| Title: | Hydrologic cost-effectiveness ratio favors switchgrass production on marginal croplands over existing grasslands |
| Authors: | Yimam, Y.D., T.E. Ochsner and G.A. Fox |
| Year: | 2017 |
| Journal: | PLoS ONE |
| Volume (Issue): | 12(8) |
| Pages: | |
| Article ID: | e0181924 |
| DOI: | 10.1371/journal.pone.0181924 |
| URL (non-DOI journals): | |
| Model: | SWAT |
| Broad Application Category: | hydrologic only |
| Primary Application Category: | land use change assessment |
| Secondary Application Category: | bioenergy crop, tree and/or vegetation assessment |
| Watershed Description: | 1063 km^2 Skeleton Creek, located in north-central Oklahoma, U.S. |
| Calibration Summary: | |
| Validation Summary: | |
| General Comments: | |
| Abstract: | Switchgrass (Panicum virgatum L.) has attracted attention as a promising second generation
biofuel feedstock. Both existing grasslands and marginal croplands have been suggested
as targets for conversion to switchgrass, but the resulting production potentials and
hydrologic impacts are not clear. The objectives of this study were to model switchgrass production
on existing grasslands (scenario-I) and on marginal croplands that have severe to
very severe limitations for crop production (scenario-II) and to evaluate the effects on evapotranspiration
(ET) and streamflow. The Soil and Water Assessment Tool (SWAT) was
applied to the 1063 km2 Skeleton Creek watershed in north-central Oklahoma, a watershed
dominated by grasslands (35%) and winter wheat cropland (47%). The simulated average
annual yield (2002±2011) for rainfed Alamo switchgrass for both scenarios was 12 Mg ha-1.
Yield varied spatially under scenario-I from 6.1 to 15.3 Mg ha-1, while under scenario-II the
range was from 8.2 to 13.8 Mg ha-1. Comparison of average annual ET and streamflow
between the baseline simulation (existing land use) and scenario-I showed that scenario-I
had 5.6% (37 mm) higher average annual ET and 27.7% lower streamflow, representing a
40.7 million m3 yr-1 streamflow reduction. Compared to the baseline, scenario-II had only
0.5% higher ET and 3.2% lower streamflow, but some monthly impacts were larger. In this
watershed, the water yield reduction per ton of biomass production (i.e. hydrologic cost effectiveness
ratio) was more than 5X greater under scenario-I than under scenario-II.
These results suggest that, from a hydrologic perspective, it may be preferable to convert
marginal cropland to switchgrass production rather than converting existing grasslands. |
| Language: | English |
| Keywords: | |