Datos de fenología, reducción de hoja y variaciones estacionales de la composición foliar, en cuatro especies del matorral costero del Mediterráneo meridional ibérico

Abstract

Three species of spiny shrubs (Withania frutescens, Lycium intricatum and Asparagus albus) were found living together in Nueva Tabarca island and, with Rhamnus lycioides ssp. lycioides in the Santa Pola cape, the study site selected, forming the association Chamaeropo Rhamnetum lycioides O. de Bolós 1957. All these species have a common, interesting feature: loss or reduction of leaves in dry summer. In this work, a first approach to the phenology of this species was done and also one attempt of quantification of the leaf reduction phenomenon, with the definition of Leaf Persistence Index (LPI) and the searching for its interrelations with water, pigments and the mineral nutrient content in leaves. A sampling of ten individuals of each species was made with two week intervals and phenological observations were made each time. In the samples, water con tent of leaves and stems, chlorophyll a and b and N, P Ca, Mg, Na and K concentrations in leaves were measured. In the phenology the behaviour is different in R.lycioides ssp. lycioides than in the other species, completely deciduous during part of the summer, which is precisely when they flower. The study of the variation of leaf content in relation with the LPI shows positive (accumulation) and negative (loss) significative correlations. In the fit to linear regressions the results are very similar in W.frutescens and A.albus and also, in part, in L.intricatum. The other species, R.lycioides ssp. lycioides is the more asynchronous in leaves' fall. The speed of accumulation of elements in relation to LPI changes in senescing leaves, can be measured with the slope of fitted linear regressions. Loss of water in stems was especially high in Solanaceae. The disappearance of chlorophylles is more similar in A.albus and L.intricatum. In elements such N and P, W.frutescens and A. albus have a more economical behaviour than L.intricatum.