Damage and recovery of the Gurbantunggut Desert vegeta-tion following engineering activities

The fragile ecological environment of the Gurbantunggut Desert is damaged/disturbedby human activities relating to the development of oil-gas resources and the constructions of de-sert road and great engineering in the Jungger Basin. It was mainly represented: soil compaction,vegetation cleaning, burial of vegetation, oil polluting, and soil disturbance. With investigation andexperiment, we found that when the way and intensity of engineering activities disturbing theeco-environment does not make its ecological stability disintegrated, the desert vegetation has acapacity of natural recovery. To speed and strengthen the process of vegetation recovery efficientassistant measurements, including stabilizing mobile sands promptly and sowing seeds of shruband herb plants in good time will be needed.     

Multi-method pIRIR dating of sedimentary sequences at the southern edge of the Gurbantunggut Desert,NW China and its palaeoenvironmental implications

The Gurbantunggut Desert is the second-largest desert in China, located in the westerly-dominated region of north-western China. Previous understanding of palaeoclimate of this desert was mostly based on lake and loess records from the Junggar Basin and Tian Shan Mountains, whilst direct dating of sedimentary records from the desert was very limited. This study applies high-resolution post-infrared infrared stimulated luminescence (pIRIR) dating to three sedimentary profiles at the southern edge of the Gurbantunggut Desert, which contain aeolian sand and water-lain sediments, recording palaeoenvironmental changes at the desert margin since the Last Glacial Maximum (LGM). Different pIRIR dating procedures were applied for samples with different ages. For Holocene-aged samples, a single-aliquot regenerative-dose (SAR) pIRIR procedure based on a three-stepped pIRIR measurement at 110 °C, 140 °C and 170 °C was used, and a standard growth curve (SGC) procedure yields an equivalent dose (D_e) similar to that of the full-SAR procedure; thus, is applicable for accelerating D_e measurement. For samples much older than the Holocene, a multi-aliquot regenerative-dose (MAR) pIRIR procedure based on a three-stepped pIRIR measurement at 150 °C, 200 °C and 250 °C was found to be the optimal dating procedure, because a SAR procedure would yield underestimated ages due to uncorrected initial sensitivity change. pIRIR dating results of the investigated profiles reveal a substantial sand accumulation during the LGM, an intensification of aeolian deposition at ∼12 ka and a wetter depositional environment at ∼10–8 ka. A rapid fluvial deposition is dated at ∼20–19 ka, corresponding to the deglaciation period. The sedimentary records from the desert margin show some correlation with lake and loess records in the same region and suggest a complex response of the desert environment to different climatic factors.     

Influences of vegetation disturbance on hydrogeomorphic response following wildfire

Quantifying the linkages between vegetation disturbance by fire and the changes in hydrologic processes leading to post‐fire erosional response remains a challenge. We measured the influence of fire severity, defined as vegetation disturbance (using a satellite‐derived vegetation disturbance index, VDI), landscape features that organize hydrologic flow pathways (relief and elongation ratios), and pre‐fire vegetation type on the probability of the occurrence of post‐fire gully rejuvenation (GR). We combined field surveys across 270 burned low‐order catchments (112 occurrences of GR) and geospatial analysis to generate a probabilistic model through logistic regression. VDI alone discriminated well between catchments where GR did and did not occur (area under the curve = 0.78, model accuracy = 0.72). The strong effect of vegetation disturbance on GR suggests that vegetation exerts a primary influence on the occurrence of infiltration excess run‐off and post‐fire erosion and that major gully erosion will not occur until fire consumes aboveground biomass. Other topographic and local factors also influenced GR response, including catchment elongation, per cent pre‐fire shrub, mid‐slope riparian vegetation, armoured headwaters, firehose effects, and concentration of severe burn in source areas. These factors highlight the need to consider vegetation effects in concert with local topography and site conditions to understand the propensity for flow accumulation leading to GR. We present a process‐based conceptual hydrologic model where vegetation loss from fire decreases rainfall attenuation and surface roughness, leading to accelerated flow accumulation and erosion; these effects are also influenced by interactions between fire severity and landscape structure. The VDI metric provides a continuous measure of vegetation disturbance and, when placed in a hydrologic context, may improve quantitative analysis of burned‐area susceptibility to erosive rainfall, hazard prediction, ecological effects of fire, landform evolution, and sensitivity to climate change. Copyright © 2015 John Wiley & Sons, Ltd.     

