Neotropical woodlice (isopoda) colonizing leaf-litter of pioneer plants in a coal residue disposal environment

The irregular disposal of coal combustion residues has adverse impacts on terrestrial ecosystems. Pioneer plants and soil invertebrates play an important role in the recovery of these areas. The goal of this study was to investigate the colonization patterns of terrestrial isopods (Oniscidea) in leaf litter of three spontaneous pioneer plants (grass - Poaceae, shrub - Euphorbiaceae, tree - Anarcadiaceae) at sites used for fly ash or boiler slag disposal. The experiment consisted of eight blocks (four per disposal site) of 12 litter bags each (four per plant species) that were randomly removed after 6, 35, 70 or 140 days of field exposure. Three isopod species were found in the litter bags: Atlantoscia floridana (van Name, 1940) (Philosciidae; n = 116), Benthana taeniata Araujo & Buckup, 1994 (Philosciidae; n = 817) and Balloniscus sellowii (Brandt, 1833) (Balloniscidae; n = 48). The isopods colonized the three leaf-litter species equally during the exposure period. However, the pattern of leaf-litter colonization by these species suggests a conflict of objectives between high quality food and shelter availability. The occurrence of A. floridana and the abundance and fecundity of B. taeniata were influenced by the residue type, indicating that the isopods have different degrees of tolerance to the characteristics of the studied sites. Considering that terrestrial isopods are abundant detritivores and stimulate the humus-forming processes, it is suggested that they could have an indirect influence on the soil restoration of this area.

Decomposition of the rubber tree Hevea brasiliensis litter at two depths

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

LITTER DEVOLUTION AND DECOMPOSITION IN A PERIODICALLY FLOODED FOREST IN RESTINGA DA MARAMBAIA, RIO DE JANEIRO

Restinga (sandbank) areas are fragile environments, which have been subjected to anthropogenic pressures since the country colonization. So that mitigate actions can be taken, it must be developed studies to better understand the ecological processes in these environments. Thus, this study aims to quantify litter and nutrients devolution and litter decomposition in a periodically flooded forest in 'Restinga da Marambaia', Rio de Janeiro. In the study area 10 conic collectors and 30 litter bags were installed. The annual litter devolution was 7.64 Mg.ha(-1), and September was the highest contribution month. Nitrogen was the element returned to the soil to a higher amount (71.9 kg ha(-1) yr(-1)), followed by potassium (41.1 kg ha(-1) yr(-1)). Litter decomposition rate 0.0015 g g(-1) day(-1) and the half-life were 462 days. Potassium was the element that showed the highest losses in comparison to the others. Cellulose appeared as a major participant in the structure of leaf litter, followed by lignin, the latter being associated with the leathery texture of the leaves in this formation.

Liberação de macronutrientes das palhadas de milheto solteiro e consorciado com feijão-de-porco sob cultivo de feijão

A ciclagem de nutrientes está relacionada com a capacidade de absorção das diferentes espécies de plantas de cobertura. Já as velocidades de decomposição e liberação de nutrientes, das palhadas produzidas pelas mesmas, têm com fator principal a relação C/N, com diferença marcante entre gramíneas e leguminosas. Neste sentido, o objetivo deste trabalho foi avaliar a produção de matéria seca, teor, acúmulo, decomposição e liberação de macronutrientes da palhada de milheto (Pennisetum typhoides (Burm.) Stapf) solteiro e consorciado com feijão-de-porco (Canavalia ensiformes (L.) DC.), em ambiente de campo, sob a cultura do feijoeiro, semeada em agosto de 2005 (inverno/primavera), em um Latossolo Vermelho distroférrico típico. A liberação de nutrientes foi determinada por meio da distribuição de bolsas confeccionadas com telas de náilon, com malha de 1 mm, de dimensões de 0,2 x 0,2 m, preenchidas com quantidades de palha proporcionais à área da bolsa. O delineamento utilizado foi o de blocos casualizados, com quatro repetições, em esquema de parcelas subdivididas. As parcelas foram constituídas pelos dois tipos de palhadas (milheto e milheto + feijão-de-porco), e as subparcelas, pelas épocas de avaliação ao longo do cultivo do feijoeiro (0, 8, 16, 24, 40, 56 e 72 dias após o manejo das plantas de cobertura). Os resíduos coletados foram secos em estufa de circulação forçada de ar, a 65 ºC, até atingirem peso constante, para determinação da matéria seca remanescente, sendo posteriormente moídos e encaminhados para a determinação dos teores de macronutrientes. Com base nos teores e na matéria seca remanescente, foram calculadas as quantidades remanescentes dos macronutrientes, sendo elas expressas em percentagem do valor inicial. Os valores foram ajustados a modelos não lineares, escolhendo-se aqueles com melhor ajuste em cada situação. A palhada de milheto + feijão-deporco apresentou maior quantidade de matéria seca e maiores teores de N e Ca, ciclando maior quantidade de todos os macronutrientes. A palhada de milheto + feijão-de-porco apresentou maiores velocidades de decomposição e liberação de N, Ca e Mg.

