Natural Riparian Zones Research Articles

Assessment of the Divergent Influence of Natural and Non-Seasonal Hydrological Fluctuations on Functional Traits and Niche Characteristics of Plant Guilds along the Xiangxi River, China

The reservoir water level fluctuation zones (RWLFZs) and the natural riparian zones (NRZs) are two riparian ecosystems with dramatically opposite hydrological rhythms that notably influence the plant guilds. However, little is known about the discrepancies of the functional traits and niche characteristics of plant guilds in the RWLFZs and NRZs under different flooding rhythms. The aims of this study were to assess the divergent influence of natural and non-seasonal hydrological fluctuations on functional traits and niche characteristics of plant guilds. The results showed that 78 vascular plant species were identified in the riparian zones of the Xiangxi River basin. The dominant species were annuals in the two riparian ecosystems and their percentage increased temporally from 65.79% in the NRZs to 67.34% in the RWLFZs. Compared with the NRZs, the specific leaf area, vegetation coverage and the aboveground biomass in the RWLFZs significantly increased by 74%, 27% and 19.6%, respectively, while the water-use efficiency of the RWLFZ decreased by 59.6% and there was no significant difference in the net photosynthetic rate between them, which showed that annuals in the RWLFZs adopted the R adaptation strategy of being fast-growing with a short lifespan and quickly acquiring and investing resources by altering leaf morphology, including expanding the leaf area. The Simpson dominance index of RWLFZs was significantly higher than that of NRZ. Thus, counter-seasonally hydrological alterations had significant effects on functional traits of dominant species in the RWFLZs. Moreover, the highly adaptable and widely distributed species with larger niche breadths and high important values usually had a higher niche overlap value in the RWLFZs than in the NRZs, which showed that the competition in the plant communities after experiencing anti-seasonal flooding was much more intraspecific than interspecific and would facilitate the expansion of species niches. Our findings imply that the species with large niche breadths and high important values should be prioritized in ecological restoration efforts in the newly formed hydro-fluctuation zones of the TGR.

Nearshore fish diversity changes with sampling method and human disturbance: Comparing eDNA metabarcoding and seine netting along the Upper St. Lawrence River

Aquatic ecosystems are deteriorating, with the most impacted species and populations having insufficient data to inform conservation and management. Monitoring aquatic biodiversity and evaluating anthropogenic impacts typically rely on time-consuming, logistically challenging, and invasive methods (e.g., seining, trawling or electrofishing). Environmental DNA (eDNA) methods have been touted as an important advancement, especially in fish biodiversity assessment. We compare eDNA metabarcoding and seining methods along a 350 km section of the Upper St. Lawrence River (Canada) for: i) mapping the distribution of invasive and threatened fish species, ii) describing species richness and fish community structure, and iii) assessing the effect of habitat type and anthropogenic degradation of riparian zones on fish community composition and richness. eDNA detected more fish species (n = 67) than seining (n = 38) and revealed higher fish diversity in samples adjacent to intact, natural riparian zones. Fish assemblages were influenced by habitat type according to analyses using eDNA, while no effect of any environmental predictor on fish community composition was found using seining. Altogether, our results support eDNA metabarcoding as a powerful, complementary tool in fish monitoring and testing for the impacts of anthropogenic disturbances.

