Ecological Engineering最新文献

Plant introduction and hydrological management are essential strategies for near-natural wetland restoration. However, the combined effects of plant species and water depth on soil quality restoration remain poorly understood. The wetland ecosystem is crucial for Earth ecosystem health and sustainable development, but it faces challenges due to environmental change and human activities leading to soil quality degradation. In this study, we conducted a five-year near-natural restoration experiment covering approximately 2071 m² area in the Changbai Mountains region of northeastern China to assess the impact of plant species and water depth combinations on soil quality dynamics in reclaimed wetlands. Through an ecological engineering project, a meticulous controlled experiment was implemented to investigate the impact of different plant species and water depth combinations on soil quality in near-naturally restored wetlands. Over the five-year restoration period, we observed significant improvements in soil quality indicators, including pH, bulk density, soil organic carbon content, and labile organic carbon fractions. Soil pH and bulk density both showed a decreasing trend, with notable variations influenced by the combination of plant species and water depth. Particularly significant drops were observed in wetlands where Lythrum salicaria L. was introduced at 10 cm water depth and Iris wilsonii C. H. Wright was introduced at 30 cm water depth. Meanwhile, soil organic carbon content also appeared optimal restoration effects in the aforementioned combinations, highlighting the regulatory effect of these combinations on soil quality regulation. Linear regression modeling demonstrated a significant positive correlation between soil organic carbon and both above-ground and below-ground biomass, highlighting the interplay between vegetation dynamics and soil quality restoration. Our study provides valuable insights into the complex dynamics of soil quality restoration in reclaimed wetlands and underscores the importance of considering plant species-water depth combinations in restoration planning. By understanding these dynamics, restoration practitioners can make informed decisions to enhance the sustainability of wetland ecosystems and their invaluable ecological services.

Clogging has garnered growing interest as a significant operational and maintenance concern that affects the sustainable development and implementation of sub-surface flow (SSF) wetlands in wastewater treatment. The existing literature on clogging has been found to have limitations, as none of the studies have provided a comprehensive overview of the entire clogging process, starting from its initiation to remediation. In addition, very few works have addressed the models that were utilized to forecast the occurrence of system clogging. This study primarily focuses on the process of clogging, in widely used SSF wetland systems due to its negative impact on the lifespan of these systems. The article seeks to evaluate different forms of clogging and their developmental mechanisms, as well as the influencing factors. The work thoroughly examines the several techniques used to measure and evaluate clogging. The current review also encompasses the examination of several mathematical models used to predict the clogging of the system. Lastly, it also emphasizes the remediation methods required to resolve clogs. The main objective of this review is to bring all pertinent information on the clogging of SSF wetlands to the attention of prolific researchers with the goal of mitigating system clogging and establishing CW technology as a viable and sustainable alternative for wastewater treatment in the near future.

Wetland degradation is a major factor in the decline of biodiversity. Ecological engineering construction efforts, such as water diversion, have been the main method of wetland restoration. To reveal the effects of biodiversity conservation and ecological engineering construction in the semiarid regions of China, waterbird surveys were carried out 2 years before and 8 years after the construction of the ecological engineering project discussed in this study. The relationships among waterbirds and habitat landscape patterns, hydrology and vegetation conditions were analyzed. The impacts of ecological engineering on habitats and waterbird diversity were revealed. The results showed that (1) there were significant changes in land use, hydrological distributions and vegetation cover in the study area before and after the construction of the ecological project. The quality of waterbird habitats after the construction project was better than that before construction. However, there were fluctuating conditions. (2) The areas of water bodies and marshes were positively correlated with the number and diversity of waterbirds. However, increases in arable land, forestland, grassland and saline land can stress rare waterbirds. Changes in water levels, water body areas and vegetation cover in the conservation area all directly affect the availability of waterbird habitats, which can affect waterbird diversity. The wetland water level is the most important impact factor. (3) The annual water diversion volume in the study area is 5.00 × 10⁷ m³. When the water level is maintained at approximately 1.5-2.5m, the number of waterbirds remains stable. This study can provide scientific guidance and a methodological basis for the construction of ecological projects with waterbirds as protected targets.

Increased bank erosion is one of the most significant threats to agricultural stream ecosystems. However, it is challenging to ascertain whether bank restoration measures positively affect in-stream habitats and aquatic communities. This study evaluated three nature-based bank protection measures' short-term (2-year) effects on aquatic physical habitat quality and benthic macroinvertebrate communities in a headwater stream in agricultural areas. The results demonstrate that nature-based bank protection measures can significantly improve the quality of aquatic physical habitat in streams. The TPRW (timber piles + riprap + willow cuttings) and WTRW (waste tires + riprap + willow cuttings) measures exhibited the most pronounced improvement in the quality of aquatic physical habitat in streams. The diversity of benthic macroinvertebrates was the highest in the TPRW reach, and the seasons significantly affected the density of benthic macroinvertebrates. The Shannon-Wiener diversity index and Margalef's richness index were the most consistent with the changing trend of physical habitat quality and are effective indicators of the ecological effects of stream restoration measures in our study area. In this study area, TPRW is the preferred measure for streambank restoration of agricultural streams, and WTRW is the alternative measure. However, the ecological effects of WTRW need to be monitored over a more extended period to identify whether there is potential ecotoxicity in the process of weathering and decomposition.

