Ecohydrology最新文献

The lack of information on what constitutes suitable habitat for native freshwater mussels can limit restoration efforts. While many species reside in silt–sand–gravel substrates, species such as the Spectaclecase (Cumberlandia monodonta) and Salamander (Simpsonaias ambigua) mussels are thought to be associated with rock structures (e.g., wing dams and rock outcrops) in rivers. Our objective was to assess if hydroacoustic technology could be used to quantify physical habitat features for C. monodonta and S. ambigua. Multibeam echosounder, acoustic Doppler current profiler, sidescan sonar and underwater videography were used to quantify water depth, substrate hardness, bed roughness and bed slope of the riverbed, water velocity, shear velocity and the degree of rock clustering at six sites in the Saint Croix River, Minnesota. The sites varied in type of rock structures and relative abundances of both species. The strength of the associations among physical habitat features and mussel abundance was weak; R² values were typically < 0.5. However, species-specific differences in microhabitat were observed. For example, C. monodonta was typically observed at sites with higher velocity and shear velocity compared to S. ambigua. Mussel abundance was greatest at sites that contained crevices of sand surrounded by boulders and bedrock. Future refinements in hydroacoustic methods and post-processing computations could improve predictions. Information on habitat features from occupied and unoccupied sites could help resource managers characterize existing occupied habitats, identify potential reintroduction areas and implement restoration programmes.

Understanding the disasters that arise from climate change in advance and developing necessary adaptation plans are crucial to mitigate their impacts. Drought progresses slowly but can profoundly impact entire ecosystems and human livelihoods. Many indices are introduced to analyse drought. This study aims to quantify the spatiotemporal response of groundwater systems to long-term meteorological and hydrological trends in the Seyhan Basin using the Groundwater Drought Index (GWI). It tests the hypothesis that groundwater drought exhibits a lagged but regionally distinct response to climatic drivers, especially in semiarid regions where topography, distance to the sea and anthropogenic withdrawals vary significantly. The years 1970–2016 were selected for analysing meteorological data and 1970–2015 for analysing hydrological data. Fifteen measurements from 24 meteorological observation stations (15 within the basin and 9 in neighbouring basins), 5 evaporation observation stations, 20 stream-gauging stations and 9 groundwater observation wells were utilised. The effects of analysed trends on GWI were examined, and climate change has been observed to impact drought parameters from a holistic perspective. Selecting an index appropriate to regional characteristics should be considered, and updating measurements is crucial for accurate predictions.

Pinus ponderosa is a widespread conifer species across western North America, yet its intraspecific variability in drought response remains understudied, particularly at subseasonal time scales. We investigated how intraspecific tree dominance influences physiological and anatomical growth responses to warm-season precipitation pulses in a semi-arid montane forest in southern Nevada, USA. Using high-resolution dendrochronology, quantitative wood anatomy and dual-isotope (δ¹⁸O, δ¹³C) analysis of tree-ring cellulose, we compared dominant (old-growth) and codominant (mature) trees during two growing seasons: one impacted by a remnant tropical storm that provided an uncharacteristic pulse of precipitation to southern Nevada during the monsoon season (2015) and one with drier conditions with little monsoonal precipitation (2016). Codominant trees exhibited stronger and more immediate growth responses to warm-season precipitation, characterized by increased tracheid production and cellulose δ¹⁸O values that matched those of warm-season precipitation δ¹⁸O values, indicating shallow soil water use. In contrast, dominant trees relied more on deeper soil moisture and showed more conservative growth strategies. These divergent strategies suggest that intraspecific dominance mediates access to water and controls the sensitivity of growth to seasonal precipitation variability, highlighting the importance of intraspecific variation in shaping forest resilience and climate adaptation strategies under increasing drought and climate extremes.

