Biofuels A gronomy J our n al • Volu me 102 , I s sue 2 • 2 010 675 ABSTRACT Th e expected profi tability of six cellulosic feedstock crops is compared with two corn (Zea mays L.)-based systems under southern Great Lakes region conditions over a projected 10-yr period. At 2006-2009 costs and yields from literature, none would be more profi table than the corn-based systems. Comparative breakeven price analysis identifi es the cellulosic feedstock price that would make crops equally profi table with continuous corn. Breakeven prices of cellulose are $110 to $130 Mg -1 for poplar (Populus spp.), switchgrass (Panicum virgatum L.), and mixed grasses. For miscanthus (Miscanthus × giganteus J.M. Greef & Deuter ex Hodk. & Renvoize), breakeven cellulose prices are $200 Mg -1 at current costs, but only $45 Mg -1 if rhizome costs fall to near European levels, well within the range of temporary U.S. farm bill cost share levels for biomass harvest, transportation, and storage. Without targeted subsidies, native prairie and fallow old fi eld systems would not be competitive with corn or the other four cellulosic crops reviewed at current yields and foreseeable prices.Comparative breakeven yields at a cellulose price of $60 Mg -1 would require yield gains above benchmark literature values of 50% for switchgrass, 60% for poplar and mixed grasses, 140% for fallow old fi elds, 180% for native prairie, and 190% for miscanthus at current rhizome costs, but no added yield for miscanthus with rhizomes at plausible reduced cost.
Semi-natural habitats are integral to most agricultural areas and have the potential to support ecosystem services, especially biological control and pollination by supplying resources for the invertebrates providing these services and for soil conservation by preventing erosion and runoff. Some habitats are supported through agri-environment scheme funding in the European Union, but their value for ecosystem service delivery has been questioned. An improved understanding of previous research approaches and outcomes will contribute to the development of more sustainable farming systems, improve experimental designs and highlight knowledge gaps especially for funders and researchers. Here we compiled a systematic map to allow for the first time a review of the quantity of evidence collected in Europe that semi-natural habitats support biological control, pollination and soil conservation. A literature search selected 2252 publications, and, following review, 270 met the inclusion criteria and were entered into the database. Most publications were of pest control (143 publications) with less on pollination (78 publications) or soil-related aspects (31). For pest control and pollination, most publications reported a positive effect of semi-natural habitats. There were weaknesses in the evidence base though because of bias in study location and the crops, whilst metrics (e.g. yield) valued by end users were seldom measured. Hedgerows, woodland and grassland were the most heavily investigated semi-natural habitats, and the wider landscape composition was often considered. Study designs varied considerably yet only 24% included controls or involved manipulation of semi-natural habitats. Service providers were commonly measured and used as a surrogate for ecosystem service delivery. Key messages for policymakers and funders are that they should encourage research that includes more metrics required by end users, be prepared to fund longer-term studies (61% were of only 1-year duration) and investigate the role of soils within semi-natural habitats in delivering ecosystem services.
We report the discovery that Bombus terrestris audax (Buff-tailed bumblebee) locomotor trajectories adhere to a speed-curvature power law relationship which has previously been found in humans, non-human primates and Drosophila larval trajectories. No previous study has reported such a finding in adult insect locomotion. We used behavioural tracking to study walking Bombus terrestris in an arena under different training environments. Trajectories analysed from this tracking show the speed-curvature power law holds robustly at the population level, displaying an exponent close to two-thirds. This exponent corroborates previous findings in human movement patterns, but differs from the three-quarter exponent reported for Drosophila larval locomotion. There are conflicting hypotheses for the principal origin of these speed-curvature laws, ranging from the role of central planning to kinematic and muscular skeletal constraints. Our findings substantiate the latter idea that dynamic power-law effects are robust, differing only through kinematic constraints due to locomotive method. Our research supports the notion that these laws are present in a greater range of species than previously thought, even in the bumblebee. Such power laws may provide optimal behavioural templates for organisms, delivering a potential analytical tool to study deviations from this template. Our results suggest that curvature and angular speed are constrained geometrically, and independently of the muscles and nerves of the performing body.
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