以小时为步长的大兴安岭典型林分地表死可燃物含水率模型预测及外推精度

地表死可燃物含水率是火险天气和火行为预报中的重要指标.本研究基于时滞平衡含水率法(Nelson和Simard方法)及气象要素回归方法,于2010年9—10月对黑龙江省大兴安岭地区盘古林场不同郁闭度的山杨-白桦混交林、红皮云杉纯林,以及采伐迹地(原1∶1樟子松-白桦混交林)地表死可燃物含水率进行以小时为步长的连续测定,建立其预测模型,得到预测误差,并使用相应的模型对其他林分地表死可燃物含水率进行外推精度分析.结果表明:采用Nelson平衡含水率法构建的地表死可燃物含水率变化模型的平均绝对误差、平均相对误差和均方误差根(0.0154、0.104和0.0226)低于Simard法(0.0185、0.117和0.0256)和气象要素回归法(0.0222、0.150和0.0331).在外推效果方面,气象要素回归法的平均绝对误差、平均相对误差和均方误差根(0.0410、0.0300和0.0740)低于Simard法(0.610、0.492和0.846),但前两者均高于Nelson法(0.034、0.021和0.0660),说明以小时为步长的时滞平衡含水率法,尤其是Nelson法适用于大兴安岭地区所测林分.外推虽不能降低误差,但有助于提高现有模型应用至不同林分条件或大尺度范围内的地表死可燃物含水率预测精度和利用率.模型建模和外推误差与不同树种和郁闭度条件差异有关,研究时应根据不同林分和地点选择合适的平衡含水率模型.     

Snapshot of an early Paleoproterozoic ecosystem: Two diverse microfossil communities from the Turee Creek Group,Western Australia

Eighteen microfossil morphotypes from two distinct facies of black chert from a deep‐water setting of the c. 2.4 Ga Turee Creek Group, Western Australia, are reported here. A primarily in situ, deep‐water benthic community preserved in nodular black chert occurs as a tangled network of a variety of long filamentous microfossils, unicells of one size distribution and fine filamentous rosettes, together with relatively large spherical aggregates of cells interpreted as in‐fallen, likely planktonic, forms. Bedded black cherts, in contrast, preserve microfossils primarily within, but also between, rounded clasts of organic material that are coated by thin, convoluted carbonaceous films interpreted as preserved extracellular polymeric substance (EPS). Microfossils preserved within the clasts include a wide range of unicells, both much smaller and larger than those in the nodular black chert, along with relatively short, often degraded filaments, four types of star‐shaped rosettes and umbrella‐like rosettes. Large, complexly branching filamentous microfossils are found between the clasts. The grainstone clasts in the bedded black chert are interpreted as transported from shallower water, and the contained microfossils thus likely represent a phototrophic community. Combined, the two black chert facies provide a snapshot of a microbial ecosystem spanning shallow to deeper‐water environments, and an insight into the diversity of life present during the rise in atmospheric oxygen. The preserved microfossils include two new, distinct morphologies previously unknown from the geological record, as well as a number of microfossils from the bedded black chert that are morphologically similar to—but 400–500 Ma older than—type specimens from the c. 1.88 Ga Gunflint Iron Formation. Thus, the Turee Creek Group microfossil assemblage creates a substantial reference point in the sparse fossil record of the earliest Paleoproterozoic and demonstrates that microbial life diversified quite rapidly after the end of the Archean.     

Native woody vegetation in central Argentina: Classification of Chaco and Espinal forests

Question

What are the composition and spatial patterns of native woody plant communities in the southern Great Chaco and Espinal?

Location

Córdoba Province, central Argentina, an area of ca. 161,000 km².

Methods

We collected 351 geo‐referenced relevés representative of the geographic, topographic and ecological variation of the Chaco and Espinal woody vegetation in central Argentina. The relevés were classified into vegetation types using the hierarchical ISOPAM method. Forest and shrubland types were described on the basis of diagnostic species occurrences and their distribution in relation to environmental factors. A map of the actual vegetation derived from remote‐sensed images (Landsat) and field data was used to describe the current distribution and abundance of the different vegetation types.

