Root biomass and carbon storage in differently managed multispecies temporary grasslands

Species-rich grasslands may potentially increase carbon (C) storage in soil and an experiment was established to investigate C storage in highly productive temporary multi-species grasslands. Plots were established with three mixtures: 1) a herb mixture containing salad burnet (Sanguisorba minor L.), fenugreek (Trogonella foenum-gruecum), chicory (Chicorium intybus L.), caraway (Carum carvi L.), birdsfoot trefoil (Lotus corniculatus L.), chervil (Anthriscus cerefolium L.), plantain (Plantago lanceolata L.), lucerne (Medicago sativa L.) and melilot (Melilotus officinalis), 2) 50% of the herb mixture and 50% of a white clover (Trifolium repens L.)/perennial ryegrass (Lolium perenne L.) mixture, and 3) 5% of the herb mixture and 95% of the white clover/ryegrass mixture. Management factors were number of cuts per year and fertilizer application. Aboveground biomass increased considerably with increasing content of herbs and with fertilizer application in plots with a 4-cut strategy. With a 6-cut strategy without fertilizer herbs had no effect on the aboveground biomass. In the herb mixture biomass of small roots was lower than in mixtures with white clover and ryegrass. There was a tendency towards increased biomass in the large root fraction with increasing herb content. The experiment indicated increased CO2 evolution following cultivation of multispecies grasslands

Management of forb species mixtures for high biomass production

Including forb species in grassland mixtures may secure a more biodiversity-friendly production of biomass. This experiment showed interesting future perspectives in terms of production of low-cost biomass for e.g. biogas production, which can be obtained by reducing the number of cuttings without compromising yield levels. No significant differences in dry matter (DM) yields of chicory, birdsfoot trefoil, yarrow and a 13 species mixture were observed between the situations with four compared to one autumn cut per year. Especially the 13 species mixture showed great potential in terms of yield and suppression of unsown species, for which reasons it should be developed further through knowledge on the species in pure stands

Effect of seed mixture composition and management on competitiveness of herbs in temporary grasslands

In multispecies grasslands the proportion of different herb species may vary considerably due to low competitiveness of some herbs. To examine the possibility for increasing the competitiveness an experiment with three factors were set up: 1) amount of herb seed in a perennial ryegrass (Lolium perenne), white clover (Trifolium repens) mixture, 2) slurry application and 3) cutting frequency. The experiment was carried out over two years. The herbs mix contained salad burnet (Sanguisorba minor), fenugreek (Trogonella foenum-gruecum), chicory (Chicorium intybus), caraway (Carum carvi), birdsfoot trefoil (Lotus corniculatus), chervil (Anthriscus cerefolium), plantain (Plantago lanceolata), Lucerne (Medicago sativa) and melilot (Melilotus officinalis). The proportion of herb seeds was 5, 25, 50 or 100 %. The herb species were most competitive in the first harvest year. In the second year the proportion of all herb species were very low in the mixtures, where white clover and perennial ryegrass were represented. The proportion of many herbs were higher at a 7-cut than at a 4-cut management, and application of cattle slurry also affected the competitiveness. In general chicory, caraway and plantain were the strongest competitors, salad burnet and birdsfoot trefoil were intermediate, and melilot, fenugreek and chervil were very weak competitors

Air-core photonic band-gap fibers: the impact of surface modes

We study the dispersion and leakage properties for the recently reported low-loss photonic band-gap fiber by Smith et al. [Nature 424, 657 (2003)]. We find that surface modes have a significant impact on both the dispersion and leakage properties of the fundamental mode. Our dispersion results are in qualitative agreement with the dispersion profile reported recently by Ouzounov et al. [Science 301, 1702 (2003)] though our results suggest that the observed long-wavelength anomalous dispersion is due to an avoided crossing (with surface modes) rather than band-bending caused by the photonic band-gap boundary of the cladding.Comment: 7 pages including 4 figures. Accepted for Optics Expres

Modal cut-off and the V-parameter in photonic crystal fibers

We address the long-standing unresolved problem concerning the V-parameter in a photonic crystal fiber (PCF). Formulate the parameter appropriate for a core-defect in a periodic structure we argue that the multi-mode cut-off occurs at a wavelength lambda* which satisfies V_PCF(lambda*)=pi. Comparing to numerics and recent cut-off calculations we confirm this result.Comment: 3 pages including 2 figures. Accepted for Optics Letter

Graphene on metals: a Van der Waals density functional study

We use density functional theory (DFT) with a recently developed van der Waals density functional (vdW-DF) to study the adsorption of graphene on Al, Cu, Ag, Au, Pt, Pd, Co and Ni(111) surfaces. In constrast to the local density approximation (LDA) which predicts relatively strong binding for Ni,Co and Pd, the vdW-DF predicts weak binding for all metals and metal-graphene distances in the range 3.40-3.72 \AA. At these distances the graphene bandstructure as calculated with DFT and the many-body G$_0$W$_0$ method is basically unaffected by the substrate, in particular there is no opening of a band gap at the $K$-point.Comment: 4 pages, 3 figure

Use of rhizobacteria as biological control agents of downy brome

Non-Peer Reviewe

Economic Effects of the 1988 Drought in North Dakota: A 1989 Update of the Financial Conditions of Farm and Ranch Operators

Agricultural Finance, Farm Management, Resource /Energy Economics and Policy,

Outlook of North Dakota Farm Households: Results of the 1988 Longitudinal Farm Survey

Agricultural Finance, Farm Management,

Photonic crystal resonator integrated in a microfluidic system

We report on a novel optofluidic system consisting of a silica-based 1D photonic crystal, integrated planar waveguides and electrically insulated fluidic channels. An array of pillars in a microfluidic channel designed for electrochromatography is used as a resonator for on-column label-free refractive index detection. The resonator was fabricated in a silicon oxynitride platform, to support electroosmotic flow, and operated at 1.55 microns. Different aqueous solutions of ethanol with refractive indices ranging from n = 1.3330 to 1.3616 were pumped into the column/resonator and the transmission spectra were recorded. Linear shifts of the resonant wavelengths yielded a maximum sensitivity of 480 nm/RIU and a minimum difference of 0.007 RIU was measured