Nutrientes e carbono em Khaya
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Data
2025-02-27
Autores
Carvalho, Matheus Azevedo
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Universidade Federal do Espírito Santo
Resumo
This study aimed to evaluate the stem of Khaya grandifoliola, Khaya senegalensis, and Khaya ivorensis at 8 years and 7 months of age and to determine whether these species differ in their biomass, nutrient, carbon, and nutrient use efficiency (NUE) stocks. The study site is located in the Vale Natural Reserve, in the municipality of Linhares, Espírito Santo, Brazil (19°09′01.2″ S and 40°04′48.7″ W). A preliminary census was carried out, from which five trees of average diameter were selected for felling. From each tree, three 5 cm discs were removed at the base, middle, and top of the trunk. Two opposing wedges were then taken from each disc to represent heartwood and sapwood proportionally, and these wedges were separated into stembark and stemwood compartments. The samples were oven-dried to a constant weight, ground, and taken to the laboratory for determination of carbon, macro, and micronutrient contents on for each tree. Stemwood and stembark biomass were estimated based on the census of the same stand. Using the nutrient content and biomass data from the felled trees, a principal component analysis (PCA) was performed, considering statistical significance, collinearity, and coefficient of variation (CV). Nutrient and carbon stocks were calculated as the product of average nutrient content and census-based biomass. For the calculation of NUE, the ratio between nutrient content for each tree and its respective biomass was used. The contents, biomass, stocks, and NUE were subjected to analysis of variance and Tukey’s test (p < 0.05), while the PCA was subjected to a PERMANOVA (Permutational Multivariate Analysis of Variance). Macronutrient contents in the stembark followed the same order: Ca > N > K > Mg > S > P, whereas the stemwood nutrient order varied according to species. The biomass of K. senegalensis had the highest proportion of stembark (24.13%) relative to stemwood. In contrast, K. ivorensis showed the lowest stembark biomass but the highest stemwood biomass, not differing statistically from K. grandifoliola. The stemwood biomass of K. senegalensis was about 13% lower than that of the other species. The PCA indicated clustering among the Khaya species, explaining 83% of the total variance in three principal components (PC1 = 36.1%; PC2 = 26.4%; PC3 = 20.5%). K. senegalensis exhibited high stembark stocks of N (68.83 kg ha-1), P (4.33 kg ha-1), and K (53.37 kg ha-1) and high stemwood stocks of N (72.66 kg ha-1), Mg (12.91 kg ha-1), and P (10.66 kg ha-1), in addition to the highest carbon accumulation in stembark (3.07 Mg ha-1). K. ivorensis had the highest stemwood stocks of K (77.75 kg ha-1) and Fe (360.98 g ha-1), yet the lowest stocks of N and Ca. K. grandifoliola presented the highest stemwood stock of Ca and intermediate values for the other nutrients. Stemwood carbon stock did not differ among the species, with an average of 11.77 Mg ha-1. NUE in the stembark did not differ among species. In the stemwood, K. ivorensis demonstrated greater efficiency in the use of N, Ca, Mg, and Cu, but lower efficiency for Fe; K. grandifoliola was more efficient in the use of Zn, Mn, and K; and K. senegalensis stood out only in the NUE of Fe, showing low efficiency for N, Mg, and Mn.
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Estoque de carbono , Mogno-africano , Eficiência de utilização de nutrientes