Channel and vegetation recovery from dredging of a large river in the Gulf coastal plain,USA

Anthropogenic impacts in large rivers are widely studied, but studies of recovery once a disturbance has stopped are uncommon. This study examines the biogeomorphic recovery of a 40-km river corridor on the mid-Apalachicola River, Florida following the cessation of dredging, disposal, and snag removal in 2002. This failed navigation project resulted in vegetation losses (~166 ha between 1941 and 2004), river widening, and increased point bar areas. We used paired sets of imagery for a 10-year period during the recovery process at two different flow levels to assess sand bar change, land cover change, and their spatial variations. Most large sand bars decreased significantly in area due to growth of pioneer species, typically from the bankside of the bar. Mean bar area shrank 0.17 and 0.20 ha for the 30th and 1st percentile flows, respectively. For the entire study area, both water-level comparisons showed gains in vegetation (23.36 and 15.83 ha), compensated by losses in the extent of water (16.83 and 8.55 ha) and sand bar losses (6.53 and 7.28 ha). Overall, these gains during the 10-year passive recovery period are equivalent to ~15% of the vegetation losses that resulted from the navigational dredging. As found in other studies, most of the pioneer vegetation grew approximately 2 m relative elevation above the low-water surface. The initial length of the tree line and the area of herbaceous growth both had a significant and positive relationship with the area of new vegetation growth over the study interval. As parts of the river are healing, reduced channel capacity from narrowing and tree growth will benefit the floodplain. As elsewhere, understanding of a river's biogeomorphology, hydrology, and disturbance history can help in selecting appropriate recovery metrics to further advance the understanding and management of disturbed floodplains. © 2020 John Wiley & Sons, Ltd.     

宁洱6.4级地震城市工程震害调查

本文根据2007年6月3日发生的云南省宁洱6.4级地震现场调查结果,简要分析了此次地震记录到的强震加速度记录及其与工程结构震害的关系,简要描述并总结分析了调查获得的各类城市工程结构、非结构附属物及设备等的部分震害状况及原因,并针对性的给出了提高其抗震性能的建议,探讨提出了需要进一步深入研究的问题。     

Experimental engineering procedure for the recovery of liquid water from the atmospheric vapor content

Summary It is proposed that liquid water be recovered from the atmosphere through a partial duplication of natural moist convection processes within an experimental piece of equipment in which certain of the actions could be protected and enhanced. No source of driving energy other than the automatic release of latent heat of condensing water vapor is envisioned. Various problems of a scientific and engineering nature that arise are enumerated and discussed in a preliminary fashion.     

Impacts of artificially planted vegetation on the ecological restoration of movable sand dunes in the Mugetan Desert,northeastern Qinghai-Tibet Plateau

Controlling desertification is an important ecological target for the Qinghai-Tibet Plateau of China, where studies on impacts of vegetation restoration measures on sandy soil improvement are still lacking. The Mugetan Desert in Guinan County, Qinghai Province, northeastern Qinghai-Tibet Plateau is a repre-sentative ecological restoration area. The impacts of artificial vegetation on the ecological restoration and its properties are studied by using field investigation and sample testing including contents of the surface layer and the vegetation composition of movable, semi-fixed, and fixed sand dunes. Results demonstrate that the moss crust has formed on the surface of a sand dune which has become fixed after 30 years under the impact of artificial vegetation (i.e. Cathay poplar). Meanwhile, the clay minerals, organic matter, and other soil available nutrients have markedly increased. A correlation has been found between these materials, i.e., clay minerals and organic matter content increasing with silt and clay increases with reduction in sand content. In addition, soil nutrient were positively correlated with the increase of plant diversity.Under the current meteorological conditions, the artificial vegetation is helpful for the stabili-zation of sand dune and the ecological restoration in the Mugetan Desert.     

