Abstract
Lawns as a landcover change substantially alter evapotranspiration, CO2, and energy exchanges and are of rising importance considering their spatial extent. We contrast eddy covariance (EC) flux measurements collected in the Denver, Colorado, USA metropolitan area in 2011 and 2012 over a lawn and a xeric tallgrass prairie. Close linkages between seasonal vegetation development, energy fluxes, and net ecosystem exchange (NEE) of CO2 were found. Irrigation of the lawn modified energy and CO2 fluxes and greatly contributed to differences observed between sites. Due to greater water inputs (precipitation + irrigation) at the lawn in this semi-arid climate, energy partitioning at the lawn was dominated by latent heat (LE) flux. As a result, evapotranspiration (ET) of the lawn was more than double that of tallgrass prairie (2011: 639(±17) mm vs. 302(±9) mm; 2012: 584(±15) mm vs. 265(±7) mm). NEE for the lawn was characterized by a longer growing season, higher daily net uptake of CO2, and growing season NEE that was also more than twice that of the prairie (2011: −173(±23) g C m−2 vs. -81(±10) g C m−2; 2012: −73(±22) g C m−2 vs. -21(±8) g C m−2). During the drought year (2012), temperature and water stress greatly influenced the direction and magnitude of CO2 flux at both sites. The results suggest that lawns in Denver can function as carbon sinks and conditionally contribute to the mitigation of carbon emissions - directly by CO2 uptake and indirectly through effects of evaporative cooling on microclimate and energy use.
Highlights
The exchange of energy, water, and greenhouse gases of terrestrial ecosystems with the atmosphere and the resulting feedbacks on climate and biogeochemical cycles has put them in the focus of science (Heimann and Reichstein 2008; Arneth et al 2010)
This study demonstrated that an urban lawn and xeric tallgrass prairie differ notably with regard to net ecosystem exchange (NEE) of CO2, energy partitioning, and ET, a finding that appears most relevant considering the present rapid expansion of urban areas such as Denver and predicted future urban growth
Close links were found between seasonal vegetation development (i.e., Leaf area index (LAI)), energy fluxes, and NEE of CO2
Summary
The exchange of energy, water, and greenhouse gases of terrestrial ecosystems with the atmosphere and the resulting feedbacks on climate and biogeochemical cycles has put them in the focus of science (Heimann and Reichstein 2008; Arneth et al 2010). The uptake of CO2 by vegetation varies spatially and temporally and is strongly influenced by management (Oncley et al 1997; Katul et al 2001; Leuning et al 2004; Ma et al 2007; Baldocchi 2008; Davis et al 2010; Eugster et al 2010). The prairies of the Great Plains, as the dominant grasslands of North America, have been dramatically impacted by land use change, mostly for agricultural production (Suttie et al 2005). Another anthropogenic impact is the conversion to urban land use. Urban ecosystems currently cover a relatively small fraction of the land surface in the United States (US) (3–5%), they are expanding rapidly
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
