Manuel Rodríguez Guitián

Upland vegetation in the north-west Iberian peninsula after the last glaciation: Forest history and deforestation dynamics

This paper presents the results of pollen analyses from organic sediments of seven cores (299 spectra) in a mountainous area of the north-west Iberian peninsula. The pollen diagrams, supported by seven14C dates, are used to construct a regional pollen sequence covering the main stages of vegetation dynamics, from the last phases of the Late-glacial until the present. During the Late-glacial Interstadial an important development of cryophilous forests (Betula andPinus) was recorded, although various mesophilous and thermophilous tree elements were also present. The Younger Dryas, palynologically clearly defined, is characterized by an important reduction in tree pollen percentages and the expansion of steppe formations (Poaceae andArtemisia). At the beginning of the Holocene, there was an expansion ofQuercus and a spread of other trees, which combined to give a vegetation cover of varied composition but dominated by mixed deciduous forests. Such forest formations prevailed in these mountains until 3000 years ago, when successive deforestation phases are recorded at various times as a result of increased farming activity. The results are compared with data from other mountainous areas in the northern Iberian peninsula and southern France.

Vegetation in the mountains of northwest Iberia during the last glacial-interglacial transition

Abstract. A new core taken from a site in the Sierra de Courel range of mountains in the northwest Iberian peninsula, Spain, enables a palaeoenvironmental reconstruction to be made of the biological events resulting from climatic changes and human activities during the last 17,000 years in the area. The sequence begins with a phase characterised by the dominance of Gramineae (Poaceae) and Pinus. A markedly arid period with prevalence of Artemisia pollen occurred between 17,5000 and 15,500 uncal. B.P. Subsequently, a succession of woodlands with Betula, Pinus and other mesophilous and thermophilous trees was recognised during the period 15,500-13,500 uncal. B.P. Between 13,500 and 10,300 uncal. B.P. herbaceous vegetation formations indicating moister conditions dominated the pollen record, although a maximum of Gramineae has been dated during the period 11,300-10,300 uncal. B.P. Comparison with other pollen data from neighbouring mountains allows an interpretation of the vegetation changes during the glacial/interglacial transition in the mountains of northwest Iberia. The Holocene pollen record from the site does not differ markedly from other records in the area, tree expansion occurring before 10,000 uncal. B.P. and high values of deciduous Quercus mixed with other trees and shrubs persisting until 3500 uncal. B.P., when increased human activities are shown by a fall of the tree pollen percentages.

Some considerations about the postglacial history and recent distribution ofFagus sylvatica in the NW Iberian Peninsula

This paper presents a re-assessment of the evidence of beech (Fagus sylvatica) presence on the NW Iberian Peninsula in the different stages of the Late Quaternary. For this purpose, numerous pollen diagrams were re-examined and the present-day distribution of the species was documented.Beech pollen has been recorded in different periods, before the Würm Pleni-Glacial, during the Late Glacial and the Holocene, leading to the hypothesis that there existed local refugia forFagus sylvatica in the NW Iberian Peninsula, comparable to those in more eastern areas of southern Europe, the existence of which has been recognized.This hypothesis explainsFagus’ present biogeographical range without recourse to the theory of migration from the Pyrenees through the Cantabrian region.However, there is no evidence that this species experienced a period of expansion or dominance in the vegetation in the northwestern Iberian Peninsula, unlike in the other parts of the Peninsula such as the western Pyrenees and the eastern Cordillera Cantabrica.

Sesquiterpene Lactones in Arnica montana: Helenalin and Dihydrohelenalin Chemotypes in Spain

An analytical RPLC method for sesquiterpene lactones in Arnica montana has been extended to include quantitative analyses of dihydrohelenalin esters. LC-ESI-MS-MS distinguished the isomeric helenalin and dihydrohelenalin esters. The dihydrohelenalin esters have lower response factors for UV detection than do helenalin esters, which must be taken into account for quantitative analyses. Analyses of flowers from 16 different wild populations of A. montana in Spain showed differing proportions of helenalin and dihydrohelenalin esters. For the first time a chemotype with high levels of helenalin esters (total helenalins 5.2-10.3 mg/g dry weight) is reported in Spanish A. montana. These samples were from heath lands at high altitude (1330-1460 m), whereas samples from meadows and peat bogs at lower altitudes were the expected chemotype with high levels of dihydrohelenalin esters (total dihydrohelenalins 10.9-18.2 mg/g). The phenolic compounds, both flavonoid glycosides and caffeoylquinic acids, in Spanish A. montana are reported for the first time. The levels of several of these compounds differed significantly between samples from heath lands and samples from peat bogs or meadows, with the heath land samples being most similar to central European A. montana in their phenolic composition.

