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Lakes in the Midwest and Northeast United States are at risk of anthropogenic chloride contamination, but there is little knowledge of the prevalence and spatial distribution of freshwater salinization. Here, we use a quantile regression forest (QRF) to leverage information from 2,773 lakes to predict the chloride concentration of all 49,432 lakes greater than 4 ha in a 17-state area. The QRF incorporated 22 predictor variables, which included lake morphometry characteristics, watershed land use, and distance to the nearest road and interstate. Model predictions had an r2 of 0.94 for all chloride observations, and an r2 of 0.87 for predictions of the median chloride concentration observed at each lake. The four predictors with the largest influence on lake chloride concentrations were low and medium intensity development in the watershed, crop density in the watershed, and distance to the nearest interstate. Almost 2,000 lakes are predicted to have chloride concentrations above 50 mg L-1 and should be monitored. We encourage management and governing agencies to use lake-specific model predictions to assess salt contamination risk as well as to augment their monitoring strategies to more comprehensively protect freshwater ecosystems from salinization.
Hilary A. Dugan; Nicholas K. Skaff; Jonathan P. Doubek; Sarah L. Bartlett; Samantha M. Burke; Flora Krivak-Tetley; Jamie C. Summers; Paul C. Hanson; Kathleen C. Weathers. Lakes at Risk of Chloride Contamination. Environmental Science & Technology 2020, 54, 6639 -6650.
AMA StyleHilary A. Dugan, Nicholas K. Skaff, Jonathan P. Doubek, Sarah L. Bartlett, Samantha M. Burke, Flora Krivak-Tetley, Jamie C. Summers, Paul C. Hanson, Kathleen C. Weathers. Lakes at Risk of Chloride Contamination. Environmental Science & Technology. 2020; 54 (11):6639-6650.
Chicago/Turabian StyleHilary A. Dugan; Nicholas K. Skaff; Jonathan P. Doubek; Sarah L. Bartlett; Samantha M. Burke; Flora Krivak-Tetley; Jamie C. Summers; Paul C. Hanson; Kathleen C. Weathers. 2020. "Lakes at Risk of Chloride Contamination." Environmental Science & Technology 54, no. 11: 6639-6650.
The nematode Deladenus siricidicola is the primary biological control agent of Sirex noctilio, a globally invading woodwasp pest of Pinus species. Preliminary studies on the diversity of populations of D. siricidicola revealed very low diversity in the Southern Hemisphere where they have been introduced for the purpose of biological control. The potential to augment biocontrol efficacy by increasing genetic diversity in biocontrol programs motivated this study, which investigated the patterns of genetic diversity in D. siricidicola across eight countries, including the presumed native range (Spain) areas of accidental introduction (Canada and the USA) and countries D. siricidicola has been intentionally released (Argentina, Brazil, Chile, New Zealand and South Africa). Nematodes were screened using mitochondrial COI sequence data and twelve microsatellite markers. Analyses of these data identified three distinct lineages from North America (Lineage A), the Southern Hemisphere (Lineage B) and Spain (Lineage C). Strains from Chile were an exception as they appear to represent an admixture of lineages A and B. This suggests a common origin of populations throughout the Southern Hemisphere, with a second introduction from North America into Chile. The introduction into North America is distinct from that in the Southern Hemisphere and probably originated from Europe. It is evident that substantial genetic diversity exists in D. siricidicola globally, which could be exploited to augment the reduced diversity in some populations used in biocontrol programs.
Katrin Fitza; Jeff Garnas; María Lombardero; Matthew P. Ayres; Flora Krivak-Tetley; Rodrigo Ahumada; Brett P. Hurley; Michael J. Wingfield; Bernard Slippers. The global diversity of Deladenus siricidicola in native and non-native populations. Biological Control 2019, 132, 57 -65.
AMA StyleKatrin Fitza, Jeff Garnas, María Lombardero, Matthew P. Ayres, Flora Krivak-Tetley, Rodrigo Ahumada, Brett P. Hurley, Michael J. Wingfield, Bernard Slippers. The global diversity of Deladenus siricidicola in native and non-native populations. Biological Control. 2019; 132 ():57-65.
Chicago/Turabian StyleKatrin Fitza; Jeff Garnas; María Lombardero; Matthew P. Ayres; Flora Krivak-Tetley; Rodrigo Ahumada; Brett P. Hurley; Michael J. Wingfield; Bernard Slippers. 2019. "The global diversity of Deladenus siricidicola in native and non-native populations." Biological Control 132, no. : 57-65.
