Nutrient fluxes in litterfall of a secondary successional alluvial rain forest in Southern Brazil

During forest succession, litterfall nutrient fluxes increase significantly. The higher inputs of organic matter and nutrients through litterfall affects positively soil fertility and the species composition, which are essential components in forest restoration and management programs. In the present study, the input of nutrients to the forest soil via litterfall components was estimated for two sites of different development stages, in an early successional alluvial rain forest in Brazil. Litterfall returned to the soil, in kg/ha, ca. 93 N, 79 Ca, 24 K, 15 Mg, 6 P, 1.7 Mn, 0.94 Fe, 0.18 Zn, 0.09 Cu and 11.2 Al, in the site where trees were more abundant and had higher values of basal area. In the other area, where trees where less abundant and values of basal area were comparatively low, litterfall returned <50% of those amounts to the forest soil, except for Al. The amount of Al that returned to the soil was similar in both areas due to the high contribution of Tibouchina pulchra (82% of Al returned). Comparatively, high proportion of three dominant native tree species (Myrsine coriacea, T. pulchra and Cecropia pachystachya) explained better litter nutrient use efficiency (mainly N and P) in the site with the least advanced successional stage. Although litterfall of these species show lower nutrient concentrations than the other tree species, their nutrient fluxes were high in both sites, indicating a certain independence from soil essential nutrients. Such feature of the native species is very advantageous and should be considered in forest restoration programs. Rev. Biol. Trop. 59 (4): 1869-1882. Epub 2011 December 01.

Durante la sucesión secundaria forestal, el flujo de nutrientes en la hojarasca se incrementa significativamente. Los altos ingresos de materia orgánica y nutrientes a través de la hojarasca afecta positivamente la fertilidad del suelo y la composición de especies, las cuales son componentes esenciales para programas de restauración forestal y de manejo. En el presente estudio, el ingreso de nutrientes a través de la hojarasca y sus componentes fueron estimados para dos sitios de una selva lluviosa atlántica aluvial en sucesión temprana. La cantidad anual de elementos que ingresan al suelo desde la vegetación más desarrollada (sitios con alta área basal y abundancia de árboles) fueron (en kg/ha): 93 N, 79 Ca, 24 K, 15 Mg, 6 P, 1.7 Mn, 0.94 Fe, 0.18 Zn, 0.09 Cu y 11.2 Al. Menos de la mitad de esas cantidades fueron aportadas por la vegetación menos desarrollada, excepto para el Al. La cantidad de Al aportada a este sitio fue similar a la contribución de la vegetación más desarrollada, debido a la contribución de: Tibouchina pulchra (82% de todo el Al aportado). La eficiencia en el uso de nutrientes de la hojarasca (principalmente de N y P) de la vegetación menos desarrollada fue superior a la eficiencia de una más desarrollada, debido a la alta proporción de tres especies nativas dominantes (Myrsine coriacea, Tibouchina pulchra y Cecropia pachystachya) en la primera. Si bien la hojarasca de esas especies presenta menor concentración de nutrientes que las otras especies arbóreas, el flujo de nutrientes fue mayor (para ambos sitios), marcando una cierta independencia de los nutrientes esenciales del suelo. Las cantidades de esas especies deberían ser consideradas con mayor atención para su uso en programas de restauración forestal.

CAÍDA DE HOJARASCA Y DINÁMICA DE NUTRIENTESEN PLANTACIONES DE Acacia mangium (MIMOSACEAE)DE ANTIOQUIA, COLOMBIA. / Litterfall and Nutrient Dynamics in Acacia mangium (Mimosaceae)Forest Plantations of Antioquia, Colombia

La producción de hojarasca, el retorno y la reabsorción de nutrientes, y la eficiencia en su uso, fueron estudiados durante un año en plantaciones de Acacia mangium estable-cidas en suelos degradados por minería aurífera en la región del Bajo Cauca colom-biano. La producción anual de hojarasca fina fue de 10,4 Mg ha-1 y estuvo dominada por la fracción foliar (54%), seguida del material reproductivo (24%), y en menor pro-porción por otros restos (6%) y hojas de otras especies (1,5%). Los mayores retornos de materia orgánica y nutrientes se presentaron en los sitios clasificados como de calidad alta, en tanto que la práctica de subsolado del suelo, previo establecimiento de las plantaciones, no mostró efectos significativos sobre estos. La hojarasca foliar mostró una concentración alta de N y consecuentemente, dados los altos valores de producción de esta fracción, un retorno potencial alto de N. El P, con baja concentración foliar y un bajo retorno potencial, además de los altos valores de los índices de eficiencia en su uso y de reabsorción foliar, fue el nutriente más limitante. Los altos valores de producción de hojarasca fina y de retorno potencial de nutrientes determinados en este es-tudio, muestran que la especie Acacia mangium tiene un gran potencial para la recupera-ción de áreas degradadas, a partir del restablecimiento de los ciclos biogeoquímicos.

