Ichnology of Lower Jurassic beach deposits in the Shemshak Formation at Shahmirzad,southeastern Alborz Mountains,Iran

A 19 m thick package of well-sorted lowermost Jurassic (Hettangian-Lower Sinemurian?) sandstones within the Shemshak Formation of the southeastern Alborz Mountains displays features characteristic of foreshore to upper shoreface environments such as tabular bedding, low-angle lamination, trough cross-stratification, parting lineation, and oscillation ripples. In contrast to most other beach successions recorded in the literature the sandstones contain a trace fossil assemblage characterised by low abundance but comparatively high diversity. The assemblage, comprising 14 ichnotaxa, is dominated by Palaeophycus heberti, Rhizocorallium irregulare, Gyrochorte comosa, and Parahaentzschelinia surlyki. Contrary to predictions, which assume a dominance of suspension-feeders in such high-energy environments, the trace fossil assemblage represents a variety of ethological groups ranging from suspension-feeders to deposit-feeders, detritus-feeders, scavengers, and a possible trap constructor (Ctenopholeus), whereby deposit-feeders predominate. This anomaly is explained by a high amount of organic detritus in the sediment, indicated by abundant plant material, and a position of the beach in the vicinity of a river mouth.     

The Carboniferous carbonates of the Dombar Hills (western Kazakhstan) and the problem of the Viséan–Serpukhovian boundary

The Upper Viséan–Serpukhovian ammonoid-rich carbonates in the Dombar Hills (Aktobe Region, western Kazakhstan) provide an excellent opportunity to calibrate the ammonoid and conodont zonations around the base of the Serpukhovian Stage, and are important for interregional correlation. A section in the Dombar Hills spanning the Viséan–Serpukhovian boundary is measured and its fossil content is analyzed. Two ammonoid genozones (Hypergoniatites-Ferganoceras and Uralopronorites-Cravenoceras) and two conodont zones (Lochriea nodosa and Lochriea ziegleri) are recognized. The section displays a contact between the Hypergoniatites-Ferganoceras and Uralopronorites-Cravenoceras ammonoid genozones in a continuous succession and an evolutionarily early appearance of the genus Cravenoceras. The base of the Serpukhovian Stage is drawn at the level of the first appearance datum (FAD) of the conodont Lochriea ziegleri, which, as in the Verkhnyaya Kardailovka section (potential GSSP candidate, South Urals, Russia) enters within the Hypergoniatites-Ferganoceras ammonoid Genozone.     

A Spatial Model to Prioritize Sagebrush Landscapes in the Intermountain West (U.S.A.) for Restoration

The ecological integrity of Sagebrush ( Artemisia spp.) ecosystems in the Intermountain West (U.S.A.) has been diminished by synergistic relationships among human activities, spread of invasive plants, and altered disturbance regimes. An aggressive effort to restore Sagebrush habitats is necessary if we are to stabilize or improve current habitat trajectories and reverse declining population trends of dependent wildlife. Existing economic resources, technical impediments, and logistic difficulties limit our efforts to a fraction of the extensive area undergoing fragmentation, degradation, and loss. We prioritized landscapes for restoring Sagebrush habitats within the intermountain western region of the United States using geographic information system (GIS) modeling techniques to identify areas meeting a set of conditions based on (1) optimum abiotic and biotic conditions favorable for revegetation of Sagebrush; (2) potential to increase connectivity of Sagebrush habitats in the landscape to benefit wildlife; (3) location of population strongholds for Greater Sage-Grouse ( Centrocercus urophasianus , a species of conservation concern); and (4) potential impediments to successful restoration created by Cheatgrass ( Bromus tectorum , an invasive exotic annual grass). Approximately 5.8 million ha in southwestern Idaho, northern Nevada, and eastern Oregon met our criteria for restoring Wyoming big sagebrush ( Artemisia tridentata ssp. wyomingensis ) and 5.1 million ha had high priority for restoring Mountain big sagebrush ( A. tridentata ssp. vaseyana ). Our results represent an integral component in a hierarchical framework after which site-specific locations for treatments can be focused within high-priority areas. Using this approach, long-term restoration strategies can be implemented that combine local-scale treatments and objectives with large-scale ecological processes and priorities.     