Lakes are active processors of organic carbon (OC) and play important roles in landscape and global carbon cycling. Allochthonous OC loads from the landscape, along with autochthonous OC loads from primary production, are mineralized in lakes, buried in lake sediments, and exported via surface or groundwater outflows. Although these processes provide a basis for a conceptual understanding of lake OC budgets, few studies have integrated these fluxes under a dynamic modeling framework to examine their interactions and relative magnitudes. We developed a simple, dynamic mass balance model for OC, and applied the model to a set of five lakes. We examined the relative magnitudes of OC fluxes and found that long-term (>10 year) lake OC dynamics were predominantly driven by allochthonous loads in four of the five lakes, underscoring the importance of terrestrially-derived OC in northern lake ecosystems. Our model highlighted seasonal patterns in lake OC budgets, with increasing water temperatures and lake productivity throughout the growing season corresponding to a transition from burial- to respiration-dominated OC fates. Ratios of respiration to burial, however, were also mediated by the source (autochthonous vs. allochthonous) of total OC loads. Autochthonous OC is more readily respired and may therefore proportionally reduce burial under a warming climate, but allochthonous OC may increase burial due to changes in precipitation. The ratios of autochthonous to allochthonous inputs and respiration to burial demonstrate the importance of dynamic models for examining both the seasonal and inter-annual roles of lakes in landscape and global carbon cycling, particularly in a global change context. Finally, we highlighted critical data needs, which include surface water DOC observations in paired tributary and lake systems, measurements of OC burial rates, groundwater input volume and DOC, and budgets of particulate OC.
Ian M. McCullough; Hilary A. Dugan; Kaitlin J. Farrell; Ana M. Morales-Williams; Zutao Ouyang; Derek Roberts; Facundo Scordo; Sarah L. Bartlett; Samantha M. Burke; Jonathan P. Doubek; Flora Krivak-Tetley; Nicholas K. Skaff; Jamie C. Summers; Kathleen C. Weathers; Paul C. Hanson. Dynamic modeling of organic carbon fates in lake ecosystems. Ecological Modelling 2018, 386, 71 -82.
AMA StyleIan M. McCullough, Hilary A. Dugan, Kaitlin J. Farrell, Ana M. Morales-Williams, Zutao Ouyang, Derek Roberts, Facundo Scordo, Sarah L. Bartlett, Samantha M. Burke, Jonathan P. Doubek, Flora Krivak-Tetley, Nicholas K. Skaff, Jamie C. Summers, Kathleen C. Weathers, Paul C. Hanson. Dynamic modeling of organic carbon fates in lake ecosystems. Ecological Modelling. 2018; 386 ():71-82.
Chicago/Turabian StyleIan M. McCullough; Hilary A. Dugan; Kaitlin J. Farrell; Ana M. Morales-Williams; Zutao Ouyang; Derek Roberts; Facundo Scordo; Sarah L. Bartlett; Samantha M. Burke; Jonathan P. Doubek; Flora Krivak-Tetley; Nicholas K. Skaff; Jamie C. Summers; Kathleen C. Weathers; Paul C. Hanson. 2018. "Dynamic modeling of organic carbon fates in lake ecosystems." Ecological Modelling 386, no. : 71-82.
There is increasing interest in using “real-world pedagogy” to train students in ways that make them better able to contribute toward a more sustainable society. While there is a robust body of literature on the competencies that students need as sustainability professionals, there is a lack of specific guidance in the literature on how to teach for competency development or on how to structure a program or course to support competency development. Our research addresses this gap in the literature through a description and autoethnographic reflection on the design and early implementation of a “real-world” course. The course is from the Environmental Studies Program at Dartmouth College (Hanover, NH, USA), but it takes place in the environs of the Gobabeb Research and Training Centre in the Namib Desert of Namibia and in nearby Topnaar settlements. Our research objective was to articulate strategies to address the primary pedagogical challenges that we faced during the design and first five iterations of the course. These include: How do we frame this course and communicate it to students in a way that is understandable and works within the particular context and constraints of the course? Can we provide students with a coherent framework that helps them to understand the approach and also provides a platform for thoughtful consideration, acquisition, and retention of appropriate competencies? How do we develop collaborations with our community partners that are ethical and effective? How do we frame these real-world experiences in a way that allows for students to integrate their experience with the theory and broader empiricism they learn on campus? To address these pedagogic challenges, we framed the course as a research-based course, more specifically community-based research (CBR), conducted in a social-ecological system (SES). We developed lower-level strategies for implementing this framing, including preparing students for collaborative research, encouraging student ownership of their learning, linking theory to research, and thoughtfully navigating time constraints. Furthermore, program-level and student-level engagement with community have been critical for avoiding becoming “helicopter researchers.” Drawing on our personal reflections and those of our community partners, we conclude with a discussion of emergent outcomes and the next steps for continual improvement and adaptation.
