GPS scintillation studies in the arctic region during the first winter-phase 2008 Indian Arctic Expedition

We present the results of scintillation studies based on the data obtained during the first winter-phase Indian Arctic Expedition in March 2008 at the Indian Himadri Station, Ny-Ålesund (78.9°N, 11.9°E), in the vicinity of the daytime cusp and under the nightside polar cap. A global-positioning-system ionospheric scintillation and TEC monitor (GISTM) receiver (model GSV4004A) was used to record scintillations and the total electron content (TEC). The polar ionosphere is more sensitive to phase than to amplitude scintillations. Occurrence of amplitude scintillation is confined to well-defined regions, while phase scintillation shows a strong characterization both in magnetic latitude and magnetic local time. Occurrence of amplitude and phase scintillation increases during disturbed compared with quiet days. During disturbed days, the phase-scintillation region is displaced towards lower latitudes, following the auroral oval. The observed noon peak in scintillation occurrence may indicate that the irregularities that generate scintillation are caused by precipitation in the daytime cusp/cleft region. A significant enhancement of the TEC and the rate of change of the TEC index (ROTI) signified transits of polar-cap patches across different satellite trajectories during geomagnetic storms. We found that patches are most likely to occur when IMF Bz is southward and/or K_p > 4. Loss of signal lock was more for the L2 signal than for L1, and shows a maximum in the morning sector. Positional errors tend to increase during disturbed conditions.     

Fruit polymorphism in ephemeral species of Namaqualand: IV. Growth analyses of plants cultivated from the dimorphic diaspores

Growth analyses were conducted on two polymorphic annual species, Dimorphotheca sinuata and Arctotis fastuosa of Namaqualand, Republic of South Africa. Plants cultivated from disc diaspores of D. sinuata produced significantly more inflorescences, produced bigger mature plants and allocated more biomass to reproduction than plants cultivated from ray diaspores. Plants of both D. sinuata and A. fastuosa growing on less disturbed sites in the field allocated more biomass to reproduction than plants growing on more disturbed sites. Reproductive allocation of A. fastuosa increased with a decrease in plant size, whereas reproductive allocation was not affected by plant size in the case of D. sinuata.     

Structure and functioning of soil zoocenoses of taiga geosystems of the Lena-Angara plateau

A unified methodological approach was used to study the soil zoocenoses of uneven-age industrial areas of the Kovykta gas and condensate field. Regeneration of the soil-biotic block is characterized by sequential changes in quantitative characteristics, and in the taxonomic and functional structure of invertebrate communities. The study revealed distinguishing characteristics of the progressive successions of drastically disturbed mountain-taiga geosystems, and the factors that are responsible for the direction and duration of the individual successions.     

新疆沙冬青叶片蛋白质的双向电泳技术研究

提取新疆沙冬青叶片中蛋白质受到脂类、酚类等次生代谢产物的干扰,针对这种现象,进行了组分提取优化方法和双向电泳技术的改进。实验分析表明,用乙醚淋洗完整叶片,50 mmol·L-1 Tris-HCl缓冲液,上样量240 μg（7 cm胶条）,考马斯亮蓝染色等方法可很大程度增加提取可溶性蛋白含量,结合丙酮-三氯乙酸的沉降,可较完整地提取蛋白质组。     

Effects of galvanic distortion on magnetotelluric data over a three-dimensional regional structure

Although the galvanic distortion due to local, near-surface inhomogeneities is frequency-independent, its effect on the magnetotelluric data becomes, in a 3-D structure, frequency-dependent. Therefore, both the apparent resistivity and the phase responses are disturbed, and a correction should be carried out prior to the 3-D interpretation in order to retrieve the 3-D regional impedance tensor. In many cases, the structure is 2-D for depths corresponding to a first range of periods and 3-D for longer periods (called 2-D/3-D). For these cases, a simple method which allows us to retrieve the 3-D regional impedance tensor (except the static shift) is presented. The method proposed uses the Groom & Bailey decomposition of the distortion matrix for the short periods. Three examples are presented: two using synthetic data and one employing real data. These examples show the effect of the galvanic distortion over a regional 2-D/3-D model and the retrieval of the regional transfer functions from the distorted ones.     

