Maria Jose GiI Garcia . Maria B1anca Ruiz Zapata . Juan Ignacio Santisteban . Rosa Mediavilla· Enrique Lopez-Parno . Cristino Jose Dabrio Late holocene environments in Las Tablas de Daimiel (south central Iberian peninsula, Spain) Abstract The use of a high resolution pollen record in combination with geochemical data from sediments com­ posed mainly of layers of charophytes alternating with lay­ ers of vegetal remains plus some detntal beds penmts the reconstruction of the environmental evolution of the last 3000 years in an inland wetland of the Mediterranean do­ main, thus introducing a new climatic dataset for the Late Holocene. Hydrological fluctuations. reflected in the re­ lationship between emerged and aquatic vegetation and inorganic and organic C and N changes, can be related to aridity or humid phases, while relations among arboreal taxa (Que reus and Pinus) and Artemisia are used as temper­ ature indicators. Five climatic periods have been identified: a Subatlantic Cold Period ( < 1 50 B.C.). cold and arid; the Roman Wann Period ( 150 B.C.-A.D. 270). wanner and wet­ ter; the Dark Ages (A.D. 270-A.D. 950). colder and drier; the Medieval Wann Period (A.D. 950-A.D. 1 400). wanner and wetter; and the Little Ice Age (>A.D. 1 400) indicated by a cooling and drying trend. Despite the lack of any direct evidence of hwnan action, there are some episodes related to deforestation during the Reconquista (Middle Ages) that mask the real climatic signal. Keywords Pollen· Late Holocene . Environmental changes· Mediterranean area M. J. Gil Garcia (�) . M. B. Ruiz Zapata Department of Geology, University of Alcab, 28871 Alcala de Henares (Madrid), Spain e-mail: mjose.gil@uah.es 1. I. Santisteban . C. 1. Dabrio Department of Stratigraphy, University Complutense of Madrid, 28040 Madrid. Spain R. Memavilla Direcci6n de Geologia y Geofisica, Instituto Geol6gico y Minero de Espaiia, 28760 Tres Cantos (Madrid), Spain E. L6pez-Pamo Direcci6n de Recursos Minerales y Geoambiente, Instituto Geol6gico y Minero de Espaiia, 28003 Madrid. Spain Introduction There has been an increasing interest in Late Holocene cli­ mate variability during recent years that is reflected, for example. in the IPCC (2001) report. This states "There is emerging evidence for significant, rapid (timescales of sev­ eral decades or more), regional temperature changes during the last 1 0.000 years. However. the evidence does not in­ dicate that any such events were global in scale" (Folland et a1. 2001 ); this includes periods like the "Little Ice Age" or the "Medieval Wann Period" (IPCC 2001 . pp 1 33-1 36). However there is still debate about the procedures used to reach those conclusions and their validity (Soon and Baliunas 2003; Soon et a1. 2003; McIntyre and McKitrick 2003. 2005). Apart from the numerical procedures used for data analysis. there is one key fact that affects the truly "global" validity of the global palaeoclimatic reconstruc­ tions: "there are still only a small number of long. well­ dated. high-resolution proxy records" (Briffa and Osbom 1 9 9 9 ). This is true in two main senses, the spatial coverage is very heterogeneous and the number of proxies used in studies of global climate change is low. The Iberian Peninsula is Wlique as it is located at the intersection between the Mediterranean and the Atlantic, Europe and Africa and is consequently affected by all of them. Because of its geodynamic position, its tectonic evo­ lution is very complex and this is reflected in a very variable topography. As a result the variability of environments and records is very high. Despite this, research has centred on similar environments to those of north and central Europe (peat bogs. high altitude lakes. deep lakes) while multi­ proxy study of many of the unusual systems �xisting in the Iberian Peninsula (saline lakes. temperate mIddle and low altitude biogenic lakes. etc.) did not begin until recently. For example. Martinez-Cortizas et a1. (1 9 9 9 ). using vari­ ations in Hg in a peat bog in NW Spain found evidence of some important climate changes during the last 4000 years. Valero-Garces et a1. ( 19 99 . 