重庆主城河岸带植物群落功能性状与土壤理化性质的关系

PDF HTML阅读 XML下载 导出引用 引用提醒 重庆主城河岸带植物群落功能性状与土壤理化性质的关系 DOI: 10.5846/stxb202202160368 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 重庆市科技兴林项目（2021-9）；西南大学生命科学学院科学基金项目（20212005406201）；宁夏回族自治区重点研发计划项目（2020BFG03006）；中央林业改革发展资金科技推广示范项目（渝林科推2020-2） The relationship between plant functional traits and soil physicochemical properties in the riparian zones of downtown Chongqing Author: Affiliation: 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:基于功能性状视角开展植物群落与环境关系的研究有助于揭示植物的适应策略。然而，目前关于城市河岸带植物群落功能性状的研究较少。为此选取10项植物功能性状指标和14项土壤理化性质指标，探究重庆主城3种生境类型河岸带（自然型河岸带（NRZ）、农耕主导型河岸带（FRZ）和开发建设主导型河岸带（BRZ））植物群落功能性状与土壤因子特征及互作机制。结果表明：（1）与NRZ生境相比，FRZ生境中的土壤速效磷、速效钾和氧化还原电位和BRZ生境中的土壤含水量显著偏高（P<0.05）；FRZ和BRZ生境中的土壤pH值和全磷含量显著偏高，而土壤有机质、全钾和全氮含量显著偏低（P<0.05）。（2）与NRZ生境相比，FRZ生境中的比根长和比根表面积显著较高，茎干物质含量和叶干物质含量显著较低；BRZ生境中仅茎干物质含量显著较低（P<0.05）。（3）冗余分析结果表明，影响各生境类型河岸带植物群落功能性状的土壤因子不同，NRZ生境为土壤容重、含水量和硝态氮，FRZ生境为土壤铵态氮、全磷和有机质，BRZ生境则是土壤含水量、温度和速效磷。研究发现与自然状态相比，农业和建筑类型的人为干扰导致重庆主城河岸带生境发生改变，植物群落通过权衡功能性状组合的策略提高对生境变化的适应性。 Abstract:Studying the relationship between plants and the environment through plant functional traits is of help to reveal plants' adaptation strategies. At present, most researches on the relationship between plant functional traits and environmental factors have mainly focused on the terrestrial ecosystems. Very few similar studies have been carried out in the riparian ecosystems. Riparian vegetation is a prerequisite for riparian ecosystems to function properly, while maintaining healthy watercourse and landscape connectivity. Therefore, our study selected 10 plant functional trait indices and 14 soil physiochemical property indices to explore plant community functional traits, soil factor characteristics and interaction mechanisms of three habitat types (natural riparian zone (NRZ), farming riparian zone (FRZ) and building riparian zone (BRZ)) within the riparian zones of downtown Chongqing. The results showed that:(1) compared with the NRZ habitat, the soil available phosphorus, available potassium and redox potential in the FRZ habitat and the soil moisture in the BRZ habitat were significantly higher (P<0.05). The soil pH value and total phosphorus content were significantly higher in FRZ and BRZ habitats, while soil organic matter, total potassium and total nitrogen content were significantly lower (P<0.05). (2) In comparison to the NRZ habitats, the specific root length and specific root surface area in the FRZ habitats were significantly higher, and the stem dry matter content and leaf dry matter content were significantly lower. Only the stem dry matter content was significantly lower in the BRZ habitats (P<0.05). (3) The results of redundancy analysis showed that the soil factors which affected the functional traits of riparian plant communities in different habitat types were different. For the NRZ habitats, the influencing factors were soil bulk density, soil moisture and nitrate nitrogen. For the FRZ habitats, the influencing factors were soil ammonium nitrogen, total phosphorus and organic matter. For the BRZ habitats, the influencing factors were soil moisture, soil temperature, and available phosphorus. This study found that in comparison to the natural riparian state, the anthropogenic disturbance of agriculture and structural engineering related projects led to changes in the riparian habitats of downtown Chongqing, and that the plant community improved its adaptability to various habitats through trade-off combinations of functional traits. 参考文献 相似文献 引证文献

Drone-based investigation of natural restoration of vegetation in the water level fluctuation zone of cascade reservoirs in Jinsha River

The reservoir water level fluctuation zone (WLFZ) is a new and fragile ecosystem that is gaining attention with the construction of large and medium-sized hydropower plants. Compared to the natural riparian zone, it has a greater drop in water level, longer inundation time, more intense impact from alternating wet and dry conditions, and a wider impact on ecological security. The Jinsha River basin is located in the upper reaches of the Yangtze River in China, and several world-class large-scale hydropower projects with dam heights over 100 m have been built, forming a large area of reservoir WLFZ, however, due to the short time since their construction, there are few related studies. In this paper, fixed sample plots were set up in the typical WLFZs of each large reservoir in the Jinsha River basin. In response to the problem of the precipitous terrain and poor accessibility of the Jinsha River basin, a combination of small UAV surveys and field research in July 2020 was used to draw vegetation cover maps and extract topographic data for each site, and quantitatively analyse the community composition, dominant species types, area, coverage, spatial distribution patterns and environmental factors of tolerant vegetation using spatial superposition analysis, neural network models, landscape pattern indices and typical correlation analysis. The results showed that the original drought-tolerant vegetation in the arid river valley WLFZ has evolved into amphibious herbaceous vegetation, with trees and shrubs disappearing and species composition tending to be simpler. 44 species of plants, mainly in the Asteraceae and Gramineae families, were extant, 61% of which were also reported in the Three Gorges Reservoir WLFZ. The water level variation showed convergence in the natural screening process of suitable species in the WLFZ. Moreover, even in the dry valley WLFZs, flood stress showed a more significant filtering effect on vegetation species than drought stress. The vegetation in the WLFZ showed an obvious band-like aggregated distribution along the water level elevation gradient, and the vegetation coverage along the flooding gradient is as follows: upper part of the WLFZ >> middle part > lower part, and mainly concentrated in the gentle area with slope less than 35°. Flooding stress, drought stress and soil substrate deficiency were the main limiting factors for vegetation recovery in the WLFZ. The vegetation restoration of the WLFZ should be adapted to local conditions, and the dominant role of native species should be emphasized. At the early stage of the restoration of the WLFZ, native species should be selected for artificial planting to accelerate the formation of vegetation cover, and gradually advance downwards along the gradient of water level elevation, while for areas of the WLFZ with slopes greater than 35° and large topographic relief, biological engineering measures should be used to help plant establishment, and after a certain stable cover has been formed, natural restoration should be the main focus.