Nature-based solutions (NbS) and soil bioengineering techniques have gained considerable attention due to their relevant hydrological functions and ability to mitigate slope instability. Live pole drains (LPD), a lesser-known NbS, have traditionally been deployed on slopes to drain the excess surface water and regulate the soil's water budget, making it a suitable technique for stormwater management and landslide prevention. However, neither the LPD performance as a plant-based drainage system nor its potential to regulate the soil-water budget through hydrological processes have been thoroughly studied. This paper presents a novel pilot, lab-based approach for testing the hydrological performance of LPD under different soil hydrological conditions. We built three different treatments and investigated their hydrological performance under multiple storm events. We explored how LPD regulate the soil-water budget by partitioning the water inputs (i.e., rainfall precipitation) into water outputs (i.e., surface runoff, subsurface flow, and percolation). The study revealed that LPD can effectively manage stormwater by draining excess runoff and buffering water in the soil, outperforming fallow soil. Subsurface flow and percolation were significantly higher under LPD treatments when compared to fallow ground, suggesting that the presence of an enhanced structure in the soil results in high soil hydrological performance. The presence of a secondary species with the LPD showed a more efficient hydrological performance than an LPD alone, which aligns with the current implementation of NbS fostering biodiversity. Antecedent soil moisture impacted the hydrological performance of LPD by altering the relative infiltration capacity of the soil and by potentially modifying the availability of channels for preferential flow. Our findings provide a sound basis for future research to improve our understanding of the hydrological performance of LPD for slope instability mitigation and encourage their reproduction and upscaling.

Przewalski's Naked Carp (Gymnocypris przewalskii) is a typical migratory fish species of the Qinghai Lake region (China). This study focused on the Gangbei Channel fishway located in the Shaliu River, a tributary of Qinghai Lake. A fish passage study was conducted during the peak of the upstream migration of G. przewalskii, and entry proportion and passage efficiency in the Gangbei channel fishway was monitored in real-time using PIT-Telemetry. A detailed hydraulic characterization of the fishway was done using a 3-D numerical model validated by in-situ measurements, and combined with empirical swimming ability data for the species. The results showed that: (1) the proportion of released G. przewalskii entering and passing the fishway were 13% and 5%, respectively; (2) discharge, fish body length, salinity, and diel period were key factors affecting the attempt rate of the G. przewalskii; (3) The critical swimming speed and sprint swimming speed at 50% of G. przewalskii reaching fatigue were 1.02 m/s and 1.91 m/s, respectively; (4) Based on the swimming ability of G. przewalskii and the hydraulic characteristics of the fishway, the flow velocity at the weir sections of the fishway exceeded the sprint swimming ability of G. przewalskii, creating a velocity barrier. Data derived from this study will be used to provide a more comprehensive theoretical basis and data reference for the eco-hydraulic reconstruction of pool-and-weir fishways providing an efficient upstream passage for the conservation of G. przewalskii and other species.

Understanding the long-term dynamics of saltmarsh vegetation and their driving factors is crucial for the restoration of degraded coastal wetlands. Reclamation and plant invasion, identified as the two most significant environmental contributors to saltmarsh vegetation degradation, profoundly influence the evolution of saltmarsh vegetation. However, the long-term impacts of reclamation and plant invasion on native saltmarsh vegetation remain unclear. This study utilized multi-source time series remote sensing data to quantify the long-term impacts of Spartina alterniflora invasion and reclamation on native saltmarsh vegetation in the Yangtze River estuary from 1985 to 2020. Unlike other studies, this study generated annual saltmarsh cover data using image composite, zoning classification, object-based phenology algorithm, and random forest algorithm, which largely addressed the problem that existing studies could not capture transient change and gradual change because of insufficient observation frequency. Results showed that: (1) Reclamation had resulted in a loss of 503.93 km² of native saltmarsh vegetation from 1985 to 2020, including 286.16 km² of Phragmites australis community and 217.77 km² of Scirpus spp. community; Spartina alterniflora invasion had resulted in a loss of 78.96 km² of native saltmarsh vegetation from 1985 to 2020, including 12.48 km² of Phragmites australis community and 66.48 km² of Scirpus spp. community; (2) Significant differences of spatial-temporal evolution patterns of native saltmarsh vegetation were observed under different degrees of Spartina alterniflora invasion and reclamation, including irrecoverable scenario under severe plant invasion and excessive reclamation, recoverable scenario under moderate degree of reclamation and plant invasion, and competitive scenario under plant invasion and without reclamation.; (3) From a long-term remote sensing perspective, spread limitation determined by reclamation intensity was a decisive factor in the evolution of Phragmites australis community in the study area, while interspecific competition between invasive Spartina alterniflora and Scirpus spp. determined the evolution of Scirpus spp. community. This study provides a theoretical basis and baseline for the protection strategies of native saltmarsh vegetation in the study area.

