Caratteri Fondamentali della Vegetazione delle Paludi Pontine

Abstract

Observations in various microhabitats as regards the composition of different growth forms in an alpine region of Tungnath, northwestern Himalaya, were carried out. Maximum frequency was displayed by mat-forming forbs (Trachydium roylei, 100%) throughout the growing season (May–October). Maximum values for density and Importance Value Index (IVI) (452.10 plants m^?2 and 157.8, respectively) were recorded for tussock graminoids, Poa annua (L.). The IVI of different growth forms exhibited significant positive correlation with stoloniferous graminoids (KD), mat forming forbs (TR) and prostrate creeping dwarf shrubs (GT). A significant positive correlation with plant available water was also detected for mat-forming forbs (TR) and one of the plant species (CN) representing stoloniferous graminoids. The values of concentration of dominance (Cd) ranged from 0.0001 to 0.277. Diversity index (H) was highest (0.532) for tussock graminoids [Danthonia cachemyriana (Jaub &; Spach.), P. annua] indicating the relative abundance of this growth form. Overall, tussock graminoids are dominant in the region, indicating stable and moderate steepness of the slopes, the major topographic feature of Tungnath. Besides topography, grazing, anthropogenic activities and interactions among associated species are the determining factors for the phytostructure of alpine communities in Himalaya.     

喜马拉雅山错那段不同海拔梯度蚂蚁多样性

为了揭示喜马拉雅山不同海拔梯度蚂蚁的多样性规律,采用样地调查法研究了喜马拉雅山错那段北坡、南坡和山间谷地的蚂蚁群落.共采集蚂蚁标本7516头,隶属于2亚科、5属、7种.利用EstimateS 9.1.0程序对该地区蚂蚁物种丰富度进行估计并绘制物种累计曲线,结果表明错那段的蚂蚁物种实际观察值等于或接近该地区蚂蚁丰富度的估计值.多样性分析显示,错那段3个垂直带蚂蚁物种数目、Shannon-Wiener多样性指数和Fisherα指数顺序为北坡>山间谷地>南坡,优势度指数顺序为北坡<山间谷地<南坡,个体密度顺序为北坡>南坡>山间谷地;在各垂直带上蚂蚁群落物种数目、个体密度、多样性指数总体随海拔升高呈现垂直带中下部较高,垂直带上部较低;群落各项指标更多的表现出"多域效应"现象,降水和海拔对蚂蚁物种丰富度和多样性起决定作用,凋落物的质量和坡度有重要影响.相关性分析发现错那段蚂蚁物种多样性指数与草本盖度极相关,优势度指数与灌木盖度相关性显著;群落相似性分析表明植被类型和海拔高差对蚂蚁群落间相似性有重要作用.     

Gemmae in Octoblepharum albidum Hedw.

Abstract

The nine Tortula species and two varieties known from the islands of the subantarctic botanical zone are distinguished in a key. New synonymy, taxonomic notes and illustrations are provided and the presently known distribution of the species is reported and discussed.     

Integrated sedimentological,ichnological and sequence stratigraphical studies of the Koti Dhaman Formation (Tal Group), Nigali Dhar Syncline,Lesser Himalaya,India: paleoenvironmental,paleoecological, paleogeographic significance

Abstract

Integrated ichnology, sedimentology and sequence stratigraphy of the Lower Quartzite Member to the Arkosic Sandstone Member of the Koti Dhaman Formation (Cambrian Series 2, Stage 4), Tal Group, Nigali Dhar Syncline, Lesser Himalayan lithotectonic zone are presented. Trilobite traces of Gondwanan affinity i.e., Cruziana salomonis, Cruziana fasciculata, Rusophycus dispar and Rusophycus burjensis are recorded along with Arenicolites isp. and Skolithos isp. from the Lower Quartzite Member. A rich and diverse ichnoassemblage attributed to the Cruziana ichnofacies is described for the first time from the Arkosic Sandstone Member of the same formation. Seven ichnofossil assemblages, i.e., Cruziana-Rusophycus, Planolites-Palaeophycus, Cruziana problematica, Diplichnites, Cochlichnus anguineus, Bergaueria perata and Psammichnites gigas have been recognized in the Lower Quartzite to Arkosic Sandstone members of the Koti Dhaman Formation. Seven sedimentary facies i.e., sandstone–shale facies (FT1), cross-bedded (trough and planar) sandstone (FT2), bedded sandstone facies (FT3), shale facies (FT4), shale–sandstone facies (FT5), shale-rippled sandstone facies (FT6) and planar and trough cross-laminated sandstone (FT7) and four facies associations FA1-FA4 are identified in the Koti Dhaman Formation. The formation contains shallowing upward parasequences of a tidal flat complex. Overall, two major events are recognized: i) the break in sedimentation between the Lower Quartzite Member and the overlying Shale Member probably related to forced-regressive event and ii) the facies shift from FT6 to FT7 of the Arkosic Sandstone Member represents an erosive transgressive event; the surface is interpreted as wave ravinement surface, which also serves as a sequence boundary. Integrated ichnology, sedimentology and sequence stratigraphic studies indicate that the Lower Quartzite Member was deposited in a shallow subtidal sand sheet complex and tidal flat complex; the Shale Member was deposited in a mud flat setting of a tidal flat complex, and the Arkosic Sandstone Member in a mixed-flat (tidal flat complex) to sand sheet complex front and margin (subtidal sand sheet complex). Overall, the lower to middle part of the Koti Dhaman Formation represents a tide-dominated shallow subtidal–intertidal to mud-flat subenvironments of the tidal flat complex. A palaeogeographic reconstruction of lower Cambrian (516–514?Ma) is presented based on the distribution of trilobite traces from the Lesser Himalaya and the Bikaner–Nagaur area of Peninsular India (eastern Gondwana), Egypt, Jordan, Turkey (western Gondwana) and Canada (Avalonia).     

