The upper Shemshak Formation (Toarcian–Aalenian) of the Eastern Alborz (Iran): Biota and palaeoenvironments during a transgressive–regressive cycle

The siliciclastic, up to 4,000 m thick Upper Triassic–Bajocian Shemshak Formation is widespread across the Iran Plate, especially in the Alborz Mountains of northern Iran. In contrast to its lower, generally non-marine part, the upper part is marine. Based on the Tazareh section of the eastern Alborz, an integrated analysis of this marine interval is presented. The 1,700 m thick marine sedimentary succession records a gradual deepening from inner to mid and outer shelf environments from the Middle Toarcian to early Late Aalenian. During the Late Aalenian–Early Bajocian, the trend was reversed and infilling of the basin by a large delta system occurred. This general facies development reflects a nearly symmetrical transgressive–regressive (T–R) megacycle, terminated by the inter-regional mid-Cimmerian tectonic event. A renewed transgression in the early Late Bajocian initiated a subsequent sedimentary megacycle. The bioturbated mid and outer shelf sediments contain a low to moderately diverse benthic fauna dominated by deep burrowing bivalves, often preserved in the growth position. A hierarchy of four orders of sedimentary cycles can be recognized (parasequences, parasequence sets, unconformity-bounded third-order depositional sequences, and the 13 ma long second-order T–R megacycle). A regional correlation with the Jajarm area (200 km to the east) shows a very similar temporal facies pattern of the upper Shemshak Formation. The eastern Alborz T–R cycle is completely out-of-phase with other (eustatic) sea-level curves, suggesting regional tectonic control. Rough estimates of subsidence rates give an average value of 126 m/ma. However, much higher values for the Aalenian (230 m/ma), particularly the Late Aalenian (700 m/ma), indicate a distinct increase in subsidence rate towards the Early Bajocian mid-Cimmerian tectonic event. These high subsidence rates suggest that the sediments of the Shemshak Formation of the eastern Alborz formed in a (young) rift basin.     

Associations among spring-dependent aquatic assemblages and environmental and land use gradients in a Mojave Desert mountain range

In many arid landscapes, springs provide the only reliable source of water. Accordingly, both native species and human land uses, including diversion of water, livestock grazing, and recreation, tend to concentrate around springs and spring‐fed riparian areas. We examined whether species richness and composition of aquatic macroinvertebrates at 45 springs in the Spring Mountains, an isolated mountain range in the eastern Mojave Desert (Nevada, USA), could be predicted using readily measured environmental gradients and estimates of disturbance intensity. The Spring Mountains is a focus of regional conservation planning, and managers are charged with prioritizing its springs for conservation and rehabilitation. Our results suggested that species richness of aquatic macroinvertebrates in the Spring Mountains system may be greatest at intermediate levels of natural and human disturbance. Discharge and springbrook length appeared to be only weakly correlated with species richness, whereas neither elevation, nor water temperature, nor electrical conductance was significantly associated with species richness. Nestedness analyses demonstrated that species present in relatively depauperate locations tended to be subsets of the species present in locations that were richer in species, but that pattern did not appear to be driven by either disturbance intensity or by the environmental variables we measured. Disturbance intensity was not associated with the extent to which species presences and absences were predictable. Although our results should not be interpreted to mean that major environmental gradients and disturbance intensity have no effect on distributional patterns of aquatic invertebrates in the Spring Mountains, the ability of these variables to serve as predictors of species richness and composition may be relatively low. Springs and other wetlands in arid landscapes are characterized by isolation and unpredictable disturbances, and faunal responses to environmental gradients may tend to be individualistic and taxon‐specific.     

祁连山北坡霸王枝-叶性状关系的个体大小差异

枝与叶片权衡关系的个体大小差异性, 是物种形成不同冠层结构充分利用空间资源的一种策略, 有利于植株通过构型调整自身的光合效率和增强竞争力。在祁连山北坡荒漠草地, 根据体积将霸王(Zygophyllum xanthoxylum)分为3个大小等级(I级: (植株体积的立方根(d) ≤ 60 cm)、II级(60 cm < d ≤ 120 cm)和III级(d > 120 cm)), 采用标准化主轴估计方法, 研究了不同大小等级霸王种群枝长度与叶面积、叶数量的生长关系。结果表明: 随着植株大小等级增大, 霸王的枝长度、叶面积、枝横截面积逐渐增大, 叶数量呈逐渐减小趋势; 霸王枝长度的增长速度大于或等于叶面积的增长速度, 枝长度的增加速度大于叶数量的增加速度; 随着个体大小等级的增加, 霸王枝长度与叶面积的异速斜率、枝长度与叶数量回归方程的y轴截距均显著减小, 即植株叶面积与枝长度比值、叶数量的投入均显著降低。为提高资源利用效率, 霸王小个体植株倾向于短枝上着生大量的小叶, 大个体植株趋向于长枝上着生少量的大叶, 随植株大小等级增加, 叶面积增加而叶数量降低, 对小枝的资源配置具有一定的影响。     

