Paricá (Schizolobium amazonicum) and embaúba (Cecropia sp.) as new raw materials for particleboards
In this work two potential new species for forest plantation projects in Northern Brazil were evaluated for their suitability in particleboard production. The main evaluated parameters of the laboratory boards were pH value and buffer capacity of the particles, compaction ratio, thickness swelling, modulus of elasticity (MOE), modulus of rupture (MOR) and internal bond (IB). The results showed that both species are highly suitable for particleboard production as they presented low densities (400–430 kg/m³), light color, good compressibility and no apparent adverse reactions after UF-resination.
Enrichment planting in logging gaps with Schizolobium parahyba var. amazonicum (Huber ex Ducke) Barneby: A financially profitable alternative for degraded tropical forests in the Amazon
Abstract Conservation of degraded forests is a challenging issue in the tropics, since the maintenance of environmental services and economic demands must be conciliated. Environmental services must be conserved while degraded tropical forests are demanded to be competitive against more financially profitable land uses as crop fields and pastures. The objective of this study was to evaluate productivity and financial profitability of enrichment planting in degraded forests. Seeds of Schizolobium parahyba var. amazonicum were planted in logging gaps of a 108-ha degraded forest in southeast Para (Brazil) in February 1995 (average = 91.7 seeds ha−1 and 15.3 seeds gap−1). After 13 years (2008), S. parahyba presented a volume increase of 3.1 m3 ha−1 yr−1 for individuals ⩾25 cm in DBH. More than 30% of the planted seeds were able to germinate, establish, and grow up to sizes ⩾25 cm in DBH. A cost-benefit analysis through Net Present Value (NPV) and a sensitivity analysis with different interest rates were performed to compare financial profitability of the treated and control area under roundwood and laminated plus sawnwood production. Enrichment planting using S. parahyba seeds presented higher NPVs in the treated than in control area for all simulations, except roundwood under interest rate of 9% per year.
Experimental investigation of the geotechnical properties and microstructure of lime-stabilized saline soils under freeze-thaw cycling
Abstract The Song-Nen Plain in northeastern China holds one of the three largest expanses of soda saline-alkali soil in the world. Due to its disadvantageous geotechnical properties, the saline soil in this area is unable to meet the needs of construction projects. This study evaluates the stabilizing effect of adding lime to such soils. Specifically, it investigates how the physicochemical and mechanical properties and microstructure of soda saline-alkali soil are altered by lime and how these changes are affected by both freeze-thaw cycling and the duration of curing. The results reveal that adding lime to saline soil transforms clay particles into sand and silt particles and causes the pore size distribution (PSD) to become bimodal, with small-pore and macropore populations. An increase in lime content leads to an increase in the unconfined compressive strength (UCS) but a gradual decrease in both the cation exchange capacity (CEC) and plastic index. Freeze-thaw cycles break up coarse particles and aggregate finer particles, increasing the diameter of macropores and decreasing the USC; however, the effect on specimens with >9% lime is negligible. It is further shown that the geotechnical properties of the soil change immediately after the addition of lime, indicating that the cation exchange reaction takes place very quickly. Furthermore, the pozzolanic reaction leads to an increase in the percentage of sand-sized particles and a decrease in porosity after 28 days of curing. Overall, these results indicate that it is feasible to use lime to improve the engineering properties of soda saline-alkali soil in this area.