Hydro-fluctuation Belt Research Articles

Time-varying reliability analysis of Majiagou landslide based on weakening of hydro-fluctuation belt under wetting-drying cycles

The impoundment of the Three Gorges Reservoir has a significant impact on the storage area, where the frequent occurrence of reservoir landslides with great harm has attracted much attention. Taking the Majiagou landslide as a case, this study focuses on the hydro-fluctuation belt affected by the reservoir operation. Under the scheduling of reservoir water level, the landslide displacement associated with the hydro-fluctuation belt presents a step-like deformation and the movement behaves as a retrogressive type. The wetting-drying cycles test has been performed to simulate the effects of reservoir water level on the hydro-fluctuation belt. Then, the weakening of soil strength parameters is well characterized by an exponential function model. Considering the continuous weakening of the hydro-fluctuation belt, the time-varying reliability, consistent with the actual landslide zoning, is analyzed under the reservoir operation for 10 years. The results indicate that the migration of seepage field in the landslide is closely related to the scheduling of reservoir water level and lags behind the scheduling. Similarly, the factor of safety varies with the reservoir water level, and the minimum value is obtained when the water drops to the lowest level. With the repeated interaction of reservoir water level on the hydro-fluctuation belt, the most dangerous failure probability of the landslide gradually increases. As a result, the stability of the Majiagou landslide declines from the initial basic stable to the less stable state.

Growth and reproductive responses of Polygonum hydropiper populations to elevational difference associated with flooding

Elevation can greatly affect both intensity and duration of flooding in riparian areas, and may thus affect the performance of plants distributed therein. However, few studies have examined the performance of riparian plants over elevation difference.This study compared growth and reproductive traits of populations of the riparian species Polygonum hydropiper distributed at low and high elevations of 10 different riparian locations in the hydro-fluctuation belt of the Three Gorges Reservoir Region, China.Both the location and the interaction between location and elevation had significant effects on almost all growth and reproduction traits of P. hydropiper, suggesting that the effects of elevation varied greatly among different locations. Across all locations, high-elevation plants had significantly higher total biomass, stem biomass, root biomass, and plant height than low-elevation plants. Correspondingly, high-elevation plants also had significantly higher stem starch concentrations. In comparison, low-elevation plants had significantly lower biomass, shorter height, and thinner leaves; while they had significantly higher reproductive allocation, as well as faster germination and higher germination rate at a number of locations. Therefore, low energy consumption and high reproductive capacity could be a survival adaption of low-elevation plants to frequent and deep flooding.Local conditions and/or flooding might impose strong selection pressure on P. hydropiper, thus resulting in intra-specific differentiation. Across all locations, low- and high-elevation populations exhibit different growth and reproduction responses to different flooding regimes.

Spatial–temporal variation of nitrogen and diffusion flux across the water–sediment interface at the hydro-fluctuation belt of Danjiangkou reservoir in China

Abstract Based on overlying water and sediment sample collection from 15 sites during July, September, November 2018 and January 2019 in the hydro-fluctuation belt of Danjiangkou reservoir China, the variation of nitrogen (N) was studied. And the concentrations of NH4+-N, NO3−-N and NO2−-N in the sediment, pore water and overlying water were determined to evaluate the diffusion flux across the water–sediment interface. The results showed that the lowest sediment N concentration was 36.54 mg/L in July, and the highest one was 145.93 mg/L in November. Spatially, the sediment N concentrations were higher in tidal soil and loam than in sandy soil. According to the diffusion fluxes of NH4+, NO3− and NO2−, sediments at all sites tend to release N to the overlying water except in the sampling month of November, when the sediment acts as a sink of NO3−. The highest release rates of NH4+-N and NO3−-N were 17.66 mg m−2·d−1 and 80.15 mg m−2·d−1, respectively, which are much higher than the release rate of NO2−-N (0.29 mg m−2·d−1). The findings indicate that hydro-fluctuation belt sediment contributes a lot to the nitrogen contents in the overlying water, and internal pollution is a main reason for the water quality deterioration and even eutrophication.

Laboratory investigation of the mode-I fracture of sandstone caused by a combination of freeze-thaw cycles and chemical solutions

The mechanical parameters and deterioration mechanisms of sandstone specimens obtained from the hydrofluctuation belt in the Three Gorges Reservoir Region of China were investigated under a combination of freeze-thaw cycles and different chemical solutions. The degradation in several mechanical characteristics was discussed, and the degree of freeze-thaw deterioration of the mechanical behaviors was quantitatively analyzed based on the crack propagation radii and a damage variable that reflects the changes in porosity. The results showed that the mechanical parameters of sandstone had a significant damage deteriorating trend under freeze-thaw cycles and different chemical solutions. And the degree of damage deterioration of fracture toughness KIC was the greatest, followed by that of tensile strength; that of compression strength was the smallest. There was obvious consistency among fracture toughness KIC, tensile strength, and compression strength of sandstone under a combination of freeze-thaw cycles and different chemical solutions; those were obvious linear relationship. The crack propagation radii for the various effects of freeze-thaw cycles and chemical solutions were smaller than those of the natural state and the radii generally decreased with increasing freeze-thaw cycles.

