Investigation of rangeland indicator species using parametric and non-parametric methods in hilly landscapes of central Iran

This study aimed to identify indicator species and explore the most important environmental and management variables contributing to vegetation distribution in a hilly upper dam landscape in Zagros Mountain chain, Iran. A stratified random sampling method was used to collect topographic, edaphic, management and vegetation data. The density and cover percentage of perennial species were measured quantitatively. Indicator species were identified using the two-way indicator species analysis. Besides calculating physiognomic factors in sample sites, 24 soil samples were collected from 0 to 30 cm of soil depth and analyzed in terms of gravel percentage, texture, saturation moisture, organic matter, pH and electrical conductivity in saturation extract, lime percentage, soluble calcium and magnesium, available phosphorus, Cation Exchange Capacity(CEC) and soluble sodium and potassium. Multivariate techniques including Canonical Correspondence Analysis and Multi-Dimensional Scaling were used to explore the relationships of species with environmental and management variables. Seven plants were identified as indicator species due to being significantly correlated with management(grazing or non-grazing) and edaphic variables such as CEC, soil texture, pH, CaCO3 percentage and physiographic variable including slope, elevation, and convex and concave formations(p < 0.05). Overall, overgrazing and its subsequent effects on soil characteristics, loss of vegetation cover and trampling were found as the major causes of deterioration. Sustainable and integrated management practices such as the implementation of appropriate grazing systems were suggested to enhance soil quality and reduce the accelerated erosion in upper dam zones.

Assessment of plant diversity of endemic species of the Saharo-Arabian region in Egypt

Savanna, semi-deserts, and hot deserts characterize the Saharo-Arabian region, which includes Morocco, Mauretania, Algeria, Tunisia, Libya, Egypt, Palestine, Kuwait, Saudi Arabia, Qatar, Bahrain, the United Arab Emirates, Oman, Yemen, southern Jordan, Syria, Iraq, Iran, Afghanistan, Pakistan, and northern India. Its neighboring regions, the Sudano-Zambezian region belonging to the Paleotropical Kingdom and the Mediterranean and Irano-Turanian regions included in the Holarctic Kingdom, share a large portion of their flora with the Saharo-Arabian region. Despite the widespread acknowledgment of the region's global importance for plant diversity, an up to date list of the Saharo-Arabian endemics is still unavailable. The available data are frequently insufficient or out of date at both the whole global and the national scales. Therefore, the present study aims at screening and verifying the Saharo-Arabian endemic plants and determining the phytogeographical distribution of these taxa in the Egyptian flora. Hence, a preliminary list of 429 Saharo-Arabian endemic plants in Egypt was compiled from the available literature. Indeed, by excluding the species that were recorded in any countries or regions outside the Saharo-Arabian region based on different literature, database reviews, and websites, the present study has reduced this number to 126 taxa belonging to 87 genera and 37 families. Regarding the national geographic distribution, South Sinai is the richest region with 83 endemic species compared with other eight phytogeographic regions in Egypt, followed by the Isthmic Desert(the middle of Sinai Peninsula, 53 taxa). Sahara regional subzone(SS1) distributes all the 126 endemic species, Arabian regional subzone(SS2) owns 79 taxa, and Nubo-Sindian subzone(SS3) distributes only 14 endemics. Seven groups were recognized at the fourth level of classification as a result of the application of the two-way indicator species analysis(TWINSPAN) to the Saharo-Arabian endemic species in Egypt, i.e., Ⅰ Asphodelus refractus group, Ⅱ Agathophora alopecuroides var. papillosa group, Ⅲ Anvillea garcinii group, Ⅳ Reseda muricata group, V Agathophora alopecuroides var. alopecuroides group, Ⅵ Scrophularia deserti group, and Ⅶ Astragalus schimperi group. It's crucial to clearly define the Saharo-Arabian endemics and illustrate an updated verified database of these taxa for a given territory for providing future management plans that support the conservation and sustainable use of these valuable species under current thought-provoking devastating impacts of rapid anthropogenic and climate change in this region.

