The nutrient plasticity of moss-dominated crust in the urbanized Sonoran Desert

In deserts, moss-dominated crusts may play an important role in terrestrial-aquatic and aboveground-belowground connections. Despite its importance, very little is known about moss's role in biogeochemical cycles and how nutrient pulses (e.g., from N deposition in air pollution) will affect their functional significance as an integrator of nutrient cycling in deserts. Moss and soil were sampled from 15 sites in the Sonoran Desert in and around Phoenix, covering the city core subject to N deposition and rural areas to the east and west. Samples were analyzed for C, N, P and micronutrient content to compare moss stoichiometry over a gradient of soil resource availability. Moss %N and %P were positively correlated with soil N and P. Thus, sites in the city core subject to N deposition tended to have higher soil N and therefore higher moss N than the sites outside the city core. Micronutrient content varied with sampling region but was not related to soil content. Results suggest that moss can take up excess N,, but overall coverage of moss is lower in the city, limiting its ability to act as a N sink.