Construction of an integrated technology system for control agricultural non-point source pollution in the Three Gorges Reservoir Areas

Agricultural non-point source pollution (NPSP) is becoming a severe threat and seriously restricting the sustainable development of agricultural economy and rural environment in the Three Gorges Reservoir Areas (TGRA). However, limited studies have focused on agricultural NPSP management in TGRA, especially for integrated technology systems with TGRA characteristics. An integrated slopping land/paddy field/hydro-fluctuation belt eco-system (SPHES) was constructed using best management practices in this study. Evaluation results of the SPHES at the comprehensive test demonstration zone showed that ecological engineering interception technologies on slopping land can reduce 80–90 % of sediment, 20–30 % of nitrogen (N), and 25–35 % of phosphorus (P), respectively. The utility of interception and absorption technology under ridge cropping pattern in paddy fields can effectively control inorganic N in sewage and P in external sewage within one week. Biological sequestration technologies of N and P in hydro-fluctuation belt can intercept 30–50 % of total N, 65–95 % of total P, and 75–90 % of sediments. In summary, the comprehensive removal rate of pollutants in agricultural NPSP exceeded 89 % using this eco-system. The work presented here provides the construction of this integrated eco-system for agricultural NPSP controlling, thereby applying to all small watersheds in the TGRA to control and manage agricultural NPSP. This integrated technology system has broad prospects for promotion and application in similar ecological areas.

Foraging behavior of the Greater White-fronted Goose (Anser albifrons) wintering at Shengjin Lake: diet shifts and habitat use

BackgroundThe habitat use and foraging behaviors of waterbirds are closely related to the distribution and abundance of their food resources. Reductions in food supply can cause waterbirds to shift their habitats and adjust their foraging behaviors to meet their nutritional requirements and increase fitness. Seasonal withdraw of the water levels in the river-connected lakes in the middle and lower Yangtze River floodplain provides abundant food resources for the wintering Greater White-fronted Goose (Anser albifrons). Sedge (Carex) meadows are critical foraging habitats for herbivorous waterbirds in the hydro-fluctuation belt, which changes with hydrological conditions and climate. This study aimed to examine the behavioral responses of the Greater White-fronted Goose to temporal- spatial changes of food availability in the Sedge meadows.MethodsFields surveys were carried out at Shengjin Lake from November 2017 to April 2018. According to the phenology of Shengjin Lake, we divided the wintering season into three periods. The food density, minimum temperature, food items, grass height, and number of foraging geese were surveyed, and samples of the foraging behavior were collected. We analyzed the relationship of the foraging behavior and habitat use relative to the food resources, using correlation and linear regression analyses.ResultsAlong with the temporal-spatial variation and exploitation of food resources, the food abundance and items varied widely among the foraging sites. Over the whole wintering period, the foraging habitat with the highest utilization rate was the meadows, followed by the paddy fields, and then mudflats. Furthermore, the utilization of the meadows showed a bimodal distribution trend, while the paddy fields showed a unimodal trend, and a decreasing trend was seen in the mudflats over the whole wintering period. The results of the generalized linear model showed that the foraging rate was related to the food density and grass height, with a linearly increasing trend during the winter.ConclusionsWith the change of food resources in the three habitats, the habitats used by the Greater White-fronted Geese shifted from meadows in the hydro-fluctuation belt to the paddy fields, and then back to the meadows. The time budget for foraging activities increased correspondingly, and there was an increase in the foraging rate to compensate for food shortages.

The analysis of slippage failure of the HuangNanBei slope under dry-wet cycles in the three gorges reservoir region, China

The purpose of this paper is to study the sliding failure of the jointed rock slope caused by the degradation of rock mass mechanics under dry-wet cycles. Based on the mechanical parameters of reservoir limestone obtained under different numbers of dry-wet cycles, a discrete element approach was adopted to analyze the slippage failure mode of HuangNanBei slope in the Three Gorges Reservoir Region. The Barton-Bandis nonlinear strength criterion for discontinuities was used to improve the Mohr-Coulomb (M-C) sliding model, and the modified M-C sliding model could make the shear strength parameters of the discontinuities change with the stress state. Under the modified model, there was a tendency for disintegration between blocks in the process of slippage, which was more in line with the actual working conditions and proved the validity and necessity of this model. Furthermore, the slip rate increased with the increase of dry-wet cycles, and the increase trend had not slowed down after 30 dry-wet cycles. The cumulative displacement from 0 to 30 dry-wet cycles was obtained by changing the mechanical parameters of the discontinuities every 10 steps to simulate each dry-wet cycle. The pattern of the cumulative displacement curve was consistent with the slip curve of the 30th dry-wet cycle, which indicated that the degradation of the rock mass mechanics is irreversible. Consequently, strengthening the hydro-fluctuation belt is of great significance for disaster prevention and control in the reservoir region.

Effects of waterlogging and increased soil nutrients on growth and reproduction of <i>Polygonum hydropiper</i> in the hydro-fluctuation belt of the Three Gorges Reservoir Region

Effects of waterlogging and increased soil nutrients on growth and reproduction of <i>Polygonum hydropiper</i> in the hydro-fluctuation belt of the Three Gorges Reservoir Region

Mechanism Damage to Mode-I Fractured Sandstone from Chemical Solutions and Its Correlation with Strength Characteristics

The fracture toughness of rock is very important in rock cutting, blasting, and hydraulic fracturing for tunnel excavation. To evaluate factors that reduce rock fracture toughness, we emulated the environment of joint rock in the hydro-fluctuation belt of a typical bank slope in the Shanxi Tong Chuan reservoir region. We tested long-term immersion of sandstone samples in different chemical solutions to determine the resulting mechanical characteristics and damage degradation. Variations in the physical and mechanical properties of the samples were analyzed under the effects of the chemical solutions. Experimental results show that the sandstone was significantly damaged by the chemical solutions, but its peak strain increased, and different chemical solutions had distinct influences on the degree of mechanical damage. These differences varied with the acid–base properties of the solutions. Also, there were clear consistencies among the solutions in the degree of their damage to mechanical parameters, physical parameters, and ion concentrations. Therefore, we were able to obtain correlations among the physical and mechanical parameters of the sandstone samples, damage variables, and the ion concentrations of calcium and magnesium. The surfaces of the samples were seriously degraded after being subjected to the corrosive effect of various chemicals; for example, there were different amounts of holes and pitting corrosion. The sizes of the holes and the degree of surface pitting gradually increased with an increase in corrosion time.

