52 EUEORGEN: Quercus suberNEI¥IORK .80zoo (8U)Id=234.23Cuenca del Ulla (C/PO)Id=176.08Potes (S)Id=160.6as 38.4%as 42.0%lA 0.3%AU 4.2%OPy 2.1%OR 43.4%PS 21.7%S. Carrascoy (MU)Id=146.8Foncastfn (VA)Id=116.25Sestrica (Z)Id=107.83as 47.7%0151.5%PP 49.0%Other sp. 2.6%Hoyo de Manzanares (M)Id=99.5Pinet (V)Id=75.27S. Calderona (CS)Id=60.76,","-w.."j-..JV 2.7%010.5%PR 5.8%Fig. 3. Percentage of trees in each population and Margalef diversity index (Id),calculated with the densities of mature trees (trees/ha). AU=Arbutus unedo; IA=lIexaquifolium; JO=Juniperus oxycedrus; PA=Prunus avium; PH=Pinus ha/epensis;PN=Pinus nigra; PP=Pinus pinea; PR=Pinus pinaster; PS=Pinus sy/vestris;QI=Quercus iJex; QPy=Quercus pyrenaica; QS=Quercus suber; QU=Quercus robur.
PRESENTATIONS 53Medium values of diversity were found in Sierra de Carrascoy, Foncastin,Sestrica and Hoya de Manzanares. The low diversity of Pinet, Sierra Calderona andHaza del Lino is due to historic events: charcoal and firewood extraction wasintense in the three stands, which also have suffered from recent fires. In Haza delLino, cork oak is the only tree species, since the forest is regularly brushed andselective cuttings are made to favour cork exploitation.ConclusionsThe present status of Q. suber marginal populations is influenced mainly by the usesand management of the forest. Cork exploitation favours the species while, in thepast, charcoal and firewood extraction gave rise to even-aged forests wherevegetative reproduction dominates. Environmental conditions determine thebiological diversity and the ability of populations to response to disturbances.Two trends are shared by all populations: low number of young trees and poorregeneration, and loss of dominance. Except for Haza del Lino, the regenerationrate is higher for other tree species than for cork oak.The results obtained allow the classification of the populations according to theirgreater or lesser decline risk. Criteria taken into account for this classificationinclude the density of adult trees, density of regeneration, percentage of loss ofdominance, surface of the populations and presence of other Q. suber stands in theneighbourhood. Haza del Lino has been qualified as '0', with no current risk ofdisappearance. Potes, Sierra Calderona, Foncastin, Sestrica, Cuenca del rio andBozoo are at slight risk of decline, and Pinet and Hoyo de Manzanares at greaterrisk. On the other hand, Carrascoy can be considered almost extinct~The preliminary results obtained have mainly a qualitative chara-cter. In future, itwould be desirable to carry out more exhaustive inventories, as well as precisestudies on the phenology and mating system and an assessment of the regenerationpatterns in each population. This information would allow us to establish prioritiesand management programmes for the conservation and increase of genetic diversityin the populations.ReferencesDiaz-Fernandez, P.M., M.P. Jimenez Sancho, G. Catalan Bachiller, S. MartinAlbertos and L. Gil Sanchez. 1995. Regiones de procedencia de Quercus suber.ICONA, Madrid, 49 pp.Gil, L. 1995. Present state of Quercus suber in Spain: proposals for the conservationof marginal populations. Pp. 14-20 in Quercus suber Network. Report of the firsttwo meetings, 1-3 December 1994 and 26-27 February 1995, Rome, Italy (E.Frison, M.C. Varela and J. Turok, compilers). IPGRI, Rome, Italy.Margalef, R. 1980. Ecologia. Omega, Barcelona, 951 pp.Varela, M.C. and G. Eriksson. 1995. Multipurpose gene conservation in Quercussuber -a Portuguese example. Silvae Genetica 44:28-37.