孔雀河应急输水后的地下水响应研究

依据输水前后地下水埋深动态来评估孔雀河应急输水工程的实施效果。结果表明,输水显著减小了距河岸0~300m范围内的地下水埋深差异;地下水对应急输水的响应迅速,在输水结束后1周内地下水埋深趋于稳定;输水对地下水的横向影响范围超过垂直河岸300m;输水对地下水位的抬升效果显著,上游普惠区段抬升2.54m,中游尉犁区段抬升3.18m。输水后上游普惠区段平均地下水埋深8.05m,达到了荒漠河岸林胡杨和柽柳生存的地下水埋深阈值;中游尉犁区段平均地下水埋深为11.69m,天然植被仍无法有效利用,因此孔雀河生态输水必须持续性、常态化已达到生态恢复的目的。     

塔里木河下游工程输水后的生态效益分析

以塔里木河下游为研究区域,分析了生态输水工程实施以来该区地下水埋深、水质、植被生长状况的不同响应程度。研究表明:生态输水工程使得原本较低的地下水位在一段时间内得到抬升,局部生态环境得到改善,尤其在输水中期(2003-2005年),植被物种组成发生变化,物种多样性增加,植被盖度提高,地下水水质有所好转;但2007年以后,尤其是2008年,随着输水的间断,下游地下水位开始回落,草本植物物种数量又开始减少,因此,生态输水工程必须持续进行才能真正挽救塔里木河下游生态环境。     

低温雪灾后莽山保护区森林植被恢复遥感评价

以2008年1月的低温雪灾为背景,选择反映植被长势的植被覆盖度为研究对象,以受人类活动干扰最少、最能体现植被自然恢复的莽山保护区为研究区,以像元二分模型为基础,通过计算样区植被遥感直方图的拐点来确定NDYI(soil)和NDVI(veg),通过植被覆盖的变化情况来衡量低温雨雪后森林植被的恢复状况,并对不同地形条件下、不同林龄和树种的森林植被恢复情况进行了分析,以期为整个莽山乃至南方受灾地区的受灾程度评价提供方法支持,为灾后重建决策提供数据参考.     

塔河下游胡杨和红柳自然恢复的土壤条件初步研究

主要研究了塔里木河下游中段，随塔里木河下游应急放水，河滩地的胡杨和红柳种子出苗与根系吸水后重新发芽生长等自然恢复措施的同时，分析了河床自然淹水条件下林灌草甸土的水分，盐分和肥力变化状况及其对胡杨和红柳乔灌木植被种子出苗和地下水位的升高对升灌木根系重新发芽生长的效果。根据对塔河下游定点观测取样分析结果来看，淹水林灌草甸土不但是自然恢复保护塔河下游绿色走廓的根本基础，而且是恢复与保护绿色走廓的一项有效措施。     

浅析工程建设活动引发的植被破坏问题与恢复治理方法

文章介绍了青海省境内由于人类工程活动引起的植被破坏问题,并阐述了植被恢复工程现状与效果,提出了新的治理技术和方法。分析了针对工程活动破坏的植被恢复工程的重要性,针对性地提出了关于植被恢复的建议。     

大渡河流域干冷河谷特征植被调查分析——以某水电站为例

水电开发建设促进经济发展、增加清洁能源的同时,势必会对当地生态环境造成一定影响。特别是对于地处干冷河谷地区工程建设后的植被恢复工作一直是工程实践的难题。选取大渡河流域上游电站施工区作为研究对象,对该区域典型的干冷河谷植被特征进行调查分析,以气候地形、植被特征和植物种类为调查重点,分析了不同立地条件下的植被分布特征及影响要素,成果可为干冷河谷区域水电开发建设中的植被恢复技术的可行性论证和植被恢复工程方案提供参考。     

废弃矿山地质环境恢复治理方案分析

文章介绍了某废弃矿山绿色植被恢复项目的恢复方案、恢复措施、绿色植被的选型及种植,对废弃矿山采取有针对性的恢复措施,才可恢复其生态环境。     

塔河上游地区阿拉尔段天然退化生态系统植物群落物种多样性特征分析及恢复途径

通过对塔河上游阿拉尔地区天然植被的物种多样性的特征分析,并结合实际情况,得出了该地区天然植被生态系统在人类干扰下普遍存在退化现象,尤其在绿洲—荒漠过渡带,这种现象更为严重。应采取有效措施对天然植被特别是过渡带的植被进行生态恢复。另外还讨论了本地区植被恢复与重建的对策。     

