Norway spruce responses to drought forcing in areas affected by forest decline

Abstract

Aim of study: To assess the crown condition and radial growth of Norway spruce in plots with an increasing frequency and strength of drought during the last decades. Area of study: Northern Moravia, Czech Republic. Materials and methods: Crown condition assessment and dendrochronology analysis were used. Main results: Tree-ring width (TRW) was significantly influenced by previous autumn and current summer climate. The temporal variability of the growth-climate relationship shows that the impact of water sufficiency (precipitation, relative soil water content, drought index) markedly increased mainly during the 2000s and the 2010s. Most climate-growth relationships were significant only in the last two or three decades. The observed crown conditions and their relationships with TRW also indicate stress intensification during the same period. Our results suggest that water availability was the main factor affecting radial growth and the occurrence of negative pointer years and was probably also the factor triggering the decline. Research highlights: In these current site and climate conditions, the silviculture of Norway spruce is extremely risky in the study area. Our results have also shown that the observed climate change is too dynamic for long-term forest plans, especially with regard to recommended forest species composition.