A new chronology of Cedrela fissilis (VELL.) (Meliaceae) for Southern Brazil: a combination of classical dendrochronology and radiocarbon dating

FONTANA, CLAUDIA; LIDIO LOPEZ

Belen

Congreso; A new chronology of Cedrela fissilis (VELL.) (Meliaceae) for Southern Brazil: a combination of classical dendrochronology and radiocarbon dating; 2023

Universidade Federal do Pará

Widely distributed in the tropical regions of South America, Cedrela fissilis is a long-lived treespecies that can exceed 350 years of age. Its growth rings are distinguished by a semi-ring-porousand axial marginal parenchyma wood structure. Because of its longevity, wide geographicaldistribution and well-marked annual rings, C. fissilis is commonly used in dendrochronologicalstudies. However, radiocarbon (14C) bomb pulse dating has shown that, in Suriname, under a bimodal precipitation regime, species of this genus are able to produce two rings per year. Nonetheless,other classical chronologies validated by the 14C bomb pulse have shown that C. fissilis, and otherspecies of the genus, form annual rings at sites where there is only one distinct wet and dry seasonper year. For this investigation, we used bomb-peak 14C dating to test whether the classicaldendrochronological approach accurately dates the growth rings of a population of C. fissilis growingin the subtropical forest in Brazil under a well-distributed rainfall regime throughout the year. Thestudy area is in the Brazilian Southern Plateau, Santa Catarina State (27° 9.908´S; 51° 34.639´W). Theclassical chronology was built using 24 C. fissilis trees. Visual dating was checked using the ProgramCofecha v6.06P, and the residual chronology built using the Program Arstan v48c. The years 1957,1962, 1963, 1966, 1969 and 1974 were selected from samples with well-defined rings and the highestcorrelation with the chronology to be independently evaluated by the 14C bomb pulse method.Classical cross-dating showed synchronism in radial growth between trees (r = 0.507; rbar = 0.242),with high values of climate sensitivity (MSI = 0.561) and a satisfactory expressed population signal(EPS = 0.86). Here, 14C bomb pulse of selected calendar years showed that the trees were accuratelydated by the classical cross-dating approach. In this respect, C. fissilis appears to form annual growthrings, even in places where the rainfall regime is relatively equally distributed throughout the year.The consistent match between 14C signatures in tree rings with those expected for the atmosphereduring the nuclear era (after 1950) confirmed that well-dated subtropical tree-ring records can be usedfor paleoclimatic reconstructions of these regions, in addition to many other applications in ecologicalstudies.