Browsing by Author "Boersma, Kate S."
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- Limitations of trait‐based approaches for stressor assessment: The case of freshwater invertebrates and climate driversHamilton, Anna T.; Schäfer, Ralf B.; Pyne, Matthew I.; Chessman, Bruce; Kakouei, Karan; Boersma, Kate S.; Verdonschot, Piet F. M.; Verdonschot, Ralf C. M.; Mims, Meryl C.; Khamis, Kieran; Bierwagen, Britta; Stamp, Jen (Wiley, 2019-09)The appeal of trait-based approaches for assessing environmental vulnerabilities arises from the potential insight they provide into the mechanisms underlying the changes in populations and community structure. Traits can provide ecologically based explanations for observed responses to environmental changes, along with predictive power gained by developing relationships between traits and environmental variables. Despite these potential benefits, questions remain regarding the utility and limitations of these approaches, which we explore focusing on the following questions: (a) How reliable are predictions of biotic responses to changing conditions based on single trait–environment relationships? (b) What factors constrain detection of single trait–environment relationships, and how can they be addressed? (c) Can we use information on meta-community processes to reveal conditions when assumptions underlying trait-based studies are not met? We address these questions by reviewing published literature on aquatic invertebrate communities from stream ecosystems. Our findings help to define factors that influence the successful application of trait-based approaches in addressing the complex, multifaceted effects of changing climate conditions on hydrologic and thermal regimes in stream ecosystems. Key conclusions are that observed relationships between traits and environmental stressors are often inconsistent with predefined hypotheses derived from current trait-based thinking, particularly related to single trait–environment relationships. Factors that can influence findings of trait-based assessments include intercorrelations of among traits and among environmental variables, spatial scale, strength of biotic interactions, intensity of habitat disturbance, degree of abiotic stress, and methods of trait characterization. Several recommendations are made for practice and further study to address these concerns, including using phylogenetic relatedness to address intercorrelation. With proper consideration of these issues, trait-based assessment of organismal vulnerability to environmental changes can become a useful tool to conserve threatened populations into the future.
- Organized Oral Session 44: Impacts of Species Addition and Species Loss on Ecosystem Function in Freshwater SystemsCapps, Krista A.; Atkinson, Carla L.; Rugenski, Amanda; Baxter, Colden V.; Boersma, Kate S.; Carey, Cayelan C.; McIntyre, Peter B.; Moore, Jonathan W.; Nowlin, Weston H.; Vaughn, Caryn C. (Ecological Society of America, 2012-10)Understanding the role of species as drivers of ecosystem processes is imperative to preserve, utilize, and sustain ecosystems globally. Addition of species through invasion and loss of species through extirpation or extinction can have profound effects on ecosystem structure and function (Zavaleta et al. 2009). This is especially true for freshwater ecosystems in which a preponderance of native species are threatened with extinction and where nonnative species are frequently introduced (Dudgeon and Smith 2006). Commonly, anthropogenic activities result in the loss of biodiversity and enhance the ability of exotic species to invade and persist in novel habitats (Dudgeon and Smith 2006). Because these activities are expected to increase through time, advances in understanding the consequences of species loss and addition on ecosystem function are needed to guide appropriate management and conservation decisions. The loss and addition of organisms may render habitats functionally impaired (Covich et al. 2004); therefore, understanding the consequences of such change is imperative to manage, mitigate, and restore freshwater ecosystems.
