Research has recorded the species was responsible for fixing over 674 tons of carbon per hectare. Once again science demonstrated that forests can reduce greenhouse gas emissions into the atmosphere. Plantations can compensate greenhouse gas emissions. The study also evaluated the quantity of stored carbon per native species in the Cerrado biome. Results reinforce the role of both natural and planted forests in accumulating carbon and mitigating climate changes. A study coordinated by Embrapa Cerrados in partnership with University of Brasília (UnB) shows that eucalyptus plantations can store large amounts of carbon in the biomass of their aerial parts and in the soil, similarly to natural Cerrado areas, contributing to the mitigation of emissions of greenhouse gases (GHGs), especially carbon dioxide (CO2). The results indicate high levels of carbon in eucalyptus plantations and area of natural vegetation they analyzed (over 183.99 tons per hectare - t/ha), accumulated in the soil, demonstrating that the species may contribute to the fixation of over 674.17 t/ha of CO2. Both natural and planted trees can act as carbon drains since they fix a high quantity of carbon through photosynthesis, allocating it in the biomass of their aerial parts (trunk and crown), in the roots, and add organic residues to the soil. Research suggests that forests in general play a fundamental role not only in the carbon cycle, but also contributes to minimizing global warming by reducing the circulation of greenhouse gases, such as nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2). “In that sense, planting trees in savannas to remove GHGs from the atmosphere should be considered, if not for the long term, at least for short-term carbon compensations. In the case of eucalyptus, they can be cut down after 7, 14, and 21 years of age to produce paper and cellulose, its main uses in Brazil”, Alcides Gatto, a researcher at University of Brasília and one of the authors of the study, points out. According to Brazilian Tree Industry’s 2022 Annual Report, Brazil has an approximate area of 10 million hectares of planted trees, out of which 76% are of eucalyptus plantations for commercial purposes, such as charcoal, paper, cellulose, fence posts, electricity poles, and timber for furniture and civil construction. The cycles from planting to felling range from 5 to 20 years, depending on the purpose of the wood. Alexsandra de Oliveira, a researcher at Embrapa Cerrados, mentions that there are numerous studies on soil carbon stocks and GHG mitigation in Cerrado areas converted into crops or pastures. However, despite the expansion of eucalyptus crops the biome, there still is little information on the impact of the crop on carbon stocks and on greenhouse gas emissions. Additionally, researchers point out that many studies are limited because they only measure carbon in the soil biomass or over the soil; however, it is also important to estimate carbon in the different compartments of the crop, such as roots and dead biomass in the Cerrado. “Since forests are important for carbon fixation, because terrestrial ecosystems, vegetation, and soil are the main carbon drains, information on carbon over the soil and in roots is essential to reduce uncertainties in regional metrics about areas of eucalyptus plantations in the Cerrado, and to feed into national models of carbon storage and climate change”, Eloisa Ferreira, a researcher at Embrapa Genetic Resources and Biotechnology, comments. Thus, the goal of this study was to quantify the carbon stock and the biomass per compartments of planted eucalyptus (Eucalyptus urophylla x Eucalyptus grandis hybrid) of different ages and estimate, through both direct and indirect methods, as well as the biomass and the carbon stock of an area with natural vegetation in the Cerrado biome. The study was carried out in a rural area in Paranoá, located in Brasília, Federal District; in neighboring areas with two eucalyptus crops: a 4-year-old one with EAC1528 clones and a 6-year-old with GG100 clones; and in an area of Cerradão, which is one of Cerrado formation types. Tree carbon The research team carried out a forest inventory to study the floristic composition of the Cerrado natural area. They found 84 species of 41 botanical families. The native species showed different storage capacities of biomass and carbon. Pau-terra (Qualea grandiflora),), with 161 trees/ha, was the species that most stored carbon, 2.87 t/ha (13% of the total), or 17.88 kg/ha per tree. However, pau-terrinha (Q. parviflora), with 24 trees/ha, was the individual species that most stored carbon: 77.88 kg/ha. Regarding the biomass and the carbon stored in the aerial part of the trees, wood was the component that contributed the most (81.35% in the youngest crop and 88.46% in the oldest one). According to the researchers, the eucalyptus wood is the part that most store biomass and carbon, whereas the storage in the other parts, such as bark, leaves, and branches, may vary according to the characteristics of the