The hydro-fluctuation belt of the Three Gorges Reservoir: Source or sink of microplastics in the water?

Reservoirs can be an important environmental compartment for microplastic pollution. Previous investigations have found that surface waters and sediments in the Three Gorges Reservoir (TGR) have had high microplastic abundance, and the Xiangxi River, which is one of the largest primary tributaries of the TGR, has had much higher microplastic abundance than several marine and freshwater systems in China. A strip of land on the bank of the reservoir area, which is called the hydro-fluctuation belt (HFB), is periodically exposed due to the special hydrodynamic conditions in the TGR. The HFB may be an important source and/or sink of microplastics in TGR. In this study, microplastic occurrence in sediments from the Xiangxi River HFB was investigated to reflect the local microplastic pollution status and to evaluate its potential to serve as a source/sink of microplastics in the TGR. Seven sampling sites were selected, and sediments within the HFB and above the belt were collected in summer when the water level was low. The results showed that the microplastic abundance ranged from 0.55 ± 0.12 × 103 to 14.58 ± 5.67 × 103 particles m−2, which was one to two orders of magnitude higher than that in sediments from the Xiangxi River in our previous study (80–846 particles m−2). Statistical analysis revealed that the microplastic abundance within the HFB was significantly higher than that of the area above the HFB. The results indicate that the HFB can be an important microplastic sink when the water level is low, and the belt can turn into a potential source when the water level is high. Cluster analysis was applied to reveal the characteristics of the microplastics collected at different sites, and the results suggest that the cluster analysis may be a useful tool in elucidating the source and fate of microplastics.

Analysis of Changes in the Micromorphology of Sandstone Joint Surface under Dry-Wet Cycling

Changes in the micromorphology of joint surface under dry-wet cycling have a direct effect on the mechanical properties of the jointed rock masses, which in turn affects the deformation stability of the bank slope of a reservoir. In this study, we design and carry out a test that aims to quantity the effects of repeated rise and fall of a reservoir on the properties of a jointed rock masses. The results are as follows: first, the roughness, local gradient, and undulation of the joint surface gradually decreased under repeated dry-wet cycling. In addition, the height parameters and texture parameters showed a steep decrease followed by a slow decline. The deterioration was particularly obvious over the first 5 dry-wet cycles. Second, the roughness coefficient of the joint surface, the compressive strength of the face wall, and the basic friction angle were gradually reduced under dry-wet cycling. The shear strength of the jointed rock masses (obtained both quantitatively and experimentally) showed a deteriorating trend controlled by the deterioration of the micromorphology, the strength of the face wall, and the frictional properties of the joint surface. Finally, the dry-wet cycling process determined trends of changes in the microstructure parameters and mechanical properties of the joint surface. Our research results provide a good basis for the analysis of the deterioration and failure of rock masses within the hydrofluctuation belt of a bank slope.

三峡消落带落羽杉人工幼林叶片分解及磷释放特征

PDF HTML阅读 XML下载 导出引用 引用提醒 三峡消落带落羽杉人工幼林叶片分解及磷释放特征 DOI: 10.5846/stxb201808091698 作者: 作者单位: 三峡库区生态环境教育部重点实验室，重庆市三峡库区植物生态与资源重点实验室，西南大学生命科学学院，重庆400715,三峡库区生态环境教育部重点实验室，重庆市三峡库区植物生态与资源重点实验室，西南大学生命科学学院，重庆400715,三峡库区生态环境教育部重点实验室，重庆市三峡库区植物生态与资源重点实验室，西南大学生命科学学院，重庆400715,三峡库区生态环境教育部重点实验室，重庆市三峡库区植物生态与资源重点实验室，西南大学生命科学学院，重庆400715,三峡库区生态环境教育部重点实验室，重庆市三峡库区植物生态与资源重点实验室，西南大学生命科学学院，重庆400715,三峡库区生态环境教育部重点实验室，重庆市三峡库区植物生态与资源重点实验室，西南大学生命科学学院，重庆400715 作者简介: 通讯作者: 中图分类号: 基金项目: 重庆市林业重点科技攻关项目（渝林科研2016-8，2019-16）；国家科技部国际合作专项（2015DFA90900）；中央财政林业科技推广示范项目（渝林科推2014-10） Foliar decomposition and phosphorus release in a Taxodium distichum young forest stand rehabilitated in the hydro-fluctuation belt of the Three Gorges Reservoir Author: Affiliation: SOUTHWEST UNIVERSITY,SOUTHWEST UNIVERSITY,SOUTHWEST UNIVERSITY,SOUTHWEST UNIVERSITY,SOUTHWEST UNIVERSITY,SOUTHWEST UNIVERSITY Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为探究三峡消落带人工重建植被落羽杉（Taxodium distichum）幼林叶片在不同水文条件下的分解特征及其对土壤-水体磷的贡献潜力，本实验在控制条件下，模拟三峡库区消落带土壤水分变化设置了常规生长水分条件（CK）、轻度干旱水分胁迫（T1）、潮湿（T2）、2 cm水淹（T3）、10 cm水淹（T4）5个不同处理，研究落羽杉叶片分解及磷释放特征。研究结果表明：（1）在整个试验期间（90 d），T3、T4两个水淹处理的叶片失重率分别达51%（T3）和55%（T4），显著高于CK、T1、T2三个未水淹处理；（2）未分解残留叶片中的全磷含量在CK、T1、T2三个未水淹的处理组呈现增加趋势，而水淹处理（T3、T4）呈减少趋势；（3）土壤全磷含量在试验过程中呈现波动性变化特征，但至试验结束时，各处理中土壤全磷含量与CK相比均无显著差异；（4）T3、T4处理中叶片添加显著增加了上覆水体中总磷含量，试验过程中呈现出在分解初期迅速上升，在分解10 d时达到峰值，之后逐渐降低并趋于稳定，但试验结束时仍显著较高，分别是对应无叶片组的17.15倍（T3）和5.81倍（T4）。这些结果说明水淹通过促进落羽杉叶片的分解从而增加上覆水体中磷的含量，因此有必要在水淹前对消落带的落羽杉幼林叶片进行适时采收，以尽可能减少其对库区水体的磷负荷。 Abstract:To explore traits related to leaf decomposition and the potential contribution of the phosphorus of the leaves of Taxodium distichum to the soil-water system in the fluctuation zone of the Three Gorges Reservoir, an indoor experiment was conducted upon simulation of the water change of the hydro-fluctuation belt in the reservoir. Five different kinds of water treatments were applied to investigate leaf decomposition processes of T. distichum and phosphorus release characteristics. Five water treatments included normal growth water condition (CK), light drought water stress (T1), water saturation (T2), 2 cm flooding (T3), and 10 cm flooding (T4). The results showed that:1) During the entire experiment period (90 d), the rate of leaf weight loss of the two flooding groups reached 51% (T3) and 55% (T4), which were significantly higher than that of the three unflooded treatment groups of CK, T1, and T2; 2) The total phosphorus content in leaves increased in the CK, T1, and T2 treatment groups, but decreased in the flooding treatments (T3 and T4); 3) The total phosphorus content of the soil showed fluctuation characteristics during the experiment period, but at the end of experiment there was no significant difference in soil total phosphorus content between the treatment groups and the CK group; 4) During the experiment period, total phosphorus content of the overlying water of the T3 and T4 treatment groups with addition of leaves increased significantly compared with that of the respective treatment groups without addition of leaves and showed a rapid increase in the initial decomposition rate followed by a gradual decrease and finally a stable state. The peak value of leaf decomposition was observed on the 10th day, after which leaf decomposition decreased. However, at end of the experiment the total phosphorus content of T3 and T4 treatment groups with addition of leaves was still significantly higher than that of the respective treatment groups without addition of leaves, reaching 17.15 (T3) and 5.81 (T4) times higher, respectively. These results indicated that:water flooding can promote the decomposition of the leaves of the T. distichum; the decomposition of leaves under different water conditions did not significantly affect the phosphorus content in the soil; and the decomposition of the leaves of the T. distichum during flooding may increase the phosphorus content in the water. Therefore, it is necessary to collect the leaves of the T. distichum in the hydro-fluctuation belt in a timely manner in order to reduce the phosphorus load of the water body in the reservoir area as much as possible. 参考文献 相似文献 引证文献

