Ecohydrology最新文献

In the last decades, so-called internal or sea-based mitigation measures have been suggested as nature-based solutions to remove nutrients and improve water quality in semi-enclosed coastal waters. However, these have rarely been tested in the field, especially in colder climates where winter ice cover is common. The aim of this experimental research was to investigate plant growth conditions in such an environment, as well to estimate nutrient removal capacity by harvesting constructed floating wetlands (CFWs). We tested small (24–28 m²) CFWs (Biomatrix®, Scotland, UK) at two demonstration sites: the Curonian lagoon (CL, Lithuania) and Szczecin lagoon (SL, Poland). In the CL, CFWs were planted predominantly with Carex acutiformes (Ehrh.), while the SL CFW was planted mainly with the reed Phragmites australis (Cav.) Trin. ex Steud. We aimed to test the amount of nutrient removal by plant harvesting over three subsequent years (2019–2021). We investigated carbon storage capacity and plant nutrient stoichiometry as indicators of potential nutrient limitation in the brackish coastal waters. Plant biomass increased annually, stabilising at 2.5–3.7 kg wet weight m⁻². The total nutrient uptake per installed island area varied with the plant species composition. In the successive years, the harvested plants from the CL CFW dominated by Carex accumulated 10.4–13.1 g N m⁻², 0.6–0.8 g P m⁻² and 318–431 g C m⁻² per year. The harvest from the SL CFW dominated by Phragmites contained a two-times higher amount of nutrients, the respective figures being 21.2 g N m⁻², 1.6 g P m⁻² and 704 g C m⁻². The nutrient stoichiometry in the vegetation did not suggest the presence of sub-optimal growth conditions due to nitrogen limitation. However, the CL's dissolved nutrient supply was very low during the summer cyanobacteria bloom and indicated a severe nitrogen deficiency (as reflected in the dissolved inorganic nitrogen:dissolved inorganic phosphorus [DIN:DIP] molar ratio of 6). We suggest that to maximise nutrient removal capacity, tall plants with high biomass should be selected and/or plants with fine root systems to efficiently uptake the limiting nutrient from the water.

Environmental contamination by plastics has been receiving considerable attention from scientists, policy makers and the public during the last few decades. Though some of the models have succeeded in simulating the transport and fate of plastic debris in freshwater systems, a complete model is now being developed to clarify the dynamic characteristics of the plastic budget on a continental scale. Recently, the author linked two process-based eco-hydrology models, NICE (National Integrated Catchment-based Eco-hydrology) and NICE-BGC (BioGeochemical Cycle), to a plastic debris model that accounts for both the transport and fate of plastic debris (advection, dispersion, diffusion, settling, dissolution and biochemical degradation by light and temperature) and applied these models on a regional scale and also for global major rivers. The present study was newly modified to incorporate the plastic dynamics in estuaries by extending the previous studies. The model was employed to conduct a 2-year global simulation aimed at evaluating changes in plastic dynamics in major rivers including 130 tidal estuaries. The model simulated the impact of estuaries on plastic budget and its seasonal variability caused by settling, resuspension and bedload transport during 2014–2015. The model showed that plastics with smaller particle sizes account for more in the water of estuaries than that of rivers, and plastics with larger particle sizes accumulate more on the riverbed. The simulated result also showed that estuaries trap more plastic than lakes and riverbeds (0.218 ± 0.053 Tg/year) although not as much as reservoirs (0.386 ± 0.103 Tg/year). More than 40% of plastics were retained by lakes, reservoirs, riverbeds and estuaries and the riverine plastic transport to the ocean was revised from 1.749 ± 0.371 Tg/year in the author's previous study to 1.000 ± 0.397 Tg/year in the present study. These results aid the development of solutions and measures for the reduction of plastic input to the ocean and help quantify the magnitude of plastic transport under climate change.

