The basic wood density influences the carbon stock, playing a crucial role in climate-changing global mitigation through carbon sequestration. Understanding wood carbon release depends on the Nitrogen assessment and CN ratio. Therefore, our research aimed to: (i) Compare basic density, organic carbon, nitrogen, and C/N ratio among the Khaya grandifoliola, K. ivorensis, and K. senegalensis; (2) Analyze the gradient along positions and diameter of the commercial stem; (3) Recommend the most representative sampling position for each species based on the diameter. The experimental area is located in Southeastern Brazil. Twelve average-diameter trees per species were cut down, and wood disc samples were collected at 0, 25, 50, 75, and 100% commercial height. Our results show statistical differences in wood basic density among the species, and K. senegalensis has the highest basic density, 592 kg m³. There was no statistical difference in organic carbon between species and along the stem. Stem diameter instead of commercial height improved the variable studied, confirming the research hypothesis. Sampling at 17% of the commercial height, ranging to 18–22 cm stem diameters, is recommended for greater representativeness.

Wood from reforestation gains market value due to its sustainable and legal origin. Planted forests in Brazil play a crucial role in economic, social and environmental aspects, with Eucalyptus and Pinus dominating the timber sector. However, non-majority species, such as those of the Khaya genus, have attracted great commercial interest due to the quality of their wood, being seen as an alternative to Brazilian mahogany. This study aimed to evaluate the biomass production of Khaya spp. stands and the nutrient uptake impacts in different harvesting scenarios. The research area is in Reserva Natural Vale (RNV) in Sooretama, Espírito Santo state, Brazil. The study was conducted 9.5 years after the planting of the Khaya spp. monoculture at a spacing of five m × five m, and the base fertilization consisted of 150 g of yoorin thermophosphate and 15 g of FTE BR 12 per seedling. The seedlings were of seminal origin, coming from different regions of Brazil and corresponding to three species: Kkaya grandifoliola C.DC (Belém-PA), Khaya ivorensis A. Chev. (Linhares-ES) and Khaya senegalensis A. Juss. (Poranguatu-GO). K. senegalensis exhibited the highest percentage of bark, while K. ivorensis was found to have the highest percentage of leaves. The biomass of the stems and branches did not vary by species. The relative biomass proportions had the following order: branches > stems > bark > leaves. The stocks of Ca and Mg were higher for K. grandifoliola, exceeding those for K. senegalensis (22.1%) for Ca and for K. ivorensis (42.3%) for Mg. The lowest nutrient uptake occurred in the scenario in which only the stem was removed, with averages of 44.17, 10.43, 21.93, 52.59 and 9.97 kg ha⁻¹ for N, P, K, Ca and Mg, respectively. Compared to total biomass harvesting, this represents a reduction in export levels by 91.34% for N, 79.31% for P, 94.66% for K, 94.29% for Ca and 93.28% for Mg. The nutrient uptake assessment demonstrated that more conservative harvest scenarios resulted in lower nutrient losses, indicating the importance of forest management practices that prioritize soil and nutrient conservation. In summary, the findings of this study provide a solid basis for the sustainable management of Khaya spp., highlighting implications for productivity and nutrient dynamics on a small or medium scale.

ANÁLISE QUALI-QUANTITATIVA DA ARBORIZAÇÃO DE CINCO PRAÇAS EM JERÔNIMO MONTEIRO, ESPÍRITO SANTO

The study aimed to describe the influence of different planting spacings in aboveground biomass and soil carbon stocks, in 7.5 years old Anadenanthera peregrina (L.) Speg. var. peregrina stands, hypothesizing that smaller spacings might enhance carbon storage. The stands are located in Espírito Santo, Brazil and were planted in 2011. Blocks were allocated in a randomized block design to evaluate three treatments: 3 m x 3 m, 4 m x 4 m and 5 m x 5 m tree spacings. Samples up to 100 cm were taken for carbon determination and soil bulk density. 10 trees were felled and their aboveground biomass measured. Soil and aboveground biomass C stocks were calculated. The aboveground biomass C stock did not change in different spacing. Soil C stock was not influenced by the spacings, with total C stock of 122.93, 106.09 and 97.08 Mg ha-1 for 3 m x 3 m, 4 m x 4 m and 5 m x 5 m, respectively. The intensification of carbon storage in smaller spacings was not confirmed. The study reveals inedited information about carbon storage in A. peregrina var. peregrina stands and demands new investigations regarding different soil characteristics. The species do have potential for carbon storage regardless of tree spacing.

Nutrient removal through timber harvesting can affect the long-term sustainability of forest plantations, particularly when species differ in biomass allocation and nutrient use. Understanding these differences is therefore essential for developing species-specific nutrient management strategies. This study evaluated differences in stem biomass allocation, nutrient and carbon stocks, and nutrient use efficiency (NUE) among 8.6-year-old Khaya grandifoliola, K. ivorensis, and K. senegalensis. This study was conducted in a plantation located at Reserva Natural Vale, Brazil, where five trees per species were sampled. Discs collected from the base, middle, and top of the commercial stem were separated into stemwood and stembark for chemical analyses. Biomass, nutrient and carbon stocks, and NUE were estimated, and differences among species were assessed using univariate and multivariate analyses. Macronutrient concentrations in the stembark followed the order Ca > N > K > Mg > S > P. K. senegalensis had the highest proportion of stembark (24.13%) and accumulated greater stocks of several nutrients and carbon in this compartment, as well as higher N, P, and Mg stocks in stemwood. In contrast, K. ivorensis showed the highest K and Fe stocks in stemwood, whereas K. grandifoliola accumulated the greatest amount of Ca. Stemwood carbon stocks averaged 11.77 Mg ha⁻¹ and did not differ among species. Nutrient use efficiency also differed among species, with K. ivorensis showing greater efficiency for N, Ca, Mg, and Cu, K. grandifoliola for K, Zn, and Mn, and K. senegalensis for Fe. The results revealed species-specific patterns of biomass allocation, nutrient accumulation, and nutrient use efficiency. K. senegalensis, which had the highest proportion of stembark, also accumulated greater stocks of several nutrients and carbon in this compartment, highlighting the potential value of retaining bark after harvesting to support nutrient return to the soil. However, the species-specific patterns of nutrient accumulation indicate that the implications for nutrient export depend on the element considered. These findings can inform species selection and harvesting practices aimed at improving nutrient conservation in Khaya spp. plantations.