In 1969, a cooperative progeny test of Douglas-fir, Pseudotsuqa menzies-ii (Mirb.) Franco, was initiated to evaluate the growth performance of progeny from selected plus trees. Using height data measured in 19 75, it is shown that the mean height of plus tree progeny is significantly greater than the mean height of the control progeny. Much of this gain may, however, be due to the heterotic effect of crossing parents from allopatric populations. The breeding value of individual plus trees showed a wide range of variation. This range was markedly reduced when the few extreme plus tree parents were excluded. An investigation of possible geographic trends showed that in only one instance did the progeny of parents of similar origin perform comparably. It is therefore concluded that, over the range of plus tree selection, geographic origin is; of little, importance in determining breeding value. Initial juvenile-mature data demonstrated that nursery height in 1969 and 1970 was significantly correlated with plantation height in 1975. As expected, 1973 and 1974 plantation heights were highly correlated with 1975 height. An attempt to predict genotype x environment interactions from the latitudinal and longitudinal displacement of the progeny from their plus tree parents proved unsuccessful. Other variables must therefore be considered before: progeny performance at a specific location can be successfully predicted. / Forestry, Faculty of / Graduate

The forest water balance and root water relations were studied in a thinned (840 stems/ha) and an unthinned (1840 stems/ha) stand of a Douglas fir forest during two consecutive summers. Soil water content and potential data were used to compute water extraction rates and patterns for the root zone in each stand over a four-week drying period. The results showed a gradual downward shift of the zone of maximum root water uptake as the soil dried. There was good correlation between water uptake rate and root density. Water flux into the bottom of the root zone, estimated by the use of Darcy's Law, increased from 8 to 15% of the evapotranspiration at the thinned site and from 2 to 8% at the unthinned site. Soil profile water depletion, corrected for flux out of or into the bottom of the root zone, agreed well with evapotranspiration computed from micrometeorological energy balance data. Water withdrawal from trunk storage accounted for only 2% of the total evapotranspiration over the four-week drying period. In the first two weeks, evapotranspiration from the thinned stand was 11% less than that from the unthinned stand, but was 18% more in the last two weeks. At a particular soil water potential, individual trees at the thinned site transpired an average of 25% more than those at the unthinned site on fine sunny days. When water uptake was compared over the four-week period, it was found that the individual trees at the thinned site were transpiring 35% more than those at the Unthinned site. Measurements of soil and root xylem water potentials were made using a Wescor HR-33T dew point microvoltmeter and PT 51-10 hygrometers. Tensio-meters were used to measure soil water potentials at values greater than -1 bar. Twig water potential was measured by the pressure chamber technique. Root water potential measurement required tangential insertion of the hygrometer into the root xylem and sensor protection from plant resins using gypsum powder. Soil water potentials measured with hygrometers were compared with potentials computed using gravimetric soil water content measurements and laboratory soil water retention data, while root water potential measurements were compared with those made on roots with the pressure chamber. The comparisons showed good agreement to within 0.3 bar over an 8-bar range. Soil water matric potential on both dew point and psychrometric modes showed good agreement. Soil and root resistances to water uptake were studied in both stands. Resistances were obtained from water potential differences and evapotranspiration fluxes. Root xylem water potential, like twig water potential, showed a definite diurnal trend. Soil water potential approached the root water potential as the soil dried. Soil resistance remained very small in comparison to root resistance even at a soil water potential of -11 bars; however, it was found that "contact resistance" could account for as much as half of the total soil to root xylem resistance. Root resistance varied during the daytime becoming increasingly.important toward nightfall. The plot of rate of water uptake versus soil to root xylem potential difference showed a linear relationship extending through zero. Root resistance remained relatively constant as the soil dried. / Land and Food Systems, Faculty of / Graduate

Thesis (Ph. D.)--University of Washington, 2008. / Vita. Includes bibliographical references (leaves 168-178).

Thesis (Ph. D.)--Oregon State University, 1991. / Typescript (photocopy). Includes bibliographical references (leaves 115-123). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 1993. / Typescript (photography). Includes bibliographical references (leaves 123-144). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 77-88). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references. Also available on the World Wide Web.

Thesis (Ph. D.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 239-279). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 1988. / Typescript (photocopy). Includes bibliographical references (leaves 69-74). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 1993. / Typescript (photocopy). Includes bibliographical references (leaves 37-42). Also available on the World Wide Web.