近期和长远时段内北极生态系统结构受到的影响

生物在物种水平上对全球气候变暖和紫外线B(UV-B)辐射增强的反应受到其群落内其他物种以及生态系统内养分循环的调节,所有的这些反应将会导致生态系统结构的变化.根据高纬度地区坏境因子的可能变化而做的控制试验表明,由夏季变暖而引起苔原植被的变化要小于增加施肥而引起的变化,试验涉及的某些环境因子对北极生态系统的结构有非常强烈地影响,但是这些影响因地区而异,观测结果表明,处于最寒冷地区的植物群落和无脊椎动物群落对全球气候变暖和紫外线B辐射的增强反应最为强烈.尽管微生物量和养分储存量相对稳定,北极无脊椎动物群落还是很可能会对全球变暖产生迅速的反应.试验结果显示,加强紫外线B辐射会改变革兰氏阴性细菌和真菌的群落组成结构,但不会对植物群落的组成产生影响.由夏季气温升高而提高的植物生产力将会控制食物网的动态变化,以苔原植被和亚极地森林植物为基础的食物网中的营养流动会明显地影响到几种优势动物种群数量的周期性波动,在某些年分这些动物的种群数量会达到峰值.小型啮齿动物和食叶昆虫如秋毛虫种群数量的周期性变化则会影响苔原和森林苔原植物的组成结构和多样性,同时也会影响到一些专性捕食者和寄生虫的变化.在暖冬,雪表形成冰壳可能会减少旅鼠的植物食物来源,然而较深的雪也可以使它们免受雪地表面上捕食者对它们的捕食.在芬诺斯堪的亚地区,已有证据表明小型啮齿类动物群落结构和种群动态的显著变化会导致专门以小型啮齿类动物为食物的捕食者的数量减少.气候还可能改变昆虫在白桦森林生态系统中的作用,因为暖冬可以增加这些昆虫卵的成活率,并且扩大其分布范围.此外,在夏季困扰驯鹿的昆虫会由于夏季气候的变暖而扩大其分布范围、增加种群数量并且种群更为活跃;同时在另一方面也会对驯鹿不利,即那些昔日驯鹿/北美驯鹿的避难场所--冰川和未融的成片的雪--在这样温暖的夏季则可能会消失.     

近期和长远时段内北极生态系统功能受到的影响

长期以来,就营养物质和碳循环而言,北极生态系统降低了初级生产力；能量,水和温室气体交换的水平已引起了局部和区域性的小幅度降温.大气CO2中的碳沉积在广袤而寒冷的有机土壤中,冰雪覆盖的低矮植被产生高的反射率,都影响了局部气候.然而,北极生态系统功能的许多方面都对气候变化及其产生的生物多样性影响敏感.当前的北极气候导致了低的有机物质分解速率,因此,尽管有机物和元素输入量较低,但北极生态系统还是趋向于积累有机物和元素,土壤中氮和磷等可利用元素结果成为促进碳固定以及生物量和有机物进一步积累的关键性限制因素.气候变暖可能增加特别是土壤中的碳和元素的周转,起初可能导致元素的丢失,但最后会慢慢的恢复.在北极生态系统中,单个物种和物种多样性已经明显地影响了元素的输入和滞留,另一方面,从长远来看,尽管CO2和紫外线增加对植物组织化学、分解和氮固定的影响可能变得重要,但对整个生态系统来说,影响可能很小.碳循环的示踪气体主要形式是CO2和CH4,大多数碳以CO2的形式损失,这些CO2是由植物和土壤生物产生.来自潮湿苔原生态系统以CH4形式释放的碳大约是CO2形式的5％,而且在没有任何其他变化的情况下,对变暖作出响应.冬天过程和植物类型也影响CH4释放和能量在生物圈和大气之间的交换,因为反射率从冬末到夏天存在很大的变化,在冬末,雪反射了入射的大部分光线,在夏天,生态系统吸收了入射的大部分光线,所以在所有的陆地生态系统中,北极生态系统在能量交换方面表现出巨大的季节性变化.植被深刻地影响北极生态系统水和能量交换.在冰雪覆盖期间,反射率从苔原、森林苔原、落叶林、常绿林依次降低.灌木和树增加了雪的深度,反过来又使冬天的土壤温度增加,因此,由气候变化而引起的未来植被方面的变化很可能深远地改变区域的气候.     

