ABSTRACT Adopting land-uses that contribute with a considerable litter input can affect the accumulation, protection, and bioavailability of organic carbon in the edaphic environment, compromising the different compartments of soil organic matter (SOM) and the associated benefits. Moreover, changes in seasons can influence the dynamic of SOM. Notably, the mechanisms involved in SOM stabilization and storage, particularly in agroforestry production areas, are still poorly explored. This study aimed to verify if the contents of soil organic carbon (SOC) and the physical fractions of the SOM are modified as a function of agroforestry systems implemented in the short term, and verify if seasonality can affect the compartmentalization of SOM in agrifood systems. Also, we tested if the carbon management index (CMI) is sensitive to detecting management practices quality across the unmanaged pasture, different agroforestry systems, and a reference area (forest). We measured soil physical properties, SOC content in bulk soil, particular organic carbon (POC), and mineral-associated organic carbon (MAOC) fractions at three different depths (0.00-0.05, 0.05-0.10, and 0.10-0.20 m) in response to the adoption of agroforestry systems. Our results show that after a short period of implementation of agroforestry systems, significant changes were observed in SOC contents and the physical fractions of SOM in the most superficial layers (0.00-0.05 and 0.05-0.10 m), with emphasis on the particulate fraction of SOM. We verified that the seasonality affected the SOC, POC, and MAOC contents. We also found that the CMI index was more sensitive and efficient in detecting changes arising from seasonality and the management practices involved. According to this index, it was possible to verify that the agroforestry system with the highest density of species for biomass production (AS3) has been accumulating more carbon in the soil. Therefore, this study provides relevant information regarding soil carbon management in agroforestry systems.

Abstract The study evaluated the ecology of soil invertebrate faunal communities in periodically flooded forest (CF) fragments and anthropic fields (AF) in the Atlantic Forest. The sampling occurred in the rainy and dry seasons using pitfall traps. We estimated the total activity, richness, diversity, and evenness as well as the activity of the taxonomic and functional groups. Total activity and richness varied as a function of seasonality. Entomobryomorpha, Poduromorpha, and Symphypleona were the most representative taxonomic groups. Enchytraeidae and Blattaria were exclusive to CF. Auchenorrhyncha, Chilopoda, Heteroptera, and Thysanoptera were exclusive to AF. The functional group of microphagous/saprophagous (M/S) showed the highest activity, independent of the environment and season. Greater dissimilarity was observed among the invertebrate fauna in AF when compared to CF. Periodically flooded areas favored groups from the saprophagous trophic guild, while AF areas favored predator and herbivore groups. Soil fauna present in forest environments presented less seasonal variability.

ABSTRACT Soil invertebrate fauna plays a major role in several environmental processes, and its absence can negatively impact ecosystem health. This study aimed to assess the recovery of epigeal and edaphic invertebrate faunal communities following an environmental disaster, with landslides, mudflow, and river floods, in sites under different management systems, the effects of cover crops on invertebrate fauna, and their relationship with soil physical and chemical properties in the mountainous region of Rio de Janeiro State, Brazil. The following sites were evaluated: CF, a site under conventional farming without any record of natural hazard events; LS, a site impacted by an intense landslide event that left the area buried by mudflow; RO1, a site affected by river overflow and treated with NPK fertilizer and poultry litter; RO2, a site affected by river overflow and subjected to liming and heavy fertilization with NPK; and RO3, a site affected by a less intense river overflow and subjected to fertilization with poultry litter and NPK fertilizer. At each site, epigeal and edaphic fauna were sampled using pitfall traps and a monolith sampler, respectively. Physical (soil temperature, moisture, aggregate stability, and density) and chemical (pH in water, Ca2+, Mg2+, Al3+, K+, P, cation-exchange capacity, and total organic carbon) properties were determined in the 0.00-0.05 and 0.00-0.10 m layers. The predominant epigeal faunal groups were Entomobryomorpha, Poduromorpha, Diptera, and Coleoptera; and the predominant edaphic faunal groups, Coleoptera and Oligochaeta. There was a positive correlation between Coleoptera larvae, Hymenoptera, and species richness with total organic carbon. Coleoptera larvae were positively associated with biogenic aggregate stability, whereas Coleoptera was positively associated with physicogenic aggregate stability. Oligochaeta showed a positive correlation with soil moisture. Cover crops favored the development of epigeal and edaphic faunal groups that enhance soil properties through organic matter fragmentation and decomposition, and structural engineering. The strong correlation between soil chemical, physical, and biological properties demonstrate the importance of monitoring these components to assess the recovery of disaster-affected areas.

