Search

Perennial grasses and corn stalks can supply abundant lignocellulosic feedstock in the northern Great Plains of the U.S. There is a need to understand the mechanical properties of these crops for better handling and processing of biomass feedstocks in bioprocessing industries. The objectives of this research included determination of tensile and shear stresses of big bluestem, corn stalk, intermediate wheatgrass, and switchgrass stems and measurement of specific tensile and shear energies during tensile and shear failure. A high-capacity MTI-100K universal testing machine equipped with adapted tensile clamps and a specially designed and fabricated double-shear device were used for tensile and shear testing. Ultimate shear stresses were not statistically different for big bluestem, corn stalk, and intermediate wheatgrass, with values of 7.33, 8.53 and 6.23 MPa, respectively, which were less than switchgrass at 13.39 MPa (p < 0.05). Corn stalk had the greatest ultimate tensile stress of 69.30 MPa, followed by switchgrass, big bluestem, and intermediate wheatgrass. The ultimate tensile stress and shear stress were statistically different (p < 0.05) from each other for all four feedstocks. Both ultimate shear energy and specific shear energy for corn stalk were statistically different (p < 0.05) from big bluestem, intermediate wheatgrass, and switchgrass. The evaluated shear to tensile stress ratios, expressed as percentages, were 29.3%, 12.3%, 30.5%, and 31.9%, whereas the shear to tensile energy ratios were greater, with values of 42.2%, 67.2%, 61.2%, 50.4% for big bluestem, corn stalk, intermediate wheatgrass, and switchgrass, respectively. Based on these results, shear-dominant size-reduction devices (e.g., knife mills and chippers) should be more energy efficient, and this energy efficiency should be taken advantage of when designing size-reduction devices. Further research efforts are necessary to determine the effect of moisture, crop variety, and maturity stage, as these factors are known to affect the mechanical characteristics of biomass feedstocks. [ABSTRACT FROM AUTHOR]

Decomposition is a critical process that links the above- and below-ground portions of the nutrient cycle. A study was initiated in North Dakota, USA, to evaluate the decomposition rate between three genetically improved grass species monocultures, Agropyron desertorum, Bromus inermis, and Pascopyrum smithii, and two native perennial grass species occurring in area rangelands, Nassella viridula and Bouteloua gracilis. Standing litter of all five species was harvested in October 1996 and placed into litterbags. Litterbags were placed along transects in early November 1996 and randomly selected bags were sampled in June, July, August, September, and October, 1997. Carbon (C), nitrogen (N) and lignin were determined on all samples including the initial litter samples. The percent of dry matter decomposed across time ranged from 18.4% for B. gracilis to 26.8% for A. desertorum. The two native species, occurring in undisturbed rangeland, had significantly lower rates of decomposition than did the monocultures of the improved cultivars, including the monoculture of the improved native, P. smithii. Most decomposition occurred prior to the June 1997 sampling date, and from June to October 1997 decomposition was approximately the same for all species (7 to 8% ). The N concentration of the initial samples had the strongest correlation (r = 0.78 P < 0.01) with decomposition rates. Lignin had a significant positive correlation (r = 0.49, P = 0.03) and the C:N ratio had a significant negative correlation (r = -0.67 P < 0.01) with decomposition. Traits, such as decomposition, that can affect ecosystem functioning need to be given greater emphasis in genetic selection of native and improved grass species. [ABSTRACT FROM AUTHOR]

Presents a study which compared the properties of soils from an ungrazed and a heavily grazed vegetation pasture in the Northern Great Plains, United States. Functions of soils in the ecosystem; Examination of the effect of soil management practices on soil properties; Methodology; Results and discussion.

Native plant biodiversity loss and exotic species invasions are threatening the ability of many ecosystems to maintain key functions and processes. We currently lack detailed plant biodiversity data at a national scale with which to make management decisions and recommendations based on current conservation challenges. We collected plant biodiversity and exotic species richness data from 4 sites in the Northern Great Plains using the modified Whittaker (MW) and Natural Resources Inventory (NRI) methods to evaluate any major differences between indicators generated from these methods and offer recommendations based on findings. Our data indicated that the NRI protocols underestimated both total plant species richness and exotic species richness compared with the MW approach. More importantly, however, results show that biodiversity indicators from the two methods showed similar trends. Increasing time spent on making species richness measurements and implementing a more systematic approach to detecting species within a plot could improve biodiversity inventory and monitoring efforts in NRI while also providing a link between existing long-term data and any new information collected. These adjustments would ultimately help those interested in adopting NRI methods and using plant biodiversity data to increase the amount and quality of information collected. [ABSTRACT FROM AUTHOR]