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Background: Cocoa is an important tropical tree crop that is mainly cultivated in agroforestry systems (AFS). This system, known as cabruca in northeastern Brazil, holds promise to reconcile biodiversity conservation and economic development. However, since cocoa AFS alters forest structure composition, it can affect litter dynamics in riparian zones and streams. Thus, our objective was to determine litter inputs and standing stocks in riparian zones and streams under three types of forest: managed cocoa AFS, abandoned cocoa AFS, and secondary forest. Methods: We determined terrestrial litter fall (TI), vertical (VI) and lateral (LI) litter inputs to streams, and litter standing stocks on streambeds (BS) in the Atlantic Forest of northeastern Brazil. Litter was collected every 30 days from August 2018 to July 2019 using custom-made traps. The litter was dried, separated into four fractions (leaves, branches, reproductive organs, and miscellaneous material) and weighed. Results: Terrestrial litter fall was similar in all forests, ranging from 89 g m-2 month-1 in secondary forest (SF) to 96 g m-2 month-1 in abandoned cocoa AFS (AC). Vertical input were higher in AC (82 g m-2 month-1) and MC (69 g m-2 month-1) than in SF (40 g m-2 month-1), whereas lateral input were higher in MC (43 g m-2 month-1) than in AC (15 g m-2 month-1) and SF (24 g m-2 month-1). Standing stocks followed the order SF > AC > MC, corresponding to 425, 299 and 152 g m-2. Leaves contributed most to all litter fractions in all forests. Reproductive plant parts accounted for a larger proportion in managed AFS. Branches and miscellaneous litter were also similar in all forests, except for higher benthic standing stocks of miscellaneous litter in the SF. Despite differences in the amounts of litter inputs and standing stocks among the forests, seasonal patterns in the abandoned AFS (AC) were more similar to those of the secondary forest (SF) than the managed AFS, suggesting potential of abandoned AFS to restore litter dynamics resembling those of secondary forests.

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Tropical forests are the largest contributors to global emissions of carbon dioxide (CO2) to the atmosphere via soil respiration (R s). As such, identifying the main controls on R s in tropical forests is essential for accurately projecting the consequences of ongoing and future global environmental changes to the global C cycle. We measured hourly R s in a secondary tropical moist forest in Puerto Rico over a 3-year period to (a) quantify the magnitude of R s and (b) identify the role of climatic, substrate, and nutrient controls on the seasonality of R s. Across 3 years of measurements, mean R s was 7.16 ± 0.02 µmol CO2 m-2 s-1 (or 2,710 g C m-2 year-1) and showed significant seasonal variation. Despite small month-to-month variation in temperature (~4°C), we found significant positive relationships between daily and monthly R s with both air and soil temperature, highlighting the importance of temperature as a driver of R s even in warm ecosystems, such as tropical forests. We also found a significant parabolic relationship between mean daily volumetric soil moisture and mean daily R s, with an optimal moisture value of 0.34 m3 m-3. Given the relatively consistent climate at this site, the large range in mean monthly R s (~7 µmol CO2 m-2 s-1) was surprising and suggests that even small changes in climate can have large implications for ecosystem respiration. The strong positive relationship of R s with temperature at monthly timescales particularly stands out, as moisture is usually considered a stronger control of R s in tropical forests that already experience warm temperatures year-round. Moreover, our results revealed the strong seasonality of R s in tropical moist forests, which given its high magnitude, can represent a significant contribution to the seasonal patterns of atmospheric (CO2) globally.

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Drought periods may change mangrove litterfall production through water deprivation and increasing tree evapotranspiration, but these impacts have been rarely estimated. In Brazil, an intense drought and strong winds impacted mangrove forests leading to mass tree mortality in 2016, suggesting that forest productivity also declined rapidly. Fifteen months after the initial impact, we started to monitor and quantify litterfall production in paired transects from disturbed and undisturbed mangroves. The litterfall production of the undisturbed forests (575 ± 28 Kg C ha-1 y-1) was 31- to 3-fold higher than that at the disturbed mangrove forests (18 to 169 Kg C ha-1 y-1). The strong decline in litterfall production may have implications to the export of nutrients to estuarine ecosystems. Our baseline suggests that mangrove forests are greatly vulnerable to climate impacts and that the litterfall production collapse in dead mangrove forests may impair marine ecosystem food webs.

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Recent studies have shown the importance of subtropical forests as terrestrial carbon sinks and also their vulnerability to human disturbances and climate change. The Semi-deciduous Atlantic Forest presents large extensions replaced by productive uses, such as tree plantations, and forest remnants showing high levels of structural heterogeneity. No studies have performed carbon stock densities estimations in different pools in the region. We wonder how changes in forest structure and forest replacement by pine plantations affect ecosystem carbon stock densities in different pools and fluxes. We performed carbon estimates based on field data and compared closed (CF) and open (OF) canopy natural forest patches and Pinus taeda plantations at harvest age (PP). Structural changes in the natural forest had a profound effect on the ecosystem by halving the forest carbon stock while pulp-intended pine plantations reached the carbon stock of closed forest at harvest age. Main changes from CF to OF were a 55% decrease in the carbon of biomass and a 42% decrease in SOC. Instead, carbon stock density in biomass of PP was similar to CF but the carbon in fallen deadwood was 78% lower while in the litter layer was double; the SOC at 0-5 cm depth was 31% lower in PP than CF. Our study shows that structural changes in the natural forest halve the forest carbon stock while pulp-intended pine plantations can reach the closed forest carbon stock at harvest age. However, PP do not seem to be effective for carbon storage in the long term because of regular harvesting and clearing and their short-life products. Therefore, to effectively store the forest carbon, arresting deforestation, replacement and degradation of the original forest is crucial.