RESUMO: O objetivo deste estudo foi avaliar o efeito da fitomassa de diferentes plantas de cobertura no desenvolvimento da comunidade da fauna epígea em área de cultivo orgânico de berinjela (Solanum melongena, L.). Foi adotado delineamento em blocos ao acaso, com quatro tratamentos de plantas de cobertura: braquiária, crotalária, milheto e coquetel (crotalária, braquiária e milheto), além de uma área de floresta secundária (FR). A fauna epígea avaliada por meio de armadilhas do tipo “pitfall traps” em dois períodos de coletas, aos 110 dias e aos 180 dias, após o corte das plantas de coberturas. Foram coletadas amostras de solo para análise de atributos físicos e químicos. Foram capturados 2032 indivíduos na primeira coleta e 3806 indivíduos na segunda coleta. Os maiores valores de riqueza na primeira coleta foram observados nas áreas milheto e coquetel. A análise de agrupamento mostrou similaridade dos grupos da fauna epígea entre o milheto e braquiária na primeira amostragem e entre o coquetel e crotalária na segunda amostragem. A co-inércia evidenciou covariância significativa entre a fauna epígea da segunda coleta e os atributos do solo. O manejo com plantas de coberturas influenciou de forma benéfica a atividade, riqueza e índices ecológicos, em ambos os períodos de amostragens. A associação positiva entre grupos da fauna e os atributos físicos e químicos mostram a eficiência das plantas de coberturas em cultivo orgânico na promoção de melhorias da qualidade do solo.

ABSTRACT: This study assessed the effect of cover crop biomass on the epigeal fauna of an organic eggplant (Solanum melongena L.) cropping system. A randomized block design was used, with four cover crop treatments: brachiaria, crotalaria, millet, and cocktail (brachiaria, crotalaria and millet). The epigeal faunal indices were determined at each plot. The epigeal fauna of a secondary forest site was also assessed for comparison. Epigeal individuals were collected using pitfall traps at two sampling periods (110 and 180 days after mowing cover crops). Soil samples were collected for determination of physical and chemic properties. 2032 individuals were captured in the first sampling and 3806 individuals in the second. The highest values of wealth in the first collection were observed in the millet and cocktail areas. Cluster analysis showed similarity of epigeal faunal groups between millet and brachiaria plots at the first sampling and between cocktail and crotalaria sites at the second sampling. Co-inertia analysis showed a significant covariance between epigeal fauna at the second sampling and soil properties. The cover crops management had a beneficial influence on the activity, wealth and ecological indexes, in both sampling periods. The positive association observed between epigeal faunal groups and soil physical and chemical properties demonstrates the efficiency of cover crops in improving soil quality in organic cropping systems.

RESUMO Avaliou-se a eficiência da aveia preta na recuperação da agregação do solo e quantificou-se os teores dos nutrientes nos agregados biogênicos e fisiogênicos em áreas de cultivo de Nova Friburgo, RJ. A paisagem foi estratificada nas secções: superior - com o emprego de aveia preta, adubada e outra não adubada; e inferior: com aveia preta adubada, outra com consórcio de aveia preta, nabo forrageiro e ervilhaca com adubação. Ambas as secções tinham área adjacente de floresta. Os agregados foram separados quanto às vias de formação quantificando-se a porcentagem de massa em cada via de formação. Foram analisados: estabilidade dos agregados, teores de nutrientes e conteúdo de carbono orgânico. Na parte superior, na área adubada verificou-se a maior porcentagem de agregados biogênicos associada a maiores valores de carbono orgânico total, e fertilidade. Nessa área também foram observados maiores valores de diâmetro médio ponderado e o diâmetro médio geométrico dos agregados. Na parte inferior, na área de consórcio foi quantificada a maior porcentagem de agregados biogênicos e quantificados os menores teores de P, Ca+2, Mg+2 e K+. Os sistemas de manejo influenciaram nas vias de formação dos agregados. A classificação morfológica representa uma importante ferramenta para o monitoramento do manejo do solo. A aveia preta promoveu o aumento da formação dos agregados biogênicos, os quais se comportaram como compartimentos de reservas de nutrientes.

