Indicating appropriate groundwater tables for desert river-bank forest at the Tarim River, Xinjiang, China

Based on data collected over 2 years of monitoring the lower reaches of the Tarim River, the groundwater table depth was divided into six classes; 0 to 2 m, 2 to 4 m, 4 to 6 m, 6 to 8 m, 8 to 10 m, >10 m. We investigated the vegetation in this area to measure the influence of groundwater table depth on plant diversity and species ecological niche. The results indicated that plant diversity was highest at the 2 to 4 m groundwater table depth, followed by that at 4 to 6 m, and then that at 0 to 2 m. When the groundwater depth dropped to below 6 m, species diversity decreased dramatically, and the slope of Hill's index tended to level off. The ecological niche of the major species in this area initially expanded as the groundwater level dropped. The widest niche appeared at the 4 to 6 m groundwater table depth and gradually narrowed with deepening groundwater. Ecological niche analysis also revealed that the 4 to 6 m groundwater table depth was associated with the lowest degree of niche overlap and the richest variety of species. Our findings indicate that in the lower reaches of the Tarim River, the groundwater table depth must be a minimum of 6 m for vegetation restoration; it should be maintained at 2 to 4 m in the vicinity of the water path, and at 4 to 6 m for the rest of this arid area.     

Impacts of ecological water conveyance on groundwater dynamics and vegetation recovery in the lower reaches of the Tarim River in northwest China

The ecological water conveyance project (EWCP) in the lower reaches of the Tarim River provided a valuable opportunity to study hydro-ecological processes of desert riparian vegetation. Ecological effects of the EWCP were assessed at large spatial and temporal scales based on 13 years of monitoring data. This study analyzed the trends in hydrological processes and the ecological effects of the EWCP. The EWCP resulted in increased groundwater storage—expressed as a general rise in the groundwater table—and improved soil moisture conditions. The change of water conditions also directly affected vegetative cover and the phenology of herbs, trees, and shrubs. Vegetative cover of herbs was most closely correlated to groundwater depth at the last year-end (R?=?0.81), and trees and shrubs were most closely correlated to annual average groundwater depth (R?=?0.79 and 0.66, respectively). The Normalized Difference Vegetation Index (NDVI) responded to groundwater depth on a 1-year time lag. Although the EWCP improved the NDVI, the study area is still sparsely vegetated. The main limitation of the EWCP is that it can only preserve the survival of existing vegetation, but it does not effectively promote the reproduction and regeneration of natural vegetation.     

Effect of the ecological water conveyance project on environment in the Lower Tarim River, Xinjiang, China

The dynamic response of groundwater level is examined in traverse and lengthways directions. Take the Yinsu section for an example, we have simulated groundwater levels before and after water-conveyance every time and calculated the incidence of groundwater on the both sides of the river. It is noted that the effect keeps growing with the water-delivery times increasing, from 570 m after the first times to 3,334 m after the eighth times. In addition, this paper involves the temporal response of the natural vegetation to water conveyance, vegetation coverage, planted-species number, dominant position and species diversity from 2002 to 2006. The findings indicate that the positive influence of ecological water conveyance project (EWCP) on the ecosystem in the Lower Tarim River is a long-term process. In this paper, we try to calculate water required for recovery of damaged ecosystem by using data available. This project is likely the base of research on water demand and the reference of measures for research on ecological water conveyance effect.     

紧急调水后塔河下游生态环境的改善恢复情况

塔里木河下游河道断流已经二十多年，地下水位持续下降，绿色走廊濒临绝境，抢救塔里木河下游绿色走廊已迫在眉睫，2001年4月1日第3次向塔河下游输水，并确保向下游输水3亿m^3至台特玛湖，对此分析了紧急调水后塔河下游生态环境的改善情况。     

Influence of intermittent water releases on groundwater chemistry at the lower reaches of the Tarim River, China

