Search

As variedades tradicionais de milho cultivados pelos agricultores familiares constituem-se em fonte de variabilidade genética e são fundamentais para segurança alimentar. Assim, o presente trabalho tem como objetivo, avaliar, com base em componentes físicos e químicos, o comportamento da variabilidade genética de milho tradicional cultivadas em terra firme e praia, na regional Vale do Juruá, estado do Acre. As características constaram da determinação de matéria seca, material mineral, proteína bruta, extrato etéreo, energia bruta, fibra em detergente neutro, amido e digestibilidade in vitro da matéria seca, vitreosidade e densidade dos grãos. Os dados foram analisados mediante estatística descritiva, associado à análise multivariada de componentes principais (PCA), com auxílio do software R. Por meio da PCA, as variedades cultivadas em terra firme e praia formaram 3 grupos distintos, na qual a vitreosidade nos grãos variou de 73,7% a 79,46%, de modo que, as variedades de grãos avermelhadas apresentaram maior presença de endosperma vítreo e maior densidade, havendo uma correlação forte e positiva entre essas variáveis. Já as variedades de grãos amarelas e amarelas-oranges apresentaram maior aderência a energia, amido e maior digestibilidade. Portanto, as variedades tradicionais cultivadas em terra firme e praia, apresentam variações em relação as análises físicas e químicas. Palavras-chave: valor nutricional; recursos genéticos; conservação on farm.

Amazonian biodiversity has been used for generations by human populations, especially by Indigenous peoples and traditional communities in their cultural, social and economic practices. However, forest degradation, driven by forest fires, has threatened the maintenance of these resources. This study examined the effects of recent forest fires on species with timber, non-timber and multiple-use potential in Brazil’s state of Acre. Forest inventories in five forest types were analyzed, identifying species with timber, non-timber and multiple-use potential based on a review of existing scientific articles, books and studies in the technical literature. The indicators of the effect of forest fires on species density were based on the mean and standard deviation of tree density and absolute abundance. We found that 25% of the tree individuals have potential for use by humans, 12.6% for timber, 10.7% non-timber and 1.4% have multiple-use potential. With the negative impact of fire, the reduction in timber, non-timber and multiple-use potential can range from 2 to 100%, depending on the vegetation type and especially on the recurrence of fire. However, even in forests that are degraded by fire, species that are useful to humans can be maintained to a certain degree and contribute to other environmental services, thus they must be preserved.

The diversity of soils and environments in the Amazon demands studies that improve the information with regard to their use and management. The objective of this study was to characterize the morphological, physical and chemical attributes of soils originating from the Cruzeiro do Sul Formation, in the Juruá Valley, Acre. Five geological profiles were selected and physical (granulometry) and chemical analyses (pH in H2O, K+, Ca2+, Mg2+, Al3+ and organic matter) were conducted, and samples of horizons and related layers were obtained. The soils showed intense deepening of the mantle of weathering, with predominance of orange and yellowish colors associated with 5 YR, 7.5 YR and 10 YR hues. Sandy clay-sandy texture was predominant, with higher proportions of fine sand at subsurface level. Acidity ranged from medium to high, with pH between 4.6 and 5.2. The levels of exchangeable bases were low, indicating the chemical poverty of the source material associated with sandy texture. The sandy texture also reflected in low levels of organic matter. Al3+ contents reached 12.05 cmolc.dm-3, which may generate phytotoxicity for plant development. CTC showed a positive correlation with Al3+ and exchangeable acidity. The soils originating from sediments of the Cruzeiro do Sul Formation present low natural fertility.

Abstract The Climatological Water Budget (CWB) determined by the Thornthwaite and Matter (1955) allows the temporal visualization of the variables that compose the climate, thus allowing the climatic characterization of a region. Therefore, this work aimed at identifying and quantifying the months of water surplus and deficit through CWB to characterize the climate for the municipality of Cruzeiro do Sul - AC, Brazil, and analyze the temporal distribution of rainfall for the municipality. We used daily precipitation and temperature values and procedures to fill in the database. We calculated the potential evapotranspiration (ETP) using the Hargreaves Samani method (1985). Subsequently, we determined the periods of soil water storage (SWS), water deficiency (DEF), and water surplus (SUR) on a monthly scale. The climate of Cruzeiro do Sul, located in the northern region of Brazil, was characterized according to the Thornthwaite (1955) as B1rA'a' for a AWC of 140 mm, that is, a humid climate with annual rainfall average of 2227 mm and real evapotranspiration of 1660 mm, with small water deficiency in the months from June to October, with no thermal deficiency, and summer concentrated in three months with an average air temperature of 25 °C ranging between 18 °C and 32 °C.