The earliest record of birch mice from the Early Miocene Nei Mongol,China

The earliest species of birch mouse, Sicista primus sp. nov., was recovered from the 17-Ma-old (Early Miocene) Gashunyinadege locality, central Nei Mongol, China. It is ~9 Ma older than the previous first appearance datum of Sicista in Eurasia. This study indicates that North American Macrognathomys is a synonym of Eurasian Sicista, having 12 shared dental characters. As a result, the biogeography of dipodids indicates that Asian Sicista dispersed to North America as opposed to the hypothesis that Sicista originated from the North American clade. Sicista is one of the few extant rodent genera that originated as early as the Early Miocene.     

Circumpolar status of Arctic ptarmigan: Population dynamics and trends

Rock ptarmigan (Lagopus muta) and willow ptarmigan (L. lagopus) are Arctic birds with a circumpolar distribution but there is limited knowledge about their status and trends across their circumpolar distribution. Here, we compiled information from 90 ptarmigan study sites from 7 Arctic countries, where almost half of the sites are still monitored. Rock ptarmigan showed an overall negative trend on Iceland and Greenland, while Svalbard and Newfoundland had positive trends, and no significant trends in Alaska. For willow ptarmigan, there was a negative trend in mid-Sweden and eastern Russia, while northern Fennoscandia, North America and Newfoundland had no significant trends. Both species displayed some periods with population cycles (short 3–6 years and long 9–12 years), but cyclicity changed through time for both species. We propose that simple, cost-efficient systematic surveys that capture the main feature of ptarmigan population dynamics can form the basis for citizen science efforts in order to fill knowledge gaps for the many regions that lack systematic ptarmigan monitoring programs.

     

Aerosol formation yields from the reaction of catechol with ozone

The formation of secondary organic aerosol from the gas-phase reaction of catechol (1,2-dihydroxybenzene) with ozone has been studied in two smog chambers. Aerosol production was monitored using a scanning mobility particle sizer and loss of the precursor was determined by gas chromatography and infrared spectroscopy, whilst ozone concentrations were measured using a UV photometric analyzer. The overall organic aerosol yield (Y) was determined as the ratio of the suspended aerosol mass corrected for wall losses (M_o) to the total reacted catechol concentrations, assuming a particle density of 1.4 g cm^?3. Analysis of the data clearly shows that Y is a strong function of M_o and that secondary organic aerosol formation can be expressed by a one-product gas–particle partitioning absorption model. The aerosol formation is affected by the initial catechol concentration, which leads to aerosol yields ranging from 17% to 86%. The results of this work are compared to similar studies reported in the literature.     

Application of Adjoint Approach to Oil Spill Problems

Adjoint method is applied to various oil spill problems. A three-dimensional model for describing the dispersion of a quasi-passive substance (a pollutant or a nutrient) and its adjoint model are considered in a limited sea region. Direct and adjoint estimates are used to get dual (equivalent) estimates of the mean concentration of the substance in important zones of the region. The role of dual estimates is illustrated with a few examples. They include such oil spill problems as the search of the most dangerous point of the oil tanker route, the oil dispersion with a climatic velocity, and the dependence of the oil concentration estimates on the oil spill rate. One more example is the application of optimal bioremediation strategy for cleaning a few zones polluted by oil. In this case, instead of oil, the model describes the dispersion of a nutrient released to marine environment. Balanced, unconditionally stable second-order finite-difference schemes based on the splitting method for the solution of the dispersion model and its adjoint are suggested. The main and adjoint difference schemes are compatible in the sense that at every fractional step of the splitting algorithm, the one-dimensional split operators of both schemes satisfy a discrete form of Lagrange identity. In the special unforced and non-dissipative case, each scheme has two conservation laws. Every split one-dimensional problem is solved by Thomas’ factorization method.     

