Mid-Holocene palaeoclimatic and palaeohydrological conditions in northeastern European Russia: a multi-proxy study of Lake Vankavad

Mid-Holocene changes in vegetation, palaeohydrology and climate were investigated from the sediments of Lake Vankavad in the northern taiga of the Usa Basin, NE European Russia, through the analysis of pollen, plant macrofossils, Cladocera and diatoms. Lake Vankavad was probably formed at ca. 5000 BP (ca. 5600 cal. BP) and initially it was shallow with a littoral cladoceran fauna. Macrofossil and pollen results suggest that dense Betula-Picea forests grew in the vicinity and the shore was close to the sampling point. At ca. 4600 BP (ca. 5400 cal. BP) the water level rose coincident with the decrease in the density and area of forests, probably caused by cooling climate and accelerated spread of mires. There was also a further rise in the water level at ca. 3500 BP (ca. 3800 cal. BP). The initiation of the lake, followed by two periods of rising water-level, as well as the increase in mire formation, was a consequence of a rise in groundwater level. This probably reflects lower evapotranspiration in a cooling mid-Holocene climate and/or higher precipitation in the lowland area. Also the decreased forest density and area may have contributed to the lower evapotranspiration. It is also possible that permafrost aggradation or changes in peat ecosystems might have affected the hydrological conditions in the area.     

How special are Etendeka mesas? Flora and elevation gradients in an arid landscape in north-west Namibia

Seven mesas (i.e. flat-topped, isolated mountains) and the Grootberg mountain in arid north-west Namibia were investigated with regard to floristic relationships in relation to environmental gradients. Relationships between mesas and their surrounding, species richness and number of mesa specialists were used as measures to explore the influence of elevation on these floristic parameters. Also soil properties were investigated along these elevation gradients. The overall questions were designed to investigate the importance, i.e. ‘special status’, of these mesas in terms of contributing to species diversity and to elucidating ecological processes in this arid landscape.With regard to special floristic status, the tops of mesas supported different plant communities than their surrounding plains, while slopes indicated various levels of intermingling with plain vegetation. Differences between mesas and plains became more pronounced with increasing elevation. There were, however, no clear vegetation belts related to elevation. Plant species richness and number of mesa specialists showed a trend of increasing numbers with elevation, but these trends were statistically poorly supported, largely due to high variability between samples.Do soil gradients and elevation, as two important environmental variables, affect this ‘special’ status? Pronounced soil gradients were evident for many soil properties. These in combination with altitudinal effects of increased moisture and lower temperatures were believed to directly influence plant species composition and richness. The soil gradients may also indicate nutrient flow from the mesas to the surrounding lowlands, a process of ecological importance, particularly should degradation due to over grazing become a problem in the lowland areas.     

祁连山海北高寒草甸地区植物生长期的光合有效辐射特征

分析了祁连山海北高寒草甸地区 1998年植物生长期内光合有效辐射 (PAR)的日、季节变化特征。结果表明 :PAR日变化与太阳总辐射 (Eg)日变化趋势一致 ,表现为单峰型变化过程 ,日总量最大可达 11.7MJ·m-2 左右。植物生长期内的 4月下旬～ 9月中旬季节变化较为复杂 ,雨季来临之前的 4～ 6月较高 ,其它时间较低 ,旬平均最高在 5月达 85 .2 3MJ·m-2 。PAR在Eg中所占的比例 (η)晴天状况下日平均在 0 .36～ 0 .41之间 ,阴天稍高 ,植物生长期内 η的旬平均在 0 .32～ 0 .43之间。分析还表明 ,PAR与Eg日总量具有很好的正相关关系 ,从而可依Eg的变化量来估算PAR。同时计算表明 ,海北高寒草甸地区植物群落对PAR的光能利用率为 0 .5 8%左右     

植物入侵与其它全球变化因子间的相互作用

全示变化包括大气臭氧层的损耗，CO2等温室气体排放增加，气候增暖，土地利用和覆盖变化。生物多样性丧失以及外来种入侵等因子，植物入侵与其它全球性变化因子间有复杂的相互作用；大气CO2浓度增加将导致C3植物比C4植物竞争力更强，低营养生态系统会变得更易入侵，变化的气候条件下，许多种类面临迁移或外来问题，土壤变暖也将使许多休眠植物改变习性，增加紫外辐射将使一些植物的生长和生产力减少。进而会对其竞争和生态过程有间接的影响，CO2浓度升高时硫酸盐的沉积可以增强C3植物的竞争力，较致密的生境破碎化后，一些入侵种可通过边缘进一步向群落内部入侵，增加或降低典型干扰的频率和强度及引入新干扰，能促进外来种的定居和扩散，植物，动物和微生物间的关系改变对植物入侵的速率和效果有明显影响，世界性贸易和运输为生物的入侵提供了条件。     

海水碳酸盐体系缓冲模型在水质预测中的应用

采用二维浅水潮波方程数值模拟了深圳湾及其邻近海域的潮流，在此基础上引入了海水碳酸盐体系的缓冲容量数学模型和二维水质联合模型，进行了电厂海水脱硫冷却水对海水中pH值的影响预测。研究表明，电厂排放的冷却水对海水中pH值的影响面积很小，不会给周围海水水质造成不良影响，几乎不影响深圳湾的水质。     