Douglas T. Bolger; Karen Hutchins Bieluch; Flora E. Krivak-Tetley; Gillian Maggs-Kölling; Joseph Tjitekulu. Designing a Real-World Course for Environmental Studies Students: Entering a Social-Ecological System. Sustainability 2018, 10, 2546 .
AMA StyleDouglas T. Bolger, Karen Hutchins Bieluch, Flora E. Krivak-Tetley, Gillian Maggs-Kölling, Joseph Tjitekulu. Designing a Real-World Course for Environmental Studies Students: Entering a Social-Ecological System. Sustainability. 2018; 10 (7):2546.
Chicago/Turabian StyleDouglas T. Bolger; Karen Hutchins Bieluch; Flora E. Krivak-Tetley; Gillian Maggs-Kölling; Joseph Tjitekulu. 2018. "Designing a Real-World Course for Environmental Studies Students: Entering a Social-Ecological System." Sustainability 10, no. 7: 2546.
Accidental and intentional global movement of species has increased the frequency of novel plant–insect interactions. In Patagonia, the European woodwasp,Sirex noctilio, has invaded commercial plantations of North American pines. We compared the patterns of resin defenses andS. noctilio-caused mortality at two mixed-species forests near San Carlos de Bariloche, Argentina. We observed lower levels of resin flow and higher levels of mortality inPinus contortacompared withPinus ponderosa. In general,S. noctilioattacked trees with lower resin compared with neighboring trees. Resin production inP. ponderosawas not related to growth rates, but forP. contorta, slower growing trees produced less resin than faster growing conspecifics. For all infested trees, attack density and number of drills (ovipositor probes) per attack did not vary with resin production. Most attacks resulted in one or two drills. Attack rates and drills/attack were basically uniform across the bole of the tree except for a decrease in both drills/attack and attack density in the upper portion of the crown, and an increase in the attack density for the bottom 10% of the tree. Planted pines in Patagonia grow faster than their counterparts in North America, and produce less resin, consistent with the growth-differentiation balance hypothesis. Limited resin defenses may help to explain the high susceptibility ofP. contortato woodwasps in Patagonia.
S.J. Martinson; A.A. Fernádez Ajó; A.S. Martínez; Flora Krivak-Tetley; J.M. Villacide; M.P. Ayres; J.C. Corley. Attack rates ofSirex noctilioand patterns of pine tree defenses and mortality in northern Patagonia. Bulletin of Entomological Research 2018, 109, 141 -149.
AMA StyleS.J. Martinson, A.A. Fernádez Ajó, A.S. Martínez, Flora Krivak-Tetley, J.M. Villacide, M.P. Ayres, J.C. Corley. Attack rates ofSirex noctilioand patterns of pine tree defenses and mortality in northern Patagonia. Bulletin of Entomological Research. 2018; 109 (2):141-149.
Chicago/Turabian StyleS.J. Martinson; A.A. Fernádez Ajó; A.S. Martínez; Flora Krivak-Tetley; J.M. Villacide; M.P. Ayres; J.C. Corley. 2018. "Attack rates ofSirex noctilioand patterns of pine tree defenses and mortality in northern Patagonia." Bulletin of Entomological Research 109, no. 2: 141-149.
Anthropogenic sources of chloride in a lake catchment, including road salt, fertilizer, and wastewater, can elevate the chloride concentration in freshwater lakes above background levels. Rising chloride concentrations can impact lake ecology and ecosystem services such as fisheries and the use of lakes as drinking water sources. To analyze the spatial extent and magnitude of increasing chloride concentrations in freshwater lakes, we amassed a database of 529 lakes in Europe and North America that had greater than or equal to ten years of chloride data. For each lake, we calculated climate statistics of mean annual total precipitation and mean monthly air temperatures from gridded global datasets. We also quantified land cover metrics, including road density and impervious surface, in buffer zones of 100 to 1,500 m surrounding the perimeter of each lake. This database represents the largest global collection of lake chloride data. We hope that long-term water quality measurements in areas outside Europe and North America can be added to the database as they become available in the future.