Based on the data of the depths and the chemical properties of groundwater, salinity in the soil profile, and the basic information on each delivery of water collected from the years 2000 to 2006, the varied character of groundwater chemistry and related factors were studied. The results confirmed the three stages of the variations in groundwater chemistry influenced by the intermittent water deliveries. The factors that had close relations to the variations in groundwater chemistry were the distances of monitoring wells from the water channel, the depths of the groundwater, water flux in watercourse, and the salinities in soils. The relations between chemical variation and groundwater depths indicated that the water quality was the best with the groundwater varying from 5 to 6 m. In addition, the constructive species in the study area can survive well with the depth of groundwater varying from 5 to 6 m, so the rational depth of groundwater in the lower reaches of the Tarim River should be 5 m or so. The redistribution of salts in the soil profile and its relations to the chemical properties and depths of groundwater revealed the linear water delivery at present combining with surface water supply in proper sections would promote water quality optimized and speed up the pace of ecological restoration in the study area.     

塔里木河下游植被指数的遥感监测

为了了解塔里木河下游9次应急输水的生态环境效益，利用MODIS—NDVI最大合成法、差值法，分析了塔里木河下游植被指数的年际变化情况，结果表明：（1）塔里木河下游地区植被覆盖度变化中增加区面积呈增加趋势。（2）2002年与输水初期相比，植被覆盖度增加区主要分布于上段和中段的老塔里木河及其文阔尔河河道两侧，下段河道覆盖度增加区仅零星分布于距河道0．3km左右的地势低洼区域。2003年以后，下段植被覆盖度增加区面积已达84．30km^2，是2002年的3．16倍，主要分布在距离河道0．5km左右的河道两侧。至2007年塔里木河下游河道两侧植被覆盖度增加区的变化是比较显著的，特别是下段植被覆盖增加区呈带状分布于距河道1．5km左右的范围内。植被指数遥感监测说明塔里木河下游地区的生态环境得到明显改善。     

孔雀河中下游生态环境治理探讨

孔雀河作为塔里木河流域的一条重要河流，被誉为巴音郭楞州人民的“母亲河”。近年来，由于博斯腾湖水位下降，孔雀河上游无序截水灌溉，导致其中下游极度干旱，巳严重威胁到绿色走廊的畅通以及下游农牧区的生产、生活和可持续发展。本文通过对孔雀河中下游环境现状的分析，从其治理的必要性、重要意义、基本原则、对策、建议等方面进行了探讨。     

CVOR在山区河道整治植被恢复综合评价中的应用研究

以石葵河生态河道治理为例,将工程扰动区划分为河道工程区（Q1）、临时施工道路区（Q2）、弃渣场区（Q3）、取土区（Q4）、临时表土堆场区（Q5）等5个分区。采用层次分析法和CVOR模型,构建山区河道整治工程扰动区植被恢复综合评价模型。结果表明：Q1区植被恢复潜力最强,生态健康等级为健康,属容易恢复区,Q4区、Q5区、Q2区生态健康等级为不健康,植被恢复潜力较弱,生态修复中须加大投资;植被恢复潜力与生态系统健康评价结果基本保持一致,基况条件对植被恢复潜力影响较大,可通过人工干扰提高扰动区植被恢复潜力,提升植被恢复效果。     

The threshold between natural recovery and the need for artificial restoration in degraded lands in Fujian Province, China

Whether to use artificial restoration or to allow natural recovery of degraded land has been an important topic in restoration ecology because of the need to determine the most appropriate way to restore degraded lands that have suffered from serious soil erosion. To identify the threshold between a need for artificial restoration and the possibility of natural recovery, we analyzed the vegetation cover, soil fertility parameters, erosion modulus, and runoff coefficient in 32 plots with different vegetation covers in China’s Fujian province from 1999 to 2009. In our study, 20 % vegetation cover appeared to be the threshold between natural recovery and artificial restoration. When vegetation cover dropped below 20 %, it was difficult to stabilize the original ecological structure and functions based on natural recovery mechanisms, and artificial restoration was needed. By monitoring sites to detect when vegetation cover is approaching this threshold, local managers could determine whether natural or assisted recovery represents the most appropriate strategy for ecological restoration.     