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Chronological measurements of litterfall production can be used for understanding ecosystem dynamics such as net primary production and carbon cycling in highly seasonal ecosystems such as tropical dry forests (TDF). This paper presents data on litterfall production and meteorology in an old-growth TDF. The data was generated within the Monte Mojino Reserve located in the Sierra de Alamos - Rio Cuchujaqui Natural Protected Area in northwestern México. For litterfall collection, twenty randomly placed litterfall traps were installed to collect monthly litterfall production across four full growing seasons (48 monthly collections). Meteorological data were obtained from an automatic micrometeorological station that recorded data in situ from January 2013 to March 2019. The database includes litterfall production [g m-2 month-1], monthly rainfall [mm], air temperature [°C], relative humidity [%] and photosynthetic active radiation [µmol m-2 s-1].

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Este artículo es una revisión bibliográfica sobre las funciones ecológicas que caracterizan a los bambúes, por las cuales merecen un mayor reconocimiento e inclusión en los programas de restauración ecológica. Los bambúes son un grupo de plantas muy diverso, de amplia distribución geográfica y económicamente importante. Aunque son más reconocidos por los usos comerciales, su potencial de uso en programas de restauración ecológica es prometedor, ya que pueden ser eficientes en la prestación de varios servicios ambientales relacionados con el suelo, el agua y el secuestro de carbono. Su rápido crecimiento, junto con su capacidad para controlar la erosión y mantener el agua a nivel del suelo, así como para proporcionar nutrientes mediante la descomposición de la hojarasca, convierte a los bambúes en un grupo valioso para la recuperación de áreas degradadas y para la restauración productiva de ecosistemas, en particular a través de sistemas agroforestales. Los enfoques agroforestales pueden combinar diferentes especies de bambú con otros cultivos, para satisfacer las necesidades humanas y generar a la vez beneficios para los ecosistemas. De manera similar, los bosques o plantaciones de bambúes, junto con sistemas agroforestales mixtos, pueden actuar como áreas de conexión y corredores biológicos, en paisajes muy fragmentados, proporcionando refugio y alimento para una amplia diversidad de organismos. A pesar de las percepciones de que los bambúes pueden ser invasivos, las pruebas para apoyar esto son limitadas. Recomendamos una evaluación cuidadosa de las características biológicas de las especies de bambúes seleccionadas, antes de su implementación en proyectos de restauración productiva y de recuperación de los servicios ambientales.

This article is a bibliographic review on the ecological functions that distinguish bamboos, for which they deserve greater recognition and inclusion in ecological restoration programs. Bamboos are a highly diverse, geographically widespread and economically important plant group. Although they are more recognized by commercial uses, their potential for use in ecological restoration programs is promising, as they can be effective in delivery of several environmental services related to soil, water and carbon sequestration. Their rapid growth, along with their abilities to control erosion and maintain water at soil level, as well as provide nutrients by litterfall decomposition, make them a valuable group for recovery of degraded areas and in productive restoration of ecosystems, in particular via agroforestry systems. Agroforestry approaches can combine different bamboo species with other crops, to meet human needs while generating benefits for ecosystems. Similarly, bamboo forests or plantations together with mixed agroforestry systems can act as stepping-stones and biological corridors, in very fragmented landscapes by providing shelter and food for a wide diversity of organisms. Despite perceptions that bamboos can be invasive, evidence to support this is limited. We recommend careful evaluation of the biological characteristics of bamboo species selected, prior to deployment in productive restoration projects and for the recovery of environmental services.

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Abstract We report the first known infestation of mangroves by the invasive moth Hyblaea puera in Paraná, Southern Brazil. The infestation caused massive defoliation of Avicennia schaueriana trees, affecting approximately 20,000 hectares of mangroves. We discuss the implications for conservation and management, focusing on protected areas, the ecology of mangroves, and local livelihoods.

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Termites are abundant arthropods in tropical ecosystems and actively participate in the process of litter decomposition. The objective of this study was to evaluate the population structure of Microcerotermes indistinctus in arboreal nests and to estimate their contribution to the consumption of wood litter in an area of Caatinga, a type of seasonally dry tropical forest located in the Brazilian semi-arid region. The populations of fifteen nests were quantified and separated into castes, "larvae", and eggs. Wood blocks of four typical Caatinga species were offered to termites under laboratory conditions. Litter production was estimated in the area over the course of one year. The mean population size of M. indistinctus was 73,897 individuals/nest, while the mean nest density in the area was 25 active nests/ha. Total consumption of the four types of wood was estimated to be 10.5 mg of wood/g termite (fresh weight)/day. Based on consumption and population size, M. indistinctus consumes 0.35% of the total litter and 1.71% of the annual production of branches and twigs in the area. Wood-consuming termites are highly affected by anthropogenic disturbances in the semi-arid region of Brazil, putting the ecosystem services they perform related to the process of litter decomposition at risk.

