Sebastião Fonseca

Perdas de solo e água por erosão hídrica em sistemas florestais na região de Aracruz (ES)

SUMMARY : SOIL AND WATER LOSSES BY EROSION IN FORESTECOSYSTEMS IN THE REGION OF ARACRUZ, STATE OFESPIRITO SANTO, BRAZIL Soil and water losses by erosion were measured in forest ecosystems and were relatedto the calculated maximum tolerable soil losses. Main soil classes in the Coastal Plains ofthe region of Aracruz (ES) were studied, with the aim of obtaining indicators of managementadequacy for this production system. The experimental plots were set on loamy/clayeyYellow Argisol (PA1), Haplic Plinthosol (FX), and moderately rocky Yellow Argisol (PA8).The slopes ranged from 2-8 %, 1-12 %, and 29-36 %, for each soil class. Three soil coverswere studied of each soil class: eucalyptus trees, native forest, and bare soil. Soil and waterlosses under eucalyptus followed the order: PA8 > PA1 > FX. Water losses ranged from 9-70 mm, equivalent to 1-6 % of the total annual rainfall. Soil losses in the eucalyptus plotslay well below the calculated maximum tolerable soil losses in all soil classes, which indicatesadequacy of management in this production system regarding water erosion. The fact thatsoil losses in eucalyptus were relatively close to those in native forest indicates thesustainability of the former environment regarding erosion.Index terms: Ultisol, Plinthosol, erosion, eucalyptus, native forest, bare soil.

Valores de referência para macronutrientes em eucalipto obtidos pelos métodos DRIS e chance matemática

Data from 1.213 trees of Eucalyptus grandis x E. urophylla hybrids were collected between 1988 and 1994 from the Aracruz Celulose S.A. commercial plantation in the State of Espirito Santo, Brazil. Data on stand productivity and macronutrient concentration in four tree components (leaf, branch, stembark and stemwood) were used to determine the reference values of nutrient concentration by the methods of Mathematical Chance and DRIS. The formula of Jones and the population distribution based on age and selection of the relation between elemental concentrations by the F test were used in the calculation of DRIS indices. Critical levels were obtained using the DRIS method, by the following processes: determining the mean nutrient concentration in the nutritionally balanced and productive (optimum critical level) eucalypt stands; and by graphs (critical-level graph). The mean concentration proved to be a promising method, even when compared to the Mathematical Chance method. This latter method was appropriate mainly for the determination of the optimum range, which could be used as minimum and maximum limits for the range of nutrient sufficiency in productive trees.

Atividade microbiana, carbono e nitrogênio da biomassa microbiana em plantações de eucalipto, em seqüência de idades

SUMMARY : ACTIVITY, CARBON AND NITROGEN OF MICROBIAL BIOMASSIN EUCALYPT PLANTATIONS IN AN AGE SEQUENCE Microbial activity is highly relevant for nutrient cycling and soil fertility in forestplantations. Due to the long growth cycles, continuous litter production and dead rootscontribute to storage and increase of soil organic matter. Changes in soil and litter microbialbiomass and activity under 1, 3, 5 and 13-year-old eucalypt plantations were evaluated.Soil and climate conditions were the same at the sites. Microbial biomass C and N werehigher in litter than in soil. Then, litter could be an important sink of microbial C and N ineucalypt plantation. No increase or drop in microbial biomass and activity was observedas plantations grew older, probably because the soil and litter samples were from reformedplantations. Litter quality had a direct influence on litter microbial activity and microbialbiomass C and N. Organic carbon and N content were the most reliable indicators to showchanges in the soil under eucalypt plantations, while in the litter it were the microbialattributes and cellulose, lignin, and N content.Index terms: organic matter, nutrient cycling, forest soils.