Response of Soil Fauna to the Shift in a Riparian Landscape along an Urban-Rural Habitat Gradient.

Urbanization is accelerating worldwide, resulting in drastic alterations of natural riverbanks, which seriously affects the ecological functions and services of riparian landscapes. Our understanding of how anthropogenic activities influence soil animal communities within riparian zones is scarce. The soil fauna represents an important biotic component of the soil ecosystem and greatly contributes to soil structure and fertility formation. We investigated the richness, abundance, diversity, and distribution of soil animal groups, including macro- and mesofauna, in different riparian landscapes along an urban–rural habitat gradient. In natural riparian zones with permeable revetments, the soil fauna was richest and most abundant, mainly because of the low levels of human disturbance and the more suitable habitat conditions. Different soil animal groups responded differently to revetment type and distance from the water flow. The hygrophilous soil mesofauna, requiring a more humid environment, was more sensitive to shifts in revetment types, the location on the riverbank, and the seasons. In summer, when precipitation in the study area was highest, the abundance of the hygrophilous soil mesofauna was significantly higher than in autumn. Distance from the water flow significantly affected the abundance of the hygrophilous soil mesofauna. Our results demonstrated that hygrophilous soil mesofauna can serve as a good indicator in riparian zones, reflecting the hydrological conditions. We also observed interactions between revetment type and distance from the water flow; the distance effect was stronger in the natural riparian zone with a permeable revetment type. Our results highlight the importance of anthropogenic effects on soil ecosystem processes and functions in riparian landscapes, and the necessity of protecting and retaining the natural riverbank and native vegetation patches in riparian landscape planning and construction.

Photosynthetic acclimation of riparian plant Distylium chinense to heterogeneous habitats

Distylium chinense is an evergreen dominant shrub with strong adaptability under heterogeneous habitats, including natural riparian zone (NRZ), anti-seasonal water level fluctuation zone (ASWLFZ), and no water level fluctuation zone (NWLFZ) in the Three Gorges Reservoir Region (TGRR) in China. In order to understand the photosynthetic ecological adaptability and habitat adaptation strategies of D. chinense under heterogeneous habitats, its photosynthesis and chlorophyll fluorescence parameters were investigated. The results showed that photosynthetic characteristics were significantly different among heterogeneous habitats (p<0.05). The PSII potential activity and PSII maximum photochemical efficiency (Fv/Fm) of D. chinense in the ASWLFZ were the highest among heterogeneous habitats. Non-photochemical quenching coefficient (qN) in the NWLFZ was higher than that in the NRZ and ASWLFZ (p<0.05). Stepwise regression analysis showed that water use efficiency and stomatal conductance were correlated with specific leaf area (SLA), leaf area and leaf dry weight. Regression curve fitting and canonical correspondence analysis revealed that light intensity, soil water content, air humidity and temperature were the main factors affecting photosynthetic characteristics and leaf functional traits. Our results evidenced that D. chinense adapted to the high water content and low light intensity environments, especially in the valley waterfall habitats, by increasing stomatal conductance and net photosynthetic rate, reducing SLA and maintaining moderate qN and Fv/Fm with adopting a profligate water use pattern to improve photosynthetic productivity. Therefore, D. chinense has a wide photosynthetic acclimation to different environments, which provided baseline information for the conservation and ecological restoration in the newly formed hydro-fluctuation zone and other similar degenerative riparian ecosystem.

