Aquatic-terrestrial Ecotone Research Articles

Patterns and drivers of organic carbon in hydromorphic soils across inland aquatic-terrestrial ecotones at the global scale

The aquatic-terrestrial ecotones of inland waters, including rivers, lakes, and reservoirs, are subject to occasional, recurrent, or even permanent flooding and play a vital role in the carbon cycles of aquatic ecosystems. However, the patterns and drivers of soil organic carbon in aquatic-terrestrial ecosystems have not been clearly documented on a global scale. To address this knowledge gap, we constructed a database of organic carbon content of 1970 globally distributed aquatic-terrestrial ecotone soils and utilized a random forest model to measure the primary drivers at global scale. We found that the average soil organic carbon content was 26, 33, and 18 g kg−1, and the mean soil organic carbon stock was 24.95, 22.38, and 30.66 t ha−1 for the aquatic-terrestrial ecotones of rivers, lakes, and reservoirs, respectively. Notably, the soil organic carbon content in lake ecotones was significantly higher than in river and reservoir ecotones. However, reservoir ecotones stored the highest soil organic carbon compared to lake and river ecotones. The random forest model explained 52 %, 49 %, 58 %, and 28 % variations of soil organic carbon content across all sites, river, lake, and reservoir ecotones, respectively. Soil physiochemical properties exert more pronounced effects across all ecotone types than climate factors when predicting soil organic carbon in global aquatic-terrestrial ecotones. However, it is noteworthy that the primary drivers of soil organic carbon content vary according to ecotone type. For river and lake ecotones, nitrogen content emerges as the dominant factor regulating organic carbon content. Conversely, in reservoir ecotones, pH stands out as the primary driver for soil organic carbon content. Beyond nitrogen content and pH, the composition of silt and clay also proves pivotal in predicting soil organic carbon in aquatic-terrestrial ecotones. These findings underscore the critical determinants of soil organic carbon accumulation in global inland aquatic-terrestrial ecotones.

Functional and temporal facets of predation by marsh frogs across the aquatic–terrestrial ecotone of ponds and implications in the context of biological invasions

Abstract Freshwater vertebrate predators can exert trophic control over aquatic and littoral communities. Among these predators, post‐metamorphic anurans exhibit a biphasic trophic spectrum by foraging in both terrestrial and aquatic habitats. Many studies have described their diet through the classical taxonomic classification of prey. However, these singular diet habits imply a complex, time‐dependent, realised trophic niche in which predation pressure occurs over many consumers that fill diverse functional roles throughout the aquatic and terrestrial interface of ponds. Among anurans, marsh frogs (Pelophylax ridibundus) have been introduced outside their range in many countries and are now invading nationwide areas, particularly in western Europe. Focusing on their foraging specificities will therefore further the understanding of the trophic role of these alien taxa in pond environments that are highly colonised. We collected stomach contents from 761 marsh frogs from introduced populations in 19 ponds in southern France once a month over 4 months of their active period in the spring. The populations of marsh frogs were studied in a geographic area that was devoid of native water frogs and their origin tracks back as far as south‐eastern Europe (i.e., more than 1,000 km from the studied sites, as evidenced previously by genetic analyses). Marsh frogs exhibited generalist and opportunistic feeding strategies. The trophic niche was strongly asymmetrical and broader in the terrestrial environment than in the aquatic environment. However, predation occurred in communities of large freshwater macroinvertebrates and amphibians. Whereas the composition of the terrestrial diet exhibited strong seasonal variations, predation pressure was continuously exerted on the same aquatic organisms over time. Primary consumers and consumers at higher trophic levels frequenting aquatic benthic, vegetated, pelagic, and surface microhabitats were preyed upon, underlying the multidimensional extent of the predation spectrum. The diversified feeding strategies of alien marsh frogs highlight the extent of potential ecological control by predation on pond communities. Because of their wide trophic niche, they exert predation pressure on most pond organisms, triggering possible top‐down control of the overall aquatic communities. Our results show that the integration of the functional traits and microhabitats of consumed prey may aid in a better understanding of how predation by anurans may target specific components of pond communities. More particularly, this study raises concerns about the predatory role of introduced anurans in the context of biological invasions.