- Pervasive changes in stream intermittency across the United StatesZipper, Samuel C.; Hammond, John C.; Shanafield, Margaret; Zimmer, Margaret; Datry, Thibault; Jones, C. Nathan; Kaiser, Kendra E.; Godsey, Sarah E.; Burrows, Ryan M.; Blaszczak, Joanna R.; Busch, Michelle H.; Price, Adam N.; Boersma, Kate S.; Ward, Adam S.; Costigan, Katie; Allen, George H.; Krabbenhoft, Corey A.; Dodds, Walter K.; Mims, Meryl C.; Olden, Julian D.; Kampf, Stephanie K.; Burgin, Amy J.; Allen, Daniel C. (2021-08)Non-perennial streams are widespread, critical to ecosystems and society, and the subject of ongoing policy debate. Prior large-scale research on stream intermittency has been based on long-term averages, generally using annually aggregated data to characterize a highly variable process. As a result, it is not well understood if, how, or why the hydrology of non-perennial streams is changing. Here, we investigate trends and drivers of three intermittency signatures that describe the duration, timing, and dry-down period of stream intermittency across the continental United States (CONUS). Half of gages exhibited a significant trend through time in at least one of the three intermittency signatures, and changes in no-flow duration were most pervasive (41% of gages). Changes in intermittency were substantial for many streams, and 7% of gages exhibited changes in annual no-flow duration exceeding 100 days during the study period. Distinct regional patterns of change were evident, with widespread drying in southern CONUS and wetting in northern CONUS. These patterns are correlated with changes in aridity, though drivers of spatiotemporal variability were diverse across the three intermittency signatures. While the no-flow timing and duration were strongly related to climate, dry-down period was most strongly related to watershed land use and physiography. Our results indicate that non-perennial conditions are increasing in prevalence over much of CONUS and binary classifications of 'perennial' and 'non-perennial' are not an accurate reflection of this change. Water management and policy should reflect the changing nature and diverse drivers of changing intermittency both today and in the future.
- Spatial Patterns and Drivers of Nonperennial Flow Regimes in the Contiguous United StatesHammond, John C.; Zimmer, Margaret A.; Shanafield, Margaret; Kaiser, Kendra E.; Godsey, Sarah E.; Mims, Meryl C.; Zipper, Samuel C.; Burrows, Ryan M.; Kampf, Stephanie K.; Dodds, Walter K.; Jones, C. Nathan; Krabbenhoft, Corey A.; Boersma, Kate S.; Datry, Thibault; Olden, Julian D.; Allen, George H.; Price, Adam N.; Costigan, Katie H.; Hale, Rebecca; Ward, Adam S.; Allen, Daniel C. (2021-01-28)Over half of global rivers and streams lack perennial flow, and understanding the distribution and drivers of their flow regimes is critical for understanding their hydrologic, biogeochemical, and ecological functions. We analyzed nonperennial flow regimes using 540 U.S. Geological Survey watersheds across the contiguous United States from 1979 to 2018. Multivariate analyses revealed regional differences in no-flow fraction, date of first no flow, and duration of the dry-down period, with further divergence between natural and human-altered watersheds. Aridity was a primary driver of no-flow metrics at the continental scale, while unique combinations of climatic, physiographic and anthropogenic drivers emerged at regional scales. Dry-down duration showed stronger associations with nonclimate drivers compared to no-flow fraction and timing. Although the sparse distribution of nonperennial gages limits our understanding of such streams, the watersheds examined here suggest the important role of aridity and land cover change in modulating future stream drying. Plain Language Summary A majority of global streams are nonperennial, flowing only part of the year, and are critical for sustaining flow downstream, providing habitat for many organisms, and regulating chemical and biological processes. Using long-term U.S. Geological Survey measurements for 540 watersheds across the contiguous United States, we mapped patterns and examined the causes of no-flow fraction, the fraction of each climate year with no flow, no-flow timing, the date of the climate year on which the first recorded no flow takes place, and length of the dry-down period, the average number of days from a local peak in daily flow to the first occurrence of no flow. We found differences in patterns of no-flow characteristics between regions, with higher no-flow fraction, earlier timing, and shorter dry-down duration in the western United States. No-flow fractions were greater and less variable in natural watersheds, while no-flow timing was earlier and dry-down duration was shorter in human-modified watersheds. Aridity had the greatest effect on intermittence across the United States, but unique combinations of climate, biophysical, and human impacts were important in different regions. The number of gages measuring streamflow in nonperennial streams is small compared to perennial streams, and increased monitoring is needed to better understand drying behavior. Key Points . Three metrics reveal regional and human-driven patterns of nonperennial flow: no-flow fraction, day of first no flow, and dry-down duration Streams with human modifications generally dry more quickly than unmodified streams, especially in California and the Southern Great Plains Climate strongly influences no-flow fraction and timing, but physiographic variables are more important for the duration of dry down
