Silica retention in the Three Gorges Reservoir

A mass balance of dissolved silica (DSi) based on daily measurements at the inflow and outflow of the Three Gorges Reservoir (TGR) in 2007 and a more precise budget, with inflow, outflow, primary production, biogenic silica (BSi) settlement, dissolution of BSi in the water column and flux of DSi at the sediment–water interface in the dry season (April) of 2007 were developed. We address the following question: How much does the Three Gorges Dam (TGD) affect silica transport in the TGR of the Changjiang River (Yangtze River)? The DSi varied from 71.1 to 141 μmol/l with an average of 108 μmol/l, and it ranged between 68.1 and 136 μmol/l, with an average of 107 μmol/l in inflow and outflow, respectively, in the TGR in 2007. The linear relationship of DSi between inflow and outflow water is significant (r = 0.87, n = 362, p < 0.01). Along the main stream of the TGR, the DSi concentration decreases with an average concentration of 84.0 μmol/l in the dry season. However, the stratification of DSi was not obvious in the main channel of the TGR in the dry season. The BSi is within the range of 0.04–5.00 μmol/l, with an average concentration of 2.1 μmol/l in the main channel of the TGR, while it is much higher in Xiangxi Bay (1.30–47.7 μmol/l, 13.1 μmol/l) than in the main stream of the TGR and the other bays. After the third filling of the TGR, approximately 3.8% of the DSi was retained by the TGR based on a 12-month monitoring scheme in 2007, which would slightly reduce nutrient fluxes of the Changjiang River to the East China Sea (2%). DSi was lost during January to June and November, whereas the additions of DSi were found during the other months in 2007. The budget results also indicate that there is a slight retention of DSi. The retention of DSi in the reservoir is approximately 2.9%, while BSi is approximately 44%. Compared with the total silica load, the retention of DSi and BSi in the reservoir is only 5.0% in the dry season. With its present storage capacity, the reservoir does not play an important role as a silica sink in the channel of the TGR. The DSi load is significantly related to discharge both in inflow and outflow waters (p < 0.01). DSi retention, to some extent, is the runoff change due to impoundment.     

Comparative studies on physiological and biochemical adaptation of Taxodium distichum and Taxodium ascendens seedlings to different soil water regimes

Responses of baldcypress (Taxodium distichum) and pondcypress (Taxodium ascendens) seedlings in leaf gas exchange and root metabolism to a wide range of hydrological regimes were studied. Four water treatments included control (C), mild drought (MD), wet soil (WS) and flooding (FL). Both species showed no significant change in net photosynthetic rate (Pn) in response to flooding in contrast to significant reduction in Pn under mild drought conditions. In baldcypress, Pn was also maintained at control level compared to significant increase of Pn in pondcypress when subjected to the wet soil treatment. In flooding, both species showed significant increase in contents of malate and shikimate in their lateral roots and further in total roots, as compared to control. However, different adaptation to flooding was demonstrated in their taproots in contents of malate and shikimate. Furthermore, baldcypress seedlings showed significant reductions in lateral and total root biomass, in contrast with no significant change in that of pondcypress seedlings in response to flooding. In wet soil, no significant effects were revealed in contents of malate and shikimate in roots (including different root portions) of baldcypress seedlings in contrast to significant increase of their contents in lateral roots of pondcypress seedlings. No significant effects on root biomass were detected in either baldcypress or pondcypress seedlings in response to wet soil. When subjected to mild drought, baldcypress seedlings displayed no significant change in contents of malate and shikimate in roots, whereas pondcypress seedlings exhibited significant reduction in content of shikimate in lateral roots and total roots. In addition, root biomass of baldcypress seedlings showed no significant change, while lateral and total root biomass of pondcypress seedlings demonstrated significant increase when mild drought was imposed. These findings indicate that baldcypress and pondcypress appear to be promising candidates for reforestation in the Three Gorges Reservoir region due to their characteristics of water-tolerance and mild drought endurance. However, pondcypress is more resilient than baldcypress to the continuum of water availability conditions expected in the Three Gorges Reservoir region.     