三峡库区消落带立柳(Salix matsudana)生长及营养元素分配特征

PDF HTML阅读 XML下载 导出引用 引用提醒 三峡库区消落带立柳(Salix matsudana)生长及营养元素分配特征 DOI: 10.5846/stxb201811162485 作者: 作者单位: 三峡库区生态环境教育部重点实验室;重庆市三峡库区植物生态与资源重点实验室;西南大学生命科学学院,三峡库区生态环境教育部重点实验室;重庆市三峡库区植物生态与资源重点实验室;西南大学生命科学学院,攀枝花市旅游局,三峡库区生态环境教育部重点实验室;重庆市三峡库区植物生态与资源重点实验室;西南大学生命科学学院,三峡库区生态环境教育部重点实验室;重庆市三峡库区植物生态与资源重点实验室;西南大学生命科学学院,三峡库区生态环境教育部重点实验室;重庆市三峡库区植物生态与资源重点实验室;西南大学生命科学学院,三峡库区生态环境教育部重点实验室;重庆市三峡库区植物生态与资源重点实验室;西南大学生命科学学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家十三五重点研发计划（2017YFC0505305）；国家国际科技合作专项（2015DFA90900）；三峡后续工作库区生态与生物多样性保护专项项目（5000002013BB5200002）；中央财政林业科技推广示范资金项目（20170183） Growth and nutrient distribution characteristics of Salix matsudana in the hydro-fluctuation belt of the Three Gorges Reservoir Author: Affiliation: Key Laboratory of Eco-environments in Three Gorges Reservoir Region Ministry of Education,Chongqing Key Laboratory of Plant Ecology and Resources Research in Three Gorges Reservoir Region;School of Life Sciences,Southwest University,Key Laboratory of Eco-environments in Three Gorges Reservoir Region Ministry of Education,Chongqing Key Laboratory of Plant Ecology and Resources Research in Three Gorges Reservoir Region,School of Life Sciences,Southwest University,Panzhihua Tourism Bureau,Key Laboratory of Eco-environments in Three Gorges Reservoir Region Ministry of Education,Chongqing Key Laboratory of Plant Ecology and Resources Research in Three Gorges Reservoir Region,School of Life Sciences,Southwest University,Key Laboratory of Eco-environments in Three Gorges Reservoir Region Ministry of Education,Chongqing Key Laboratory of Plant Ecology and Resources Research in Three Gorges Reservoir Region,School of Life Sciences,Southwest University,Key Laboratory of Eco-environments in Three Gorges Reservoir Region Ministry of Education,Chongqing Key Laboratory of Plant Ecology and Resources Research in Three Gorges Reservoir Region,School of Life Sciences,Southwest University,Key Laboratory of Eco-environments in Three Gorges Reservoir Region Ministry of Education,Chongqing Key Laboratory of Plant Ecology and Resources Research in Three Gorges Reservoir Region,School of Life Sciences,Southwest University Fund Project: National keypoint research and invention program in 13th Five-Year, No. 2017YFC0505305; the Program for International S&T Cooperation Projects of China, No. 2015DFA90900; the Program for the Follow-on Work of the Three Gorges: Ecological and Biological Diversity Conservation in the Reservoir Region, No. 5000002013BB5200002; The Forestry Extension Project of China entral Finance, No. 20170183. 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:立柳因良好的耐淹性常被用于三峡库区消落带的植被重建。为探讨立柳如何通过营养元素的积累和分配来适应库区消落带冬季水淹，于2015年5月对三峡库区消落带植被修复示范基地内3个采样带（175 m，170 m和165 m）中立柳的生长状况以及叶、枝条和根的营养元素含量特征进行分析。结果表明：（1）经过3个水淹周期后，随着水淹强度的增加，立柳的株高、基径和冠幅均受到一定的抑制；但与种植初期相比，3个采样带中立柳的株高、基径和冠幅均显著增加，且生长状态良好。（2）立柳各器官中营养元素含量均处于正常水平，但水淹抑制了根中N、P的积累，促进了Fe和Mn的积累；水淹显著降低了海拔165 m处立柳叶和枝条中Ca含量、枝条和根中Cu和Zn的含量。（3）水淹胁迫导致N、P、K、Mg元素更多地在叶中积累，而Cu和Zn在枝条中大量积累，这有利于退水后植株的光合合成以及恢复生长；Fe、Mn元素在根中大量积累，其对根系正常生理可能造成的干扰值得进一步关注。研究表明，在不同的水淹胁迫梯度下，立柳可针对性地调整其营养元素积累和分配方式，保持植株正常的生长状态，对维护三峡库区消落带生态系统的正常结构和功能具有重要作用。但在库区消落带植被恢复和重建工作中，需加强170 m以下海拔区域立柳生长的监测和研究。 Abstract:After the completion of the Three Gorges Dam, a hydro-fluctuation belt with a range of 30 m and an area of about 350 km2 was formed. The unique anthropogenic hydrological regime of the Three Gorges Dam has had significant negative impacts on the reservoir's ecosystem. A large number of native flooding-intolerant plants living within the belt have gradually died due to off-season flooding, which negatively affected the ecosystem structure and function of the hydro-fluctuation belt. Therefore, vegetation reconstruction and restoration in the Three Gorges Reservoir (TGR) is urgent; previous studies have shown that Salix matsudana has been used for vegetation reconstruction due to its flood resistance abilities. The nutritional accumulation and distribution of plants in a certain degree can reflect