The woods were extracted from the Puerto Cubarro sidewalk (1°50 32" N, 72°42 40.2" W) in the municipality of Calamar located on the left bank of the Unilla River belonging to the Department of Guaviare, 80 km from San José del Guaviare the capital with a mean annual precipitation of 2,800 mm, mean temperature up to 26.5 °C, and relative humidity >80% (Figure 1).

Figure 1

Ten trees of each species of Parkia discolor and Brosimum lactescens were used; all the activities of directed logging and of preparation for their extraction from the forest were included. Felling operations involved cutting the standing tree, measurement to determine the ideal size of the logs, limbing and bucking. Its fall was directed in order to reduce damage to the remaining mass and thus ensure forest sustainability. Good fuel management was ensured in all harvesting operations to avoid spills that altered soil conditions or caused a fire.

The logs were sawn and dimensioned for the extraction of samples or wooden specimens that after an airdrying process were measured and tested to technologically characterize the species under study. The test pieces were elaborated following the methodology proposed by the American Society for Testing and Materials (ASTM 2003) and the Colombian technical standards (NTC), which establish the procedures both in specifications of the test pieces, test speed and number of samples to be tested.

From each log, a central plank 8 cm thick was taken for the length of the log, from which two lumbers were obtained, maintaining very well-differentiated radial and tangential orientations, from which the test pieces necessary for each of the tests were obtained (Figure 2).

Figure 2

For the physical properties, 20 test pieces per species with a dimension of 3x3x10 cm length were used. To determine wood density under different moisture content conditions, the Colombian Technical Standard NTC 290 (ICONTEC 2006) was followed and to determine the radial, tangential, longitudinal and volumetric contractions of the wood following the NTC 701.

For the mechanical properties, 20 test pieces were extracted with dimensions of 5x5x20 cm, as established by the Colombian Technical Standard NTC 663 (NTC 2006), and 2.5x2.5x41 cm according to NTC 784 (NTC 2006), to calculate the parallel compression and static bending tests of the two forest species, which were free of defects such as knots, piths, cracks, missing edges, etc.

To evaluate the mechanical properties, the wood was taken to a dry-air (moisture content close to 12%). The tests were carried out in a Tinius Olsen universal testing machine with a load capacity of 15,000 kilograms.

The holocellulose content was determined using sodium chlorite according to the procedure of Wise et al. (1946). In a beaker, 150 mL of 1.5% (w/w) sodium chlorite solution were poured into 2 g of wood, and 10 drops of glacial acetic acid and the sample was placed in a water bath at 75 °C for 1 h. After that hour, 10 drops of glacial acetic acid and 1.5 g of sodium chlorite were added, it was cyclically repeated every hour, for a total period of 4 h. After chlorination, the solution was filtered, washed with 200 mL of cold water, followed by 10 mL of acetone; the residue was taken to a conventional oven at 105 °C until constant weight.

The lignin content was determined as described by TAPPI T 222 om-02 (2002). 15 mL of 72% sulfuric acid (w/w) were added to 1 g of wood sample, stirring it for 10 min and letting it stand for 2 h. Subsequently, 575 mL of distilled water were added and it was boiled for 4 h maintaining a constant volume, if necessary distilled water was occasionally added. Finally, it was filtered in Büchner funnels and the samples were repeatedly washed until the acid residues were removed. Finally, samples were brought to constant weight in an oven at 105 °C. All measurements were made in 12 replicates for each chemical composition determination (one sample per tree). Data were presented as percentages on a dry basis.

The extractive content was determined as described by TAPPI T 204 CM-97 (1997). 100 mL of NaOH to 1% were added to 2 g of wood sample, stirring it with a glass rod for 10 seconds, and placed the sample in a water bath, letting the water in the boiling bath for 1 h (97 °C); after bath, it was stirred again for 25 minutes. The digestion material was filtered and neutralized by adding 25 mL acetic acid to 10% for 1 min, then it was washed with 100 mL of hot water. The previous step was repeated, with a second portion of 25 mL of acetic acid to 10% for 1 min, then washed again with hot water leaving the material free of acid. Finally, they were brought to constant weight in an oven at 105 °C.

The statistical analysis was performed using a completely randomized experimental design for each test, with the help of the Statgraphics software. The information was processed according to the methodology described by Hoshmand (2006).

The results of density, dimensional stability coefficient (DSC) obtained for Guaimaro (Brosimum lactescens (S. Moore) C.C. Berg) are presented inTable 1 and for Dormidero negro (Parkia discolor Spruce ex Benth) in Table 2.

Table 1

Table 2

The results of the physical properties appear in each box and are represented as follows:

Where, is Mean, ± q is 95% Confidence Interval and CVt is the total coefficient of variation.

The Guaimaro is considered a high-density wood due to the value obtained in dry air density of 938.22 kg m^-3 and is classified as a heavy wood thanks to the anhydrous density value obtained of 898.85 kg m^-3; values that are within the range suggested by the ASTM (760-1,000 kg m^-3).

