Resumo Os atributos físico-hídricos do solo são interdependentes e o planejamento e o manejo do solo são dificultados devido à alta variabilidade desses atributos. O presente estudo objetivou avaliar a variabilidade dos atributos físico-hídricos em uma topossequência inserida em área de regeneração espontânea na Baixada Litorânea Fluminense. Foram selecionados quatro perfis, e nestas coletadas amostras nos horizontes superficiais e subsuperficiais para quantificação dos valores da umidade, densidade do solo, macroporosidade, microporosidade, condutividade hidráulica, granulometria e resistência do solo à penetração (com penetrômetro de bancada e em campo). Foi realizada a análise exploratória e calculados os parâmetros descritivos, o teste de correlação de Pearson e a análise dos componentes principais. Nos horizontes A, o teor de argila variou de 59,0 a 577,0 g kg-1, a umidade de 1,5 a 16,4% e a microporosidade 10,4 a 46,2%, entre os perfis P3 (Planossolo) e P4 (Gleissolo). A resistência à penetração nos dois métodos esteve mais relacionada com o perfil 1 (Argissolo), entretanto, os valores máximos não restringem o desenvolvimento das raízes. A variabilidade dos atributos físico-hídricos em vertentes de pequeno comprimento é alta, principalmente para os atributos condutividade hidráulica, umidade, microporosidade, e argila do solo. Na baixada a maior variabilidade dos atributos físico-hídricos é explicada pelos atributos argila, microporosidade, silte e umidade. O incremento de argila em profundidade aumenta a densidade e a resistência do solo à penetração das raízes.

Abstract Soil physical and hydraulic properties are interdependent, and soil-use planning and management are complicated by the high variability of these attributes. The current study assessed the variability of physical and hydraulic properties of soils along a toposequence located in a forest fragment under spontaneous regeneration in the coastal lowlands of Rio de Janeiro. Four soil profiles were selected, and samples were collected from surface and subsurface horizons for determination of moisture content, bulk density, macroporosity, microporosity, hydraulic conductivity, texture, and soil resistance to penetration (measured using benchtop and field penetrometers). Exploratory and principal component analyses were performed, and descriptive parameters and Pearson’s correlation coefficients were calculated. In A horizons of profiles 3 (Planossolo) and 4 (Gleissolo), clay contents ranged from 59.0 to 577.0 g kg-1, moisture contents from 1.5 to 16.4%, and microporosity from 10.4 to 46.2%, respectively. Field- and laboratory-measured penetration resistances showed a stronger association with profile 1 (Argissolo); however, values were not sufficiently high to limit root development. The variability in soil physical and hydraulic properties in short slopes is high, mainly in terms of hydraulic conductivity, moisture, microporosity, and clay content. The greater variability of soil physical and hydraulic properties in lowland is attributed to clay and silt fractions, microporosity, and moisture content. The increment in clay content with depth increases bulk density and resistance to root penetration.

Resumo A erosão hídrica é uma das principais formas de degradação do solo, causando danos econômicos, ambientais e sociais. O objetivo deste estudo foi avaliar o efeito de diferentes estágios de formação de voçorocas (inicial - IG; juvenil - JG; maduro - MG; e senil - SG) nos atributos químicos, matéria orgânica e microbiológicos do solo, utilizando uma floresta secundária (SF) e duas áreas de pastagem como referência no ambiente “Mar de Morros” do bioma Mata Atlântica brasileira. Amostras de solo (profundidade 0-0,05 m) foram coletadas no final das estações chuvosa e seca. As voçorocas em diferentes estágios de formação promoveram diminuição da fertilidade do solo e modificação dos atributos microbiológicos, principalmente quando comparados com a área de floresta secundária. Reduções de mais de 60% no carbono orgânico total (TOC), carbono orgânico oxidável (POXC), atividade da FDA, β-glicosidase, fosfatase ácida, C (MBC) e N (MBN) da biomassa microbiana, respiração basal do solo (BSR) e proteína do solo relacionada à glomalina (GRSP) foram observados em voçorocas nos estágios inicial (IG) e intermediário (JG e MG) quando comparados ao SF. Verificou-se que o efeito da erosão sobre os atributos químicos e microbiológicos do solo é mais intenso em voçorocas nos estágios inicial e intermediário em comparação com ao senil (SG). Usando a multivariada PCA, os atributos microbiológicos e químicos do solo discriminaram as voçorocas com distintos estágios de formação. Os atributos químicos, TOC, POXC, atividade FDA, β-glicosidase, fosfatase ácida, MBC and MBN, SBR e GRSP são bons indicadores para avaliar o processo de estabilização da erosão em voçorocas.