studied area. The biomass stock and carbon storage increased as plantations grew older. For the 4-year-old crop, the carbon and biomass accumulated in the aerial part were of 62.1 t/ha (27.5% of the total) and 141.1 t/ha, respectively, whereas the data of the 6-year-old one were of 81.7 t/ha (37.78% of the total) and 189.7 t/ha, respectively. Carbon in soil and roots The main carbon reserve found among the three studied areas is in the soil, which fixed 68%, 58%, and 84% of the total carbon, respectively, in the 4-year-old crop, 6-year-old crop, and natural Cerrado area. It was observed that the total soil carbon concentration decreases exponentially with depth. Research details Karina Pulrolnik, a researcher at Embrapa Cerrados, explains that the higher carbon concentration in the superficial layer (0 a 5 cm) is due to the deposition of organic material and slow decomposition in both planted and natural forests, which are rich in lignin and with a high carbon/nitrogen ratio, factors that increase the decomposition time of litter and the carbon in the soil levels. The density of thin roots also contributes to increase the level of carbon in the soil, even in those with low natural fertility, such as the Cerrado ones. The total carbon found in the soil profile 0 to 100 cm deep, the layer of 0 to 30 cm represented 48% of the total 4-year-old eucalyptus crop, 50% of the 6-year-old one, and 52% of the natural Cerrado area. The 4-year-old eucalyptus crop (154.23 t/ha) and the natural Cerrado area (154.69 t/ha) stored the highest amounts of carbon in all studied soil layers. It means that after 4 years of eucalyptus implementation, there was no reduction in carbon in the soil, whereas the 6-year-old eucalyptus crop presented the lowest values of carbon in the soil (126.26 t/ha). “The 4-year-old eucalyptus crop seemed to have replaced the carbon stocks in the first meter of soil depth, despite some losses that may have occurred right after its establishment. On the other hand, a significant loss of carbon in the soil of 18% (28.43 t/ha) was observed due to its alternative use, where a similar natural area was converted into agriculture, especially soybean crop and, a few years later, it became a 6-year-old eucalyptus crop”, Alexsandra de Oliveira comments. She adds that scientific studies show a decrease in carbon levels in the first years of the conversion of natural vegetation into other types of soil use, as grain crops, period in which a significant rate of carbon in the soil that was physically protected in stable aggregates is abruptly oxidized, resulting in mineralization and carbon loss to the atmosphere in the form of CO2. Roots presented the lowest contribution to total carbon storage: 4.9 t/ha in the 4-year-old eucalyptus crop, 1.9 t/ha in the 6-year-old eucalyptus crop, and 3.1 t/ha in the natural Cerrado area, considering a depth of 0 a 60 cm, representing, respectively, 2.16%, 0.88%, and 1.68% of the total carbon of the areas. Therefore, the 6-year-old eucalyptus crop stored most carbon in the aerial part, and the 4-year-old eucalyptus crop stored most carbon in the roots. Researchers point that the lowest quantity of superficial roots in the oldest crop might be related to the root proportion that grew deeper and deeper as the crop was getting older. Young eucalyptus stored the highest amount of carbon Despite the different results of the carbon dynamics among the parts of the trees, the youngest eucalyptus crop, or the 4-year-old one, presented the highest total carbon stocks in the roots and soil (226.23 t/ha), possibly due to the greatest biomass production in the early stages of growth, since the plant growth decreases as the years go by. However, according to the authors, this result indicates the necessity of further studies regarding commercial crops of different ages to confirm if the data is similar to the results in this work. Researchers highlight the remarkable capacity of both natural and planted forest species in fixing carbon dioxide (CO2), always presenting a positive balance, even discounting losses due to respiration, plant death, and gradual return of initially fixed CO2 to the atmosphere. They remember, however, that stored carbon is kept in live trees, in the litter, and in the organic matter of the soil for decades or even thousands of years in stable organic forms in the soil. “It validates the importance of both natural and planted forests as drains of greenhouse gases, especially CO2, because they mitigate climate changes, showing relevance to local sustainability and generation of carbon market”, says Fabiana Piontekowski Ribeiro, who is a forest engineer and was part of the doctoral program at University of Brasilia at the time this study was carried out. Authors of the study The paper, which can be accessed here, was authored by Fabiana Piontekowski Ribeiro, Alcides Gatto, Alexsandra Duarte de Oliveira, Karina Pulrolnik, Marco Bruno Xavier Valadão, Juliana Baldan Costa Neves Araújo, Arminda Moreira de Carvalho, and Eloisa Aparecida Belleza Ferreira.