ABSTRACT The objective of this study was to evaluate the efficiency of black oat (Avena strigosa Schreb) crops in recovering soil aggregation, and quantify the nutrient contents in aggregates considering their formation pathways (biogenic and physicogenic) in crop areas in a mountains environment in the municipality of Nova Friburgo, RJ, Brazil. The landscape was stratified into two sections for the study: upper, two areas with black oat crops, one fertilized and one not fertilized one not fertilized, and one adjacent forest area representing the original soil conditions; and lower: one fertilized area with black oat, and one fertilized area with black oat intercrops with oilseed radish (Raphanus sativus L.) and vetch (Vicia sativa L.), and one adjacent forest area representing the original soil conditions. The aggregates were separated according to their formation pathways, quantifying the weight percentage of each formation pathway. The aggregate stability and nutrient and organic carbon contents were evaluated. The fertilized area in the upper section had the highest biogenic aggregate percentage, which was associated with the highest total organic carbon contents, and soil fertility. This area also had the highest weighted mean diameter (WMD) and geometric mean diameter (GMD) of aggregates. The intercrop area in the lower section had the highest biogenic aggregate percentage and the lowest P, Ca+2, Mg+2, and K+ contents in the aggregates. The management systems affected the aggregate formation pathways. Morphological classification is an important tool for the monitoring of soil management. The black oat crops increased the biogenic aggregate formation, which become reservoir of nutrients.

Resumo Com a nova legislação ambiental brasileira vislumbra-se a possibilidade do uso de sistemas agroflorestais diversificados para recompor áreas de preservação permanente e reserva legal, principalmente em pequenas propriedades rurais. Uma pergunta que surge, diz respeito à capacidade desses sistemas em reduzir custos na restauração florestal e, ao mesmo tempo apresentar eficiência ecológica similar aos plantios em que se faz uso exclusivo de espécies nativas do bioma em questão. Buscando a resposta avaliou-se nesse estudo um sistema agroflorestal implantado em 2005, em Seropédica - RJ, que tinha o objetivo de interligar dois fragmentos florestais ali existentes. Desde então foram feitas avaliações da serapilheira, micro e mesofauna do solo desse “corredor agroflorestal” na interligação desses fragmentos. Os resultados indicaram que a quantidade e a qualidade da fauna do solo e fungos micorrízicos foram favorecidos pelo sistema agroflorestal em comparação à matriz de pastagem, mas tanto a riqueza, quanto a abundância ainda se encontram em níveis inferiores aos fragmentos florestais interligados. A pastagem próxima ao sistema agroflorestal vem se beneficiando da melhoria ambiental ali existente, criando um “efeito de borda positivo”, situação bem distinta da pastagem que se encontrava mais distante da área de influência do corredor agroflorestal. Para os indicadores utilizados, o sistema agroflorestal foi eficiente.

Abstract The Brazilian new environmental law permits the use of agroforestry systems to restore degraded areas protected by legislation, especially in small farms. One question that arises is if it is possible to reduce costs of the restoration process with these agroforestry systems and, at the same time, to offer ecological services, similar to afforestation with the exclusive use of native species of the Atlantic Forest biome. Seeking results to proof the effectivity, an agroforestry system established in 2005, at Seropédica, RJ state, with the objective of connecting two forest fragments, went through a series of evaluations realized on the ecological effectiveness on the connection of these fragments. The results indicated that the quantity and quality of soil fauna and mycorrhizal fungi obtained benefits by the agroforestry system in comparison to the pasture matrix but are still at lower levels than the forest fragments. Pasture near the agroforestry system has benefited from the environmental improvement there, originated from a “positive edge effect”, a situation quite different from the pasture that was farther from the area of influence of the agroforestry corridor. For the indicators used, the agroforestry system was efficient.