ESTOQUES DE CARBONO E NITROGÊNIO NAS FRAÇÕES DA MATÉRIA ORGÂNICA EM ARGISSOLO SOB EUCALIPTO E PASTAGEM

The cultivation of eucalyptus in areas of pasture has resulted in changes of C and N storage in soil, mainly due to the different characteristics of each plant and their biomass management; the largest stock of C and N can be found under eucalyptus, originating from the biomass at the soil surface layer and increasing the C/N in decomposition of plant residues. These differences may cause a decrease in the storage of C and N fractions in the chemical, physical and biological soil, both in the more labile, an the more recalcitrant fractions. This study aimed to evaluate the stocks of total organic carbon (TOC) and total N (TN), the stock of C and N in humic substances (fulvic acids, humic and humin), the light fraction (C-MOL and N-MOL) and the microbial biomass (C-BM and N-BM) in samples of collected from the layers 0-0.10, 0.10-0.20, 0.20-0.40, 0.40-0.60 and 0.60-1.00 m in depth, line (EL) and interline (EEL) from the soil under eucalyptus in the fourth rotation with six years of age, and from an area of cultivated pasture with Brachiaria (P). The total organic carbon stock and carbon in the light fraction in the first layers of soil (0.60 m) was higher in the interline of eucalyptus compared with that from the cultivated pasture and the line of eucalyptus, probably favored by harvest residue from the previous cycle of eucalyptus buried in the current interline. By determining the natural abundance of 13 C in the 0-0.20m soil, it was found that 29% and 37% of carbon present in the soil organic matter (SOM) after 28 years of cultivation in the line and interline, respectively, was derived from eucalyptus (C 3 plants), which corresponded to an average rate of cycling of SOM in this soil of 1.04% (line) and 1.32% (interline) per year. In the soil interline it was observed that the C-C 3 from the eucalyptus increased the stock of soil organic C, even with the replacement of C-C 4 from the pasture, after 28 years of eucalyptus cultivation. For nitrogen in humic substances, a similar stock was obtained for the soil of the interline of eucalyptus and that of the pasture, which was higher than that of the soil line of eucalyptus, up to 1 m deep. The soil of eucalyptus (EL and EEL) showed a stock of C and N in microbial biomass similar to that of cultivated pasture.

Detailed soil survey of an experimental watershed representative of the Brazilian Coastal Plains and its practical application

This paper presents a detailed soil survey of an experimental watershed with representative pedoclimatic characteristics of the Coastal Plains in Espirito Santo State and its practical applications. For the pedological survey, 35 observation sites and three soil profiles were sampled and described, which were morphologically characterized and subjected to physical (particle size) and chemical analyses (routine and sulfuric acid digestion). The soil map was made using the geographic information system ArcGIS 9.3. This GIS software was also used to generate the digital elevation model (DEM) for identifying the slope classes. SAGA software was used to calculate the topographic wetness index (WI) which aided in a more accurate separation of Haplic Organosol from other soils. The predominant soil class in the watershed was the dystrophic/dystrocohesive Yellow Argisol (97%), containing morphological, chemical and physical characteristics representative of the most expressive Coastal Plains soils. Geoprocessing tools and techniques aided to make the watershed soil map.