COMPUTER-ASSISTED TERRAIN STRATIFICATION

Terrain influences many ecological processes. Therefore, ecologists must consider terrain effects in sampling designs. Incomplete information on the ecological role of terrain, however, makes it difficult to account for terrain variability in sample designs. As a partial solution, we introduce a protocol that automatically stratifies complex terrain. This stratification method uses image-processing techniques to cluster digital images of slope, elevation, and aspect into homogeneous groupings. The technique is demonstrated for a stratification of complex terrain disturbed by a large forest fire. By identifying terrain complexity at several spatial resolutions, we were able to place transects that sample terrain variability and fire severity representatively across a controlled range of scales. [Key words: terrain, stratification, image processing, sample design.]     

微生物结皮对两种一年生植物种子萌发和出苗的影响

在温室中对两种一年生植物的种子在微生物结皮和流沙对照上的萌发和出苗状况进行了实验.结果表明:在湿润和干燥状况下,苔藓结皮和藻结皮对种子萌发和出苗状况的影响,完整的和破坏的苔藓结皮和藻结皮对种子萌发和出苗状况的影响,总的来说雾冰藜(Bassia dasyphlla)在完整的苔藓结皮和破坏的两种结皮中出苗率均较高.完整致密的藻结皮能阻止雾冰藜的根接触土壤从而对其出苗设置了物理屏障.小种子植物小画眉草(Eragrostics poaeoides)因其种子较大,种子植物有相对大的土壤接触面积和具有特殊的结构须根,从而较容易克服结皮造成的物理屏障,穿透完整致密的结皮层而到达土壤.在破坏的微生物结皮中小画眉的出苗率略有降低.水分处理仅对雾冰藜的出苗有显著影响.在湿润处理下雾冰藜的出苗率要高于在干燥处理下的.因此,自然状况下年降雨量和分配状况的差异可能会影响这两种植物每年幼苗出苗率的差异,进而会影响到这两个种群在人工固沙区分布格局的差异.     

Diatom-inferred palaeoenvironmental changes of a Pliocene lake disturbed by volcanic activity

Lake development in geologically active basins is a complex phenomenon as shown by the bed of the Pliocene Tlaxcala paleolake disturbed by volcanic eruptions in central Mexico. A 5-m layered freshwater diatomite outcrop section shows volcanic ashes throughout a bottom Stephanodiscus zone up to a more recent Aulacoseira zone. A 0.5-m transition region begins with an abrupt decrease in volcanic inputs and ends with a shift to Aulacoseira solida (Eulenstein) Krammer. Sediment analysis points to a shallow eutrophic lake in the bottom zone undergoing a transition to higher water volume leading to a threshold depth for the species shift. The lake was apparently deeper and mesotrophic thereafter. A common interpretation is to attribute such a volume change to a moisture increase. However, evidence of geological activity, mainly volcanism and faulting, suggests that it could have also been rooted in geomorphological changes of the lake basin.     

Ecological patterns and sustainability of freshwater swamp forest ecosystems: assessing climate and disturbance interactions

Species composition and factors that control the distribution of freshwater swamp forests in West Africa are largely unknown. To achieve this, 24, one‐hectare forest plots were established to assess the tree species (DBH ≥ 10 cm) distribution across the ecosystem. A total of 138 species within 100 genera and 41 families were distributed across the forest plots and 47 species were identified as indicator species. These indicator species were used to constrain the species‐environmental categories across three broad habitat types: the disturbed freshwater zone, the mangrove‐freshwater transition zone and the intact freshwater zone. While 40 species are associated with one of the three forest categories, seven of them coexisted in disturbed and mangrove‐freshwater zones. Disturbance (local factors) was identified as the most important determinant of the species distribution followed by the climatic factors. Future climate predictions for the locations are quite variable and suggest that some species may be non‐viable as the ecosystem's composition may alter. While the indicator species provides insights on the species‐environment relationships, and is useful for informing forest conservation and planning, their tendency to continually co‐exist with others and provide vital functions is dependent on how sustainably the people use them.     