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We review data from coastal Pacific Panama and other tropical coasts with two aims. First, we defined inputs and losses of nitrogen (N) mediating connectivity of watersheds, mangrove estuaries, and coastal sea. N entering watersheds-mainly via N fixation (79-86%)-was largely intercepted; N discharges to mangrove estuaries (3-6%), small compared to N inputs to watersheds, nonetheless significantly supplied N to mangrove estuaries. Inputs to mangrove estuaries (including watershed discharges, and marine inputs during flood tides) were matched by losses (mainly denitrification and export during ebb tides). Mangrove estuary subsidies of coastal marine food webs take place by export of forms of N [DON (62.5%), PN (9.1%), and litter N (12.9%)] that provide dissimilative and assimilative subsidies. N fixation, denitrification, and tidal exchanges were major processes, and DON was major form of N involved in connecting fluxes in and out of mangrove estuaries. Second, we assessed effects of watershed forest cover on connectivity. Decreased watershed forest cover lowered N inputs, interception, and discharge into receiving mangrove estuaries. These imprints of forest cover were erased during transit of N through estuaries, owing to internal N cycle transformations, and differences in relative area of watersheds and estuaries. Largest losses of N consisted of water transport of energy-rich compounds, particularly DON. N losses were similar in magnitude to N inputs from sea, calculated without considering contribution by intermittent coastal upwelling, and hence likely under-estimated. Pacific Panama mangrove estuaries are exposed to major inputs of N from land and sea, which emphasizes the high degree of bi-directional connectivity in these coupled ecosystems. Pacific Panama is still lightly affected by human or global changes. Increased deforestation can be expected, as well as changes in ENSO, which will surely raise watershed-derived loads of N, as well as significantly change marine N inputs affecting coastal coupled ecosystems.

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Abstract: Restingas are sandy areas spread along the Brazilian coast made up of a mosaic of forest and open woodland vegetation adapted to varying conditions of aridity, oligotrophy and salinity. Two vegetation types are very common in southeast Brazilian restingas, open Clusia formations and seasonally dry forest formation. Litter production and nutrient (C and N) turnover were studied comparatively in forest formations and Clusia formations, in vegetation patches with and without Clusia hilariana. The results showed that the breakdown process is extremely retarded in Clusia formations, with or without C. hilariana, leading to C accumulation in the soil. Microbial and soil fauna activity is lower in Clusia formations in comparison to forest formations; patches without Clusia hilariana showed intermediate conditions regarding total matter and carbon loss. Nitrogen loss was lowest in patches without C. hilariana, where soil micro-organisms accumulate N during the decomposition process, such as in the forest. The ratio of lignin in litter and the slow release of N reinforce the importance of the dominant tree Clusia hilariana as a potential key species for organic matter turnover. The accumulation of organic matter under the Clusia formation vegetation may be determinant for the humus richness of some bodies of water in the restinga, demonstrating the importance of this species to the ecosystem.

Resumo: Restingas são terraços arenosos dispostos ao longo da costa brasileira. Dois tipos de vegetação são muito comuns nas restingas do sudeste brasileiro, formações Clusia e formação florestal sazonalmente seca. A produção de serapilheira e o turnover de nutrientes (C e N) foram estudados comparativamente na formação florestal e na formação aberta de Clusia, em moitas de vegetação com e sem Clusia hilariana. Os resultados mostraram que a decomposição é muito lenta na formação de Clusia levando a acumulação de C no solo. A ação microbiana e da fauna do solo também é mais lenta nessa formação em comparação com a formação florestal; moitas sem Clusia hilariana apresentaram condições intermediárias com relação a perda de carbono total. A liberação de nitrogênio também é menor em moitas sem C. hilariana, onde os microrganismos do solo acumulam o N durante o processo de decomposição, como na floresta. A proporção de lignina na serapilheira e a liberação lenta de N reforçaram a importância da espécie dominante Clusia hilariana como uma espécie chave para o turnover da matéria orgânica do ecossistema. Por fim o acúmulo de altos teores orgânicos sob a vegetação da formação de Clusia pode ser o fator responsável pela riqueza de húmus de alguns corpos de água na restinga, demostrando a importância desta espécie para o ecossistema.

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Resumen Los manglares se distribuyen a lo largo de gradientes topográficos en zonas costeras, donde las variaciones en salinidad y períodos de inundación influyen en la composición y productividad primaria. En este estudio se evaluaron los atributos estructurales y producción de hojarasca de los manglares de la Laguna Mecoacán, Golfo de México. En seis sitios de monitoreo se determinó durante la segunda semana de julio 2014, la composición florística, el diámetro a la altura del pecho (DAP), altura, densidad del mangle adulto, juveniles, reclutas y plántulas. Además, se calcularon el área basal, índice de valor de importancia (IVI) y cobertura. Se tomaron muestras mensuales (noviembre 2014 a octubre 2015) de producción de hojarasca de las especies de mangle mediante trampas de captura, mientras que los parámetros físico-químicos de agua superficial, intersticial y subterránea fueron determinados mediante piezómetros. Los sitios de estudio en la Laguna Mecoacan se clasificaron en dos tipos fisonómicos: Borde (Boca, Aspoquero, Arrastradero y Pajaral) y cuenca (Cerros y Mojarrero). La densidad promedio del manglar fue de 2 870 árboles. ha-1. El área basal más alta se encontró en Pajaral (41.7 m-2. ha). Avicennia germinans (L.) Stearn presentó los valores más altos de IVI en todos los sitios. Se registró una cobertura media de 17.5 m2. Las especies mostraron zonación con los niveles de salinidad de agua intersticial; A. germinans con mayor densidad en áreas de alta salinidad (hipersalinas), mientras Laguncularia racemosa (L.) Gaertn y Rhizophora mangle L. en áreas de menor salinidad. La producción de hojarasca fue de 5.15 ton. ha-1. año-1, mostró una correlación positiva con la precipitación y alta correlación negativa con los niveles de salinidad y ORP intersticial y subterránea. Los resultados indican que la variabilidad en la composición, la estructura y la producción de hojarasca en la Laguna Mecoacán está determinada localmente por la capacidad de adaptación a las condiciones ambientales (precipitación, salinidad, potencial redox) de las especies presentes. Se recomienda establecer los sitios como parcelas permanentes de monitoreo y estimar la biomasa en pie y debajo del suelo para entender mejor la dinámica de nutrientes como una de las principales fuentes de energía in situ y exportado a zonas adyacentes.