ABSTRACT Termites have peculiar activities in the soil, inducing significant changes in the soil properties. The objective of this study was to assess physical and chemical properties and soil organic matter to evaluate the effect of termite activity and termite mounds on the soil. Two toposequences were selected and divided in slope thirds (shoulder, backslope, and footslope). In each of these, four termite mounds were selected. Samples were taken from the soils and termite mounds (top, center, and base) along with a variety of termites for identification. Analyses were carried out for physical, soil texture, and chemical properties, as well as for particle size and chemical fractioning of organic matter. The species Cornitermes cumulans was found in all mounds. Soil with termite mound presented higher clay content, acidity, and Al3+ content. Phosphorus contents differed considerably between mound material and soil. Sum of bases and cation exchange capacity of the soil were higher in mounds, and differed within the mounds, according to the sampling height. Total organic carbon and particulate carbon content were highest at the mound base. A marked disparity was observed between the contents of humic substances in the mounds and surrounding soil, with humin fraction differences in distinct topographic position. The high nutrient contents detected in the termite mounds confirm the importance of termites in concentrating nutrients.

ABSTRACT We characterized soil physical and chemical properties and soil organic matter in epigeal termite mounds in pastures to evaluate the changes promoted by termites in comparison to an adjacent area. We selected seven active epigeal termite mounds in the municipality of Seropédica, state of Rio de Janeiro, Brazil. Soil samples were collected from top, center and base positions of each mound, at 0.50 and 1.50 m distance from the base of the mound. We identified individuals of the genus Embiratermes, Velocitermes, and Orthognathotermes. The humin fraction predominated over the humic and fulvic acid fractions both in mounds and adjacent soil. The amount of organic matter and the mineral fractions (mineral-associated organic carbon - MOC) varied among builder species. The studied chemical attributes point to a higher concentration of nutrients in the mounds than in the adjacent soil.

RESUMO Compreender a variabilidade espacial dos atributos químicos e físicos do solo é importante para melhorar as práticas de manejo e conservação do solo. Por sua vez, a variabilidade espacial das propriedades do solo resulta da variação das características morfológicas do relevo. Assim, o objetivo deste estudo foi avaliar a influência da curvatura da superfície na variabilidade espacial dos atributos químicos e físicos do solo na região de Mar de Morros (Pinheiral-Rio de Janeiro, Brasil). Foram selecionadas duas pedoformas adjacentes com curvatura convexa e côncava e coletadas amostras de solo em uma grade com espaçamento fixo de 10 metros entre os pontos. Foram coletadas um total de 56 amostras de solo (0-5 cm de profundidade) nas duas pedoformas e analisados os atributos físicos e químicos do solo. Na análise dos dados foi utilizada estatística descritiva e geoestatísitca. Os atributos químicos do solo apresentaram um padrão aleatório quanto a distribuição espacial em ambas as pedoformas. No entanto, a pedoforma côncava apresentou maiores valores de pH e potássio e valores mais baixos para alumínio quando comparada a pedoforma convexa. Por outro lado, os valores de silte apresentaram dependência espacial em ambas às pedoformas. Já a densidade do solo e o teor de argila apresentaram dependência espacial na pedoforma convexa. Os valores da densidade do solo e silte aumentaram no sentido do terço superior para o terço inferior em ambas as pedoformas. Os resultados mostram que para esta área de estudo, a curvatura da superfície tem maior influência na dependência espacial dos atributos físicos do que para os atributos químicos solo.

ABSTRACT Understanding the spatial variability of soil chemical and physical attributes is important for improving management practices and soil conservation. In turn, the spatial variability of soil properties results from variation in morphological relief characteristics. Thus, the purpose of this study was to evaluate the influence of landform curvature on the spatial variability of soil chemical and physical attributes in the Mar de Morros region (Pinheiral-Rio de Janeiro State, Brazil). Two adjacent landforms were selected with convex and concave curvature and sampled in a regularly spaced grid of 10 meters. A total of 56 soil samples (0-5 cm depth) from the two landforms were collected and analyzed for physical and chemical attributes. The data were analyzed using descriptive statistics and geostatistics. All chemical attributes showed random patterns of spatial variability in both landforms. The concave landform had higher values of pH and potassium and lower values of aluminum than the convex landform. In contrast, silt content showed spatial dependence in both the concave and convex landforms. Bulk density and clay showed spatial dependence in the convex landform. Bulk density and silt content increased from the shoulder to the footslope of both landforms. The results show that, for this study area, landform curvature has more influence on the spatial dependence of soil physical attributes than of soil chemical properties.