Structural-dynamical analysis of the state of the biota of soils in urbanized geosystems (Exemplified by the City of Sayanogorsk)

We report the results from investigating the ecological state of the urbanized geosystems in the city of Sayanogorsk. A comparative analysis is made of the structure of zoocenoses against the natural and anthropogenically disturbed soils predominating in the region. We examine the transformation conditions for soil cover and the ecologically important factors influencing the state of soil-biotic communities. The study revealed a negative influence of urban pressure on the population and biomass of invertebrate animals and demonstrated the possibilities of using the structure and quantitative characteristics of zoocenoses in biodiagnostics of changes of steppe geosystems under the influence of anthropogenic factors.     

国际湿地保护策略及模式

没有湿地就没有水,湿地是地球生态系统的重要组成部分,因此引起世界各国的普遍重视和保护。根据国外湿地保护的经验教训,热带雨林的保护,国际生态环境保护策略模式,提出因地制宜的适合本国国情的保护措施和保护策略,以及制定有关的、系统性的法律、法规,以便操作掌握。探讨了我国湿地的现状,为保护湿地,挽救生态环境危机的紧迫而有效的措施和制定有关政策、规划;提出了保护湿地的原则意见。     

基于树轮地貌学的山洪研究进展

山洪是中国主要的自然灾害之一,严重威胁山区人民生命财产与工程建设安全。针对山洪已发展了多种多样的研究手段,但多集中于过去几十年的时间段内。树轮地貌学方法作为研究历史山洪事件的有效手段之一,在世界范围内被广泛应用。利用树轮中的生长干扰信息,可以对山洪事件进行精确定年,重建无记录或少记录地区内山洪发生的频率、大小和空间分布特征等,根据伤疤的高度或应用水力模型则可以定量重建山洪的流量大小。随着树轮地貌学方法和技术的逐渐成熟,研究趋向于探讨山洪的驱动机制、更大空间尺度山洪的规律性等,具有广阔的应用前景,但是基于树轮的山洪研究工作在国内还未见报道。论文对树轮地貌学应用于山洪研究的发展过程进行了系统回顾,对研究进展进行了简要概述,最后讨论该研究领域的潜力及局限性,以期为在国内进一步开展相关工作提供参考信息。     

Evolution of disturbed oak woodlands: the case of Mexico City's western forest reserve

Mexico City is the largest city in population and area in the world. In the last 30 years it has expanded its area westwards to include the mountains of the Sierra de las Cruces. These mountains contain the nearest forest reserve for the citizens of Mexico City. Deforestation and severe ecological degradation resulting from the destruction of the natural environment; air, water and soil pollution; and hydrological and geomorphological imbalances, limit the capacity of these areas to support forest regeneration. This study focuses on the geo-ecology of the climax oak woodlands found in the Sierra de las Cruces. Based on morpho-structural evidence, bioclimatic type, degree of human intervention and general geo-ecological considerations, three territorial systems have been differentiated in which the oak woodlands exist in different climax facies: a) oak woodlands developed in very humid and cool environments located on low mountain slopes; b) disturbed oak woodlands developed in humid and cool environments located on high piedmonts; and c) highly disturbed oak woodlands developed in subhumid and temperate environments, located on low piedmonts. A comparative study of the content, structure and functional relationships of the secondary facies associated with these climax communities, allowed conclusions to be drawn on the way oak woodlands respond to human intervention, and the risky situations to which these communities are subjected, particularly the most sensitive facies that deserve immediate protection.     