Effects of Flooding on Susceptibility of Taxodium distichum L. Seedlings to Drought

Responses of baldcypress (Taxodium distichum) seedlings to soil moisture were studied to test the hypothesis that flooding may lead to seedling's higher susceptibility to drought. Treatments included a well-watered but drained control (C), continuously flooded (CF), control followed by drought (CD), and flooded followed by drought (FD). Gas exchange values revealed no significant effects on net photosynthetic rate (P_N) in response to flooding. In contrast, after the onset of drought, P_N was significantly reduced in CD and FD plants. Significant growth reductions under mild drought conditions indicated that baldcypress seedlings were drought sensitive. However, comparison of gas exchange rates and growth responses between CD and FD plants indicated that prior flooding had no detectable effect on subsequent sensitivity of baldcypress to drought. These findings explain baldcypress persistence in wetland habitats characterized by periodic flooding and mild drought.     

三峡库区流域水环境保护分区

流域内不同地域的社会经济发展水平、土地利用状况、植被覆盖程度、与水域的相对位置均对水环境质量存在显著影响.围绕水体保护的核心需求,面向流域空间范围开展水环境保护分区十分必要.本文以三峡库区为研究区,着眼于区域生态环境特征、水体压力-响应特征的空间差异性,基于生态因子叠置法、生态敏感性分析等方法,研究三峡库区水环境保护分区.分区综合考虑了水热条件、地势地貌、生态敏感性等因素,将库区划分为:1)红区,即严格保护区,总面积2924 km2,占库区的5.1%;2)黄区,即一级防护区,总面积10477 km2,占库区的18.4%;3)蓝区,即二级防护区,总面积43599 km2,占库区的76.5%.辨识了红区、黄区和蓝区不同分区的关键环境问题,并有针对性地提出各区的发展方向和水环境保护定位.     

三峡库区生态环境与可持续发展对策研究

在分析三峡库区生态环境面临严峻挑战的基础上,指出了三峡库区生态环境的脆弱性、自然资源的不合理开发、管理不当和协调失误、法制观念淡薄和执法力度不足是造成三峡库区生态环境恶化的主要原因,最后提出了减缓三峡库区生态环境恶化的可持续发展对策:生态环境恢复与重建,农业生产方式的转变,管理制度的改革。     

Vertical Variation of Nonpoint Source Pollutants in the Three Gorges Reservoir Region

Nonpoint source (NPS) pollution is considered the main reason for water deterioration, but there has been no attempt to incorporate vertical variations of NPS pollution into watershed management, especially in mountainous areas. In this study, the vertical variations of pollutant yields were explored in the Three Gorges Reservoir Region (TGRR) and the relationships between topographic attributes and pollutant yields were established. Based on our results, the pollutant yields decreased significantly from low altitude to median altitude and leveled off rapidly from median altitude to high altitude, indicating logarithmic relationships between pollutant yields and altitudes. The pollutant yields peaked at an altitude of 200–500 m, where agricultural land and gentle slopes (0–8°) are concentrated. Unlike the horizontal distributions, these vertical variations were not always related to precipitation patterns but did vary obviously with land uses and slopes. This paper also indicates that altitude data and proportions of land use could be a reliable estimate of NPS yields at different altitudes, with significant implications for land use planning and watershed management.     

Biostabilization and Transport of Cohesive Sediment Deposits in the Three Gorges Reservoir

Cohesive sediment deposits in the Three Gorges Reservoir, China, were used to investigate physical and geochemical properties, biofilm mass, and erosion and deposition characteristics. Biofilm cultivation was performed in a recirculating flume for three different periods (5, 10 and 15 days) under ambient temperature and with sufficient nutrients supply. Three groups of size-fractionated sediment were sequentially used, including 0–0.02 mm, 0.02–0.05 mm and 0.05–0.10 mm. Desired conditions for erosion and deposition were designed by managing high bed shear stress at the narrow part of upstream flume and low shear stress at the wide part of downstream flume. Biostabilization and transport characteristics of the biofilm coated sediment (bio-sediment) were strongly influenced by the cultivation period, and the results were compared with clean sediment. The bio-sediment was more resistant to erosion, and the mean shear stress was increased by factors of 2.65, 2.73 and 5.01 for sediment with 5, 10 and 15 days of biofilm growth compared with clean sediment, resulting in less sediment being eroded from the bed. Simultaneously, the settling velocity was smaller for bio-sediment due to higher organic content and porosity (i.e., lower density). Additionally, there was a smaller probability of deposition for sediment with a longer cultivation period after erosion, resulting in more retention time in aquatic systems. These results will benefit water management in natural rivers.     