Influence of Vineyard Vegetational Borders on Western Grape Leafhopper (Erythroneura elegantula Osborn), its Egg Parasitoids (Anagrus spp.) and Generalist Insect Predators

Studies have shown that vegetational diversity in or around cropping systems can enhance naturalenemy abundance, although the impact on herbivores is less certain. We studied the influence of vineyardvegetational borders on density of the western grape leafhopper, Erythroneura elegantula, its majorparasitoids, Anagrus spp., and two generalist predators, Orius spp. and Leptothrips mali. Two studyvineyards had planted, perennial flowering hedgerows, one bordered a natural riparian zone, and onehad a sparse border of native trees. From April to September 2007, we counted leafhopper nymphs andadults of Anagrus spp., Orius spp. and L. mali within 10 m of the border, and at additional 20 m intervalsup to 90 m. At two sites with a diverse border, leafhopper density was stable nearest the border; at otherdistances leafhopper density decreased between the first and second generations. This effect was notseen at the sparse border site. Anagrus spp. density was enhanced at one site with a diverse border, butonly late season. There was no border effect on the generalist insect predators, by site or early vs. lateseason. Regression analysis showed a positive relationship between leafhopper and Anagrus spp. density,suggesting that the parasitoids were responding to higher leafhopper density. We conclude that, dependingon the nature of the border vegetation, there can be an effect on leafhopper nymphal density, but in thisstudy there is no evidence that it was due to natural enemies.

C4 herbs dominate the reservoir flood area of the Three Gorges Reservoir

Dam operations can dramatically degenerate riparian vegetation. To improve the restoration practices of reservoir riparian vegetation, it is important to understand which and how a dominant species physiologically and ecologically maintain high fitness in this type of ecosystems. We explored the compositional change of riparian plants during the long-term flood-dry-flood cycle in the reservoir flood area (RFA) of the Three Gorges Reservoir Area (TGRA), China. In total 769 vascular plant species (belonging to 415 genera in 122 families) existed in the study area before damming (prior to 2006, i.e. the natural riparian zone). Following damming (2008–2018), plant species diversity rapidly declined, with only 51 species identified in 2018 (45 genera in 22 families). Before damming, perennial herbs, annual herbs and shrubs co-dominated the study area. After damming, the proportion of shrubs decreased significantly, and the proportion of annuals to total plants increased by 20%. Alien invasive species proportion increased from 5% to 18%. Notably, the proportion of C4 species increased significantly from 7% to 31%. Ten of the 16 dominant species in RFA since 2015 were C4 Poaceae species. Our study indicates that dam construction could cause severe biodiversity loss of riparian plants and draw alien species invasion. Besides, C4 herbs would dominate the RFA. A higher photosynthetic rate could help C4 plants grow faster to cope with the nitrogen deficiency and short growth cycles in RFA. Hence, screening C4 herbs for vegetation restoration might aid in maintaining biodiversity and ecosystem functions in flood-dry-flood reservoir flood areas.

The influence of revetment types on soil denitrification in the adjacent tidal urban riparian zones

Riparian zones adjacent to revetments, as the last position of the entire riparian, are the last barrier to intercept runoff nitrogen pollution. They are also the areas where hyporheic exchange occurs when soil is submerged by river water. Revetments can be classified into impervious revetments and permeable revetments according to their permeability. It has been realized that impervious revetments are not conducive to exchange between rivers and riparian zones. Tidal riparian zones undergo water level changes more frequently than normal riparian zones. Thus, revetments in tidal riparian zones may have a greater impact on nitrogen cycling. However, the quantitative influence of revetment types on nitrogen removal in adjacent tidal urban riparian zones is not clear, resulting in the lack of scientific support for the revetments construction. Removal of nitrogen from riparian zones primarily occurs through plant uptake, microbial immobilization, and denitrification. However, nitrogen will be released into soil again after plants die or microorganisms decompose. While denitrification can completely remove nitrogen through transferring nitrate (NO3−) into gaseous nitrous oxide (N2O) and dinitrogen (N2). In this study, we used three revetment types (permeable concrete pile revetments (PR), impervious masonry stone revetments (IR), and no revetments (NR)) as examples to quantify the effects of revetment types on soil denitrification in adjacent tidal urban riparian zones at three distances from the revetments (0.3 m, 0.6 m, 1.0 m) by measuring the soil (0–20 cm) denitrification potential (DP) and N2O production rates (N2OR). Results indicated that compared with soil denitrification (0.32 ± 0.06 mg kg−1h−1) in natural riparian zones (NR), PR could significantly improve it (0.97 ± 0.07 mg kg−1h−1), while IR significantly inhibited it (0.23 ± 0.04 mg kg−1h−1) in the adjacent tidal urban riparian zones (P < 0.01). Changes in soil properties caused by revetment types accounted for the differences in soil denitrification. Soil organic carbon (SOC) was a main direct chemical factor, and soil texture was a main indirect physical factor. Based on these results, revetments construction did not necessarily inhibit soil denitrification in natural riparian zones, and priority should be given to building permeable revetments to improve the soil denitrification provided by the riparian ecosystem.