eco-physiological processes, and can serve as a crucial indicator of the structure and function of the local ecosystem. In order to explore how S. matsudana adapts to the winter flooding in the hydro-fluctuation belt of the TGR through the accumulation and distribution of nutrients, the growth status and the nutrient content in leaves, branches, and roots of S. matsudana in three sampling belts (at altitudes of 175 m, 170 m, and 165 m) of the vegetation remediation demonstration base of the TGR were measured in May 2015. The results showed that:(1) After three flooding cycles, the plant height, base diameter, and crown width of S. matsudana were inhibited by the increase of flooding intensity; however, compared with the initial stage of planting, the plant height, base diameter and crown width of S. matsudana in the three sampling belts were significantly higher, and the growth status was good as well. (2) The nutrient content in all organs of S. matsudana were maintained at normal levels, but flooding reduced the content of N and P in roots and increased the Fe and Mn content. In addition, winter flooding resulted in a significant decrease in the content of Ca in S. matsudana leaves and branches and the content of Cu and Zn in the branches and roots at an altitude of 165 m. (3) Under flooding stress, N, P, K, and Mg elements accumulated more in the leaves, while Cu and Zn accumulated in the branches, which is beneficial for photosynthetic rates and recovering growth of plants after water withdrawal. While winter flooding leads to higher accumulation of Fe and Mn elements in the roots, this disturbance to normal root physiology deserves further attention. Studies have shown that under different flood stress conditions, S. matsudana can adjust the accumulation and distribution of nutrients in a targeted manner to ensure a normal growth state. However, in this study of vegetation restoration and reconstruction in the water-fluctuating zone of the reservoir, we found that it is necessary to strengthen the monitoring and research of sustainable growth of S. matsudana at altitudes below 170 m. 参考文献 相似文献 引证文献

三峡库区消落带落羽杉与立柳林土壤微生物生物量碳氮磷动态变化

三峡库区消落带落羽杉与立柳林土壤微生物生物量碳氮磷动态变化

The Stability of Tailings Dams under Dry-Wet Cycles: A Case Study in Luonan, China

Instability of tailings dams may result in loss of life and property and serious environmental pollution. The position of the tailings dam’s phreatic line varies due to continuously changing factors such as rainfall infiltration and discharge of tailings recycling water. Consequently, tailings dams undergo dry-wet (DW) cycles, accompanied by the appearance of a hydro-fluctuation belt. With dynamic development of the physical and chemical properties of tailings sand in the hydro-fluctuation belt, the stability of tailings dams is uncertain. In this study, direct shear tests were performed on the tailings sand collected from a tailings dam in Luonan, through which the shear strength parameters of tailings sand with DW cycles were obtained. Then, a method that efficiently calculates the phreatic line of the tailings dam under DW cycles was proposed. In addition, based on laboratory tests and the proposed phreatic line calculation method, we used a finite element program to evaluate the stability of the tailings dam that experienced different DW cycles. The calculated results showed that: (i) the damage effects of DW cycles gradually weakens as the number of DW cycles increases. (ii) With the increasing of DW cycles, the maximum displacement of the tailings dam increases from 0.5 mm to 22 mm, and the area of maximum displacement expanded mainly at the toe of the tailings dam and at the front edge of the hydro-fluctuation belt. (iii) The tailings dam safety factor decreases continuously with increasing DW cycles. This study may provide a novel method for analyzing the stability of tailings dams under different DW cycles as well as an important reference for improving tailings dam stability.

