ABSTRACT Ecotonal transition regions are neglected in floristic and ecological restoration studies, despite their vast occurrence and socioeconomic relevance. The present study evaluated the emergence and initial development of forest species from the ecotonal transition between the Pampas and the Atlantic Forest, in direct seeding, using inter-row green manure (Canavalia ensiformis). We tested sixteen species and evaluated emergence, survival and seedling height rates monthly for twelve months. Six species emerged and established themselves, with mean emergence values of 7%, survival rate of 73% and height of 20 cm. Larger seed species had higher emergence rates. All legumes in the study emerged (Enterolobium contortisiliquum, Parapiptadenia rigida, Bauhinia forficata and Mimosa bimucronata). The pitangueira (Eugenia uniflora) was the only recalcitrant seed species to present emergence. The coverage of jack bean provided greater establishment for Annona sylvatica and Enterolobium contortisiliquum, with statistical significance by the Wilcoxon test. For future studies on direct seeding, we recommend further study on the quality and size of forest seeds, responses in temperate climates, ideal sowing time, density and depth. For the green cover we recommend a higher sowing density and intercropping with other species, including native herbs and shrubs.

RESUMO As regiões de transição ecotonal são negligenciadas em estudos florísticos e de restauração ecológica, apesar da vasta ocorrência e relevância socioeconômica. O presente estudo avaliou a emergência e o desenvolvimento inicial de espécies florestais da transição ecotonal entre Pampa e Mata Atlântica, em semeadura direta, usando adubação-verde na entrelinha (Canavalia ensiformis). Testamos dezesseis espécies e avaliamos os índices de emergência, sobrevivência e a altura de plântulas, mensalmente, por doze meses. Seis espécies emergiram e se estabeleceram, apresentando valores médios de emergência de 7%, índice de sobrevivência de 73% e altura de 20 cm. Espécies de sementes maiores tiveram maiores índices de emergência. Todas as leguminosas do estudo emergiram (Enterolobium contortisiliquum, Parapiptadenia rigida, Bauhinia forficata e Mimosa bimucronata). A pitangueira (Eugenia uniflora) foi a única espécie de semente recalcitrante a apresentar emergência. A cobertura do feijão-de-porco proporcionou maior estabelecimento para Annona sylvatica e Enterolobium contortisiliquum, com significância estatística pelo teste de Wilcoxon. Para futuros estudos sobre semeadura direta, recomendamos aprofundamento na qualidade e tamanho das sementes florestais, nas respostas em clima temperado, na época de semeadura, densidade e profundidade ideais. Para a cobertura verde recomendamos maior densidade de semeadura e consórcio com outras espécies, inclusive herbáceas e arbustivas nativas.

ABSTRACT Soils classified as Alisols are very frequent in the sedimentary agricultural areas of southern Brazil. The presence of red mottles with morphology similar to plinthite and saprolite residue is very common in these soils, and its identification can be considered a difficult task, both in the field and in the laboratory. The incorrect identification of these redoximorphic features can affect soils’ taxonomic and technical classification. We aimed to compare morphological, physical, chemical and mineralogical data to identify reddish mottles, possibly plinthites or saprolite residues, that occur in soils with high textural contrast in southern Brazil. Four soil profiles classified as Argissolos Bruno-Acinzentados (Alisols) were sampled. Matrix and mottles samples from the horizon Bt, CB, C and Cr were separated and subjected to morphological, granulometric, total sand fractionation, chemical extractions of iron and potassium and mineralogical features. Peds from each horizon were submitted to the submersion test in water for 2 and 8 hours and to 5 wetting and drying cycles. The mineralogy indicated the low degree of alteration of the samples, with abundant presence of 2:1 minerals and feldspars, even in the clay fraction. The saprolite resisted in the water submersion tests, making it difficult to interpret the results for the correct identification between plinthites and saprolite fragments. The morphological field data associated with the results of the tests of submersion in water, the cycle of wetting and drying, the dissolution of K and mineralogy, indicate the saprolithic nature of the mottles in all horizons and profiles. The submersion test in water for 2 and 8 hours was not efficient for the plinthite/saprolite identification. The cycle of wetting and drying tests allowed the identification of saprolite.

