Doreen L. Griffin

An examination of the genetic control of Douglas-fir vascular tissue phytochemicals: Implications for black bear foraging

Silvicultural practices can influence black bear (Ursus americanus) foraging preferences for Douglas-fir (Pseudotsuga menziesii) cambial-zone vascular tissues, but little is known about the role of genetics. To study the impact of genetic selection, vascular tissue samples were collected from Douglas-fir trees in six half-sib families from five different sites in north central Oregon. Four replications of three-tree non-contiguous plots were sampled at each site to examine inter- and intra-site variation. Tree growth was measured as tree diameter at breast height and the absolute concentrations of 26 different terpenoids were determined by gas chromatography/flame ionization detection from ethyl acetate extracts. The simple carbohydrates fructose, glucose, and sucrose, and the phenolic glycoside coniferin were quantified using anion-exchange chromatography with pulsed amperometric detection. Cluster analysis was used to reduce the number of variables used in analyses of variance. Results for the families studied here indicate that tree growth and some terpenoids were under some level of genetic control. Furthermore, allocation of constitutive terpenoids in vascular tissues was not at the expense of tree growth. The sugars present in vascular tissue were affected by environment (site) and genetics (family) and their interaction.

Silvicultural Attempts to Induce Browse Resistance in Conifer Seedlings

A multiyear study was conducted to determine if soil amendment combined with topical application of elemental sulfur could be employed to reduce deer browse damage to four conifer species. Fertilizer and sulfur were applied to conifer seedlings at seven sites near Corvallis, OR. Growth and browse damage data were collected for all seedlings over a period of 17 months. Additionally, foliar concentrations of monoterpenes and simple carbohydrates were assessed in western redcedar (Thuja plicata) seedlings over a period of three years. Fertilization and sulfur treatments had a moderate impact on growth and no influence on browse damage or the chemical responses. Over the course of the study, browse damage diminished while foliar monoterpene concentrations increased in redcedar. It appears that silvicultural manipulation via sulfur application and/or soil amendment cannot accelerate or alter the ontogenetical changes that may naturally defend seedlings against mammalian herbivores. In a brief trial with captive deer, redcedar browse resistance was influenced by seedling maturation, but not monoterpene content. Other maturation effects may yield significant browse protection to young seedlings.

Analysis of commercially available zinc phosphide from Bangladesh — Implications for rodent control

Abstract Farmers in Bangladesh seem reluctant to purchase zinc phosphide (Zn 3 P 2 ) for use in rodent control, primarily because of a concern over the quality of the technical powder available from local distributors. During 1988, packets of Zn 3 P 2 were purchased from the shelves of 23 distributors in Bangladesh and analyzed for technical purity. Only 2 of 23 distributors sold Zn 3 P 2 containing at least 80% (a.i.), while 14 distributors sold material ranging from 15% to nondetectable. Such a lack of quality control is not acceptable if farmers in Bangladesh are to use this material as a primary method of rodent control in agriculture.