Submitted by Leticia Schettini (leticia@ufrrj.br) on 2016-09-21T13:51:09Z No. of bitstreams: 1 2011 - Alessandro de Paula Silva.pdf: 1644637 bytes, checksum: 98c00f3218ccb86b94b9b0975a7dd573 (MD5) / Made available in DSpace on 2016-09-21T13:51:09Z (GMT). No. of bitstreams: 1 2011 - Alessandro de Paula Silva.pdf: 1644637 bytes, checksum: 98c00f3218ccb86b94b9b0975a7dd573 (MD5) Previous issue date: 2011-02-28 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico - CNPQ / The aim of this work was to evaluate the influence of the position along a toposequence and hillslope form on chemical and physical-hydric soil properties, and their relationship with the natural regeneration of vegetation in areas of abandoned pastures. A total of eight areas in the municipality of Itabora? - Rio de Janeiro State were evaluated. In the shoulder, backslope and footslope positions of the relief toposequence concave and convex slope shapes were identified. Two experimental plots (10 x 20 m) were installed in each section of the toposequence, one for each slope shape, and evaluations related to soil and vegetation type were proceeded. Chemistry and physical-hydric soil characterization was evaluated at 0-10cm depth. Chemical analysis (pH, Al, Ca, Mg, P, K, C e N) and physical hydric attributes of soils based on granulometry, porosity (macro, micro and total porosity), soil bulk density, hydraulic conductivity, and soil mechanical resistance to penetration (RMSP) were carried out. The analysis of vegetation consisted of dry matter evaluation, aboveground regrowth rate of pasture and quantification, and species richness of trees and herbaceous shrubs in natural regeneration. The areas were grouped into 2 based on textural class: Group 1, the clayey areas, and Group 2 medium texture areas. Soil fertility in all the areas showed low levels of sum of bases and base saturation, and high levels of aluminum saturation, which were not influenced by topographic conditions, although the concave slope shape seem to promote the removal of bases. The soil organic carbon and total nitrogen contents were highest on the clayey texture areas. Chemistry and physical-hydric characterization of soil differed among different topographic conditions in medium texture areas, where the shoulder and backslope showed higher porosity (macro and total porosity). The RMSP was not influenced by topographic conditions. More than 90% of the analyzed points showed declivities ranging from 20 and 75 %, reducing values of pH, SB and V (%), and increasing values of m (%). The grass biomass values exceed 10 Mg/ha. The regrowth rate was high showing an average ranging from 984 to 1.356 kg/ha/month, and the clayey areas had lowest values. Low species richness was observed, with greatest diversity of arboreal growth on concave slope; while the herbaceous shrub regeneration tended to be highest in backslope and footslope. The regeneration in terms of species richness was lowest in B. humidicola areas, for both strata and in herbaceous shrub cover. A complementary analysis showed that the geographical orientation of the slopes had a close relationship with the values of natural regeneration, while south-facing slopes showed highest species richness. The backslope in concave slopes showed lowest regrowth in the pasture, and these areas were identified as those with best natural regeneration when compared to other areas studied in this research. / Objetivou-se avaliar a influ?ncia da posi??o na topossequ?ncia e da forma de rampa nas propriedades qu?micas e f?sico-h?dricas do solo e a sua rela??o com o padr?o da regenera??o natural da vegeta??o em ?reas de pastagens abandonadas. Foram avaliadas oito ?reas no munic?pio de Itabora? ? RJ. Nos ter?os superior, m?dio e inferior da topossequ?ncia foram identificados rampas de forma c?ncava e convexa. Foram instaladas duas parcelas (10 x 20 m) em cada ter?o, uma para cada forma de rampa, onde se procederam as avalia??es quanto ao solo e vegeta??o. O solo foi avaliado quanto ?s suas caracter?sticas qu?micas e f?sico-h?dricas ? profundidade de 0 a 10 cm. Foram realizadas as an?lises qu?micas de pH, Al, Ca, Mg, P, K, C e N e as an?lises f?sico-h?dricas de granulometria, porosidade (macro, micro e total), densidade do solo, condutividade hidr?ulica e resist?ncia mec?nica do solo ? penetra??o (RMSP). A an?lise da vegeta??o consistiu na avalia??o da mat?ria seca e taxa de rebrota da parte a?rea da pastagem e da quantifica??o e riqueza da vegeta??o arb?rea e herb?ceoarbustiva da regenera??o natural. As ?reas foram agrupadas em duas de acordo com a classe textural: Grupo 1, ?reas de textura argilosa, e Grupo 2, ?reas de textura m?dia. A fertilidade do solo de todas as ?reas apresentou n?veis baixos de soma e satura??o de bases e n?veis altos de satura??o por alum?nio, n?o sendo influenciadas significativamente pelas condi??es de relevo, embora as formas de rampas c?ncavas pare?am promover uma maior remo??o de bases. Os teores de carbono e nitrog?nio total foram maiores nas ?reas de textura mais argilosa. As caracter?sticas f?sico-h?dricas do solo diferiram em fun??o das condi??es de relevo somente nas ?reas de textura m?dia, onde os ter?os superior e m?dio apresentaram maior porosidade (macro e total). A RMSP n?o foi influenciada pelas condi??es de relevo. Mais de 90% dos pontos analisados apresentaram declividades entre 20% e 75 % favorecendo diminui??es nos valores de pH, SB e V(%) e aumentos nos valores de m (%). Foram identificadas tr?s esp?cies de gram?neas predominantes nas pastagens (Brachiaria decumbens, Brachiaria humidicola e Paspalum sp.), com predomin?ncia da esp?cie Paspalum sp. Os valores de biomassa de gram?neas apresentaram-se altos superando 10 Mg/ha. As taxas de rebrota foram elevadas apresentando em m?dia valores entre 984 a 1.356 kg/ha/m?s, sendo os menores valores encontrados nas ?reas argilosas. Observou-se baixa riqueza de esp?cies e tend?ncia em maior domin?ncia arb?rea na rampa c?ncava, enquanto que a regenera??o herb?ceo-arbustiva tendeu a ser maior nos ter?os inferior e m?dio. A regenera??o foi menor em ?reas de B. humidicola, em termos de riqueza de esp?cies, nos dois estratos e para cobertura herb?ceo-arbustiva. Uma an?lise complementar mostrou que a orienta??o geogr?fica das encostas possuiu estreita rela??o com os valores de regenera??o natural, sendo que encostas voltadas para o sul apresentaram maior riqueza de esp?cies. Os ter?os m?dios de rampas c?ncavas apresentaram o menor vigor de rebrota do capim. Essas ?reas foram tamb?m identificadas como aquelas com a maior regenera??o natural dentre as ?reas estudadas.