Stephen Plont

Watershed characteristics create a mosaic of potential storage zones, and linkages between these result in hydrologic connectivity between groundwaters and surface waters. Watershed storage and connectivity are fundamental controls on stream network dynamics, yet predicting the patterns of hydrologic responses like streamflow remains difficult due to landscape heterogeneity across multiple, interacting spatial scales. Here, we characterize storage and connectivity dynamics at the watershed scale and the hydrogeomorphic feature (HGF) scale using a network of steam and riparian groundwater monitoring wells in three watersheds spanning the Coastal Plain, Piedmont, and Appalachian Plateaus physiographic regions of the southeastern USA. At the watershed scale, we operationalized watershed storage as the slope of streamflow recession at the watershed outlet, and hydrologic connectivity as the relationship between outlet discharge and network length. At the HGF scale, we operationalized storage as the slope of water level recession at seven in-stream monitoring locations, and connectivity as the lateral hydraulic gradient and water level hysteresis relationships between the stream channel and adjacent riparian zone at three locations per watershed. At the watershed scale, we found patterns in storage and connectivity varied across physiographic regions. We also found distinct storage and connectivity dynamics across HGFs, many of which challenged existing conceptualizations for similar geomorphic settings. Notably, channel incision emerged as a key structural control, homogenizing storage and connectivity patterns across otherwise disparate watersheds and producing a common threshold response in watershed storage. Together, these results demonstrate that watershed-scale patterns do not reflect the heterogeneity observed at the HGF scale. Moreover, river corridor structure, particularly channel incision, is a key driver of storage and connectivity dynamics across physiographic settings.

Watershed characteristics create a mosaic of potential storage zones, and linkages between these result in hydrologic connectivity between groundwaters and surface waters. Watershed storage and connectivity are fundamental controls on stream network dynamics, yet predicting the patterns of hydrologic responses like streamflow remains difficult due to landscape heterogeneity across multiple, interacting spatial scales. Here, we characterize storage and connectivity dynamics at the watershed scale and the hydrogeomorphic feature (HGF) scale using a network of steam and riparian groundwater monitoring wells in three watersheds spanning the Coastal Plain, Piedmont, and Appalachian Plateaus physiographic regions of the southeastern USA. At the watershed scale, we operationalized watershed storage as the slope of streamflow recession at the watershed outlet, and hydrologic connectivity as the relationship between outlet discharge and network length. At the HGF scale, we operationalized storage as the slope of water level recession at seven in-stream monitoring locations, and connectivity as the lateral hydraulic gradient and water level hysteresis relationships between the stream channel and adjacent riparian zone at three locations per watershed. At the watershed scale, we found patterns in storage and connectivity varied across physiographic regions. We also found distinct storage and connectivity dynamics across HGFs, many of which challenged existing conceptualizations for similar geomorphic settings. Notably, channel incision emerged as a key structural control, homogenizing storage and connectivity patterns across otherwise disparate watersheds and producing a common threshold response in watershed storage. Together, these results demonstrate that watershed-scale patterns do not reflect the heterogeneity observed at the HGF scale. Moreover, river corridor structure, particularly channel incision, is a key driver of storage and connectivity dynamics across physiographic settings.

Watershed characteristics create a mosaic of potential storage zones, and linkages between these result in hydrologic connectivity between groundwaters and surface waters. Watershed storage and connectivity are fundamental controls on stream network dynamics, yet predicting the patterns of hydrologic responses like streamflow remains difficult due to landscape heterogeneity across multiple, interacting spatial scales. Here, we characterize storage and connectivity dynamics at the watershed scale and the hydrogeomorphic feature (HGF) scale using a network of steam and riparian groundwater monitoring wells in three watersheds spanning the Coastal Plain, Piedmont, and Appalachian Plateaus physiographic regions of the southeastern USA. At the watershed scale, we operationalized watershed storage as the slope of streamflow recession at the watershed outlet, and hydrologic connectivity as the relationship between outlet discharge and network length. At the HGF scale, we operationalized storage as the slope of water level recession at seven in-stream monitoring locations, and connectivity as the lateral hydraulic gradient and water level hysteresis relationships between the stream channel and adjacent riparian zone at three locations per watershed. At the watershed scale, we found patterns in storage and connectivity varied across physiographic regions. We also found distinct storage and connectivity dynamics across HGFs, many of which challenged existing conceptualizations for similar geomorphic settings. Notably, channel incision emerged as a key structural control, homogenizing storage and connectivity patterns across otherwise disparate watersheds and producing a common threshold response in watershed storage. Together, these results demonstrate that watershed-scale patterns do not reflect the heterogeneity observed at the HGF scale. Moreover, river corridor structure, particularly channel incision, is a key driver of storage and connectivity dynamics across physiographic settings.

Here we present a comprehensive dataset of hydrologic, biogeochemical, microbial, and macroinvertebrate community measurements from a set of multi-year, co-occurring, watershed studies in non-perennial stream networks that dynamically expand and contract over space and time. The data were collected over the three consecutive water years (Autumn 2021–Autumn 2024) across three stream networks draining watersheds with a similar humid, subtropical climate but distinct physiographies (i.e., Piedmont, Appalachian Plateau, Coastal Plain) in Alabama, USA. Our goal was to characterize the spatiotemporal patterns and drivers of how non-perennial stream networks expand and contract, as well as the biogeochemical, microbial, and macroinvertebrate dynamics associated with changes in network connectivity and water availability. We used a combination of spatial, temporal, and spatiotemporal sampling and sensor-based monitoring approaches to capture hydrologic, biogeochemical, and ecological responses to network expansion and contraction in each watershed. This manuscript describes the overall study design, monitoring network and sampling approaches, data and sample collection and analysis, and specific datasets generated. All data products are publicly available through the “Aquatic Intermittency effects on Microbiomes in Streams” (AIMS) Hydroshare data repository for hydrologic, biogeochemical, and macroinvertebrate data (AIMS region code = “SE”; https://www.hydroshare.org/group/247, Plont et al., 2026t) and through the NCBI data repository for microbial data. All data product-specific DOIs and repository-specific unique IDs are cited in Appendix A (Tables A1, A3).

