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Lilly, Paul J.

Natural Resources

2012

PhD

Turfgrass lawns make up a substantial fraction of the urbanized landscape in the United States, and a significant portion of land cover nationally, but C and N cycling in lawns is poorly understood. We used a full factorial, randomized complete block, split-plot design to test the effects of irrigation, mowing height, and fertilization on C and N stocks and fluxes in soil and biomass in a two-year-old stand of tall fescue (Festuca arundinacea Schreb.) appropriate for home lawns. Standing turfgrass biomass represented a small C stock but a surprisingly large N stock, comparable to a hardwood forest on a per-unit-area basis. Annual biomass production represented substantial fluxes of both Cand N, again comparable to other temperate ecosystems. Large C and N fluxes to and from biomass coincided with seasonal variations in total soil C and N stocks, and we measured net annual increases in soil C stocks in some (but not all) treatments. Management practices had minimal impact on average standing biomass stocks or on the C and N content of annual production, but significantly influenced the timing and magnitude of variation in stocks, and the relative contributions of different turf components to production. Management also influenced the magnitudes of seasonal changes in many soil variables, but rarely affected the overall seasonal pattern. Despite their small biomass, turfgrass lawns cycle large amounts of C and N, and management has important effects on when and how that cycling takes place.