The dynamics of the production, chemical composition, and accumulated nutrients in litterfall are essential to understand the availability of nutrients and, consequently, possible gains in productivity in different forest types. Thus, the objective of the present study was to evaluate the litterfall and the accumulated nutrients in litterfall in a Pinus taeda plantation and native forest from southern Brazil. Two forest types: (i) an eight-year-old Pinus taeda L. plantation; and (ii) a native forest fragment, located in southern Brazil, were studied for four years. The monthly and annual litterfall production, chemical composition, accumulated nutrients, and nutrient use efficiency of the litterfall were evaluated. The Pinus taeda plantation showed higher values of leaves/needles litterfall and N, P, K, Ca and Mg use efficiency. This demonstrates that Pinus taeda plantations have a high production of needle biomass, which, in turn, has increased cell division, favoring the entry of these nutrients into the soil via decomposition. Our results show that total litterfall production did not significantly influence the accumulated nutrient and nutrient efficiency of litterfall, demonstrating that evaluating litterfall fractionation, such as leaves/needles, twigs and miscellaneous, is essential to understand the quantity and quality of litterfall and, thus, the nutrient cycling, which can contribute to possible silvicultural practices to be implemented, which can provide growth gains in forest types.

Atualmente o Pinus taeda é a espécie de maior importância utilizada em reflorestamentos na região Sul do Brasil servindo de base para a cadeia produtiva do setor madeireiro. O objetivo deste trabalho foi avaliar aos dois e sete anos de idade a resposta de Pinus taeda a adição de doses de fósforo logo após o plantio em Latossolo Vermelho de textura argilosa e média na região de Telêmaco Borba, Paraná. Foram instalados dois experimentos de campo, um no solo de textura argilosa e o outro em textura média, em delineamento de blocos ao acaso, com quatro repetições, no qual os tratamentos consistiram em doses crescentes de fósforo (0, 50, 75 e 100 kg ha-1 de P2O5). As doses de fósforo foram aplicadas na forma de superfosfato triplo (46% P2O5) em duas covetas laterais aos 30 dias após o plantio. O teor de fósforo disponível no solo foi caracterizado como muito baixo. Aos dois e sete anos foram medidos o diâmetro e altura total de 20 plantas por parcela, e o cálculo de volume por área. Os resultados indicaram que o uso de adubação fosfatada promoveu ganhos significativos na produtividade de Pinus taeda até sete anos de idade no Latossolo Vermelho de textura média, e a resposta se deu de forma linear com máxima produção para a dose de 100 kg ha-1 de P2O5. Para o Latossolo Vermelho de textura argilosa não houve resposta significativa ao uso de adubação fosfatada até os sete anos de idade.

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.

No Brasil, o Sistema Integrado de Diagnose e Recomendação (DRIS), já vem sendo muito utilizado como ferramenta de manejo nutricional em povoamentos de Eucalyptus e, atualmente são raros os estudos realizados com Pinus. Assim, objetivou-se realizar uma avaliação nutricional pelo sistema DRIS em um povoamento de Pinus taeda L., aos 19 meses de idade, plantado em Cambissolo na região dos Campos de Cima da Serra, RS. Foram usadas 64 doses de adubação, pela técnica do confundimento, para três fatores, com quatro níveis, distribuídos em quatro blocos, com doses de N (Ureia), P2O5 (Superfosfato triplo) e K2O (Cloreto de potássio). Foram coletadas três amostras compostas de acículas em cada um dos tratamentos (cada amostra formada por três árvores), determinando-se os teores médios de N, P, K, Ca e Mg. Para o cálculo das funções DRIS, foi usada a fórmula f = (R - r) / s, em que: f = valor da função para a relação (X/Y) entre os teores de dois nutrientes; R = valor da relação dual (X/Y); r = valor médio das relações duais (X/Y); s = desvio-padrão das relações duais (X/Y). A avaliação nutricional pelo DRIS indicou o N e o Ca como os nutrientes mais limitantes ao crescimento das plantas de Pinus taeda, aos 19 meses de idade, com a seguinte ordem de limitação: N = Ca > Mg > K > P; os teores ótimos estimados de N, P, K, Ca e Mg, pelo método do nível crítico gráfico, foram de 14,6; 1,6; 8,7; 2,6 e 0,8 g kg-1 respectivamente, indicando boas condições nutricionais das plantas de Pinus taeda.

Ciclagem de nutrientes em povoamento de Eucalyptus dunnii Maiden: produção de serapilheira e devolução de macronutrientes no bioma Pampa

The objective of this study was to evaluate whether there is an influence of different clonal hybrids of Eucalyptus urophylla on the carbon concentration and amount in below-ground biomass in trees cultivated in Oxisol, Brazil. Stumps and roots of three different eucalypt hybrid clones, AEC 0144, AEC 0223, and VM01, were selected, weighed immediately after being removed from the ground, and sampled for carbon determination and moisture content at the laboratory. The Shapiro-Wilk and Bartlett tests were used to evaluate data distribution and the homogeneity of variances, respectively. Analysis of variance (ANOVA) complemented by the Scott-Knott test was used to evaluate the effects of specie/hybrid on the below-ground biomass (dry matter) and carbon amount per stump. The hybrid type of Eucalyptus urophylla does not influence the carbon concentration; however, there is a difference in below-ground biomass production and carbon amount with it being higher for Eucalyptus urophylla × Eucalyptus camaldulensis when compared to the species Eucalyptus urophylla and hybrid Eucalyptus urophylla × Eucalyptus grandis.