Abstract Mangrove forests are distributed along the topographical gradients of coastal areas, where variations in salinity and flooding influence the composition and primary production of these forests. This study evaluated the structural attributes and production of leaf litter of mangrove species in Mecoacán Lagoon. We established six monitoring sites and studied the floristic composition, diameter at breast height (DBH), and density of adult, juvenile and recruited trees, as well as seedling density; additionally, the basal area, importance value index (IVI), and coverage were also calculated. Monthly samples (from November 2014 to October 2015) of the leaf litter production of different mangrove species, were collected using litter traps, and the physicalchemical parameters of surface, interstitial, and subterranean water were determined using piezometers. The study sites were classified into two physiognomic types: fringe (Boca, Aspoquero, Arrastradero, and Pajaral) and basin (Cerros and Mojarrero). The average density of mangrove trees was 2 870 trees. ha-1. The highest basal area was found in Pajaral (41.7 m2. ha-1). Avicennia germinans presented the highest IVI value in all sites. An average coverage of 17.5 m2 was recorded. The species were zoned with respect to interstitial salinity levels. A. germinans had a greater density in areas with high salinity (hypersaline) and Laguncularia racemosa and Rhizophora mangle in areas of lower salinity. The leaf litter production was 5.15 ton. ha-1. year-1 and showed a positive correlation with rainfall and a highly negative correlation with salinity level as well as with interstitial and subterranean oxidation redox potential (ORP). The results indicated that variability in the composition, structure, and production of leaf litter in Laguna Mecoacán is locally determined by the species capacity to adapt to environmental conditions (rainfall, salinity, redox potential). Several recommendations include the establishment of the sites evaluated in this study, as permanent monitoring areas and to estimate the above and belowground biomass, in order to understand the nutrient dynamics, as mangroves provide sources of energy both in situ and that may be exported to neighboring areas.

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Mercury (Hg) concentrations in tropical forest soils and litter are up to 10 times higher than those from temperate and boreal forests. The majority of Hg that has been stored in tropical soils, as the forest is left intact, could be trapped in deeper layers of soil and only small quantities are exported to water bodies. The quantitative approach to the Hg cycle in tropical forests is uncommon; the South America Atlantic Forest indeed is a hotspot for species conservation and also seems to be for the Hg's cycle. This study reports on a biannual dynamics of Hg through different species assemblage of different successional stages in this biome, based on 24 litter traps used to collect litterfall from 3 different successional stages under a rainforest located at Brazilian Southeast. The mean Hg litterfall flux obtained was 6.1 ± 0.15 µg ha-1 yr-1, while the mean Hg concentration in litter was 57 ± 16 ng g-1 and the accumulation of Hg via litterfall flux was 34.6 ± 1.2 µg m-2 yr-1. These inventories are close to those found for tropical areas in the Amazon, but they were lower than those assessed for Atlantic Forest biome studies. These low concentrations are related to the remoteness of the area from pollution sources and probably to the climatic limitation, due to the altitude effects over the forest's eco-physiology. The mercury fluxes found in each different successional stage, correlated with time variations of global radiation, suggesting a mandatory role of the forest primary production over Hg deposition to the soil.

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ResumenLa laguna de Barra de Navidad es un humedal costero de importancia internacional (sitio RAMSAR) y está incluida entre los 81 sitios prioritarios de manglar de México. Una de las características de mayor valor de la laguna, es la presencia de bosques de mangle en buen estado de conservación. El objetivo de nuestro trabajo, fue medir la producción de hojarasca del manglar y los factores ambientales que pueden influir en su dinámica.El manglar fue dividido en siete zonas y las recolectas de hojarasca se realizaron mensualmente entre noviembre 2011 y octubre 2012, mediante recolectores cuadrados de 0.25 m2 construidos con malla de mosquitero (1 mm) y colocados a 1.3 m del suelo. De forma simultánea, se midieron varias variables abióticas en el agua intersticial recolectada en pozos permanentes en cada zona, mediante un Sistema Multi-Sonda, YSI-556-M. El valor total promedio de producción de hojarasca, según el área de cada zona, fue de 19.12 ± 1.23 gPS/m2.mes (2.29 t/ha.año). Esta baja productividad se atribuye al clima seco de la región y a la poca amplitud de las mareas. Avicennia germinans y Laguncularia racemosa produjeron poco más del 80 % de toda la hojarasca, mientras que Rhizophora mangle sólo contribuyó con el 16 % y Conocarpus erectus< 4%. Existe una correlación significativa entre las variables abióticas del sustrato (principalmente la salinidad y la profundidad del agua intersticial) y la cantidad de hojarasca producida. Se concluye que, existen variaciones espaciales significativas en las variables abióticas del sustrato que se correlacionan con diferencias en la composición por especies del manglar y que, junto con las etapas de los ciclos vitales de esas especies, generan variaciones significativas en la cantidad y composición de la hojarasca producida. La investigación futura se enfocará en la cuantificación de las variaciones espaciales de la estructura del bosque y su relación con la producción de hojarasca.