Hydraulic redistribution (HR) is a common phenomenon in water-limited ecosystems; however, it remains unclear how the volume of water transported via HR compares to other components of the hydrologic budget and how HR influences water availability for understory plant communities. In this study, we investigate the absolute and relative magnitude of HR on a forest water budget and identify potential impacts of this water subsidy to understory plant communities. We scaled tree-level estimates of transpiration and HR of three common tree species naturally occurring in a longleaf pine woodland with plot-level measurements of basal area to determine their magnitude at the stand scale. We trenched plots containing understory vegetation but devoid of mature trees and their connected roots to exclude HR subsidies to understory plant species. We analysed soil water isotopes and assessed leaf water potential (Ψ_L) in trenched and control plots to determine if HR results in mixing of water among soil strata and improves understory plant moisture status. Water inputs from HR were equivalent to >30% of total rainfall for the site during the observation period and ~40% of total tree water uptake, depending on species. A stable isotope mixing model confirmed that soil water within HR-exposed plots was more similar to groundwater, whereas soil water within trenched plots was more similar to precipitation. Exclusion of HR via trenching decreased soil moisture and pre-dawn Ψ_L for all understory species. These three lines of evidence suggest that HR from overstory trees redistributes a sizable portion of water from deeper to shallower soil profiles and that this water subsidy enhances understory plant water status.

The characterization of long-term streamflow in regions undergoing climatic change and agricultural expansion is relevant for achieving sustainable development goals and for assessing the vulnerability of water-dependent populations and agricultural activities. The objective of this work was to characterize the temporal patterns of water yield in the plain basin of the Carcarañá River (33,063 km²), located in central Argentina and to analyse its relationship with a fast expansion of rainfed cultivation and climate change. The streamflow data for the period 1980–2020 were analysed in conjunction with climatic data (rainfall, reference evapotranspiration), satellite data (NDVI) and cropping statistics (sown area of summer crops) data. The annual water yield averaged ~10% of the rainfall and showed a clear upward trend throughout the study period, both in absolute terms and relative to rainfall (i.e., runoff coefficient), which was not explained by rainfall or reference evapotranspiration temporal patterns. Conversely, we found that the trend in water yield was positively associated with the agricultural area (p < 0.05), which more than doubled during the study period (from 29% to 66%). Likewise, the mean NDVI of the basin, a proxy for primary productivity and vegetation transpiration, has decreased steadily over the last 20 years (p < 0.05). The separation between base flow and quick flow suggested that both flows increased during the analysed period (p < 0.05), though the latter would have been more relevant in explaining the trend observed in total flow. Taken together, our results suggest that agricultural expansion, rather than climate change, is the dominant factor explaining the hydrological changes observed in the study basin. Understanding the key role of land use in shaping the hydrology of a landscape is critical to developing policies and practices for more efficient and sustainable use of environmental resources.

Lotic environments are among the most vulnerable aquatic ecosystems, and changes occurring in them happen faster than our capacity to measure the impacts, with the choice of community attributes that best reflect these disturbances still unclear. In this study, we evaluated the response of phytoplankton species and species traits along a gradient of urbanization in lowland streams. To do this, we sampled nine streams in three areas classified as densely populated (DP), low populated (LP), and rural areas (RA) during the four seasons (n = 108), considering relevant limnological variables (including metals, herbicides, and inorganic nutrients) and phytoplankton. Phytoplankton was analysed using taxonomic and morpho-functional traits approaches. We used several multivariate analyses to assess phytoplankton species and trait distribution among stream groups (DP, LP, RA) and identify their environmental drivers. We found that phytoplankton responded to the urbanization gradient at both taxonomic and functional levels. However, this response was mediated by the land use (urban vs. rural) rather than its intensity. The main stressors detected were eutrophic conditions and organic matter contamination, which differed among groups (DP-LP and RA). Both approximations indicated eutrophic, organically enriched conditions, but the situation varied among seasons and stream groups. The response of the taxonomic approach was clearer than the traits-based approach, showing differences in density only between stream groups in the summer and the spring. Phytoplankton was responding to the gradient of urbanization in these subtropical lowland streams, but the seasonality, especially temperature and changes in the water column mixing also mediate the effect.