According to the basic density classification of the NTC 2500 (Civil Engineering and Architecture. Using Wood for Construction), the wood of Brosimun lactescens species belongs to Group A, making it useful for construction with 760.96 kg m^-3 (greater than 710 kg m^-3). These results are equal to those obtained by Rosales-Solórzano et al. (2018) in studies made for the same wood. Still, they are higher than those found for the wood of Brosimun alicastrum species, which has medium density and belongs to the Group B category used for construction purposes (Escobar and Rodríguez 1993).

The wood of Guaimaro (B. lactescens) has a high total volumetric shrinkage of 17.91%, placing it in the range suggested by the ASTM (15-20%). The wood has a very stable dimensional stability coefficient (DSC) of 1.28% (less than 1.5%), which determines its suitability for construction.

The Dormidero Negro is a wood of medium density and moderately heavy, with a dry air density of 640.00 kg m^-3 and an anhydrous density of 605.22 kg m^-3 range suggested by the ASTM (510-750 kg m^-3). The wood of Parkia discolor belongs to Group C, it is considered not suitable for heavy constructions and high resistance with 540.61 kg m^-3 (400-550 kg m^-3). These results were similar to those reported by de Miranda et al. (2012) and were higher than those obtained in Parkia biglobosa wood (Ataguba et al. 2015).

The wood of Dormidero negro (P. discolor) presents a low total volumetric shrinkage of 8.86%, placing it in the range suggested by the ASTM (less than 10%). The wood is dimensionally unstable with a Dimensional Stability Coefficient (DSC) of 2.36% (greater than 1.8%); which makes it unsuitable to be used as a raw material for construction. These results are equal to those obtained for the wood of Parkia biglobosa (Ataguba et al. 2015).

The results of the mechanical characterization of the wood Guaimaro (Brosimum lactescens) species are presented in Table 3 and Table 4 for the wood of Dormidero negro (Parkia discolor).

Table 3

Table 4

The response of Guaimaro wood to static bending is considered to be of a slightly high resistance according to ASTM standards with a modulus of rupture of 1,293.16 kg cm^-2 (1,260-1,519 kg cm^-2) and slightly high elasticity with MOE of 168.41x10³ kg cm^-2 (156-185 kg cm^-2), superior to that reported by Escobar and Rodríguez (1993) of 142x10³ kg cm^-2 for the wood of the species Brosimun alicastrum.

The response of the wood of Guaimaro (B. lactescens) to stress resistance in compressions parallel considers the wood to have high resistance to such compressions according to ASTM standards with compression parallel of 786.82 kg cm^-2 (750-1,049 kg cm^-2), superior to that reported for the same wood of the species B. alicastrum of 725 kg cm^-2 (Escobar and Rodríguez 1993). It can be used as wooden roofs, columns and pillars, wooden beams, wood for structures, etc.

The wood of Dormidero negro (Parkia discolor) presents low resistance to static bending with a modulus of rupture of 713.50 kg cm^-2 (754-510 kg cm^-2) and very low elasticity with MOE of 51.02x10³ kg cm^-2 (43-71 kg cm^-2) according to ASTM standards, lower than those reported for Parkia gigantocarpa and Parkia biglobosa wood (de Miranda et al. 2012; Ataguba et al. 2015).

The response of Dormidero negro (P. discolor) wood is of very low resistance to compression parallel to the grain of 92.24 kg cm^-2 (less than 479 kg cm^-2) according to ASTM standards, equal to those reported for P. gigantocarpa wood (de Miranda et al. 2012) and less than those obtained for Parkia biglobosa wood (Ataguba et al. 2015. It could be used to manufacture boxes or packaging that are not exposed to high pressures. It can also be employed in modular construction systems with low structural load and in decorative elements, such as picture frames, mirrors, or ornaments, where aesthetics and ease of handling are prioritized over strength.

The composition of the polysaccharides obtained for the Guaimaro (Brosimum lactescens) wood and Dormidero negro (Parkia discolor) are listed in Table 5.

Table 5

The holocellulose contents for Dormidero negro wood were similar to those reported for P. pendula and P. timoriana woods (Wahyuni 2018; Batista et al. 2021). The amount of lignin was similar to those reported for P. pendula and P. timoriana woods (Wahyuni 2018; Batista et al. 2021).

The wood of Guaimaro presented low contents in the polysaccharides formed by holocellulose of 65.60%, which were lower than those reported for the wood B. alicastrum of 81.05% (Castañeda 1986). Regarding lignin contents, they were 35.81% higher than those reported for B. alicastrum wood of 20.44% (Castañeda 1986).

The percentage of extractives for Guaimaro (Brosimun lactescens) wood was on average 18.52%, similar to that obtained for Brosimum alicastrum (17.51%), in studies conducted by Castañeda (1986) following the same procedure.

The percentage of extractives for Dormidero negro (Parkia discolor) wood is comparable to that presented by Batista et al. (2021); but greater than those obtained for Parkia timoriana wood (Wahyuni 2018).