The Bio-Geo-Socio-Chemistry of Home Lawns.

In the Baltimore Ecosystem Study, one of two urban long-term ecological research (LTER) projects funded by the U.S. National Science Foundation, we home lawns are a major focus.  A series of long-term study plots are used to compare nitrogen (N) and carbon (C) dynamics (nitrate leaching, nitrous oxide, carbon dioxide and methane fluxes, potential net N mineralization and nitrification, microbial biomass C and N content) in forests and home lawns. The plot work is set in the context of watershed-scale N mass balances and social science research on human values, preferences and actions related to home lawn management.  Between 2001 and 2005, annual NO₃^- leaching ranged from 0.05 to 4.1 g N m^-2 y^-1 and was higher in grass than forest plots, except in a very dry year and when a disturbed forest plot was included in the analysis. N₂O fluxes ranged from 0.05 to more than 0.3 g N m^-2 y^-1 with few differences between grass and forest plots, and markedly higher fluxes in wet years.  Differences in NO₃^-  leaching and N₂O flux between forests and grasslands were not as high as expected given the higher frequency of disturbance and fertilization in the grasslands.  CO₂ flux, organic matter, microbial biomass and ¹⁵N retention were as high or higher in urban grasslands than in forests, suggesting that active C cycling creates sinks for N in vegetation and soil in these ecosystems.  Lawncare expenditures and management intensity varied markedly and were related to mappable lifestyle behavior indicators. While urban grasslands export more N to the environment than native forests, they have considerable capacity for N retention.  There is potential to manage and increase this retention, but only if human behavior is considered along with biogeochemical processes in integrated bio-geo-socio-chemical research, education and management plans.