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- Creators: Mozart, Wolfgang Amadeus, 1756-1791
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.
Fourteen native lizard species inhabit the desert surrounding Phoenix, AZ, USA, but only two species persist within heavily developed areas. This pattern is best explained by a combination of socioeconomic status, land cover, and location. Lizard diversity is highest in affluent areas and lizard abundance is greatest near large patches of open desert. The percentage of building cover has a strong negative impact on both diversity and abundance. Despite Phoenix's intense urban heat island effect, which strongly constrains the potential activity and microhabitat use of lizards in summer, thermal patterns have not yet impacted their distribution and relative abundance at larger scales.
Using satellite telemetry and remote sensing, I investigated three aspects of the Asian Great Bustard’s ecology critical to its conservation: migratory routes, migratory cues, and habitat use patterns. I found that Asian Great Bustards spent one-third of the year on a 2000 km migratory pathway, a distance twice as far as has previously been recorded for the species. Tracked individuals moved nomadically over large winter territories and did not repeat migratory stopovers, complicating conservation planning. Migratory timing was variable and migratory movements were significantly correlated with weather cues. Specifically, bustards migrated on days when wind support was favorable and temperature presaged warmer temperatures on the breeding grounds (spring) or advancing winter weather (fall). On the breeding grounds, Asian Great Bustards used both steppe and wheat agriculture habitat. All recorded reproductive attempts failed, regardless of habitat in which the nest was placed. Agricultural practices are likely to intensify in the coming decade, which would present further challenges to reproduction. The distinct migratory behavior and habitat use patterns of the Asian Great Bustard are likely adaptations to the climate and ecology of Inner Asia and underscore the importance of conserving these unique populations.
My research indicates that conservation of the Asian Great Bustard will require a landscape-level approach. This approach should incorporate measures at the breeding grounds to raise reproductive success, alongside actions on the migratory pathway to ensure appropriate habitat and reduce adult mortality. To secure international cooperation, I proposed that an increased level of protection should be directed toward the Great Bustard under the Convention on Migratory Species (CMS). That proposal, accepted by the Eleventh Conference of Parties to CMS, provides recommendations for conservation action and illustrates the transdisciplinary approach I have taken in this research.