Dating lava flows of tropical volcanoes by means of spatial modeling of vegetation recovery

The age of past lava flows is crucial information for evaluating the hazards and risks posed by effusive volcanoes, but traditional dating methods are expensive and time‐consuming. This study proposes an alternative statistical dating method based on remote sensing observations of tropical volcanoes by exploiting the relationship between lava flow age and vegetation cover. First, the factors controlling vegetation density on lava flows, represented by the normalized difference vegetation index (NDVI), were investigated. These factors were then integrated into pixel‐based multi‐variable regression models of lava flow age to derive lava flow age maps. The method was tested at a pixel scale on three tropical African volcanoes with considerable recent effusive activity: Nyamuragira (Democratic Republic of Congo), Mt Cameroon (Cameroon) and Karthala (the Comoros). Due to different climatic and topographic conditions, the parameters of the spatial modeling are volcano‐specific. Validation suggests that the obtained statistical models are robust and can thus be applied for estimating the age of unmodified undated lava flow surfaces for these volcanoes. When the models are applied to fully vegetated lava flows, the results should be interpreted with caution due to the saturation of NDVI. In order to improve the accuracy of the models, when available, spatial data on temperature and precipitation should be included to directly represent climatic variation. Copyright © 2017 John Wiley & Sons, Ltd.     

The relative roles of climate variations and human activities in vegetation change in North China

Using SPOT-VEGETATION Normal Difference Vegetation Index (SPOT/NDVI) data from 1998 to 2011 and climate data obtained from 223 weather stations in or near North China, vegetation variation characteristics within North China were analyzed. Vegetation variation characteristics under the influence of climate variations and human activities were distinguished through a residual analysis. Based on the results of that analysis, the relative roles of climate variations and human activities in vegetation variation were calculated. The results showed that NDVI observed by remote sensing (SPOT/NDVI) increased from 1998 to 2011. The relative roles of climate variations and human activities in vegetation increase were 30.82% and 69.18%, respectively, indicating that human activities played a major role. And observed NDVI showed an increasing trend for different land cover types overall. While NDVI increase in shrub was mainly caused by climate variations, NDVI increases in forest, grassland, farmland, deserts and urban were all primarily caused by human activities. For areas with increasing vegetation, as identified by remote sensing observations in North China, the relative roles of climate variations and human activities in vegetation change were calculated at 14.85% and 85.15% respectively, again indicating that human activities played an important role in vegetation increase. For areas of decreasing vegetation, as identified by remote sensing observations in North China, the relative roles of climate variations and human activities in vegetation change were calculated at 87.72% and 12.28% respectively, indicating that climate variations had large negative effects on vegetation condition. In addition, the relative roles of climate variations and human activities on vegetation variation have obvious spatial differences in North China. Human activities played a positive role in vegetation growth in North China. However, we cannot ignore the function of human destruction on vegetation variation in some areas.     

Adjustment and recovery of unstable alluvial channels: Identification and approaches for engineering management

The management of riverine environments is shown to require a knowledge and awareness of the complex interactions between fluvial and mass-wasting processes, riparian vegetation, and channel form. Identification of the cause of instability rather than the local symptoms, and knowledge of the temporal and spatial aspects of channel adjustment are central to the application of (1) appropriate analyses to estimate future channel changes, (2) appropriate mitigation measures, and (3) the protection of river-crossing structures and adjacent land. Conceptual models of channel evolution and bank-slope development are particularly valuable for interpreting past and present processes, applying appropriate computational techniques to estimate future channel changes, and implementing strategies to mitigate the impacts of processes likely to dominate the channel in the future. Techniques for identification and analysis of channel instability are interdisciplinary and provide a mechanism for estimating changes in channel-bed elevation and channel width with time. Features of channel form and associated riparian vegetation can be used as diagnostic criteria to identify channel processes, the stage of channel evolution and the magnitude and extent of instability. Changes in bed elevation with time can be represented using an exponential function; changes in channel width with time can be calculated using slope stability equations and (or) projection of a temporary angle of stability from a low-angle surface termed the ‘slough line’ that supports re-establishment of woody vegetation. These techniques, in combination with knowledge of the state of channel evolution, can then be used to assess the appropriateness of various mitigation measures to control on-going channel adjustments and to protect river-crossing structures.     