塔里木河流域生态脆弱性评价研究

塔里木河流域受自然及人为因素的影响,局部地区生态退化问题突出,从景观生态学的干扰性质理论和恢复生态学的观点出发,选择水资源系统、土地资源系统及植被资源系统及其10个综合性敏感因子对流域生态的敏感性及恢复力进行分析,并确定敏感因子的定量指标,定性代码及其权重和阈值,通过算术对数插值对敏感因子实际值进行规范化处理,并构建生态胁迫度。结果表明,塔里木河三源流阿克苏河流域、叶尔羌河流域、和田河流域及于流区的上、中、下游区生态胁迫度分别为0．13、0．25、0．30、0．31、0．57及0．84,在评价分级标准的限定下,其对应的生态脆弱性程度依次为轻微脆弱、一般脆弱、一般脆弱、一般脆弱、中等脆弱及严重脆弱。     

新疆北部沙漠边缘植被恢复可能性初探

古尔班通古特沙漠边缘植被破坏严重,沙丘活化明显,是新疆干旱植被恢复的重点地区之一,一般缺乏地表水补充,其沙丘的水分状况便成为植被生存和恢复过程的关键条件,为探究古尔班通古特沙漠边缘植被恢复的可能性,在植物生长期内对流动沙丘和固定沙丘不同部位的水分状况进行了连续监测,结果表明:沙丘大多数层次含水量月变化与月降水量分布相一致;流动沙丘含水量从上部到下部依次升高;流动沙丘中部和下部稳定湿沙层处在距沙丘表面60 cm以下,且厚度超过100 cm,固定沙丘稳定湿沙层只存在于沙丘中部距沙丘表面60～150 cm内,其厚度不超过100 cm,在一般年份,该地区利用本地种进行植被恢复是可行的.     

Emergy-based evaluation of system sustainability and ecosystem value of a large-scale constructed wetland in North China

Constructed wetland has been widely adopted to deal with degraded natural wetlands and water bodies; thus, more attention should be focused on ecological–economic sustainability and ecological efficiency of these projects for long-term success. Emergy accounting was conducted to investigate the energy and resource flows in constructed wetlands during the restoration process. Emergy-based indexes were adopted to evaluate the sustainability of a pilot large-scale constructed wetland in a large wetland restoration project in North China, carried out to enhance the river water quality and offset the degradation of natural wetland. Emergy and emdollar values for ecosystem services and natural capital were also calculated. The results showed that when outflow was considered as the product, the studied large-scale constructed wetland was more self-supporting and could be operated with lesser financial investment, although the waste treatment efficiency and the sustainability index were lower than conventional small-scale treatment constructed wetlands. Compared with natural wetlands, more visits from tourists and lesser financial investment coming in as feedback into the wetland would reduce system environment loading and promote system self-support ability, ultimately generating sustainability. In addition, the studied large-scale constructed wetland can effectively simulate energy and resource flows of natural wetland ecosystem and contribute a roughly equal value of ecosystem services in term of gross primary production. The studied large-scale constructed wetland can successfully achieve ecosystem functions as replacement for natural wetland and hasten the restoration process, although the restoration effectiveness of ecosystem structures in terms of living biomass and water using emergy-value accounting is still inconclusive.     

Dynamics of the lakes in the middle and lower reaches of the Yangtze River basin, China, since late nineteenth century

The middle and lower reaches of the Yangtze River basin have the most representative and largest concentration of freshwater lakes in China. However, the size and number of these lakes have changed considerably over the past century due to the natural and anthropogenic impact. The lakes, larger than 10 km² in size, were chosen from relief maps and remotely sensed images in 1875, 1950, 1970, 1990, 2000, and 2008 to study the dynamics of lakes in the middle and lower reaches of the Yangtze River basin and to examine the causes and consequences of these changes. Results indicated that there was a dramatic reduction in lake areas, which decreased by 7,841.2 km² (42.64 %) during the study period (1875–2008), and the number of lakes in this region changed moderately. Meanwhile, a large number of lakes in the middle and lower reaches of the Yangtze River basin were directly converted into paddy fields, ponds, building lands, or other land-use types over the study period. Therefore, all kinds of lake reclamation should be identified as the major driving factors for the loss of lake in this region. Furthermore, flooding, soil erosion, and sedimentation were also the main factors which triggered lake changes in different periods. Some wetland conservation and restoration projects have been implemented since the 1970s, but they have not reversed the lake degradation. These findings were of great importance to managers involved in making policy for the conservation of lake ecosystems and the utilization of lake resources.     

