Arbuscular mycorrhizal fungi activity in the rhizosphere of tree seedlings subjected to residual herbicides

Trees occurring on the margins of agricultural areas can mitigate damage from residual herbicides. Rhizospheric microbial activity associated with trees is one of the main remedial capacity indicators. The objective of this study was to evaluate the rhizospheric microbiological activity in tree species subjected to the herbicides atrazine and sulfentrazone via the rhizosphere. The experiment was designed in four blocks and a 6 × 3 factorial scheme. The first factor consisted of six tree species from Brazil and the second of atrazine, sulfentrazone, and water solutions. Four herbicide applications were performed via irrigation. The total dry mass of the plants, mycorrhizal colonization, number of spores, basal respiration of the rhizospheric soil, and survival rate of bioindicator plants after phytoremediation were determined. Trichilia hirta had higher biomass when treated with atrazine and sulfentrazone. Herbicides decreased the microbial activity in Triplaris americana and did not affect the microbiological indicators of Myrsine gardneriana, Schizolobium parahyba, and Toona ciliata. Fewer bioindicator plants survived in soil with Triplaris americana and sulfentrazone. Microbiological indicators were influenced in different ways between species by the presence of herbicides in the rhizosphere.

Efeito da intensidade de luz no desenvolvimento vascular e na qualidade de mudas de Paricá

A luz é um fator ambiental essencial no crescimento de plantas. Por isso, este estudo objetiva analisar a influência da intensidade luminosa no desenvolvimento vascular e na qualidade de mudas de paricá (Schizolobium parahyba var. amazonicum Huber ex Ducke). As mudas foram alocadas sob pleno sol, baixa, média e alta intensidade de sombreamento (0%, 25%, 50% e 75% de sombreamento, respectivamente). Foram medidos o diâmetro, a altura, o índice SPAD, a produção de biomassa e o desenvolvimento vascular do caule (xilema, câmbio e floema). Calculou-se ainda o índice de qualidade de Dickson (IQD). Os maiores valores de produção de biomassa, desenvolvimento vascular e IQD foram encontrados nas mudas cultivadas sob baixa intensidade de sombreamento. Concluiu-se que a intensidade de luz influencia os parâmetros de crescimento em paricá, e que o desenvolvimento vascular do caule e os atributos morfológicos apresentam correlação direta, explicando o crescimento radial e o aumento da qualidade das mudas, que foi otimizado nas mudas cultivadas sob baixa intensidade de sombra. Portanto, a melhor qualidade de mudas e produção xilemática pode ser alcançada por mudas de paricá quando cultivadas sob baixa intensidade de sombreamento.

Cellulose acetate obtained from Schizolobium parahyba (vell.) blake wood

Currently, non-biodegradable polymers are produced on a large scale and cause several environmental problems, especially due to their low degradation. Cellulose acetate is a non-toxic, low-flammable and low-cost polymer, playing an important environmental role. The objective of this study was to synthesize cellulose acetate membranes from Schizolobium parahyba wood (“guapuruvu”) with particles sizes of 20 and 60 mesh. The materials were submitted to acetosolv pulping, bleaching and acetylation to produce the acetates. The yields and the degree of substitution were found. The fibers were chemically characterized and the samples obtained at each processing step were analyzed by FTIR. It was possible to prepare acetates from both granulometries wood. The FTIR analysis showed changes on the samples’ bands, indicating that the chemical processes were efficient. Cellulose acetate obtained from the 60 mesh material presented a higher degree of substitution (2.74 ± 0.12) when compared to the 20 mesh acetate (2.59 ± 0.13), showing that the particle size of the material influenced on the efficiency of the acetylation reaction. DMA tests have demonstrated that the 60 mesh membrane has higher flexibility and transparency when compared to the 20 mesh membrane.

