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

Abstract

As in many archipelagos, the Azorean primary forest was largely cleared and replaced by secondary forest and grassland, the Azorean tree Laurus azorica (Seub.) Franco being one of the dominant trees in the remaining natural forests. Dendrochronological and dendrometric studies in the Azores mainly focused on non-indigenous trees, either used for timber (e.g., Cryptomeria japonica D. Don) or considered as invasive (Pittosporum undulatum Vent.). Therefore, this study aims to describe the growth ring anatomy of L. azorica, and to understand the relationship between dendrometric traits (e.g., trunk diameter at breast height; tree height), and the number of growth rings. Growth ring anatomy was accessed by wood anatomical preparation of microcore samples while tree age estimation was based on growth ring counts in wood cores taken at breast height and at base. A total of 145 trees were sampled, resulting in 262 increment cores, at six representative stands of laurel forest in São Miguel Island (Azores). The wood anatomical analysis confirmed the presence of clear annual ring boundaries, and a high structural similarity towards Laurus novocanariensis Rivas Mart., Lousã, Fern.Prieto, E.Días, J.C.Costa & C.Aguiar. Age at tree base averaged 33 years, with 60% of the trees between 25 and 50 years old, and only about 15% above 50 years old. This suggests the existence of a secondary forest that is more recent than expected, probably due to human disturbance. The allometric models showed best fit when calculated by stand, suggesting the effect of local environmental conditions on growth rate. Radial growth rate was estimated at 0.68 cm.year−1. Given the known dominance of this species and the threats affecting natural forests, this baseline study will allow a better understanding of forest distribution and dynamics, and support a more effective forest management approach.

Oceanic Island forests buried by Holocene (Meghalayan) explosive eruptions: palaeobiodiversity in pre-anthropic volcanic charcoal from Faial Island (Azores, Portugal) and its palaeoecological implications

“…The studied samples are comparable to L. azorica wood anatomy (e.g. Peraza and Lopez de Roma, 1967;Loutfy, 2009;Schweingruber and Landolt, 2010;Schweingruber et al, 2011;Wheeler, 2011;Matos et al, 2019), particularly the vessel tangential lumina length and distribution and grouping, the mean vessel length, the presence of simple perfora tion plates, and septate fibers. In some specimens, latewood fiber walls are thick, without visible lumina or septa and totally vitrified (e.g.…”

Taxonomic, structural diversity and carbon stocks in a gradient of island forests

“…As expected, PF showed high values 51 , and NF the lowest values of total carbon storage. The latter could be due to climatic and soil limitations, since large stature forests, although rare, are still present at sheltered low altitude locations in the Azores, but also to differences in tree age and growth rate, estimates of which are still lacking for most Azorean trees 102 .…”

“…The small height in NF could be associated with environmental conditions in montane belts where trees with contorted trunks and branches, dense compact crowns, small and hard leaves are found 61 . Moreover, the submontane forest dominated by Laurus azorica has been mostly replaced by pastureland or exotic woodland 61 , 72 , 94 , the existing stands being limited in distribution range and in age, with many relatively young trees 102 , often being invaded by P. undulatum or A. melanoxylon 81 , 88 . One such examples is the Laurus dominated forest that we sampled at Povoação (São Miguel Island).…”

“…It is clear, nonetheless, that if a carbon market is to be established in the Azores, natural forests could regain importance, since, as a surplus, they harbor huge amounts of native and endemic species of plants and animals 72 . Notwithstanding, for more precise estimates of carbon sequestration, their growth rate should be considered, making dendrochronological studies more relevant 102 , 105 .…”

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.…”