植物生长调节剂对波吉卵囊藻生长的影响

本文研究了不同浓度的植物生长调节剂，即6－苄氨基嘌呤（6－BA）、2．4－二氯苯氧乙酸（2．4－D）对波吉卵囊藻Oocystis borgei的生长和代谢影响。结果表明：6－BA在0．1－0．5mg.L^-1和2.4-D在0.1-7mg.L^-1的浓度范围内，对波吉卵囊藻的生长、干重、叶绿素a含量、光全作用强度和呼吸作用强度都有一定的促进作用，可作为虾塘波吉卵囊藻定向培育的生长调节剂。6－BA和2．4－D的最佳浓度分别是0.5mg.L^-1和1.5mg.L^-1。     

Spatio-temporal variability in faunal assemblages surrounding the discharge of secondary treated sewage

Macrofaunal assemblages inhabiting the intertidal zone surrounding an input of secondary treated effluent were sampled in order to determine how the pollution impact varied temporally and spatially. Assemblages varied along the pollution gradient formed by the Bolivar Wastewater Treatment Plant outfall in Gulf St Vincent, South Australia. While the abundance of some species did not vary, the abundance of juvenile western king prawns (Melicertus latisulcatus) and blue crabs (Portunus pelagicus) progressively decreased with proximity to the outfall. Species richness and diversity also decreased towards the outfall. An increase in nutrient content in the water adjacent to the outfall is likely to explain these changes. At distances of 4 and 5 km away, species diversity increased and the abundance of M. latisulcatus decreased, possibly due to a change in habitat from sand to seagrass. The occurrence of a storm prior to sampling on one occasion masked the effects of pollution and habitat changes. The results of this study suggest that the disposal of treated effluent into Gulf St Vincent is having a localised effect on the faunal assemblages surrounding the discharge point.     

Spectral detection of stress-related pigments in salt-lake succulent halophytic shrubs

The spectral detection of vegetation pigment concentrations has a high potential value, but it is still underdeveloped, especially for pigments other than chlorophylls. In this study, the seasonal pigment dynamics of two Tecticornia species (samphires; halophytic shrubs) from north-western Australia were correlated with spectral indices that best document the pigment changes over time. Pigment dynamics were assessed by analysing betacyanin, chlorophyll and carotenoid concentrations at plant level and by measuring reflectance at contrasting seasonal dates. Plant reflectance was used to define a new reflectance index that was most sensitive to the seasonal shifts in Tecticornia pigment concentrations. The two Tecticornia species turned from green to red-pinkish for the period March–August 2012 when betacyanins increased almost nine times in both species. Chlorophyll levels showed the opposite pattern to that of betacyanins, whereas carotenoid levels were relatively stable. Normalised difference indices correlated well with betacyanin (r = 0.805, using bands at 600 and 620 nm) and chlorophyll (r = 0.809, using bands at 737 and 726 nm). Using knowledge of chlorophyll concentrations slightly improved the ability of the spectral index to predict betacyanin concentration (r = 0.822 at bands 606 and 620 nm, in the case of chemically determined chlorophyll, r = 0.809 when using remotely sensed chlorophyll). Our results suggest that this new spectral index can reliably detect changes in betacyanin concentrations in vegetation, with potential applications in ecological studies and environmental impact monitoring.     

A Parameterization of Bowen Ratio with Respect to Soil Moisture Availability

The Bowen ratio (B) is impacted by 5 environmental elements: soil moisture availability, m, the ratio of resist-ances between atmosphere and soil pores, ra/rd, atmospheric relative humidity, h, atmospheric stability, ΔT, and environment temperature. These impacts have been investigated over diverse surfaces, including bare soil, free water surface, and vegetation covered land, using an analytical approach. It was concluded that: (a) B is not a continuous function. The singularity exists at the condition αhcb=h, occurring preferably in the following conditions: weak turbulence, stable stratified stability, dry soil, and humid air, where hcb, defined by Eq.(11) is a critical variable. The existence of a singularity makes the dependence of B on the five variables very complicated. The value of B approaches being inversely proportional to m under the conditions m≥mfc (the soil capacity) and / or ra/rd→0. The proportional coefficient changes with season and latitude with relatively high values in winter and over the poles; (b) B is nearly independent of ra/rd during the day. The impact of m on B is much larger as compared to that of ra/rd on B, (c) when h increases, the absolute value of B also increases; (d) over bare soil, when the absolute surface net radiation increases, the absolute value of B will increase. The impact of RN on B is larger at night than during the day, and (e) over plant canopy, the singularity and the dependcies of B on m, ra , and h are modified as compared to that over bare soil. Also (i) during the daytime unstable condition, m exerts an even stronger impact on B, at night, however, B changes are weak in response to the change in m; (ii) the value of B is much more sensitive in response to the changes of turbulent intensity; (iii) the B response to the variation of h over a vegetation covered area is weaker; and (iv) the singularity exists at the condition hcp=h instead of αhcb=h as over bare soil, where hcp is defined by Eq.(49). The formulas derived over bare soil also hold the same when applied to free water bodies as long as they are visualized as a special soil in which the volumetric fraction of soil pore is equal to one and are fully filled with water. Finally, the above discussions, are used to briefly study the impact on the thermally induced mesoscale circulations.     

美国弗蒙特州两种濒危鸟类保护成效研究

本文以美国弗蒙特(Vermont)州濒危鸟类游隼(Falco peregrinus)和潜鸟(Gavia immer)为例,反映鸟类与环境的关系,说明人类活动对环境及野生动物的影响,濒危动物的拯救工作应把环境综合治理放在重要位置。