Cratylia argentea is a multi-purpose shrub with potential as a source of protein for livestock, but is rarely used in production units. This study aimed to monitor the establishment of a stand of this plant in a sandy Ultisol (Red-Yellow Argisol), in an area of 4,000 m2 on a rural property in Cruzeiro do Sul, Acre, Brazil, comparing 2 planting methods: (i) transplanting seedlings (78 in total); and (ii) direct seeding (3,820 seeds in 1,910 pits). The existing pasture was sprayed with glyphosate before planting C. argentea. Subsequently, herbicide and mechanical methods were used to control weeds, while fertilizer was applied and the area was mulched. In the first year after planting, activities performed and inputs were recorded along with costs in order to create a reference model for those intending to cultivate this species in the humid tropics. At 10 months after planting, average height of plants was 162 cm (range 70‒240 cm) with no effect of planting method. Ninety-seven per cent of plants established from seedlings survived, while 81% of pits established from direct seeding in the field had surviving plants. The cost of establishing a hectare of C. argentea was US$ 1,654.17, with 85.8% of the cost for labor and only 14.2% for other inputs, although costs of producing seedlings and hand-planting them were not considered. Studies to develop planting systems using less labor seem warranted.

This work morphometrically characterized watersheds that occur in the municipality of Xapuri and constructed a model that explains the extent of watershed impact and resilience. Emphasis was given to provide a decision-making tool for non-specialists. The study area is located in the State of Acre and has four sub-basins: Alto Acre, Rio Xapuri, Xipamanu and Riozinho do Rola. A cartographic survey was conducted, to include the morphometric characteristics of the area and land use and cover features that resulted in the soil-hydrographic zoning of the municipality. Sub-basins Xapuri, Xipamanu and Riozinho do Rôla revealed drainage densities and orders that indicate low drainage efficiency, while Alto Acre presented high drainage orders (ninth order) and densities, contrary the geometric indices and drainage densities, and is considered to have efficient drainage. Considerable alterations in permanent preservation areas occur in the municipality of Xapuri, with conversion to less resilient areas highly sensitive to impacts. The soil-hydrographic zoning assists in visualizing the municipality in a land management context through an ecosystem approach and a qualitative view of the possibilities and weaknesses.

O presente estudo avaliou as consequências do desmatamento e a utilização do solo com Brachiaria brizantha em relação ao estoque e dinâmica de C e frações húmicas em duas floresta-pastagem no Acre. A primeira localizada sequências município de Rio Branco em área de Floresta Aberta com bambu e palmeira e duas pastagens de B. brizantha de 3 e 10 anos com predomínio de Argissolo Vermelho-Amarelo alítico plíntico. O segundo situado no município de Senador Guiomard em área de Floresta Densa e pastagem de B. brizantha de 20 anos em Latossolo Vermelho-Amarelo distrófico. Em cada local foram coletadas, em triplicata, amostras de solos nas profundidades de 0-5, 5-10, 10-20 e 20-40 cm. Nestas amostras foram avaliadas as características físico-químicas, o C das substâncias húmicas e da matéria orgânica leve, e a composição isotópica do solo e das respectivas frações orgânicas até 1 m de profundidade, determinando o percentual de C derivado da pastagem e da floresta. Houve incremento nos estoques de C do solo e nos valores de δ13C do solo com o tempo de utilização da pastagem, em ambas as sucessões. A porcentagem de C derivado de pastagem foi expressiva na camada superficial do sistema com 20 anos de uso, com proporções que chegaram a 70% do C total. Os valores de δ13C para os ácidos húmicos variaram de -12,19 a -17,57 ‰, indicando maior proporção de C derivado da pastagem. A estabilidade estrutural da MOS, inferida pela relação humina com as frações ácido fúlvico e ácido húmico (HUM/FAF+FAH), tenderam a diminuir nos ecossistemas de pastagem quando comparada com as florestas naturais.This study evaluates the impacts of converting natural Amazonian forests in Brazil to pasture dominated by Brachiaria brizantha concerning to C dynamics and humic fractions in two soil chronosequences in the Acre State, Brazil. The first site, dominated by Plinthic Red Yellow Argissols (Ultisols), is located in the municipality of Rio Branco and comprises an area of bamboo- and palm-dominated open forest with two B. brizantha pastures of 3 and 10 years old. The second site, dominated by a dystrophic Red Yellow Latosol (Oxisol), is located in the municipality of Senador Guiomard and comprises an area of dense forest and a 20-year old B. brizantha pasture. In each site soil samples were collected in triplicate at depths of 0-5, 5-10, 10-20 and 20-40 cm. Samples were evaluated for physical and chemical characteristics, C of humic substances and light organic matter, and the isotopic composition of soil and its organic fractions to 1 m depth, determining the percentage of C derived of both grassland and forest. There were increases in stocks of soil C and δ13C soil with the time of grazing in both sites. The percentage of C derived from pasture was much higher in the surface layer of the Senador Guiomard site following 20 years of grazing, with proportions that reached 70% of the total C. δ13C values for the humic acids ranged from -12.19 to -17.57 ‰, indicating a higher proportion of C derived from pasture. The MOS structural stability inferred by the relationship of the humin with both fulvic acid and humic acid fractions (HUM / FAF + FAH) tended to decrease in grassland ecosystems when compared with native forests.