Floods,drought, and seed mass of riparian plant species

Plant communities in dryland riparian ecosystems are influenced by flood disturbance and water availability. As global climate change alters stream flow regimes, there is increasing need to understand which traits allow plant species to persist under increased stress and disturbance. Small seed mass is part of a strategy that adapts for disturbance, but the role of seed mass as an adaptation for drought is less well documented. For dryland riparian plant communities, we asked, does seed mass vary with water availability and flood frequency? We compared community seed mass between sites that vary in flow permanence (longitudinal water gradient) and between hydrogeomorphic surfaces within sites (lateral gradients of moisture and disturbance). Using data from four rivers in Arizona, we contrasted seed mass between plant groups. We found community seed mass to be greater at sites with ephemeral than perennial flow, and to increase laterally from wet, frequently-flooded channel edges to dry, less disturbed terraces. Seed mass varied by moisture group (smallest for hydroriparian species) and by disturbance group (smallest for disturbance species), and showed a trend for being greater in introduced species. We conclude that small seed mass is independently associated with wet and disturbed conditions in dryland riparian ecosystems.     

Comparison of Methods for Evaluating the Forage-livestock Balance of Alpine Grasslands on the Northern Tibetan Plateau

Livestock grazing is one of primary way to use grasslands throughout the world, and the forage-livestock balance of grasslands is a core issue determining animal husbandry sustainability. However, there are few methods for assessing the forage-livestock balance and none of those consider the dynamics of external abiotic factors that influence forage yields. In this study, we combine long-term field observations with remote sensing data and meteorological records of temperature and precipitation to quantify the impacts of climate change and human activities on the forage-livestock balance of alpine grasslands on the northern Tibetan Plateau for the years 2000 to 2016. We developed two methods: one is statical method based on equilibrium theory and the other is dynamic method based on non-equilibrium theory. We also examined the uncertainties and shortcomings of using these two methods as a basis for formulating policies for sustainable grassland management. Our results from the statical method showed severe overgrazing in the grasslands of all counties observed except Nyima (including Shuanghu) for the entire period from 2000 to 2016. In contrast, the results from the dynamic method showed overgrazing in only eight years of the study period 2000-2016, while in the other nine years alpine grasslands throughout the northern Tibetan Plateau were less grazed and had forage surpluses. Additionally, the dynamic method found that the alpine grasslands of counties in the northeastern and southwestern areas of the northern Tibetan Plateau were overgrazed, and that alpine grasslands in the central area of the plateau were less grazed with forage surpluses. The latter finding is consistent with field surveys. Therefore, we suggest that the dynamic method is more appropriate for assessment of forage-livestock management efforts in alpine grasslands on the northern Tibetan Plateau. However, the statical method is still recommended for assessments of alpine grasslands profoundly disturbed by irrational human activities.     

Fluvial sediment transport and deposition following the 1991 eruption of Mount Pinatubo

The 1991 eruption of Mount Pinatubo generated extreme sediment yields from watersheds heavily impacted by pyroclastic flows. Bedload sampling in the Pasig–Potrero River, one of the most heavily impacted rivers, revealed negligible critical shear stress and very high transport rates that reflected an essentially unlimited sediment supply and the enhanced mobility of particles moving over a smooth, fine-grained bed. Dimensionless bedload transport rates in the Pasig–Potrero River differed substantially from those previously reported for rivers in temperate regions for the same dimensionless shear stress, but were similar to rates identified in rivers on other volcanoes and ephemeral streams in arid environments. The similarity between volcanically disturbed and arid rivers appears to arise from the lack of an armored bed surface due to very high relative sediment supply; in arid rivers, this is attributed to a flashy hydrograph, whereas volcanically disturbed rivers lack armoring due to sustained high rates of sediment delivery. This work suggests that the increases in sediment supply accompanying massive disturbance induce morphologic and hydrologic changes that temporarily enhance transport efficiency until the watershed recovers and sediment supply is reduced.     

