Effects of clone and cutting traits on shoot emergence and early growth of willow

Abstract

To assess if size differences between plants in establishing willow stands may be caused by differences between cuttings prior to planting, plant response (survival, sprouting in terms of emergence time and shoot number, and growth in terms of shoot size, weight and leaf area) was quantified as a function of clone, original position on shoots from which cuttings are derived, cutting length, cutting diameter, and field storage time. Longer and thicker willow cuttings developed more and taller shoots and displayed a higher biomass production than shoots from short and thin cuttings. Cuttings derived from apical positions along shoots displayed for a given diameter a higher shoot biomass production than cuttings derived from the more basal parts. The effect of position was related to differences between cuttings with regard to phenology, bud burst for cuttings from high positions having progressed further after a fortnight than buds on cuttings from basal stem parts. A two week field storage of shoots prior to planting led to a decrease in early biomass production. We conclude that the planting system based on the use of entire shoots comprises a considerable amount of pre-emergence variation in the cuttings, which underlies size variation development during early establishment of willow plantations. To obtain a faster and more even establishment of willows, we recommend the use of larger and more even-sized cuttings, and a shortest possible field storage time.