No description available.

Made available in DSpace on 2014-12-17T14:17:55Z (GMT). No. of bitstreams: 1 AneCFS_DISSERT.pdf: 3100120 bytes, checksum: 8f26524545d2044027f402e45324031d (MD5) Previous issue date: 2014-03-17 / This study aimed to establish patterns of dynamics of litter and redistribution of rainfall of Caatinga vegetation. Sampling was done monthly for twenty three months in four areas: degraded, successional primary stage, secondary stage and late stage. We installed 72 collectors of 1.0 mx 1.0 m, with nylon fabric background in three areas. Litter deposited was fractionated into leaves, twigs, reproductive structures and miscellaneous, dried and weighed. To assess the stock of accumulated litter we used metal frame with dimensions of 0.5 mx 0.5 m, thrown randomly and collected monthly, taken to the laboratory for oven drying and weighed. To evaluate the decomposition, 40g of litter were placed in nylon bags (litterbags) mesh 1 mm ?, dimensions 20.0 x 20.0 cm, being distributed on the soil surface and removed monthly, cleaned, dried and weighed. To evaluate the contribution of rainfall we used interceptometers installed 1.0 m above the ground surface, distributed under the canopy of six species of the caatinga, which evaluated the stemflow through collecting system installed around the stems of these species. The deposition of litter in the primary stage was 2.631,26 kg ha-1; 3.144,89 kg ha-1 in the secondary stage; 3.144,89 kg ha-1 in the late stage. The fraction of leaves was the largest contributor to the formation of litter in three stages. The degraded area showed greater accumulation of litter and decomposition has been sluggish during the dry period. We conclude that occurred greater litterfall in later stages. The late successional stage showed faster decomposition of litter, the evidence that is a better use of litter in nutrient cycling processes and incorporation of organic matter to the soil. The time required to decompose 50 % of the litter in the later stages of succession was lower indicating greater speed of release and reuse of nutrients by the vegetation. The specie jurema preta with less leaf area and consists of leaflets, showed greater internal precipitation in rain events of greater magnitude. The stemflow was not influenced by DAP and basal area. The water lost by trapping represented the largest proportion of total rainfall in all species studied / O presente trabalho teve por objetivo estabelecer padr?es da din?mica da serrapilheira e redistribui??o da ?gua da chuva da vegeta??o da Caatinga. Foram realizadas coletas mensais durante vinte tr?s meses em quatro ?reas: degradada, est?gio sucessional prim?rio, secund?rio e tardio. Foram instalados 72 coletores de 1,0 m x 1,0 m, com fundo da tela de n?ilon em tr?s ?reas. A serrapilheira depositada foi fracionada em folhas, galhos, estruturas reprodutivas e miscel?nea, secas em estufa e pesadas. Para avaliar o estoque de serrapilheira acumulada utilizou-se moldura met?lica com dimens?es de 0,5 m x 0,5 m, lan?ada aleatoriamente, sendo coletada mensalmente, levada ao laborat?rio para secagem em estufa e pesadas. Para avalia??o da decomposi??o, 40g serrapilheira, foram colocadas em sacolas de n?ilon (litterbags) malha 1 mm?, dimens?es 20,0 x 20,0 cm, sendo distribu?das na superf?cie do solo e retiradas mensalmente, limpas, secas e pesadas. Para a avalia??o da contribui??o da precipita??o pluvial, utilizou-se intercept?metros instalados 1,0 m acima da superf?cie do solo, distribu?dos abaixo da copa de seis esp?cies da caatinga, onde se avaliou o escoamento pelo tronco atrav?s de sistema coletor instalado ao redor dos caules dessas esp?cies. A deposi??o de serrapilheira no est?gio prim?rio foi 2.631,26 kg ha-1, 3.144,89 kg ha-1 no est?gio secund?rio e 4.542,30 kg ha-1 no est?gio tardio. A fra??o folhas foi a que mais contribuiu na forma??o da serrapilheira nos tr?s est?gios avaliados A ?rea degradada apresentou maior ac?mulo de serrapilheira e a decomposi??o mostrou-se lenta durante o per?odo seco. Conclui-se que ocorreu maior produ??o de serrapilheira nos est?gios mais avan?ados. O est?gio sucessional tardio apresentou decomposi??o da serrapilheira mais r?pida, o que evid?ncia um melhor aproveitamento da serrapilheira no processo de ciclagem de nutrientes e na incorpora??o de mat?ria org?nica ao solo. O tempo necess?rio para decompor 50% da serrapilheira da Caatinga nos est?gios mais avan?ados de sucess?o foi menor indicando maior velocidade da libera??o e o reaproveitamento de nutrientes por parte da vegeta??o. A jurema preta, com menor ?rea foliar e constitu?da de fol?olos, apresentou maior precipita??o interna nos eventos de chuva de maior amplitude. O escoamento pelo tronco n?o foi influenciado pelo DAP e ?rea basal. A ?gua perdida por intercepta??o representou a maior propor??o da precipita??o pluviom?trica total em todas as esp?cies estudadas

