Depression and growth recovery of silver fir in uneven-aged Dinaric forests in Croatia from 1901 to 2001

Abstract

The causes of the decline of silver fir across Europe in the 1960s and 1970s and its subsequent recovery remain open to debate. We studied the radial growth of silver fir and possible influential factors on growth decline in uneven-aged silver fir-Norway spruce- European beech forests in the Dinaric Mountains of Croatia (180 000 ha) since 1900 using dendrochronological methods. Data on the radial growth of large firs (diameter at breast height >50 cm) sampled in 2002 across the region (151 plots, 491 m(2) each), regional climatic data (temperature, precipitation and drought) and SO2 emissions were used in both statistical and dynamic factor analyses. Two main growth patterns of fir trees were identified: the first features a sharp decline in radial growth in the period 1966-1983, followed by a dramatic recovery, while the second is characterized by a relatively constant increase in radial growth. The most influential climatic factors were mean monthly temperatures in February, July and August ; mean precipitation in May and September ; and summer drought. However, SO2 emissions explained a larger part of the total variability of radial growth than climatic factors (46-60 per cent and 0-42 per cent, respectively). The growth recovery of silver fir supports further application of uneven-aged silviculture in the region.