Here we present a comprehensive dataset of hydrologic, biogeochemical, microbial, and macroinvertebrate community measurements from a set of multi-year, co-occurring, watershed studies in non-perennial stream networks that dynamically expand and contract over space and time. The data were collected over the 2022–2024 water years across three stream networks draining watersheds with a similar humid, subtropical climate but distinct physiographies (i.e., Piedmont, Appalachian Plateau, Coastal Plain) in Alabama, USA. Our goal was to characterize the spatiotemporal patterns and drivers of how non-perennial stream networks expand and contract, as well as the biogeochemical, microbial, and macroinvertebrate dynamics associated with changes in network connectivity and water availability. We used a combination of spatial, temporal, and spatiotemporal sampling and sensor-based monitoring approaches to capture hydrologic, biogeochemical, and ecological responses to network expansion and contraction in each watershed. This manuscript describes the overall study design, monitoring network and sampling approaches, data and sample collection and analysis, and specific datasets generated. All data products are publicly available through the Hydroshare data repository for hydrologic, biogeochemical, and macroinvertebrate data (https://www.hydroshare.org/group/247) and through the NCBI data repository for microbial data. All data product-specific DOIs and repository-specific unique IDs are cited in Appendix A (Table A1, Table A3).

While collaborative science is becoming the norm in ecology, many ecologists participating in collaborations are less aware of the body of research that studies the processes by which collaborative teams organize and communicate. Here, we discuss how we successfully used a shared leadership model in the Dry Rivers Research Coordination Network. We discuss how this model promoted our success in different stages of the project, using the Tuckman model of team development: forming, storming, norming, performing and adjourning. Shared leadership in the forming phase helped us recruit a diverse membership from different scientific disciplines. In the storming and norming phases, shared leadership was especially useful in ensuring that all voices were heard in establishing group norms that promoted adhesion among and investment by RCN members. Shared leadership in the performing phase was crucial in providing opportunities for early career members to lead projects, and in the adjourning phase we reflected upon our entire collaboration to identify that shared leadership was crucial to our success, generating the thesis for this commentary. It is our hope that others may find this discussion of our experience in implementing a shared leadership model useful in developing their own fruitful collaborations. Read the free Plain Language Summary for this article on the Journal blog.

Dynamics of respired dissolved organic carbon in a stream data

Headwater streams make up nearly 80% of the stream network by length and play an important role in shaping the physical, chemical, and biological functions of downstream waters. In the Southeastern US, these systems are beginning to experience increases in the frequency and duration of drying, but it is unclear how increased drying will impact downstream water quality. To begin to address this issue, we examined nitrogen dynamics in a forested headwater stream across an annual drying event. The annual drying event was divided into seasonal wet (March–June), dry‐down (June–October), and rewet (November–March) periods. We used a combination of water quality sensors at the watershed outlet, spatially distributed synoptic sampling of net denitrification conditions and physicochemical variables across the watershed, and a series of denitrification potential experiments to examine variation in biogeochemical state across the annual drying event. At the watershed outlet, nitrate concentrations were positively correlated with increased watershed‐scale connectivity during the rewet period, while nitrate concentrations were positively correlated with increased streamflow during the dry‐down period. Throughout the watershed, net denitrification conditions varied more across seasons than space, with greater net denitrification conditions during the dry‐down period. Further, net denitrification conditions were positively correlated to stream temperature, nitrate, and ammonium concentrations but inversely related to streamflow. Finally, denitrification measurements confirmed the dry‐down period experienced the highest denitrification rates. Our results highlight the connection between stream drying and nitrogen dynamics in humid systems, providing key information for developing predictive understanding of headwater streams.

Stream confluences are ubiquitous interfaces in freshwater networks and serve as junctions of previously independent landscapes. However, few studies have investigated how confluences influence the transport, mixing, and fate of organic matter (OM) and inorganic nutrients at the scale of river networks. To understand how network biogeochemical fluxes may be altered by confluences, we conducted two sampling campaigns at five confluences in summer and fall 2021 spanning the extent of a mixed land use stream network. We sampled the confluence mainstem and tributary reaches as well as throughout the mixing zone downstream. We predicted that biologically reactive solutes would mix non‐conservatively downstream of confluences and that alterations to downstream biogeochemistry would be driven by differences in chemistry and size of the tributary and upstream reaches. In our study, confluences were geomorphically distinct (e.g., wider, deeper, unique erosional, and depositional features) downstream compared to reaches upstream of the confluence. Dissolved OM and nutrients mixed non‐conservatively downstream of the five confluences. Biogeochemical patterns downstream of confluences were only partially explained by contributing reach chemistry and drainage area. We found that the relationship between geomorphic variability, water residence time, and microbial respiration differed between reaches upstream and downstream of confluences. The lack of explanatory power from network‐scale drivers suggests that non‐conservative mixing downstream of confluences may be driven by biogeochemical processes within the confluence mixing zone. The unique geomorphology, non‐conservative biogeochemistry, and ubiquity of confluences highlights a need to account for the distinct functional role of confluences in water resource management in freshwater networks.