Research note. Effects of early summer drought on the crown density of Norway spruce

Abstract

Norway spruce (Picea abies (L.) Karst.) is sensitive to drought stress. The species loses needles during and shortly after droughts, followed by a rapid recovery (Gruber, 1990). Past periods of regional decline in Norway spruce have been linked to drought, especially where the species does not grow naturally or where non-local provenances have been introduced (Innes, 1993). A study of changes in forest condition in Britain 1989 to 1992 reports that change in crown density in Norway spruce covaries with soil moisture deficits, annual potential evapotranspiration and depositions of sulphur (Mather et al., 1995). The results suggest that trees which tolerate the independent stresses of pollution and drought will exhibit signs of decline under circumstances of combined water and pollution stress (Macrez and Hubac, 1988; Pierre and Queiroz, 1988). Early summer drought occurred in southeastern Norway in 1992 and again in 1993. This paper explores the relationship between drought and crown density for Norway spruce, as observed in the national monitoring scheme