Soil warming alters seed-bank responses across the geographic range of freshwater Taxodium distichum (Cupressaceae) swamps

? Premise of the Study: Climate warming is predicted to have far-reaching effects on the distribution of species, but those effects may depend on the flexibility of regenerating species in responding to climate gradients. We conducted a study to determine whether the variation in the response of seed banks to temperature varied across the latitudinal range of Taxodium distichum swamps in North America. ? Methods: The soil was collected in a long-term research network and heated experimentally to three current-day spring normal soil temperatures (average maximum daily spring normal soil temperatures during May in Illinois, Arkansas, and Louisiana, USA, respectively: 22°, 25°, and 29°C). A "normal" is the mean temperature calculated over a 30-yr interval (1971-2000). Seed-bank density and biomass responses were examined in relation to latitude and difference in the soil temperature of the experiment and the spring normal. ? Key Results: Using first- and second-order regression analysis, we determined that the variation in total germination density was lowest mid-range and in experimental soil temperatures similar to the spring normal. For some dominant species, the variance in germination density was higher in the northern (Cephalanthus occidentalis) or the southern part of the network (Saururus cernuus and Polygonum pensylvanicum). Overall, the variance of total biomass (root, shoot, whole plant) was higher if the experimental soil temperature was warmer than the spring normal. ? Conclusions: Our results suggest that the regeneration of some populations of swamp species may have more flexibility to respond to climate warming than others.     

三峡库区民间常用中草药水黄连的基源调查

通过实地调查,借助已有各种文献,进行分析、总结、归纳。初步调查了在三峡库区生长的拥有“水黄连”名称的植物13种,其中库区作为“水黄连”药用的有8种。为库区“水黄连”的开发利用提供帮助。     

Littoral zooplankton of the downstream Area of Kaniv Reservoir

The results of an up-to-date study of littoral zooplankton of the downstream area of Kaniv Reservoir are presented. New approaches are applied to establish the monitoring stations, and state-of-the-art methods of sampling are used in regard to the type and size of the studied artificial waterbodies. The existing tendencies of developing the littoral zooplankton species diversity have been analyzed. Three zooplankton species have been registered for the first time for the fauna of Ukraine and 17 species for Kaniv Reservoir. The faunistic composition, biotope-related distribution, and abundance of the zooplankton were assessed.     

Immediate impacts of the second impoundment on fish communities in the Three Gorges Reservoir

Long and short term investigations have revealed dramatic changes in fish communities after impoundments by reservoirs. However, the process of these changes during impoundment remains poorly studied. In 2005 and 2006, before and during the second stage of impoundment of the Three Gorges Reservoir (TGR), in the upper reaches of the Yangtze, China, we investigated fish catches to assess the impacts of reservoir filling on fish community structure. We conducted sampling at 2 sites, Wanzhou reach, which had been inundated by the first water filling in 2003, and Fuling reach, which still remained a riverine site before this water filling. The results revealed an evident and immediate shift of fish communities from lotic to lentic components. In the Wanzhou reach, during the filling, the abundance percentage of lentic fish increased to 94% compared to 69% before the filling. In the Fuling reach, after the filling, lotic fish declined in abundance from 99% to 85%, while lentic fish increased from less than 1% to 12% in abundance. Based on our investigation and the regulation scheme of the TGR, we predicted that after the completion of the Three Gorges Dam (TGD), there would be typical lacustrine, transitional and riverine zones in TGR, with their corresponding fish assemblages. We suggest that long term monitoring should be conducted to evaluate the future ecological effects, and different strategies implemented in these three zones for conservation purposes.     