森林植被在生态环境建设中的作用

本文对森林植被在生态环境建设中的作用进行了分折,指出森林植被建设是生态环境建设的重点,建议加快我因森林植被的建设与恢复,改善生态环境。     

矿区废弃地植被恢复中的森林生态效益计量分析

基于矿区废弃地植被恢复的视角，在分析矿区废弃地生态系统脆弱性和森林生态效益价值计量理论与方法的基础上，探讨了森林生态效益计量问题。结合矿区废弃地的相关特点，对矿区废弃地植被恢复中森林生态效益计量的具体指标进行了筛选。通过研究，选出涵养水源、净化大气、生物多样性保护、保持水土、游憩效益5个具体效益价值计量指标，为今后矿区废弃地植被恢复中森林生态效益价值的计量研究提供借鉴。     

公路建设中水土流失分析及对策建议

以天津地区公路建设为例,分析了公路建设过程中水土流失主要受降雨、植被的减少、地形、土壤、人工因素等方面的影响。根据水土流失方程式对公路施工前后水土流失的情况进行了分析,结果显示公路建成一般需要2~3年,由于植被的恢复,水土流失可恢复到施工前的水平,并且随着植被的生长,道路沿线的水土流失会比施工期减轻。     

Early Vegetation Development on an Exposed Reservoir: Implications for Dam Removal

The 4-year drawdown of Horsetooth Reservoir, Colorado, for dam maintenance, provides a case study analog of vegetation response on sediment that might be exposed from removal of a tall dam. Early vegetation recovery on the exposed reservoir bottom was a combination of (1) vegetation colonization on bare, moist substrates typical of riparian zones and reservoir sediment of shallow dams and (2) a shift in moisture status from mesic to the xeric conditions associated with the pre-impoundment upland position of most of the drawdown zone. Plant communities changed rapidly during the first four years of exposure, but were still substantially different from the background upland plant community. Predictions from the recruitment box model about the locations of Populus deltoides subsp. monilifera (plains cottonwood) seedlings relative to the water surface were qualitatively confirmed with respect to optimum locations. However, the extreme vertical range of water surface elevations produced cottonwood seed regeneration well outside the predicted limits of drawdown rate and height above late summer stage. The establishment and survival of cottonwood at high elevations and the differences between the upland plant community and the community that had developed after four years of exposure suggest that vegetation recovery following tall dam removal will follow a trajectory very different from a simple reversal of the response to dam construction, involving not only long time scales of establishment and growth of upland vegetation, but also possibly decades of persistence of legacy vegetation established during the reservoir to upland transition.     

Impact of the December 2004 tsunami on soil, groundwater and vegetation in the Nagapattinam district, India

The tsunami of 26 December 2004 struck the Nagapattinam District, Tamil Nadu, India. Sea water inundation from the tsunami caused salinization problems for soil and groundwater in coastal areas of the district, and also induced salt injuries in crops. To document the recovery of the agricultural environment from the tsunami, we conducted observations of the soil, groundwater, and vegetation. Soil electrical conductivity increased sharply after the tsunami, but returned to pre-tsunami levels the following year. Groundwater salinity returned to pre-tsunami levels by 2006. These rapid rates of recovery were due to the monsoon rainfall leaching salt from the highly permeable soils in the area. MODIS NDVI values measured before and after the tsunami showed that vegetation damaged by the tsunami recovered to its pre-tsunami state by the next rice cropping season, called samba, which starts from August to February. From these results, we conclude that the agricultural environment of the district has now fully recovered from the tsunami. Based on the results, we have also identified important management implications for soil, groundwater, and vegetation as follows: 1) due to the heavy monsoon rainfall and the high permeability of soils in this region, anthropogenic inputs like fertilizers should be applied carefully to minimize pollution, and the use of green manure is recommended; 2) areas that were contaminated by sea water extended up to 1000 m from the sea shore and over pumping of groundwater should be carefully avoided to prevent inducing sea water intrusion; and 3) data from a moderate resolution sensor of 250 m, such as MODIS, can be applied to impact assessment in widespread paddy field areas like the Nagapattinam District.     

