Eucalypt plantations in the Mediterranean region are frequently regarded as poor in understory vegetation and as a threat to plant biodiversity. An experiment was developed to study the germination of seeds and the early growth of understory vegetation and thus verify whether reproductive
structures maintained their viability in the soil of intensive forest plantations. Soil samples were collected from a Eucalyptus globulus Labill. plantation in Portugal subjected to three treatments: removal of slash (R), broadcast of harvest residues on the soil (S), and incorporation
of slash by harrowing (I). Soil samples were submitted to controlled environmental conditions favorable to seed emergence. After 3 months, the average number of species per treatment, proportion of soil cover, Shannon-Wiener diversity and equitability indices, and plant biomass were determined.
Results were compared with vegetation surveys performed in the field trial during the early stages after planting. The greatest number of species, proportion of soil cover, and plant species diversity were observed in treatment S. Aboveground biomass was the greatest in treatment R. The results
confirmed that plant species maintained viable seeds in soil, but the intensity of soil disturbance may negatively influence species' ability to rapidly colonize soil after tree harvest.