Classification and ordination in the Indian Peaks area,Colorado Rocky Mountains

Summary A mid-latitude, Northern Hemisphere alpine vegetation in the Colorado Rocky Mountains was suitable for analysis by syntaxonemie and numerical methods, which interpreted the Braun-Bianquet association data, distributed by habitat and vegetation dominance types, correspondingly. Classification and ordination yielded complementary, interpretable results, which combined were more informative than results of either technique alone. Syntaxonomic results can faeilitate the interpretation of numerical results; the syntaxonomic relationships can be clarified by the results of numerical analysis.Alliances and orders of the Braun-Blanquet hierarchy, and their diagnostic taxa groups were derived by numerical methods from an association/taxa matrix. On the basis of this matrix, numerical methods demonstrated some of the environmental gradient complexes controlling the compositional variation. The compositional distinctiveness and uniformity of orders and alliances parallel environmental distictiveness and uniformity.The following attributes of the sampled vegetation and environment were probably responsible for the successful combination of syntaxonomic and numerical results: 1. The sampled area as a geographically limited universe, characterized by relative environmental, biotic, and historical distinctiveness and uniformity, 2. The wide range, high diversity, and clear denfinition of habitat and vegetation dominance types. Because it effectively summarizes and simplifies field data, syntaxonomy can play an important role in building local vegetatio models.Most of the figures in this paper are from a book version of a University of Colorado, Department of Environmental, Population, and Organismic Biology, Ph. D. thesis which was produced at the Institute of Arctic and Alpine Research. I would like to thank Dr. P.J. Webber, the thesis advisor, for his support, for suggesting the numerical methods, and for computer programs which were written by W.F. Reid. Vicki Dow, Marilyn Joel, and Karen Sproul drafted the majority of figures. I am grateful to Gwen Archer for editorial help.     

祁连山森林生态环境与黑河流域径流量的灰色关联分析和拓扑预测

甘肃省河西走廊由于远离海洋和受高山阻隔而成为干旱区。但因特殊的地理环境而有南部祁连山水源涵养林调蓄降水和冰雪融水,形成了三大内陆河水系,灌溉河西走廊7.0×10~5     

Phage display and crystallographic analysis reveals potential substrate/binding site interactions in the protein secretion chaperone CsaA from Agrobacterium tumefaciens

The protein CsaA has been proposed to function as a protein secretion chaperone in bacteria that lack the Sec-dependent protein-targeting chaperone SecB. CsaA is a homodimer with two putative substrate-binding pockets, one in each monomer. To test the hypothesis that these cavities are indeed substrate-binding sites able to interact with other polypeptide chains, we selected a peptide that bound to CsaA from a random peptide library displayed on phage. Presented here is the structure of CsaA from Agrobacterium tumefaciens (AtCsaA) solved in the presence and absence of the selected peptide. To promote co-crystallization, the sequence for this peptide was genetically fused to the amino-terminus of AtCsaA. The resulting 1.65 Å resolution crystal structure reveals that the tethered peptide from one AtCsaA molecule binds to the proposed substrate-binding pocket of a symmetry-related molecule possibly mimicking the interaction between a pre-protein substrate and CsaA. The structure shows that the peptide lies in an extended conformation with alanine, proline and glutamine side chains pointing into the binding pocket. The peptide interacts with the atoms of the AtCsaA-binding pocket via seven direct hydrogen bonds. The side chain of a conserved pocket residue, Arg76, has an “up” conformation when the CsaA-binding site is empty and a “down” conformation when the CsaA-binding site is occupied, suggesting that this residue may function to stabilize the peptide in the binding cavity. The presented aggregation assays, phage-display analysis and structural analysis are consistent with AtCsaA being a general chaperone. The properties of the proposed CsaA-binding pocket/peptide interactions are compared to those from other structurally characterized molecular chaperones.     