ABSTRACT Soil physical properties can be changed after vehicle traffic, especially by heavy military tracked vehicles. The Santa Maria military Instruction Field, where the experiment was carried out, is currently the most used area for armored tracked vehicles training in Brazil, with the M113 BR being the main equipment. The aim of this study was to determine the effect of the straight line and pivoted traffic intensity of the M113 BR on the physical properties and advancement of the compaction state of an Abruptic Alisol (Argissolo Vermelho-Amarelo Ta Distrófico abrúptico) with military vehicle traffic history. The study was conducted in a completely randomized design, independently evaluating the effect of straight and pivoting traffic in three soil layers (0.00-0.04, 0.10-0.14, and 0.20-0.24 m). For the straight-line traffic, traffic intensities (TI) with one (TI1), two (TI2), and five (TI5) passes on the same trail were evaluated. For the pivoting traffic, TI with one (TI1P) and two (TI2P) pivots was evaluated. Both studies had two non-traffic treatments (NT). The soil bulk density, total porosity, macroporosity, microporosity, saturated soil hydraulic conductivity, soil penetration resistance, soil bearing capacity, preconsolidation pressure, and gravimetric water content were analyzed in this study. In the straight-line traffic, cases with no significant differences in TP, Ma, Mi, and Ks prevailed. The highest TP, smallest Bd and largest Mi were observed in the 0.10-0.14 m layer. In the pivoting traffic, one pass was sufficient to increase Bd and decrease TP, Ma, Mi, and Ks in the 0.00-0.04 m layer and the increase from one to two pivotings had a significant difference only in Mi in this same layer. Both types of traffic intensity did not affect the PR in any layer. The Abruptic Alisol, pre-compacted from long-term military training, supported the loads applied by the M113 BR when additional traffic occurred in straight line mode, but not when in pivoting mode. The preconsolidation pressure parameter was not appropriate to assess the ability of the soil to support loads applied by pivoting traffic.

Resumo: O objetivo deste trabalho foi avaliar o uso da seleção de covariáveis por conhecimento especializado no desempenho de modelos de predição de classes de solos em uma paisagem complexa, para identificar o melhor modelo preditivo para o mapeamento digital de solos na região Sul do Brasil. Um total de 164 pontos foram amostrados em campo, com uso do hipercubo latino condicionado, tendo-se considerado as covariáveis elevação, declividade e aspecto. A partir do modelo digital de elevação, extraíram-se as covariáveis ambientais que compuseram três conjuntos, formados por: 21 covariáveis, covariáveis após exclusão das multicolineares e covariáveis escolhidas por conhecimento especializado. A predição foi realizada com os seguintes modelos: árvore de decisão, floresta aleatória, regressão logística múltipla e máquina de vetor de suporte. A acurácia dos modelos foi avaliada pelo índice kappa (K), pela acurácia geral (AG) e pela acurácia da classe. Os modelos de previsão foram sensíveis à amostragem desproporcional de classes de solo. O melhor mapa predito obteve AG de 71% e K de 0,59. O uso do conjunto de covariáveis escolhido pelo conhecimento especializado melhora o desempenho do modelo em prever as classes de solo em uma paisagem complexa, e floresta aleatória é o melhor modelo para previsão espacial das classes de solo.

Abstract: The objective of this work was to evaluate the use of covariate selection by expert knowledge on the performance of soil class predictive models in a complex landscape, in order to identify the best predictive model for digital soil mapping in the Southern region of Brazil. A total of 164 points were sampled in the field using the conditioned Latin hypercube, considering the covariates elevation, slope, and aspect. From the digital elevation model, environmental covariates were extracted, composing three sets, made up of: 21 covariates, covariates after the exclusion of the multicollinear ones, and covariates chosen by expert knowledge. Prediction was performed with the following models: decision tree, random forest, multiple logistic regression, and support vector machine. The accuracy of the models was evaluated by the kappa index (K), general accuracy (GA), and class accuracy. The prediction models were sensitive to the disproportionate sampling of soil classes. The best predicted map achieved a GA of 71% and K of 0.59. The use of the covariate set chosen by expert knowledge improves model performance in predicting soil classes in a complex landscape, and random forest is the best model for the spatial prediction of soil classes.

