Growth and structure of a young Aleppo pine planted forest after thinning for diversification and wildfire prevention

Aim of study: In the Mediterranean, low timber-production forests are frequently thinned to promote biodiversity and reduce wildfire risk, but few studies in the region have addressed such goals. The aim of this research was to compare six thinning regimes applied to create a fuelbreak in a young Aleppo pine (Pinus halepensis Mill.) planted forest. Area of study: A semiarid continental high plateau in south-eastern Spain. Material and methods: Three thinning intensities (Light, Medium and Heavy) were combined with two thinning methods: i) Random (tree selection), and ii) Regular (tree spacing). Tree growth and stand structure measurements were made four years following treatments. Main results: Heavy Random thinning successfully transformed the regular tree plantation pattern into a close-torandom spatial tree distribution. Heavy Regular thinning (followed by the Medium Regular and Heavy Random regimes) significantly reduced growth in stand basal area and biomass. Individual tree growth, in contrast, was greater in Heavy and Medium thinnings than in Light ones, which were similar to the Control. Research highlights: Heavy Random thinning seemed the most appropriate in a young Aleppo pine planted forest to reduce fire risk and artificial tree distribution simultaneously. Light Regular thinning avoids understocking the stand and may be the most suitable treatment for creating a fuelbreak when the undergrowth poses a high fire risk.