Distribution and clinical features of Paragonimiasis skrjabini in Three Gorges Reservoir Region

Paragonimiasis has previously been reported in the Southwest Provinces of China, including Chongqing and Sichuan. The construction of Three Gorges Dam, which was begun in 1994, has resulted in substantial changes to the depth and the flow pattern of the Yangtze River. To investigate epidemiology of the paragonimiasis, 724 people aged 2-49years were selected and examined for Paragonimus infection by intradermal test (IDT), and enzyme-linked immunosorbent assay (ELISA). A survey of eating habits was conducted face-to-face in 5 endemic counties. Freshwater crabs were collected from seven sites in the 5 counties to determine the rate of infection with Paragonimus metacercariae. Additionally, we analyzed 213 case reports from the region dated 2006 to 2009. According to the survey results, the prevalence of Paragonimus skrjabini infection in freshwater crab was 39.65%, and the human infection rates detected by IDT and ELISA were 14.36% (104/724) and 7.46% (54/724), respectively. These results show that the Three Gorges Reservoir is still an area of high paragonimiasis endemicity. The water level of the Yangtze River has risen to 175m, and the area of water coverage in the region has increased to 1084km(2). These conditions will favor the growth and expansion of the freshwater crab population.     

三峡库区典型森林植被生态水文功能

以三峡工程库区典型植被类型(针阔混交林、常绿阔叶林、楠竹林、灌木林和农地)为研究对象,采用层次分析法建立森林生态水文功能层次结构模型,用综合评分法进行评价。结果表明:林冠层生态水文功能以灌木林作用最优(得分0.979),为其他乔木林的1.5～2倍。枯落物层以灌木林作用最优(得分1),楠竹林最差(0.422)。土壤层仍以灌木林作用最优(得分0.921),楠竹林最差(0.313);农地是由立地条件一致的灌木林改造8年而来,农地土壤的生态水文功能相对于灌木林地土壤下降了近一半。森林生态系统总体生态水文功能表现为灌木林(得分0.95)针阔混交林(0.52),常绿阔叶林(0.53)楠竹林(0.37)农田(0.33)。可以推断,三峡库区典型林分中,灌木林生态水文功能最优,楠竹林最差,森林的生态水文功能是农地的1.12～2.9倍。     

Application of Structural Equation Models for Elucidating the Ecological Drivers of Anopheles sinensis in the Three Gorges Reservoir

Objective

To identify the major ecological drivers for malaria vector density using the structural equation model (SEM) in the Three Gorges Reservoir.

Method

An 11-year longitudinal surveillance of malaria vector as well as its related ecological factors was carried out in the Three Gorges Reservoir. The Delphi method was used to identify associated ecological factors. The structural equation model was repeatedly corrected and improved by the corrected index, combined with the actual situation. The final model was defined by relative simplicity, best fitting as well as the practicality.

Result

The final model indicated that the direct effects of temperature, livestock, humidity, and breeding on the vector were 0.015, −0.228, 0.450, 0.516 respectively, their total effects on the vector were 0.359, −0.112, 0.850, and 0.043 through different pathways.

Conclusion

SEM was effective and convenient in elucidating the mechanism by which malaria vector dynamics operated in this study. It identified that the breeding had the highest direct effect on vector and played a key role for mediating effect of temperature and humidity.     

三峡库区资源植物的现状与保护

据调查统计,三峡库区有资源植物2070种,其中药用植物1006种、纤维植物104种、油脂植物76种、观赏植物74种、野果植物54种、芳香植物54种、树脂树胶植物68种、淀粉及糖类植物52种,鞣科植物32种、珍稀植物49种、其它类型植物465种。论述了三峡库区资源植物的分类及保护现状。     