荒漠草原区风力发电场建设前后的植被变化

调查了甘肃景泰荒漠草原区一处风电场基础设施建设和运行对植被的影响。结果表明:荒漠草原区百兆瓦级风力发电场建设造成直接植被生产力损失量为6.79 g·m^-2·a^-1,间接植被生产力损失量为91.43 g·m^-2·a^-1。随着扰动程度增加,物种丰富度降低,均匀度减小。在工程运行后,经历近10 a的自然恢复,核心扰动区虽然物种单一,但植被生产力是次级扰动区的两倍以上,为间接扰动区和未扰动区的50%和33%左右;而间接扰动区植被生产力仅为未扰动区的50%。总体上,风电工程扰动对区域植被的影响,不仅在于建设期对局地群落植被生产力的完全丧失,更重要的是在运行期间对周边大面积间接影响区群落植被生产力的大幅度降低,而且这种影响是长期和持续性的。     

数字山地垂直带谱及其体系的探索

本文总结了传统山地垂直带研究的脉络及存在的问题；构建了山地垂直带谱数据结构，实现了垂直带谱数字化与可视化；提出了垂直带谱的三级体系：以基带区分一级带谱，以特征垂直带区分二级带谱，以垂直带组合结构、优势垂直带及垂直高度及宽度区分三级带谱；归纳出垂直带谱5种生态类型：1.与区域气候相联系的顶极带谱；2.与主要山地相联系的基本带谱；3.与特殊地生态现象相联系的过渡/特殊带谱；4.与人类干扰相联系的扰动带谱；5.与强烈人类活动相联系的次生带谱。     

Vegetable matter dynamics in geosystems of the Nazarovskaya forest-steppe

The long-term vegetable matter dynamics in geosystems of the Nazarovskaya forest-steppe is considered. The differences in phytomass reserves for the facies of the Berezovskii area are demonstrated. The study revealed a clear-cut rhythmic behavior of variability in phytomass and its life forms which is attributed to the bioclimatic situation not only in a current year but also in preceding years. It is shown that anthropogenically disturbed lands are experiencing a progressive succession which manifests itself in successive changes of the grass stand.     

Highly variable sediment distribution in shallow, wind-stressed lakes: a case for sediment-mapping surveys in paleolimnological studies

We examine sediment distribution patterns in seven Florida lakes and discuss implications for paleolimnological studies of shallow, subtropical lakes. The study lakes are highly productive and should exhibit thick organic sediment deposits, but organic sediments are often grossly lacking because basins are shallow, and frequent mixing, lack of stratification, and warm temperatures lead to breakdown of organic material.Organic sediment distribution patterns are highly variable. We observe three types of distribution patterns. When organic sediments are abundant, there may be (1) uniform sediment distribution. In lakes lacking organic sediments, there are (2) distribution to deeper areas if present, or (3) distribution to peripheral areas and embayments when deep waters are absent. We advocate the use of systematic mapping surveys to locate optimal coring sites for paleolimnological studies of shallow, wind-stressed lakes. Because numerous factors affect diagenesis and sediment redistribution, sediment abundance and location are not predictable. Sediment chronologies may be discontinuous and disturbed even in accumulation zones. The extent to which sedimentary records are discontinuous or disturbed is not quantifiable in any practical manner. ²¹⁰Pb and ¹³⁷Cs radioisotopic profiles provide qualitative evidence of the degree of stratigraphic disturbance. Total excess ²¹⁰Pb inventories show that sediments are focused into depositional zones when sediment distribution is uneven. Excess ²¹⁰Pb inventories are not informative about the completeness of sedimentary profiles unless small inventories suggest discontinuous sedimentation or erosional events. We present examples of disturbed and undisturbed profiles, and discuss how we use radioisotopic and geochemical evidence, and multiple cores to assess stratigraphic continuity.Journal Series No. R-04815 of the Florida Agricultural Experiment Station.