BIOMARCADORES DERIVADOS DE PLANTA E DE MICRORGANISMOS EM SOLOS DE TABULEIROS COSTEIROS CULTIVADOS COM EUCALIPTO E ACÁCIA

Changes in the management systems for the cultivation of different forest stands and the use of species rotation can lead to alterations in the quality of soil organic matter (SOM) and plant residue deposition. This study evaluated the stage of decomposition and the contribution of plant and microbial origin for SOM through biomarkers, such as lignin-derived phenols, carbohydrates and amino sugars in continuous short rotation eucalypt ( Eucalyptus urophylla x Eucalyptus grandis hybrid) (seven years) compared to a rotation system including acacia ( Acacia mangium Willd.) after short-rotation eucalypt; and long-rotation eucalypt (24 years). A native vegetation (Atlantic Forest) was used as a reference for the original site condition representative for the northern coast of Espirito Santo state. To do so, we estimated the content of total organic C (TOC), total N (TN) and the contents of lignin-derived phenols (VSC), the carbohydrates and the amino sugars derived from soil microorganisms, and acids/aldehyde ratio of groups vanilil ((Ac/Al)vanilil) and syringyl ((Ac/Al)syringyl) of the lignin, hexoses/pentoses (H/P) ratio of carbohydrates, besides glucosamine/muramic acid (Gluc/Ac. Mur) and glucosamine/galactosamine (Gluc/Gal) ratios for soil and litter samples. The results indicated that litter of the continuous short-rotation eucalypt has greater dry mass, lignin (VSC) and carbohydrates contents, C/N and VSC/N ratios; a similar proportion of coarse litter to fine litter and C content, but a lower N content in comparison to the species rotation system that includes the leguminous acacia. In the soil, acacia cultivation increases C, N and carbohydrates content, widened the acid/aldehyde ratio of vanilil groups of lignin and the glucosamine/muramic acid ratio of amino sugars derived from microbial activity. The longer rotation of eucalypt (24 years) increased C content and decreased the VSC/N ratio in SOM compared to the continuous short-rotation eucalypt, but still having C and N content lower than in soil of acacia and native forest. The smallest Ac/Al ratio of lignin-derived phenols in soils cultivated with eucalypt (in long and short-rotation) indicates that the SOM is in less advanced stage of decomposition (humification) than in the soil cultivated with acacia, and that under native forest. In soils under acacia, followed by that of short-rotation eucalypt, the higher glucosamine/muramic acid ratio suggested a greater contribution of fungi in SOM cycling, whereas in the native forest and long-rotation eucalypt there is greater abundance of bacteria-derived compounds. Overall, the results indicate that there was a recovery in the quality of the soils cultivated with eucalypt for a longer rotation and also with acacia in relation to the continuous short-rotation eucalypt.

BALANÇO HÍDRICO E DE ENERGIA PARA PLANTIOS DE EUCALIPTO COM COBERTURA PARCIAL DO SOLO

Plantios com idade inicial de desenvolvimento apresentam descontinuidade na cobertura do solo, tendendo a apresentar maior exposicao do dossel ao vento e a radiacao solar, o que altera as interacoes solo-plantaatmosfera. O objetivo deste trabalho foi estudar os componentes dos balancos hidricos e de energia ao longo do primeiro ano de desenvolvimento do eucalipto na regiao da planicie costeira brasileira. O sitio experimental esta localizado em uma area pertencente a empresa Fibria Celulose no municipio de Aracruz- ES. O espacamento entre as arvores do plantio de eucalipto da area estudada foi de 3 x 3 m e a data do plantio foi em 15/08/2004. O periodo de estudo foi compreendido entre a data do plantio ate a cultura ter completado 19 meses de idade. Verificou-se maior disponibilidade de energia no periodo de verao e que a precipitacao influenciou diretamente na particao do balanco de energia, sendo que, durante todo o periodo estudado, a fracao da energia disponivel destinada a evapotranspiracao foi sempre maior que a fracao destinada ao aquecimento do sistema solo-planta-atmosfera, apresentando uma relacao de 59,57% de λE/R. Observou-se tambem que o balanco hidrico com a evapotranspiracao modelada apresentou boa correspondencia ao comportamento da umidade observada, apresentando um coeficiente de determinacao de 0,94. Os maiores portes das arvores, maiores indices de area foliar e sistema radicular, favoreceu a evapotranspiracao, mostrando que a maior parte da energia disponivel foi utilizada para mudanca de fase da agua.

FENÓIS DERIVADOS DA LIGNINA, CARBOIDRATOS E AMINOAÇÚCARES EM SERAPILHEIRA E SOLOS CULTIVADOS COM EUCALIPTO EM SISTEMAS CONVENCIONAL E FERTIRRIGADO

