Effects of growth rates, tree morphology and site conditions on longevity of Norway spruce in the northern Swiss Alps

Longevity of trees is known to be associated with growth rates, but also with tree morphology and spatial influences. However, very little quantitative information is available on the effects of these biotic and abiotic influences on maximum ages of trees. The objectives of this study were to investigate the trade-off between longevity and growth rates of Norway spruce (Picea abies) and to quantify the effects of tree morphology and abiotic site conditions on longevity of this species. Data were collected along different topographical and climatic gradients in a 20?×?25?km study area in the northern part of the Swiss Alps (Glarus). The ages of the more than 100 sampled dead Norway spruces ranged between 50 and 367?years. Longevity of these trees was negatively related to tree growth, i.e. slow-growing trees tended to grow older than fast-growing trees. Tree height was positively associated with longevity for both upper and lower storey trees. Longevity of lower storey trees was increased with large crown diameter, but decreased with long crown length. Upper storey trees growing at higher altitude tended to get older than at lower altitude. We conclude that the combined effects of growth rates, variability in site conditions and different traits of tree morphology determine tree longevity of Norway spruce in the Swiss Alps. Because longevity is tightly linked to mortality rates of tree populations, our study may improve our understanding of long-term processes of forest dynamics under current and future climate.