Migration and Transformation of Mercury in Unsubmerged Soil and Sediment at One Typical Forest Reservoir in Southwest China

Mercury (Hg) has been regarded as a global pollutant due to its volatility and toxicity. The sediment in the reservoirs or lakes is an important compartment for Hg methylation and it has also been considered as a sensitive area of Hg. In this study, a typical forest reservoir surrounding by evergreen broad-leaved forest in Chongqing of southwest China was selected to investigate the migration and transformation of Hg in unsubmerged soil and sediment. The unsubmerged soil and sediment were also replaced to each other to observe the dynamics of THg and TMeHg concentrations in equilibrium processes. The results were as follows:① The THg and TMeHg mean concentrations in Dahonghai reservoir water were (1.89±0.72) ng·L-1 and (0.13±0.04) ng·L-1, respectively, which were lower than the first class water quality standards in environmental quality standard of China and other reservoirs or lakes, implying that this study area did not affect by Hg pollution. Meanwhile, the THg and TMeHg mean concentrations in unsubmerged soil and sediment were also lower than those in other reservoirs or lakes. ② Seasonal variations of THg and TMeHg concentrations in reservoir water and soil were both observed higher in warm seasons, and more obvious variations occurred for TMeHg which probably influenced by meteorological parameters, such as, temperature and rainfall. ③Compared with unsubmerged soil, the THg and TMeHg mean concentrations in sediment were both elevated, suggesting the sediment was an important sink of Hg. While, the sediment would be a source of Hg (especially TMeHg) with a high THg and TMeHg level. ④ The THg and TMeHg mean concentrations in unsubmerged soil and sediment after situ replacement were equilibrated with ambient soil in a short time (one or two months), implying the hydro-fluctuation belt of reservoir promoting the geochemical cycle of Hg.

A nonstationary parameter model for the sandstone creep tests

The rock masses of hydro-fluctuation belt experience seepage pressure following impoundment in the Three Gorges Reservoir; its creep behaviors are significant for reservoir bank slopes. To study the creep behaviors under seepage pressure (0, 1.45, and 1.75 MPa), we performed creep tests using representative landslide sandstone in the Three Gorges Reservoir and investigated the sandstone creep behaviors under the coupling effects of seepage pressure and stress. Previous researches on rocks have usually regarded the creep constitutive parameter as a constant; however, in this study, a nonlinear, nonstationary, plastic-viscous (NNPV) creep model which can describe the curve of sandstone creep tests is proposed. The rock-creep parameters under three levels of seepage pressure were identified, and theoretical curves using the NNPV model agreed well with the experimental data, indicating that the new model cannot only describe the primary creep and secondary creep stages under varying seepage pressures but also, in particular, perfectly describes the tertiary creep stage. Finally, the sensitivity of the NNPV model parameters is analyzed, and the result shows that the nonstationary coefficient α and the nonlinear coefficient m are main parameters affecting the tertiary creep stage.

落羽杉根系有机酸与NSC代谢对三峡消落带水位变化的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 落羽杉根系有机酸与NSC代谢对三峡消落带水位变化的响应 DOI: 10.5846/stxb201706091053 作者: 作者单位: 西南大学生命科学学院,西南大学生命科学学院,西南大学生命科学学院,西南大学生命科学学院,西南大学生命科学学院,西南大学生命科学学院,西南大学生命科学学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家国际科技合作专项（2015DFA90900）；中央高校基本科研业务费专项资金资助（XDJK2017D104）；三峡后续工作库区生态与生物多样性保护专项项目（5000002013BB5200002）；中央财政林业科技推广示范资金项目（20170183，渝林科研2016-8）；国家十三五重点研发计划（2017YFC050530502） Responses of root organic acids and nonstructural carbohydrates of Taxodium distichum to water-level changes in the hydro-fluctuation belt of the Three Gorges Reservoir Author: Affiliation: School of Life Sciences, Southwest University,School of Life Sciences, Southwest University,School of Life Sciences, Southwest University,School of Life Sciences, Southwest University,School of Life Sciences, Southwest University,School of Life Sciences, Southwest University,School of Life Sciences, Southwest University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为探究三峡库区消落带水位变化下落羽杉根系有机酸和非结构性碳水化合物（NSC）的响应特征，以适生木本植物落羽杉为对象，在消落带原位环境中设置对照-SS（海拔175 m，试验期间无水淹）、MS（海拔170 m，中度水淹胁迫）和DS（海拔165 m，深度水淹胁迫）3个处理，分别于海拔170 m和165 m退水时采集样品，测定并分析根系有机酸和NSC的变化。结果表明：（1）库区水淹对落羽杉基径无显著影响，仅有DS组明显抑制了高生长，落羽杉生长能较积极地响应库区水淹。（2）库区水淹对落羽杉侧根和总根有机酸的影响一致，侧根有机酸代谢作用优于主根。与SS组相比，MS组根系有机酸含量增高，DS组根系有机酸含量降低，除部分根系酒石酸、苹果酸、柠檬酸变化达到显著水平外，其余有机酸均无显著变化。（3）库区不同强度水淹对落羽杉根系NSC有不同程度的影响。与SS组相比，MS组可溶性糖无显著变化，淀粉、NSC含量显著增加，但总根NSC在水淹前与水淹后无明显差异；形成鲜明对比的是，DS组显著降低了可溶性糖、NSC含量，对淀粉无显著影响，且水淹后总根NSC显著低于水淹前。（4）相关分析表明，主根、总根草酸、苹果酸、柠檬酸及侧根、总根莽草酸分别与淀粉、NSC间表现出显著相关性（P<0.05）。研究结果表明，在三峡库区消落带水淹胁迫下，落羽杉根系有机酸与NSC代谢联系紧密。通过维持一定的根系淀粉含量，保持植株正常的有机酸代谢水平，较好地适应三峡库区消落带生境。 Abstract:Along the Three Gorges Dam reservoir on the Yangtze River in China, water levels fluctuate between 145-175 m annually, which has resulted in severe ecological problems, such as the degradation of vegetation and a decrease in biodiversity. In recent years, many efforts have been made to restore the vegetation in water-level-fluctuating zones. Some flood-tolerant species have been selected through pot experiments; however, only a few of these flood-tolerant plants survived after being planted in the hydro-fluctuation zones, bringing new challenges to rebuild vegetation in these areas. Chronic submergence is one of the major factors limiting the survival of plant species in the Three Gorges Reservoir. Previous studies showed that the root metabolism of organic acids and nonstructural carbohydrates (NSC) played an important role in the plant's response to flooding. However, it is still unclear how the root metabolism of organic acids and NSC in adaptable plants responds to water-level changes in the hydro-fluctuation belt of the Three Gorges Reservoir. In this study, Taxodium distichum, a flood-tolerant plant, was planted at three elevations:the control-SS (175 m above sea level, abbreviates as ASL), prolonged moderate submergence-MS (170 m ASL) and prolonged deep submergence-DS (165 m ASL) in the reservoir riparian region of Zhong County, Chongqing. Organic acid and NSC content was measured and analyzed after collection during de-submergence of MS and DS. The results showed that:(1) There was no significant difference in the base diameter of T. distichum and the height was inhibited only by DS, indicating that the height and the base diameter of T. distichum could positively respond to water-level changes in the riparian zone. (2) The organic acids in lateral roots showed a trend consistent with that of the total root. The root organic acid content was higher in MS and lower in DS than that in SS. Except for tartaric acid, malic acid, and citric acid in some roots, there were no significant differences in the remaining organic acids. (3) Soluble sugar did not significantly change, whereas starch and NSC content was significantly higher in MS than in SS. However, the NSC content of the total root did not change after being flooded. In contrast, the content of soluble sugars and NSC was significantly lower, while starch content did not differ significantly in DS from that in SS. On the other hand, the NSC in total roots reduced to some extent after flooding. (4) Correlation analysis showed that the content of starch and NSC was negatively correlated with the oxalic acid content of taproots and total roots, whereas the NSC displayed a strong and positive correlation with the concentration of malic acid, citric acid of the taproot and total root, and shikimic acid of the lateral and total root. The results indicated that there was a close relationship in root metabolism between organic acids and NSC of T. distichum. With a sufficient amount of starch and the organic acid metabolic levels similar to those in the control, T. distichum could adapt well to the water-level-fluctuating zones of the Three Gorges Reservoir. 参考文献 相似文献 引证文献

