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Changes in nitrification rates due to climate change have the potential to influence soil nitrogen availability, water quality, and greenhouse gas emissions. However, the mechanisms through which temperature and precipitation affect nitrification and the nitrifying microbial community in the field are largely unknown. We examined the effects of warming (up to ~4°C) and altered precipitation (−50%, ambient, +50%) on potential nitrification kinetics, or potential nitrification rates over a range of ammonium (NH 4 + ) concentrations. We also examined responses of the abundance and composition of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB), which play a critical role in nitrification. This work took place over two years in an old-field ecosystem in Massachusetts, USA, as part of the Boston-Area Climate Experiment (BACE). Across all dates and during June and August 2010, drought decreased the half-saturation constant, K m , or the concentration of NH 4 + at the half-maximal potential nitrification rate. AOB composition responded to the main and interactive effects of warming and precipitation, and warming decreased AOA abundance by 82% during January 2009. Although K m , AOB composition, and AOA abundance responded to the treatments to some degree, potential nitrification kinetics were generally uncorrelated with AO composition or abundance. Sampling date also had a greater effect on potential nitrification kinetics and AO than the treatments themselves, and these larger temporal fluctuations may have masked any correlations between nitrification kinetics and AO. Our results demonstrate that the effect of warming and altered precipitation on AO and nitrification kinetics must be considered in the context of broader temporal variations in AO composition, AO abundance, and nitrification kinetics.

Understanding the structure and function of urban landscapes requires integrating social and ecological research. Here, we integrate parallel social and ecological assessments of natural areas within New York City. We examined social data (from a rapid assessment of park use and meaning, collected at a park zone level) alongside ecological data (from a plot-based assessment of forest structure and diversity). In-depth interviews with researchers and managers (n = 11) involved with the social and ecological assessments revealed commonly-held values considered critical for integration, including clear communication, openness, trust, and shared goals and also identified barriers to the integration process, including the scales at which each dataset was collected. We applied an informed, shared problem framing to investigate the relationships between visitor use and ecological condition in urban natural areas. We began with fuzzy cognitive modeling, where researchers developed models of defining a “healthy urban forest.” We then developed two social-ecological typologies to examine the integrated dataset in relation to how visitors may affect or perceive ecological health and threat. Typologies identify NYC natural areas where social indicators (number of visitors, diversity of park use motivations) are either high or low and ecological condition is either high or low. Examination of these typologies led to exploring correlations between social and ecological variables, to team discussions, and to developing new research questions. We conclude this paper with a discussion of tradeoffs of this type of emergent, integrative approach to social-ecological synthesis research.