Pseudotsuga Menziesii Seedlings Research Articles

The effects of volcanic ash influenced soils and nitrogen fertilization on douglas‐fir seedlings

Abstract An experiment was conducted to help understand the contributions of different soil layers to soil fertility, plant growth, and response to fertilization. Douglas‐fir (Pseudotsuga menziesii) seedlings were used in a pot bioassay to delimit the effects of volcanic ash soils, urea fertilization at 100 and 200 ppm, and the technique of using undisturbed soil as a growth medium. Volcanic ash horizons contained more available phosphorus and mineralized more nitrogen than underlying horizons. Best seedling growth occurred in ash horizons fertilized with 200 ppm of urea‐N. Fertilization decreased soil pH, mycorrhizae formation and foliar‐P levels but increased foliar‐N. The technique of using undisturbed soil had little effect on seedling growth in the weak structured ash horizons but did decrease root weights in the moderate structured sub‐ash layers.

Growth and cold hardiness of container-grown Douglas-fir, noble fir, and Sitka spruce seedlings in simulated greenhouse regimes

Seedlings of Pseudotsugamenziesii (Mirb.) Franco, Abiesprocera Rehd., and Piceasitchensis (Bong.) Carr. were grown for 5 months in growth rooms which simulated hot, warm, or cool growing regimes in greenhouses in western Oregon. Temperature, humidity, light intensity, and photoperiod were changed diurnally and seasonally. In all three species, maximum heights of seedlings were attained in the hot regime, whereas stem diameters were similar under the hot and warm regimes. Dry weight increment was greatest in the warm regime. The cool regime was suboptimal for all aspects of growth. Seedlings grown in the hot regime were least resistant to cold in early fall. Differences in resistance to cold of seedlings grown in the warm and cool regimes varied by species and type of damage.

Resistance to water uptake by Douglas-fir seedlings in soils of different texture

Seedlings of Pseudotsugamenziesii (Mirb.) Franco were grown in fertilized silty clay, silt loam, and loamy sand in a growth chamber. Needle water potentials hardly changed as soil water potential, ψs, dropped to about −2.5 MPa. At ψs = −0.6 MPa, the effect of soil texture on water uptake rate was statistically significant (p = 0.01). Calculated water uptake resistance (from soil to foliage), R, was hardly affected by ψs between −0.5 and −1.0 MPa, but nearly doubled as ψs fell from −1.0 to −2.2 MPa. Plant water resistance is inferred to change relatively little over this range. Upper limits of soil resistance at ψs > −2.5 MPa, estimated (by Gardner's equation) for silt loam and silty clay, are too low to make a large contribution to R, or to the change in R with ψs, or to the large differences in average R among different textures at ψs values from −0.5 to −2.2 MPa. It is inferred that contact resistance, Rc, is large, varies significantly with ψs, and may vary with texture. Unsaturated hydraulic conductivity differences theoretically account for a relationship of Rc, with texture, and, together with possible root shrinkage, could account for a relationship of Rc, with ψs. Mycorrhizal development in these fertilized seedlings was too slight to justify consideration of hyphal resistance.

Studies of Moisture Status and Storage Conditions of Spring-Lifted, Mud-Packed Douglas-Fir Seedlings

Two-year-old (2–0) Douglas-fir (Pseudotsugamenziesii) seedlings were lifted in the spring and mud-packed. These seedlings were tested (a) for moisture status during and after mud-packing or (b) for the effects of various storage conditions.Moisture status measurements indicated that the mud-packing process placed a reversible moisture stress on the seedlings. When the seedlings were planted, however, the mud-packed seedlings displayed a higher moisture stress than bare-root or unlifted seedlings. There was no difference in moisture stress between bare-root or unlifted seedlings.Mud-packed seedlings, stored in the field for 19 days and subsequently planted, had higher survival and root growth than those having other storage conditions. The other storage conditions included higher and lower temperatures than in the field and light versus dark. Treatment of the mud-packs with fertilizer and vermiculite had no effect on any of the parameters measured.