Plant communities regulated by water-level gradient in Caohai aquatic–terrestrial ecotones affect bacterial and fungal structures and co-occurrence networks

There is increasing awareness that vegetation dynamics play an important role in ecosystem stability and belowground microbial community diversity in wetlands. Studying plant–microbe dynamics and interactions under various conditions within lakes helps with the effective management of lake ecosystems by restoring ecosystem services. However, our knowledge about the response of microbial interactions to vegetation variation remains limited. We investigated how soil nutrients, enzyme activities, fungal and bacterial community diversity, and their network properties vary along the inundation gradient in aquatic–terrestrial ecotones of Caohai Lake in southwest China. Compared with the arid zone, the organic carbon and ammonia nitrogen contents in the severe inundation zone (SIZ) increased by 28.5% and 16.4%, respectively. Compared with the SIZ, the activities of cellobiohydrolase, β-1, 4-N-acetylglucosaminidase and leucine aminopeptidase in the dry–wet cycling zone increased significantly, increasing by 62.1%, 60.5% and 26.1%, respectively. Moreover, long inundation significantly reduced the abundance of fungi, diversity of bacteria, and size and complexity of their community co-occurrence networks. Microbial networks were smaller (fewer edges) and less stable (higher positive to negative edge ratios) in the SIZ. Aboveground vegetation regulated by water-level gradient can directly or indirectly affect microbial community structure and further interfere with the properties of bacterial and fungal co-occurrence networks. In conclusion, our findings suggested that plant communities regulated by water-level gradient play an important role in maintaining microbial diversity and co-occurrence network stability along the aquatic–terrestrial ecotone in Caohai Lake.

Applying synchronous fluorescence spectra with Gaussian band fitting and two-dimensional correlation to characterize structural composition of DOM from soils in an aquatic-terrestrial ecotone

Dissolved organic matter (DOM), the primary participant of carbon and nitrogen cycle, has a great impact on the behavior and fate of organic pollutants and heavy metals in eutrophic lakes. The dynamic spectral properties of DOM fractions were revealed in an aquatic-terrestrial ecotone under the different types of land use. Composite soil samples of different depths (0–20, 20–40 and 40–60 cm) were collected from four different land uses along a disturbed-impact gradient in Taihu Lake, China, i.e., grassland (GRL), forest land (FOL), paddy field (PAF), and vegetable field (VEF). DOM mainly consisted of tyrosine-like material (TYLF), tryptophan-like material (TRLF), microbial humic-like material (MHLF), fulvic-like material (FLF) and humic-like material (HLF) within all soil profiles, where TRLF was the dominant component (61.30 %) using synchronous fluorescence spectroscopy (SFS) combined with principal component analysis and Gaussian band fitting. Based on two-dimensional correlation spectroscopy with SFS and Fourier transform infrared, the variation order of DOM fractions was FLF → MHLF → HLF → TRLF → TYLF within the GRL soil profile, and MHLF exhibited an oppositive change with aliphatic OH and amide I in protein. The order of DOM fractions was MHLF → FLF → HLF → TYLF → TRLF within the FOL soil profile, and the change trend of MHLF remained oppositive with aliphatic OH and CO in ester. The order of DOM within the PAF soil profile fractions was TRLF → MHLF → HLF → TYLF → FLF, and changing trends of TYLF were oppositive to aliphatic OH, CH bending vibration, CH bending vibration and CO in ester. The order of DOM fractions was HLF → TYLF → TRLF → FLF → MHLF within the VEF soil profile, where the changing trend TYLF remained oppositive to aliphatic OH, CH deformations in lignin and aliphatic group and amide I in protein. This study may provide important support for alleviating lake water eutrophication or pollution.