RESUMO A matéria orgânica do solo é uma importante fonte primária de nutrientes às plantas e influencia a infiltração, retenção de água, suscetibilidade à erosão e agregação do solo. No entanto, esse processo está condicionado à qualidade e quantidade da matéria orgânica aportada. O objetivo deste trabalho foi avaliar a influência do desastre ambiental causado pela chuva em áreas de produção de oleráceas na região Serrana do Rio de Janeiro. Foram selecionadas as seguintes áreas: A1: sem impacto (testemunha); A2: soterramento total e cultivo de aveia + ervilhaca; A3: transbordamento do rio e cultivo de milheto + girassol; A4: transbordamento do rio e grande deposição de areia com cultivo de aveia-preta; A5: transbordamento do rio com grande deposição de areia e sem cultivo; e A6: transbordamento do rio em pequena escala e sem cultivo. As propriedades edáficas analisadas foram: textura; densidade do solo (Ds); densidade de partículas (Dp); diâmetro médio ponderado (DMP) e diâmetro médio geométrico (DMG) de agregados estáveis em água; pH(H2O), Al3+, Ca2++Mg2+, Na+, H+Al, K, P e carbono orgânico total (COT); e frações granulométricas e químicas da matéria orgânica. Os maiores valores de DMP e DMG foram observados nas áreas A3 e A6, que seguem a mesma tendência dos maiores teores de argila. Os teores de COT e suas frações químicas e físicas apresentaram diferenças em relação à testemunha com os menores valores verificados nas áreas que foram submetidas ao impacto pelo transbordamento do rio e grande deposição de areia. As áreas que foram impactadas pelo soterramento com predomínio da fração argila apresentaram valores semelhantes ou superiores aos da testemunha. As variáveis foram selecionadas e avaliadas por meio da análise de componentes principais, que evidenciou distinção entre as áreas estudadas, com separação entre elas associada à textura do solo e densidade de partículas.

ABSTRACT Soil organic matter is an important primary source of nutrients for plants and influences infiltration, water retention, susceptibility to erosion, and soil aggregation. However, this process is conditioned on the quality and quantity of organic matter supplied. The objective of this study was to evaluate the influence of the environmental disaster caused by rain in areas of horticulture production in the mountainous region of Rio de Janeiro. The following areas were selected: A1- no impact (control); A2 - totally covered by landslide and cultivation of oats + vetch; A3 - river overflow and cultivation of millet + sunflower; A4 - river overflow and extensive deposition of sand and growing of black oats; A5 - river overflow with extensive deposition of sand and no cultivation; and A6 – river overflow on a small scale and no cultivation. The soil properties analyzed were texture; bulk density (BD); particle density (Pd); mean weight diameter (MWD) and geometric mean diameter (GMD) of water-stable aggregates; pH(H2O), Al3+, Ca2++Mg2+, Na+, H+Al, K, P, and total organic carbon (TOC); and particle size and chemical organic matter fractions. The highest values of the DMG and DMP were observed in areas A6 and A3, which also have the highest clay contents. The TOC content and its chemical and physical fractions showed differences compared to the control, with the lowest values observed in areas that underwent the impact of river overflow and extensive sand deposition, since the areas that were affected by landslide with predominance of the clay fraction showed values similar or superior to reference values. Principal component analysis clearly showed a distinction among the areas studied, and this distinction is clearly associated with soil texture and particle density.