Results

The classification of the 351 plots × 837 species matrix revealed two major clusters comprising seven woody vegetation types corresponding to Chaco lowland and mountain forests and shrublands, Espinal forests and edaphic vegetation. The most important gradients in woody vegetation types are related to elevation, temperature and rainfall variables.

Conclusions

Subtropical seasonally dry woody plant communities from the southern extreme of the Great Chaco and Espinal forests were described for the first time based on complete floristic data. Our results show that lowland Chaco native forests, as well as replacement communities, are still present in its southern distribution range and are well distinguishable from other vegetation types such as the Espinal and mountain forests. Overall, extensive Espinal forests have almost disappeared while Chaco vegetation is highly fragmented and degraded.

     

Predicting the cumulative effect of multiple disturbances on seagrass connectivity

The rate of exchange, or connectivity, among populations effects their ability to recover after disturbance events. However, there is limited information on the extent to which populations are connected or how multiple disturbances affect connectivity, especially in coastal and marine ecosystems. We used network analysis and the outputs of a biophysical model to measure potential functional connectivity and predict the impact of multiple disturbances on seagrasses in the central Great Barrier Reef World Heritage Area (GBRWHA), Australia. The seagrass networks were densely connected, indicating that seagrasses are resilient to the random loss of meadows. Our analysis identified discrete meadows that are important sources of seagrass propagules and that serve as stepping stones connecting various different parts of the network. Several of these meadows were close to urban areas or ports and likely to be at risk from coastal development. Deep water meadows were highly connected to coastal meadows and may function as a refuge, but only for non‐foundation species. We evaluated changes to the structure and functioning of the seagrass networks when one or more discrete meadows were removed due to multiple disturbance events. The scale of disturbance required to disconnect the seagrass networks into two or more components was on average >245 km, about half the length of the metapopulation. The densely connected seagrass meadows of the central GBRWHA are not limited by the supply of propagules; therefore, management should focus on improving environmental conditions that support natural seagrass recruitment and recovery processes. Our study provides a new framework for assessing the impact of global change on the connectivity and persistence of coastal and marine ecosystems. Without this knowledge, management actions, including coastal restoration, may prove unnecessary and be unsuccessful.     

放射线引导下经椎间盘入路内脏大小神经毁损术治疗上腹部癌痛的临床分析

目的:观察放射线引导下经椎间盘入路毁损内脏神经治疗上腹部癌痛的疗效及安全性。方法:选择上腹部癌痛患者26例,在放射线引导下经T11~12椎间盘入路穿刺,注射无水乙醇5.0 mL毁损内脏大、小神经,观察穿刺成功率,并记录术前、术后1天、1周、2周、1月、2月的疼痛强度(NRS评分)、生活质量评分(QOL),阿片类药物的用量以及手术不良反应的发生情况。结果:所有患者均穿刺到位,无严重并发症出现。和术前相比,术后各时点的NRS评分、每日吗啡消耗量下降,QOL评分增加(P0.05)。其中,6例患者发生暂时性腹泻,一周内恢复;5例患者出现不同程度的腹背部烧灼感,未经特殊处理24 h后症状消失。结论:在放射线引导下经椎间盘入路毁损内脏神经治疗上腹部癌痛的操作简单,疗效好,可显著提高患者的生活质量,且安全性高。     

Lambertella advenula, a new combination proposed forMoellerodiscus advenulus, new to Japan

Moellerodiscus advenulus, a sclerotiniaceous fungus new to Japan, was collected and its ascospore morphology and cultural characteristics were studied. Ascospores possess previously unreported characters, such as gelatinous polar appendages and a sheath, and become brown and one-septate after discharge, prior to germination. The stromata produced in culture have a thin black rind typical ofLambertella. The taxonomic position ofM. advenulus is discussed, and a new combination,L. advenula, is proposed.     

