetation–environment relationships for two study areas within the Lefka Ori massif Crete, a proposed Natura 2000 site. Methods Eleven environmental variables were recorded: altitude, slope, aspect, percentage of bare rock, percentage of unvegetated ground, soil depth, pH, organic matter content and percentages of sand, silt and clay content. Classification of the vegetation was based on twinspan , while detrended correspondence analysis (DCA) and canonical correspondence analysis (CCA) were used to identify environmental gradients linked to community distribution. Results One hundred and twenty‐five species were recorded from 120 plots located within the two study areas. Forty‐seven of the recorded species are endemic, belonging to 35 families. Hemicryptophytes and chamaephytes were the most frequent, suggesting a typical oro‐mediterranean life form spectrum. The samples were classified into five main community types and one transitional. The main gradients, identified by CCA, were altitude and surface cover type in the North‐west site, while in the Central site the gradients were soil formation‐development and surface cover type. Main conclusions The use of classification in combination with ordination techniques resulted in a good discrimination between plant communities and a greater understanding of controlling environmental factors. The methodology adopted can be employed for improving baseline information on plant community ecology and distribution in Mediterranean mountain zones.     

卧龙自然保护区亚高山草甸的数量分类与排序

在野外植被调查的基础上,采用植被数量分析方法对岷江流域卧龙自然保护区亚高山草甸进行TWINSPAN分类和DCA排序,研究了植物种、植物群落与环境之间的关系.结果表明,该地区亚高山草甸共有植物139种,隶属于31科88属.应用数量分类方法将114个样方分为12个群落类型.在分析不同环境因子间的关系基础上,从定量的角度揭示了影响群落分布的主要因素是海拔梯度和土壤含水量.DCA排序图反映出排序轴的生态意义,第1轴反映了各群落类型所在环境的海拔梯度,从上到下,随着海拔的升高,植物群落或植物种的耐寒性越来越强;第2轴基本上反映了各群落类型所在环境的土壤含水量.排序结果与分类结果比较吻合,反映出植物群落类型和物种分布随环境因子梯度变化的趋势.     

Distribution of plant life forms along an altitudinal gradient in the semi‐arid valley of Zapotitlán,Mexico

Abstract. Plant life‐form abundance along a 600 m altitudinal gradient (1600–2200 m a.s.l.) in the semi‐arid valley of Zapotitlán, México was correlated with soil characteristics and climatic variables. One mixed soil sample was taken and analysed for each of six elevations, temperature was estimated using a terrestrial thermal gradient, and precipitation using a linear regression between total annual precipitation and the elevation of the weather stations in the valley. Rosettes, microphanerophytes, therophytes and nanophanerophytes were well represented throughout the gradient. Columnar cacti were restricted to the 1600–1800 m range, and geophytes to the 1700–1800 m range. In general, abundance of life forms was inversely associated with altitude. Multiple regression analysis did not show parameters to significantly explain the abundance of rosettes, nanophanerophytes, epiphytes, geophytes and hemiparasites; altitude and nitrogen proved significant for columnar cacti, succulents and chamaephytes; altitude, pH, electrical conductivity and nitrogen were significant for globose cacti; pH was significant for therophytes; and altitude was significant for microphanerophytes.     

Quantitative classification and ordination of forest communities in Pangquangou National Nature Reserve

Quantitative analysis of ecological relationships between vegetation and the environment has become an essential means in the field of research of modern vegetation ecology. In this article, based on data from 84 quadrates, forest communities in this reserve were investigated using TWINSPAN, DCA and DCCA. The results will be helpful in the construction and development of Pangquangou National Nature Reserve. Using TWINSPAN, the forest communities were classified into seven types. The distribution pattern of vegetation reflects the comprehensive influence of environments. The results of DCA and DCCA clearly reflect the relationship between the pattern of forest communities and environmental gradients. The ordination result of DCCA indicates that altitude is more important than other environmental factors because the change of altitude gradient will lead to changes in the temperature and humidity gradients. The first of the DCA ordination axes indicates the humidity gradient, and the second indicates the temperature gradient. All these results show that the main factors restricting the distribution of communities in this reserve are temperature and humidity. The ecological meaning of the ordination axis in DCCA is much clearer than that in DCA, and the species-environment correlation of DCCA is more obvious than DCA. The first DCCA axis indicates the altitude gradient among the communities, while the second is the gradient in aspect and slope among the communities. DCCA ordination can simultaneously express similarities of species and environment. Therefore, the quadrat location in the DCCA ordination figure is much closer than in the DCA.     

Food selection by the guanaco (Lama guanicoe) along an altitudinal gradient in the Southern Andean Precordillera (Argentina)

Wild ungulates like the guanaco are exposed to important changes in climate and plant diversity along altitudinal gradients in the Andes Mountains, such as in the Southern Andean Precordillera where three phytogeographic provinces are present in altitudinal belts. The guanaco’s diet and food availability were seasonally analyzed using microhistological analysis and point-quadrat transects at six sampling sites, representative of the phytogeographic belts along the altitudinal gradient. Plant cover and diversity decreased with growing altitude. Richness of plant species was poorer at the summit than in the lower altitudes, whereas the proportion of species eaten by guanacos increased with altitude. The diet included 77 species. Grasses were preferred and shrubs were avoided all year round. The grass Poa spp. occupied more than 50 % of the diet at all altitudes. Grasses were the main dietary item even at low altitudes, where shrubs constituted the main food available. Decreasing generalism with descending phytogeographic belts agrees with the prediction for altitudinal gradients. The increase of diversity in the diet during the winter decline of plant cover at high and middle altitudes follows that expected from the optimal foraging theory. The winter decline of vegetation and the dietary shift from grazing to browsing proved to be stronger as altitude increases and the climate become more rigorous. Plant species richness, food scarcity, and climate severity are relevant variables to explain altitudinal and seasonal changes in the diet of adaptive ungulates in mountain environments, such as the guanaco in the Southern Andean Precordillera.     

Quantitative classification and ordination of forest communities in Pangquangou National Nature Reserve

Quantitative analysis of ecological relationships between vegetation and the environment has become an essential means in the field of research of modern vegetation ecology. In this article, based on data from 84 quadrates, forest communities in this reserve were investigated using TWINSPAN, DCA and DCCA. The results will be helpful in the construction and development of Pangquangou National Nature Reserve. Using TWINSPAN, the forest communities were classified into seven types. The distribution pattern of vegetation reflects the comprehensive influence of environments. The results of DCA and DCCA clearly reflect the relationship between the pattern of forest communities and environmental gradients. The ordination result of DCCA indicates that altitude is more important than other environmental factors because the change of altitude gradient will lead to changes in the temperature and humidity gradients. The first of the DCA ordination axes indicates the humidity gradient, and the second indicates the temperature gradient. All these results show that the main factors restricting the distribution of communities in this reserve are temperature and humidity. The ecological meaning of the ordination axis in DCCA is much clearer than that in DCA, and the species-environment correlation of DCCA is more obvious than DCA. The first DCCA axis indicates the altitude gradient among the communities, while the second is the gradient in aspect and slope among the communities. DCCA ordination can simultaneously express similarities of species and environment. Therefore, the quadrat location in the DCCA ordination figure is much closer than in the DCA.