Determination of species-area relationships and minimum sampling area for the shrub communities in the arid valley in the upper reach of the Minjiang River, China

The minimum sampling areas (MSAs) for the shrub communities in the arid valley in the upper reach of the Minjiang River, China, were studied by fitting community species-area relationships using 3 types of equations. The MSAs were determined at the proportional factor (ρ) 0.6, 0.7, 0.8 and 0.9. The proportional factors represent the proportion of the number of species within a sampling plot in the total number of species. The MSAs of the shrub communities at different elevations and on different slope faces for ρ = 0.6, 0.7 and 0.8 were all around 100 m². Hence, the MSAs could be set to be 100 m² (10 m × 10 m) at 60%–80% precision levels. For ρ = 0.9, that is, for a 90% precision level, the MSAs were less than 200 m² (10 m × 20 m). The MSAs and species richness increased gradually with the rising elevation. At the elevation below 2000 m, the MSAs and species richness on the north-facing slope were larger than those on the south-facing slope. However, at the elevation around 2200 m, there was no difference amongst different facing slopes. For the shrub communities in the arid valley in the upper reach of the Minjiang River, the species-area curves by fitting the first two equations are better than that by fitting the third equation.     

2017—2020年珠江口棘头梅童鱼的种群特征

为了掌握珠江口重要经济鱼类棘头梅童鱼的种群特征,根据2017—2020年春(3—4月)、秋(9—10月)两季在珠江口海域开展的底拖网调查及采集到的棘头梅童鱼样本,对其生物学特征和资源密度分布特征进行了初步分析。结果表明: 珠江口棘头梅童鱼体长、体重变化范围分别为22～168 mm、0.23～103.11 g,其中雌性个体的体长、体重均大于雄性个体,未见明显的小型化现象;性成熟体长集中在90～140 mm,未见性成熟提早现象。总体长体重关系式中的异速生长因子b值为2.9057,且年际变化小,而条件因子a值(3.029×10^-5)小于1988年该海域的调查结果,说明珠江口棘头梅童鱼整体生长发育良好,但栖息地环境质量(饵料供应、生长环境)下降。研究海域梅童鱼的开发率E为0.67,处于过度捕捞状态;梅童鱼资源密度平均值为77.73 kg·km^-2, 中西侧资源密度大于东侧,在纬度方向上总体分布均匀;根据4个资源密度高值区初步推测其产卵场在南沙港附近。2017—2020年的年平均资源密度比1980—1982年下降了93.5%,为持续利用该资源,建议条件成熟时可于春季在产卵场设立保护区,以保护补充群体与产卵群体。     

黄河中游晋陕峡谷陕西侧龙门至壶口段新发现的石制品

2019-2020年,在黄河中游晋陕峡谷陕西一侧龙门至壶口段新发现9处旷野旧石器地点,采集石制品136件,部分石制品直接采自地层剖面上。康家岭地点石制品的埋藏地层为马兰黄土底部的洪积碎屑层,时代可能为晚更新世早期。苏家岭地点有1件石制品出自MIS3阶段弱古土壤层之下的洪积碎屑层,光释光年龄为距今7.2±0.7万年。其余大部分石制品的埋藏地层为马兰黄土层,时代为晚更新世中、晚期,其中凉泉沟地点埋藏石制品的黄土地层光释光年龄大于距今5万年。古人类加工石制品的原料主要为砾石,岩性以石英岩为主,其次为石英,此外还有少量燧石、细砂岩和硅质岩。石制品类型包括石核、石片、石器和断块。个体大小以中小型为主。石核和石片以自然台面者为主,剥片主要采用硬锤锤击法直接剥片,少量应用砸击法。石器有中小型的刮削器、凹缺器和大型的砍砸器,均属简单石核-石片技术产品。本次新发现的旧石器地点进一步扩大了晋陕峡谷地区旧石器时代遗存的时空分布范围,有助于后续相关研究工作的开展。     

基于高通量测序的乐安江冬季细菌群落特征分析

【目的】分析乐安江从上游至下游水体细菌群落结构组成变化,揭示细菌群落结构组成变化的影响因素。【方法】分析不同河段水体中C、N、P、Cu、Zn、As和Pb等化学指标。对水体DNA的16S rRNA基因进行高通量测序确定细菌群落特征。基于Bray-Curtis距离的采样点非度量多维尺度(NMDS)分析和聚类分析研究乐安江水体细菌群落结构差异,基于冗余分析(RDA)研究环境因子与细菌群落的关系。【结果】乐安江水体中C、N、P、Cu、Zn、As和Pb等化学指标含量中下游偏高。中游河水受德兴铜矿废水影响,细菌群落多样性降低,下游受农业、生活废水影响,细菌群落丰富度和多样性升高。水体中优势菌群为β-变形菌纲(Beta-proteobacteria,53.03%)、放线菌门(Actinobacteria,20.24%)和拟杆菌门(Bacteroidetes,14.75%)。中游受德兴铜矿废水影响,Beta-proteobacteria丰度增大,而Actinobacteria丰度减小;下游受微生物间捕食影响,Bacteroidetes丰度下降。在细菌群落与环境因子的关系中,DO是解释乐安江细菌群落结构变化的最佳环境因子。【结论】乐安江中游德兴铜矿废水和中下游农业、生活废水明显改变了水体细菌群落结构组成,使水体细菌群落特征从上游到下游发生显著变化。本研究为揭示人类活动对乐安江水生态环境的影响提供了参考性数据。     