ABSTRACT Human activities often alter soils found in urban areas. These alterations affect their environmental functions and potential for use. However, soils from urban areas in Brazil have not been surveyed and identified, which can pose a technical problem for the development of the city. Considering the importance of urban environments and their soils, this study aimed to evaluate the environmental and morphological characteristics and the physical properties of urban soils in Santa Maria, Rio Grande do Sul, Brazil. The purpose was then to organize a protocol for describing urban soils and to identify diagnostic qualifiers to subsidize establishment of an order that allows proper classification of these soils in the Brazilian Soil Classification System. The protocol containing general and environmental notes and morphological notes and qualifiers was organized based on the experience of this study and the relevant literature. The environmental, morphological, and physical analyses carried out supported interpretation of the urban soils of Santa Maria, their classification in the World Reference Base for Soil Resources system, and identification of diagnostic qualifiers proposed for the Brazilian Soil Classification System. The protocol tested in this study was adequate for data collection in the field. Soils had high variation in layer thickness, particle size composition, color, bulk density, saturated hydraulic conductivity, penetration resistance, stoniness, and the presence of artifacts. Considering the establishment of a Brazilian taxonomy for urban soils, the field data led to the proposal for new qualifiers, such as Saprolitic (residual saprolite material), Impervic (sealed/impermeable layer), Multigranic (layers with contrasting textures), Stonic (layers with stoniness), and Saprorockic (layers constituted of transported saprolite), which can be used as diagnostic attributes in the Brazilian Soil Classification System and even contribute to improvement of the order of Technosols in the World Reference Base For Soil Resources system.

ABSTRACT The study of the relationships between the yield potential of forest stands and the conditions offered for plant development is fundamental for the adequate management of the forest when aiming at sustainable high yields. However, these relations are not clear, especially in commercial forests, on rugged terrain where relationships between the landscape, soil, and plants are more complex. Considering this, we tested the hypothesis that the morphological aspects of the soil conditioned by topography are the main limiting factors for tree development. Our objective was to evaluate the edaphic and topographic influence on the dendrometric variation of Pinus taeda L. of a forest stand in a subtropical climate at high altitude. For that, Spearman’s correlation analysis and canonical correspondence were performed on two data datasets containing pedological, topographic, and dendrometric information of a commercial plantation of Pinus taeda, in the Campo Belo do Sul, Santa Catarina state, Brazil. Soil sampling and characterization was performed in two distinct designs. The first design was based on the morphological description of 11 soil profiles. The second was performed with intensive prospecting of the area, with 102 sampling locations determined through conditioned Latin hypercube sampling. For each sampling point, the height and diameter of the four nearest trees were measured and the terrain attributes were calculated from the digital elevation model. The solum depth, the thickness of the superficial horizon, elevation, and vertical distance to channel network were the main conditioning factors of the dendrometric variation, wherein taller trees were found in deeper soils, with a thicker surface horizon, in lower areas that are vertically closer to the drainage network. Our results showed that the selection of topographic and morphological variables has a significant effect on the tree height and should therefore be used to select homogeneous areas for the development of the species. In addition, we showed the importance of using an intensive sampling survey to understand dendrometric variation.

ABSTRACT Phosphorus (P) fractionation is a suitable procedure to ascertain P lability in sediments and is able to distinguish sources of P under different soil management practices in a catchment. Brazil is the second largest producer and the largest exporter of tobacco in the world. Inadequate management of cultivated areas exposes the soil to erosion processes, accelerating the transfer of sediment and P to water bodies, which leads to eutrophication. We evaluated the P forms in suspended sediments collected at two rainfall events in the stream of a small catchment in the state of Rio Grande do Sul. The samples were collected upstream and downstream areas in three sub-catchments with different degrees of anthropogenic pressure and in three phases of the hydrograph in the catchment outlet. The first rainfall event occurred during the fallow period, and the second one, during the period of transplanting the tobacco crop. The sediment P forms were evaluated by successive extractions, following the Hedley method. The results showed that an increase in anthropogenic pressure leads to an increase in total inorganic P and a decrease in the levels of organic C and total organic P in sediments. In the control area, the quantity and quality of the eroded material remained the same in both rainfall events. The levels of total P in sediment alone were not sufficient to evaluate the influence of the soil management practices prevalent in each sampling period. However, P fractionation shows that during the tobacco transplanting period, P in sediments was mainly in labile fractions, and rainfall during this period was more likely to promote the eutrophication process. Sediments carried in runoff during the tobacco transplanting period have larger amounts of available P than those borne during rainfall in the fallow period.

