Stand responses to initial spacing in Norway spruce plantations in Norway

Abstract Using data from nine spacing experiments of Norway spruce (Picea abies (L.) Karst.) in Norway, covering wide ranges of site index and initial spacing, this study evaluated stand basal area and volume responses to initial spacing and examined whether these responses varied by stand ages or site quality. We developed nonlinear regression models that described the standing basal area or volume responses to initial spacing along with site index and stand ages. The results show that closer spacings produced higher standing basal area and volume than wider spacings. The response curves are highly nonlinear in younger stands and become nearly linear in mid-rotation stands, indicating stronger responses at younger ages and weaker responses as age increases. Furthermore, for young stands, spacing effects are stronger at closer than at wider spacings. The basal area and volume responses to initial spacing tend to be similar across site indices. However, the interaction of site index and stand age on spacin...