Drylands, though one of the largest biomes, are also one of the most understudied biomes on the planet. This leaves scientists with limited understanding of unique life forms that have adapted to live in these arid environments. One such life form is the hypolithic microbial community; these are autotrophic cyanobacteria colonies that can be found on the underside of translucent rocks in deserts. With the light that filters through the rock above them, the microbes can photosynthesize and fix carbon from the atmosphere into the soil. In this study I looked at hypolith-like rock distribution in the Namib Desert by using image recognition software. I trained a Mask R-CNN network to detect quartz rock in images from the Gobabeb site. When the method was analyzed using the entire data set, the distribution of rock sizes between the manual annotations and the network predictions was not similar. When evaluating rock sizes smaller than 0.56 cm2 the method showed statistical significance in support of being a promising data collection method. With more training and corrective effort on the network, this method shows promise to be an accurate and novel way to collect data efficiently in dryland research.

The majority of trust research has focused on the benefits trust can have for individual actors, institutions, and organizations. This “optimistic bias” is particularly evident in work focused on institutional trust, where concepts such as procedural justice, shared values, and moral responsibility have gained prominence. But trust in institutions may not be exclusively good. We reveal implications for the “dark side” of institutional trust by reviewing relevant theories and empirical research that can contribute to a more holistic understanding. We frame our discussion by suggesting there may be a “Goldilocks principle” of institutional trust, where trust that is too low (typically the focus) or too high (not usually considered by trust researchers) may be problematic. The chapter focuses on the issue of too-high trust and processes through which such too-high trust might emerge. Specifically, excessive trust might result from external, internal, and intersecting external-internal processes. External processes refer to the actions institutions take that affect public trust, while internal processes refer to intrapersonal factors affecting a trustor’s level of trust. We describe how the beneficial psychological and behavioral outcomes of trust can be mitigated or circumvented through these processes and highlight the implications of a “darkest” side of trust when they intersect. We draw upon research on organizations and legal, governmental, and political systems to demonstrate the dark side of trust in different contexts. The conclusion outlines directions for future research and encourages researchers to consider the ethical nuances of studying how to increase institutional trust.

Drylands cover almost half of the land surface on Earth, yet there is still little understood of the processes in these ecosystems. This project studied the impact of macroclimate (precipitation and temperature in large regions) in comparison to microclimate (the climate under canopy versus in the open) to learn more about the drivers of litter decomposition in drylands.

Nitrogen is an essential, often limiting, element for biological growth that can act as a pollutant if present in excess. Nitrogen is primarily transported by water from uplands to streams and eventually to recipient lakes, estuaries, and wetlands, but can be modulated by biological uptake and transformation along these flowpaths. As a result, nitrogen can accumulate in aquatic ecosystems if supply is high or if biological retention is low. Dryland and urban ecosystems offer interesting contrasts in water supply, which limits transport and biological activity in drylands, and nitrogen supply that increases with human activity. In my dissertation, I ask: What is the relative balance among nitrogen retention, removal, and transport processes in dryland watersheds, and what is the fate of exported nitrogen? My dissertation research demonstrates that water is a major control on where and when nitrogen is retained and removed versus exported to downstream ecosystems. I used a mass-balance model based on synoptic surveys to study seasonal and spatial patterns in nitrate loading to a dryland stream network. I found that irrigation diversions transport nitrate from agricultural areas to the stream network year-round, even during dry seasons, and are an important driver of nitrate loading. I further explored how seasonal precipitation influences flood nutrient export in an intermittent desert stream by coupling long-term data of flood-water chemistry with stream discharge and precipitation data. I found that higher precipitation prior to a flood fills water storage sites in the catchment, leading to larger floods. In addition, higher antecedent precipitation stimulates biological nitrogen retention in the uplands, leading to lower nitrogen concentration in floods. Finally, I evaluated the consequences of nitrogen export from watersheds on how urban wetlands attenuate nitrate through denitrification that permanently removes nitrogen, and dissimilatory nitrate reduction to ammonium (DNRA) that retains nitrogen in another biologically reactive form. I found that DNRA becomes proportionally more important with low nitrate concentration, thereby retaining nitrogen as ammonium. Collectively, my dissertation research addresses how dryland and urban ecosystems can be integrated into models of watershed nitrogen cycling.