<p>Cover cropping is an effective management practice for reducing nitrogen (N) losses to the environment from agriculture fields in the Midwest. Cereal rye (CR; <i>Secale cereale L</i>.) and hairy vetch (HV; <i>Vicia villosa Roth</i>) are two of the most common cover crop species grown in the region. However, limited cover crop adoption in the region is partly due to a dearth of knowledge addressing the effect of cover crops on nitrogen cycling and grain production within corn and soybean conservation cropping systems. The following studies were designed to address knowledge gaps in the current literature regarding the rate, quantity, and timing of cover crop residue C and N release; the fate of CR N following termination; and the effects of cover crops specifically on soybean growth, N assimilation, and yield. Data from this study revealed that growers should be aware that cover crop nutrient release may result in a “tug-of-war” between the soil microbiome and cash crops for soil inorganic-N. Additionally, we observed that CR N is used minimally by the subsequent crop; thus, growers should value CR N as a long-term benefit, such as building SOM. Finally, we found that added pressure from CR during early soybean growth may reduce soybean resilience, and in a wet year result in yield loss.</p>

Made available in DSpace on 2014-12-17T14:33:06Z (GMT). No. of bitstreams: 1 UirandeOC_DISSERT.pdf: 1223777 bytes, checksum: 015d2e9b7467f66c5a5e5e66ec6aa6d6 (MD5) Previous issue date: 2012-02-22 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The decomposition process exercises an extensive control over the carbon cycle, affecting its availability and nutrient cycling in terrestrial ecosystems. The understanding of leaf decomposition patterns above the soil and fine roots decomposition below the soil is necessary and essential to identify and quantify more accurately the flow of energy and matter in forest systems. There is still a lack of studies and a large gap in the knowledge about what environmental variables act as local determinants over decomposition drivers. The knowledge about the decomposition process is still immature for Brazilian semiarid region. The aim of this study was to analyze the decomposition process (on leaves and fine roots) of a mixture of three native species for 12 months in a semiarid ecosystem in Northeast Brazil. We also examined whether the rate of decomposition can be explained by local environmental factors, specifically plant species richness, plant density and biomass, soil macro-arthropods species richness and abundance, amount of litterfall and fine root stock. Thirty sampling points were randomly distributed within an area of 2000 m x 500 m. To determine the decomposition rate, the litterbag technique was used and the data analysis were made with multiple regressions. There was a high degradation of dead organic matter along the experiment. Above ground plant biomass was the only environmental local factor significantly related to leaf decomposition. The density of vegetation and litter production were positively and negatively related to decay rates of fine roots, respectively. The results suggest that Caatinga spatial heterogeneity may exert strong influences over the decomposition process, taking into account the action of environmental factors related to organic matter exposure of and the consequent action of solar radiation as the decomposition process main controller in this region / A decomposi??o exerce um amplo controle sobre o ciclo do carbono, disponibilidade e ciclagem de nutrientes nos ecossistemas terrestres. A compreens?o sobre os padr?es de decomposi??o foliar acima do solo e das ra?zes finas abaixo do solo ? necess?ria e essencial para identificar e quantificar com mais precis?o os fluxos de energia e mat?ria nos sistemas florestais. Ainda h? car?ncia de estudos e uma grande lacuna no conhecimento sobre quais vari?veis ambientais atuam como determinantes locais sobre os controladores da decomposic?o. O conhecimento sobre o processo de decomposi??o ainda ? incipiente para o semi?rido brasileiro. O objetivo do presente estudo foi analisar o processo de decomposi??o (folhas e ra?zes), de uma mistura de tr?s esp?cies nativas durante 12 meses em um ecossistema semi?rido do Nordeste Brasileiro. Tamb?m foi analisado se a taxa de decomposi??o pode ser explicada por fatores ambientais locais, especificamente riqueza de esp?cies, densidade e biomassa a?rea vegetal, riqueza de esp?cies e abund?ncia de macro-artr?podes do solo, produ??o de serrapilheira e estoque de ra?zes finas. Trinta pontos amostrais foram distribu?dos aleatoriamente dentro uma ?rea de 2000 m x 500 m. Para determina??o das taxas de decomposi??o foi utilizada a t?cnica de bolsas de serapilheira (litterbags) e para as an?lises dos dados foram utilizadas regress?es m?ltiplas. Houve uma alta degrada??o da mat?ria org?nica morta. A biomassa a?rea vegetal foi o ?nico fator ambiental local significativamente relacionado ? decomposi??o foliar. A densidade da vegeta??o e a produ??o da serrapilheira foram, respectivamente, positiva e negativa significativamente relacionadas com as taxas de decaimento de ra?zes finas. Os resultados sugerem que a heterogeneidade espacial da Caatinga pode exercer fortes influ?ncias no processo de decomposi??o, tendo em vista a atua??o de fatores ambientais relacionados ? exposi??o da mat?ria org?nica e a consequente atua??o da radia??o solar como controlador do processo de decomposi??o nessa regi?o

Made available in DSpace on 2017-07-10T15:14:37Z (GMT). No. of bitstreams: 1 _Marcos_F_Martins.pdf: 1223784 bytes, checksum: 76c7bc7ba3e56163da07738160894089 (MD5) Previous issue date: 2016-02-26 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / The aim of this study is to evaluate the rate of decomposition of straw on crambe cover crop based on no-tillage system under different soil management practices and usages. We attempt to approach the practice adopted by farmers in the western region of Paraná. The experiment was conducted in the experimental area of the Agronomic Institute of Paraná - IAPAR, regional center of Santa Tereza do Oeste, Paraná, Brazil. The experiment consisted of four soil management practices: Traditional Tillage System - SPDT - Scarified Tillage System - SPDE - Gypsum Agricultural Tillage System - SPDG - and Tillage System with Quality - SPDQ. The treatments were distributed in randomized order on portions subdivided on time with fifteen macro-plots of 20 m x 25 m. The assessments took place on 0 (zero), 7, 15, 30, 60, 90, and 120 days after the harvest of crambe. Decomposition was determined quantitatively by the analysis of the rate of decomposition of crop residues using litterbags. The average loss of phytomass of crambe crop was significantly different (p>0,05), specially for SPDE and SDPG, which had reduction of around 0,63% day-1 and 0,71% day-1, respectively. The longest half-life period was observed on system SPDQ-12, with 66 days. The shortest half-life period was observed on system SPDE, with 45 days. / O objetivo do presente trabalho foi avaliar a velocidade de decomposição da palha em cobertura da espécie do crambe em diferentes usos e manejos do solo com base no sistema plantio direto. Buscou-se aproximar da prática adotada pelos produtores rurais da região oeste paranaense. O experimento foi conduzido na área experimental do Instituto Agronômico do Paraná - IAPAR, pólo regional de Santa Tereza do Oeste, Paraná, Brasil. Os tratamentos foram constituídos de quatro sistemas de manejo do solo, sendo estes: Sistema Plantio Direto Tradicional - SPDT -, Sistema Plantio Direto Escarificado - SPDE -, Sistema Plantio Direto Gessado - SPDG -, e Sistema Plantio Direto com Qualidade - SPDQ. Os tratamentos foram distribuídos de modo inteiramente casualizados em parcelas subdivididas no tempo com quinze macro-parcelas de 20 m x 25 m. As avaliações no tempo ocorreram aos 0 (zero), 7, 15, 30, 60, 90 e 120 dias após colheita do crambe. A determinação da decomposição seguiu-se de forma quantitativa, por meio da análise da taxa de decomposição dos resíduos culturais com o uso de litter bags . A perda média de fitomassa da cultura do crambe foi significativamente diferente (p>0,05) principalmente para o manejo SPDE e SDPG, a qual tiveram reduções respectivamente de 0,63 % dia-1 e 0,71 % dia-1. Para o tempo de meia vida o maior tempo constatado foi no sistema tratamento que continha como manejo o consórcio composto de Aveia preta cabocla + Tremoço branco, com 66 dias, já o menor tempo de meia vida foi observado para o sistema SPDE, com 45 dias. O sistema de manejo influenciou no tempo de meia-vida dos resíduos reduzindo em até 21 dias.