Offshore macrobenthic recovery in the Murchison field following the termination of drill-cuttings discharges

The effects of discharged drilling cuttings contaminated with oil-based drilling fluids on the macrobenthos surrounding several North Sea oil-production platforms have been well documented. Areas of biological effect ranging from highly modified benthic communities, through transitional zones to undisturbed zones have been identified and characterized. Results are presented from a series of studies at the Murchison oil field which indicate partial recovery of macrofaunal communities around the production platform after cuttings discharges had ceased. Eventual rates of recovery of affected macrobenthic communities around production platforms are discussed in terms of persistence of oil in the drilling cuttings and the rates of degradation of the oil and its toxic components.     

浅型富营养湖泊的生态恢复——五里湖水生植被重建实验

依据浅型湖泊生态系统的多稳定态理论,在富营养湖泊治理过程中,当外来污染得到有效控制时,通过人工重建水生植被可以加速湖泊的生态恢复。在五里湖中,挺水植物和浮叶植物都能很好地生长,水底光照不足是沉水植物难以生长的主要原因。在自然条件下建成了永久性挺水植物群落和浮叶植物群落,在人工控制的围隔环境中改善了水底光照条件,建成了沉水植物群落。但这些沉水植物仍不能渡过夏季,主要原因是湖水过深和水温较高,降低水位和建造人工浅滩可为五里湖沉水植被恢复创造有利条件。本研究可为富营养水体的水质控制和植被恢复提供多种实用技术,但在水生植被的结构与环境功能等方面仍需开展深入的定量研究。     

Geomorphic and sediment volume responses of a coastal dune complex following invasive vegetation removal

This paper documents application of an established geostatistical methodology to detect significant changes in a foredune–transgressive dune complex where Parks Canada Agency (PCA) implemented a dynamic restoration program to remove invasive marram grasses (Ammophila spp.) and enhance dynamic dune habitat for an endangered species. Detailed topographic surveys of a 10 320 m² site in the Wickaninnish Dunes in Pacific Rim National Park, British Columbia, Canada for the first year post‐treatment are compared to a pre‐restoration LiDAR baseline survey. The method incorporates inherent spatial structure in measured elevation datasets at the sub‐landscape scale and models statistically significant change surfaces within distinct, linked geomorphic units (beach, foredune, transgressive dune complex). Seasonal and annual responses within the complex are discussed and interpreted. All geomorphic units experienced positive sediment budgets following restoration treatment. The beach experienced the highest differential volumetric change (+1656 m³) and net sediment influx (+834 m³, 0 · 19 m³ m^–2) mostly from supply to the supratidal beach and incipient dune. This sediment influx occurred independent of the restoration effort and was available as a buffer against wave erosion and as supply to the landward dunes. The foredune received +200 m³ (0 · 13 m³ m^‐2) and its seaward profile returned to a similar pre‐restoration form following erosion at the crest from vegetation removal and scarping by high water events. Sediment bypassing and minimal change was evident at the mid‐stoss slope with appreciable extension of depositional lobes in the lee. The transgressive dune complex experienced high accretion following restoration activity (+201 m³) and over the year (+284 m³, 0 · 07 m³ m^–2) mostly from depositional lobes from the foredune, precipitation ridge growth along the downwind boundary, and growth of existing lobes within the complex. Further integration of this methodology to detect significant geomorphic changes is recommended, particularly for applications where sampling densities are limited or logistically defined. Copyright © 2013 John Wiley & Sons, Ltd.     

