Factors affecting cork oak (Quercus suber) regeneration: acorn sowing success and seedling survival under field conditions

Abstract

Background: The lack of regeneration of cork oak (Quercus suber) is putting at risk the conservation of the montado. Biotic and abiotic factors as well as management are thought to constrain regeneration.Aims: Identify limitations to regeneration during the early stages and relate them to management practices.Methods: Experimental burying of acorns was carried out at three distinctly managed montados. Cache predation, seedling emergence, survival and resprouting were monitored during the first year. Regeneration was evaluated by testing the effect of biotic and abiotic factors in each stage.Results: Regeneration was determined by temperature and relative humidity. Early emerged seedlings showed higher drought tolerance and resprouting ability. Bigger acorns and higher plant cover significantly assisted emergence, survival and resprouting. Mortality causes were drought (38%) and mechanical ploughing (33%), while cache predation and browsing on seedlings were low (1.7%, when excluding tag effect on cache predation, and 0.6%, respectively). Seedling emergence and survival of drought were significantly lower in the most disturbed site than in the other two sites.Conclusions: Abiotic factors restrain regeneration while acorn size and plant cover are key factors determining seedling emergence and survival. The lack of regeneration may be overcome in the short term by preserving the shrub layer. Moreover, reforestation by direct sowing should be also considered.