Jacob N. Barney

Sustainable Biofuels Redux

Science-based policy is essential for guiding an environmentally sustainable approach to cellulosic biofuels.

Nonnative Species and Bioenergy: Are We Cultivating the Next Invader?

ABSTRACT Biofuel feedstocks are being selected, bred, and engineered from nonnative taxa to have few resident pests, to tolerate poor growing conditions, and to produce highly competitive monospecific stands—traits that typify much of our invasive flora. We used a weed risk-assessment protocol, which categorizes the risk of becoming invasive on the basis of biogeography, history, biology, and ecology, to qualify the potential invasiveness of three leading biofuel candidate crops—switchgrass, giant reed, and miscanthus (a sterile hybrid)—under various assumptions. Switchgrass was found to have a high invasive potential in California, unless sterility is introduced; giant reed has a high invasive potential in Florida, where large plantations are proposed; miscanthus poses little threat of escape in the United States. Each biofuel crop shares many characteristics with established invasive weeds with a similar life history. We propose genotype-specific preintroduction screening for a target region, which consists of risk analysis, climate-matching modeling, and ecological studies of fitness responses to various environmental scenarios. This screening procedure will provide reasonable assurance that economically beneficial biofuel crops will pose a minimal risk of damaging native and managed environs.

ISOLATION AND CHARACTERIZATION OF ALLELOPATHIC VOLATILES FROM MUGWORT (Artemisia vulgaris)

Several volatile allelochemicals were identified and characterized from fresh leaf tissue of three distinct populations of the invasive perennial weed, mugwort (Artemisia vulgaris). A unique bioassay was used to demonstrate the release of volatile allelochemicals from leaf tissues. Leaf volatiles were trapped and analyzed via gas chromatography coupled with mass spectrometry. Some of the components identified were terpenes, including camphor, eucalyptol, α-pinene, and β-pinene. Those commercially available were tested individually to determine their phytotoxicity. Concentrations of detectable volatiles differed in both absolute and relative proportions among the mugwort populations. The three mugwort populations consisted of a taller, highly branched population (ITH-1); a shorter, lesser-branched population (ITH-2) (both grown from rhizome fragments from managed landscapes); and a population grown from seed with lobed leaves (VT). Considerable interspecific variation existed in leaf morphology and leaf surface chemistry. Bioassays revealed that none of the individual monoterpenes could account for the observed phytotoxicity imparted by total leaf volatiles, suggesting a synergistic effect or activity of a component not tested. Despite inability to detect a single dominant phytotoxic compound, decreases in total terpene concentration with increase in leaf age correlated with decreases in phytotoxicity. The presence of bioactive terpenoids in leaf surface chemistry of younger mugwort tissue suggests a potential role for terpenoids in mugwort establishment and proliferation in introduced habitats.

A unifying framework for biological invasions: the state factor model

Biological invasions are a fixture in our landscapes, with consequent losses in endemic biota and shifts in ecosystem function. Despite the historical recognition of exotic species success in novel environs, this phenomenon lacks a holistic-descriptive framework. Recent attempts to explain biological invasions are based largely on identifying the inherent invasive qualities of successful exotic species (i.e., invasiveness), or characterizing the susceptibility of a habitat to an introduced species (i.e., invasibility), with few studies examining their interaction or additional contributing factors (e.g., time since introduction). We propose unifying the ’points of entry’ into biological invasions with a state factor model that incorporates all contributing variables—not just species or habitats—into a quantifiable, factorial model amenable to hypothesis testing. State factors are phenomenological variables describing the state of a system—historically used in soil and vegetation science. Our state factor equation relates any quantifiable property of an invasion (i) as a function of propagule pressure (p), introduced habitat (h), invader autecology (a), source environment (s), and time since introduction (t). By manipulating state factors singly, or in interaction, targeted variation can be related to quantifiable properties of exotic species while controlling, or at minimum accounting for, remaining factors contributing variation to the system. This holistic factor-function paradigm extends research on invasions from beyond the limits imposed by current theory, fosters novel empirical approaches, elucidates knowledge gaps in our understanding of resident invasions, and allows for variable accounting via a factor matrix. Here we briefly outline the ontogeny of state factors in soil and vegetation science, detail our proposed ’phast’ framework for biological invasions, including notation, and examine a case study in state factor utility.

A Review of the Biology and Ecology of Three Invasive Perennials in New York State: Japanese Knotweed (Polygonum cuspidatum), Mugwort (Artemisia vulgaris) and Pale Swallow-wort (Vincetoxicum rossicum)

Terrestrial weeds continue to evolve in association with the rapid global changes in our land-use systems, due to their regenerative strategies, their adaptability to change, and their inherent diversity. Currently, invasive weeds are estimated to cost the United States’ economy up to

Global Climate Niche Estimates for Bioenergy Crops and Invasive Species of Agronomic Origin: Potential Problems and Opportunities

35 billion per year, and this total is rapidly increasing, as greater numbers of invasive species become naturalized. Several invasive exotic species have more recently established across New York State, creating difficulties for agricultural producers, roadside and natural areas managers, and homeowners and resulting in millions of dollars expended annually for their control. Three perennials that have become particularly problematic in New York State in recent years in both agricultural and roadside settings include Japanese knotweed (Polygonum cuspidatum Sieb. & Zucc.), mugwort (Artemisia vulgaris L.), and pale swallow-wort (Vincetoxicum rossicum (Kleop.) Barbar.). This review describes their history, biology, ecology, and potential for management and focuses on key characteristics contributing to their spread in New York State and adjacent regions.