The marine algae of Berwickshire: a detailed checklist

Summary

Details are given of the distribution of 197 species of seaweed in Berwickshire. These include previous records from herbaria and the published literature, together with records gathered in a programme of field work carried out between 1987 and 1991.     

Phylogenetic diversity,structure and diversification patterns of endemic plants along the elevational gradient in the Eastern Himalaya

ABSTRACT

Background: Several studies have documented the variation in species diversity patterns along elevational gradients in the Himalaya, but few have reported the evolutionary and biogeographic processes behind these patterns.

Aims: To understand whether evolutionary history and phylogeny have any role in structuring plant species communities along an elevational gradient in the Sikkim Himalaya.

Methods: We used data on endemic plant species occurrence from primary and secondary sources to construct family-level phylogenetic supertrees for different growth forms with the help of Phylomatic tool of Phylocom. These phylogenetic supertrees were used as a base for testing phylogenetic diversity (PD), niche conservatism, diversification time patterns and phylogenetic structure of various plant growth forms along an elevational gradient.

Results: PD was the highest at mid-elevations for all growth forms and PD had a significant positive correlation with endemic species richness. Species at mid-elevations were dominated by the ancestral/primitive taxa. There was phylogenetic clustering at higher elevations and phylogenetic overdispersion at lower and mid-elevations for the majority of the growth forms.

Conclusions: Time-for-speciation effect and niche conservatism along elevation (retention of niche-related ancestral elevational distribution over evolutionary time scale by species) together determine plant species diversity patterns in the Himalaya.     

A new species of Astragalus L. (Leguminosae) from India based on morphological and molecular markers

A new species, Astragalus himachalensis , is described and illustrated from the Himalaya in India. The species grows occasionally in different parts of the cold desert of Lahul-Spiti (Himachal Pradesh). It resembles A. himalayanus , but differs chiefly in the small size of the plants (length, 5–15 cm), diadelphous stamens, and small pods (length, 5–6 mm) with the stipe length (2–3 mm) more or less equal to the calyx length. The similarities and significant differences between A. himachalensis and A. himalayanus were confirmed by analyses of random amplification of polymorphic DNA (RAPD) and directed amplification of minisatellite DNA (DAMD) markers. RAPD and DAMD methods clearly distinguished between the two species and were in congruence with morphological markers. © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 154 , 27–34.     

Increase in light interception cost and metabolic mass component of leaves are coupled for efficient resource use in the high altitude vegetation

Global syntheses of leaf trait scaling relationships report an increase in light interception costs or ‘diminishing returns’ with increase in leaf area. However, variation in light interception costs across ecological gradients and plant strategies to cope up with these costs are not adequately understood. We analyzed leaf area (A) – leaf dry mass (M), leaf water mass (W) – M and W – A scaling relationships in plants occurring in a high altitude region of western Himalaya across environmental gradients to understand changes in light interception cost and metabolic mass component. M represents light interception cost, whereas, W is considered as a proxy of metabolic mass component for liquid phase being the ultimate source of metabolic activity. Trait values were measured from 9278 leaves belonging to 136 dominant species occurring at different sites, slope aspects, elevations and habitat types. Overall, light interception cost increased with increasing A (scaling exponent (α) < 1 in A–M relationship) and metabolic mass component increased disproportionately high with increasing M and A. We found significant differences in scaling exponents of leaf trait relationship between sites, elevations, slope aspects and habitat types, indicating that increase in light interception cost was more evident at higher elevations, southern slopes and open habitats. Further, with increase in light interception cost, metabolic mass component also increased (α > 1 in W–M and W–A relationships). The changes in scaling exponents of various leaf trait relationships across ecological gradients indicated that vegetation of different regions have differences in light interception cost and metabolic mass component. Moreover, increasing light interception cost (increase in mechanical and hydraulic tissues) with increasing A and increasing metabolic mass (leaf thickness) with increasing A and M are favored in high altitude vegetation. This could be a key strategy of high altitude plants for efficient resource capture and use in harsh environments.