Validation of a Technique for Estimating Alfalfa (Medicago sativa) Biomass from Canopy Volume

Determining biomass production of individual alfalfa (Medicago sativa L.) plants in space planted evaluation studies is generally not feasible. Clipping plants is time consuming, expensive, and often not possible if the plants are subjected to grazing. A regression function (Bʹ = 0.72558 + 0.11638 × Vʹ) was developed from spaced plants growing on rangeland in northwestern South Dakota near Buffalo to nondestructively estimate individual plant biomass (B) from canopy volume (V). However, external validation is necessary to effectively apply the model to other environments. In the summer of 2015, new data to validate the model were collected from spaced plants near Brookings, South Dakota. Canopy volume and clipped plant biomass were obtained from ten alfalfa populations varying in genetic background, growth habit, and growth stage. Fitted models for the model-building and validation data sets had similar estimated regression coefficients and attributes. Mean squared prediction errors (MSPR) were similar to or smaller than error mean square (MSE) of the model-building regression model, indicating reasonable predictive ability. Validation results indicated that the model reliably estimated biomass of plants in another environment. However, the technique should not be utilized where individual plants are not easily distinguished, such as alfalfa monocultures. Estimating biomass from canopy volume values that are extrapolations (\u3e2.077 × 106 cm3) of the model-building data set is not recommended

The Role of Student Attitudes and Beliefs About Mathematics and Science Learning in Academic Achievement: Evidence From TIMSS for Six Nations

In view of the prevalent belief among parents, educators, and policy makers that positive student attitudes and beliefs about mathematics learning are associated with higher academic achievement, Turner and Boe (1999) recently examined this association using data from the Third International Mathematics and Science Study (TIMSS) for seventh- and eighth-grade students in the United States. In light of the substantial support found by Turner and Boe for such attitude-achievement relationships under statistically controlled conditions, the research reported here was designed to expand upon the prior study by quantifying the strength of these relationships in both mathematics and science and to extend the analysis to other nations. To examine cross-national similarities and differences in attitude-achievement relationships, Singapore, Korea, and Hong Kong (representing the Peoples\u27 Republic of China 1) were selected from the East, and Switzer­land, Germany, and the United States were selected from the West