Implications for the hydrologic cycle under climate change due to the expansion of bioenergy crops in the Midwestern United States

Abstract

To meet emerging bioenergy demands, significant areas of the large-scale agricultural landscape of the Midwestern United States could be converted to second generation bioenergy crops such as miscanthus and switchgrass. The high biomass productivity of bioenergy crops in a longer growing season linked tightly to water use highlight the potential for significant impact on the hydrologic cycle in the region. This issue is further exacerbated by the uncertainty in the response of the vegetation under elevated CO 2 and temperature. We use a mechanistic multilayer canopy-root-soil model to (i) capture the eco-physiological acclimations of bioenergy crops under climate change, and (ii) predict how hydrologic fluxes are likely to be altered from their current magnitudes. Observed data and Monte Carlo simulations of weather for recent past and future scenarios are used to characterize the variability range of the predictions. Under present weather conditions, miscanthus and switchgrass utilized more water than maize for total seasonal evapotranspiration by approximately 58% and 36%, respectively. Projected higher concentrations of atmospheric CO 2 (550 ppm) is likely to decrease water used for evapotranspiration of miscanthus, switchgrass, and maize by 12%, 10%, and 11%, respectively. However, when climate change with projected increases in air temperature and reduced summer rainfall are also considered, there is a net increase in evapotranspiration for all crops, leading to significant reduction in soil-moisture storage and specific surface runoff. These results highlight the critical role of the warming climate in potentially altering the water cycle in the region under extensive conversion of existing maize cropping to support bioenergy demand.R apidly growing energy demand, worldwide depletion of fossil fuels, and global warming are raising an interest in expanding clean and renewable bioenergy production. In the United States, the current starch-based bioethanol production only contributes a small portion of total energy needs (1, 2), but it is raising new challenges related to environmental issues (3-6) and a competition with food production on available fertile land (7). Bioenergy extracted from lignocellulosic feedstocks offers the possible use of marginal land (8), along with many energy, environmental, and economic advantages over current biofuel sources (9), and is being considered as a promising alternative to sustainably meet the US Department of Energy target for bioenenergy and biobased products in the future (10). At present, Miscanthus × giganteus (miscanthus) and Panicum virgatum (switchgrass) are considered as the two perennial grasses with the highest potential for lignocellulosic bioenergy production in the Midwest with high biofuels yield per unit land area, reduced requirement of nutrient inputs (11, 12), and low net CO 2 emissions (13-16). However, if large portions of the landscape in the Midwestern United States are converted to these crops for meeting bioenergy demands, for example, by using l...

Biomass sorghum and maize have similar water-use-efficiency under non-drought conditions in the rain-fed Midwest U.S.

“…Growing season duration has been shown to impact regional hydrology through changes in ET and drainage . Additionally, increases in LAI have been shown to increase ET (Le et al, 2011), suggesting that the relatively large and prolonged LAI of biomass sorghum could support significant ET late into the growing season. Dense crop canopies and intensely managed agroecosystems have been shown to reduce maximum summertime temperatures in the Corn Belt (i.e.…”

Comparative analysis of hydrologic signatures in two agricultural watersheds in east-central Illinois: legacies of the past to inform the future

“…At the end of the growing season, ET of corn and soybeans declines and ends a few weeks before harvest, which usually occurs at the beginning of October, but Miscanthus continues to transpire until the first frosts, usually in November (Schilling et al, 2008;McIsaac et al, 2010;Le et al, 2011), so that its growing season is two months or more longer than the current row crop annuals. In addition, the canopy of Miscanthus is much more dense than that of corn or soybeans, with a maximum leaf area index (LAI) of up to 10 compared to 7 for soybeans and 5.5 for corn (Heaton et al, 2008;Le et al, 2011) which would also intercept more water than the annual crops, thus reducing throughfall in addition to drying the soil profile earlier in the year . In a tiledrained watershed, this could mean that the local streams become baseflow-dependent earlier in the year than under row crops, and, in dry years especially, experience larger and/or longer deficit periods during the summer low flow season.…”

“…Both field experiments Smith et al, 2013) and watershed-scale modeling experiments (Ng et al, 2010) have shown that less nitrate is exported from Miscanthus compared to conventional corn crops. However, recent field experiments Hickman et al, 2010) and canopy-scale modeling studies (Le et al, 2011) have also shown that water usage by Miscanthus is significantly greater than that of corn or soybeans. If large-scale planting of these biomass crops is to be sustainable, it is essential to understand how watersheds as a whole might respond to this change and be aware of possible negative outcomes.…”

Catalysis for Biomass and CO2 Use Through Solar Energy: Opening New Scenarios for a Sustainable and Low-Carbon Chemical Production

“…Bioenergy crops, e.g., switchgrass and miscanthus, can transpire as much as 38% more than corn over a growing season [20]. Replacing traditional annual cropping systems with switchgrass in the Midwest and High Plains may cause additional stress to water resources because the agricultural crop production in large portions of these areas (e.g., Kansas and Nebraska) is dependent upon irrigation water from already stressed local resources [21].…”

“…Change in land cover thus has the potential to impact local and regional climate through alteration of the energy and moisture balances of the land surface [14][15][16][17][18]. The longer growing season and greener vegetative cover of biofuel crops result in higher water loss to the atmosphere through evapotranspiration (ET), decline in soil water depth [17,19] and reduced surface runoff [20] relative to annual cropping systems. Changes in soil moisture and runoff determine streamflow, groundwater recharge and influence water quality.…”