An assessment of restoration success to forests planted for ecosystem restoration in loess plateau, Northwestern China

Using ecosystem attributes identified by the Society of Ecological Restoration International, we assessed three restoration projects in the loess plateau, northwestern China, including planting Larix principis-rupprechtii (LS) and Pinus tabulaeformis (PS) on shrubland, and planting L. principis-rupprechtii on open forest land (LO). The reestablishment of native species in LS and PS was poorer than LO because of the excessive stand density. Species diversity, seedling number, and seedling diversity were significantly higher in LO than in LS and PS. Soil nutrient was also significantly higher in the LO treatment. The vegetation composition, species diversity, and soil nutrient in LO, however, were more similar to these in the reference. Our results indicate that planting L. principis-rupprechtii on open forest land had accelerated the succession of the ecosystem for approximately 30 years. But the poor natural regeneration of L. principis-rupprechtii suggests that post-planting activities in LO are required after timber harvesting or the natural mortality of the L. principis-rupprechtii. Management operation such as selective thinning will be required in LS and PS to promote the true restoration of native species diversity in the future.     

Analysis of the changes of vegetation coverage of western Beijing mountainous areas using remote sensing and GIS

Mentougou District acts as a crucial component in the ecological buffer in western Beijing mountainous areas, Beijing, China. Using two Landsat MSS/TM images acquired on July 14, 1979 and July 23, 2005, the vegetation coverage of Mentougou District was calculated based on normalized difference vegetation index and spectral mixture analysis (NDVI-SMA) model. Its temporal and spatial changes were analyzed according to digital elevation model (DEM) image, social and economic data. The results showed that the vegetation coverage decreased from 76.4% in 1979 to 72.7% in 2005. Vegetation degradation was probably the result of human disturbance, such as outspreading of resident areas, and coal and stone mining activities, while vegetation restoration might be contributed by the combined effects of both natural processes and ecological construction effort. Vegetation changes were closely related to topographical characteristics. Plants at high altitude were more stable and less degraded than the plants at low altitude, while the plants on steep slope or northwest aspect were more vulnerable to degradation. During the period of 26 years, landscape appeared to become more fragmental, and ecological quality of the land seemed deteriorated sharply in that highly-covered vegetation area has been decreased by 24%.     

基于鱼类生物完整性指数的上海苏州河水生态系统健康评价

苏州河横贯上海中心城区，曾是都市污染河流。为从生态学角度揭示苏州河的污染程度，笔者采用鱼类生物完整性指数（F-IBI）评价了苏州河水生态系统的健康状况。分别于2019年6月4—23日（夏季）和9月14—26日（秋季），租用专业渔船在苏州河13个断面采集样本，共采集到10 102尾鱼类，隶属于8目15科37属45种。以大莲湖为参照点，通过判别分析和关联度筛选，从5大类29个初选指标中筛选出10个指标，构建了苏州河F-IBI评价指标体系。分析结果表明：夏季干流上游的5个断面状况为"极好"或"好"，支流3个断面为"好"或"一般"，而干流下游的5个断面则为"差"或"极差"。秋季干流上游5个断面和支流3个断面与夏季的健康状况相似，下游断面则有所改善，仅武宁路桥为"极差"，其余均为"一般"或"差"。研究显示苏州河上游干流的水生态系统已基本恢复，而上游支流和下游干流还未建立健康稳定的水生态系统。建议苏州河环境综合整治第四期工程要更加注重治理岸上的污染源，同步实施干支流水系的污染治理，定期开展城区段淤泥清理，实施岸线的生态化改造。     