Land use effects on soil phosphorus behavior characteristics in the eutrophic aquatic-terrestrial ecotone of Dianchi Lake, China

Growing evidence suggests that land use has widespread effects on soil phosphorus (P) cycling, which can contribute to plant growth and environmental impacts. P pool and P behavior characteristics have identified as potential indicators of soil nutrient cycling and functions. In this study, we investigated effects of different land-use types (farmland and ecological buffer zone) on soil P fractions (i.e., labile P, moderately labile P, organic P, apatite P, and residual P) and soil P sorption-release characteristics at three sampling sites in the eutrophic aquatic-terrestrial ecotone of Dianchi Lake, China. In addition, we also identified key soil physicochemical properties that were significantly related to soil P fractions and sorption-release characteristics. Different land use induced changes in soil P fractions and P stocks. Organic P pool showed a significant difference between FL and BZ in all sites and other P pools displayed the site-specific responses. Soils in buffer zone have higher P buffer capacity (higher maximum sorption capacity and lower degree of P saturation) in comparison with farmland. Moreover, soil buffer capacity was significantly correlated with soil labile P. These results suggest buffer zone in lakeside may act as sink of P in reducing soil P loss. However, higher labile P and very low C: Po ratios (<100) in all soil samples indicate there is large amount of available P accumulated in soils and soil P loss risk in the aquatic-terrestrial ecotone is still high. Redundancy analysis results showed that the soil key physicochemical properties (soil organic carbon, total nitrogen, exchangeable Fe and Al concentration, and pH) were closely related to soil P fractions and sorption-release characteristics. Therefore, we conclude that soil P fractions (especially labile P, organic P) and key soil physicochemical indices are useful indicators for assessing the behavior of P in soils induced by different land use in the eutrophic aquatic-terrestrial ecotone of lakes.

Distribution Characteristics and Pollution Assessment of Heavy Metals in Sediments of Zhushan Bay

The distribution characteristics of heavy metals in the columnar sediments of Zhushan Bay, Taihu Lake are studied. The Pearson correlation analysis and principal component analysis are carried out, and the pollution of heavy metals is evaluated. The highest mean concentration is found for zinc (Zn), followed by chromium(Cr), copper (Cu), nickel (Ni ), lead (Pb), arsenic (As), cadmium (Cd). The content of heavy metals in estuaries and open water is significantly higher than those in aquatic-terrestrial ecotone, and pollution accumulation occurs in the deep sediments. There is a significant positive correlation between Cr, Cu, Ni and Zn, which indicates their similar sources. The geoaccumulation index (Igeo) shows that Cr has the highest value, with moderately to heavily polluted. The pollution situation of the study area is improved after the desilting project of Taihu Lake, but the potential ecological risk index (RI) is still moderate to severe, among which Cd is the single factor that contributes the most to RI.

Aquatic Macrophytes are Seasonally Important Dietary Resources for Moose

Moose (Alces alces) are generalist herbivores, but are important aquatic-terrestrial ecotone specialists. Aquatic macrophytes are a high-quality food source for moose during summer, but the importance of aquatic food sources to the moose diet is difficult to study. We used stable isotope analysis of carbon and nitrogen from moose hooves and forage (terrestrial plants, aquatic macrophytes, and arboreal lichen) to assess the diet of moose at Isle Royale National Park, Michigan, USA, using Bayesian mixing models. We also evaluated the isotopic variability along chronologies of serially sampled hooves. Overall, our mixing models indicate that 13%–27% of the summer moose diet was aquatic in origin. Among moose that died during winter, body condition was impaired and hoof 15N was higher where aquatic habitats were sparse. Although isotope chronologies preserved in hooves could significantly enhance our understanding of ungulate foraging ecology, interpretation of such chronologies is presently limited by our lack of knowledge pertaining to hoof growth rate and seasonal growth variability related to age and health. Distinct isotopic values among terrestrial plants, aquatic macrophytes, and arboreal lichens indicate that continued methodological advances in stable isotope ecology will lead to more precise estimates of the contribution of aquatic feeding to moose population dynamics and other ungulates.