落羽杉与墨西哥落羽杉3个杂交后代品系的生长和杂种优势分析

以落羽杉〔Taxodium distichum(Linn.)Rich.〕和墨西哥落羽杉(T.mucronatum Tenore)及其3个杂交后代品系'中山杉405'('Zhongshansha 405')、'中山杉406'('Zhongshansha 406')和'中山杉407'('Zhongshansha 407')2年生盆栽扦插苗为研究对象,对株高和地径的年增长量、总叶面积、株高和地径的增长量动态变化、株高和地径的生长期进行了比较分析,并根据地径增长量分析了3个杂交后代品系的杂种优势.结果表明:3个杂交后代品系的年株高增长量介于父本与母本之间但无显著差异,而三者的年地径增长量和总叶面积则明显高于父本和母本.墨西哥落羽杉与3个杂交后代品系的株高和地径生长期均一致,分别为5月11日至10月5日和6月1日至11月9日;而落羽杉的株高和地径生长期分别为5月11日至8月10日和6月8日至11月16日.5月份至10月份,墨西哥落羽杉的株高持续增长,而3个杂交后代品系的株高不连续增长,落羽杉的株高则在8月10日之后停止生长;生长初期和生长末期,3个杂交后代品系的地径增长量均高于父本和母本;秋季3个杂交后代品系均能快速进行地径生长,而此时父本和母本的地径增长量均下降.除夏季的少数时间段外,'中山杉405'在整个生长季都表现出明显的杂种优势,而'中山杉406'和'中山杉407'在整个生长季总体上表现出杂种优势,且它们的杂种优势最大值均出现在生长后期,说明供试的3个杂交后代品系在秋季也能快速生长.研究结果显示:供试的3个杂交后代品系均遗传了落羽杉地径生长迅速和墨西哥落羽杉株高生长期长的特性,秋季3个杂交后代品系的地径和株高增长量总体上均高于父本和母本,表现出明显的杂种优势.     

Evaluation of Gridded Precipitation Data for Driving SWAT Model in Area Upstream of Three Gorges Reservoir

Gridded precipitation data are becoming an important source for driving hydrologic models to achieve stable and valid simulation results in different regions. Thus, evaluating different sources of precipitation data is important for improving the applicability of gridded data. In this study, we used three gridded rainfall datasets: 1) National Centers for Environmental Prediction - Climate Forecast System Reanalysis (NCEP-CFSR); 2) Asian Precipitation - Highly-Resolved Observational Data Integration Towards Evaluation (APHRODITE); and 3) China trend - surface reanalysis (trend surface) data. These are compared with monitoring precipitation data for driving the Soil and Water Assessment Tool in two basins upstream of Three Gorges Reservoir (TGR) in China. The results of one test basin with significant topographic influence indicates that all the gridded data have poor abilities in reproducing hydrologic processes with the topographic influence on precipitation quantity and distribution. However, in a relatively flat test basin, the APHRODITE and trend surface data can give stable and desirable results. The results of this study suggest that precipitation data for future applications should be considered comprehensively in the TGR area, including the influence of data density and topography.     

三峡库区生态环境教育部重点实验室

三峡库区生态环境教育部重点实验室2003年11月经教育部批准成立。实验室现任学术委员会主任为董鸣研究员,实验室主任为李百战教授。实验室围绕三峡库区水环境、自然生态系统和城镇生态系统, 重点对三峡工程建设和运行期间库区生态环境的演变和发展规律、库区生态环境的综合调控理论与关键技术以及生     

三峡水库泄水期消落带土壤微生物活性

以三峡库区香溪河消落带土壤为对象,研究泄水期(5-8月)消落带不同海拔土壤理化性质及微生物活性,旨在揭示三峡库区消落带土壤质量变化趋势.结果表明:随着海拔降低、淹水强度增强,消落带土壤含水量增加,pH值上升,土壤微生物生物量和微生物熵逐渐降低,土壤代谢熵显著增加,干湿交替区165 m以下土壤代谢熵显著高于未淹没区175 ～185 m.表明香溪河消落带低海拔土壤受江水淹没胁迫,pH值趋于碱性,土壤环境质量降低,不适宜微生物的生长.消落带各海拔土壤SOC、TN和C/N无显著差异;但干湿交替区土壤SOC、TN和C/N的变异系数降低,表明干湿交替是影响库区消落带土壤碳、氮分布的重要因子.相关分析显示,土壤C/N与SOC呈极显著正相关,说明香溪河消落带C/N的变化主要由SOC决定.