Revista Árvore ISSN: 0100-6762 [email protected] Universidade Federal de Viçosa Brasil Araujo Skorupa, Alba Lucia; de Barros, Nairam Félix; Lima Neves, Júlio César FOREST LITTER DECOMPOSITION AS AFFECTED BY EUCALYPTUS STAND AGE AND TOPOGRAPHY IN SOUTH-EASTERN BRAZIL Revista Árvore, vol. 39, núm. 6, noviembre-diciembre, 2015, pp. 1055-1064 Universidade Federal de Viçosa Viçosa, Brasil Available in: http://www.redalyc.org/articulo.oa?id=48843584008 How to cite Complete issue Scientific Information System More information about this article Network of Scientific Journals from Latin America, the Caribbean, Spain and Portugal Journal's homepage in redalyc.org Non-profit academic project, developed under the open access initiative Forest litter decomposition as an effect... 1055 FOREST LITTER DECOMPOSITION AS AFFECTED BY EUCALYPTUS STAND AGE AND TOPOGRAPHY IN SOUTH-EASTERN BRAZIL1 Alba Lucia Araujo Skorupa2, Nairam Félix de Barros3 e Júlio César Lima Neves3 ABSTRACT – Forest litter decomposition is a major process in returning nutrients to soils and thus promoting wood productivity in the humid tropic. This study aimed to assess decomposition of eucalypt litter in the Rio Doce region, Brazil. Leaf litter was sampled under clonal eucalypt stands aged 2, 4 and 6 years on hillslopes and footslopes. Soil and soil+litter samples were incubated at two levels of soil moisture, temperature and fertilization. C-CO2 emissions from soil measured during 106 days were higher at 32 °C than at 23°C, mainly for the 2-yr-old stand on footslope. When leaf litter was added on soils, C-CO2 emissions were eight times higher, mainly on footslopes, with no effect of stand age. Leaf decomposition in situ, assessed with a litterbag experiment showed a mean weight loss of at least 50% during 365 days, reaching 74% for 2 yr-old stands on footslopes. In comparison with data from the native forest and the literature, no apparent restrictions were found in eucalypt litter decomposition. Differences between in vitro and in situ results, and between eucalypt and native forest, were most likely related to the response of diverse decomposer communities and to substrate quality. Keywords: Soil respiration; Litterbag; CO2 evolution. DECOMPOSIÇÃO DE SERAPILHEIRA FLORESTAL: EFEITO DA IDADE DO EUCALIPTO E TOPOGRAFIA NO SUDESTE DO BRASIL RESUMO – A decomposição de serapilheira florestal é um processo importante ao retornar nutrientes ao solo e, assim, estimular a produtividade da madeira no trópico úmido. Este trabalho objetivou avaliar a decomposição de serapilheira de eucalipto na região do rio Doce, MG. Frações foliares foram amostradas em plantações de eucalipto nas idades de 2, 4 e 6 anos e posições de encosta e baixada. Amostras de solo e solo + fragmentos de folhas foram incubadas em dois níveis de umidade, temperatura e fertilização. A quantidade de C-CO2 emitida pelo solo no período de 106 dias foi maior na temperatura de incubação de 32 oC do que a 23 oC, especialmente em solos de baixada, na idade de 2 anos. A respiração do solo foi intensificada oito vezes pela presença de fragmentos de folhas sobre o solo, principalmente em solos da baixada, e não houve efeito significativo para a idade. A decomposição foliar in situ, avaliada em um experimento de sacos de decomposição, apresentou perda média de no mínimo 50% durante 365 dias, alcançando 74% para o eucalipto em dois anos, na baixada. Após a comparação com uma mata nativa e dados da literatura nacional, não foi encontrada nenhuma restrição aparente na decomposição da fração foliar do eucalipto. Diferenças entre os resultados in vitro e in situ e entre a mata nativa e o eucalipto podem estar relacionadas a uma diferente comunidade de decompositores e à qualidade do substrato foliar. Palavras-chave: Respiração do solo; Sacos de decomposição; Emissão de CO2. 1 Recebido em 24.07.2012 aceito para publicação em 21.10.2015. 2 Universidade Federal de Viçosa, Centro de Ciências Agrárias, Departamento de Engenharia Florestal, Viçosa, MG - Brasil. E-mail: <[email protected]>. 3 Universidade Federal de Viçosa, Centro de Ciências Agrárias, Departamento de Solos, Viçosa, MG - Brasil. E-mail: <[email protected]> e <[email protected]>. Revista Árvore, Viçosa-MG, v.39, n.6, p.1055-1064, 2015 http://dx.doi.org/10.1590/0100-67622015000600008 1056 SKORUPA, A.L.A. et al. 1. INTRODUCTION granite and gneiss. Soil used in this incubation has pH values from 4.4 to 5.9, and soil organic matter between Forest litter decomposition plays an important 13 and 18 g kg-1 under eucalypt stands. Under native role in returning nutrients to soil, and is critical to forest, soil organic matter is higher (28 g kg-1), and the productivity of fast-growing tree plantations in soil pH is 5.9. the humid tropics. However, there have been reports th of intense litter accumulations (>25 Mg ha-1) under Soil and leaf litter were sampled in