The Utility of Tallgrass Prairie Reconstructions as Bioenergy Feedstocks

Two of the more pressing, yet opposing, ecological challenges that we face at the global-scale are the loss of biodiversity and rising demand for energy. Many ecological experiments have shown the importance of biodiversity for ecosystem services and functions, but the simultaneous demand for energy has led to greater conversion of natural landscapes to low-diversity energy production crops (e.g., corn for ethanol). One potential solution to these seemingly opposing issues would be to grow diverse native vegetation for bioenergy. Native tallgrass prairie produces large amounts of aboveground biomass but also provides great habitat for wildlife and other ecosystem services. In this study, we compared the productivity, yearly biomass variability, and invasion resistance of four potential bioenergy feedstocks with contrasting diversity: 1 species - a switchgrass monoculture; 5 species - a mix of C4 grasses; 16 species - a mix of grasses, forbs and legumes; and 32 species - a mix of grasses, forbs, and legumes. Each diversity treatment was replicated four times on three different soil types (clay, loam, and sand soil) for a total of 48 plots (0.33-0.56ha each). We compared productivity by harvesting all plant material to ground level in 10 randomly placed 0.3m2 quadrats per plot. Weed biomass was compared using basal area sampling of 10 randomly placed 0.1m2 quadrats per plot. Across soil types, the 1, 16 and 32 treatments produced the same amount of aboveground biomass over the 5-yr study, with the 1 treatment producing significantly more biomass than the 5 treatment. Despite the overall similarity between the 1, 16, and 32 treatments, the relative ranking of the four diversity treatments varied depending on soil type. Weed biomass was higher in low-diversity treatments than high-diversity treatments. Year-to-year variation in productivity did not differ between treatments. As we attempt to meet the bioenergy goals mandated by the Energy Policy Act (2005) and Energy Independence and Security Act (2007), our results indicate that diverse mixtures of native tallgrass prairie plants are a reliable source of bioenergy and also provide the ecosystem benefits associated with increased diversity. However, variation in the relative productivity of the four diversity mixtures on different soil types suggests that seed mixes of bioenergy crops must be tailored to their specific site for maximum productivity and stand success

Above- and belowground biomass and soil respiration in a low-input perennial biofuel production system

Backgroud Global climate change largely depends on the atmospheric carbon balance, of which soil respiration is a significant component. Native perennial prairie vegetation is being tested as an alternative to corn for renewable biofuel production. Mixtures of this vegetation are considered ‘carbon negative’ because net CO2 sequestration exceeds atmospheric release1. Studies have shown that aboveground biomass and the rate of carbon sequestration are both increased by planting a diverse mixture of species versus a monoculture1. Research Question: How does the diversity of biofuel vegetation mixtures affect soil respiration, aboveground biomass and belowground biomass

Productivity and resistance to weed invasion in four prairie biomass feedstocks with different diversity

High-diversity mixtures of native tallgrass prairie vegetation should be effective biomass feedstocks because of their high productivity and low input requirements. These diverse mixtures should also enhance several of the ecosystem services provided by the traditional monoculture feedstocks used for bioenergy. In this study, we compared biomass production, year-to-year variation in biomass production, and resistance to weed invasion in four prairie biomass feedstocks with different diversity: one species – a switchgrass monoculture; five species – a mix of C4 grasses; 16 species – a mix of grasses, forbs, and legumes; and 32 species – a mix of grasses, forbs, legumes, and sedges. Each diversity treatment was replicated four times on three soil types for a total of 48 research plots (0.33–0.56 ha each). We measured biomass production by harvesting all plant material to ground level in ten randomly selected quadrats per plot. Weed biomass was measured as a subset of total biomass. We replicated this design over a five-year period (2010–2014). Across soil types, the one-, 16-, and 32-species treatments produced the same amount of biomass, but the one-species treatment produced significantly more biomass than the five-species treatment. The rank order of our four diversity treatments differed between soil types suggesting that soil type influences treatment productivity. Year-to-year variation in biomass production did not differ between diversity treatments. Weed biomass was higher in the one-species treatment than the five-, 16-, and 32-species treatments. The high productivity and low susceptibility to weed invasion of our 16- and 32-species treatments supports the hypothesis that high-diversity prairie mixtures would be effective biomass feedstocks in the Midwestern United States. The influence of soil type on relative feedstock performance suggests that seed mixes used for biomass should be specifically tailored to site characteristics for maximum productivity and stand success

The James Webb Space Telescope Mission

Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least $4m$. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the $6.5m$ James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 years, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space Telescope Overview, 29 pages, 4 figure

The utility of high-diversity prairie mixtures as bioenergy feedstocks

Two of the more pressing, yet opposing, ecological challenges that we face at the global-scale are the loss of biodiversity and rising demand for energy. Many ecological experiments have shown the importance of biodiversity for ecosystem services and functions, but simultaneous demand for energy has led to greater conversion of natural landscapes to low-diversity energy crops (e.g., corn for ethanol). One potential solution to these seemingly opposing issues would be to grow diverse native vegetation for bioenergy. Native tallgrass prairie produces large amounts of aboveground biomass but also provides great habitat for wildlife and other ecosystem services. In this study, we compared the productivity, yearly biomass variability, and invasion resistance of four potential bioenergy feedstocks with contrasting diversity: 1 species - a switchgrass monoculture; 5 species - a mix of C4 grasses; 16 species - a mix of grasses, forbs and legumes; and 32 species - a mix of grasses, sedges, forbs, and legumes. Each diversity treatment was replicated four times on three different soil types (clay loam, loam, and sandy loam) for a total of 48 plots (0.33-0.56 ha each). We compared productivity by harvesting all plant material in 10 randomly placed 0.3m2 quadrats per plot. Species composition was compared using basal area sampling of 10 randomly placed 0.1m2 quadrats per plot. Across soil types, the 1-, 16-, and 32-species treatments produced the same amount of aboveground biomass over the 5-yr study, with the 1-species treatment producing more biomass than the 5-species treatment. Although the overall productivities of the 1-, 16-, and 32-species treatments were similar, the relative ranking of the four diversity treatments varied between soil types. Weed biomass was higher in low-diversity treatments than high-diversity treatments. Year-to-year variation in productivity did not differ between treatments. My results show that diverse mixes of native perennial vegetation are as productive as a switchgrass monoculture over a 5-yr period suggesting that they are reliable source of biomass for bioenergy. However, differences in the relative ranking of the four diversity treatments, between soil types suggest that bioenergy seed mixes must be tailored to site characteristics to maximize productivity and stand success