Abstract Water erosion is one of the main forms of soil degradation, causing economic, environmental, and social damage. This study evaluated the effects of different formation stages of gullies (initial - IG; juvenile- JG; mature - MG; and senile - SG) on the chemical, organic carbon and microbiological attributes of soil, using a secondary forest (SF) and two areas of pasture as references in the “Mar de Morros” environment of the Brazilian Atlantic Forest biome. Soil samples (depth 0-0.05 m) were collected at the end of the rainy and dry seasons. Gullies in different stages of formation promote a decrease in soil fertility and modification of microbiological attributes, particularly when compared with secondary forest areas. Reductions of over 60% in total organic carbon (TOC), oxidizable organic carbon (POXC), FDA activity, β-glycosidase, acid phosphatase, C and N from microbial biomass, basal soil respiration (BSR) and glomalin-related soil protein (GRSP) were observed in gullies in early (IG) and intermediate (JG and MG) stages when compared to SF. It was found that the effect of erosion on soil chemical and microbiological attributes is more intense in gullies in the initial and intermediate stages compared with those in the senile stage (SG). Using multivariate PCA, the microbiological and chemical attributes of the soil are discriminated between gullies with distinct formation stages. Chemical attributes, TOC, POXC, FDA activity, β-glycosidase, acid phosphatase, MBC and MBN, BSR, and GRSP are good indicators for evaluating the process of erosion stabilization in gullies.

RESUMO Os estudos sobre a variabilidade espacial de atributos do solo de pastagens tropicais buscam conhecimentos que possam auxiliar nas tomadas de decisões sobre os manejos destes solos. O presente estudo teve como objetivo avaliar a variabilidade espacial de atributos químicos do solo e seus efeitos na produtividade de área cultivada com Tifton 85. O experimento foi realizado na Fazenda Feno Rio, localizada na Universidade Federal Rural do Rio de Janeiro, em Seropédica, em uma área de 3,91 ha. Os solos foram amostrados em malha irregular, perfazendo o total de 50 pontos georreferenciados, nas profundidades de 0-0,20 e 0,20-0,40 m. Foram analisados os atributos químicos do solo pH em água, Al+3, Ca+2, Mg+2, Na+, K+, P, H+Al e COT, além da massa seca (MS) da Tifton 85 para avaliação da produtividade. A partir destes parâmetros foram realizadas análises de estatística descritiva, correlação linear, geoestatística e geração de mapas. Foi possível inferir diferentes zonas de produtividade em relação à média geral, verificando-se que a produtividade média na área foi de 2.248 kg ha-1. Os parâmetros químicos do solo Na+, Ca+2, COT e H+Al correlacionaram significativamente com a MS, confirmando serem importantes e interferirem na produtividade da Tifton 85. Percebeu-se que a realização de mapeamentos ao longo do ciclo da Tifton 85 são importantes na compreensão da variabilidade da produção de MS e a investigação de áreas com diferentes potenciais produtivos deve ser acompanhada de mapas de atributos químicos do solo, buscando correlacionar e entender as razões que podem estar envolvidas nestas variações.

ABSTRACT Studies on spatial variability of soil attributes of tropical pastures gather information that can assist in decision making about managements of these soils. The objective of the present study was to evaluate the spatial variability of soil chemical attributes and their effects on grass yield of Tifton 85. The experiment was carried out in an area of 3.91 ha at the Feno Rio Farm of the Federal Rural University of Rio de Janeiro, Seropédica, RJ, Brazil. Soils of the 0-0.20 and 0.20-0.40 m layers were sampled considering an irregular sampling mesh, making a total of 50 georeferenced points. The parameters evaluated were: the soil chemical attributes pH, Al+3, Ca+2, Mg+2, Na+, K+, P, H+Al, and total organic carbon (TOC); and the Tifton 85 dry matter yield (DMY). The results of these parameters were subjected to descriptive statistics, linear correlation, and geostatistics, and maps were developed for the analyses. Regions with grass yields different from the general mean were found in the area, which presented mean grass yield of 2248 kg ha-1. The soil chemical parameters Na+, Ca+2, TOC, and H+Al were significantly correlated with DMY, confirming that they are important and affect the Tifton 85 grass yield. The mapping of the Tifton 85 cycle is important for understanding the variability of DMY. The investigation of areas with different productive potentials should be followed by development of maps of soil chemical attributes to correlate and understand the ratios that may be involved with these variations.

