Summer drought: a driver for crown condition and mortality of Norway spruce in Norway
Summer drought, i.e. unusually dry and warm weather, has been a significant stress factor for Norway spruce in southeast Norway during the 14 years of forest monitoring. Dry and warm summers were followed by increases in defoliation, discolouration of foliage, cone formation and mortality. The causal mechanisms are discussed. Most likely, the defoliation resulted from increased needle-fall in the autumn after dry summers. During the monitoring period 1988–2001, southeast Norway was repeatedly affected by summer drought, in particular, in the early 1990s. The dataset comprised 455 ‘Forest officers’ plots’ with annual data on crown condition and mortality. Linear mixed models were used for estimation and hypothesis testing, including a variance–covariance structure for the handling of random effects and temporal autocorrelation.
Document Type: Research Article
Publication date: April 1, 2004