Recovery in Naturally Dynamic Environments: A Case Study from the Sperrgebiet,Southern African Arid Succulent Karoo

Little is known about the process of vegetation recovery and associated time frames in the Succulent Karoo Biome of southern Africa. This study investigated the recovery of vegetation on sites impacted by mining (different types of dumps and mined areas) in the arid succulent karoo. The main aim of this study was to determine the state of recovery, time frames, successional stages, and the influence of environmental factors on recovery of coastal dune and sand plain plant communities. For this purpose, vegetation was recorded on some 121 sites throughout a coastal strip of approximately 100 × 3 km in Namibia’s restricted diamond area (Sperrgebiet). Using the species pool concept to derive vegetation reference sites and dominance-diversity curves, recovery of vegetation (measured in terms of species richness and cover) in these altered landscapes reached about 46% on the oldest, 51-year-old mine dumps. However, based on species richness, richness levels similar to the undisturbed reference sites were recorded after 30 years, following a logarithmic trend. Successional stages of natural recovery were indicated in this dynamic coastal environment and Cladoraphis cyperoides and Galenia fruticosa appear to be early successional species. Scaling up of studies to landscape level and developing a target community using the species pool concept are discussed as means to measure recovery in dynamic biological communities. On these altered, man-made landforms, the availability of seed may be the bottleneck to achieve vegetation cover comparable to undisturbed vegetation in the surrounding. Hence, restoration efforts should focus on this aspect.     

Sediment delivery linkages in a chaparral watershed following a wildfire

The purpose of this research is to study the temporal and spatial sediment delivery to and within the stream network following a wildfire on a chaparral watershed in Arizona, USA. Methods include interpretation of channel processes (aggradation, degradation) from sequential aerial photographs, field measurements of sediment delivery, and overland flow from ten microwatersheds having different vegetation cover (no vegetation, chaparral cover, and bare with vegetation buffer strips). The response of the watershed to the fire was very complex. The fire reduced the chaparral cover to zero in most locations and severe erosion led to filling of the channels by sediment. With vegetation recovery, sediment delivery from the watershed practically ceased. Vegetation buffer strips were mainly responsible for arresting the sediment delivered from bare hillslopes. Relatively clear water, entering the channels, caused degradation in the tributaries that delivered the sediment into the main stream at El Oso Creek. Due to high water infiltration by immense volumes of sediment deposits in the middle reach, the sediment from the tributaries was deposited as in-channel fans. In contrast, the upper reach of El Oso Creek behaved similarly to the tributaries. It aggraded after the fire and was followed by degradation. The low reach of El Oso Creek is degrading because it is still adjusting base level to the incision of the master stream. Implications of this study are that land managers, concerned to avoid severe erosion and sedimentation following disturbance, should concentrate on the establishment and enhancement of vegetation buffer strips along channel banks.     

Impacts after four years of experimental trampling on alpine/sub-alpine environments in western Tasmania

Experimental trials were undertaken over four years to assess the impact of recreational trampling in undisturbed alpine and sub-alpine vegetation communities in the Western Arthur Range, western Tasmania. Data on 'pad' formation due to human trampling were collected using vegetation cover assessments, biomass estimates and detailed cross-sectional surface profiles. In sub-alpine buttongrass and alpine herbfield, prolonged and sustained damage may occur after 100 passes by walkers. The environmental threshold of the flat alpine herbfield site was breached after 200 passes. Plant morphology was one determinant of resistance and resilience, with upright woody shrubs and tall tussock graminoids most vulnerable to sustained trampling damage. Cushions are susceptible to trampling impacts at 500 passes. Loss of vegetation cover peaks 6-12 months after trampling. Our results show that pads formed with as few as 30-100 passes per annum and tracks form at between 100 and 500 passes per annum. Two years after the cessation of trampling, there is some small recovery in vegetation cover after 30 and 100 passes per annum applied for three years, but no evidence of recovery at the 500 pass treatments. The low trampling threshold and slow recovery rates in western Tasmania suggest that concentrating walkers on a minimal number of sites may be the best management option for these untracked alpine and sub-alpine environments.     