Os organismos que constituem a fauna do solo são de grande relevância para os compartimentos serapilheira-solo, por atuarem em importantes processos, como fragmentação do material vegetal, decomposição e ciclagem de nutrientes. Este estudo objetivou avaliar a comunidade da fauna invertebrada do solo sob o cultivo de cana-de-açúcar colhida sem queima, considerando-se a deposição de diferentes quantidades de palhada sobre o solo. Os tratamentos consistiram de diferentes quantidades de palhada de cana-de-açúcar: T0% (0 Mg ha-1); T<img border=0 width=32 height=32 src="../../../../../../img/revistas/pat/v44n4/a02car01.jpg">25% (2,2 Mg ha-1); T<img border=0 width=32 height=32 src="../../../../../../img/revistas/pat/v44n4/a02car01.jpg">50% (5,1 Mg ha-1); T <img border=0 width=32 height=32 src="../../../../../../img/revistas/pat/v44n4/a02car01.jpg">75% (7,8 Mg ha-1); e T<img border=0 width=32 height=32 src="../../../../../../img/revistas/pat/v44n4/a02car01.jpg">100% (12,0 Mg ha-1). A amostragem aconteceu no período seco e final do período chuvoso, com armadinhas "Pitfall". O número de indivíduos por armadilha ao dia, no período seco, variou entre 11,1 (T0%) e 14,7 (T<img border=0 width=32 height=32 src="../../../../../../img/revistas/pat/v44n4/a02car01.jpg">25%) e, no período chuvoso, de 15,11 (T0%) a 33,15 (T<img border=0 width=32 height=32 src="../../../../../../img/revistas/pat/v44n4/a02car01.jpg">75%). Os maiores valores de Shannon foram observados no período chuvoso, e os menores valores de diversidade e equitabilidade resultaram da maior incidência dos grupos Araneae e Formicidae. A quantidade de palhada sobre o solo não proporcionou grande influência nos índices ecológicos e riquezas total e média. A época da coleta influenciou na variação do número de indivíduos, riqueza de espécies, índice de Shannon e de Pielou. Amanutenção da palhada promoveu benefícios para a fauna do solo, em relação ao manejo tradicional.

The organisms that constitute the soil fauna are highly relevant to the litter-soil compartments, because they act in important processes, such as fragmentation of the plant material, decomposition and nutrients cycling. This study aimed to evaluate the invertebrate fauna community in soil cultivated with sugarcane harvested without burning, considering the maintenance of different straw levels on the soil surface. Treatments consisted of different amounts of sugarcane straw: T0% (0 Mg ha-1); T<img border=0 width=32 height=32 src="../../../../../../img/revistas/pat/v44n4/a02car01.jpg">25% (2.2 Mg ha-1); T<img border=0 width=32 height=32 src="../../../../../../img/revistas/pat/v44n4/a02car01.jpg">50% (5.1 Mg ha-1); T<img border=0 width=32 height=32 src="../../../../../../img/revistas/pat/v44n4/a02car01.jpg">75% (7.8 Mg ha-1); and T<img border=0 width=32 height=32 src="../../../../../../img/revistas/pat/v44n4/a02car01.jpg">100% (12.0 Mg ha-1). Samples were collected in the dry season and late wet season, with "Pitfall" traps. The number of individuals per trap per day during the dry period ranged from 11.1 (T0%) to 14.7 (T<img border=0 width=32 height=32 src="../../../../../../img/revistas/pat/v44n4/a02car01.jpg">25%) and, in the rainy season, from 15.11 (T0%) to 33.15 (T<img border=0 width=32 height=32 src="../../../../../../img/revistas/pat/v44n4/a02car01.jpg">75%). The highest Shannon values were observed during the rainy season, and the lowest values for diversity and equitability resulted in a higher incidence of Araneae and Formicidae groups. The amount of straw on soil showed no significant influence on ecological indices and total and average wealth. The harvest time affected the number of individuals, species wealth and Shannon and Pielou's indices. The maintenance of straw on the soil surface benefitted the soil fauna, concerning the conventional crop management.

O objetivo deste trabalho foi avaliar indicadores químicos, físicos e biológicos da degradação de pastagens em áreas contrastantes quanto à ocorrência de cupinzeiros. Foram avaliadas as áreas de pastagem com a cultivar Marandu de Urochloa brizantha (Syn. Brachiaria brizantha), quanto à ausência (pasto 1) ou à presença (pasto 2) de cupinzeiros, e área com vegetação nativa de Cerrado. Foram avaliados: granulometria e fertilidade do solo; atividade microbiana do solo; nitrogênio potencialmente mineralizável; produção da gramínea em oferta; liteira existente e depositada no período de 28 dias; e fração leve da matéria orgânica do solo. No pasto 2, os cupinzeiros foram contados e 20 ninhos foram sorteados para coleta e identificação de cupins. Cornitermes cumulans foi a única espécie coletada, com média de 128 ninhos por hectare, tendo ocupado 0,1% da área útil. Entre os indicadores avaliados, apenas a oferta e a liteira diferiram entre as áreas de pastagens. A maior densidade de cupinzeiros não pode ser relacionada à acidez do solo ou aos outros parâmetros avaliados. A presença de cupinzeiros não é indicador de degradação química e biológica da pastagem e não está associada à alteração na dinâmica de resíduos da parte aérea de capim-marandu.

