ABSTRACT Evaluations of biomass and nutrient contents in teak stands are necessary alternatives for avoiding early cutting to provide supplemental data for the plant module of fertilization recommendation systems. This study aimed to adjust allometric equations to estimate the accumulation of biomass and nutrient contents in teak plantations in the central region of Brazil. Plots in seminal and clonal stands contained 81 trees aged 75 months, that had not received previous fertilization or thinning. Additional clonal stands aged 15, 51 and 63 months and a seminal stand aged 63 months had been previously fertilized during implantation. Allometric equations for biomass and macronutrient contents were obtained for components of the aerial parts of trees as a function of diameter at 1.3 m height (DBH), and the possibility of using an equation or the need for specific equations was evaluated for genetic material (seminal or clonal) and the fertilization scheme (not fertilized or fertilized). The equations adjusted to the four sets of stands, all with elevated predictive capacity, did not differ among each other based on an identity test. Thus, the use of a robust equation adjusted with data from all stands is recommended to obtain estimates with a high degree of accuracy. The biomass and accumulation of macronutrients in components of the aerial parts of teak trees should be considered to obtain the nutrient contents in both the exportable components in thinned trees and the components maintained in the area and available for biogeochemical cycling.

ABSTRACT: Litter decomposition dynamics and nutrient release are also dependent on their biochemical composition, and such information is important for adequate nutritional management but is still incipient for plants like teak. This study aimed to evaluate the decomposition dynamics, nutrient release, and biochemical composition of clonal teak litter. The study was conducted in areas of clonal teak stands, in São José do Rio Claro, Mato Grosso, Brazil. Litter collectors were arranged in the area to collect material along the entire dry period. Subsequently, this litter was placed in litter bags, which were distributed in the area. The litter bags were collected every month, for 0.91 years, to determine the dry matter and mineral nutrient contents, in order to estimate the decomposition and nutrient release. Litter biochemical composition was determined at the times of 0, 0.25, 0.58, 0.75, and 0.91 years. Teak litter, essentially leaves, had a half-life time (t1/2) of dry matter and C of 0.74 years, due to the high content of insoluble lignin, which corresponds to 2.28 Mg ha-1 of dry matter and 1.2 Mg ha-1 of C. The t1/2 values of N and P release (1.20 and 1.01 years) were higher than those of K, Ca, and Mg (0.08, 0.47, and 0.66 years, respectively). Hence, the nutrient release rate of the litter followed the descending order: K > Ca > Mg > P > N. The litter biochemical composition at the end of the experimental period showed reductions of 18.7 % in polysaccharides and holocellulose, 56 % in polyphenols, 56.3 % in tannins, 22.2 % in extractives, and 28.5 % in soluble lignin; and increases of 25.6 % in insoluble lignin and 22.6 % in total lignin. These data are useful for the balance of carbon and mineral nutrients and to support fertilization management in teak plantations in low-fertility soils.

Investigou-se o comportamento de juntas soldadas de uma liga a base de ouro utilizada na confecção de próteses odontológicas sobre implantes antes e após ser submetida ao processo de soldagem a laser. Constatou-se que houve uma mudança estrutural na região da solda e esta apresentou uma microestrutura dendrítica refinada e o metal base uma microestrutura granular bifásica com maior dureza e presença de precipitados de Au. Os ensaios eletroquímicos, em meio aerado de NaCl 0,15 molL-1 à temperatura ambiente, que simula as condições do ambiente oral, demonstraram que a junta soldada apresentou melhor desempenho frente à corrosão quando comparada ao metal base; provavelmente devida a estrutura metalúrgica desta região.

In this work, welded Au alloy joints, used for prosthesis supported by implants, have been studied before and after to laser welding processes. A refined dendritic microstructure was observed in the welding area. The base metal exhibited a two-phase granular microstructure with larger hardness and the appearance of Au precipitate. The electrochemical experiments, in NaCl 0,15 mol.L-1 solution at room temperature, which are appropriate to simulate corrosion at oral environment conditions, showed that the joint has a better performance when compared to base metal; probably due to the metallurgical structure in the region.