Effects of revetment type on the spatial distribution of soil nitrification and denitrification in adjacent tidal urban riparian zones

Revetments between the river channels and riparian zones are important factors in the modification of urban riparian zones structure, particularly in zones adjacent to them. Although there have been many studies on the stability of revetments in tidal urban riparian zones, the quantitative effects of revetments on the nitrogen cycling in riparian zones adjacent to them remain unclear. Tidal riparian zones undergo more frequent river–soil exchanges than normal riparian areas, thus, revetments may have a greater impact on the nitrogen cycling. Nitrification and denitrification are two important biotransformation processes of nitrogen cycling. In this study, we used soil (depths of 0–20, 25–45, and 55–75 cm) nitrification and denitrification rates as indicators to study the effects of revetment type on the spatial distribution of soil nitrogen cycling in tidal urban riparian zones adjacent to three revetments (permeable concrete pile revetments (PR), impervious masonry stone revetments (IR), and no revetments (NR)) at three distances (0.3, 0.6, and 1.0 m). Our results indicated that compared with natural riparian zones (NR), PR significantly improved soil nitrification and denitrification rates, while IR significantly improved soil nitrification rates but decreased denitrification rates (P < 0.05), which were totally different from the general perception, particularly in impervious revetments. Revetment type mainly affected the temporary inundation zones (0–20 cm). For example, in the temporary inundation zones, the variation in soil denitrification rates was 14.49 mg kg−1 h−1, while in the frequent inundation zones (25–45 cm) and the permanent inundation zones (55–75 cm), the variations were 3.26 and 2.94 mg kg−1 h−1, respectively. Soil compaction was probably the main constraint factor for soil nitrification in natural riparian zones, soil organic carbon (SOC) and nitrogen availability were probably the main constraint factors for soil denitrification adjacent to impervious revetments. In order to take full advantage of the structural characteristics of impervious revetments and permeable revetments, the combination of impervious revetments in permanent inundation zones and permeable revetments in temporary inundation zones could be optimally designed to enhance soil nitrogen cycling function of tidal urban riparian zones during revetment construction.

Combined effects of physical environmental conditions and anthropogenic alterations are associated with macrophyte habitat fragmentation in rivers - Study of the Danube in Serbia

We hypothesize that the physical features of river habitats and anthropogenic hydromorphological alterations influence macrophyte communities and lead to habitat fragmentation. Sampling included 1081 contiguous survey units positioned in the main channel and side arms along 588km of the Danube River, along its middle course. To identify habitat fragments, Multivariate Regression Tree analysis (MRT) was applied on macrophyte and environmental data. Indicator species analyses were combined with MRT. To identify habitat fragments on a scale larger than final MRT groups, we set thresholds for an MRT complexity parameter. We identified 20 fine, 7 medium, and 3 large scale habitat fragments. Damming was the main fragmentation agent. Macrophyte communities show continuous variation at all scales of habitat fragmentation. High species diversity indicates major anthropogenic alteration of the river's hydrology and decline of the natural riparian zone. Future studies of the macrophyte communities, and their habitat fragmentation must include more factors (e.g. nutrient status, physicochemical quality of the water, etc.), as well as assessment of the importance of tributaries.