December 7 eucalypt stands in Southeastern Brazil (Gama-Rodrigues 2000, under Eucalyptus grandis x E. urophylla hybrid et al., 2008; Palha Leite, F., unpublished data), raising clonal stands (3 x 2.5 m spacing) aged 2, 4 and 6 yrs concern about proper nutrient cycling. Identifying on footslope and hillslope positions, and under a native the causes of such unbalances can be difficult since forest on the footslope. For each combination of stand factors such as phenology and litter quality interact age and topographic position, recently abscised leaves, with the biotic and abiotic environment, and also varying from green to yellow-green colors, were collected o because of seasonal and yearly climate variation. in triplicate on the forest floor and stored at 4-7 C for Measuring litter decomposition processes is important the CO2-C evolution assessment. Leaf lignin was in assessing litter dynamics, but difficult because determined by the acid detergent fiber method of Van decay rates and decomposer organisms vary over time Soest and Wine (1968). In each sampling plot described and space (PRESCOTT, 2005). Additionally, stand age above, soil from the 0-20 cm depth was sampled and and position in the landscape can affect the stored at 4-7 °C for two weeks before incubation. decomposition process because of their effect on litter Soils were incubated with and without leaf litter production and site properties, but this has seldom fragments. The sampled leaf material was air-dried and been studied (BARGALI, 1996; ALVAREZ-SÁNCHES; cut to approximately 0.5 x 0.5 cm fragments. Subsequently, ENRÍQUEZ, 1996). 15 g of leaf fragments were brought to 80% water This study aimed to investigate potential restrictions retention capacity and placed onto 50 g of air-dried to eucalypt litter decomposition and nutrient cycling soil sieved <2 mm contained in 0.6 dm³ glass jars. in the Doce River region, which may be related to stand Incubations were conducted at two levels of temperature, age, topographic position, temperature, soil moisture moisture and fertilization. The average minimum and maximum monthly temperatures of the region, respectively and fertility. To test this hypothesis, leaf litter from 23 and 32°C, were used. Soil moistures were 40 and different combinations of ages and topographic positions 80% of the water holding capacity. Fertilization levels were incubated at different temperatures, soil moistures were 0 and 5 mL of a solution with 50 mg L-1 P(KH PO ), and fertilizations. In addition, a litterbag experiment 2 4 80 mg L-1 N(NH Cl), and 80 mg L-1 K(KCl). was established to assess decomposition and nutrient 4 release in situ. The CO2 evolved was trapped with NaOH and titrated with HCl using phenolphthalein as indicator, after 2. MATERIAL AND METHODS addition of BaCl2 to precipitate sodium carbonate (ANDERSON, 1982). The first titration was done after The study area is located in the Doce River near 2 days of incubation, followed by a new incubation Belo Oriente, Minas Gerais, Brazil (19°18’S and 42°22’W), for 3 days and titration, and so on, for 4, 6, 8, 10, 12, with a mean altitude of 336 m above sea level. The 14, 20, and 27 days, in a total of 106 days. Results were natural vegetation is semi-deciduous tropical forest. expressed in CO -C mg g-1 soil evolved, according to According to the Koeppen classification, the climate 2 the formula: is a tropical humid, with mean annual temperature and precipitation of 25.2°C and 1,000-1,280 mm, respectively. In general, the rainy season is from October to March, comprising about 80% of mean annual precipitation. Potential annual evapotranspiration varies from 950 where [HCl] = HCl concentration; f = correction to 1,200 mm, with an annual water deficit between 30 factor for HCl concentration; 6 = equivalent mg of C- and 90 mm. The dominant soils in the area are Oxisols CO2 Vb = volume (mL) of HCl spent with blank; Va = and Ultisols of clayey texture developed from Proterozoic volume (mL) of HCl spent to titrate NaOH from samples. Revista Árvore, Viçosa-MG, v.39, n.6, p.1055-1064, 2015 Forest litter decomposition as an effect... 1057 The experimental design was a completely randomized stands. There was no effect of topographic position factorial design, in which the main factors were stand on nutrient concentrations. No significant differences ages in three levels (2, 4 and 6 yrs) and topographic were found for carbon, lignin concentration and C:N, positions in two levels (footslope and hillslope), summing C:P and lignin:N ratios in eucalypt leaf litter due to stand up to six main plots. Additionally, a split-plot was used, age and topographic position. The mean C:N ratio of as each main plot was subdivided into a combination eucalypt leaf litter was 40:1, similar to values reported of three incubation factors in two levels: soil moisture, by Sodré (1999) in Southeast Bahia, Brazil.