Thursday, August 9, 2007
Exhibit Halls 1 and 2, San Jose McEnery Convention Center
Many experimental studies have reported a facilitative effect of shrubs and grasses for the early establishment of reforested woody species in Mediterranean environments. But evidences exist of competition for water or nutrients in field conditions. Despite decades of research, no consensus has been reached on these items, and sometimes we need to take a decisions relative to remove or not grasses previous to forest labours.
Plant competitive ability differs from one species to another and little attention has been paid to the flora composition and its consequences on resource availability for young seedlings. Furthermore species composition and their relative abundance depend on light availability under natural conditions, and so these interactions must be considered.
In November of 2002, an experiment was set up at south of Sierra de Gredos mountains; acorns of Quercus suber were collected near the area and 1600 seeds were planted at 4 experimental plots placed according to a light gradient under tree canopies. A split-plot design was used for test herbs effects on seedlings’ survival. We identify the species composition in each plot and their relative abundance. Periodically we recorded the number of seedlings alive from Nov 2002 to Jan 2006.
Both, species composition and relative abundance were significantly different between plots. Grasses growing at full sunlight were more abundant and presented a higher number of perennial species and water demand species such as Cynodon dactylon, Vulpia muralis or Bromus tectorum compared with species under the canopy. Consequences on seedling survival are discussed.
