FLORESTA, Curitiba, PR, v. 49, n. 4, p. 641 - 650 , out/dez 2019. Momolli, D. R. et.al. ISSN eletrônico 1982-4688 DOI: 10.5380/rf.v49 i4.56727 641 NUTRIENT CYCLING IN EUCALYPTUS DUNNII: MICRONUTRIENTS IN THE LITTERFALL Dione Richer momolli 1* , Mauro Valdir Schumacher 2 , Aline Aparecida Ludvichak 1 , Kristiana Fiorentin dos Santos 3 Huan Pablo de Souza 1 , Claudiney do Couto Guimarães 1 1 Federal University of Santa Maria, Postgraduate Program in Forest Engineering. Santa Maria, Rio Grande do Sul, Brasil – dionemomolli@gmail.com*, aline_lud@yahoo.com.br, huan.pablo@hotmail.com, claudiney.couto@hotmail.com 2 Federal University of Santa Maria, Prof. Full. Department of Forest Sciences, Santa Maria, RS - Brasil. E-mail: mvschumacher@gmail.com 3 Blumenau Regional University Foundation, Postgraduate Program in Forest Engineering. Blumenau, Santa Catarina, Brasil. kristianafiorentil@gmail.com Recebido para publicação: 05/12/2017 – Aceito para publicação: 18/02/2019 Resumo Ciclagem de nutrientes em Eucalyptus dunnii: micronutrientes na serapilheira produzida. A avaliação da produção de serapilheira e retorno de nutrientes é importante para a compreensão da dinâmica de ciclagem de nutrientes. Embora exigidos em quantidades inferiores pelas plantas, os micronutrientes possuem importância singular na regulação biogeoquímica. O objetivo do presente estudo foi quantificar a serapilheira produzida e a concentração de micronutrientes nas diferentes frações e estações do ano em um povoamento de Eucalyptus dunnii. Foram demarcadas 4 parcelas de 20 m x 21 m. A coleta da serapilheira da fração folhas, galhos finos (diâmetro < 0,5 cm) e miscelânea, deu-se pela instalação de 4 coletores com área de 0,5 m² em cada parcela. Para a quantificação da fração galhos grossos (diâmetro > 0,5 cm), em cada parcela foram demarcadas 4 áreas úteis das árvores de diâmetro médio. A fração foliar representou 59 % da serapilheira e a ordem de transferência foi Mn > Fe > B > Zn > Cu, totalizando 8,04 kg ha -1 . A fração foliar apresentou as maiores concentrações para B e Mn. A produção de serapilheira mostrou-se estacional com verão e primavera diferindo estatisticamente do inverno e a variável temperatura explica o padrão de deposição da mesma. Palavras-chave: fertilização; sustentabilidade; nutrição florestal. Abstract The evaluation of litterfall and nutrient return is important for understanding the dynamics of nutrient cycling. Although required in smaller quantities by plants, micronutrients have unique importance in biogeochemical regulation. The objective of the present study was to quantify the litterfall and the concentration of micronutrients in the different fractions and seasons of the year in Eucalyptus dunnii stand. Four plots of 20 m x 21 m were demarcated. The collection of leaf litter, twigs (diameter <0.5 cm) and miscellaneous resulted in the installation of 4 collectors with an area of 0.5 m² in each plot. For the quantification of the thick branches fraction (diameter> 0.5 cm), four useful areas of medium-diameter trees were demarcated in each plot. The leaf fraction represented 59% of litterfall and the transfer order was Mn> Fe> B> Zn> Cu, totaling 8.04 kg ha -1 . The leaf fraction presented the highest concentrations for B and Mn. The litterfall was seasonal with summer and spring differing statistically from winter and the temperature variable explains the deposition pattern of the same. Key-words: fertilization; sustainability; forest nutrition INTRODUCTION With the growth of the world population, coupled with the increased consumption of forest products, commercial tree plantations have been one way out of meeting these demands. The world area occupied by tree plantations grew by 5 million hectares between 2000 - 2010 (FAO, 2015). According to IBÁ (2016), in Brazil and the state of Rio Grande do Sul, this increase was verified, registering an increase of 60.7 and 58.1%, respectively. In the state of Rio Grande do Sul, the largest expansion of the area was in the Pampa Biome, characterized by its sandy texture and low natural fertility (SUERTEGARAY and SILVA 2009). Studies evaluating litterfall are important for understanding nutrient cycling, which provide support for the establishment of management techniques, fertilization and help in understanding interactions with the environment (SILVA et al., 2013). Although many studies evaluate litterfall and nutrient return in ecosystems (CORRÊA et al., 2013), few studies report micronutrients in forest formations (CORRÊA et al., 2016). To understand nutrient cycling, it is necessary to evaluate the behavior of micronutrients and their relationship with macronutrient concentration in forest species (SOBRADO, 2014). Although required in small