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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. [ABSTRACT FROM AUTHOR]

Abstract: Intercropping switchgrass (Panicum virgatum) between rows in managed pine stands is a potential, emerging method for biofuel feedstock production in forestry systems. Switchgrass intercropping likely alters vegetation characteristics within a stand by increasing herbaceous vegetation cover and thus influences insect communities positively. However, its effect may vary with stand age, which often determines canopy closure and vegetation structure within a stand: effects of switchgrass intercropping may be stronger in old pine stands with a closed canopy than in young pine stands with an open canopy. We examined how switchgrass intercropping and stand age, namely 3–4‐year‐old pine (YPine) and 8–9‐year‐old pine (OPine), influenced insect abundance and diversity in loblolly pine (Pinus taeda) stands in Mississippi, U.S.A., during May to August 2013–2014. We captured insects at 36 locations throughout 12 stands (three stands per each of four treatments; intercropping and non‐intercropping treatment in YPine and OPine stands), using pan traps. Abundance and family level richness were greater in YPine stands and Shannon–Wiener diversity and evenness at family level was higher in OPine stands both years. However, insect abundance and diversity did not differ between intercropping and non‐intercropping treatments. Community composition was also influenced by stand age, which explained > 90% of constrained inertia, rather than switchgrass intercropping. Our findings suggest that switchgrass intercropping is unlikely to significantly affect insect communities in managed pine stands, whereas stand age, as well as associated successional changes, can be a main factor affecting insects, as often observed in other animal taxa in managed pine landscapes. [ABSTRACT FROM AUTHOR]

Perennial grasses are promising candidates for bioenergy crops, but species that can escape cultivation and establish self-sustaining naturalized populations (feral) may have the potential to become invasive. Fertile Miscanthus × giganteus, known as 'PowerCane,' is a new potential biofuel crop. Its parent species are ornamental, non-native Miscanthus species that establish feral populations and are sometimes invasive in the USA. As a first step toward assessing the potential for 'PowerCane' to become invasive, we documented its growth and fecundity relative to one of its parent species ( Miscanthus sinensis) in competition with native and invasive grasses in common garden experiments located in Columbus, Ohio and Ames, Iowa, within the targeted range of biofuel cultivation. We conducted a 2-year experiment to compare growth and reproduction among three Miscanthus biotypes-'PowerCane,' ornamental M. sinensis, and feral M. sinensis-at two locations. Single Miscanthus plants were subjected to competition with a native grass ( Panicum virgatum), a weedy grass ( Bromus inermis), or no competition. Response variables were aboveground biomass, number of shoots, basal area, and seed set. In Iowa, all Miscanthus plants died after the first winter, which was unusually cold, so no further results are reported from the Iowa site. In Ohio, we found significant differences among biotypes in growth and fecundity, as well as significant effects of competition. Interactions between these treatments were not significant. 'PowerCane' performed as well or better than ornamental or feral M. sinensis in vegetative traits, but had much lower seed production, perhaps due to pollen limitation. In general, ornamental M. sinensis performed somewhat better than feral M. sinensis. Our findings suggest that feral populations of 'PowerCane' could become established adjacent to biofuel production areas. Fertile Miscanthus × giganteus should be studied further to assess its potential to spread via seed production in large, sexually compatible populations. [ABSTRACT FROM AUTHOR]

This article assesses the potential of California agriculture to supply biofuel feedstock in the form of switchgrass. We construct a fully calibrated, multiregion, multi-input and multioutput model of agricultural supply for California's Central Valley based on the principles of positive mathematical programming. We exploit agronomic information obtained from a biophysical model to estimate regional production functions for switchgrass. The model predicts the extent and location of potential feedstock production in the Central Valley. Our results suggest that switchgrass adoption rates differ widely among agricultural regions, and that switchgrass is not likely to displace specialty crops by much statewide. [ABSTRACT FROM AUTHOR]

Biofuel crops may help achieve the goals of energy-efficient renewable ethanol production and greenhouse gas ( GHG) mitigation through carbon (C) storage. The objective of this study was to compare the aboveground biomass yields and soil organic C ( SOC) stocks under four crops (no-till corn, switchgrass, indiangrass, and willow) 7 years since establishment at three sites in Ohio to determine if high-yielding biofuel crops are also capable of high levels of C storage. Corn grain had the highest potential ethanol yields, with an average of more than 4100 L ha−1, and ethanol yields increased if both corn grain and stover were converted to biofuel, while willow had the lowest yields. The SOC concentration in soils under biofuels was generally unaffected by crop type; at one site, soil in the top 10 cm under willow contained nearly 13 Mg C ha−1 more SOC (or 29% more) than did soils under switchgrass or corn. Crop type affected SOC content of macroaggregates in the top 10 cm of soil, where macroaggregates in soil under corn had lower C, N and C : N ratios than those under perennial grasses or trees. Overall, the results suggest that no-till corn is capable of high ethanol yields and equivalent SOC stocks to 40 cm depth. Long-term monitoring and measurement of SOC stocks at depth are required to determine whether this trend remains. In addition, ecological, energy, and GHG assessments should be made to estimate the C footprint of each feedstock. [ABSTRACT FROM AUTHOR]