三峡库区消落带不同水淹强度下池杉与落羽杉的光合生理特性

PDF HTML阅读 XML下载 导出引用 引用提醒 三峡库区消落带不同水淹强度下池杉与落羽杉的光合生理特性 DOI: 10.5846/stxb201704150673 作者: 作者单位: 三峡库区生态环境教育部重点实验室，重庆市三峡库区植物生态与资源重点实验室，西南大学生命科学学院,三峡库区生态环境教育部重点实验室，重庆市三峡库区植物生态与资源重点实验室，西南大学生命科学学院,三峡库区生态环境教育部重点实验室，重庆市三峡库区植物生态与资源重点实验室，西南大学生命科学学院,三峡库区生态环境教育部重点实验室，重庆市三峡库区植物生态与资源重点实验室，西南大学生命科学学院,三峡库区生态环境教育部重点实验室，重庆市三峡库区植物生态与资源重点实验室，西南大学生命科学学院,三峡库区生态环境教育部重点实验室，重庆市三峡库区植物生态与资源重点实验室，西南大学生命科学学院,三峡库区生态环境教育部重点实验室，重庆市三峡库区植物生态与资源重点实验室，西南大学生命科学学院 作者简介: 通讯作者: 中图分类号: 基金项目: 重庆市林业重点科技攻关项目（渝林科研2016-8）；中央财政林业科技推广示范项目（渝林科推[2017-12]）；国家林业局天然林保护工程管理中心项目（2016-01）；国际科技合作专项（2015DFA90900）；重庆市研究生科研创新项目（CYB16066） Photosynthetic characteristics of Taxodium ascendens and Taxodium distichum under different submergence in the hydro-fluctuation belt of the Three Gorges Reservoir Author: Affiliation: Key Laboratory of Eco-environment in the Three Gorges Reservoir Region of the Ministry of Education, Chongqing Key Laboratory of Plant Ecology and Resources Research in the Three Gorges Reservoir Region , School of Life Sciences, Southwest University,Key Laboratory of Eco-environment in the Three Gorges Reservoir Region of the Ministry of Education, Chongqing Key Laboratory of Plant Ecology and Resources Research in the Three Gorges Reservoir Region , School of Life Sciences, Southwest University,Key Laboratory of Eco-environment in the Three Gorges Reservoir Region of the Ministry of Education, Chongqing Key Laboratory of Plant Ecology and Resources Research in the Three Gorges Reservoir Region , School of Life Sciences, Southwest University,Key Laboratory of Eco-environment in the Three Gorges Reservoir Region of the Ministry of Education, Chongqing Key Laboratory of Plant Ecology and Resources Research in the Three Gorges Reservoir Region , School of Life Sciences, Southwest University,Key Laboratory of Eco-environment in the Three Gorges Reservoir Region of the Ministry of Education, Chongqing Key Laboratory of Plant Ecology and Resources Research in the Three Gorges Reservoir Region , School of Life Sciences, Southwest University,Key Laboratory of Eco-environment in the Three Gorges Reservoir Region of the Ministry of Education, Chongqing Key Laboratory of Plant Ecology and Resources Research in the Three Gorges Reservoir Region , School of Life Sciences, Southwest University,Key Laboratory of Eco-environment in the Three Gorges Reservoir Region of the Ministry of Education, Chongqing Key Laboratory of Plant Ecology and Resources Research in the Three Gorges Reservoir Region , School of Life Sciences, Southwest University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为探究三峡库区消落带原位人工种植的池杉（Taxodium ascendens）和落羽杉（Taxodium distichum）在该特殊生境下的适应机制，设置了浅淹（SS，海拔175m，对照）、中度水淹（MS，海拔170m）和深度水淹（DS，海拔165m）3个水淹处理组，测定了两树种在连续4个周期性水淹处理后的光合响应过程，并采用直角双曲线模型、非直角双曲线模型、直角双曲线修正模型和指数模型进行拟合，比较各模型拟合结果差异并选出最优模型，通过最优模型来分析水淹后落干期两树种的光合生理变化。结果表明：（1）不同模型间的光响应曲线拟合结果存在差异（P<0.05）。综合分析可知，4种模型中，指数模型是拟合两树种光响应曲线的最优模型，更符合植物的生理学意义。（2）两树种的光响应曲线有相似的变化规律，光合速率（Pn）的表现均为DS组 > MS组 > SS组。（3）中度水淹和深度水淹两树种的最大净光合速率（Pnmax）、表观量子效率（α）、光饱和点（LSP）均高于浅淹，而光补偿点（LCP）则显著降低。以上结果说明落干生长期两树种对强光和弱光的利用能力增强，水淹对两树种的光合潜力有一定的促进作用，这可能与其遭受水淹胁迫后的自我调节能力和光合补偿机制有关。由此表明，当生境发生不良变化时，植物的适应性变化往往表现为沿着有利于光合作用最大化的方向发展。 Abstract:After the completion of the Three Gorges Dam Project, the water level of the Three Gorges Reservoir Area (TGRA) fluctuated between 145m a.s.l. in summer and 175m a.s.l. in winter. These extreme water fluctuations along with an annual 30m water-level drawdown have led to the formation of the hydro-fluctuation zone around the reservoir, turning the terrestrial ecosystem into a wetland experiencing winter flooding every year. Under these water fluctuation conditions, the richness and diversity of the vegetation decreased and soil erosion was exacerbated, which further damaged the ecological structure and function of the riparian ecosystem of the reservoir area. The effective way to solve this problem is to restore the riparian vegetation artificially. Understanding the photosynthetic adaptation mechanism of water-tolerant species in the hydro-fluctuation zone is of great importance to undertake vegetation restoration in the TGRA. In order to research the adaptation mechanism of the species suitable to the hydro-fluctuation belt of the TGRA, we designed the following three water regimes:periodic shallow submergence (SS, 175m), moderate submergence (MS, 170m), and deep