Resumo O solo é um recurso natural fundamental para a subsistência e desenvolvimento da humanidade, sendo principalmente explorado pela agricultura, cujas práticas inadequadas comprometem as condições edáficas, favorecendo a ocorrência de processos erosivos, que culminam principalmente na perda de solo e nutrientes. A erosão hídrica atua como principal forma de degradação do solo, em que, a partir da ação do impacto da gota de chuva sobre o solo, ocorre o desprendimento de partículas que, associadas a fatores como clima, relevo, solo vegetação e uso e ocupação, favorecem esse processo. O objetivo do estudo foi classificar quatro voçorocas com base em seus estágios evolutivos e julgar as classificações físico-químicas do solo nas faces internas e externas das voçorocas. A morfologia das voçorocas foi classificada por imagem aérea gerada por drone. As voçorocas foram mapeadas usando imagens do Google Earth a partir de 2016. A avaliação qualitativa foi realizada usando o modelo digital de curvatura de elevação de campo (MDSC) com validação de campo. Amostras deformadas foram coletadas nas profundidades de 0-10 e 10-20 cm, enquanto amostras não deformadas foram coletadas em profundidades de 0-10 cm para avaliar seus atributos químicos e físicos. De posse dos dados foi realizada análise estatística não paramétrica de Kruskal-Wallis a 5%. Os atributos químicos e físicos do solo diferiram de acordo com o estágio evolutivo nas faces (interna e externa) em profundidades de 0 a 10 cm, enquanto as faces mostraram diferenças em profundidade de 10 a 20 cm.

Abstract Soil is a fundamental natural resource for subsistence and development of humanity, exploited mainly for agriculture. Agricultural practices, though, are improperly performed, compromising edaphic conditions and favoring erosive processes, which mainly culminate in the loss of soil and nutrients. Water erosion represents the main form of soil degradation, given that the impact of raindrops on the soil results in the detachment of particles, a process favored by factors such as climate, relief, soil vegetation and use and occupation. The objective of the study was to classify four gullies based on their evolutionary turns and to judge the physical-chemical classifications of the soil at the internal and external faces of the gullies. The morphology of the gullies was classified by aerial images generated by drones. The gullies were mapped using Google Earth images from 2016. The qualitative assessment was performed using the digital field-elevation curvature (MDESC) model with field validation. Deformed samples were collected at depths of 0-10 and 10-20 cm, while non-deformed samples were collected at depths of 0.0-0.10 cm to evaluate their chemical and physical attributes. A nonparametric 5% Kruskal-Wallis statistical analysis was performed on the resulting data. The chemical and physical attributes of the soil differed according to the evolutionary stage of the surfaces (internal and external) at depths of 0 to 10 cm, while the faces showed differences in depth of 10 to 20 cm.

Abstract This study aimed to evaluate enzyme activity, glomalin-related soil proteins (GRSP), soil chemical attributes, and total organic carbon (TOC) in two Agroforestry systems (AFS) (AFS-1 and AFS-2), in a traditional agriculture area (TA), and secondary forest (SF) area in Paraty (RJ). Soil samples (from 0 to 5 cm depth) were collected during the rainy and dry seasons. AFS improves and/or maintains soil chemical indicators based on pH increase, reduces aluminum saturation and maintains soil nutrient content (Ca, Mg and K), when compared with SF. The contribution of organic material and the biodiversity of the AFS provide the maintenance of the total organic carbon content of the soil. AFS maintain the activity of the enzymes protease, β-glucosidase, acid phosphatase, and total enzyme activity (FDA), and the production of glomalin-related soil protein at levels similar to those observed in SF, especially during the rainy season.

ABSTRACT The objective of this study was to evaluate the influence of natural pasture and spontaneous regeneration on soil chemical properties and epigeal fauna community using a secondary Atlantic Forest as reference. The study areas were located in Passa Vinte, Minas Gerais, Brazil. In each study area, pitfall traps were used to sample epigeal fauna in the dry and rainy seasons. Earth samples were collected at a depth of 0-5 cm in the dry and rainy seasons for analysis of chemical attributes. The pasture and regeneration areas showed an overall activity of epigeal fauna and functional groups similar to the forest area. However, the diversity evaluated by the Shannon and Pielou evenness indices and the total richness were lower than the observed in the forest. The best fertility attributes were observed in the forest and pasture areas.