- What’s in a Name? Patterns, Trends, and Suggestions for Defining Non-Perennial Rivers and StreamsBusch, Michelle H.; Costigan, Katie H.; Fritz, Ken M.; Datry, Thibault; Krabbenhoft, Corey A.; Hammond, John C.; Zimmer, Margaret A.; Olden, Julian D.; Burrows, Ryan M.; Dodds, Walter K.; Boersma, Kate S.; Shanafield, Margaret; Kampf, Stephanie K.; Mims, Meryl C.; Bogan, Michael T.; Ward, Adam S.; Perez Rocha, Mariana; Godsey, Sarah E.; Allen, George H.; Blaszczak, Joanna R.; Jones, C. Nathan; Allen, Daniel C. (MDPI, 2020-07-13)Rivers that cease to flow are globally prevalent. Although many epithets have been used for these rivers, a consensus on terminology has not yet been reached. Doing so would facilitate a marked increase in interdisciplinary interest as well as critical need for clear regulations. Here we reviewed literature from Web of Science database searches of 12 epithets to learn (Objective 1—O1) if epithet topics are consistent across Web of Science categories using latent Dirichlet allocation topic modeling. We also analyzed publication rates and topics over time to (O2) assess changes in epithet use. We compiled literature definitions to (O3) identify how epithets have been delineated and, lastly, suggest universal terms and definitions. We found a lack of consensus in epithet use between and among various fields. We also found that epithet usage has changed over time, as research focus has shifted from description to modeling. We conclude that multiple epithets are redundant. We offer specific definitions for three epithets (non-perennial, intermittent, and ephemeral) to guide consensus on epithet use. Limiting the number of epithets used in non-perennial river research can facilitate more effective communication among research fields and provide clear guidelines for writing regulatory documents.
- Zero or not? Causes and consequences of zero-flow stream gage readingsZimmer, Margaret A.; Kaiser, Kendra E.; Blaszczak, Joanna R.; Zipper, Samuel C.; Hammond, John C.; Fritz, Ken M.; Costigan, Katie H.; Hosen, Jacob; Godsey, Sarah E.; Allen, George H.; Kampf, Stephanie K.; Burrows, Ryan M.; Krabbenhoft, Corey A.; Dodds, Walter K.; Hale, Rebecca; Olden, Julian D.; Shanafield, Margaret; DelVecchia, Amanda G.; Ward, Adam S.; Mims, Meryl C.; Datry, Thibault; Bogan, Michael T.; Boersma, Kate S.; Busch, Michelle H.; Jones, C. Nathan; Burgin, Amy J.; Allen, Daniel C. (2020-05)Streamflow observations can be used to understand, predict, and contextualize hydrologic, ecological, and biogeochemical processes and conditions in streams. Stream gages are point measurements along rivers where streamflow is measured, and are often used to infer upstream watershed-scale processes. When stream gages read zero, this may indicate that the stream has dried at this location; however, zero-flow readings can also be caused by a wide range of other factors. Our ability to identify whether or not a zero-flow gage reading indicates a dry fluvial system has far reaching environmental implications. Incorrect identification and interpretation by the data user can lead to inaccurate hydrologic, ecological, and/or biogeochemical predictions from models and analyses. Here, we describe several causes of zero-flow gage readings: frozen surface water, flow reversals, instrument error, and natural or human-driven upstream source losses or bypass flow. For these examples, we discuss the implications of zero-flow interpretations. We also highlight additional methods for determining flow presence, including direct observations, statistical methods, and hydrologic models, which can be applied to interpret causes of zero-flow gage readings and implications for reach- and watershed-scale dynamics. Such efforts are necessary to improve our ability to understand and predict surface flow activation, cessation, and connectivity across river networks. Developing this integrated understanding of the wide range of possible meanings of zero-flows will only attain greater importance in a more variable and changing hydrologic climate. This article is categorized under: Science of Water > Methods Science of Water > Hydrological Processes Water and Life > Conservation, Management, and Awareness