Acúmulo de macronutrientes e decomposição da palhada de braquiárias em razão da adubação nitrogenada durante e após o consórcio com a cultura do milho

Em regiões de clima tropical, as principais limitações na manutenção de palhada na superfície do solo são a dificuldade de sua implantação e as suas elevadas taxas de decomposição. Visando identificar o potencial produtivo dos capins xaraés e ruziziensis, bem como a posterior formação de palhada para continuidade do sistema plantio direto, avaliou-se a produtividade de massa seca, a relação lignina/N total, o acúmulo de macronutrientes e a decomposição da palhada em duas safras agrícolas. Os tratamentos foram constituídos por duas espécies de braquiária (Brachiaria brizantha cv. Xaraés e Brachiaria ruziziensis), implantadas em consórcio com a cultura do milho e adubadas com as mesmas doses de N (0, 50, 100, 150 e 200 kg ha-1), durante e após o consórcio com a cultura do milho. O tempo de decomposição da palhada durante o período de 120 dias foi avaliado pelo método das sacolas de decomposição (litter bags). A adubação nitrogenada não influenciou a produtividade de massa seca dos capins xaraés e ruziziensis, a relação lignina/N total e a quantidade de palhada depositada sobre a superfície do solo após o consórcio com milho, porém elevou os acúmulos de N, K, Mg e S. Os capins xaraés e ruziziensis apresentaram potencial de produção de palhada acima de 4.000 kg ha-1 na entressafra, com a manutenção de 15 a 60 % dessa quantidade aos 120 dias após o manejo.

Biomass decomposition and nutrient release from black oat and hairy vetch residues deposited in a vineyard

A significant quantity of nutrients in vineyards may return to the soil each year through decomposition of residues from cover plants. This study aimed to evaluate biomass decomposition and nutrient release from residues of black oats and hairy vetch deposited in the vines rows, with and without plastic shelter, and in the between-row areas throughout the vegetative and productive cycle of the plants. The study was conducted in a commercial vineyard in Bento Gonçalves, RS, Brazil, from October 2008 to February 2009. Black oat (Avena strigosa) and hairy vetch (Vicia villosa) residues were collected, subjected to chemical (C, N, P, K, Ca, and Mg) and biochemical (cellulose - Cel, hemicellulose - Hem, and lignin - Lig content) analyses, and placed in litter bags, which were deposited in vines rows without plastic shelter (VPRWS), in vines rows with plastic shelter (VPRS), and in the between-row areas (BR). We collected the residues at 0, 33, 58, 76, and 110 days after deposition of the litter bags, prepared the material, and subjected it to analysis of total N, P, K, Ca, and Mg content. The VPRS contained the largest quantities and percentages of dry matter and residual nutrients (except for Ca) in black oat residues from October to February, which coincides with the period from flowering up to grape harvest. This practice led to greater protection of the soil surface, avoiding surface runoff of the solution derived from between the rows, but it retarded nutrient cycling. The rate of biomass decomposition and nutrient release from hairy vetch residues from October to February was not affected by the position of deposition of the residues in the vineyard, which may especially be attributed to the lower values of the C/N and Lig/N ratios. Regardless of the type of residue, black oat or hairy vetch, the greatest decomposition and nutrient release mainly occurred up to 33 days after deposition of the residues on the soil surface, which coincided with the flowering of the grapevines, which is one of the phenological stages of greatest demand for nutrients.