The study aimed to evaluate the content of phenols derived from lignin, carbohydrates, amino sugars, the stage of decomposition of compounds and the relative contribution of plant-and microbial-derived compounds to the soil organic matter (SOM) in the conventional and fertirrigated till age of eucalyptus. Samples of litter and soil (Ultisol) were taken from two tillage systems (conventional and fertirrigated) at two collection sites (line and between-line) with three replications. It was evaluated the litter production, content of total organic C (TOC), total N (TN), lignin and phenols-derived lignin and its Ac/Alratio, carbohydrates and their hexose/pentose ratio, amino sugars and the glucosamine/muramic acid ratio in the soil. The cultivation of eucalyptus in fertirrigated system promoted higher litter fall, reduced the carbohydrate content and maintained the content of lignin in the litter in comparison to the conventional system. In soil, the greater accumulation of the litter (22%) in fertirrigated system increased the contents of carbohydrates, lignin and amino sugars, mainly in the between-lines position. The hexoses/pentoses ratio also increased, indicating a greater presence of compounds of microbial origin. Among the compounds of microbial origin, a larger abundance of glucosamine was observed, indicating a greater contribution of fungal to the SOM formation under fertirrigated cultivation.

ABUNDÂNCIA NATURAL DE 15N E FORMAS DE NITROGÊNIO EM ARGISSOLO CULTIVADO COM EUCALIPTO E ACÁCIA

The nutrients nitrogen and one of the most demanded by plant species, and its presence in soil under organic or mineral forms available to plants is linked to quality and quatity of plant residues added to the soil. The study aimed to evaluate the influence of cultivation of eucalyptus and acacia in the composition of organic and inorganic N forms and the natural abundance of 15N in an Ultisol. For this, we collected soil and litter samples in continuous short-rotation eucalypt (Eucalyptus urophylla x Eucalyptus grandis hybrid) (seven years) compared to a rotation system including acacia (Acacia mangium Willd.) after short-rotation eucalypt; and long-rotation eucalypt (24 years). A native vegetation (Atlantic Forest) was used as a reference for the original site condition representative for the northern coast of Espirito Santo state. To do so, we evaluated the content of total organic C, total N, N-NH4 +, N-NO3 -, C/N ratio, fractionation of organic N and 15N natural abundance in soil and litter. Among the forms of organic-N hydrolyzed, the N-amino was the fraction with the highest contribution of organic N (39%), followed by the fraction of N-unidentified (27%), the fraction of N-amide (18%) and N-hexosamine (15%). The acacia plantation presented smaller natural abundance of 15N and higher levels of total N and soil organic C, and increased organic forms of N-hydrolyzed, when compared to the eucalyptus short-rotation soil. This indicates the increase of labile N-organic forms in the soil for the plants and reduction of humification of soil organic matter (SOM) of acacia. Thus, the crops rotation with acacia after eucalyptus contributed to the increase of organic forms in the soil, important for the nutrition of plants, because they are potential sources of nutrients to the plants in a short-time period.

Estoques de carbono e nitrogênio em frações da matéria orgânica de solos cultivados com eucalipto nos sistemas convencional e fertirrigado

The objective of this study was to evaluate the C and N stocks in fractions of labile and more stable SOM fractions in response to intensification of forest cultivation through fertirrigation when compared to conventional stands. To that end, two areas planted with eucalyptus in the same (Ultisol), but with different managements (fertilized and irrigated and conventional system) were sampled in the 0-10, 10-20, 20-40, 40-60 and 60-100cm deep soil layers in line and interrow of the cultivation. The sampling interrow soil was justified by the ridged and burial of plant residues from previous crop cultivation in-between the substrate. At seven years old, eucalypt under fertirrigation increased the litterfall and the C and N stocks in the most labile and stable SOM fractions, leading to greater stocks of C and N in the 0-100 cm deep soil layer. The increments due to fertirrigation observed for total C was 50.34 and for the labile fraction was 5.62t ha-1. The eucalypt interrow soil, especially in the fertirrigated treatment, presented larger stocks of total C and N and also larger C stocks in humic substances and light fraction of SOM possibly due to greater deposition and incorporation of vegetable residues from the previous cycle in the interrow current cultivation. The intensification of water and nutrients usage in short-rotation eucalypt stands is an alternative to increase the deposition of vegetable residues and C sequestration in more stable and labile SOM fractions, especially in the 0-40cm soil layer.