Changes in amphipod (Crustacea) assemblages associated with shallow-water algal habitats invaded by Caulerpa racemosa var. cylindracea in the western Mediterranean Sea

The effects of the invasive species Caulerpa racemosa var. cylindracea (hereafter C. racemosa) on amphipod assemblages associated with shallow-water rocky habitats were studied. Two habitats located along the SE Iberian Peninsula were compared; invaded and non-invaded. The results showed that growth of C. racemosa affects habitat structure, influencing the species composition and biomass of macroalgae, and detritus accumulation. In turn, such changes in habitat features affected the associated amphipod assemblages with different ecological requirements. However, the species richness of amphipods was relatively high in both habitats, while the species composition of amphipods changed completely. For example, some species such as Ampithoe ramondi and Hyale schmidti did not colonize invaded habitats, while others such as Apocorophium acutum were favoured by the spread of C. racemosa. Habitat invasion by C. racemosa can have an important influence on biotic assemblages, modifying both habitat structure and the associated fauna, with unknown effects on the overall ecosystem.     

浑善达克沙地天然沙地榆种内竞争研究

采用逐步扩大范围的方法确定影响沙地榆对象木的最佳竞争范围,利用Hegyi提出的单木竞争指数模型,对浑善达克沙地天然沙地榆种内竞争强度进行定量分析。结果表明,在沙地榆群落中,对象木的最佳竞争距离为8 m,沙地榆种内竞争强度随着植株径级的增大而逐渐减小。竞争强度与对象木胸径服从幂函数关系,从模型预测结果可知,当沙地榆胸径在30 cm以内时,竞争强度变化显著;当沙地榆胸径达30 cm 以上时,竞争强度变化很小。采用逐步扩大范围的方法能有效地确定竞争木范围,较好地反应浑善达克沙地天然沙地榆种内竞争关系。应在沙地榆胸径达30 cm前采取适当的人工疏伐措施来促进植株生长和增强生态系统的稳定性。     

Alien cyanobacteria Anabaena bergii var. limnetica Couté et Preisig from Lithuania: Some aspects of taxonomy, ecology and distribution

The anthropogenic eutrophication of surface waters and the global climate warming promoted some bloom-forming tropical cyanobacteria, including Anabaena, distribution northwards. Anabaena bergii var. limnetica was for the first time recorded in Lithuania from the hypertrophic Lake Gineitišk?s in 2008. It developed when the water temperature reached its annual maximum (July–August); its highest biomass (0.26 mg L⁻¹) was reached at the end of July. Akinetes formation started in the middle of August. The morphological variability of A. bergii var. limnetica morphospecies is presented. The morphological, ecological differences and distribution of A. bergii var. limnetica and the related morphospecies A. bergii, A. bergii f. minor, Anabaena minderi are discussed.     

黑龙江野鲤(Cyprinus haematopteru)与建鲤(Cyprinus carpio var. Jian)正反交与自交子代消化酶活力及其分布比较分析

在网箱养殖 45 天后, 采用比较分析黑龙江野鲤与建鲤正反交与自交子代消化酶活力的方法, 研究由杂交引起的遗传背景改变对消化酶活力及其分布的影响。 结果表明, 两杂交群体肝胰腺蛋白酶活力显著高于建鲤自交子代, 后肠则显著低于后者, 后肠脂肪酶活力显著高于黑龙江野鲤自交子代; 黑龙江野鲤♂×建鲤♀子代各消化器官淀粉酶活力均显著高于两自交群体。两杂交群体除前、中肠淀粉酶活力差异显著度与建鲤自交子代不同外, 3 种消化酶活力分布及不同器官间的差异程度和两自交群体均相同; 四个群体脂肪酶和淀粉酶活力在前、中肠及肝胰腺均表现出互补现象, 后肠均有较高活力不互补。     

云南哀牢山西麓季风常绿阔叶林及思茅松林的群落学特征

在云南哀牢山西麓川河河谷残存有较大面积的季风常绿阔叶林,其周围分布着思茅松林.采用典型取样法,对季风常绿阔叶林及思茅松林的物种组成与群落结构进行了调查和分析,结果表明:季风常绿阔叶林乔木层的优势种主要是红木荷(Schima wallichii)、高山栲(Castanopsis delavayi)、密花树(Rapanea neriifolia),而思茅松成熟林以思茅松(Pinus kesiya var.langbianensis)为绝对优势.在季风常绿阔叶林的29株样树树干上共调查到附生植物共36种,但在思茅松林中几乎找不到附生植物.季风常绿阔叶林和思茅松成熟林的香农-威纳多样性指数分别为3.32和1.70;相对于思茅松林,季风常绿阔叶林物种组成和群落结构都更复杂,具有较高的生物多样性和稳定性.由于该区域的季风常绿阔叶林受到了较为严重的人为干扰和破坏,因此,需要进一步加强对山地森林植被的保护与管理,尽量减少人为干扰,并采取适当的人工抚育措施,促进该区山地森林资源的保护和恢复.     