submergence (DS, 165m). Li-6400 portable photosynthetic measurement system was used to test the light response curves of photosynthesis of Taxodium ascendens and Taxodium distichum after four cycles of submergence, in situ, in the TGRA. The light response curves were fitted and analyzed using the rectangular hyperbola model, the non-rectangular hyperbola model, the rectangular hyperbola modified model, and the exponential equation model. The optimal model was screened out from the four models by analyzing proximity between the simulated and measured values of photosynthetic parameters, and then it was used to analyze the photosynthetic characteristics of the two species under different submergence conditions. Results showed that:(1) The fit of different models was significantly different. The exponential equation model was the best model for the light response curve in accordance with the physiology of the two species; (2) The light response curves of the two species showed similar trends in variation, and along with an increase in the intensity of submergence, the photosynthetic rate of the two species also increased; (3) The maximum photosynthetic rate, apparent quantum yield, and light saturation point of the two species growing under both deep and moderate submergence conditions were higher than that in shallow submergence, while the light compensation point of the two species decreased significantly in deep submergence conditions. These results suggest that the utilization capacity of both low light and high light of the two species were improved after submergence. Submergence also stimulated the photosynthetic potential of the two species, which may be related to the positive self-adjustment ability and the photosynthetic compensation of the two species after submergence stress. This also indicates that when the habitat is stressed, plants often adapt themselves to maximize photosynthesis. Thus, it is appropriate to use these two species for reconstructing the vegetation in the hydro-fluctuation belt of the TGRA. 参考文献 相似文献 引证文献

The effects of the reverse seasonal flooding on soil texture within the hydro-fluctuation belt in the Three Gorges reservoir, China

PurposeThe formation of the large hydro-fluctuation belt at the altitude of 145–175 m, following the construction of the Three Gorges Dam, developed from the terrestrial system in the Three Gorges reservoir. This research mainly concerned the effects of the resultant reverse seasonal flooding on soil texture.Materials and methodsFour field experimental plots were designed with sample belts and quadrats at the head, middle, and tail sections of the reservoir area. Stratified soil samples were collected, followed by analysis of soil structure and soil grain size of the collected samples.Results and discussionThe reverse seasonal flooding significantly changes texture and nutrient of riparian soil. The percentages of silt and clay formations were greatest at the lower hydro-fluctuation belt, followed by the middle and upper hydro-fluctuation belt, respectively. The percentage of silt and clay particles at 150 m was greater than that of 170 m by 18.12%. Conversely, the percentage of sand particles at the upper hydro-fluctuation belt ranked the highest, and followed by the middle and lower hydro-fluctuation belt, respectively. The percentage of sand particles at 170 m was higher than that at 150 m by 19.72%. Soil texture type changed with increasing altitude gradient, from silt loam, loam, then to sandy loam. Reverse seasonal flooding also promotes silt and clay permeation, and deposition from surface soil to subsurface soil, increasing homogeneity in grain structure between soil layers. This change in soil texture is associated with changes in soil nutrients. The content of soil organic matter, total nitrogen, total phosphorus, and total potassium varied significantly among soil texture types, with loam having the highest soil nutrient concentration and sandy loam having the lowest.ConclusionsThe reverse seasonal flooding promotes the deposition of clay and silt within the hydro-fluctuation belt, inducing the total texture change of loam to silt loam. However, the structures and attributes of soil texture varied along the altitude gradient, as the exposed and submersed season and time span of riparian soil changed with the increase of altitude.