Laurel forests in Tenerife, Canary Islands

Abstract

The general wood structure, vessel size and distribution along the stem xylem radius and in petioles were studied in Laurus azorica trees living in a Tenerife laurel forest. The fractions of volume occupied by dry matter, water and air in percentage of wood fresh volume were also studied. The wood showed a diffuse-porous structure, with solitary vessels or vessels somewhat clustered in small radially oriented groups. Vessels had a diameter ranging from 20 to 130 µm. This diameter was minimal close to the pith, increased more than 2-fold with age, and reached its maximum width close to the cambium. Vessel density decreased from 36 vessels mm -2 near the pith to about 13 vessels mm -2 near the cambium. Accordingly, the lumen area was small in young xylem close to the pith (0.0015 mm 2 ), reaching a value 5 times larger (0.007 mm 2 ) near the cambium than in the centre of the stem. Lumen area of vessels in petioles was about 1.5% of petiole cross-sectional area and thus much lower than in stems. Mean hydraulic diameter of these vessels was about 20 µm, and mean vessel density about 136 per petiole. There were only small differences in proportions of dry matter, water and air along stem radius. The relevance of each one of these fractions in the wood is discussed as evidence of the possible existence of a number of embolized vessels dispersed in the total functional cross-sectional area of the xylem.

Linking Dendrometry and Dendrochronology in the Dominant Azorean Tree Laurus azorica (Seub.) Franco

“…Franco) increment cores, there was a progressive color differentiation between earlywood, lighter, and latewood, darker, particularly at the ring boundary. There was no visible distinct heartwood in any of the taken increment cores, since no color change or difference in light transmission could be observed along the increment fresh cores, immediately after being taken, confirming earlier Laurus observations by [21,62].…”

“…In São Miguel Island we found a diffuse-porous wood structure in L. azorica, as reported for L. novocanariensis Rivas Mart., Lousã, Fern.Prieto, E.Días, J.C.Costa & C.Aguiar from Tenerife by Morales et al [21]. According to those authors, vessel distribution in the wood of Laurus suggests a high efficiency.…”

“…Meanwhile, in species with a random distribution of vessels, this often obscures the ring boundaries, making ring identification in diffuse porous genera particularly difficult [5]. However, L. azorica showed distinct growth rings as found for other Lauraceae, including the close relative, Laurus nobilis L. [21,27,30]. The greater difficulties found in L. azorica growth ring analysis corresponded to ring anomalies which can be originated by reaction wood, knots, compartmentalization by fungi or putrefaction, observed in the pith, and mainly in larger individuals.…”

“…Several xylem rays where visible, perpendicular to the ring boundaries, a trait that is very prominent in hardwoods, providing radial transportation functions [67]. Laurus azorica secondary xylem showed strict radial regularities, as found in Tenerife for L. novocanariensis [21]. As a hardwood species, L. azorica xylem vessels show very evident pits in tangential section, which allows for water transport between individual vessels.…”

Tree-ring distinctness, dating potential and climatic sensitivity of laurel forest tree species in Tenerife Island

“…Fortunately, this view has completely changed. Tropical dendrochronology has boosted in the last decades (Worbes, 2002;Rozendal and Zuidema, 2011;Brienen et al, 2016) and in Macaronesian laurel forests, annual tree rings have been registered in several native tree species from Azores (Matos et al, 2019;Pavão et al, 2022), Madeira (Pupo-Correia, 2016, and the Canary Islands, including the species used in this study (Peraza Oramas and López De Roma, 1967;Morales et al, 2002). However, the potential for studying the inter-annual variation of xylem secondary growth and the radial growth responses to climate fluctuations and drought still remains systematically unexplored.…”