Improved productivity, water yield, and water use efficiency by incorporating switchgrass cultivation and native ecosystems in an integrated biofuel feedstock system

Abstract

The southern Great Plains of the USA has great potential to produce biofuel feedstock while minimizing the dual stresses of woody plant encroachment and climate change. Switchgrass (Panicum virgatum) cultivation, woody biomass captured during removal of the encroaching eastern redcedar (Juniperus virginiana) to restore grasslands and thinning of the native oak forest can provide an integrated source of feedstock and improve ecosystem services. In north‐central Oklahoma, we quantified productivity and ecosystem water use of switchgrass stands and degraded ecosystems encroached by eastern redcedar and compared these to native oak forest and tallgrass prairie ecosystems. We measured aboveground net primary productivity (ANPP) using allometric equations (trees) and clip plots (herbaceous), and evapotranspiration (ET) using a water balance approach from gauged watersheds, and calculated water use efficiency (WUE = ANPP/ET) from 2016 to 2019. Among vegetation cover types, ANPP averaged 5.1, 5.4, 6.0, and 7.8 Mg ha−1 year−1 for the prairie, oak, eastern redcedar, and switchgrass watersheds and was significantly greater for switchgrass in 2018 and 2019 (2 and 3 years post establishment) when it reached 8.6 Mg ha−1 year−1. Averaged across 2017–2019, ET was significantly greater in the forested watersheds than the grassland watersheds (1022 mm year−1 for eastern redcedar, 1025 mm year−1 for oak, 874 mm year−1 for prairie, and 828 mm year−1 for switchgrass). The mean WUE was significantly greater (9.47 kg ha−1 mm−1) for switchgrass than for the prairie, eastern redcedar, and oak cover types (6.03, 6.02, and 5.31 kg ha−1 mm−1). Switchgrass offered benefits of greater ANPP, less ET, and greater WUE. Our findings indicate that an integrated biofuel feedstock system that includes converting eastern redcedar encroached areas to switchgrass and thinning the oak forest can increase productivity, increase runoff to streams, and improve ecosystem services.

Assessing efficacy of cellular transmission technology in camera trapping for wildlife research

“…The Cross Timbers region includes both deciduous forest and grasslands (Starr et al 2019) and is characterized by post oak ( Quercus stellata ) and blackjack oak ( Q. marilandica ) of variable tree densities interspersed with patches of tallgrass prairie and shrubland (Joshi et al 2019). The CTER is 710 hectares with an elevation of 330 m, average high and low temperatures of 33.3°C and −3.2°C, respectively, and annual average precipitation of 880 mm (Schmidt et al 2020). For our class project, we used a 379‐hectare portion of the property that had adequate road access and was not associated with other ongoing research projects (Figure 1).…”

Response of Surface Runoff and Sediment to the Conversion of a Marginal Grassland to a Switchgrass (Panicum virgatum) Bioenergy Feedstock System

“…When the cultivation ceased, the watersheds reverted to grassland (also called "prairie" to differentiate it from switchgrass). On the basis of the cover, the vegetation was composed of approximately 85% graminoid and 15% forb [1]. The watershed to the southwest was 2.28 ha, and the watershed to the northeast was 3.32 ha.…”

“…After the switchgrass was established, the relative runoff among the watersheds did not differ from that of the calibration phase. Since the annual aboveground productivity of the Impact Watershed was substantially greater than the grassland Control Watershed during the switchgrass phase [1], this indicated that the switchgrass was more efficient in that it used less water to produce more growth. One result that was somewhat surprising was that the sediment load was significantly lower in the planted switchgrass system, which contrasts with our general understanding of the coproduction between the surface runoff and the sediment loads.…”

“…Carbon assimilation and ecosystem water use are tightly linked in the transitional land system between the semiarid and subhumid regions. Changes in the land use and ecosystem productivity will likely alter the ecosystem water use and the land and water system dynamics [1,2]. Water resources for environmental and municipal use in transitional land systems, such as in the southern Great Plains (SGP) of the United States, and similar transitional land systems between humid and arid zones around the globe, are critical to agricultural production and are vulnerable to land-cover and land-use alterations.…”

“…The SGP region has adequate precipitation and sufficiently productive soils for producing switchgrass, which is a perennial grass that is native to the area, and which is a species that has been identified as suitable for bioenergy production by the U.S. Department of Energy [24][25][26], in large part because of its high productivity. Switchgrass produced ~50% more aboveground biomass than the adjacent prairie in northcentral Oklahoma [1]. Growing energy crops on the marginal land in the SGP could reduce the government payments to the CRP land while sustaining the environmental benefits from perennial vegetation cover on highly erodible land.…”