樟子松固沙林土壤碳截存及土壤呼吸对干湿变化的响应

 在科尔沁沙地测定分析了流动沙丘栽植樟子松林23 a后的土壤碳截存作用,以及林地和流动沙丘土壤呼吸对干湿变化的响应。结果表明:①流动沙丘造林后土壤容重减小,土壤颗粒中极细沙和黏粉粒含量显著增加;②樟子松林地0~5 cm和5~15 cm层土壤有机碳截存量分别为221.8 g·m-2和113.9 g·m-2,截存速率分别为9.64 g·m-2·a-1和4.95 g·m-2·a-1;CaCO3-C截存量分别为4.0 g·m-2和2.5 g·m-2, 截存速率分别为0.17 g·m-2·a-1和0.11 g·m-2·a-1;③干旱条件下土壤呼吸随气温的升高呈现指数减小;无论是干旱还是降雨后,林地土壤呼吸速率均显著高于流动沙丘;④降雨刺激后土壤呼吸显著增加,林地增加的幅度显著高于流动沙丘;林地地表凋落物去除后土壤呼吸速率下降,并且在降雨后下降更为明显。     

Estimation of evapotranspiration and its components from an apple orchard in northwest China using sap flow and water balance methods

Field experiments were conducted to investigate the effects of leaf area index and soil moisture content on evapotranspiration and its components within an apple orchard in northwest China for 2 years. Evapotranspiration in the non‐rainfall period was estimated using two approaches: the soil water balance method based on tube‐type time‐domain reflection measurements, and sap flow plus micro‐lysimeter methods. The two methods were in good agreement, with differences usually less than 10%. The components of evapotranspiration varied with canopy development. During spring and autumn, soil evaporation was dominating as result of low leaf area index. In summer, plant transpiration became significant, with an average transpiration to evapotranspiration ratio of 0·87. The crop coefficient K_c showed a strong linear dependence on leaf area index. The water stress coefficient K_s was around 1·0 when soil moisture was above 23% and started to decrease linearly after that. This study demonstrates that prediction of evapotranspiration in apple orchards can be made using the Food and Agriculture Organization's crop coefficient method from commonly available meteorological data in the area. Copyright © 2006 John Wiley & Sons, Ltd.     

Study on the Free Radical Scavenging Activity of Sea Cucumber （Paracaudina chinens vat.） Gelatin Hydrolysate

Gelatin from the sea cucumber （Paracaudina chinens var.） was hydrolyzed by bromelain and the hydrolysate was found to have a high free radical scavenging activity. The hydrolysate was fractionated through an ultrafiltration membrane with 5 kDa molecular weight cutoff （MWCO）. The portion （less than 5 kDa） was further separated by Sephadex G-25. The active peak was collected and assayed for free radical scavenging activity. The scavenging rates for superoxide anion radicals （O2·^-） and hydroxyl radicals （·OH） of the fraction with the highest activity were 29.02% and 75.41%, respectively. A rabbit liver mitochondrial free radical damage model was adopted to study the free radical scavenging activity of the fraction. The results showed that the sea cucumber gelatin hydrolysate can prevent the damage of rabbit liver and mitochondria.     

浑善达克沙地南缘榆树种群的大小结构和邻体格局

 浑善达克沙地作为京津地区沙尘暴的重要沙源地引起了生态学界的广泛关注。榆树是浑善达克沙地的优势种,榆树疏林在浑善达克沙地成缀块状分布,对于该区域生态系统的整体性和多样性维持以及防风固沙等方面具有重要意义。研究浑善达克沙地南缘榆树种群的大小结构和邻体格局的结果显示:榆树种群的平均胸径为25.40 cm,最小胸径为6.37 cm,缺乏幼树,种群更新不良。榆树邻体格局研究显示:榆树种群呈丛分布,取样个体到最近邻体距离的平均值是7.13 m,在4 m以下的占55.0%,10 m以下的占72.6%。两个个体互为最近邻体的榆树占了71.4%,具有成对现象,成对现象对榆树有明显影响。最后对榆树疏林存在的问题及保护措施等进行了探讨。     

Algal populations and characteristics of oxygen exchange of effluent samples from a facultative oxidation pond

Algal populations in a facultative oxidation pond were monitored over a 12 month period. The relationships between cell counts of individual species and characteristics of oxygen exchange, determined from changes in dissolved oxygen concentration in response to varying light flux density, were investigated by correlation analysis. These measurements were made in the laboratory at a constant temperature (15°C). Microalgae (Chlorella spp.) usually made up at least 80% of the total cell numbers, whereas Euglena acus, E. gracilis, and Ankistrodesmus falcatus var. acicularis separately made up less than 10% of the total counts. However, when cell volumes were considered, E. acus usually made the greatest contribution, and this species accounted for 86% (=r²) of the variation in total cell volume. The detectable pigment concentration in the water was closely related to the numbers of E. acus present (r=0.81, P <0.001) but not to the numbers of microalgae (r=0.00). Cell counts of E. acus were highly correlated with the light saturated rate of net oxygen production (P_{n max}) and to the rate under limiting light supply (6) because of the high detectable pigment contribution from this species. It was calculated that E. acus contributed, on average, about 44% of the total rate of net oxygen production, whereas the proportion attributed to the microalgae was 8%.