AbstractBarra de Navidad lagoon is a coastal wetland of international importance (Ramsar site) and it is included among the 81 Mexican mangrove priority sites. One of the most valued characteristics of this lagoon is the presence of mangrove forest in a good conservation state. The goal of our research was the measurement of mangrove litter production and environmental factors influencing its dynamics. The mangrove area was divided into seven zones and litterfall was monthly sampled from November 2011 to October 2012 using 0.25 m2 square collectors made with mosquito mesh (1 mm) and positioned at 1.3 m above the ground. Abiotic variables of the interstitial water were measured simultaneously at each zone in permanent plots using a multi-parameter probe, YSI-556-M. Total mean value of litterfall production, weighted by zone surface, was 19.12 ± 1.23 gPS/m2.mo (2.29 t/ha.year). This low productivity is a consequence of the region's dry climate and low tide range. The species Avicennia germinans and Laguncularia racemosa produced more than 80 % of total litterfall, while Rhizophora mangle contributed only 16 % and Conocarpus erectus < 4 %. A significant correlation between litterfall production and abiotic variables was found (e.g. salinity and interstitial water depth). We concluded that there are significant spatial variations in soil abiotic variables which are correlated with differences in mangrove species composition, and produce, together with the life cycles stages of those species, significant variations in the quantity and composition of litterfall. Future research will be focused on quantifying spatial variations in forest structure and their relationship with litterfall production.

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The objective of this work was to assess the flux of atmospheric mercury transferred to the soil of the Amazonian rainforest by litterfall. Calculations were based on a large survey of published and unpublished data on litterfall and Hg concentrations in litterfall samples from the Amazonian region. Litterfall based on 65 sites located in the Amazon rainforest averaged 8.15 ± 2.25 Mg ha(-1) y(-1). Average Hg concentrations were calculated from nine datasets for fresh tree leaves and ten datasets for litter, and a median concentration of 60.5 ng Hg g(-1) was considered for Hg deposition in litterfall, which averaged 49 ± 14 µg m(-2) yr(-1). This value was used to estimate that in the Amazonian rainforest, litterfall would be responsible for the annual removing of 268 ± 77 Mg of Hg, approximately 8% of the total atmospheric Hg deposition to land. The impact of the Amazon deforestation on the Hg biogeochemical cycle is also discussed.

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Em ecossistemas florestais, o aporte e decomposição da serapilheira constituem o principal meio de transferência de nutrientes para o solo, sendo de grande importância para a sustentabilidade desses sistemas. Contudo, ainda são incipientes os estudos sobre a influência de estágios de sucessão na dinâmica da ciclagem de nutrientes em florestas secundárias, principalmente as localizadas em áreas de relevo movimentado, onde concentram-se grande parte dos fragmentos da Mata Atlântica na região sudeste do Brasil. Este trabalho teve como objetivo estudar a ciclagem de nutrientes em diferentes estágios de sucessão de uma Floresta Estacional Semidecidual Submontana, por meio da estimativa da deposição mensal e anual de serapilheira, do aporte de nutrientes e da taxa de decomposição do material foliar. Foram selecionadas três áreas com diferentes estádios sucessionais, localizadas em Pinheiral, RJ: floresta em estádio inicial (FEI), floresta em estádio médio (FEM) e floresta em estádio avançado (FEA). A produção de serapilheira foi avaliada mensalmente durante um ano (abril/2009 a março/2010) por meio de coletores cônicos de 0,21m2. A serapilheira foi seca, estratificada nas frações folhas, ramos, materiais reprodutivos e outras (frações não identificáveis), e pesada. Foram determinados os teores dos macronutrientes N, P, K, Ca e Mg para a serapilheira produzida. A decomposição do material foliar foi avaliada durante 120 dias, utilizando-se sacolas de decomposição. A deposição anual de serapilheira foi estimada em 7,47 Mg ha-1 na FEI; 8,96 Mg ha-1 na FEM e 14,7 Mg ha-1 na FEA, com a fração foliar representando, respectivamente, 86,4%, 80,7% e 66,1% do total aportado. Os teores e conteúdos de nutrientes, de maneira geral, foram menores na FEI, intermediários na FEM e maiores na FEA. A serapilheira se mostrou como uma importante via de transferência de N e Ca para o solo, destacando-se o N na FEA e o Ca na FEM e FEI. O tempo de meia vida para a FEA foi de 151 dias, seguido pela FEM (217 dias) e FEI (315 dias), observando-se na FEA maiores taxas de decomposição durante todo o período do estudo. Os resultados desse estudo evidenciaram que a idade sucessional afetou a quantidade total de nutrientes produzidos via serapilheira, função da complexidade estrutural em termos de aumento de riqueza de espécies vegetais e área basal. Desta forma, é possível supor que, desde que existam condições favoráveis tais como fontes de propágulos e dispersores, a sucessão florestal secundária, em áreas de relevo acidentado e com solos de baixa fertilidade natural, condicionará a formação de uma floresta nutricionalmente sustentável.

