Abstract
Remnants of native tallgrass prairie experience elevated atmospheric nitrogen (N) deposition in urban areas, with potential effects on species traits that are important for N cycling and species composition. We quantified bulk (primarily wet) inorganic N (NH4+-N + NO3--N) deposition at six sites along an urban development gradient (6–64% urban) in the Dallas-Fort Worth metropolitan area from April 2014 to October 2015. In addition, we conducted a phytometer experiment with two common native prairie bunchgrass species––one well studied (Schizachyrium scoparium) and one little studied (Nasella leucotricha)––to investigate ambient N deposition effects on plant biomass and tissue quality. Bulk inorganic N deposition ranged from 6.1–9.9 kg ha-1 yr-1, peaked in spring, and did not vary consistently with proportion of urban land within 10 km of the sites. Total (wet + dry) inorganic N deposition estimated using bulk deposition measured in this study and modeled dry deposition was 12.9–18.2 kg ha-1 yr-1. Although the two plant species studied differ in photosynthetic pathway, biomass, and tissue N, they exhibited a maximum 2-3-fold and 2-4-fold increase in total biomass and total plant N, respectively, with 1.6-fold higher bulk N deposition. In addition, our findings indicate that while native prairie grasses may exhibit a positive biomass response to increased N deposition up to ~18 kg ha-1 yr-1, total inorganic N deposition is well above the estimated critical load for herbaceous plant species richness in the tallgrass prairie of the Great Plains ecoregion and thus may negatively affect these plant communities.
Highlights
Over the past decade, there has been a surge in research on nitrogen (N) deposition in cities around the world (e.g., [1,2,3,4,5,6])
The research was conducted in the Dallas-Fort Worth (DFW) metropolitan area, Texas (Fig 1)
Bulk inorganic N deposition measured in DFW ranged from 6.1 to 9.9 kg ha-1 yr-1 across sites (Table 1)
Summary
There has been a surge in research on nitrogen (N) deposition in cities around the world (e.g., [1,2,3,4,5,6]). Much of the current understanding of plant responses to and recovery from N addition is derived from experimental field manipulations which are most often conducted in plant communities outside the influence of urban air pollution (e.g., [10,11,12,13,14,15]). These studies show that individual plants exposed to elevated levels of N deposition often exhibit changes in biomass, resource allocation (e.g., root:shoot ratio), and tissue quality in the form of decreased carbon (C) to N ratio. Lower C:N ratios have the potential to affect energy transfer to higher trophic levels by increasing the palatability of tissues to herbivores (e.g., [16])
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