Decomposition of Ruppia cirrhosa (Petagna) Grande in the sediment of a coastal lagoon

The decomposition process of Ruppia cirrhosa was studied in a Mediterranean coastal lagoon in the Delta of the River Ebro (NE Spain). Leaves and shoots of Ruppia were enclosed in 1 mm-mesh and 100 pm-mesh litter bags to ascertain the effect of detritivores, macroinvertebrates, and bacteria and fungi, respectively. Changes in biomass and carbon, and, nitrogen and phosphorus concentrations in the detritus were studied at the sediment-water interface and in the sediment. Significant differences in biomass decay were observed between the two bag types. Significant differences in decomposition were observed between the two experimental conditions studied using 100 pm-mesh bags. These differences were not significant when using the 1 mm-mesh bags. The carbon content in the detritus remained constant during the decomposition process. The percentage of nitrogen increased progressively from an initial 2.4 % to 3 %. The percentage of phosphorus decreased rapidly during the first two days of decomposition from an initial 0.26 % to 0.17 %. This loss is greater in the sediment than in the water column or at the sediment-water interface. From these results we deduce that the activity of microorganisms seems to be more important in the sediment than in the water-sediment interface, and that grazing by macroinvertebrates has less importance in the sediment than in the water column.

Decomposition of Arachis pintoi and Hyparrhenia rufa litters in monoculture and intercropped systems under lowland soil

Tropical grasslands under lowland soils are generally underutilized and the litter of forage legumes may be used to recover these degraded pastures. The objective of this work was to study the dynamics of litter decomposition of Arachis pintoi (pinto peanut), Hyparrhenia rufa (thatching grass) and a mixture of both species in a lowland soil. These treatments were analyzed in three areas: grass monoculture, legume monoculture and legume intercropped with the grass during the dry and wet seasons. Litter bags containing the legume, grass or a mixture of both species were incubated to estimate the decomposition rate and microorganism colonization. Decomposition constants (K) and litter half-lives (T1/2) were estimated by an exponential model whereas number of microorganisms in specific media were determined by plate dilution. The decomposition rate, release of nutrients and microorganisms number, especially bacteria, increased when pinto peanut was added to thatching grass, influenced by favorable lignin/N and C/N ratios in legume litter. When pinto peanut litter was incubated in the grass plots, 50% N and P was released within about 135 days in the dry season and in the wet season, the equivalent release occurred within 20 days. These results indicate that A. pintoi has a great potential for nutrient recycling via litter and can be used to recover degraded areas.

Proteção do solo por plantas de cobertura de ciclo hibernal na região Sul do Brasil

O objetivo deste trabalho foi avaliar o potencial de plantas de cobertura de ciclo hibernal na proteção do solo, na região Sudoeste do Paraná, em função da taxa de cobertura, da produção de matéria seca (MS), da relação C/N e da manutenção da MS remanescente dos resíduos vegetais na superfície do solo. Foram utilizados como cobertura do solo: aveia-preta (Avena strigosa), azevém (Lolium multiflorum), centeio (Secale cereale), tremoço-branco (Lupinus albus), ervilhaca comum (Vicia sativa), nabo forrageiro (Raphanus sativus) e consórcios entre aveia-preta + ervilhaca comum (A+E) e aveia-preta + ervilhaca comum + nabo forrageiro (A+E+N). O experimento foi avaliado durante os anos agrícolas 2010/2011 e 2011/2012. A decomposição das plantas de cobertura foi determinada com uso de bolsas de decomposição ("litter bags"). A aveia-preta e os consórcios proporcionaram maiores taxas de cobertura do solo aos primeiros 50 dias após a semeadura, com aporte de MS superior a 2.600 kg ha-1 na superfície do solo. O consórcio entre A+E+N apresentou relação C/N equilibrada e decomposição intermediária em relação ao cultivo solteiro, tendo promovido 1.045 kg ha-1 de palhada sobre o solo, 120 dias após seu manejo. Gramíneas puras e consórcios com gramíneas apresentam maior potencial de proteção do solo

Carbon and nitrogen cycling in an integrated soybean-beef cattle production system under different grazing intensities

