Abstract
Post-wildfire regenerated Mediterranean pine stands have a high risk of wildfire recurrence. Preventive clearings are frequently applied in a mix of systematic and selective ways, being a potential biomass source using technologies such as the collector-bundler BioBaler WB55. Our research aimed to compare the BioBaler with a chain mulcher performing systematic mulching of 50% vs. 67% of stand surface over 11.4 ha dominated by Pinus pinaster Ait. regenerated after a severe wildfire. Time studies included the machinery GPS follow-up and the weighing of each produced bale. Environmental aspects were also assessed. A regression curve related BioBaler weight productivity (odt·Workh−1) to pine biovolume (cover (%) average tree height, m). Surface productivity (stand ha·Workh−1) was greater for both technologies when a lower percentage of the total surface was cleared, but less than theoretically predicted. The BioBaler’s economic balance, including the cost of further selective clearing and the income from biomass selling, was costlier than that of the mulcher—in the most representative strata, 475 EUR·ha−1 vs. 350 EUR·ha−1. Under the studied conditions, BioBaler was not economically competitive with the conventional treatment, its main constraint being low collection efficiency (31% of the standing biomass in the cleared surface, 5.33 out of 17.1 fresh tonnes·ha−1).
Highlights
As almost 91,000 ha per year of forest land has burned over the last decade in Spain [1]and climate change will increase the fire danger potential in Mediterranean forests [2], improvements in forest fire prevention as well as suppression have become critical
The aim of this study was to assess and compare the systematic mulching and selective clearing work on post-fire naturally regenerated pine stands applying two different machines and working methods: a Biobaler WB55 and a conventional chain mulcher, both carrying out a systematic mulching of 50% vs. 67% of the total stand surface
The ideal situation was to find homogenous strata to facilitate the technology and work method comparison, the post-harvesting inventory showed that the Site 1 stratum with wide untreated strips was statistically different to the others (Table 2)
Summary
As almost 91,000 ha per year of forest land has burned over the last decade in Spain [1]and climate change will increase the fire danger potential in Mediterranean forests [2], improvements in forest fire prevention as well as suppression have become critical. Restoration and improvement treatments on post-fire natural regenerated Pinus pinaster Ait. stands are essential to reduce forest fire hazards, improve forest vigor, and increase early fruiting [3], as these pyrophytic young stands are usually very dense, and a second fire could seriously damage regeneration capacity and stand quality [4]. To this end, systematic mulching and further selective clearing is a common treatment in these Mediterranean young stands. Other Canadian trials used different mulchers for similar work: a
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