Quantification of aboveground and belowground biomass and associated organic carbon in two olive cultivars (Arbosana and Picual) grown at high density

[EN] Accurate quantification of biomass production and carbon accumulation in olive orchards is crucial for optimizing their agronomic management and assessing their potential to mitigate climate change negative impacts. In this study, two methodologies (destructive and non-destructive) were developed and tested to quantify aboveground and belowground biomass, and their carbon content, in 7.5-year-old trees of two widely cultivated olive cultivars (Arbosana and Picual), at field and under Mediterranean climate conditions. Picual accumulated more biomass (36.5 kg tree⁻¹) than Arbosana (27.5 kg tree⁻¹), mainly due to a greater investment in components like trunk and non-primary branches. Conversely, Arbosana allocated more biomass to leaves. In both cultivars, around 60% of the root biomass was at the top 25 cm of soil, and over 55% was concentrated in the root ball. Weighted average carbon concentration was 47% in aboveground biomass and 42% in roots. At the orchard scale, soil was the main organic carbon pool, around 76 t C ha-1, compared to 13-16 t C ha-1 in the total olive tree biomass. Average annual carbon accumulation rate in olive biomass ranged from 1.68 t C ha-1 yr-1 (Arbosana) to 2.16 t C ha-1 yr-1 (Picual), within the range of C fixation rates in Mediterranean agroecosystems. Destructive sampling captured cultivar differences in biomass and C content more accurately, whereas non-destructive method proved more suitable and accessible for large-scale use. These results help integrate biomass and C content data into olive genotype selection and management strategies, to increase carbon sequestration and sustainability of olive grove systems.