Hilary A. Dugan; Jamie C. Summers; Nicholas K. Skaff; Flora Krivak-Tetley; Jonathan P. Doubek; Samantha M. Burke; Sarah L. Bartlett; Lauri Arvola; Hamdi Jarjanazi; János Korponai; Andreas Kleeberg; Ghislaine Monet; Don Monteith; Karen Moore; Michela Rogora; Paul C. Hanson; Kathleen C. Weathers. Long-term chloride concentrations in North American and European freshwater lakes. Scientific Data 2017, 4, 170101 .
AMA StyleHilary A. Dugan, Jamie C. Summers, Nicholas K. Skaff, Flora Krivak-Tetley, Jonathan P. Doubek, Samantha M. Burke, Sarah L. Bartlett, Lauri Arvola, Hamdi Jarjanazi, János Korponai, Andreas Kleeberg, Ghislaine Monet, Don Monteith, Karen Moore, Michela Rogora, Paul C. Hanson, Kathleen C. Weathers. Long-term chloride concentrations in North American and European freshwater lakes. Scientific Data. 2017; 4 (1):170101.
Chicago/Turabian StyleHilary A. Dugan; Jamie C. Summers; Nicholas K. Skaff; Flora Krivak-Tetley; Jonathan P. Doubek; Samantha M. Burke; Sarah L. Bartlett; Lauri Arvola; Hamdi Jarjanazi; János Korponai; Andreas Kleeberg; Ghislaine Monet; Don Monteith; Karen Moore; Michela Rogora; Paul C. Hanson; Kathleen C. Weathers. 2017. "Long-term chloride concentrations in North American and European freshwater lakes." Scientific Data 4, no. 1: 170101.
The highest densities of lakes on Earth are in north temperate ecosystems, where increasing urbanization and associated chloride runoff can salinize freshwaters and threaten lake water quality and the many ecosystem services lakes provide. However, the extent to which lake salinity may be changing at broad spatial scales remains unknown, leading us to first identify spatial patterns and then investigate the drivers of these patterns. Significant decadal trends in lake salinization were identified using a dataset of long-term chloride concentrations from 371 North American lakes. Landscape and climate metrics calculated for each site demonstrated that impervious land cover was a strong predictor of chloride trends in Northeast and Midwest North American lakes. As little as 1% impervious land cover surrounding a lake increased the likelihood of long-term salinization. Considering that 27% of large lakes in the United States have >1% impervious land cover around their perimeters, the potential for steady and long-term salinization of these aquatic systems is high. This study predicts that many lakes will exceed the aquatic life threshold criterion for chronic chloride exposure (230 mg L−1), stipulated by the US Environmental Protection Agency (EPA), in the next 50 y if current trends continue.
Hilary A. Dugan; Sarah L. Bartlett; Samantha M. Burke; Jonathan P. Doubek; Flora Krivak-Tetley; Nicholas K. Skaff; Jamie C. Summers; Kaitlin Farrell; Ian M. McCullough; Ana M. Morales-Williams; Derek C. Roberts; Zutao Ouyang; Facundo Scordo; Paul C. Hanson; Kathleen C. Weathers. Salting our freshwater lakes. Proceedings of the National Academy of Sciences 2017, 114, 4453 -4458.
AMA StyleHilary A. Dugan, Sarah L. Bartlett, Samantha M. Burke, Jonathan P. Doubek, Flora Krivak-Tetley, Nicholas K. Skaff, Jamie C. Summers, Kaitlin Farrell, Ian M. McCullough, Ana M. Morales-Williams, Derek C. Roberts, Zutao Ouyang, Facundo Scordo, Paul C. Hanson, Kathleen C. Weathers. Salting our freshwater lakes. Proceedings of the National Academy of Sciences. 2017; 114 (17):4453-4458.
Chicago/Turabian StyleHilary A. Dugan; Sarah L. Bartlett; Samantha M. Burke; Jonathan P. Doubek; Flora Krivak-Tetley; Nicholas K. Skaff; Jamie C. Summers; Kaitlin Farrell; Ian M. McCullough; Ana M. Morales-Williams; Derek C. Roberts; Zutao Ouyang; Facundo Scordo; Paul C. Hanson; Kathleen C. Weathers. 2017. "Salting our freshwater lakes." Proceedings of the National Academy of Sciences 114, no. 17: 4453-4458.