三峡库区支流生境因子对库区蓄水的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 三峡库区支流生境因子对库区蓄水的响应 DOI: 10.5846/stxb201701180150 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: 国务院三峡办三峡后续工作库区生态与生物多样性保护专项（5000002013BB5200002-1） Response of habitat factors to reservoir impoundment in tributaries in the Three Gorges Reservoir Region 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 Science,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 Science,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 Science,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 Science,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 Science,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 Science,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 Science,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:三峡水库的运行调度，使库区支流形成了截然不同的3种河段类型：完全受水库蓄水影响的145m回水段（完全河段），既受蓄水影响又受自然洪汛影响的145-175m回水段（双重河段）以及不受蓄水影响的大于175m的自然河流段（自然河段）。为明确库区蓄水对河流不同河段生境因子的影响程度及差异，对三峡库区36条重要支流的254个河段进行河流生境调查，进行不同河段下生境指标的因子分析，并进一步分析水文情势自然性与不同河段各生境因子的相关关系。结果表明，植被状况对3种不同河段来说均为重要生境因子，但受三峡水库蓄水影响，完全河段植被结构不完整；受库区蓄水影响，完全河段与双重河段及自然河段相比，流速流态状况、表层覆盖物状况、河岸带宽度、湿润率等生境因子有明显改变；水文情势自然性对不同河段生境因子的影响不同。 Abstract:Water level management strategies specify that the impoundment of the Three Gorges Reservoir (TGR) starts from 145m asl in September to 175m asl in November. The water level is maintained for three months and then returned to 145m asl again in May. Consequently, three types of water-level-fluctuation zones appear along the Three Gorges Reservoir tributaries banks:(1) The area from the estuary to the 145-m backwater (completely-flooding reach), where the former natural riparian zone is submerged permanently since its elevation is below 145m asl; (2) the 145-m backwater area to the 175-m backwater area (double-flooding reach), which is affected by summer flooding from July to September as well as by impoundment from September to May; (3) the area above the 175-m backwater area (natural reach), which is not affected by reservoir water storage. In order to distinguish the influence of reservoir water storage on habitat factors in the different river reaches, we investigated the river habitats of 254 reaches in 36 major tributaries in the Three Gorges Reservoir area. Based on the results of these investigations, we used factor analysis to assess the 18 indicators on river hydrology, river morphology, and the water-level fluctuation zone habitat of different river habitats, and analyzed the relationship between the degree of flow regime naturalness and habitat factors in different reaches. The results showed that vegetation conditions are important habitat factors in three different types of sections. Affected by the impoundment of the Three Gorges reservoir, most riparian vegetation is herbaceous and flooding-tolerant, with nearly no trees or shrubs. Compared with the double reach and natural reach zones, the completely reach zone was subject to significant changes in the flow pattern, surface coverage, width of the buffer zone, and wetting rate. The effects of flow regime conditions on habitat factors in different river reaches differed. 参考文献 相似文献 引证文献

Submergence Tolerance and Germination Dynamics of Roegneria nutans Seeds in Water-Level Fluctuation Zones with Different Water Rhythms in the Three Gorges Reservoir.

The Three Gorges Dam features two water-level fluctuation zones (WLFZs): the preupland drawdown zone (PU-DZ) and the preriparian drawdown zone (PR-DZ). To investigate the vegetation potential of Roegneria nutans in WLFZs, we compared the submergence tolerance and germination dynamics in the natural riparian zone (NRZ), PU-DZ and PR-DZ. We found that the NRZ seeds maintained an 81.3% intactness rate and >91% germination rate. The final seed germination rate and germination dynamics were consistent with those of the controls. Meanwhile, the PU-DZ seeds submerged at 5 m, 10 m, 15 m, and 20 m exhibited intactness rates of 70.5%, 79.95%, 40.75%, and 39.87%, respectively, and >75% germination. Furthermore, the PR-DZ seeds exhibited intactness rates of 22.44%, 61.13%, 81.87%, and 15.36% at 5 m, 10 m, 15 m, and 17 m, respectively, and 80% germination. The germination rates of the intact seeds submerged >10 m were >80%. Finally, the intact seeds germinated quickly in all WLFZs. The high proportion of intact seeds, rapid germination capacity, and high germination rate permit R. nutans seeds to adapt to the complicated water rhythms of the PU-DZ and PR-DZ and indicate the potential for their use in vegetation restoration and recovery. Thus, perennial seeds can be used for vegetation restoration in the WLFZs of large reservoirs and in other regions with water rhythms similar to the Three Gorges Reservoir.