青海玛多7.4级地震桥梁工程震害特性分析

2021年5月22日青海果洛州玛多县发生7.4级地震,导致了显著的桥梁结构震害。本文基于现场调查,介绍了野马滩大桥、野马滩2号桥、黑河中桥、吾儿美岗大桥和雅娘黄河桥的典型震害特征。进一步结合地震断裂与桥位关系、地震台站的地震动记录与特性分析,初步分析了各桥的地震致灾要素和结构失效机理。野马滩大桥和野马滩2号桥整体划一的落梁震害可能系近断层法向的方向性效应所致;黑河中桥的结构轻微震害应系桥台的纵向约束作用,整个桥梁的纵向地震响应类似于整体式桥;吾儿美岗大桥结构南北方向的地震响应高于东西方向,同时减隔震支座与上、下部结构的有效锚固是发挥其减震耗能功效的必要保证;雅娘黄河桥未见水平方向地震作用所导致的显著震害特征,初步推断墩底的压溃破坏可能系震中竖向地震动所致。     

The effect of the high-speed stream following the corotating interaction region on the geomagnetic activities

The high-speed stream following the corotating interaction regions (CIRs) was analyzed. As a result of the analysis, it is found that the geomagnetic field is continuously disturbed in the high-speed stream in question. The geomagnetic disturbances with long duration recurred several rotations between December 1993 and June 1994. These disturbances were associated with a large recurrent coronal hole expanding from the south pole of the Sun. High-speed solar wind from this coronal hole was observed by the IMP-8 satellite during this period. However, the observed intensities of the geomagnetic disturbances were different for each recurrent period. This is explained by the seasonal effect. The disturbed geomagnetic condition continued in the highspeed stream after the passage of the CIRs. The long duration of these disturbances can be explained by the continuous energy input into the Earths magnetosphere from the high-speed regions following the CIRs. This kind of long-duration geomagnetic disturbance in association with coronal holes has been observed in the declining phase of other solar cycles. The relation between the coronal-hole area and the maximum solar-wind velocity is not good for the well-developed large coronal hole analyzed here.     

Partial recovery of Newark Bay,NJ, following pollution abatement

For the seven months terminating on 17 August 1980, primary sewage effluent was discharged into Newark Bay. From 22 July to 6 October 1980, we collected physical, chemical and biological data in the Newark Bay estuary from the lower Passaic River to New York Harbor. During the period of maximum discharge, the Passaic River and much of Newark Bay were anoxic or nearly so. Recovery of the Newark Bay water following sewage abatement took approximately 30 days. During most of the study period, a bloom of blue-green algae characterized the ‘Passaic River water’. This water was also characterized by chlorophyll-a values as high as 73 mg m^?3. Chlorophyll concentration almost always increased up the bay, along with decreasing salinity, increasing temperature, increasing phosphate-P and decreasing nitrate-N. The decrease in nitrate, however, was associated with an increase in ammonia-N and total N during the period of sewage discharge.     

P-immobilisation and phosphatase activities in lake sediment following treatment with nitrate and iron

The influence of a further developed inlake restoration method on the P-immobilisation and microbial activities, especially under anoxic conditions was investigated. The impact of nitrate and iron dosing with a newly developed nitrate storage compound (Depox^®Fe) was tested in enclosures in the eutrophic dimictic Lake Dagowsee, Germany. Additions of 50 g m⁻² of NO₃⁻–N and 66 g m⁻² of Fe³⁺ ensured availability of nitrate at the sediment surface during a 2-months period.As a result the phosphate release from the anoxic sediments was completely suppressed even 1 year after the application. The hypolimnetic deoxygenation was unaffected by the Depox^®Fe addition. However, sulfur reduction and methanogenesis were inhibited and the phosphatase activity increased.     

Damage data analysis and vulnerability estimation following the August 14, 2003 Lefkada Island, Greece, Earthquake

Earthquake damage data is of vital importance both as an indicator of the likely performance of buildings in future earthquakes, as well as for the calibration of existing theoretical-analytical models regarding building vulnerability. The analysis of damage data collected shortly after the August 14, 2003 Lefkada Island, Greece earthquake revealed the higher vulnerability of masonry buildings vis-à-vis all other building typologies on the island. However, promising means in strengthening the existing masonry stock emerge, when considering the improved performance of buildings of a dual-system of stone-masonry and timber frame – a construction practice uniquely adopted in the island. Based on the parameterless seismic intensity scale (psi) proposed by Spence et al. (1991) a set of preliminary vulnerability curves for the typologies of the island’s buildings are proposed.     