Notas sobre la flora de humedales del noroeste ibérico

Presentamos en esta nota algunas novedades floristicas de los humedales del occidente iberico, ya sean relativas a la flora aloctona como Ludwigia grandiflora o Panicum dichotomiflorum o bien sobre flora autoctona. En esta ultima se incluyen datos relativ

Caracterización ecológica y florística de las comunidades lauroides del occidente de la Cornisa Cantábrica (Noroeste ibérico)

Mediante la comparacion de los inventarios floristicos obtenidos en los territorios Galaico-Asturianos occidentales (Sector Galaico-Asturiano, Subprovincia Cantabro-Atlantica, Provincia Atlantica Europea) con los de las asociaciones vegetales previamente descritas en el ambito cantabro-atlantico iberico, se establece la presencia en el extremo occidental de la Cornisa Cantabrica de cuatro asociaciones vegetales dominadas por especies lauroides ( Laurus nobilis, Arbutus unedo, Rhamnus alaternus ): lauredales costeros ( Calluno vulgaris-Lauretum nobilis ), lauredales interiores calcicolas ( Tamo communis-Lauretum nobilis ), lauredales interiores silicicolas ( Holco mollis-Lauretum nobilis ), y madronales ( Frangulo alni-Arbutetum unedonis ), asi como fragmentos de otra comunidad silicicola dominada por Rhamnus alaternus . Finalmente se realizan diversos comentarios sobre el significado biogeografico, valor paleoambiental e interes para la conservacion de las comunidades vegetales aqui tratadas.

Adiciones al catálogo pteridológico gallego

Se comenta la localizacion y ecologia de las poblaciones de diversas especies de helechos del genero Isoetes que constituyen novedades para el catalogo floristico gallego asi como nuevas localidades de otros pteridofitos de distribucion fragmentada o incl

Revisión de la sintaxonomía de los hayedos del occidente de la Cordillera Cantábrica (Noroeste Ibérico) mediante análisis multivariante

Se realiza una revision de la sintaxonomia de los hayedos existentes en el extremo occidental de la Cordillera Cantabrica (NW Iberico) basada en la ordenacion obtenida al aplicar un analisis NMDS a un conjunto de 47 inventarios floristicos. Los principales factores ambientales que explican la ordenacion obtenida son el pH del horizonte edafico superficial y la altitud. La interpretacion fitosociologica de las tendencias ecologicas observadas sustentan la existencia de dos tipos de hayedos en el area de estudio: acidofilos, incluibles en la asociacion Omphalodo nitidae-Fagetum sylvaticae , y neutro-basofilos asentados sobre suelos derivados de rocas carbonatadas pertenecientes a una nueva asociacion: Neottio nidi-avis-Fagetum sylvaticae . Sobre esta ultima comunidad se realizan consideraciones acerca de sus similitudes y diferencias floristicas y sucesionales con otros hayedos neutro-basofilos cantabricos asi como su ubicacion en el esquema sintaxonomico vigente.

Phytosociological framework and conservation value of supratemperate riparian birch forest of the NW Iberian Peninsula.

We studied the downy birch forests that grow in the headwaters of rivers in the mountains in NW Iberian Peninsula and their differences from other previously described birch forests. To do this, an ordination analysis was done on a data base of 342 releves (144 unpublished). As a result, four riparian forest associations were recognized in the territory, all of them belonging to the suballiance Saxifrago spathularis-Fraxinenion excelsioris (all. Hyperico androsaemi-Alnion glutinosae , ord. Alno-Fraxinetalia excelsioris , cl. Salici-Populetea ). Two associations ( Carici reuterianae-Betuletum celtibericae and Violo palustris-Betuletum pubescentis ) have been previously described, but the other two ( Chaerophyllo hirsuti-Betuletum pubescentis and Valeriano officinalis-Betuletum pubescentis ) are described here for the first time. We characterized their floristic composition, ecological features and distribution, and evaluated their conservation value under the criteria of the 92/43/CEE Community Directive, and with regard to national and regional lists of protected species.