Is the Sosiani River Healthy? Investigating the Relationship between Water Quality Indicators and Macroinvertebrate Assemblages in the Sosiani River

The health of rivers is of great concern to governments and communities worldwide due to their important ecological functions. Numerous studies have established that water quality indicators have a positive effect on river health. However, only a few studies have examined equatorial rivers, and, to date, there has been no study on the Sosiani River in Kenya. As such, this study explored the health of the Sosiani River by considering how its aquatic macroinvertebrate assemblages were affected by various water quality parameters. The research considered whether there was a relationship between water quality indicators and macroinvertebrate assemblages in the Sosiani River. This knowledge is of paramount importance to the communities and decision makers of the Sosiani catchment, and Kenya as a whole, since there is need to understand the relationship between the water quality indicators and the health of the river in order to allocate resources for its rehabilitation and maintenance. This study examined 10 sites, nine being “test” sites and one a “reference” site. The study established a significant relationship between water quality parameters and macroinvertebrate assemblages. The sites with natural riparian zone vegetation conditions were found to have more Ephemeroptera, Plecoptera, and Trichoptera macroinvertebrates when compared to those without or with exotic vegetation. In terms of absolute numbers of surface aquatic macroinvertebrates, sites characterised by dense stream bank vegetation had more macroinvertebrates than those characterised by forest with eroded, bare stream banks. From the study, it was therefore concluded that Sosiani River is healthier at head waters where there was natural forests compared to downstream where there was plantations, intensive farming and urban area. The study recommends that more detailed studies classify macroinvertebrates to gunus level and include microinvertebrates, since this may give a more accurate assessment of the river’s health. The study further recommends that identification keys for East African macroinvertebrates be developed.

Contribution of alkaline phosphatase to phosphorus cycling in natural riparian zones in the Wangyu River running into Lake Taihu

Understanding phosphorus (P) cycling is essential to reducing algal blooms and other negative effects in water. However, few studies have investigated the contributions of alkaline phosphatase (APase) or alkaline phosphatase activity (APA) to P cycling in natural riparian zones. Here, seasonal and spatial development of plankton, P fractions, APA fractions, and fluorescence labeled enzyme activity were investigated in a natural riparian zone in the main diversion channel for water transfer into Lake Taihu. Plankton greatly benefited from APase, and APA production was their important advantage for P acquisition and proliferation. Fluorescence labeling varied greatly between species and seasons, indicating different adaptive strategies for dissolved organic P acquisition. Phytoplankton experienced severe P stress when they were the main APA producers in spring and summer, but bacteria were superior P competitors. During autumn and winter, free APA dominated, phytoplankton APA (phyt-APA) deceased because of low biomass or high dissolved reactive P (DRP) and bacterial APA (bact-APA) proportions were high. Bulk APA and DRP were negatively correlated for the entire data-set and during the productive seasons. Significant negative correlation was observed between phyt-APA and DRP in the lacustrine and wetland zones, but the situation was complicated for bact-APA, probably owing to organic carbon limitation.

Predicting fecal indicator organism contamination in Oregon coastal streams

In this study, we used publicly available GIS layers and statistical tree-based modeling (CART and Random Forest) to predict pathogen indicator counts at a regional scale using 88 spatially explicit landscape predictors and 6657 samples from non-estuarine streams in the Oregon Coast Range. A total of 532 frequently sampled sites were parsed down to 93 pathogen sampling sites to control for spatial and temporal biases. This model's 56.5% explanation of variance, was comparable to other regional models, while still including a large number of variables. Analysis showed the most important predictors on bacteria counts to be: forest and natural riparian zones, cattle related activities, and urban land uses. This research confirmed linkages to anthropogenic activities, with the research prediction mapping showing increased bacteria counts in agricultural and urban land use areas and lower counts with more natural riparian conditions.

Field Study of Riparian Zone along Sarawak River at Bintawa, Kuching

Natural riparian zones are increasingly valued in recent years as they provide a variety of beneficial functions to the environment and possess substantial economic value. In this regard, it is necessary to call for simultaneous protection of the environment and promotion of economic growth. In this writing, a field methodology is presented for the purpose of riparian wetland conservation; it is used to investigate the riparian health through studying vegetation cover, human activities and groundwater table. Healthy riparian zones can be achieved through the balancing of riverbank human activities with maintaining the functionality of wetlands, which can be done by assessing the groundwater level a nd the amount of lush vegetation. A functioning riparian zone is found with a mean of 12% human activities in the range of 0 to 17.86%, within an area along the water edge measuring 100 m x 100 m. It is only natural that the higher the percentage of the wetland vegetation that is flourishing, the more the riparian zone is functioning well.

