Hydrology and biogeochemistry are coupled in all systems. However, human decision-making regarding hydrology and biogeochemistry are often separate, even though decisions about hydrologic systems may have substantial impacts on biogeochemical patterns and processes. The overarching question of this dissertation was: How does hydrologic engineering interact with the effects of nutrient loading and climate to drive watershed nutrient yields? I conducted research in two study systems with contrasting spatial and temporal scales. Using a combination of data-mining and modeling approaches, I reconstructed nitrogen and phosphorus budgets for the northeastern US over the 20th century, including anthropogenic nutrient inputs and riverine fluxes, for ~200 watersheds at 5 year time intervals. Infrastructure systems, such as sewers, wastewater treatment plants, and reservoirs, strongly affected the spatial and temporal patterns of nutrient fluxes from northeastern watersheds. At a smaller scale, I investigated the effects of urban stormwater drainage infrastructure on water and nutrient delivery from urban watersheds in Phoenix, AZ. Using a combination of field monitoring and statistical modeling, I tested hypotheses about the importance of hydrologic and biogeochemical control of nutrient delivery. My research suggests that hydrology is the major driver of differences in nutrient fluxes from urban watersheds at the event scale, and that consideration of altered hydrologic networks is critical for understanding anthropogenic impacts on biogeochemical cycles. Overall, I found that human activities affect nutrient transport via multiple pathways. Anthropogenic nutrient additions increase the supply of nutrients available for transport, whereas hydrologic infrastructure controls the delivery of nutrients from watersheds. Incorporating the effects of hydrologic infrastructure is critical for understanding anthropogenic effects on biogeochemical fluxes across spatial and temporal scales.
Aboveground nitrogen content showed a maximum in 2011, decreasing until 2015, increasing again until 2017, and dropping in 2018; belowground nitrogen content showed the opposite temporal trend. Because foliar nitrogen content was assumed to be relatively constant over time, my data suggested that belowground nitrogen content increased between 2011 and 2015 and decreased between 2015 and 2017. Aboveground nitrogen content underwent fluctuations due to fluctuations in aboveground biomass. This occurred due to ‘thatching’, or events of widespread toppling of large macrophyte stands. The ratio of aboveground to belowground biomass can vary widely in the same CTW. My findings suggested that managing senesced aboveground plant material in CTWs may optimize the CTW’s ability to sequester nitrogen. Further research is needed to determine the best management strategies, as well as its possible implications.
This formula was used to estimate the nutrient uptake performance of aquatic primary producers from sampling observations; ANPP accounted for 16.26 metric tons of system wide N uptake, while aquatic ER contributed 6.07 metric tons N of nighttime remineralization and 5.7 metric tons of N throughout the water column during the day. The estimated yearly net aquatic N flux is 4.49 metric tons uptake, compared to about 12 metric tons yearly N uptake by the vegetated marsh (Treese, 2019). However, not accounting for animal respiration results in an underestimation of system-wide N remineralization, and not accounting for soil processes results in an underestimation of N uptake.
Based on existing research, state wildlife agencies should be diversifying their management activities to reflect both utilitarian and biocentric values. Yet agencies are still focused primarily on managing land and wildlife resources for hunting and fishing, partly because of revenues associated with permits and licenses (Jacobson et al., 2022; Manfredo, 2008). My research examines the values which state agencies emphasize in managing wildlife and engaging the public. Public-facing agency webpages are one way to investigate the values that drive agencies’ management priorities and activities. By looking at how information is represented on their main webpages, one can infer who the intended audience is, and which values guide their actions. Thus, my research aims to analyze how state management activities and associated information—as featured on their websites—represent public wildlife values and the trend away from utilitarianism (especially hunting and fishing) toward protectionism through wildlife conservation. Specifically, I ask: How do state-level wildlife agencies present and communicate wildlife management issues and reflect their different wildlife values—ranging from utilitarianism with emphasis on recreational use and enjoyment by people toward mutualist benefits that also protect wildlife—through their websites?
This paper identified issues related to the production and use of knowledge in the conservation management of the Galapagos and provided frameworks for facilitating efficient engagement and actionable science to overcome knowledge gaps. The literature emphasizes the need for usable knowledge and knowledge exchange mechanisms to ensure that research findings are translated into practical solutions. The partnership between the Galapagos National Park and the Darwin Research Station has the potential to facilitate knowledge exchange through practices such as co production of knowledge, embedded researchers, or actionable science.