Landslide susceptibility assessment is a complex task due to the multitude of causative factors, spatial variability, data availability, modeling uncertainty, and validation issues. This study addresses these challenges by proposing two predictive models that hybridize support vector regression (SVR) with two evolutionary algorithms: grey wolf optimizer (GWO) and cuckoo search algorithm (CSA). These models were developed using an extensive geospatial database from northern Iran. Over the training phase, the basic predictive model, developed using SVR, was enhanced by incorporating the GWO and CSA algorithms, resulting in the development of two hybridized models: SVR-GWO and SVR-CSA. Over the validation phase, the performance and effectiveness of each hybridized model were compared to the standalone SVR using several metrics. Compared to the standalone SVR model, the hybridized models demonstrated significant improvement in generalization and predictive abilities. Despite non-significant difference between the performances of the SVR-GWO and SVR-CSA models, the SVR-GWO model demonstrated superior performance. This could be attributed to the GWO's capabilities, which included generating a variety of solutions, demonstrating robustness against noise and outliers, achieving faster convergence speed, and effectively interacting with SVR. This study highlighted that utilizing intelligence hybridized models can significantly enhance the balance between accuracy, robustness, and objectives compared to single models. This finding holds significant implications for ecological engineers tasked with designing and implementing solutions to mitigate the impact of shallow landslides on the environment and human communities. The predictive models developed in this study serve as valuable tools for these engineers, enabling them to identify high-risk areas and implement preventative measures. This interdisciplinary approach, which combines machine learning, optimization algorithms, and ecological engineering, highlights the potential for pioneering solutions in tackling complex environmental challenges, thereby standing as a testament to the power of innovation in driving progress in landslide susceptibility assessment.

Combined Sewer Overflow Treatment Wetlands (CSO wetlands) are designed to remove pollutants under stochastic events with variable hydraulic loads. Upgrading them with forced aeration promises to increase the effectiveness and resilience of the treatment. We have tested two vertical CSO wetlands with forced aeration (CSOa and CSOb) to understand the effects of aeration on CSO treatment. Both filter beds have 0.95 and 0.80 m of saturated layer. CSOa uses gravel as top filtering layer, while CSOb utilizes sand and an additional transition layer. Tracer tests were conducted in both filters with and without aeration to assess the impact of aeration on hydraulic performance. CSOa operated with four different aeration conditions, with the optimal condition tested on both filters for comparison. Samples were taken for analysis of global parameters and the redox potential was monitored online. In the tracer test, CSOa allowed to observe the mixing impact of aeration, which avoids any preferential path when influent entered the filter. The addition of a sand layer at the surface (CSOb) allows for a more even distribution of water on the top, which limits preferential flows when aeration is off. In both filters, the results showed that aeration increased the residence time and mixing degree (NTIS <3). Testing different aeration strategies revealed the dependence of dissolved pollutant removal on oxygen supply. In CSOa, the median outlet concentration varied from 23 to 6.4 mg.L⁻¹ in TSS, 153 to 32 mg.L⁻¹ total COD (CODt), 124 to 20 mg.L⁻¹ soluble COD (CODs) and 5 to 2.5 mg.L⁻¹ NH₄-N according to aeration strategy. The lower outlet concentrations were always under the highest aeration condition. Under the optimal condition (75 min on/15 min off), median removal of CSOa was 97% TSS, 85% CODt, 78% CODs and 75% NH₄-N. Besides COD and TSS, outlet concentration and removal efficiency did not significantly differ between CSOa and CSOb. Pollutant removal demonstrated a linear correlation with organic surface load. Overall, forced aeration in CSO-TW distinctly affected filter dynamics and improved its performance.

Floristic diversification of grasslands through introduction of forb communities is a potential method for supporting biodiversity. We re-assessed community development within a 10 year field trial in Denmark in which forb communities had been transplanted into bare subsoil on previously-farmed land in open gaps in 2010. The randomized block experiment included un-planted vegetation free control plots on subsoil. Experimental forbs are common to the northwest European flora. In 2020 the community development was re-evaluated. All plots had developed into forb dominated, dense communities in which it was clear that species richness had declined primarily due to loss of annual and biennial species including increased density of the vegetation. On average, the colonization of graminoids was higher in the control plots compared to the treatment plots. Across the experiment, patches of grass e.g. Festuca rubra had colonized transplanted plots and defeated some forbs. The transplanted forbs Achillea millefolium, Agrimonia eupatoria, and Galium mollugo were widespread in all plots. Control plots had been colonized by species from the surroundings including the treatment plots. Our long-term results show that forb introduced communities were highly resistant to grass colonization for many years. Exposed subsoil can develop into forb dominated spots provided that a propagule source is close by. Top soil stripping combined with introduction of forb community hotspots is an effective tool for limiting germination and establishment of aggressive competitor species from soil seed bank and surroundings. Winter-cutting is a potential, low-input management technique for diversification, however further studies are needed to investigate whether the technique in itself is sufficient to diversify species-poor temperate grasslands.