• Smith, C.J.
  Department of Forestry and Wood Science, University College of North Wales, Bangor, Wales
  
• Wellwood, R.W.
  Department of Forestry and Wood Science, University College of North Wales, Bangor, Wales
  
• Elliott, G.K.
  Department of Forestry and Wood Science, University College of North Wales, Bangor, Wales
  

Selected wood and cell characteristics were examined in increment cores from two 46-year-old pines that had been fertilized with ammonium sulphate 37, 38 and 39 years after planting. Fertilization increased the ring-width and greatly reduced the latewood percent and the bulk density of both early and late wood; the effects were greatest shortly after the last application of fertilizer, but remained apparent for at least five further years. Though both trees produced more earlywood cells only one of the two produced more latewood.

The average tracheid diameter was not changed, though its range within the annual ring was increased. There were decreases in tracheid wall-thickness and length, and in wall volume per tracheid. These changes were greatest in latewood, so that the difference between early and latewood was reduced, while the characteristics of the earlywood were exaggerated. Resin canal radial (but not tangential) diameter and  cross-sectional area increased, though numbers of canals per unit area of ring was unchanged.

Correlations with temperature, insolation and rainfall in March-June and July-October suggest that (1) wood properties are influenced by the weather of both the current and the previous growing seasons; (2) the climatic optima for the fertilized and unfertilized trees are different and consequently (3) the weather influences the effect of fertilization on wood properties.