ANATOMY AND DRYING OF WOOD OF FOUR SPECIES FROM AN AGROFORESTRY SYSTEM

Drying is an important process in the generation of wood products, as it increases the quality of the final products; however, it is influenced by various anatomical characteristics. The aim of this study was to evaluate the influence of anatomy on the drying of wood of Parapiptadenia rigida (Benth.) Brenan, Peltophorum dubium (Spreng.) Taub., Eucalyptus grandis W. Hill × Eucalyptus urophylla S.T. Blake (hybrid), and Schizolobium parahyba (Vell.) Blake trees from an agroforestry system. Three trees aged 9 years were sampled for each species. The trees were removed from the study region when their diameter at breast height (DBH) was 1.30 m from the ground. Blocks were made with dimensions of 5.0 × 5.0 × 15.0 cm for the evaluation of oven drying and 1.5 × 1.5 × 2.0 cm for anatomical features. S. parahyba has the highest value of fiber diameter (35.1 µm) and lumen diameter (27.6 µm), whereas P. dubium had the highest value of cell wall thickness (6.8 µm). The average equilibrium moisture content was 10.98% after 40 days of drying. The anatomy of the wood influenced the drying of the four species intensity, which was related to humidity during all periods. The anatomical parameters that most influenced drying were fiber diameter (Pearson correlation coefficient: 0.77), lumen diameter (0.76), and fiber cell wall thickness (0.73); the higher the values, the greater was the drying intensity.

Forest restoration after alluvial gold mining can recover vegetation structure. A case study in Colombia

Technical reclamation and spontaneous succession (passive restoration) are the two main approaches for restoring post-mining sites worldwide. Despite substantial differences between both approaches, little is known regarding how they differ in terms of ecological outcomes. We assessed and compared the vegetation structure and composition in one spontaneous succession forest that is 29 years old, two technically reclaimed forests that are 2 and 10 years old after alluvial gold mining, and one old-growth reference forest in northeastern Antioquia, Colombia. We sampled trees and saplings establishing three Modified-Whittaker Plots in each site. We measured tree basal area, canopy cover, vegetation height, tree density, and species richness. Vegetation structure and composition differed considerably among restoration approaches. Species richness was significantly greater in the spontaneous succession forest than at the other sites. Similarly, technical reclamation significantly increased the vegetation attributes after 10 years, reaching values similar to the reference forest. We underscore the importance of fast-growth planted species (Acacia mangium, Samanea saman, and Schizolobium parahyba) to revegetate mining degraded lands.

Tetragonisca angustula resin gathering behaviour of Schizolobium parahyba

Tetragonisca angustula is a very important stingless bees species. This study aimed to report the resin gathering behaviour of this species of a possible new resin source: Schizolobium parahyba. Evaluations of temperature, number of bees in gathering activity, time and season were used to characterize bee’s behaviour. Resin gathering activities were concentered between 10 and 14 hours, with a moderate linear positive correlation index with the temperature. No bee activity was observed when temperatures were below 16.69°C. Gathering suffered extreme reduction during winter and greater activity in summer. Bees exploration were concentered on the younger leafs and apical portion of S. parahyba. Older leafs were mainly ignored, and gradually the exploring activity was constantly migrating to most young parts, while apical exploration was consistent all the studied period.

Variação das propriedades tecnológicas de painéis MDF em uma linha de produção industrial no Brasil

No presente estudo foram caracterizadas as propriedades tecnológicas de painéis de fibras de média densidade (MDF), em diferentes horários de produção em uma linha industrial brasileira, com o objetivo de avaliar a variabilidade tecnológica das chapas e sua qualidade em relação à norma técnica comercial. Painéis MDF confeccionados com fibras de Eucalyptus spp. (70%), Schizolobium parahyba (20%) e madeiras residuais de serraria (10%), aglutinados com resina ureia-formaldeído foram coletadas em intervalos de duas horas de um turno de produção da empresa. Foram determinadas às propriedades físicas (umidade, densidade aparente, absorção superficial, absorção de água, inchamento em espessura e taxa de não retorno de espessura) e resistência mecânica (flexão estática, dureza janka, tração perpendicular e arrancamento de parafuso). Os painéis de início e final do turno foram submetidos ao ciclo de envelhecimento acelerado, sendo avaliados posteriormente à densidade, tração e flexão estática. Do total das propriedades avaliadas nos painéis MDF, um percentual de 55% não apresentaram variações entre os horários de produção, e se enquadraram aos valores da norma. Apenas as propriedades de inchamento em espessura (IE 24h) e tração em 80% dos horários, não atenderam aos valores estipulados pela ABNT NBR 15316-1, variando de 11,2 a 15,6% e 0,42 a 0,62 N/mm², respectivamente, entre o início e o final do turno. O envelhecimento acelerado promoveu diminuição expressiva na qualidade das chapas. Os painéis MDF estudados apresentam bom desempenho tecnológico para uso em ambiente seco, e sua variação tecnológica decorreu do uso de fibras de diferentes madeiras na produção das chapas.