Riparian buffer zones in intensive grassland agri-systems are not necessarily a refuge for high conservation value species

The appropriate management of natural riparian zones can provide numerous ecosystem services within an agricultural landscape, including the enhancement of regional biodiversity. Management of riparian zones has featured in Irish agri-environment schemes. We investigated the biodiversity of riparian field margins which had been fenced to provide water quality and biodiversity benefits. Surveys of plants, carabid beetles and spiders were conducted in typical habitat types that occur in riparian zones (grassland, scrub and woodland) on intensively-managed grassland systems in the south-east of Ireland.

Riparian buffer zones in intensive grassland agri-systems are not necessarily a refuge for high conservation value species

The appropriate management of natural riparian zones can provide numerous ecosystem services within an agricultural landscape, including the enhancement of regional biodiversity. Management of riparian zones has featured in Irish agri-environment schemes. We investigated the biodiversity of riparian field margins which had been fenced to provide water quality and biodiversity benefits. Surveys of plants, carabid beetles and spiders were conducted in typical habitat types that occur in riparian zones (grassland, scrub and woodland) on intensively-managed grassland systems in the south-east of Ireland. Distinct assemblages of plants and spiders were identified in each habitat type, but this was not the case for carabids. There were higher abundances of carabids and spiders in grass dominated riparian margins, while scrub dominated margins provided the highest regional carabid species richness. Riparian zones in intensively farmed areas in this study had a low incidence of specialised fauna. Proportional abundances or frequencies of riparian or wetland species for the surveyed flora and fauna were low when compared to the national flora and fauna and other similar studies. Management prescriptions in addition to those currently employed, such as limited grazing of fenced watercourse zones, may increase the abundance and/or species richness of some taxonomic groups. These results highlight the need for more appropriate management prescriptions and targeting of management actions if agri-environment measures aim to conserve farmland biodiversity in riparian zones.

Presence and patterns of alkaline phosphatase activity and phosphorus cycling in natural riparian zones under changing nutrient conditions

Phosphorus (P) is an important limiting nutrient in aquatic ecosystems and knowledge of P cycling is fundamental for reducing harmful algae blooms and other negative effects in water. Despite their importance, the characteristics of P cycling under changing nutrient conditions in shallow lakes were poorly investigated. In this study, in situ incubation experiments were conducted in a natural riparian zone in the main diversion channel used for water transfer into Lake Taihu (Wangyu River). Variations in microbial biomass, dissolved P fractions (organic and inorganic), and alkaline phosphatase activity (bulk APA and specific APA) were determined after incubation with and without the addition of P and nitrogen (N) (4 total water treatments: +P, +N, +NP, and control). Experiments were conducted during two seasons (late spring and early fall) to account for natural differences in nutrient levels that may occur in situ . Our results demonstrated that low levels of DRP may not necessarily indicate P limitation. Phytoplankton exhibited “serial N limitation with P stress” in May, such that chlorophyll a (Chl a ) increased significantly with N addition, while the limiting nutrient shifted to P in October and phytoplankton biomass increased with P addition. Phytoplankton contributed greatly to APA production and was significantly influenced by P bioavailability, yet high levels of bulk APA were also not necessarily indicative of P limitation. In contrast to phytoplankton, bacteria were less P stressed. As a consequence of enhanced utilization of dissolved reactive P (DRP) and dissolved organic P (DOP), +N treatment elevated APA significantly. By contrast, APA could be repressed to low values and phytoplankton converted a large portion of DRP to DOP with P addition. But this was not consistent with bacteria APA (bact-APA) in the absence or presence of abundant phytoplankton biomass. The correlation between bulk APA and DRP was good at separate sites and discrepant for the whole data set. Regulation of APA was demonstrated by an inverse hyperbolic relationship between bulk APA, specific APA, and DRP, with a transition from high to low activity occurring between 20 and 50 μg L -1 . This study provides a better understanding of how APA and P cycling change with nutrient perturbations in Lake Taihu system. The obtained results can help understanding the process of P cycling in water and providing a reference for nutrient control in the water transfer project.