大兴安岭硅藻的中国新记录属、种

对大兴安岭硅藻进行了形态分类学研究, 发现了部分中国新记录属及中国新记录种。研究共报道大兴安岭硅藻10属10种, 对这些属、种的形态学特征进行了详细的描述, 并提供了图片资料。其中3个属为中国新记录属, 分别为: 北方藻属Boreozonacola Lange-Bertalot、Kulikovskiy Witkowski、矮羽纹藻属Chamaepinnularia Lange-Bertalot Krammer、微肋藻属Microcostatus Johansen Sray。本文给出其余7个属的详细特征描述, 为其他相关研究提供参考。观察到中国新记录种9种1变种, 分别为: 胡斯特北方藻Boreozonacola hustedtii Lange-Bertalot, Kulikovskiy Witkowski、海塞矮羽纹藻Chamaepinnularia hassiaca (Krasske) Cantonati Lange-Bertalot、墙生微肋藻Microcostatus maceria (Schimanski) Lange-Bertalot、异辐节卡维藻Cavinula heterostauron (Germain) Van de Vijver、类印加等列藻Diadesmis ingeaeformis Hamilton Antoniades、沼地盖斯勒藻Geissleria paludosa (Hustedt) Lange-Bertalot Metzeltin、忽视蹄形藻Hippodonta neglecta Lange-Bertalot, Metzeltin Witkowski、沙拉泥生藻Luticola charlatii (Peragallo) Metzeltin, Lange- Bertalot、原子麦尔藻特许变种Mayamaea atomus var. permitis (Hustedt) Lange-Bertalot、莱维迪细篦藻Neidiopsis levanderi (Hustedt) Lange-Bertalot Metzeltin。       

Plant Functional Group Classification of Herbaceous Species in Quercus wutaishanica Communities in the Taiyue Mountains,Shanxi Province of China

Quercus wutaishanica is warm temperate deciduous broad leaved forest region one of the typical vegetation types. Qwutaishanica vegetation types as a representative of Shanxi, is the main part of shanxi forest. Past research focuses on the subject of Qwutaishanica results, the study of the herb layer seldom reported. The understory layer dominant species of Qwutaishanica community on Qiliyu of Taiyue Moutains, whose abundances clearly vary along environmental(altitudinal) gradients.Herbaceous plants highly responsive to changes in environmental conditions that reflect the dynamic relations between vegetation and environment. In this paper, using the method of sample, investigated the community of Qwutaishanica on Qiliyu of Taiyue Moutains, Shanxi. We used the results of this investigation to calculate species importance values and frequency, which were used to identify 27 dominant species in herbages. χ2 tests, together with association coefficient and percentage cooccurrence, were used to measure interspecific associations of the dominant species of herbaceous. Plant functional types (PFTS) were defined according to interspecific associations and cluster analysis of the dominant species. In studies of forest understory plant assemblages, designating PFTs according to dominant herbaceous species is feasible. Dominant herbaceous species formed seven PFTs: each with its unique spatial distribution and morphological characteristics, are identifiedⅠ.amphigenous Ⅱ.pelouse edge Ⅲ.wet sparse Ⅳ.gap drought resistant Ⅴ.hill edge Ⅵ.alpine Ⅶ.dank. Plant functional types(PFTs) of herbaceous plants varies with altitude gradients, which reflect the relationship between Qwutaishanica and environment well.     

新疆天山一号冰川地区十种藓类植物叶尖的微形态观察

在光学显微镜和扫描电镜下,对新疆天山一号冰川地区生长的10种藓类植物的叶尖（毛尖）的形态、齿（刺毛）、疣、角质层纹饰等微结构进行观察,其中电镜观察结果均为首次报道。结果表明：10种藓类植物叶尖的顶尖细胞和边缘细胞大部分都是透明的,并且细胞壁厚,细胞腔大;而叶尖边缘内卷、粗糙,细胞壁厚,干时细胞壁上下或侧面凹陷,其上有较多的小孔,这些都是明显耐旱特征,有利于水分的吸收及抵御长期寒冷、反射太阳辐射对其伤害,叶尖的类型对苔藓植物科、属级的分类意义不大,但其微形态如叶尖细胞及边缘细胞的形状、数目、细胞壁的凹陷程度以及其上角质层纹饰、乳突的微形态在同属的不同种之间存在明显差异,对于属下种间的鉴定具有一定的分类学价值。     