THE EFFECT OF MAINTENANCE ON STORM WATER DETENTION BASIN EFFICIENCY1

ABSTRACT: Storm water detention is an effective and popular method for controlling the effects of increased urbanization and development. Detention basins are used to control both increases in flow rates and sedimentation. While numerous storm water management policies have been proposed, they most often fail to give adequate consideration to maintenance of the basin. Sediment accumulation with time and the growth of grass and weeds in the emergency spillway are two maintenance problems. A model that was calibrated with data from a storm water detention basin in Montgomery County, Maryland, is used to evaluate the effect of maintenance on the efficiency of the detention basin. Sediment accumulation in the basin caused the peak reduction factor to decrease while it increased as vegetation growth in the emergency spillway increased. Thus, the detention basin will not function as intended in the design when the basin is not properly maintained. Thus, maintenance of detention basins should be one component of a comprehensive storm water management policy.     

Rapid vegetation regeneration in a seriously degraded Rhanterium epapposum community in northern Kuwait after 4 years of protection

A study was carried out in northern Kuwait to investigate vegetation recovery in sandy depressions in the Sabriya oilfield ('Sabriya-IN'), 4 years after it was completely protected from livestock grazing and other anthropogenic activities which have largely depleted the dwarf shrub vegetation. This vegetation was compared with that in seriously overgrazed depressions outside the oilfield ('Sabriya-OUT'), where negative influences persist, and with a sandy site in central Kuwait which has been protected for over 20 years ('Sulaibiya'). There has been a striking recovery of the dwarf shrub vegetation in Sabriya-IN during the 4 years, with cover values of shrubs as high as at Sulaibiya. Rhanterium epapposum has been the main species to benefit from protection. However, the shrubs have not regenerated from seed, but rather from underground stumps that have probably remained in the soil for decades. Cover values of the annual flora at Sabriya-IN were very similar to those at Sulaibiya, and they were significantly higher than at Sabriya-OUT. However, it appears that some species may have disappeared or become extremely rare at Sabriya-IN when compared with Sulaibiya, as Sabriya-IN and Sabriya-OUT are remarkably similar floristically. Despite the impressive regeneration of the dwarf shrub vegetation at Sabriya-IN, which contradicts the view that vegetation recovery is a slow process in desert ecosystems, it is important to consider what the natural vegetation was in this part of the world. It is suggested that the region was once dominated by an open Acacia woodland, in which perennial grasses comprised most of the ground layer, and that the current dwarf shrub vegetation is a response to decades, if not centuries, of moderate to heavy grazing.     

Water‐Yield Reduction After Afforestation and Related Processes in the Semiarid Liupan Mountains,Northwest China1

Abstract: The increase of coverage of forest/vegetation is imperative to improve the environment in dry‐land areas of China, especially for protecting soil against serious erosion and sandstorms. However, inherent severe water shortages, drought stresses, and increasing water use competition greatly restrict the reforestation. Notably, the water‐yield reduction after afforestation generates intense debate about the correct approach to afforestation and forest management in dry‐land areas. However, most studies on water‐yield reduction of forests have been at catchment scales, and there are few studies of the response of total evapotranspiration (ET) and its partitioning to vegetation structure change. This motivates us to learn the linkage between hydrological processes and vegetation structure in slope ecosystems. Therefore, an ecohydrological study was carried out by measuring the individual items of water balance on sloping plots covered by different vegetation types in the semiarid Liupan Mountains of northwest China. The ratio of precipitation consumed as ET was about 60% for grassland, 93% for shrubs, and >95% for forestland. Thus, the water yield was very low, site‐specific, and sensitive to vegetation change. Conversion of grassland to forest decreased the annual water yield from slope by 50‐100 mm. In certain periods, the plantations at lower slopes even consumed the runon from upper slopes. Reducing the density of forests and shrubs by thinning was not an efficient approach to minimize water use. Leaf area index was a better indicator than plant density to relate ET to vegetation structure and to evaluate the soil water carrying capacity for vegetation (i.e., the maximum amount of vegetation that can be supported by the available soil water for an extended time). Selecting proper vegetation types and plant species, based on site soil water condition, may be more effective than the forest density regulation to minimize water‐yield reduction by vegetation coverage increase and notably by reforestation. Finally, the focuses in future research to improve the forest‐water relations in dry‐land areas are recommended as follows: vegetation growth dynamics driven by environment especially water conditions, coupling of ecological and hydrological processes, further development of distributed ecohydrological models, quantitative relation of eco‐water quota of ecosystems with vegetation structures, multi‐scaled evaluation of soil water carrying capacity for vegetation, and the development of widely applicable decision support tools.