新疆甘家湖梭梭林国家级自然保护区植被群落多样性及空间分布格局

新疆甘家湖梭梭林国家级自然保护区位于典型的绿洲-荒漠过渡带,明确保护区内主要植被类型及分布有助于生物多样性的保护与恢复。以2022年同期遥感影像为样点布设依据,在2023年8月进行实地调查,利用双向指示种分析法(TWINSPAN)对保护区内植被样方进行分类,计算各植被类型的α多样性指数,随后构建随机森林模型以评估植被样方的聚类结果并可视化。结果表明:(1)在甘家湖保护区,草本植物以猪毛菜属(Salsola spp.)分布最为广泛,灌木以梭梭(Haloxylon ammodendron)、碱蓬属(Suaeda spp.)、红砂(Reaumuria songarica)、角果藜(Ceratocarpus arenarius)等为这一地区主要的植被组成。(2)TWINSPAN将62个植被样方划分成14个类型,其中猪毛菜属+碱蓬属群丛(Ass.Salsola spp.+Suaeda spp.,G5)所占面积最大,且植被多样性最高;猪毛菜属+角果藜群丛(Ass.Salsola spp.+Ceratocarpus arenarius,G7)物种多样性较高,同时面积占比较大;单一植被型群丛(G14)Shannon-Wiener多样性指数与Simpson优势度指数均为最低,Pielou均匀度指数为1,在保护区中主要体现为农田和盐渍化极高的裸地。(3)随机森林模型的总体精度达到87.10%,Kappa系数达到0.8553,错分误差与漏分误差相对较小。(4)梭梭和白梭梭集中分布在保护区西北部核心区以及中偏南部的缓冲区。研究结果可为保护区后续精准管理奠定基础。

Spatial and environmental effects on plant communities in the Yellow River Delta, Eastern China

Types and structure of plant communities in the Yellow River Delta were investigated by using detrended canonical correspondence analyses （DCCAs） and a two-way indicator species analysis （TWINSPAN）. The distribution pattern and influential factors of the plant communities were also analyzed by testing elevation, slope, soil characteristics, longitude and latitude of 134 vegetation samples collected by representative plot sampling methods. Results showed that all the 134 vegetation samples could be divided into seven vegetation groups, separately dominated by Robinia pseucdoacacia, Imperata cylindrical, Miscanthus saccharifleus, Suaeda salsa, Aeluropus sinensis, Phragmites australis and Tamarix chinensis. The vegetation distribution pattern was mainly related to elevation, ground water depth and soil characteristics such as salinity and soluble potassium. Among the factors affecting distribution pattern of the plant communities, the species matrix explained by non-spatial environmental variation accounts for 45.2% of total variation. Spatial variation and spatial-structured environmental variation explain 11.8%, and 2.2%, respectively. Remained 40.8% of undetermined variation is attributed to biological and stochastic factors.

典范指示种分析──一个新的外在分类方法

本文描述一个新的外在分类方法——典范指示种分析。它是以典范对应分析排序轴为基础，同时使用植被数据和环境数据，其结果能更好地反映植被与环境的关系。我们用该方法对英国威尔士北部山地草甸的数据进行了分析，结果证明它是较理想的分析方法。

安西自然保护区放归普氏野马的采食斑块选择研究

客观地划分普氏野马放归区的植被群落,以此研究放归普氏野马在群落水平对采食斑块的选择策略,对评估放归区的食物资源状况和保护普氏野马具有重要意义。本文采用样线法结合双向指示种分类法( TWINSPAN )对安西自然保护区普氏野马放归区植被进行数量分类。之后以TWINSPAN分类的74个样方为对照,采用直接观察采样测定了80个普氏野马采食样方的9种生态因子,通过生态因子对比分析、Bailey s判别分析对普氏野马采食斑块选择进行了分析。结果表明,TWINSPAN分类将研究区74个样方归并为12个群丛类型。普氏野马采食斑块的植被盖度、草本盖度、针茅盖度、芨芨草盖度、群丛类型、生境类型都与对照地中的相应成分具有显著差异。普氏野马偏好的采食斑块特征是针茅、柽柳+芨芨草、驼绒藜为主要建群种的群丛,草本盖度(>15%),针茅盖度( 10%<C Stipa ≤15%),芨芨草盖度( 20%<C Achnatherum ≤40%),生境类型为流水滩地半灌木草原或湿地灌丛草甸。主成分分析表明斑块的生境类型( 0.955 )和群丛类型( 0.941 )对普氏野马的采食选择具有重要影响。