RESUMO O setor florestal desempenha um papel importante no contexto socioeconômico e ambiental brasileiro, por isso o avanço no conhecimento sobre os solos florestais torna-se essencial para o uso sustentável dos recursos naturais, seja como base de conservação do patrimônio natural ou como recurso para o desenvolvimento econômico. Solo florestal pode ser definido como aquele cuja pedogênese está associada à influência de uma tipologia florestal ou o que apresenta uma cobertura de floresta natural ou plantada. Diferenciar solos florestais daqueles ocupados com outros usos auxilia na compreensão das possíveis alterações relacionadas à cobertura vegetal e no desenvolvimento de melhores estratégias de manejo para o uso do solo e da floresta. No entanto, ainda não há um consenso em torno do termo, uma vez que o solo apresenta variações de acordo com as características da floresta, estimulando a discussão relativa à sua interpretação e aplicabilidade. A presente revisão de literatura tem por objetivo analisar a utilização do conceito de solo florestal, ressaltando características de diferenciação e sua relação com o tipo de cobertura, natural ou plantada. Aspectos relativos à deposição, qualidade e manejo de resíduos, ciclagem de nutrientes, compactação e produtividade de sítio são enfatizados. Conclui-se que o conceito de solo florestal é amplamente utilizado na literatura específica e útil para o levantamento de informações e de planejamento sustentável de uso do solo e da floresta. A melhoria do conhecimento sobre esse recurso abre a possibilidade de se criar uma identidade comum, o que facilita estudos comparativos de características específicas, fortalecendo a pesquisa em torno do tema.

ABSTRACT The forestry sector plays an important role in the socioeconomic and environmental Brazilian context, therefore the improvement of the knowledge about forest soil becomes essential for its sustainable use as a conservation base of natural heritage as resource for economic development. Forest soil can be characterized by pedogenesis occurred under influence of a forestry typology or under a currently natural or cultivated forest coverage. Differentiating forest soils from those occupied with other uses helps the understanding of possible alterations related to vegetal coverage and the developing of better management strategies to soil and forest use. Nevertheless, there is no consensus about this term because the soils present variations according to the forest characteristics, stimulating the discussion concerning its interpretation and applicability. This review aimed to analyze the utilization of forest soil concept, highlighting the differentiation characteristics and the relation with coverage type, natural or cultivated. Aspects related to deposition, quality and management of residues, nutrients cycling, soil compaction and site productivity are emphasized. The forest soil concept is widely used by specific literature and useful to collect specific information and to plan the sustainable use of soil and forest. The improvement of knowledge about these resources provides the creation of a common identity, supporting comparative studies and consolidating the research regarding to this theme.

A degradação do solo pela arenização no sudoeste do Rio Grande do Sul precisa ser controlada e, para isso, a revegetação é uma técnica eficiente e de baixo custo. A possibilidade de se utilizar uma espécie nativa da região para tais medidas de controle surge como uma alternativa viável do ponto de vista econômico e ecológico. O objetivo deste estudo foi testar a melhor maneira de cultivar Lupinus albescens Hook. & Arn., um tremoço nativo da região, visando à contenção da arenização. O experimento foi conduzido em uma área degradada em Alegrete, Rio Grande do Sul (RS), sul do Brasil. Os tratamentos foram espaçamentos com distância de 17, 34 e 51cm entre as linhas de plantio e número de plantas por metro linear (4, 8, 12, 16 e 20 plantas por metro linear). Os parâmetros analisados foram produção de biomassa na parte aérea, acúmulo de macronutrientes na biomassa da parte aérea, produção de sementes, peso e número de nódulos de fixação biológica de nitrogênio (FBN). Foi realizada análise da variância. Não houve interação significativa entre os dois fatores estudados. O fator espaçamento entre linhas (EL) produziu variação significativa para as diversas variáveis estudadas, com exceção do P acumulado na parte aérea. No caso do espaçamento entre linha, a análise da variância foi complementada por análise de regressão, e o valor para cada característica analisada foi estimado a partir dos modelos matemáticos gerados. O espaçamento entre linhas de 17cm favoreceu a produção de biomassa e o acúmulo de macronutrientes na biomassa da parte aérea, além do peso de nódulos de FBN. O espaçamento de 51cm foi mais eficiente para produção de sementes por planta. Conclui-se que, para plantios de contenção da arenização, o espaçamento de 17cm é mais eficiente, enquanto que, para plantios que objetivam produzir sementes, o espaçamento de 51cm é melhor.