The Biology of Invasive Alien Plants in Canada. 5. Polygonum cuspidatum Sieb. & Zucc. (= Fallopia japonica (Houtt.) Ronse Decr.)

The global push towards a more biomass-based energy sector is ramping up efforts to adopt regionally appropriate high-yielding crops. As potential bioenergy crops are being moved around the world an assessment of the climatic suitability would be a prudent first step in identifying suitable areas of productivity and risk. Additionally, this assessment also provides a necessary step in evaluating the invasive potential of bioenergy crops, which present a possible negative externality to the bioeconomy. Therefore, we provide the first global climate niche assessment for the major graminaceous (9), herbaceous (3), and woody (4) bioenergy crops. Additionally, we contrast these with climate niche assessments for North American invasive species that were originally introduced for agronomic purposes as examples of well-intentioned introductions gone awry. With few exceptions (e.g., Saccharum officinarum, Pennisetum purpureum), the bioenergy crops exhibit broad climatic tolerance, which allows tremendous flexibility in choosing crops, especially in areas with high summer rainfall and long growing seasons (e.g., southeastern US, Amazon Basin, eastern Australia). Unsurprisingly, the invasive species of agronomic origin have very similar global climate niche profiles as the proposed bioenergy crops, also demonstrating broad climatic tolerance. The ecoregional evaluation of bioenergy crops and known invasive species demonstrates tremendous overlap at both high (EI≥30) and moderate (EI≥20) climate suitability. The southern and western US ecoregions support the greatest number of invasive species of agronomic origin, especially the Southeastern USA Plains, Mixed Woods Plains, and Mediterranean California. Many regions of the world have a suitable climate for several bioenergy crops allowing selection of agro-ecoregionally appropriate crops. This model knowingly ignores the complex biotic interactions and edaphic conditions, but provides a robust assessment of the climate niche, which is valuable for agronomists, crop developers, and regulators seeking to choose agro-ecoregionally appropriate crops while minimizing the risk of invasive species.

What is the “real” impact of invasive plant species?

Polygonum cuspidatum (Japanese knotweed) is an introduced perennial geophyte in the buckwheat family (Polygonaceae). The phytogeographic distribution of P. cuspidatum in North America suggests a large number of intentional introductions via ornamental plantings from 1870 to 2000, followed by secondary spread from these foci. This species is most pernicious along riparian corridors and road and railroad rights-of-way, reducing visibility, displacing native species, negatively affecting native wildlife, and causing alterations in natural hydrologic processes. Although non-hybrid seed recruitment has not been observed in Europe because of the presence of male-sterile clones only, dispersal of seeds and stem and rhizome fragments by flowing water does occur in North America and populations are readily established from these sources. The primary means of local and regional range expansion is human-mediated transport of rhizome-infested soil. Hybridization is common with the congener P. sachalinense in the intr...

New pasture plants intensify invasive species risk.

Invasive plant species should be evaluated and prioritized for management according to their impacts, which include reduction in native diversity, changes to nutrient pools, and alteration of fire regimes. However, the impacts of most invasive species have not been quantified and, when measured, those impacts are based on a limited number of response metrics. As a result, invasion ecology has been overwhelmed by speculation and bias regarding the ecological consequences of invasive plants. We propose a quantitative mathematical framework that integrates any number of impact metrics as a function of groundcover and geographic extent. By making relative comparisons between invaded and uninvaded landscapes at the population scale, which results in a percent change for each metric, we overcome previous limitations that confounded the integration of metrics based on different units. Our model offers a quantitative approach to ecological impact that may allow identification of the transition from benign introdu...

Miscanthus × giganteus and Arundo donax shoot and rhizome tolerance of extreme moisture stress.

Significance Governments spend billions of dollars each year managing invasive plant species. Many invasive plants have escaped from pastures and now degrade natural areas and transform ecosystems. New pasture taxa are promoted to help achieve sustainable intensification of agriculture by increasing production without using more land. However, plant characteristics that increase production also increase invasion risk. Combined with inadequate regulation and management to establish large feed-plant populations, new taxa will likely exacerbate problems with invasive species. Livestock production accounts for 30% of the worlds land area. Risks associated with invasive feed-plants have been largely overlooked, even by studies explicitly critiquing the environmental risks of sustainable intensification. We suggest a suite of protocols to reduce these risks in sustainable intensification of agriculture. Agricultural intensification is critical to meet global food demand, but intensification threatens native species and degrades ecosystems. Sustainable intensification (SI) is heralded as a new approach for enabling growth in agriculture while minimizing environmental impacts. However, the SI literature has overlooked a major environmental risk. Using data from eight countries on six continents, we show that few governments regulate conventionally bred pasture taxa to limit threats to natural areas, even though most agribusinesses promote taxa with substantial weed risk. New pasture taxa (including species, subspecies, varieties, cultivars, and plant-endophyte combinations) are bred with characteristics typical of invasive species and environmental weeds. By introducing novel genetic and endophyte variation, pasture taxa are imbued with additional capacity for invasion and environmental impact. New strategies to prevent future problems are urgently needed. We highlight opportunities for researchers, agribusiness, and consumers to reduce environmental risks associated with new pasture taxa. We also emphasize four main approaches that governments could consider as they build new policies to limit weed risks, including (i) national lists of taxa that are prohibited based on environmental risk; (ii) a weed risk assessment for all new taxa; (iii) a program to rapidly detect and control new taxa that invade natural areas; and (iv) the polluter-pays principle, so that if a taxon becomes an environmental weed, industry pays for its management. There is mounting pressure to increase livestock production. With foresight and planning, growth in agriculture can be achieved sustainably provided that the scope of SI expands to encompass environmental weed risks.