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A study of the growth of Douglas fir (Pseudotsuga menziesii) seedlings Schaedle, Michail

Abstract

The object of this work was to study the soil and nutrient requirements of Douglas fir seedlings in relation to their physiological development. For this purpose, fertilizer, irrigation, growth and nutrient uptake experiments were conducted at the Green Timbers Forest Nursery and the University of British Columbia. The experimental sites were characterized by chemical and physical soil analysis. The N, P, K, Ca and Mg content of 0-0 and 1-0 seedlings was determined. Statistical methods of analysis were used to determine the significance of experimental results. Douglas fir seedlings during the first year in the nursery (0-0) produced little dry matter and removed small amounts of nutrients from the soil. The application of 20 to 30 lbs. per acre of nitrogen increased the growth of 0-0 seedlings in 1957 and 1958. Fertilization with potassium decreased, and with phosphorus increased, the growth of 0-0 seedlings in 1957 but had no effect in 1958. Application of compost, mushroom manure and cow manure increased the growth of 0-0 Douglas fir seedlings. The fertilization of 0-0 seedlings with mineral fertilizers had no effect on their development in the subsequent year. In the second year of growth (1-0), the dry matter production and the removal of nutrients from the soil by Douglas fir seedlings exceeded that of many agricultural crops. During the summer, 1-0 Douglas fir seedlings passed through at least one period of temporary dormancy, but their growth was continuous throughout the summer. Nitrogen fertilization increased the length and dry weight of 1-0 seedlings. Application of 320 lb. N per acre decreased growth and resulted in damage to seedling tissues. High phosphorus application decreased the unfavourable effect of excessive nitrogen fertilization. The 1-0 seedlings did not respond to potassium fertilization. Phosphorus, however, increased the dry weight of the 1-0 seedlings when applied at a rate of 320 lb. P205 per acre. Late summer nitrogen applications resulted in very rapid seedling growth during autumn, however, dormancy was delayed and the seedlings were heavily damaged by frost. Nitrogen fertilization in September increased the frost resistance of dormant 1-0 seedlings. Irrigation increased the height and weight of 1-0 Douglas fir seedlings. Heavy irrigation decreased the winter hardiness of the seedlings. The duration and time of the dormant period was found to be influenced by fertilization and soil moisture conditions. Each seedling, however, had individual dormancy characteristics.

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