The soil degradation by sandization in the Southwest of Rio Grande do Sul needs to be controlled and, therefore, revegetation is an efficient and low cost technique. The possibility to use a native species from this region for such control measures appears as a viable alternative in economical and ecological terms. The objective of this study was to test the more efficient way to crop Lupinus albescens Hook. & Arn., a native local plant, aiming sandization contention. The experiment was carried out in a degraded area located in Alegrete, RS, Southern Brazil. The treatments were spaced at a distance of 17, 34 and 51cm between rows plantation and number of plants by linear meter (4, 8, 12, 16 and 20 plants in each linear meter). The analyzed parameters were canopy biomass production, macronutrients in canopy biomass, seed production, weight and number of root nodules responsible by biological nitrogen fixation. The analysis of variance analysis was performed and there was no interaction between the factors. The row space produced significant variation for several variables, except for accumulated P in the canopy biomass. The number of plants by linear meter did not interfere on the characteristics analyzed. For the row space, the analysis of variance was complemented by regression analysis and the value for each analyzed characteristic, estimated by mathematical models. The row space of 17cm favored the production and macronutrients accumulation in canopy biomass, besides the weight of FBN nodules. Row space of 51cm was most efficient for seeds production. It was concluded that for crops that aims contention of sandization, row space of 17cm is more efficient, while for crops that aims to produce seeds, row space of 51cm is better.

Em sistemas de produção agrícola que utilizam a irrigação, uma das principais causas da variabilidade dos rendimentos, a disponibilidade de água para as culturas, é controlada. Nesse caso, outros fatores limitantes ao rendimento, relacionados a atributos de solo, passam a ter sua importância aumentada. Com o objetivo de investigar a variabilidade espacial dos principais atributos químicos e do rendimento de culturas, além de determinar os atributos químicos e físico-hídricos do solo em diferentes zonas de rendimento, foram analisadas duas áreas comerciais irrigadas por pivô central, com 51,8 e 58,2 ha, localizadas, respectivamente, em Trindade do Sul (TS) e Palmeira das Missões (PM), no Rio Grande do Sul (RS). As amostragens para caracterização dos atributos químicos foram georreferenciadas seguindo uma malha regular de 100 x 100 m, na camada de 0-0,10 m. Já para investigar a relação entre os atributos químicos e físico-hídricos do solo com os rendimentos obtidos, dada a extensão das áreas, três zonas com distinto potencial produtivo foram estabelecidas, utilizando os mapas de rendimento disponíveis (safras de feijão-preto de 2005/2006 e safrinha de 2006 em TS, e de milho de 2002/2003 e 2003/2004 em PM), obtidos por colhedoras equipadas com sensores de rendimento. Nessas zonas, quinze pontos amostrais foram investigados em cada área nas camadas de 0-0,05, 0,05-0,10 e 0,10-0,20 m. Os atributos químicos do solo foram submetidos à análise de estatística descritiva e geoestatística. Eles apresentaram dependência espacial classificada como forte e moderada, com modelo ajustado à semivariância predominantemente esférico. O P apresentou a maior variabilidade espacial e o pH a menor. Embora manejadas sob irrigação, ambas as áreas apresentaram variabilidade espacial de rendimento. Na zona de baixo rendimento de TS, foram constatadas acidez no solo, baixa saturação de bases e menor capacidade de água disponível, e na de PM foram observadas limitações físicas representadas por compactação por meio dos indicadores densidade, resistência à penetração e macroporosidade. A ocorrência de zonas com menor rendimento das culturas irrigadas nas duas áreas foi associada a limitações químicas e físicas do solo, especialmente em subsuperfície.