Fine litter production, nutrient return, nutrient resorption, and nutrient use efficiency were studied during one year in Acacia mangium forest plantations in mining gold degraded soils at the Bajo Cauca region of Colombia. Annual fine litter production was estimated at 10.4 Mg ha-1 and it was dominated by the leaf fraction (54%), followed by the reproduc-tive material (24%) and to a lesser proportion by other debris (6%) and other species leaves (1.5%). The highest organic matter and nutrients returns were found on sites classified as high quality. Soil plowing realized previous Acacia mangium planting, did not show any significant effect on organic matter and nutrients returns. A. mangium leaf litter had a high N concentration and consequently, given the high leaf litter production values, it was found a high N return. By the opposite, leaf litter P content and P returns via litter fall were very low. The high values found for P retranslocation and P use efficiency indexes showed that P was the most limiting nutrient for the species. The high values of fine litter production and nutrient return via leaf litter indicate that A. mangium has a great capacity for degraded areas reclamation, as of the restoration of the biogeochemical cycles.

Produção de matéria seca e eficiência nutricional para P, Ca e Mg em leguminosas herbáceas / Dry matter production and nutritional efficiency for P, Ca and Mg in herbaceous legumes

As leguminosas para adubação verde têm sido introduzidas nos sistemas agrícolas para a recuperação de solos desgastados pelo uso intensivo. O objetivo desse trabalho foi avaliar a resposta de leguminosas herbáceas à aplicação de calcário e fósforo sobre a produção de biomassa e eficiência nutricional para o P, Ca e Mg. O experimento foi desenvolvido em casa-de-vegetação do Departamento de Ciência do Solo da Universidade Federal Rural da Amazônia, utilizando-se um Latossolo Amarelo distrófico coletado na profundidade de 0 - 20 cm, em Belém, PA. O delineamento experimental usado foi o de blocos ao acaso, com arranjo de tratamentos em um fatorial 3³, onde foram comparadas três espécies de leguminosas: mucuna preta (Stizolobium atterrimum), mucuna cochinchinensis (Stilozobium cochinchinensis) e feijão-de-porco (Canavalia ensiformes); três níveis de calagem: de calcário dolomítico (0, 4 e 8 t.ha-1) e de fósforo (0, 25 e 45 mg.dm-3), com quatro repetições cada um. Mucuna cochinchinensis e o feijão de porco produziram maiores quantidades de biomassa vegetal do que a mucuna preta, sendo que a primeira espécie acumulou maior quantidade de P e a segunda maior quantidade de Ca. Mucuna cochinchinensis apresentou maior eficiência de utilização de P, Ca e Mg na ausência da calagem. Nos solos intemperizados com baixa concentração de P, Ca e Mg, o feijão-de-porco e a mucuna cochinchinensis poderão ter melhor desempenho do que a mucuna preta, visto que apresentaram maior eficiência de translocação e de utilização desses nutrientes, respectivamente.

The legumes used for green manure have been introduced in agricultural systems for recovering degraded soils by intensive use. The objective of this work was to evaluate the response of herbaceous legumes to liming and P application on dry matter and its nutritional efficiency. The experiment was developed in greenhouse at the Soil Science Department of the Federal University Agricultural of Amazon (Brazil). Soil used was a dystrophic Yellow Latosol, sampled in the 0 - 20 cm depth. A randomized block experimental design was used with treatments arranged in a factorial 3³, comparing three legume species: velvet bean (Stizolobium atterrimum), "mucuna cochinchinensis" (Stilozobium cochinchinensis) and jack bean (Canavalia ensiformes); three doses of liming (0, 4 and 8 t ha-1 of limestone) and of triple superphosphate (0, 25 and 45 mg P dm-3 of soil), with four replications each one. Results showed that "mucuna cochinchinensis" and jack bean produced higher amounts of dry matter than velvet bean. The first species accumulated higher amount of P and the second species higher amount of Ca in the tissue. The "mucuna cochinchinensis" species showed higher use efficiency of Ca, Mg and P in the absence of liming. The jack bean and mucuna cochinchinensis can have better performance than velvet bean, in weathered soils with low concentration of P, Ca and Mg, since they presented higher translocation efficiency and use of these nutrients, respectively.