|GOMEZ-CASANOVAS, NURIA - University Of Illinois|
|DELUCIA, NICHOLAS - University Of Illinois|
|DELUCIA, EVAN - University Of Illinois|
Submitted to: Global Change Biology Bioenergy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/25/2017
Publication Date: N/A
Interpretive Summary: Many changes are associated with transitioning managed, unmanaged, or marginal lands from one use to another. Among the obvious consequences associated with shifts in vegetation are changes in community structure and overall plant productivity, however, additional changes are likely to occur. These changes include the fluxes of greenhouse gases into or out of the ecosystems. Greenhouse gases are particularly important due to their ability to warm the atmosphere. One major land use change that is projected to occur involves transitioning from degraded lands to highly productive feedstocks for bioenergy production. This experiment tests how transitioning from low-productivity, grazed pastures to high productivity perennial grasses influence the fluxes of the three major greenhouse gases, CO2, N2O and CH4, associated with bioenergy production in Central Florida. Our results suggest that the conversion of pasture to energy cane will reduce GHGs emitted from soils and cattle. Improved understanding of land use impact on soil GHG dynamics will provide valuable information for decision makers debating sustainable bioenergy policies.
Technical Abstract: Changes in land use can profoundly affect the climate through variations in the emission of soil GHG. Global demands for biofuel feedstock is accelerating land use change by prompting the conversion of marginal land and managed ecosystems to highly productive second-generation bioenergy crops such as energy cane. Although the deployment of energy cane is a promising strategy to meet global bioenergy industry demands, few studies have investigated soil GHG fluxes in these crops and sub-tropical pasture with which they are competing for land. Here, we showed that soil N2O fluxes in bioenergy crops was higher (>250%) than those observed in pastures following fertilization at high soil wetness. In the absence of recent fertilization or under drier conditions the N2O source strength in energy cane and pasture sites was similar. Soils on grazed pastures were sources of CH4 during the wet season but weak sinks at lower soil moisture. Energy cane plantations were consistent weak sources of CH4 over a complete wet-dry seasonal cycle. The heterotrophic component of soil respiration was larger (139-155%) in pastures than in energy cane crops, suggesting lower decomposition of SOC in bioenergy crops. This study indicates that the GHG source strength of soils in these sub-tropical ecosystems is driven by changes in land use and seasonality including changes in soil moisture. In terms of global warming potential, grazed pastures were stronger (115-150%) soil GHG emitters than energy cane crops over a complete wet-dry seasonal cycle. Moreover, pastures became a substantial source of GHG emitters when including estimates of CH4 flux from cattle. Our results suggest that the conversion of pasture to energy cane will reduce GHGs emitted from soils and cattle. Improved understanding of land use impact on soil GHG dynamics will provide valuable information for decision makers debating sustainable bioenergy policies.