STEM FORM AND GROWTH IN PICEA-ABIES (L) KARST IN RESPONSE TO WATER AND MINERAL NUTRIENT AVAILABILITY

Change of stem shape as a result of increased and/or decreased availab ility of water and mineral nutrients was studied in a Norway spruce (P icea abies (L.) Karst.) stand in southern Sweden. Water availability w as correlated inversely with average taper, defined as the ratio betwe en diameter at breast height and height of the tree. When moving from drought via control to irrigation, average taper gradually decreased. Fertilization without irrigation had no influence on average taper. St em form measurements indicated a decrease in diameter in the upper hal f of the stems following irrigation, whereas ammonium sulphate applica tion resulted in increased diameter in the upper half of the stems, co mpared with the control. The results emphasize the necessity of creati ng stand- and treatment-specific allometric relationships when estimat ing production in terms of volume or biomass, and of interpreting grow th based on basal area with caution.