Temporal variation of energy reserves in mayfly nymphs (Hexagenia spp.) from Lake St Clair and western Lake Erie

1. We analysed changes in energy reserves (lipid and glycogen) and length–weight relationships of burrowing mayflies (Hexagenia spp.) in 1997–99 to compare an established population in Lake St Clair with a recovering population in western Lake Erie of the Laurentian Great Lakes. In addition, we measured changes in water temperature and potential food in both water columns and sediments. 2. Although overall mean values of lipid and glycogen levels of Hexagenia nymphs from Lake St Clair and western Lake Erie were not significantly different, there were differences in seasonal patterns between the two lakes. In Lake St Clair, levels were highest in early spring, declined throughout the year, and reached their lowest levels in fall during all 3 years of study. In contrast, levels in western Lake Erie were lower in spring, increased to a maximum in summer, then declined in fall. Seasonal patterns in length–weight relationships were similar to those for lipid and glycogen. 3. Total lipid as a percentage of dry weight did not increase with developmental stage of nymphs until just prior to metamorphosis and emergence from water. However, the major reserve lipid, triacylglycerols, increased systematically with development stage. In the final stage of development, triacylglycerols declined, probably as a result of energy consumption and its conversion to other biochemical components for metamorphosis and reproduction. 4. Indicators of potential food (algal fluorescence in the water column and chlorophyll a and chlorophyll a/phaeophytin ratio in sediments) suggest that Hexagenia in Lake St Clair have a food source that is benthic based, especially in early spring, whereas in western Lake Erie nymphs have a food source that is water column based and settles to the lake bottom during late spring and summer.     

PHYTOPLANKTON PIGMENTS IN COASTAL LAKE MICHIGAN: DISTRIBUTIONS DURING THE SPRING ISOTHERMAL PERIOD AND RELATION WITH EPISODIC SEDIMENT RESUSPENSION1

Phytoplankton pigment distributions during the spring isothermal periods of 1998 and 1999 and their association with episodic sediment resuspension were characterized in coastal waters of southern Lake Michigan. Total and phylogenetic group chl a concentrations (derived using chemical taxonomy matrix factorization of diagnostic carotenoids) corresponded with assemblage and group biovolumes estimated from microscopic enumeration (P≤ 0.001). Diatoms and cryptophytes dominated assemblages and together typically comprised greater than 85% of relative chl a. Total chl a concentrations and both fucoxanthin·chl a ^{? 1} and alloxanthin·chl a ^{? 1} ratios were similar across depths (P> 0.05), indicating uniform distributions of and photophysiological states for assemblages and diatoms and cryptophytes, respectively, throughout the mixed water column. Total chl a concentrations were not always spatially uniform from near‐shore to offshore waters, with the greatest variability reflecting the influence of tributary inflows upon coastal assemblages. Sediment resuspension strongly influenced water column particle density and light climate; however, total and group chl a concentrations did not correspond with coefficients of K_d and suspended particulate matter concentrations (P> 0.05). The correspondence of both light attenuation and suspended particulate matter concentration with relative diatom chl a (P≤ 0.001) indicated an apparent association between sediment resuspension and diatoms. This, and the negative association (P≤ 0.0001) between relative diatom and cryptophyte chl a, corresponded with the spatial dominance of diatom and cryptophyte chl a in near‐shore and offshore waters, respectively. The presence of viable chl a and fucoxanthin within the surficial sediment layer, established this layer as a potential source of meroplanktonic diatoms for near‐shore assemblages.     

Is speciation of demersal fishes in Lake Tanganyika restrained by physical limnological conditions?

Both Lake Malawi and Lake Victoria have many species of offshore demersal cichlids, most of which are stenotopic. In Lake Tanganyika there are fewer, more eurytopic, demersal species. These differences may be the effect of the physical regimes of the lakes. In Lake Victoria there is no permanent anoxic layer. In both the other lakes, water below 250 m depth is permanently anoxic and the seasonal cycle is dominated by upwelling. In Lake Malawi this is mainly derived from intermediate water containing free oxygen. In Lake Tanganyika upwelling involves hypolimnetic water, which may rise to within 80 m of the surface, causing great short-term changes in oxygen concentration over the depth range 50–250 m. This has inhibited the development of deep water species restricted to narrow depth ranges.