Intermittent streams are prevalent worldwide, yet the understanding of drivers of their changing flow patterns remains incomplete. We examined hydrological changes spanning four decades (1982–2020) in Kings Creek, an intermittent grassland stream within the Konza Prairie Biological Station in Kansas, USA. We analysed streamflow data from a US Geological Survey gauge on Kings Creek and three upstream Long Term Ecological Reasearch (LTER) sub-watersheds with annual, biennial or quadrennial burn frequencies and linked trajectories of woody encroachment to increased evapotranspiration and changes in streamflow. Riparian woody cover doubled in the annually and biannually burned sub-watersheds and sevenfold in the quadrennially burned watersheds. We observed significant decreases (84%) in daily discharge and number of annual flow days (55%) at the downstream USGS Kings Creek gauge, with similar changes in the LTER sub-watersheds. The changing riparian cover, propelled by the regional expansion of woody plants, contributed to decreased streamflow by amplifying actual evapotranspiration (ET). Seasonal assessments underscored the critical influence of late summer conditions (July–September), under which increases in ET were linked to rising temperatures and increased evapotranspiration by riparian cover. Our results highlight the significant hydrological impacts of woody encroachment in grasslands and emphasize the importance of long-term ecohydrological monitoring in unravelling the interplay between climate and vegetation as controls on the hyper-variable flow patterns in this intermittent stream. Predicting and managing hydrological impacts on the flow of intermittent grassland rivers and streams worldwide requires accounting for the effects of accelerating woody encroachment.

Under the current global disruption of natural hydrological dynamics of large rivers due to human activities, there is an urgent need to understand how hydrology influences freshwater biodiversity in riverine floodplains. The aim of our study was to disentangle the influence of aquatic habitat availability, aquatic habitat connectivity, and environmental conditions on the α-, β- and γ-diversity of phytoplankton, rotifers, microcrustaceans and macrophytes in shallow lakes from the Lower Paraná River floodplain. We conducted sampling campaigns during four hydrological conditions, including wet and extremely dry periods. We estimated the biodiversity of each biological group, assessed limnological conditions and calculated the availability and connectivity of aquatic habitats at both local (shallow lake) and landscape (floodplain) scales with active microwave Sentinel-1 and optical multispectral Sentinel-2 satellite data, combined with a geographic information system approach. To evaluate the influence of the studied variables on biodiversity, we applied generalised linear mixed models for α-diversity and a Mantel test for β-diversity. At the local scale, habitat availability and connectivity positively influenced overall α-diversity, while turbid and nutrient-rich conditions favoured phytoplankton but hindered microcrustacean α-diversity. At the landscape scale, β-diversity was more strongly associated with the heterogeneity of limnological conditions than with habitat connectivity, except for microcrustaceans, which were equally associated with both variables. Our study deepens the understanding of the main mechanisms of hydrology on the biodiversity of different biological groups and across spatial scales in the Lower Paraná River floodplain. Our findings underscore the critical importance of maintaining a dynamic hydrological regime to sustain essential floodplain processes that support aquatic habitats and promote biodiversity.

Human activities and climate change have significantly altered natural river flow regimes, adversely affecting ecosystems globally. This study uses the GAGES-II dataset (1981–2016) to examine relationships between environmental flow violations (EFVs) at stream gauges in the United States and characteristics of their upstream basins over two periods (1981–1998 and 1999–2016). The Variable Minimum Flow (VMF) approach was used to estimate environmental flows based on natural flow conditions for each hydrometric station. Basin characteristics were categorized into climate variability (precipitation and temperature changes), water withdrawals and geographical attributes. The variables representing these basin characteristics were then used as predictors or inputs to the random forest (RF) machine learning algorithm to analyse and predict temporal and spatial variations of EFVs based on the observed variations of predictors. The results of this study showed that approximately 55% of the 1625 stream gauges analysed exhibited EFV percentages exceeding 80% in both periods. Mapping these stations highlighted critical areas requiring intervention. Temporal EFV changes were assessed by comparing the two periods, and K-means clustering grouped stations into two clusters with distinct geographical and climatic characteristics. The RF models trained for prediction of average EFV differences between the two periods showed acceptable accuracy, with Kling–Gupta efficiency (KGE) values ranging from 0.5 to 0.7, although accuracy was higher in the stations in Cluster 2 covering more arid areas in the southwest. The feature importance analysis revealed that the dam storage-to-streamflow ratio (DSSR) and precipitation were key factors in humid areas (Cluster 1), while water withdrawal and temperature were more significant in arid areas (Cluster 2). A noticeable temporal shift was also observed as the relative importance of DSSR (water withdrawal) diminished (intensified) overtime. Given the large dataset and the diversity of factors considered, this methodology can be applied to the rest of the streamflow gauges in the United States, providing valuable insights for water resource management and environmental policy making.