In semiarid conditions, the cambium in trees may have several periods of activity and dormancy in the same year. This results in wood anatomical anomalies like intra-annual density fluctuations (IADF). Tree-rings and wood anomalies in stone pine (Pinus pinea) and Aleppo pine (Pinus halepensis) growing at two semiarid sites, Guardamar and Daroca in Spain, were studied. Based on the structure of growth rings the following types of wood anomalies were proposed: (1) type E (latewood-like cells within earlywood), (2) type E+ (latewood-like cells between earlywood and latewood of the previous tree-ring), (3) type L (earlywood-like cells within latewood), and (4) type L+(earlywood-like cells between latewood and earlywood of the next tree-ring),(5) type M (false multiple ring) and (6) type N (incomplete ring). In addition, the transition from early- to latewood, clearness of the tree-ring boundary and the presence of resin canals were investigated. The pictures of wood anomalies were presented and their frequencies in different calendar years shown for both sites and species. Response function analyses showed that tree-ring, early- and latewood widths were strongly positively correlated with precipitations from December to June in both species and sites. Some species and site-specific responses to climate were recorded. The work was completed in cooperation between the University of Ljubljana and the University of Alicante, Spain, in the frame of ERASMUS LLP bilateral agreement on student exchange.
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