Multivariate analyses of the effect of an urban wastewater treatment plant on spatial and temporal variation of water quality and nutrient distribution of a tropical mid-order river

Freshwater resources are increasingly scarce due to human activities, and the understanding of water quality variations at different spatial and temporal scales is necessary for adequate management. Here, we analyze the hypotheses that (1) the presence of a wastewater treatment plant (WWTP) and (2) a polluted tributary that drains downstream from the WWTP change the spatial patterns of physicochemical variables (pH, turbidity, dissolved oxygen, and electrical conductivity) and nutrient concentrations (reactive soluble phosphorus, total phosphorus, nitrogen series, total nitrogen, and total dissolved carbon) along a mid-order river in SE Brazil and that these effects depend on rainfall regime. Six study sites were sampled along almost 4 years to evaluate the impacts of human activities, including sites upstream (1–3) and downstream (5–6) from the WWTP. The impacts were observed presenting an increasing trend from the source (site 1) towards Água Quente stream (site 4, the polluted tributary), with signs of attenuation at site 5 (downstream from both WWTP and site 4) and the river mouth (site 6). Input of nutrients by rural and urban runoff was observed mainly at sites 2 and 3, respectively. At sites 4 and 5, the inputs of both untreated and treated wastewaters increased nutrient concentrations and changed physicochemical variables, with significant impacts to Monjolinho River. Seasonal variations in the measured values were also observed, in agreement with the pluviometric indexes of the region. Univariate analyses suggested no effect of the WWTP for most variables, with continued impacts at sites downstream, but non-parametric multivariate analysis indicated that these sites were recovering to chemical characteristics similar to upstream sites, apparently due to autodepuration. Therefore, multivariate methods that allow rigorous tests of multifactor hypotheses can greatly contribute to determine effects of both point and non-point sources in river systems, thus contributing to freshwater monitoring and management.     

Biodegradation of heptachlor and heptachlor epoxide-contaminated soils by white-rot fungal inocula

The ability of certain white-rot fungi (WRF) inocula to transform heptachlor and heptachlor epoxide and its application in artificially contaminated soil were investigated. Fungal inoculum of Pleurotus ostreatus eliminated approximately 89 % of heptachlor after 28 days of incubation, and chlordene was detected as the primary metabolite. The fungal inoculum of Pleurotus ostreatus had the highest ability to degrade heptachlor epoxide; approximately 32 % were degraded after 28 days of incubation, and heptachlor diol was detected as the metabolite product. Because Pleurotus ostreatus transformed heptachlor into a less toxic metabolite and could also effectively degrade heptachlor epoxide, it was then selected to be applied to artificially contaminated soil. The spent mushroom waste (SMW) of Pleurotus ostreatus degraded heptachlor and heptachlor epoxide by approximately 91 and 26 %, respectively, over 28 days. This finding indicated that Pleurotus ostreatus SMW could be used to bioremediate heptachlor- and heptachlor epoxide-contaminated environments.     

Effects of ozone on growth, yield and leaf gas exchange rates of two Bangladeshi cultivars of wheat (Triticum aestivum L.)

To clarify the effects of O₃ on crop plants cultivated in Bangladesh, two Bangladeshi wheat cultivars (Sufi and Bijoy) were grown in plastic boxes filled with Andisol and exposed daily to charcoal-filtered air or O₃ at 60 and 100 nl l⁻¹ (10:00-17:00) from 13 March to 4 June 2008. The whole-plant dry mass and grain yield per plant of the two cultivars at the final harvest were significantly reduced by the exposure to O₃. Although there was no significant effect of O₃ on stomatal diffusive conductance to H₂O of flag leaf, net photosynthetic rate of the leaf was significantly reduced by the exposure to O_3. The sensitivity of growth, yield, yield components and leaf gas exchange rates to O₃ was not significantly different between the two cultivars. The results obtained in the present study suggest that ambient levels of O₃ may detrimentally affect wheat production in Bangladesh.     

Zinc tolerance and uptake by <Emphasis Type="Italic">Arabidopsis halleri ssp. gemmifera</Emphasis> grown in nutrient solution

Background, aim, and scope  

Zinc is an essential micronutrient element but its concentrations found in contaminated soils frequently exceed those required by the plant and soil organisms, and thus create danger to animal and human health. Phytoremediation is a technique, often employed in remediation of contaminated soils, which aims to remove heavy metals or other contaminants from soils or waters using plants. Arabidopsis (A.) halleri ssp. gemmifera is a plant recently found to be grown vigorously in heavy metal contaminated areas of Japan and it contained remarkably high amount of heavy metals in its shoots. However, the magnitude of Zn accumulation and tolerance in A. halleri ssp. gemmifera need to be investigated for its use as a phytoremediation plant.