PALYNOLOGICAL ANALYSIS OF A PEAT- BOG SITED IN THE SIERRA DE (CÁCERES, WESTERN ) Gil Romera, G. & García-Antón, M. Departamento de Biología (Botánica), Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Madrid. (Spain)

INTRODUCTION. A new Holocene pollen sequence, recovered from a peat-bog sited close to the gorge of the river Mesto (, Cáceres) at an altitude of 1000 m.a.s.l. (UTM 30STJ98884), is presented. The scarcity of pollen data from western and southwestern Spain (Díaz Fernández 1992; Martín Arroyo and col., 1996) makes this study an interesting approach to the vegetation dynamics of this territory. In addition, the studied peat-bog is close to one of the few locations where the relict populations of Prunus lusitanica can be found on the . CLIMATE The climate in the area is of the extreme continental VEGETATION The study area is demarcated in its southernmost zone by an alder forest ( Alnus LOCATION Mediterranean type (Font, 2000) although the continental conditions are glutinosa ) which maintains some specimens of Fraxinus angustifolia and Salix atrocinerea ; EM attenuated due to the influence of humid winds from the Atlantic. Thus specimens of the latter two trees were found in the bog, along with the occasional specimen of SYST TRAL the summers are very hot, with a intense drought, but winters are mild. Sorbus aria . CEN

TAJO RIVER

MONTES DE TOLEDO Mesto’s gorge

ge Ran ercas Villu

In the surrounding elevations, there are formations of Q uercus pyrenaica in different degrees of conservation, as well as of Quercus ilex ssp . ballota. There are also individuals of Quercus faginea sbsp. faginea. Appearing in the surroundings of the bog are Genista florida , heathers (Erica arborea , E. australis ) and juniper ( Juniperus communis sbsp. communis ). The scrubs seen inside the bog are Erica tetralix , Genista anglica , typical of this type of environment and Erica. australis ,. Noteworthy among the herbaceous species are Molinia caerulea whose tussocks spread throughout the bog. Spores Trees Shrubs Herbs Aquatiqs

n us e ata uo e e l ti on id a a o c ergre s g. e ce um tra v um a Li ceae n a de e re rali e a ac n s e . m o t. lan e lus l e c are -t ae b a -t. ea hyll odiace o ae ea u e n us e r ust ae e ae e aceaec lus cus nthe c a a ir eae ali a aurea op c r pol con r a x s a a a ace ll e ace r ract ceae e unc ol et te l l Radiocarbon dates i e tus i a ll una ac r te n ryopen a sa ltha n Estimated Age (BP) D ep th inus x l e hrubs ri c pi h li lantago nca a on ril e ota CarboP Il e Alnus Betula CoryQue Querc O Sal Tre S Herbs Cis Hel E Eri c Eri c Ca Ol ePhy Vi ti s Po Ce A AsteAntheAs misCe BrassicaceaeCampanulCa C FabaceGenista aeLi P R PotentillCyp a Ju Ca R M T T Tota Zones 0 30 35 40 45 GM 2 b 50 50±35 55 60 65 500 70 75 GM 2 a 1000 80 85 90 1500 95 100 105 2000 110 GM 1 b 115 120 2500 125 130 135 3000 140 145 GM 1 a 150 3500 155 3725±50 160 165 20 20 40 60 80 20 20 20 20 40 60 80 100 20 20 200400 600 8001000 100 200 300 Exaggeration x 5 x 100 grains/gr

DISCUSSION AND CONCLUSIONS There is a general predominance of Alnus and little diversity of pollen types. This seems to indicate the local nature of the pollen reaching the Garganta del Mesto bog. Likewise, it can be deduced that the alders have been overestimated in the results in relation to the other taxa. Drastic oscillations during the origins of the bog . The basal zone, GM1a ( c.a 3700-2400 BP) is characterised by the frequent fluctuations of most of the arboreal taxa. One of the The last few centuries in the Mesto Gorge. In the last 500 years, there appears causes could be the recurrence of the fires, deducible from the carbon study, along with the presence of Cistus in the basal zone. In a parallel way, we could be dealing with the to have been a notable degradation in plant cover, along with a drop both in progressive adaptation of the taxa to the changing climatic conditions of the end of the Subboreal and the beginning of the Subatlantic. Likewise an anthropic use of the territory percentage and in pollen concentration. This may be the consequence of a can be detected, man became more and more sedentary at the end of the Bronze Age (Font, 1988) . The values in the concentration of Cerealia , Olea and Vitis indicate the sedimentation rate which was higher than in previous periods, and which presence of humans since 3700 years BP. would have led to a decrease in pollen concentration. The intensification of anthropic activity seems to be the main cause of the degradation of the landscape in this latter period. The recent increase in the percentage of several Pollen increase at the start of the Subatlantic (2500 - 50 BP). Around 2500 years BP in the zone GM 1b there was an increase in total pollen concentration which continued arboreal taxa is noteworthy, like both types of Quercus , willows and other consistently until 1500 years BP (zone GM 2a). This high concentration could be due to a lower sedimentation rate. The climatic conditions of the Subatlantic, more stable than bushes such as the Ericaceae . This might be the result of a progressive those of Subboreal, may have permitted the establishment of the vegetation in a stable manner. The effects of anthropy appear to have favoured certain taxa such as Olea, Corylus abandonment of logging and agricultural and livestock farming activities, or Quercus evergreen during the periods of Roman and Arabic dominance and can be seen in the selective logging of others such as Quercus pyrenaica for charring purposes. which would have given way to the recovery of the forest through the evolution of the heaths. The drop in the concentration of the Ceralia type pollen and of the herbaceous species, which would indicate ruderalisation, Asteraceae, Although only two datings are available, it could be said that there are differences in the sedimentation rate throughout a long the Chenopodiaceae , etc., as well as the low values for the carbon area, seem to confirm the idea of a recovery by the forest. secuence, in view of the different total pollen concentration registered. REFERENCES It is likely that the end of the Subboreal period in the Villuercas mountains gave way to a more temperate climate, similar to the present DIAZ FERNÁNDEZ, P.M., 1992. Historia de la vegetación en sierra Madrona y su entorno. Una contribución a su estudio. Tesis de Licenciatura. Facultad de Ciencias Biológicas, Universidad de Alcalá de Henares. 141 pp one. This would have allowed for the stabilisation of the vegetation in this area. FONT TULLOT, I., 1988. Historia del Clima de España. Instituto Nacional de Meteorología. Ministerio de Transportes turismo The existence of land management by man can be seen throughout the whole register; furthermore, the presence is known of y comunicaciones. Madrid. 297 pp. archaeological sites in the vicinity of the Villuercas mountains (Pavón, 1998). FONT TULLOT, I ., 2000. Climatología de España y . Salamanca: Ediciones Universidad de Salamanca.424 pp. MARTÍN ARROYO, T., RUÍZ-ZAPATA, B., VALDEOLMILLOS, A., BENITO, G., 1996, Reconstrucción de la vegetación durante el Cuanternatio reciente en el Puente del Arzobispo (Toledo, España). Primeros datos polínicos. Estudios palinológicos , pp 91-94 Universidad de Alcalá de Henares, Madrid. PAVÓN SOLDEVILLA, I.,1998. El tránsito del I al II milenio a.C. en las cuencas medias de los ríos Tajo y : La Edad de Bronce . Universidad de . 328 pp.