Larval development of mandi-pintado Pimelodus britskii (Siluriformes: Pimelodidae)

This study investigated the morphology, morphometric and meristic characters of 117 larval Pimelodus britskii showing early development of head, eye, barbel and snout. Body and mouth pigmentation increased throughout development; the mouth was ventrally situated in the yolk-sac stage, becoming subterminal afterwards, and an embryonic fin was visible in all four stages observed. Post-flexion larval P. bristskii are distinguished from larval P. ortmanni by having 47–50 myomeres (v. 36).     

Influence de la spéciation du cuivre sur les populations phytoplanctoniques naturelles de la rivière du Saguenay,Québec,Canada Influence of Copper in Various Forms on Natural Phytoplanktonic Populations from the Saguenay River,Quebec, Canada

In 1981, experiments to study the toxicity of copper in its ionic, complexed (to humic acid) and adsorbed (on cellulose fibers from a local paper mill) forms on species composition, standing crop, and photosynthesis of phytoplankton were conducted in chemostats with natural aggregations composed mainly of either green algae or of diatoms from the Saguenay River. In the aggregations of green algae, the rates of primary production were more strongly inhibited by copper than were the chlorophyll a concentrations, whereas the cell numbers, standing crop and rates of primary production of the diatoms were all strongly inhibited by copper.     

沙颍河流域人为输入对水体水化学组成的影响

人类活动输入影响河流水体化学组成,增加经河流体系向海洋输出物质的通量,影响全球物质循环过程.有效识别人为输入的影响途径和范围对于量化人类活动对全球物质循环的影响具有重要作用.沙颍河是淮河上游最大支流,流域水体受人为输入影响严重,通过研究沙颍河流域强人为输入对河水水化学组成的影响过程,有利于弄清楚强烈人为活动干扰下河流输...     

Characteristics of the Summer Hydrological Regimen and Chlorophyll Distribution in the Volga River Reservoirs

Field observations on chlorophyll content and hydrological parameters such as temperature, dissolved oxygen and conductivity profiles, Secchi disk transparency and water color were carried out at 5 reservoirs of the Mid and Lower Volga River during August 1990 and 1991. Principal Component Analysis distinguished four classes from 46 sampling points based on the hydrological regimen and phytoplankton development.     

Organic matter processing by a stream-segment ecosystem: Fort River,Massachusetts, U.S.A.

An annual organic matter budget for a 1700 m segment of Fort River (Massachusetts, USA) is presented. Primary production in this fourth order stream exceeds litter input annually, however ecosystem P/R is 0.5. Respiration in excess of gross primary production is supported by allochthonous organic matter imported from upstream reaches. The relative contribution of organic matter size fractions to stream consumers depends upon biologic lability, rate of input, and residence time in the ecosystem. Particles of seston size (1 μm to 1 mm) are most heavily used by consumers, however dissolved organic matter represents the largest input component. Microorganisms are the predominant consumers in this soft-water, nutrient-poor stream ecosystem. A conceptual model for assessing the processing efficiency of stream ecosystems is presented and discussed in terms of several headwater to estuary gradients.     

Variations in levels of clonality among Populus nigra L. stands of different ages

The evolution of genotypic diversity with population age remains poorly explored in clonal plant populations despite the potential for important shifts to occur through the course of time. Woody sprouting species are particularly under-represented in studies investigating intra-specific variations in levels of clonality from one locality to the next and through time. In this study we sought to determine the incidence and frequency of replicate genotypes in natural Populus nigra L. (Salicaceae) stands of different ages. Ten stands of this woody riparian sprouting species were selected in each of three distinct age groups (young, middle-aged and old) along a 30 km stretch of the River Garonne (south-west France). Leaf samples were collected from 15 neighbouring trees in each stand (450 samples in total) and replicate genotypes were identified using five SSR markers. Replicate genotypes were identified in two-thirds of all stands sampled (i.e. 50 of young stands, 100 of middle-aged stands and 50% of old stands). Young stands had significantly fewer replicated genotypes than middle-aged or old stands, while middle-aged stands had the greatest number of replicated genotypes. Replicate genotypes were most often found to occur as nearest neighbours and formed relatively small, discrete units (i.e. 2–4 trees growing in close proximity to one another). This suggests that asexual regeneration frequently occurs through flood-training in this species, although asexual regeneration from translocated fragments also evidently occurs as evidenced by 11 cases of replicate genotypes occurring in widely separated stands (up to 19 km apart). The results of this study highlight the need for a hierarchical sampling strategy in space and across age groups for an accureate understanding of the genotypic structure of woody sprouting species populations. Conservation and management of effective population sizes will benefit from better insight into not only spatial, but also temporal variations in levels of genotypic diversity.Co-ordinating editor: J. Tuomi