基于多时相遥感数据的典型区生态格局变化分析

利用1985、2000、2013年遥感影像提取的土地覆盖数据,通过景观格局指数、动态度计算、转移矩阵等,分析1985—2013年我国典型地区各类型生态系统景观格局及其动态变化特征、生态系统相互转化时空变化特征等,揭示1985—2013年生态环境格局变化的特点和规律:一级分类生态系统综合变化率,赣江、闽江、白龙江和岷江上游流域分别为4.7%、3.9%、3.3%和1.7%,生态系统变化强度1985—2000年较缓,2000—2013年更剧烈。1985—2013年典型区生态系统的主要转化方向具有持续性和双向性特征,岷江、白龙江和赣江上游流域退耕还林还草政策效果明显,出现较高比例的耕地转为森林和草地;面积占67.4%生态系统类型变化与耕地生态系统和人工表面生态系统变化有关;生态系统变化具有明显的区域差异,生态变化主要表现为沿主要河流谷地的线状延伸,主要城镇居民点附近生态系统类型变化较为突出,人类活动是典型地区生态系统类型格局变化的主要驱动力;典型区尤其是敏感区应加大退耕还林还草政策,减少人类经济活动,降低洪水泥石流灾害发生的概率和程度。     

塔里木河下游土地覆盖动态变化分析

利用80－90年代的TM影响数据，借助GIS分析了新疆塔里木河下游典型生态调查区内土地利用／土地覆盖现状及动态变化，并对塔河下游土地开发效果进行了对比分析。结果显示，耕地和城镇居住住用地的增加完全来源于对草地的开垦和对荒漠胡杨林的占用。同时，由于沙化、盐咸化等自然因素的影响和因对水资源的不合理利用所产生的土壤次生盐渍化的共同作用，控制着区内生态环境不断恶化的总体态势。     

Modeling Wetland Plant Community Response to Assess Water-Level Regulation Scenarios in the Lake Ontario – St. Lawrence River Basin

The International Joint Commission has recently completed a five-year study (2000–2005) to review the operation of structures controlling the flows and levels of the Lake Ontario – St. Lawrence River system. In addition to addressing the multitude of stakeholder interests, the regulation plan review also considers environmental sustainability and integrity of wetlands and various ecosystem components. The present paper outlines the general approach, scientific methodology and applied management considerations of studies quantifying the relationships between hydrology and wetland plant assemblages (% occurrence, surface area) in Lake Ontario and the Upper and Lower St. Lawrence River. Although similar study designs were used across the study region, different methodologies were required that were specifically adapted to suit the important regional differences between the lake and river systems, range in water-level variations, and confounding factors (geomorphic types, exposure, sediment characteristics, downstream gradient of water quality, origin of water masses in the Lower River). Performance indicators (metrics), such as total area of wetland in meadow marsh vegetation type, that link wetland response to water levels will be used to assess the effects of different regulation plans under current and future (climate change) water-supply scenarios.The Canadian Crown reserves the right to retain a non-exclusive, royalty free licence in and to any copyright.     

Computation of groundwater resources and recharge in Chithar River Basin, South India

Groundwater recharge and available groundwater resources in Chithar River basin, Tamil Nadu, India spread over an area of 1,722 km² have been estimated by considering various hydrological, geological, and hydrogeological parameters, such as rainfall infiltration, drainage, geomorphic units, land use, rock types, depth of weathered and fractured zones, nature of soil, water level fluctuation, saturated thickness of aquifer, and groundwater abstraction. The digital ground elevation models indicate that the regional slope of the basin is towards east. The Proterozoic (Post-Archaean) basement of the study area consists of quartzite, calc-granulite, crystalline limestone, charnockite, and biotite gneiss with or without garnet. Three major soil types were identified namely, black cotton, deep red, and red sandy soils. The rainfall intensity gradually decreases from west to east. Groundwater occurs under water table conditions in the weathered zone and fluctuates between 0 and 25 m. The water table gains maximum during January after northeast monsoon and attains low during October. Groundwater abstraction for domestic/stock and irrigational needs in Chithar River basin has been estimated as 148.84 MCM (million m³). Groundwater recharge due to monsoon rainfall infiltration has been estimated as 170.05 MCM based on the water level rise during monsoon period. It is also estimated as 173.9 MCM using rainfall infiltration factor. An amount of 53.8 MCM of water is contributed to groundwater from surface water bodies. Recharge of groundwater due to return flow from irrigation has been computed as 147.6 MCM. The static groundwater reserve in Chithar River basin is estimated as 466.66 MCM and the dynamic reserve is about 187.7 MCM. In the present scenario, the aquifer is under safe condition for extraction of groundwater for domestic and irrigation purposes. If the existing water bodies are maintained properly, the extraction rate can be increased in future about 10 % to 15 %.