Case study of a 536-years-old South American tree: biomass growth and carbon accumulation
Recent studies have shown that long-lived tropical trees are able to recover from senescence stages and maintain high rates of aboveground carbon and biomass accumulation throughout their life span. In this study, we present a tree-ring-based analysis to estimate the annual accumulation of aboveground biomass (AGB) and carbon (C-accumulation) of an Ocotea porosa tree over the last five centuries (1485–2016). The study site is located in southern Brazil, under a subtropical climate. AGB was estimated using a pantropical allometric equation, based on radial growth and intra-annual wood density (WD) measured by X-ray densitometry. The tree analyzed is estimated to be 536 years old, with a diameter of 220 cm (measured at a height of 2.23 m above the ground - environmental crime) and a total height of 23.9 m. Our estimate indicated a volume of 37.54 m³, corresponding to 19.15 Mg (min=0.00/max=0.14 Mg) of AGB and 9.57 Mg (min=0.00/max=0.7 Mg) of C-accumulation. Wood density profile showed a linear increase in density during the first 200 years (WD=0.42 ±0.04 g/cm³, r² =0.98), stabilizing at 0.51 ± 0.005 g/cm³, after this period. This trend reflects low rates of AGB and C-accumulation in the first life-century and an increase in subsequent years. Analysis of increment rates indicates two cycles of maximum accumulation of AGB and C-accumulation. One occurred in the 18th century (up to ~250th year) and the second over the 20th century, highlighting the 1940's. This study case suggests that old subtropical trees present growth plasticity, maintaining high rates of AGB and contributing to carbon stock in tropical forests. Further analyzes are in progress. Grant 2017/50085-3 and 2019/27110-7, Sao Paulo Research Foundation (FAPESP).