漓江水陆交错带土壤理化性质及其分布特征

PDF HTML阅读 XML下载 导出引用 引用提醒 漓江水陆交错带土壤理化性质及其分布特征 DOI: 10.5846/stxb201805091026 作者: 作者单位: 珍稀濒危动植物生态与环境保护教育部重点实验室,珍稀濒危动植物生态与环境保护教育部重点实验室,广西师范大学生命科学学院;珍稀濒危动植物生态与环境保护教育部重点实验室,珍稀濒危动植物生态与环境保护教育部重点实验室,珍稀濒危动植物生态与环境保护教育部重点实验室,珍稀濒危动植物生态与环境保护教育部重点实验室 作者简介: 通讯作者: 中图分类号: 基金项目: 广西自然科学青年基金项目（2016GXNSFBA380030）；广西壮族自治区中青年教师基础能力提升项目（ky2016YB062）；2017年度自治区级大学生创新创业训练计划项目（201411000124）；2017年度广西高校优秀教师出国留学项目 Soil physico-chemical properties and distribution characteristics in an aquatic-terrestrial ecotone of the Lijiang River, southwest China Author: Affiliation: Key Laboratory of Ecology of Rare and Endangered Species and Environmental Protection，Ministry of Education,,,,Key Laboratory of Ecology of Rare and Endangered Species and Environmental Protection，Ministry of Education 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:水陆交错带是水生生态系统与陆地生态系统之间的过渡带，是一种典型的生态交错区，承载着能量流动、物质循环和信息交换的重要作用。土壤作为水陆交错带系统的重要组成部分，是水陆交错带功能实现的基础之一。鉴于此，以桂林漓江水陆交错带纵向梯度（上游、中游、下游）不同植被覆盖条件下的土壤为研究对象，采用野外取样调查、实验分析与统计检验相结合，系统的分析了土壤理化性质及其分布特征，旨在为该区域退化生态系统恢复与重建提供依据。结果表明：11个土壤理化性质，其中5个指标（土壤含水量、全氮、全磷、速效氮和速效钾）在上游、中游和下游均差异性显著。不同梯度下的土壤理化性质的相关性及相关性大小也不尽相同，但在总体上存在一些较相似的变化规律，如上游、中游和下游的土壤容重和孔隙度均呈现显著负相关，土壤全磷和有机质与多数土壤化学性质呈显著正相关；土壤含水量在下游与多数土壤化学性质均显著相关，但在上游仅与土壤全磷显著负相关。PCA主成分分析表明，土壤容重、土壤孔隙度和土壤全磷含量的贡献均大于其他环境因子的平均贡献率，体现了它们是影响漓江水陆交错带土壤理化性质的重要环境因子。 Abstract:The aquatic-terrestrial ecotone is a transitional zone between aquatic and terrestrial ecosystems. It is a typical eco-transitional zone and plays an important role in energy flows, material circulation, and information transformation. Soil, as an important part of the aquatic-terrestrial ecotone, is one of the basic functional aspects of an aquatic-terrestrial ecotone. This study aimed to provide scientific guidance for the restoration of a degraded aquatic-terrestrial ecotone. To do so, a typical area of the aquatic-terrestrial ecotone of the Lijiang River, Guilin, southwest China were selected as the sampling site. We measured eleven soil physico-chemical properties, including the following soil chemical properties: soil organic matter (SOM), total nitrogen (TN), total phosphorus (TP), total potassium (TK), available nitrogen (AN), available phosphorus (AP), available potassium (AK), and soil pH, as well as the following soil physical properties: soil water content (SWC), bulk density (BD), and soil porosity (PS). We analyzed the relationships between the soil physico-chemical properties of different distributed community types by employing methods of field investigation and experimental testing using basic statistics including One-way ANOVA, the Tukey-Kramer HSD test, and Principal Component Analysis (PCA) across a longitudinal gradient (upstream, midstream, and downstream) in an aquatic-terrestrial ecotone of the Lijiang River. The results showed that SWC, TN, TP, AN, and AK have significant differences across the longitudinal gradient (upstream, midstream, and downstream) of aquatic-terrestrial ecotones. Although the correlations and the intensity of the correlations between soil physico-chemical properties across the gradient were different, there were some similarities. Of the soil physical properties, bulk density and soil porosity are significantly negatively correlated, while TP and SOM have a significant positive correlation with most of the soil chemical properties across the longitudinal gradient of the aquatic-terrestrial ecotone. Soil water content was significantly positive correlated with most of the soil chemical properties in the downstream region, but only had a significantly negative correlation with TP in the upstream region. A principal component analysis indicated that soil bulk density, soil porosity, and soil total phosphorus contributed more than the other environmental factors to PCA1 and PCA2, which were important predictors of the distribution of different community types in the aquatic-terrestrial ecotone of the Lijiang River. 参考文献 相似文献 引证文献