ABSTRACT The Atlantic Forest degradation and fragmentation imposes the need for soil and vegetation assessments in order to estimate the environmental vulnerability of the remnants. The objective of this study was to evaluate the georadar applications in areas of Atlantic Forest under different forms of use in Pinheiral, State of Rio de Janeiro, Brazil, through penetrometer impact and ground penetrating radar (GPR). Forest fragments at different stages of regeneration, and pasture and agriculture (perennial and annual) areas were selected for study. Soil characterization was performed through measurements of soil resistance to penetration (SRP) with an impact penetrometer, and the soil properties with a ground penetrating radar (georadar). SRP increased in the forest areas at initial, medium and advanced stages from 2.0 to 2.5, 2.0 to 3.0 and 2.5 to 6.0 MPa, respectively. In the perennial and annual agriculture areas, the increase in SRP was due to differences in their mineral composition, and the lowest values found in the annual agriculture area were due to fauna activity. The employment of GPR generated information in a more rapid manner than with the use of impact penetrometer.

ABSTRACT The removal of original vegetation for crops and pasture production and then followed by natural regeneration is a standard practice in the Atlantic Forest, which has produced patches with different degrees of degradation and regeneration across the landscape. The aim of this study was to evaluate the effects of replacement of native forest by pasture and natural regeneration of vegetation on soil and on soil organic matter (SOM) dynamics in the dry and rainy season in an Atlantic Forest fragment in Passa Vinte, Minas Gerais (MG), Brazil. Soil samples were collected in the rainy and dry season, at a depth of 0.00-0.05 m. The variables determined were total organic carbon (TOC) and particle-size fractions of SOM [particulate organic carbon (POC) and mineral-associated organic carbon (MOC)]; microbial activity by basal respiration (BR) and microbial biomass carbon (MBC); species richness (SR) and spore abundance (SA) of arbuscular mycorrhizal fungi (AMF); and total and easily extractable glomalin-related soil protein (T-GRSP and EE-GRSP, respectively). The conversion of native forest into pasture reduced TOC, POC, MOC, AMF-SA, T-GRSP, and EE-GRSP. However, it did not reduce MBC and BR. The fallow period in the area under natural regeneration was not long enough to restore soil TOC, POC, MOC, BR, MBC, T-GRSP, and EE-GRSP to levels approaching those observed in the forest area. Nevertheless, natural regeneration of vegetation stimulated the production of seedlings (spores) of arbuscular mycorrhizal fungi, which are important for the establishment of plant species and advance of ecological succession. Seasonality affected some of the biological soil properties and SOM dynamics.

O Cerrado é uma das principais regiões de expansão agropecuária do país, entretanto a fragilidade dos seus ecossistemas restringe a capacidade de suporte a muitas das atividades agrícolas e compromete a preservação da sua biodiversidade. O objetivo deste estudo foi definir padrões locais de características edáficas e vegetacionais, em uma sub-bacia em Rio Pardo de Minas (MG), como base para o planejamento local de uso sustentável. Para tal, foram utilizadas técnicas de levantamento fitossociológico e de solos associadas à análise estatística multivariada, dendrograma e análise de componentes principais, de forma a correlacionar distribuição espacial de grupos de espécies e atributos edáficos. Os resultados indicaram a ordenação dos ambientes em dois grupos, em função da natureza dos materiais de origem: arenítico-quartzítico e sedimentos argilo-arenosos e argilosos. A seleção de variáveis pela análise multivariada foi capaz de discriminar os ambientes representados no levantamento fitossociológico. Os padrões identificados pelos agricultores corresponderam, em geral, às variações nos parâmetros florísticos e fitossociológicos e aos atributos edáficos, entre estes a densidade absoluta, a área basal e o índice de diversidade; as frações granulométricas foram determinantes na diferenciação dos ambientes.

The Cerrado is one of the main Brazilian expanding regions for agriculture, but the fragility of its ecosystems limits the support capacity for agriculture activities, jeopardizing the preservation of its biodiversity. The objective of this study was to define local patterns of edaphic and vegetation characteristics, of a small watershed in Rio Pardo de Minas municipality (Minas Gerais State, Brazil), as the basis for the sustainable planning for local usage. For such, techniques of phytosociological survey and soils were applied and associated to multivariate statistical procedures, dendrogram and PCA, in order to correlate the spatial distribution of groups of species with soil attributes. The results showed the classification of the environments into two groups, based on the nature of parent materials: arenitic-quartzitic and sandy-clayey and clayey sediments. The selection of variables using the multivariate analysis was able to discriminate the environments represented in the phytosociological plots. The patterns identified by the local farmers corresponded, in general, to the variations in the floristic and phytosociological parameters and edaphic attributes. The absolute density, basal area, Shannon index and the granulometric fractions were the determinant parameters in the differentiation of the environments.