Canopy rainfall interception is one key hydrological process, affecting rainwater redistribution and effectiveness in semiarid regions. Canopy rainfall interception loss is jointly influenced by meteorology, vegetation and topography. The canopy water storage capacity (S), rainfall interception depth (I_m) and ratio (I_%) and vegetation characteristics, together with topographic factors of three grassland communities (dominated by Bothriochloa ischaemum, Lespedeza davurica and Artemisia gmelinii, respectively) were investigated on the Loess Plateau of China during the main growing season (June to September). Results showed that I_m ranged from 0.55 to 0.89 mm and I_% ranged from 6.14% to 12.1%, with the maximum values occurring in August for three communities, and A. gmelinii community had the largest I_m (0.89 mm) and I_% (12.1%). The I_m and I_% were positively correlated with aboveground biomass (AGB), coverage (Cov), leaf area index (LAI), community-weighted mean height (CWMH) and altitude (Alt), but negatively correlated with slope degree and rainfall intensity (RI). Hierarchical partitioning analysis (HPA) showed that AGB had the highest contribution for I_m (20.3%), while Alt had the highest contribution for I_% (18.2%). The regression models based on forward selection could effectively predict the values of I_m (R² = 0.802, RMSE = 0.049) and I_% (R² = 0.546, RMSE = 1.434). Topographic factors (altitude, slope degree and aspect) indirectly influenced both I_m and I_% by modulating vegetation characteristics (AGB, Cov, etc.). All these indicated that aboveground biomass mainly determines grassland community rainfall interception loss in the semiarid Loess Plateau.

As one of the responses to the global commitments against climate change, the Ethiopian Government launched a nationwide Green Legacy Initiative (GLI) in 2019, which largely focused on forest tree plantations with some inclusion of fruit trees. Despite its tremendous efforts and investments, its effectiveness and impacts have not been studied. This paper attempted to address this necessity by conducting a cross-sectional quasi-experiment in three randomly selected woredas/districts of Lake Hawassa Watershed from August 20 to September 2, 2023. The research hypothesized the likely impacts of GLI on four dependent variables (hydrological regulation, soil stability, nutrient cycling and plant species diversity). To achieve this, the research considered the two variants of GLI practices (plantation with and without soil and water conservation measures) and the corresponding control sites. Having three sites and three treatments with five replications, the study involved a total of forty-five quadrats of the same size (20 m × 20 m). The first three parameters were analysed using the landscape functionality analysis method, while the fourth employed Shannon's diversity index. Results of ANOVA showed that, on average 87% of randomly selected quadrats were found to significantly improve the local hydrology (runoff potential) (≈ 83.3% with Av. p = 0.012), soil stability (≈100% with Av. p = 0.002), nutrient cycling (≈83.3% with Av. p = 0.017) and plant species diversity (≈83.3% with Av. p = 0.012). The research revealed positive results from the Ethiopian Green Legacy Initiative. The small number of samples is acknowledged as a limitation of the research.

Channel constructions significantly impact river hydrodynamics, subsequently influencing river ecosystems. To mitigate the negative influence of channel construction and protect fish habitat, it is essential to evaluate fish habitat suitability through the integration of hydrodynamic and habitat models. This study models channel constructions on both the left and right riverbanks to evaluate habitat suitability for Four Major Chinese Carps and the Chinese sturgeon. Initially, flow velocity, water depth and grain size are simulated, followed by an assessment of habitat conditions using the Habitat Suitability Index (HSI) for three distinct construction strategies. Results reveal that constructing channels on the left bank mitigates adverse effects on fish habitat, while constructions on the right bank and both riverbanks lead to habitat degradation. Long-term effects on riverbed elevation and fish habitat suitability post-construction were also investigated. Notably, the Four Major Chinese Carps consistently demonstrate greater suitability for the studied river, regardless of flow rate or construction strategies, in comparison to the Chinese sturgeon. These findings underscore diverse responses to channel construction, providing valuable insights for identifying critical habitat areas for endemic fish conservation. This research presents a robust framework for assessing fish ecology in river systems, offering support for conservation decision-makers.