In forest ecosystems, the contribution and decomposition of litterfall are the primary means of transferring nutrients to the soil, being of great importance for the sustainability of these systems. However, studies about the influence of succesional stages in the dynamics of nutrient cycling in secondary forests are scarce, especially those located in relief irregular, where are concentrated much of the Atlantic Forest fragments in southeastern Brazil. This work aimed to study the cycling of nutrients in different successional stages of submontane semideciduous seasonal forest, through of monthly and annual litterfall production, by nutrient availability and the rate of decomposition of leaf material. We studied three areas with different successional stages, located in Pinheiral, RJ: forest in initial stage (FIS), forest in intermediate stage (FINS) and forest in advanced stage (FAS). The litter production was evaluated monthly for one year (April/2009 to March/2010) through conical collector 0,21m2. The litter collected was dried and stratified into leaves, branches, and other reproductive materials (fractions unidentifiable) and weighed. Subsequently, the material was homogenized and N, P, K, Ca and Mg concentrations were determined . The decomposition of leaf material was evaluated for 120 days using litter bags. It was found annual litter of 7.47 Mg ha-1 in FIS, 8.96 Mg ha-1 in FINS and 14.7 Mg ha-1 in FAS, with the leaf fraction representing, respectively, 86.4%, 80.7% and 66.1% of the total contributed. Concentration and content of nutrients, in general, were less in FIS, intermediate in FINS and higher in FAS. The litter was shown to be an important route of transfer of N and Ca to the soil, especially N in FAS and Ca in FINS and FEI. The half-life in FAS was 151 days, followed FINS (217 days) and FIS (315 days), observing the FAS greater loss of material throughout the study period. Ours results showed that the successional age affected the total amount of nutrients produced via litter, according to the structural complexity in terms of increase of plant species richness and basal area. Thereby, one can expect that, provided there are favorable conditions such as sources of propagules and dispersers, secondary forest succession in areas of relief irregular and with low fertility soils, condition the formation of a nutritionally sustainable forest.

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The study of litter decomposition and nutrient cycling is essential to know native forests structure and functioning. Mathematical models can help to understand the local and temporal litter fall variations and their environmental variables relationships. The objective of this study was test the adequacy of mathematical models for leaf litter decomposition in the Atlantic Forest in southeastern Brazil. We study four native forest sites in Parque Estadual do Rio Doce, a Biosphere Reserve of the Atlantic, which were installed 200 bags of litter decomposing with 20×20 cm nylon screen of 2 mm, with 10 grams of litter. Monthly from 09/2007 to 04/2009, 10 litterbags were removed for determination of the mass loss. We compared 3 nonlinear models: 1 – Olson Exponential Model (1963), which considers the constant K, 2 – Model proposed by Fountain and Schowalter (2004), 3 – Model proposed by Coelho and Borges (2005), which considers the variable K through QMR, SQR, SQTC, DMA and Test F. The Fountain and Schowalter (2004) model was inappropriate for this study by overestimating decomposition rate. The decay curve analysis showed that the model with the variable K was more appropriate, although the values of QMR and DMA revealed no significant difference (p> 0.05) between the models. The analysis showed a better adjustment of DMA using K variable, reinforced by the values of the adjustment coefficient (R2). However, convergence problems were observed in this model for estimate study areas outliers, which did not occur with K constant model. This problem can be related to the non-linear fit of mass/time values to K variable generated. The model with K constant shown to be adequate to describe curve decomposition for separately areas and best adjustability without convergence problems. The results demonstrated the adequacy of Olson model to estimate tropical forest litter decomposition. Although use of reduced number of parameters equaling the steps of the decomposition process, no difficulties of convergence were observed in Olson model. So, this model can be used to describe decomposition curves in different types of environments, estimating K appropriately.

O estudo da ciclagem de nutrientes através da decomposição de serapilheira é essencial para conhecer a estrutura e funcionamento das florestas tropicais nativas. Em decorrência da sua dependência de variáveis ambientais, o uso de modelos matemáticos pode ajudar a compreender as variações locais e temporais da decomposição do folhedo. O objetivo deste estudo foi testar a adequação dos modelos matemáticos para avaliar a dinâmica da decomposição da serapilheira em um mosaico de Floresta Tropical Atlântica no sudeste do Brasil. O estudo foi realizado em quatro remanescentes de mata nativa no Parque Estadual do Rio Doce, parte da Reserva da Biosfera da Mata Atlântica, onde se instalou 200 bolsas decompositoras feitas de tela de nylon 20×20 cm de 2 mm, com 10 gramas de serapilheira recém-colhida. Mensalmente, de 09/2007 a 04/2009, 10 litterbags foram removidos por área, para limpeza, secagem e posterior determinação da perda de massa. Comparamos três modelos não lineares: 1 – Modelo exponencial de Olson (1963), que considera a constante K, 2 – Modelo proposto por Fountain and Schowalter (2004), 3 – Modelo proposto por Coelho e Borges (2005), que considera a variável K através do QMR, SQR, SQTC, DMA e Teste F. O modelo de Fountain and Schowalter (2004) mostrou-se inadequado por superestimar a taxa de decomposição. A análise mostrou que a curva de decaimento do modelo com K variável foi o mais adequado, embora os valores de QMR e DMA não revelaram nenhuma diferença significativa (p> 0,05) entre os modelos. A análise mostrou um melhor ajustamento do DMA usando a variável K, que foi reforçada com os valores do coeficiente de calibração (R2). No entanto, problemas de convergência foram observados neste modelo, que não foi capaz de estimar com precisão os valores “outliers” para cada área de estudo, o que não ocorreu com o modelo de Olson. Entretanto, parece que os problemas de não convergência podem estar relacionados ao ajuste não linear dos dados de massa por tempo, utilizados para gerar o modelo. Quando submetido ao ensaio de parâmetros iguais, o modelo com K constante (Olson, 1963) mostrou-se adequado para descrever a curva de decomposição por áreas de estudo separadamente, de modo que o seu melhor ajuste não compensou os problemas de convergência encontrados. Os resultados demonstraram a aptidão do modelo proposto por Olson (1963) para estimar a decomposição de serapilheira de florestas tropicais, mesmo que eventualmente não detecte diferenças entre as etapas do processo de decomposição. Este modelo não apresenta dificuldades de convergência, permitindo descrever as curvas de decomposição em diferentes tipos de ambientes, estimando os valores de K mais apropriadamente e com mais acurácia.