漓江水陆交错带植物叶性状对水淹胁迫的响应及经济谱分析

漓江水陆交错带植物叶性状对水淹胁迫的响应及经济谱分析

Fire and flood expand the floodplain shifting habitat mosaic concept

The floodplain shifting habitat mosaic concept suggests that habitat patch dynamics are influenced by hydrologic disturbances driven by flood pulses of sufficient power to initiate incipient motion of the substratum and maintain cut-and-fill alluviation of the channel and banks. However, floodplain habitat mosaics are subject to other important landscape-scale disturbance regimes. In the Rocky Mountains of the USA and Canada, fire also affects floodplain habitat patch composition. The floodplain exists at the intersection of disturbance regimes that shape the riverscape and those that shape the landscape. We extended the shifting habitat mosaic concept by examining the effects of multiple disturbance elements on habitat patch composition across the aquatic–terrestrial ecotone of the North Fork of the Flathead River, a free-flowing river in southeastern British Columbia, Canada, and northwestern Montana, USA. We used remotely sensed imagery, meteorological records, empirical and modeled rainfall-runoff data, extent and frequency of past wildfires, and anthropogenic landuse data for 1991–2013 to examine the relationships among hydrology, fire, landuse, geomorphic position, and floodplain habitat patch dynamics. Exploratory path analysis revealed that fire had the strongest total effect and stream power and geomorphic position had moderate total effects on the variability of floodplain habitat patch composition along the North Fork. These 3 factors explained 13 to 26% of the variance in floodplain habitat patch composition between study reaches across all years. We used graphical analysis to examine the locations and intensity of disturbance and recovery pathways across floodplain transition zones throughout the study period. Our results support the hypothesis that hydrologic and fire disturbances and recovery pathways maintain the shifting habitat mosaic across the floodplains of this river system.

Contrasting metacommunity structure and beta diversity in an aquatic‐floodplain system

Habitat connectivity and dispersal interact to structure metacommunities, but few studies have examined these patterns jointly for organisms across the aquatic–terrestrial ecotone. We assessed metacommunity structure and beta diversity patterns of instream benthic invertebrates, riparian carabid beetles (Order: Coleoptera; Family: Carabidae) and riparian spiders (Order: Araneae) at fifteen sites in a river‐floodplain system. Sampling took place over a three‐year period (2010–2012) in the Rhine‐Main‐Observatory LTER site on the Kinzig River, central Germany. This allowed disentangling the combined influence, and temporal variability, of habitat connectivity (i.e. between aquatic and terrestrial) and dispersal ability (i.e. between spiders and beetles, and aerial and aquatic dispersing invertebrates) on the dominant paradigms structuring these metacommunities. We found mostly consistent differences in the manner that metacommunities were structured between groups, with lower levels of variability explained for beetles compared to the other groups. Beetles were consistently structured more by turnover than nestedness components, with greater beta diversity than expected by chance and a minor spatial compared to environmental signal emerging with variance partitioning. Conversely, spiders and benthic invertebrates had lower beta diversity and greater nestedness than null expectation, and a clearer spatial signal controlling metacommunity structure. Our results suggest varying levels of mass effects and species sorting shape river‐floodplain metacommunities, depending on habitat connectivity and dispersal ability. That is, greater connectivity and lower fragmentation along the river compared to the terrestrial zone promoted mass effects, and differences in overall dispersal ability and mode (i.e. active and passive) for instream and riparian communities shifted paradigms between mass effects and species sorting.

漓江水陆交错带不同淹没区植物多样性与土壤特征研究

漓江水陆交错带不同淹没区植物多样性与土壤特征研究

Nitrous oxide emissions from Phragmites australis-dominated zones in a shallow lake

Nitrous oxide (N2O) emissions from Phragmites australis (reed) – dominated zones in Baiyangdian Lake, the largest shallow lake of Northern China, were investigated under different hydrological conditions with mesocosm experiments during the growing season of reeds. The daily and monthly N2O emissions were positively correlated with air temperature and the variation of aboveground biomass of reeds (p < 0.05), respectively. The N2O emissions from reeds were about 45.8–52.8% of that from the sediments. In terms of the effect of hydrological conditions, N2O emissions from the aquatic-terrestrial ecotone were 9.4–26.1% higher than the submerged zone, inferring that the variation of water level would increase N2O emissions. The annual N2O emission from Baiyangdian Lake was estimated to be about 114.2 t. This study suggested that N2O emissions from shallow lakes might be accelerated by the climate change as it has increased air temperature and changed precipitation, causing the variation of water level.