In the western United States, forests are experiencing novel environmental conditions related to a changing climate and a suppression of the historical fire regime. Mixed-conifer forests, considered resilient to disturbance due to their heterogeneity in structure and composition, appear to be shifting to a more homogeneous state, but the timescale of these shifts is not well understood. Our objective was to assess the effects of climate and fire suppression on stand dynamics and demographic rates of an old-growth mixed-conifer forest in the Sierra Nevada. We used a Bayesian hierarchical analysis to quantify species and community rates of recruitment, growth, and mortality. Despite a warming climate, we found that stand density, basal area, and carbon have increased over 56 years. Fir recruitment and growth significantly exceeded the community-level median rates, whereas pine recruitment and growth was significantly lower than the community-level median rates. Shifts in species composition from a well-mixed stand to a more dense fir-dominated stand appear to be driven by low growth and recruitment rates of pines relative to firs. In forests such as these with consistent and relatively low mortality rates, we recommend that restoration and management activities be focused on promoting pine recruitment and growth.
Carrie R. Levine; Flora Krivak-Tetley; Natalie S. Van Doorn; Jolie-Anne S. Ansley; John J. Battles. Long-term demographic trends in a fire-suppressed mixed-conifer forest. Canadian Journal of Forest Research 2016, 46, 745 -752.
AMA StyleCarrie R. Levine, Flora Krivak-Tetley, Natalie S. Van Doorn, Jolie-Anne S. Ansley, John J. Battles. Long-term demographic trends in a fire-suppressed mixed-conifer forest. Canadian Journal of Forest Research. 2016; 46 (5):745-752.
Chicago/Turabian StyleCarrie R. Levine; Flora Krivak-Tetley; Natalie S. Van Doorn; Jolie-Anne S. Ansley; John J. Battles. 2016. "Long-term demographic trends in a fire-suppressed mixed-conifer forest." Canadian Journal of Forest Research 46, no. 5: 745-752.
Sirex noctilioFabricius (Hymenoptera, Siricidae) is rare and rarely studied where it is native in Eurasia, but is a widespread pest of pines in the Southern Hemisphere. Here we report on the abundance, basic biology, host use patterns and natural enemies of nativeS. noctilioin Galicia, Spain. Most trees attacked byS. noctiliofailed to produce any adult progeny: >90% of emergences came from Pinus pinaster, followed byPinus sylvestrisandPinus radiata.The proportions ofS. noctiliorequiring 1, 2 or 3 years for development were 0.72: 0.24: 0.04. Delayed development could be an adaptation to avoid parasitic nematodes, which sterilized 41.5% adults with one year generation time but only 19% of adults with 2 years generation time. Hymenoptera parasitoids accounted for 20% mortality. Sex ratios were male biased at 1: 2.9. Body size and fecundity were highly variable and lower than previously reported from the Southern Hemisphere. On attacked trees, there were 5–20 attacks per standard log (18 dm2), with usually 1–3 drills per attack. Attack densities and drills per attack were higher in trees that subsequently died. The production ofS. noctilioper log was positively related to total attacks, and negatively related to: (1) attack density, (2) incidence of blue stain fromOphiostomafungi and (3) frequency of lesions in plant tissue around points of attack. A preliminary life table for S.noctilioin Galicia estimated effects on potential population growth rate from (in decreasing order of importance) host suitability, unequal sex ratio, parasitic nematodes and Hymenoptera parasitoids.
M.J. Lombardero; M.P. Ayres; Flora Krivak-Tetley; K.N.E. Fitza. Population biology of the European woodwasp,Sirex noctilio, in Galicia, Spain. Bulletin of Entomological Research 2016, 106, 569 -580.
AMA StyleM.J. Lombardero, M.P. Ayres, Flora Krivak-Tetley, K.N.E. Fitza. Population biology of the European woodwasp,Sirex noctilio, in Galicia, Spain. Bulletin of Entomological Research. 2016; 106 (5):569-580.
Chicago/Turabian StyleM.J. Lombardero; M.P. Ayres; Flora Krivak-Tetley; K.N.E. Fitza. 2016. "Population biology of the European woodwasp,Sirex noctilio, in Galicia, Spain." Bulletin of Entomological Research 106, no. 5: 569-580.