Population structure and spatial pattern of predominant tree species in a pine–oak mosaic mixed forest in the Qinling Mountains,China

This study investigated a typical pine-oak mosaic mixed forest in the Qinling Mountains, China. In the sample plot, the population structure and spatial distribution of the stems were analyzed for the predominant species, to identify the mechanisms of species coexistence and successional trends of the forest. The population structures of all species were bimodally distributed, with young trees (DBH <1 cm) more abundant than older trees. The population structures of Quercus aliena var. acuteserrata was bimodal and rather continuous. However, Pinus tabuliformis and Pinus armandii were discontinuously bimodal, with distinct size deficiencies. Q. aliena var. acuteserrata trees were clumped throughout the plot, although those of P. tabuliformis and P. armandii were clumped at small scales. Notable negative spatial associations between Q. aliena var. acuteserrata and P. tabuliformis were found at almost scales. P. armandii and Q. aliena var. acuteserrata were negatively spatially associated at small scales but positively associated at large scales. Our findings suggest that interspecific competition gradually develops among the predominant tree species. The dynamics of the pine-oak mosaic mixed forest formed a mosaic distribution of uniformly mixed types, with the slow infiltration of Q. aliena var. acuteserrata populations that would eventually establish a pure stand.     

Hopes and challenges for giant panda conservation under climate change in the Qinling Mountains of China

One way that climate change will impact animal distributions is by altering habitat suitability and habitat fragmentation. Understanding the impacts of climate change on currently threatened species is of immediate importance because complex conservation planning will be required. Here, we mapped changes to the distribution, suitability, and fragmentation of giant panda habitat under climate change and quantified the direction and elevation of habitat shift and fragmentation patterns. These data were used to develop a series of new conservation strategies for the giant panda. Qinling Mountains, Shaanxi, China. Data from the most recent giant panda census, habitat factors, anthropogenic disturbance, climate variables, and climate predictions for the year 2050 (averaged across four general circulation models) were used to project giant panda habitat in Maxent. Differences in habitat patches were compared between now and 2050. While climate change will cause a 9.1% increase in suitable habitat and 9% reduction in subsuitable habitat by 2050, no significant net variation in the proportion of suitable and subsuitable habitat was found. However, a distinct climate change‐induced habitat shift of 11 km eastward by 2050 is predicted firstly. Climate change will reduce the fragmentation of suitable habitat at high elevations and exacerbate the fragmentation of subsuitable habitat below 1,900 m above sea level. Reduced fragmentation at higher elevations and worsening fragmentation at lower elevations have the potential to cause overcrowding of giant pandas at higher altitudes, further exacerbating habitat shortage in the central Qinling Mountains. The habitat shift to the east due to climate change may provide new areas for giant pandas but poses severe challenges for future conservation.     

Canada lynx use of burned areas: Conservation implications of changing fire regimes

A fundamental problem in ecology is forecasting how species will react to major disturbances. As the climate warms, large, frequent, and severe fires are restructuring forested landscapes at large spatial scales, with unknown impacts on imperilled predators. We use the United States federally Threatened Canada lynx as a case study to examine how predators navigate recent large burns, with particular focus on habitat features and the spatial configuration (e.g., distance to edge) that enabled lynx use of these transformed landscapes. We coupled GPS location data of lynx in Washington in an area with several recent large fires and a number of GIS layers of habitat data to develop models of lynx habitat selection in recent burns. Random Forest habitat models showed lynx‐selected islands of forest skipped by large fires, residual vegetation, and areas where some trees survived to use newly burned areas. Lynx used burned areas as early as 1 year postfire, which is much earlier than the 2–4 decades postfire previously thought for this predator. These findings are encouraging for predator persistence in the face of fires, but increasingly severe fires or management that reduces postfire residual trees or slow regeneration will likely jeopardize lynx and other predators. Fire management should change to ensure heterogeneity is retained within the footprint of large fires to enable viable predator populations as fire regimes worsen with climate change.     

新疆天山一号冰川地区12种藓类植物叶形态结构研究

采用石蜡切片和扫描电镜的方法,对新疆天山一号冰川地区的12种藓类植物叶片结构及叶表面微形态进行了观察。结果显示,不同苔藓植物叶细胞、中肋、细胞壁、细胞表面等各项指标在类型、大小、分布、干燥时细胞壁的凹陷程度以及表面角质层纹饰和小孔形态、分布等都明显不同,这些微形态特点不仅在藓类植物属下种间的区分上具有分类学意义,同时也反映出藓类植物叶片为保水抗旱,抵御长期寒冷、多风和强光照射等恶劣环境对其的伤害而形成的生存策略。本研究结果为苔藓植物在极端环境地区的生态学功能研究提供了重要的科学依据。