Comparison of dust emissions,transport, and deposition between the Taklimakan Desert and Gobi Desert from 2007 to 2011

The Taklimakan Desert(TD) and Gobi Desert(GD) are two of the most important dust sources in East Asia, and have important impact on energy budgets, ecosystems and water cycles at regional and even global scales. To investigate the contribution of the TD and the GD to dust concentrations in East Asia as a whole, dust emissions, transport, and deposition over the TD and the GD in different seasons from 2007 to 2011 were systematically compared, based on the Weather Research and Forecasting model coupled with Chemistry(WRF-Chem). Dust emissions, uplift, and long-range transport related to these two dust source regions were markedly different due to differences in topography, elevation, thermal conditions, and atmospheric circulation. Specifically,the topography of the GD is relatively flat, and at a high elevation, and the area is under the influence of two jet streams at high altitudes, resulting in high wind speeds in the upper atmosphere. Deep convective mixing enables the descending branch of jet streams to continuously transport momentum downward to the mid-troposphere, leading to enhanced wind speeds in the lower troposphere over the GD which favors the vertical uplift of the GD dust particles. Therefore, the GD dust was very likely to be transported under the effect of strong westerly jets, and thus played the most important role in contributing to dust concentrations in East Asia. Approximately 35% and 31% of dust emitted from the GD transported to remote areas in East Asia in spring and summer, respectively. The TD has the highest dust emission capabilities in East Asia, with emissions of about 70.54 Tg yr.1 in spring, accounting for 42% of the total dust emissions in East Asia. However, the TD is located in the Tarim Basin and surrounded by mountains on three sides. Furthermore, the dominant surface wind direction is eastward and the average wind speed at high altitudes is relatively small over the TD. As a result, the TD dust particles are not easily transported outside the Tarim Basin, such that most of the dust particles are re-deposited after uplift, at a total deposition rate of about 40 g m.2. It is only when the TD dust particles are uplifted above 4 km, and entrained in westerlies that they begin to undergo a long-range transport. Therefore,the contribution of the TD dust to East Asian dust concentrations was relatively small. Only 25% and 23% of the TD dust was transported to remote areas over East Asia in spring and summer, respectively.     

Subgrid modeling of salt marsh hydrodynamics with effects of vegetation and vegetation zonation

Vegetation plays a critical role in modifying inundation and flow patterns in salt marshes. In this study, the effects of vegetation are derived and implemented in a high‐resolution, subgrid model recently developed for simulating salt marsh hydrodynamics. Vegetation‐induced drag forces are taken into account as momentum sink terms. The model is then applied to simulate the flooding and draining processes in a meso‐tidal salt marsh, both with and without vegetation effects. Marsh inundation and flow patterns are significantly changed with the presence of vegetation. A smaller area of inundation occurs when vegetation is considered. Tides propagate both on the platform and through the channels when vegetation is absent, whereas flows concentrate mainly in channels when vegetation is present. Local inundation on vegetated platforms is caused mainly by water flux spilled from nearby channels, with a flow direction perpendicular to the channel edges, whereas inundation on bare platforms has contributions from both local spilled‐over water flux and remote advection from adjacent platforms. The flooding characteristics predicted by the model showed a significant difference between higher marsh and lower marsh, which is consistent with the wetlands classification by the National Wetlands Inventory (NWI). The flooding characteristics and spatial distribution of hydroperiod are also highly correlated with the vegetation zonation patterns observed in Google Earth imagery. Regarding the strong interaction between flow, vegetation and geomorphology, the conclusion highlights the importance of including vegetation in the modeling of salt marsh dynamics. Copyright © 2017 John Wiley & Sons, Ltd.