Líquenes epífitos de los alcomocales ibéricos. Correlaciones bioclimáticas, anatómicas y densimétricas con el corcho de reproducción

Abstract

The purpose of this study was to test the possibility that epiphytic lichens can be used as predictive bioindicators of sorne characteristics of the reproduction cork related with its quality. The main objectives were: on the one hand, to cany out comparative study of the epiphytic lichen floras on virgin cork from Quercus suber L. in the Iberian Peninsula. On the other hand, to establish correlations between  lichen flora, climatic and bioclimatic parameters and the density and the anatomy of reproduction cork (radial growth, early cork/late cork ratio in the annual ring). The methodology was designed in such a way as to avoid subjectivity at all stages, from sampling protocol to data analysis. The cork-oak (morphology, autoecology, phytogeography) and the cork (anatomy, chemical composition, quality) are described. The ecological characteristics ofthe studied cork-oak forests are analysed from a clirnatic-bioclirnatic, phytogeographic and vegetation series point of view. The survey area comprises the largest cork-oak forests of the Iberian Peninsula: Gaditano-onubo-algarvienses, Luso extremadurenses, Valenciano­ castellonenses and Vallesano-empordaneses cork-oak forest, together with some isolated stands in the Pontevedra, Vizcaya, Burgos, Granada and Madrid provinces. Field work was carried out in mature stands of 73 localities of the different vegetation series. In each sampling plot the epiphytic lichen flora growing on virgin bark was identified. Therefore, ten trees were selected to obtain the presence-absence inventaries and the reproduction cork samples. These samples were always taken 130 cm above the ground.

The catalogue includes 304 species, in 76 genera. Each genera is accompanied by an identification key of the studied taxa which includes the bibliographic references of other species cited in Spain on this phorophyte. For each taxon, the autoecology and known distribution is discussed. In addition, a list of the kept material in the VAB-Lich herbarium is provided. The Gaditano-onubo-algarviense cork-oak forests, with 209 species, show the highest specific number, whereas the number of species of the remaining forest are quite similar among them with 147 species in the Luso-extremadurenses, 137 in the Valenciano-castellonenses and 136 in the Vallesano-empordaneses cork-oak forests. 50 taxa are shared by the four main areas, but only 28 are found in at least three sampling plots of each area. These asymmetries can be related with important climatic differences that are implicated at the specific selection level and determine the lichenic diversity at each tenitory.

Multivariate methods of classification and ordination were used to analyse a matrix of stations and species bases on presence-absence data. Cluster analysis separates the Luso-extremadurense cork-oak forest from the others. In the former group, those localities of the Mariánico-monchiquense and those of the Toledano­ tagano chorological sectors are separated. In the other group, the more continental and drier valencian localities (joint together with two Catalonian localities: Darníus and Capmany) are separated from the group including the gaditano­ onubo-algarviense and the Catalonian localities, more thermic and oceanic. In the cork-oak forest of Cádiz, the stands from Aljibe mountains, more humid and with Lobarion species, are clearly distinguished from the others, which are clustered depending on their vegetation series. PCA shows similar results and the ordering of the localities can be related with the continentality of the climate (1-axis) and with the water availability (11-axis).

The density and radial growth (thickness of the annual growing ring and of the early and late cork) of the reproduction cork has been quantified using a new methodology for freezing microtome (Patent P9301689). The results show significant differences among localities and areas. The radial growth of the reproduction cork and the density are correlated with several bioclimatic indexes and are in accordance with the management of the cork-oak forest. The cork from more oceanic areas, Cádiz and Catalonia, shows average annual increments significantly larger than the other ones. Corks from the more continental Valencian and Toledano-tagano forest show smaller yields and the annual rings show a clear differentiation between late cork and early cork, due to the vegetative latent period during the summer. For this reason, these corks provided good stoppers.

The combination of the different sources of information allow the establishment of significant correlations among floristic, bioclimatic, anatomical and density results. The effect of the climatic continentality on the late cork thickness and of the annual precipitation on cork production is demonstrated. Regressions between floristic results and anatomical characteristics provide the sarne significant correlations.

In conclusion, the results support the assumption that epiphytic lichens can provide valuable information for the phytoclimatical characterisation of the territories and for the prediction of sorne cork characteristics implicated in its quality. This relationship is due to the simultaneous effect of the climate on lichens and trees (regulation of the phelogen activity, cork properties, etc.). Therefore, lichen sensitivity to several ecological parameters allows the establishment of relationships between the epiphytic lichen flora and the environmental changes determined by forest managements.