WATER RELATIONS, GAS-EXCHANGE AND MORPHOLOGICAL DEVELOPMENT OF FALL-PLANTED AND SPRING-PLANTED YELLOW CYPRESS STECKLINGS

Yellow cypress (Chamaecyparis nootkatensis (D.Don) Spach) stecklings ( stock derived from rooted cuttings) were fall (September 1990) and spr ing-planted (April, 1991) on a coastal reforestation site in British C olumbia to determine the influence of planting season and various nurs ery cultural treatments on steckling establishment, growth and surviva l, Gas exchange and water relations measurements were made in the firs t year after planting, with morphological development monitored during the first and second year. A randomized complete block design (6 bloc ks) was used and influence of planting season was analyzed as an indep endent factor from the nursery cultural treatments. Nursery cultural t reatment means within each plant-time population were similar (t-test, a = 0.05), with no effect on steckling physiology during the first gr owing season. Moisture stress nursery cultural treatments produced sma ller stecklings (e.g. shoot height, diameter, root and shoot dry weigh ts) than well-watered treatments, but morphological differences disapp eared after the first year, Water relation parameters indicated that f all-planted stock had greater turgor maintenance than spring-planted s tock throughout the first growing season (e.g. fall greater than or eq ual to spring in predawn and minimum shoot water potentials, total and utilized turgor, fall less than or equal to spring in osmotic potenti al at saturation and turgor loss point, and relative water content at turgor loss point). Spring-planted stecklings had greater maximum net photosynthesis under optimum conditions in a controlled environment, b ut had lower net photosynthesis under low air temperature conditions i n the field, compared with fall-planted stecklings. Fall-planted steck lings had greater stomatal conductance under all measured field climat ic conditions, except moderate conditions when both populations had si milar stomatal conductance, Shortly after fall planting, extreme envir onmental conditions (i.e. soil surface temperatures of 42 degrees C, e vaporative demand > 4 kPa and steckling minimum shoot water potentials of -1.61 +/- 0.04 MPa) resulted in high fall-planted steckling mortal ity, As a result, survival rates measured 8 weeks after spring plantin g were 82.9% and 99.8% for fall- and spring-planted stecklings, respec tively, Thereafter, spring planting, mortality was low and similar bet ween the two plane-time populations. Fall-planted stecklings had great er root development early in the first growing season, but by season e nd, spring-planted stecklings had greater root development. At the end of the second growing season, both populations were similar in shoot development, though spring-planted stecklings had greater root develop ment.