Relationships of phytogeography and diversity of tropical tree species with limestone topography in southern Belize

Aim The flora of northern Mesoamerica conventionally has been thought to be derived from taxa that emigrated from South America, but this view has recently been challenged as too simple. The dominance of limestone substrata in much of northern Mesoamerica, and its rarity in the rest of the continental Neotropics, may be one cause of the complexity of northern Mesoamerican floristics. Furthermore, northern Mesoamerica experiences longer and more intense seasonal drought than the rest of the continental Neotropics. As edaphic drought is accentuated with elevation on limestone soils, it may be expected that different topographic features have different phytogeographical affinities for seasonally drought‐prone areas of the Neotropics. The objective of this study was to test for effects of different topographic positions on the composition, phytogeography and diversity of tree species in a limestone area of Belize. Location Maya Mountains, Belize, Mesoamerica. Methods The diversity and local, regional, and hemispheric distributions of tree species on limestone valley floors, lower and upper slopes, and ridges were compared in southern Belize using 2 × 500 m transects as sample plots. Results Stem density increased, and percentage of large trees decreased, significantly with elevation above the valley floors. The proportions of species that had widespread distributions decreased significantly with increasing elevation above the valley floors. The proportions of species having northern Mesoamerican distributions increased significantly with elevation above the valley floors. All of the forests generally had the strongest phytogeographical affinities for the Petén (Guatemala) and Mexico, but greater affinities for the Yucatán were observed with increasing elevation above the valley floors. Species with distributions including the Greater Antilles made up an increasingly significant element, in terms of species and numbers of stems, with increasing elevation above the floors of valleys. Valley floors and ridges had the highest percentages of species unique to their topographic positions, 61% and 39% of their species, respectively, and were very similar in diversity. Slope forests had the highest diversity of trees ≥ 5 cm d.b.h. and were transitional in composition among the topographic positions. Main conclusions Despite relatively small changes in elevation, the composition, diversity and physical structure of the limestone forests changed significantly with topography. Such changes were presumably due to the greater edaphic drought experienced by these forests, and possibly due to lower levels of disturbance and differences in forest age, with increasing elevation above the floors of valleys.     

中国天山的平蒴藓属（Plagiobryum Lindb.）植物

平蒴藓属PlagiobryumLindb.(真藓科Bryaceae)植物在世界上共有8种(IndexMuscorum;Ochi1959,1970;Hedderson1990;Hedderson&Harold1990).中国大陆记录有3种分布(陈邦杰等1963;张满祥1978;Redfearn&Wu1986;Redfearn,Tan&He1996).其中,钝叶平蒴藓(P.giraldii(C.Muell.)Par.)特产于秦岭太白山(张满祥1978).作者基于在天山的实地考察和对标本的研究,报道了中国天山产的平蒴藓属植物共有2种即平蒴藓(P.zierii(Hedw.)Lindb.)和尖叶平蒴藓(P.demissum(Hoppe&Hornsch.)Lindb.),其中的平蒴藓为该区分布的首次记录.从种的现代地理分布和区域地理特点来看,这2种均属泛北极分布类型.依据所采的标本对它们进行了详细描述和绘图.中国天山平蒴藓属分种检索表如下1.植物体上部银白色或白色,下部红褐色.叶覆瓦状排列,卵圆形,内凹;中肋及顶或达于叶尖稍下处终止.孢蒴长棒状,平列或略倾斜1.平蒴藓P.zierii(Hedw.)Lindb.1.植物体红褐色.叶直立,披针形至卵圆状披针形;中肋突出叶尖.孢蒴梨形,下倾2.尖叶平蒴藓P.demissum(Hope&Hornsch.)Lindb.     

Potential pharmaceutical resources of the Qinling Mountain in central China:medicinal fungi

The present investigation on fungal diversity shows that there were rich fungal resources of up to 196 species,belonging to 41 families and 90 genera,in the Qinling Mountainous Range of central China.The dominant families were Polyporaceae,Russulaceae,Tricholomatacea and Lycoperdaceae,which comprised 107 species,54.59% of the total species.The dominant genera were Russula, Lactarius, Trametes, Phellinus, Coprinus,Lycoperdon,Suillu,and Calvatia,which consisted of 59 species,30.09% of the total species.According to the geographical characteristics,the genera were grouped into:cosmopolitan element (74.98%),pantropical element (3.57%),tropical element (1.02%) and north temperate element (21.43%),with the cosmopolitan element constituting the majority.Among these,the cosmopolitan and North Temperate Zone were characteristic of this region.Based on relevant literature review,the primary pharmaceutical action of the medicinal fungi in Qinling Mountain can be classified as follows:anti-cancer,anti-bacteria,anti-inflammation,relief of muscle rigidity and activation of collaterals,hemostasis,immunological regulation,as well as nourishing the stomach and tonification which means enhancing the body system.