Stock quality and field performance of Douglas fir seedlings under varying degrees of water stress

Abstract

An experiment was carried out on 12 Douglas fir seedling lots that were 3 years old and had all originated from the same seed lot. Treatments consisted in combining stock type with three different height to diameter ratios, storage duration and method (long at 2°C or short in various conditions), and protection from desiccation (by bagging or not). Seedling lots were assessed at planting by root electrolyte leakage (REL), root moisture content (RMC) and predawn shoot water potential (ψwp). They were planted simultaneously in well-watered or water-stressed conditions. Performance level was based on survival and height growth at the end of the growing season. Slender seedlings not bagged had the lowest values of RMC, ψwp and field performance. The sturdier stock type was less sensitive to desiccation and had 100 % survival, in all stress conditions. In contrast to RMC and ψwp, REL was not influenced by stock type. RMC and ψwp values were highly correlated, on a seedling basis as on a batch basis. RMC was the best predictor of the field performance parameters (survival and growth for both water regimes) which were all well correlated. Moreover, lower stock quality resulted mainly in slower growth in the well-watered field trial, and in poor survival under drought conditions. (© Inra/Elsevier, Paris.).