Under irrigated agriculture one of the main causes of yield variability, which is the plant-available water, is controlled. In this case, other yield limitations caused by soil attributes become more relevant. To investigate the spatial variability of soil attributes and crop yields, besides the relation between chemical and physical-hydric soil attributes and crop yields of two irrigated commercial plantations (51.8 and 58.2 ha) were studied in Trindade do Sul (TS) and Palmeira das Missões (PM) respectively, in the state of Rio Grande do Sul, Brazil. The soil was sampled from a regular grid of 100 x 100 m in the 0-0.10 m layer for chemical analysis. To investigate the relation between chemical and physical-hydric soil attributes and yields, due to the large area of the plantations, three soil management zones were established based on yield maps available (common bean in 2005/06 and 2006, in TS, and corn in 2002/03 and 2003/04, in PM) recorded by harvesters equipped with yield sensors. In these zones, 15 grid points were sampled in the layers 0-0.05, 0.05-0.10 and 0.10-0.20 m to analyze soil attributes. These underlying soil data, analyzed by descriptive statistics and geostatistics, classified the spatial dependence as strong and moderate, with predominance of the spherical model. Spatial variability was highest for P and lowest for pH. Although both plantations were irrigated there was spatial variability in the yields. In the low-yield zone in TS soil acidity, low base saturation and lower available soil water capacity was diagnosed, while in PM the yield constraints were associated to soil compaction, expressed in the bulk density, soil resistance and macroporosity. The low yield zones of irrigated crops, in both croplands, were linked mainly to chemical and physical limitations in the subsurface.

Os organismos edáficos, por sua sensibilidade a alterações no meio, têm sido utilizados como indicadores de modificações nos níveis de qualidade do solo, as quais podem ser promovidas por degradação ou agradação. Em Alegrete, Rio Grande do Sul, foram caracterizadas populações de organismos edáficos como bioindicadores dos efeitos da degradação por arenização e da recuperação por revegetação com Lupinus albescens Hook. & Arn., fabácea natural do Bioma Pampa. Os tratamentos constituíram-se de solo com cobertura natural de Lupinus albescens (TN), área arenizada que recebeu revegetação com Lupinus albescens há um ano (T1), área arenizada que recebeu revegetação com Lupinus albescens há três anos (T3), solo arenizado (SA) e campo nativo (CN). As coletas foram feitas em fevereiro e maio de 2006, com armadilhas PROVID. Foram determinados os parâmetros: abundância de organismos em nível de Ordem, riqueza de organismos e índices de diversidade e igualdade de Shannon. A arenização reduziu o desenvolvimento das populações edáficas, enquanto a estratégia de revegetação mostrou efeitos positivos na recolonização da área. O grupo Collembola destacou-se como bioindicador dos efeitos dos processos de degradação e recuperação. O índice de diversidade de Shannon não foi adequado para a avaliação dos efeitos da arenização quando analisado isoladamente.

Edaphic organisms are sensible to environment alterations and have been used as indicators of soil quality changes. These modifications can be promoted by degradation or agradation events. The study area is located in Alegrete, Rio Grande do Sul. It was analyzed the role of epigeic soil fauna as bioindicator of soil degradation by arenização and its restoration by revegetation with Lupinus albescens Hook. & Arn., a native fabaceous of Bioma Pampa. The treatments were constituted of soil under natural covering with Lupinus albescens, degraded area recovered with Lupinus albescens by one year (T1), degraded area recovered with Lupinus albescens by three years (T3), degraded area (SA) and native grass field (CN). The sampling was made in February and May of 2006 with PROVID traps. It was determined the abundance of organisms at Order level, the organisms richness, the diversity and evenness Shannon’ index. The process of Arenização reduced the development of sampled edaphic populations, while revegetation showed positive effects in the recolonization of the area. Colembolla group was a good bioindicator of degradation and restoration effects. The Shannon diversity index was not satisfactory to evaluate the edaphic fauna if disconnected of other parameters.