Abstract
ABSTRACT Planted forests occupy more than 6.5 million ha in Brazil, where harvest and logging operations are performed with increasingly heavier machinery, increasing the risk of soil compaction. Soil compaction can be avoided if soil load bearing capacity is not exceeded, what makes it important to assess both the soil strength and the impact of different operations. The aim of this study was to evaluate the load bearing capacity of some coarse textured soils (two Hapludult and one Haplorthod) in two soil horizons (BA and B), from northeastern Brazil; and to assess the impact of harvest and logging operations performed with harvester and forwarder. Although the Haplorthod presented higher load bearing capacity in both the BA horizon (for the whole moisture range) and the B horizon (for higher water contents), it suffered the greatest soil compaction. Traffic with the harvester resulted in soil compaction in both the BA and the B horizons, but the increase in bulk density was higher on the later, reaching 18.7% in the Haplorthod. The forwarder traffic intensity and the presence of plant residue cover significantly affected the occurrence of soil compaction. In the BA horizon, the increase in soil bulk density for different forwarder traffic intensities was 3 passes ~ 6 passes < 12 passes ~ 16 passes. The increase in bulk density was higher in the Haplorthod, reaching 32% after 16 forwarder passes over bare soil. Significant linear regressions were obtained from the number of forwarder passes and the increase in bulk density.
Highlights
In 2012, Brazil consumed approximately 182.5 million m3 of wood for industrial purposes, obtained from a total of 6.66 million ha of planted forests, from which about 35.2% was destined to wood pulp and paper production (Associação Brasileira de Produtores de Florestas Plantadas- ABRAF, 2013)
This study aimed to (i) obtain the load bearing capacity models, which relate the decrease in precompression stress with increase in soil moisture, for different coarsetextured soils planted with eucalypt (Eucalyptus sp.) forests; (ii) determine the impacts on soil structure of harvest and logging operations performed with harvester and forwarder; (iii) quantify the effects of the number of forwarder passes and the presence of plant residue cover on the soil surface in the occurrence of soil compaction
Soil bulk density did not increase in the BA horizons from the Hapludults, but in the Haplorthod the increase in bulk density was 5.2% and 18.7% in the BA and Bts horizons, respectively
Summary
In 2012, Brazil consumed approximately 182.5 million m3 of wood for industrial purposes, obtained from a total of 6.66 million ha of planted forests, from which about 35.2% was destined to wood pulp and paper production (Associação Brasileira de Produtores de Florestas Plantadas- ABRAF, 2013). In forestry production, wood harvest in extensive areas demands the use of increasingly larger and heavier farm machinery (Silva; Dias Junior; Leite, 2010; Suzuki et al, 2014), which can exert elevated pressures upon the soil (Horn; Vossbrink; Becker, 2004; Martins et al, 2013). This sort of farm machinery may cause changes in soil physical and mechanical properties, resulting in soil compaction and soil structure degradation (Dias Junior et al, 2005; Dias Junior et al, 2008; Ampoorter et al, 2010). If both high yields and environmental preservation are aimed in forestry production, it is essential that soil structure remains in good conditions (Cambi et al, 2015)
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