Response of Terrestrial-Aquatic Palm Ecotone (Morichal) to Anthropogenic Disturbance in the Orinoco Lowlands

The study tested the assumption that the effect of land-use changes on hydrological dynamics and edaphic features of an aquatic-terrestrial ecotone have led to vegetational patchiness and decrease primary productivity (NPP). On the basis of the depletion of a groundwater-fed stream, three study sites corresponding to interrupted, intermittent and permanent streams were selected throughout the ecotone in the Sunsunes catchment (Orinoco basin, Venezuela). To describe the human impact on land cover, patchiness, biodiversity, hydrological and edaphic features, NPP and nutrient availability, we use structural and functional approaches. Hydrological (i.e., duration of inundation and maximum inundation height), soil chemical (e.g., Ca concentration, available phosphorous, soil organic matter) and physical (i.e., water-filled pore spaces) features were the best predictors of anthropogenic disturbance. In the ecotone, the tree species invasion from well-drained savannas increased woody cover as described by a stretched exponential model. Groundwater drawdown in the interrupted and intermittent streams increased with 74 and 34 colonizer species from well-drained savannas. The NPP of the ecotonal vegetation along the interrupted stream (909 g C/m2/yr) was a higher sink as compared to the intermittent and permanent streams (580 g C/m2/yr). Anthropogenic stress along with natural disturbance resulted in a decline in the system´s functioning. In contrast to hydrology, the effect of the nutrient addition (i.e., liming and phosphorous) on the carbon accumulation by species was not significant. Therefore, the functional response of the system was more sensitive to hydrology regime. The results indicate impact on the ecotones occurred in short term, and that vulnerability to climate is crucial of groundwater-dependent vegetation.

Assessment of Heavy Metal Contamination of Wetland Soils from a Typical Aquatic–Terrestrial Ecotone in Haihe River Basin, North China

AbstractSurface soils were collected in the aquatic–terrestrial ecotone (ATE) of Yongnianwa wetland, downstream of Haihe River basin of North China in June of 2007. Samples were subjected to a total digestion technique before they were analyzed for total concentrations of Cr, Cu, Ni, Pb, and Zn to investigate their pollution levels in the ATE. The contamination index, integrated contamination index, geoaccumulation index, toxic units, and sum of toxic units were adopted to assess the heavy metal contamination levels and ecotoxicity, respectively. The results showed all the selected element concentrations in upland soils of the ecotone were relatively higher than those in the lowland soils. No Cr pollution was observed in all soil samples, but almost all samples were slightly polluted by Cu, Ni, Pb, and Zn except for Site 1. The contamination indexes and geoaccumulation indexes consistently presented no contamination for Site 1 and slight contamination for other sites. The ΣTUs increased from lowland to upland, but the whole level of toxicity in this ecotone was relatively low.

Heavy metals in wetland plants and soil of Lake Taihu, China

Properties of vertical distribution of soil near water bodies are vary considerably from those of land and may greatly affect the transportation of heavy metals in wetlands. Vertical distributions of heavy metals (Cr, Cd, Cu, Pb, and Zn) in the soil of aquatic-terrestrial ecotone (ATE) of Lake Taihu, China, and in wetland plant tissues were studied. Generally, concentrations of heavy metals decreased with increasing depth in the top 40-cm cores and then increased slightly with increasing depth. This investigation indicated that concentrations of Cd, Cr, Pb, and Zn exceeded the geochemical background values in the Taihu Lake area. Concentrations of Cd at all depth soil columns exceeded the Environment Quality Standard for Soils of China. Correlation analysis showed that concentrations of Zn, Cr, Cd, and Pb correlated significantly with one another, suggesting that they had the same origin. The concentration of Cu was negatively correlated with root biomass, which may explain the lower concentration of copper in the soil cores. The dominant plants of the wetland were Phragmites australis and Ludwigia prostrata, and heavy metal accumulated primarily in the root tissue. The general order was root > rhizome > stem > leaf, whereas in L. prostrata, leaf was the main tissue for Cr accumulation. Both P. australis and L. prostrata had the highest concentration factor (CF) to Cu, and CF was 20.3 and 15.8, respectively. Aquatic-terrestrial ecotone plants are more effective in controlling Cu pollution than other heavy metals. This will be very significant for ATE reestablishment near Cu-polluted sites.