Assuntos

RESUMO

The study of litter decomposition and nutrient cycling is essential to know native forests structure and functioning. Mathematical models can help to understand the local and temporal litter fall variations and their environmental variables relationships. The objective of this study was test the adequacy of mathematical models for leaf litter decomposition in the Atlantic Forest in southeastern Brazil. We study four native forest sites in Parque Estadual do Rio Doce, a Biosphere Reserve of the Atlantic, which were installed 200 bags of litter decomposing with 20×20 cm nylon screen of 2 mm, with 10 grams of litter. Monthly from 09/2007 to 04/2009, 10 litterbags were removed for determination of the mass loss. We compared 3 nonlinear models: 1 Olson Exponential Model (1963), which considers the constant K, 2 Model proposed by Fountain and Schowalter (2004), 3 Model proposed by Coelho and Borges (2005), which considers the variable K through QMR, SQR, SQTC, DMA and Test F. The Fountain and Schowalter (2004) model was inappropriate for this study by overestimating decomposition rate. The decay curve analysis showed that the model with the variable K was more appropriate, although the values of QMR and DMA revealed no significant difference (p> 0.05) between the models. The analysis showed a better adjustment of DMA using K variable, reinforced by the values of the adjustment coefficient (R2). However, convergence problems were observed in this model for estimate study areas outliers, which did not occur with K constant model. This problem can be related to the non-linear fit of mass/time values to K variable generated. The model with K constant shown to be adequate to describe curve decomposition for separately areas and best adjustability without convergence problems. The results demonstrated the adequacy of Olson model to estimate tropical forest litter decomposition. Although use of reduced number of parameters equaling the steps of the decomposition process, no difficulties of convergence were observed in Olson model. So, this model can be used to describe decomposition curves in different types of environments, estimating K appropriately.(AU)

O estudo da ciclagem de nutrientes através da decomposição de serapilheira é essencial para conhecer a estrutura e funcionamento das florestas tropicais nativas. Em decorrência da sua dependência de variáveis ambientais, o uso de modelos matemáticos pode ajudar a compreender as variações locais e temporais da decomposição do folhedo. O objetivo deste estudo foi testar a adequação dos modelos matemáticos para avaliar a dinâmica da decomposição da serapilheira em um mosaico de Floresta Tropical Atlântica no sudeste do Brasil. O estudo foi realizado em quatro remanescentes de mata nativa no Parque Estadual do Rio Doce, parte da Reserva da Biosfera da Mata Atlântica, onde se instalou 200 bolsas decompositoras feitas de tela de nylon 20×20 cm de 2 mm, com 10 gramas de serapilheira recém-colhida. Mensalmente, de 09/2007 a 04/2009, 10 litterbags foram removidos por área, para limpeza, secagem e posterior determinação da perda de massa. Comparamos três modelos não lineares: 1 Modelo exponencial de Olson (1963), que considera a constante K, 2 Modelo proposto por Fountain and Schowalter (2004), 3 Modelo proposto por Coelho e Borges (2005), que considera a variável K através do QMR, SQR, SQTC, DMA e Teste F. O modelo de Fountain and Schowalter (2004) mostrou-se inadequado por superestimar a taxa de decomposição. A análise mostrou que a curva de decaimento do modelo com K variável foi o mais adequado, embora os valores de QMR e DMA não revelaram nenhuma diferença significativa (p> 0,05) entre os modelos. A análise mostrou um melhor ajustamento do DMA usando a variável K, que foi reforçada com os valores do coeficiente de calibração (R2). No entanto, problemas de convergência foram observados neste modelo, que não foi capaz de estimar com precisão os valores “outliers” para cada área de estudo, o que não ocorreu com o modelo de Olson. Entretanto, parece que os problemas de não convergência podem estar relacionados ao ajuste não linear dos dados de massa por tempo, utilizados para gerar o modelo. Quando submetido ao ensaio de parâmetros iguais, o modelo com K constante (Olson, 1963) mostrou-se adequado para descrever a curva de decomposição por áreas de estudo separadamente, de modo que o seu melhor ajuste não compensou os problemas de convergência encontrados. Os resultados demonstraram a aptidão do modelo proposto por Olson (1963) para estimar a decomposição de serapilheira de florestas tropicais, mesmo que eventualmente não detecte diferenças entre as etapas do processo de decomposição. Este modelo não apresenta dificuldades de convergência, permitindo descrever as curvas de decomposição em diferentes tipos de ambientes, estimando os valores de K mais apropriadamente e com mais acurácia.(AU)

