Root biomass of Quercus ilex in a montane Mediterranean forest

The root systems of 32 single-stemmed holm oaks growing in shallow soils on largely unfissured bedrock were excavated in a mesic site and a xeric site in the Montseny Mountains (NE Spain). Individual root:shoot biomass ratios (roots with diameter <1cm not included) of single-stemmed trees were significantly higher in the xeric site (mean 0.45) than in the mesic site (mean 0.37), probably reflecting the lower water availability and higher light availability in the xeric site. Holm oaks ≥5cm dbh in a stand dominated by single-stemmed trees on mesic site had an aboveground biomass of 160 t/ha and a belowground biomass of 63 t/ha. The belowground biomass was composed of 30 t/ha or root crowns plus roots >5cm in diameter, 17 t/ha of roots 1-5cm in diameter, and 16 t/ha of roots <1cm in diameter. The xeric stand was dominated by multistemmed holm oaks with massive root crowns developed after repeated coppicing. Three multistemmed trees were excavated, yielding a mean root:shoot ratio of 1.2. Through resprouting from root crowns, managed or disturbed holm oak forests can accumulate a belowground biomass greater than that displayed aboveground: 91 t/ha (excluding roots <1cm in diameter) and 79 t/ha, respectively, in the xeric stand. -from Authors