The objective of this work was to evaluate chemical, physical and biological indicators of degradation of pastures in areas with contrasting occurrence of termite mounds. Pasture areas with the Marandu cultivar of Urochloa brizantha (Syn. Brachiaria brizantha) were evaluated for the absence (pasture 1) or presence (pasture 2) of termite mounds, and an area of native Cerrado vegetation. The following parameters were evaluated: soil texture and fertility; soil microbial biomass; potentially mineralizable nitrogen; forage on offer; existing litter and litter deposited on the soil surface in 28 days; and free light fraction of soil organic matter. In pasture 2, termite mounds were counted and 20 nests were randomly selected for collection and identification of termites. All active mounds were inhabited by the species Cornitermes cumulans, with a mean of 128 mounds per hectare, occupying 0.1% of the net area. Among the indicators evaluated, only forage on offer and litter deposited in 28 days differed between pasture areas. The greater density of termite mounds was not related with the higher acidity of the soil or with the other evaluated parameters. The presence of termite mounds is not an indicator of the chemical and biological degradation of the pasture and is associated with the dynamics of aerial residues of Marandu palisadegrass.

A prática da agricultura de corte e queima tem causado a degradação do solo no Estado do Piauí, e isso tem estimulado a adoção de alternativas sustentáveis de uso da terra, como os Sistemas Agroflorestais. Este trabalho objetivou avaliar as mudanças nas características químicas e nos estoques de carbono (COT) e nitrogênio (NT) de um Argissolo Vermelo-Amarelo sob sistemas agroflorestais com seis (SAF6) e 10 (SAF10) anos de adoção, sistema com base ecológica com três anos de adoção (SE3), agricultura de corte e queima (ACQ) e floresta nativa (FN), no Norte piauiense. Foram coletadas amostras de solo nos períodos seco e chuvoso na profundidade de 0-10 cm, para a avaliação dos atributos químicos do solo e dos estoques totais de carbono (COT) e nitrogênio (NT). O SAF10 apresentou menor teor de Al+3 (0,02 cmol c dm-3). O teor de P no SAF10 (12,27 mg dm-3), no período seco, foi seis a sete vezes maior do que ACQ e FN, respectivamente. Os maiores estoques de COT e NT foram observados no período seco, respectivamente no SAF10 (48,54 Mg ha-1 e 4,43 Mg ha-1) e SAF6 (43,30 Mg ha-1 e 3,45 Mg ha-1). Os sistemas agroflorestais melhoraram a qualidade do solo e podem ser considerados como estratégia conservacionista para o Norte do Piauí.

Slash and burn farming practices have caused land degradation in the state of Piauí. This problem has stimulated the adoption of land use sustainable alternatives such as agroforestry systems. This work aimed to evaluate changes in the chemical characteristics and carbon and nitrogen stocks in Acrisol under six (SAF6) and ten year (SAF10) old agroforestry systems, agriculture with a three year (SE3) ecological basis, slash and burning practices (ACQ), and native forest (FN) in the northern state of Piauí. Soil samples, in the dry and humid periods, were collected in the 0-10 cm depth. Chemical soil properties, total organic carbon (TOC) and total nitrogen (TN) were evaluated. SAF10 showed lower Al +3 content (0.02 cmol c dm-3) in relation to the other systems. In the dry season, P content in SAF10 (12.27 mg dm-3) was six to seven times larger than ACQ and FN, respectively. The highest values of TOC and TN were observed, in the dry season, respectively, in the SAF10 (48.54 Mg ha-1 and 4.43 Mg ha-1) and SAF6 (43.30 Mg ha-1 and3.45 Mg ha-1). Agroforestry systems improved soil quality and can be considered conservation strategy for northern Piaui.

