The growth of past, present, and future forests was, is and will be affected by climate variability. This multifaceted relationship has been assessed in several regional studies, but spatially resolved, large-scale analyses are largely missing so far. Here we estimate recent changes in growth of 5800 beech trees (Fagus sylvatica L.) from 324 sites, representing the full geographic and climatic range of species. Future growth trends were predicted considering state-of-the-art climate scenarios. The validated models indicate growth declines across large region of the distribution in recent decades, and project severe future growth declines ranging from −20% to more than −50% by 2090, depending on the region and climate change scenario (i.e. CMIP6 SSP1-2.6 and SSP5-8.5). Forecasted forest productivity losses are most striking towards the southern distribution limit of Fagus sylvatica, in regions where persisting atmospheric high-pressure systems are expected to increase drought severity. The projected 21st century growth changes across Europe indicate serious ecological and economic consequences that require immediate forest adaptation.
The responses of the vascular cambium and tracheid differentiation to extreme drought in Aleppo pine (Pinus halepensis Mill.) were investigated. The research focused on the drought year of 2005, in the primary study area at Maigmo (MAI) in southeastern Spain, with comparisons in Jarafuel (JAL) and Guardamar (GUA). The climate in this region is typically warm and dry with hot summers. Wood formation throughout the 2005 growing season was studied in transverse microtome sections and integrated with a retrospective dendrochronological analysis of crossdated increment cores collected in 2009. For most anatomical sections collected throughout the growing season at MAI, the vascular cambium appeared to be dormant as indicated by the low number of cells per radial file. Occasionally, immature xylem derivatives were observed during the growing season but without production of an annual ring. In increment cores collected at MAI, the 2005 position in the annual ring series contained either a narrow ring of both earlywood and latewood (47% of samples), a narrow ring of apparent latewood with no earlywood (13%), or a missing ring (50%). We introduce the term “dark ring” to refer to those annual rings of apparent latewood with no earlywood. For trees at JAL, the 2005 ring had below-average width and contained both earlywood and latewood. At GUA, the trees produced the widest 2005 ring of all three sites and mainly contained an intra-annual density fluctuation (IADF). The IADF was formed after cambial reactivation in the autumn. Although dark rings, IADFs, and especially missing rings complicate dendrochronological analysis, these anatomical features may provide an additional proxy record from which to infer climate variability and change in the past.
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