Vertical and temporal distribution of nitrogen and phosphorus and relationship with their influencing factors in aquatic-terrestrial ecotone: a case study in Taihu Lake, China

Vertical and temporal distributions of N and P in soil solution in aquatic-terrestrial ecotone (ATE) of Taihu Lake were investigated, and the relations among N, P, ORP (oxidation reduction potential), TOC, root system biomass and microorganism were studied. As a whole, significant declines in TN, NO 3 −-N, DON (dissolved organic nitrogen) and TP concentration in soil solution have occurred with increase of the depth, and reached their minima at 60 cm depth, except for NH 4 +-N, which increased with depth. The concentration of TP increased gradually from spring to winter in the topsoil, the maximum 0.08 mg/L presented in the winter while the minimum 0.03 mg/L in spring. In the deeper layer, the concentration value of TP fluctuated little. As for the NO 3 −-N, its seasonal variation was significant at 20 cm depth, its concentration increased gradually from spring to autumn, and decreased markedly in winter. Vertical and temporal distribution of DON is contrary to that of NO 3 −-N. The results also show that the variation of N and P in the percolate between adjacent layers is obviously different. The vertical variation of TN, TP, NO 3 −-N, NH 4 +-N and DON is significant, of which the variation coefficient of NO 3 −-N along the depth reaches 100.23%, the highest; while the variation coefficient of DON is 41.14%, the smallest. The results of correlation analysis show that the concentration of nitrogen and phosphorus correlate significantly with TOC, ORP, root biomass and counts of nitrifying bacteria. Most nutrients altered much from 20 to 40 cm along the depth. However, DON changed more between 60 and 80 cm. Results show that soil of 0–60 cm depth is active rhizoplane, with strong capability to remove the nitrogen and phosphorus in ATE. It may suggest that there exists the optimum ecological efficiency in the depth of above 60 cm in reed wetland. This will be very significant for ecological restoration and reestablishment.

Aquatic habitat diversity along the corridor of an Alpine flood plain river (Fiume Tagliamento, Italy)n

Habitat structure and diversity were investigated at multiple scales along the Tagliamento River (NE Italy) to analyze the spatial and temporal configuration of the aquatic habitat templet in a complex alluvial river corridor in the European Alps. A geomorphic approach was employed to determine floodplain structure and channel configuration using aerial photographs and digitized maps. Structural, thermal, and chemical variables were sampled monthly for one year in 3-km long study sections within six distinct geomorphic reaches along the longitudinal continuum. Aquatic habitat heterogeneity and complexity was quantified along the longitudinal dimension (corridor scale), within geomorphic reaches (floodplain scale) and within floodplain water bodies (within-habitat scale). Four major types of aquatic habitats were distinguished: surface-connected channels (SC), alluvial channels (AC), tributary channels (TC), and isolated standing water bodies (ISO). The first 3 types included primary, secondary, and tertiary branches plus backwaters. Active floodplain width was greatest in the island-braided lower floodplain (reach IV), which also exhibited the highest values for aquatic habitat area per river km, aquatic-terrestrial ecotone length per river km, within-floodplain thermal heterogeneity, and aquatic habitat diversity. Principal component analysis (PCA) clearly distinguished lotic from standing waters along the primary axis and substrate gradients (both longitudinally between floodplains and laterally within floodplains) on the secondary axis. PCA applied to 21 chemical variables illustrated a downstream increase in floodplain-scale spatio-temporal heterogeneity along the river corridor. Total environmental variance is considerably enhanced by the superimposition of longitudinal changes (corridor scale) on lateral changes within geomorphic reaches (floodplain scale). This study clearly demonstrated the high levels of structural complexity and habitat diversity that are possible in Alpine rivers, with implications for the important role of environmental heterogeneity in sustaining functional integrity.