O objetivo deste trabalho foi avaliar o efeito do uso do solo sobre a densidade e a diversidade da macrofauna invertebrada, bem como a relação dessa com atributos químicos do solo em diferentes agroecossistemas. Foram estudados cinco agroecossistemas: sistema ecológico com três anos de adoção (SE3), sistemas agroflorestais com seis (SAF6) e dez (SAF10) anos de adoção; agricultura de corte e queima (ACQ), e floresta nativa (FN). Em cada sistema, foram coletadas aleatoriamente cinco amostras solo, em forma de blocos (25x25 cm), na profundidade de 10 cm, nas épocas seca (outubro, 2006) e chuvosa (maio, 2007). A relação entre os atributos químicos e a macrofauna edáfica, nos diferentes sistemas de uso do solo, foi determinada por meio da análise da coinércia. Maior abundância da macrofauna foi observada na época chuvosa. Os sistemas SE3, SAF6 e SAF10 apresentaram maior riqueza de espécies e índices de Shannon e Pielou, independentemente da época de coleta. O manejo agroflorestal favoreceu a ocorrência de "engenheiros do ecossistema". Os sistemas agroflorestais propiciam melhores características químicas do solo e aumentos na abundância e riqueza da macrofauna invertebrada do solo.

The objective of this study was to evaluate land use effects on the abundance and diversity of invertebrate macrofauna and its relationship with the soil chemical characteristics in different agroecosystems. Five systems were studied: ecological based system at three years of adoption (ES3), agroforestry systems at six (AFS6) and ten years of adoption (AFS10), slash and burn agriculture (SBA), and native forest (NF). In each system, five samples were collected in the form of soil monoliths (25x25 cm) at 10 cm depth, during the dry (October 2006) and rainy seasons (May 2007). The relationship between edaphic macrofauna and chemical attributes in the different land use systems was determined by coinertia analysis. The highest abundance of macrofauna was observed in the rainy season. Systems SE3, SAF6 and SAF10 showed higher species richness and indices of Shannon and Pielou, regardless of the sampling season. The agroforestry management favored the occurrence of "ecosystem engineers". Agroforestry systems provide better soil chemical characteristics and increase soil invertebrate macrofauna abundance and richness.

Este trabalho teve como objetivos avaliar o estoque de serapilheira acumulada e quantificar os teores de N, P, K, Ca e Mg em sistemas agroflorestais com seis (SAF6) e dez (SAF10) anos de adoção, sistema com base ecológica de três anos (SE3), agricultura de corte e queima (ACQ) e floresta nativa (FN) no Município de Esperantina, norte do Piauí. As coletas foram realizadas nos períodos chuvoso e seco do ano 2007, sendo a serapilheira separada nas frações folhas e galhos para a estimativa dos estoques acumulados sobre o solo. Os maiores estoques da fração folhas foram observados na FN (3,8 Mg(t) ha-1), período seco; e da fração galhos no SAF10 (2,2 Mg(t) ha-1), no período chuvoso. Os SAFs apresentaram os maiores teores de nutrientes nas frações da serapilheira e entre os nutrientes, e a concentração de N foi superior à dos demais nutrientes, em ambos os períodos. A estimativa de transferência dos nutrientes pela serapilheira obedeceu à sequência N>Ca>K>P>Mg. Os valores de estoques da serapilheira, teores e aportes de nutrientes nos SAFs evidenciam a contribuição do manejo agroflorestal para a qualidade do solo e a sustentabilidade econômica do sistema.

This work aimed to evaluate litter deposition and quantify contents of N, P, K, Ca and Mg in agroforest systems six (AFS6) and ten (AFS10) years after implantation, in three-year old ecological based systems (ES3), slash-and-burn agriculture (SBA) and native forest (NF), all located in Esperantina, northern region of Piauí, Brazil. Collections were carried out in the wet and dry seasons of 2007. The litter was separated into leaves and branches and weighted to estimate the deposition on the soil. The highest leaf depositions were found in NF (3.8 Mg ha-1), in the dry season, whereas for branches, in the AFS10 (2.2 Mg ha-1), in the wet season. AFS showed the highest nutrient contents in the litter fractions, and, among them the N concentration was higher than the others, in both seasons. The estimate transfer of nutrients by the litter followed the sequence N>Ca>K>P>Mg. The values for litter deposition and contents and input of nutrients in the AFS systems show the contribution of the agroforest management to soil quality and the economic sustainability of the system.