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RESUMO

Azadirachta indica is a tree species which use is steadily increasing for restoration of tropical and subtropical arid and degraded lands throughout the world. The objective of this research study was to evaluate the potential of these plantations as an active restoration model for the recovery of soils under desertification in arid lands of Colombia. Litter traps and litter-bags were installed in twenty 250m² plots. Green leaves and soil samples inside and outside this species plantations were taken, and their elemental concentrations were determined. Litterfall, leaf litter decomposition and foliar nutrient resorption were moni- tored for one year. The annual contributions of organic material, such as fine litterfall, represented 557.54kg/ha, a third of which was A. indica leaves. The greatest potential returns of nutrients per foliar litterfall were from Ca (4.6kg/ha) and N (2.4kg/ha), and the smallest potential returns came from P (0.06kg/ha). A total of 68% of the foliar material deposited in litter-bags disappeared after one year. The greatest release of nutrients was that of K (100%), and the least was that of N (40%). P was the most limiting nutrient, with low edaphic availability and high nutrient use efficiency from Vitousek´s index (IEV=3176) and foliar nutrient resorption (35%). Despite these plantations are young, and that they have not had forestry management practices, as an active restoration model, they have revitalized the biogeochemical cycle, positively modifying the edaphic parameters according to the increases in organic material, P and K of 72%, 31% and 61%, respectively. Furthermore, they improved the stability of aggregates and the microbe respiration rates. The forest plantation model with exotic species has been opposed by different sectors; however, it has been acknowledged that these projects derive many benefits for the restoration of biodiversity and ecosystemic functions. The conditions of severe land degradation demand the initial use of species, such as A. indica, that can adapt quickly and successfully, and progressively reestablish the biogeochemical cycle.

Azadirachta indica A. Juss (Nim) ha sido ampliamente empleada en procedimientos de restauración, por lo tanto se evaluó el potencial de sus plantaciones para restaurar tierras secas degradadas por sobrepastoreo, vía reactivación del ciclo biogeoquímico. En 20 parcelas de 250m², se instalaron trampas de hojarasca y litter-bags. Se tomaron muestras de hojas maduras y de suelos dentro y fuera de las plantaciones, y se determinaron sus contenidos elementales. Fueron monitoreados la caída de hojarasca, la descomposición de hojarasca y la reabsorción de nutrientes foliares durante un año. Los aportes anuales de hojarasca fina representaron 557.54kg/ha (33% hojas de Nim). Los mayores retornos potenciales de nutrientes vía foliar fue- ron de Ca (4.6kg/ha) y N (2.4kg/ha) y los menores de P (0.06kg/ha). El 68% del material se descompuso tras un año. La mayor liberación de nutrientes fue de K (100%) y la menor de N (40%). El P fue el nutriente más limitante, con baja disponibilidad edáfica y alta eficiencia en su uso según el Índice de Vitousek (IEV=3 176) y la reabsorción foliar (35%). Estas plantaciones juveniles demostraron efectividad en la reactivación del ciclo biogeoquímico, que mejoraron parámetros edáficos, según incrementos de materia orgánica, P y K; 72%, 31% y 61%, respectiva- mente. Además mejoraron la estabilidad de agregados y las tasas de respiración microbiana.

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RESUMO

Talitroides topitotum (Amphipoda) was introduced in Brazil by silviculture activities. Currently the species is distributed in the states of Paraná, Rio de Janeiro and São Paulo. This paper describes the species occurrence in the state of Espírito Santo. The objective of this study was to determine the interference of the edge effect on community structure of macroinvertebrates associated with leaf litter, where a T. topitotum female specimen was observed in coffee cultivations in March 2008.(AU)

Talitroides topitotum (Amphipoda) foi introduzido no Brasil pelas atividades de silvicultura. Atualmente a espécie está distribuída nos Estados do Paraná, Rio de Janeiro e São Paulo. Este trabalho descreve a ocorrência desta espécie no Estado do Espírito Santo. O objetivo deste estudo foi determinar a interferência do efeito de borda na estruturada comunidade de macroinvertebrados associados ao folhiço, onde um espécime fêmea de T. topitotum foi observado em cultivo de café em março de 2008.(AU)

Assuntos

RESUMO

Talitroides topitotum (Amphipoda) was introduced in Brazil by silviculture activities. Currently the species is distributed in the states of Paraná, Rio de Janeiro and São Paulo. This paper describes the species' occurrence in the state of Espírito Santo. The objective of this study was to determine the interference of the edge effect on community structure of macroinvertebrates associated with leaf litter, where a T. topitotum female specimen was observed in coffee cultivations in March 2008.

Talitroides topitotum (Amphipoda) foi introduzido no Brasil pelas atividades de silvicultura. Atualmente a espécie está distribuída nos Estados do Paraná, Rio de Janeiro e São Paulo. Este trabalho descreve a ocorrência desta espécie no Estado do Espírito Santo. O objetivo deste estudo foi determinar a interferência do efeito de borda na estruturada comunidade de macroinvertebrados associados ao folhiço, onde um espécime fêmea de T. topitotum foi observado em cultivo de café em março de 2008.

Assuntos