The adaptive geometry of boreal conifers

Accurate and unbiased radiative energy transfer models are critical to our understanding of ecosystem primary productivity, carbon cycling, and climate change. Much of the current research in this area is based on models parameterized for grasslands and broadleaf forests. However, many temperate montane and boreal forests are dominated by conifers, which present unique challenges to modellers. We propose two fundamentally different strategies by which plant canopies optimize solar radiation interception. Laminar canopies (e.g., grasslands, broadleaf trees) are .solar panels. that directly intercept incoming radiant energy. By contrast, conifer canopies are conical anechoic (.without echo.) surfaces that intercept radiant energy by scattering it through the canopy. The properties of anechoic surfaces are well known in acoustical and electrical engineering, but have not been applied in environmental biophysics. We discuss the physical principles of anechoic surfaces, and demonstrate how these principles apply to conifer trees and canopies. A key feature of anechoic interception is low radiance over all wavelengths, which is an emergent property of the system. Using empirical data from boreal forest stands in Riding Mountain National Park (Manitoba, Canada), we demonstrate that conifer canopies have very low near-infrared radiance compared to laminar broadleaf canopies. Vegetation index values for conifers are thereby reduced, resulting in underestimates of primary productivity and other biophysical parameters. We also discuss the adaptive significance of boreal conifer geometry, and consider factors driving selection of laminar versus anechoic canopy architectures

Markovian spatial-inhibition models for established clonal populations

Abstract While a number of experimental studies and models have examined the foraging behaviour of single clonal genets, very few investigations have focussed on the dynamics of ramet recruitment in established clonal monocultures. This contribution discusses modelling the spatial structure of density-dependent clonal populations using Markovian spatial inhibition rules. Markovian dependence refers to situations where local conditions (interactions with neighbours) determine the outcome of a process. An example is presented in which the Markov spatial-inhibition model is successfully fitted to observed ramet spatial patterns in the clonal herb Aralia nudicaulis L. (wild sarsaparilla)

THE EFFECT OF ROUNDING ON THE PROBABILITY DISTRIBUTION OF REGRADING IN THE U.S. PEANUT INDUSTRY

This article determines the effect of rounding (pointing-off) of grade percentages to the nearest whole number on the probability distribution of regrading in the peanut industry. Results show that rounding causes graders to have to regrade an extra 4% of samples even when they follow all directions and make no mistakes. When rounding was not used, the sample weight had little effect on the probability of regrading. With rounding, the probability of regrading was reduced by beginning with a larger than 500-gram sample. Thus, rounding provides an incentive to take overweight samples in order to avoid regrading. Overweight samples can overestimate the value of peanuts. A low-cost way to improve peanut grading accuracy would be to round to tenths rather than whole numbers.grading, normal-jump distribution, peanuts, regrading, rounding, Crop Production/Industries,

Superparamagnetic magnetization equation in two dimensions

An equation for the dependence of magnetization on magnetic field in the case of two-dimensional (base plane) anisotropy has been derived. The resulting equation is expressed as an infinite series of modified Bessel functions, unlike the elementary function expressions that are applicable to the one-dimensional (axially anisotropic) and three-dimensional (isotropic) cases. Nevertheless, in the low-field limit, the series can be effectively truncated to give an approximate solution, while, in the high-field limit, an alternative expression has been derived which represents the limiting function as the field strength tends to infinity. The resulting expressions can be used to describe the superparamagnetic magnetization and susceptibility as a function of magnetic field in situations where the magnetic moments are constrained to lie in a plane, with no preferred direction within the plane. This can therefore be applied to two-dimensional structures, such as magnetic thin films, where magnetostatic energy confines the moments to the plane of the film, or to three-dimensional structures with planar magnetocrystalline anisotropy

Impact of revised Section 199A on grain producers

The Oklahoma Cooperative Extension Service periodically issues revisions to its publications. The most current edition is made available. For access to an earlier edition, if available for this title, please contact the Oklahoma State University Library Archives by email at [email protected] or by phone at 405-744-6311

A method for achieving reciprocity of funding in community-based participatory research

BACKGROUND: The St. Louis Komen Project was conceived to address disparities in breast cancer treatment and outcomes between African-American and White women in St. Louis, Missouri. Our goal was to apportion tasks and funding through a process to which all researcher partners had input and to which all could agree, thus eliminating institutionalized inequalities. METHODS: This paper describes the collaborative process and resulting division of responsibilities, determination of costs, and ultimate allocation of funds and resources, as well as the documentation employed to achieve funding reciprocity and equal accountability. RESULTS: Both communication and documentation are critical. Although the Memoranda of Understanding employed are not a panacea, they codify roles and expectations and promote trust. The process of developing financial transparency set the tone for subsequent steps in the research process. CONCLUSIONS: The exhaustive planning process and project-specific procedures developed by its partners have helped the project foster reciprocity, facilitate participation, and equitably distribute resources

Increasing plant diversity does not influence productivity: empirical evidence and potential mechanisms

The relationship between species diversity and ecosystem functions has generated considerable debate among ecologists. Ecosystem functions (e.g. productivity, nutrient retention) are often positively correlated with species richness in experimental plant assemblages, but little or no correlation exists in natural communities.We examined the effects of species richness on productivity and available soil nitrate by experimentally manipulating richness using random draws from a pool of ten perennial grasses. Species richness had no significant effect on aboveground productivity or soil nitrate availability, suggesting that functional diversity may be more important than species richness in determining ecosystem functions. The relationship between diversity and ecosystem functions may also depend on resource limitation. A positive relationship is expected when below-ground resources are limiting, but the relationship is expected to weaken when below-ground resource supply rates are higher and competition for light becomes more important. Further experiments are required to determine the mechanisms underlying diversity-productivity relationships