Abstract:The objective of this work was to evaluate the effect of grazing intensity on the decomposition of cover crop pasture, dung, and soybean residues, as well as the C and N release rates from these residues in a long-term integrated soybean-beef cattle system under no-tillage. The experiment was initiated in 2001, with soybean cultivated in summer and black oat + Italian ryegrass in winter. The treatments consisted of four sward heights (10, 20, 30, and 40 cm), plus an ungrazed area, as the control. In 2009-2011, residues from pasture, dung, and soybean stems and leaves were placed in nylon-mesh litter bags and allowed to decompose for up to 258 days. With increasing grazing intensity, residual dry matter of the pasture decreased and that of dung increased. Pasture and dung lignin concentrations and C release rates were lower with moderate grazing intensity. C and N release rates from soybean residues are not affected by grazing intensity. The moderate grazing intensity produces higher quality residues, both for pasture and dung. Total C and N release is influenced by the greater residual dry matter produced when pastures were either lightly grazed or ungrazed.

Decomposition of Ruppia cirrhosa (Petagna) Grande in the sediment of a coastal lagoon

The decomposition process of Ruppia cirrhosa was studied in a Mediterranean coastal lagoon in the Delta of the River Ebro (NE Spain). Leaves and shoots of Ruppia were enclosed in 1 mm-mesh and 100 pm-mesh litter bags to ascertain the effect of detritivores, macroinvertebrates, and bacteria and fungi, respectively. Changes in biomass and carbon, and, nitrogen and phosphorus concentrations in the detritus were studied at the sediment-water interface and in the sediment. Significant differences in biomass decay were observed between the two bag types. Significant differences in decomposition were observed between the two experimental conditions studied using 100 pm-mesh bags. These differences were not significant when using the 1 mm-mesh bags. The carbon content in the detritus remained constant during the decomposition process. The percentage of nitrogen increased progressively from an initial 2.4 % to 3 %. The percentage of phosphorus decreased rapidly during the first two days of decomposition from an initial 0.26 % to 0.17 %. This loss is greater in the sediment than in the water column or at the sediment-water interface. From these results we deduce that the activity of microorganisms seems to be more important in the sediment than in the water-sediment interface, and that grazing by macroinvertebrates has less importance in the sediment than in the water column.

The effect of moisture on decomposition processes in the disturbed peatlands of the Wainfleet bog /

The purpose of this study was to determine the effect of increased soil moisture levels on the decomposition processes in a peat-extracted bog. Field experiments, in which soil moisture levels were manipulated, were conducted using 320 microcosms in the Wainfleet Bog from May 2002 to November 2004. Decomposition was measured using litter bags and monitoring the abundance of macro invertebrate decomposers known as Collembola. Litter bags containing wooden toothpicks (n=2240), filter paper (n=480) and Betula pendula leaves (n=40) were buried in the soil and removed at regular time intervals up to one year. The results of the litter bag studies demonstrated a significant reduction of the decomposition of toothpicks (p<0.001), filter paper (p<0.001), and Betula pendula leaves (p

Sequências de culturas em sistema de semeadura direta: II - decomposição e liberação de nutrientes na entressafra

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Aporte e decomposição de serapilheira em áreas de cerradão e mata mesofítica na Estação Ecológica de Pirapitinga - MG

This study aimed to quantify the litter and nutrients amount and to estimate the decomposition rate in areas of mesophytic forest and 'Cerradao' in the Ecological Station of Pirapitinga. To evaluate litter and nutrients devolution 10 conic litter traps were randomly distributed in an area 0.1 ha in each area of study, with monthly evaluations. The litter decomposition in the areas of study was evaluated by using litter bags. The total production of litter was 2.50 and 2.92 Mg ha(-1) yr(-1) for mesophytic forest and 'Cerradao' areas, respectively. The nutrients devolution importance order was nitrogen> potassium> phosphorus. The mesophytic forest showed more homogeneous distribution of litter fall over the year and higher values of total annual litter and nutrients, the highest values were observed at the dry season. The half-life decomposition of leaf litter was equivalent between areas, about 161 days in the mesophytic forest area and 173 in 'Cerradao' area.

The invertebrate colonization during decomposition of Eichhornia azurea kunth in a lateral lake in the mouth zone of Paranapanema River into Jurumirim Reservoir (São Paulo, Brazil)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)