Spatial and environmental effects on plant communities in the Yellow River Delta,Eastern China

Types and structure of plant communities in the Yellow River Delta were investigated by using detrended canonical correspon-dence analyses(DCCAs) and a two-way indicator species analysis(TWINSPAN).The distribution pattern and influential factors of the plant communities were also analyzed by testing elevation, slope, soil characteristics, longitude and latitude of 134 vegetation samples collected by representative plot sampling methods.Results showed that all the 134 vegetation samples could be divided into seven vegetation groups, separately dominated by Robinia pseucdoacacia, Imperata cylindrical, Miscanthus saccharifleus, Suaeda salsa, Aeluropus sinensis, Phragmites australis and Tamarix chinensis.The vegetation distribution pattern was mainly related to elevation, ground water depth and soil characteristics such as salinity and soluble potassium.Among the factors affecting distribution pattern of the plant communities, the species matrix explained by non-spatial environmental variation accounts for 45.2% of total variation.Spatial variation and spatial-structured environmental variation explain 11.8%, and 2.2%, respectively.Remained 40.8% of undetermined variation is attributed to biological and stochastic factors.

Topography and soil content contribute to plant community composition and structure in subtropical evergreen-deciduous broadleaved mixed forests

Topography and soil factors are known to play crucial roles in the species composition of plant communities in subtropical evergreen-deciduous broadleaved mixed forests.In this study,we used a systematic quantitative approach to classify plant community types in the subtropical forests of Hubei Province(central China),and then quantified the relative contribution of drivers responsible for variation in species composition and diversity.We classified the subtropical forests in the study area into 12 community types.Of these,species diversity indices of three communities were significantly higher than those of others.In each community type,species richness,abundance,basal area and importance values of evergreen and deciduous species were different.In most community types,deciduous species richness was higher than that of evergreen species.Linear regression analysis showed that the dominant factors that affect species composition in each community type are elevation,slope,aspect,soil nitrogen content,and soil phosphorus content.Furthermore,structural equation modeling analysis showed that the majority of variance in species composition of plant communities can be explained by elevation,aspect,soil water content,litterfall,total nitrogen,and total phosphorus.Thus,the major factors that affect evergreen and deciduous species distribution across the 12 community types in subtropical evergreendeciduous broadleaved mixed forests include elevation,slope and aspect,soil total nitrogen content,soil total phosphorus content,soil available nitrogen content and soil available phosphorus content.

Tree assemblages and diversity patterns in Tropical Juri Forest,Bangladesh

Juri is a biodiversity-rich primary forest in Bangladesh, which remains ecologically unexplored. We identified tree species and examined the richness, alpha（a）diversity and floristic similarity patterns within the identified communities. Vegetation and environmental data were sampled in 120（0.04 ha） study plots. Tree communities were delimited by two-way indicator species analysis（TWINSPAN）. In total, 78 tree species of 35 families and58 genera were identified. TWINSPAN identified six tree communities： A—Tricalysia singularis; B—Kydia calycina-Castanopsis tribuloides; C—Polyalthia simiarum-Duabanga grandiflora; D—Ficus roxburghii; E—Artocarpus lacucha; F—Artocarpus lacucha. Mean richness, Shannon and Gini-Simpson indices were highest for the Polyalthia simiarum-Duabanga grandiflora community, while Ficus roxburghii showed lowest diversity. Significant differences（p = 0.05） in three diversity indices were recorded between Polyalthia simiarum-Duabanga grandiflora and Ficus roxburghii. Tree compositional similarity was greatest between Kydia calycina-Castanopsis tribuloides and Polyalthia simiarum-Duabanga grandiflora（0.712）.