Comparing natural and planted black spruce seedlings. I. Water relations and growth

Abstract

Container-grown black spruce (Piceamariana (Mill.) B.S.P.) seedlings were planted during 2 consecutive years alongside natural black spruce seedlings of similar initial height on an upland boreal forest clearcut. Acclimation of the planted seedlings to site conditions was followed by comparing needle conductance, shoot water potential, and growth of the planted seedlings to values obtained on the natural seedlings. Relative growth rates of the newly planted seedlings were significantly lower than those of the natural seedlings, but the difference was smaller during their second season in the field. Predawn and midday shoot water potential as well as midday needle conductance showed significant but relatively small differences between planted and natural seedlings during both years. On any given date of measurement, no clear relation could be found between water status and growth in planted seedlings. Seasonal midday averages of shoot water potential, needle conductance, and soil–plant resistance to water movement were related to the relative growth rates of all seedling types over the course of the two growing seasons. Seasonal averages of midday shoot water potential appeared to best reflect the acclimation of the planted seedlings to site conditions.