2000) identified variations in saline lake levels in NE Spain related to the end of the Medieval Wann Period. Luque and Juliii (2002) attributed most of the variations found in the sediments for the last 1000 years from the Lake Sanabria (NW Spain) to human activity, but were able to identify the Little Ice Age. Desprat et a1. (2003) recognised the classical climate episodes for recent times (First Cold Period of the Sub atlantic, Roman Warm Period, Dark Ages, Medieval Warm Period, Little Ice Age, Recent Warming) in the pollen record of the last 3000 years from the Ria de Vigo (NW Spain). More re­ cently, Riera et a1. (2004) carried out a study very similar to that presented in this paper. They used a multiproxy approach to reconstruct the last 2000 years of lake level variations in the Estanya lakes (NE Spain), differentiating between the human record and the climate record, and also clearly identifying the Medieval Warm Period and the Little Ice Age. Gonzalez-Alvarez et a1. (2005), in a multiproxy study of the last 3000 years on the Galician continental shelf (NW Spain), identified two periods of contrasting en­ vironmental conditions. They found that during the Subbo­ real/Subatlantic transition (2850 cal B.P.) conditions were stormy in comparison to those during the following Subat­ lantic and they identified an up welling related to the cooling of oceanic waters at around A.D. 1420, probably linked to the colder temperatures of the Little Ice Age. Despite the incomplete record from the Iberian Penin­ sula, there is considerable evidence of climate oscillations during the last 3000 years. These records show slight differ­ ences but this could be due to environmental factors as well as the complexity of the vegetation dynamics. Against this background the present paper describes a high-resolution study developed in a relatively continuous record from in­ land Spain and in particular tries to analyse the response of the vegetation to such changes with the help of the geo­ chemical record. Study site The study area is located in the La Mancha Plain, within the South-central Iberian Peninsula (Fig. 1 ). The La Mancha Plain corresponds to an E-W morphostructural depression in which Cainozoic terrestrial deposits overlie the Paleozoic (to the W) and Mesozoic basement. Unlike other Tertiary basins in the Iberian Peninsula, this depression has smaller dimensions and a YOWlger sedimentary filling. * Core CigDela 4-2 �42"o"W Muinllm /etIgIh: M,wimum width; Malrinllm dep(h: Ave�deplh; SlIff_atea: ,,.. 10.58 km 2.75 km 1f-5mrJ O.91m 16.75 Imr2 Fig. 1 Location of Las Tablas de Daimiel National Park and the core Cigiiela 4-2. TDNP: Las Tablas de Daimiel National Park The potential vegetation in the La Mancha Plain is typi­ cally Mediterranean, made up of Quercus rotundifolia (ev­ ergreen oak) forest together with Arbutus unedo, Phillyrea angustifolia, Rhamnus alaternus, Pistacia terebinthus and Rosa canina. At present, the vegetation consists of ev­ ergreen oak forests (Quercus rotundifolia), cleared and used as "dehesas" (forests of evergreen oak with tree-cover lower than 40% and with cleared spaces used for cultiva­ tion or pastures), together with extensive cultivation zones (Peinado-Lorca and Rivas-Martinez 1 987). The Las Tablas de Daimiel National Park is a fluvial wetland or open lake linked to the Gigtiela and Guadiana rivers, located at 605 m a.s.1. in central Spain (Fig. 1 ). The present-day system is fed by sulphated waters from the Gigtiela River, but since 1 983 the Guadiana River has supplied camonated surface and groundwaters. The climate is temperate Mediterranean with dry and hot summers and cold winters. Hydrologically, the system is controlled by high seasonal rainfall. In a typical year, the wetland is flooded for seven months, being almost dry for the rest of the year. In this paper we present palynological and litho logical data from the core Cigtiela 4-2 located in Las Tablas de Daimiel National Park (Fig. 1 ). Four other pollen sequences obtained from this area have been investigated previously. The first of these is Daimiel 11, covering about the last 3200 years (31 9 0 ±70 B.p.; 1628-1 305 B.C.) although in­ formation is limited by the low quantity of pollen grains in almost all samples (Menendez-Amor and Florschtilz 1 968) and the absence of pollen from several sections. The sec­ ond, Castillo de Calatrava, covers only about the last 6300 B.P. (6240 ± 1 9 0 B.P.; 5536-4727 B.C.; Garcia-Ant6n et a1. 1 986). The third, core CC-17, provides palaeoclimatic in­ formation since Late-glacial/Holocene transition (Dorado­ Valifio et a1. 1 9 9 9 , 2002) and the fourth, core TD, cor­ responds to the Last Glacial Cycle (Valdeolmillos et a1. 2003). Material and methods During December 2002, a coring campaign was carried out in the Las Tablas National Park yielding 40 cores taken from 1 5 coring sites. Five master points were selected and in each one two "dry" rotation cores (9 cm in diameter) were drilled and two manual PVC cores (1 1 cm in diame­ ter, 1 m in length) were made to recover the uppermost part. As result we obtained a composite core for visual study and sampling (one of which is core Cigtiela 4-2, Fig. 1 ). Once in the laboratory, the cores were opened, photographed and the stratigraphy recorded. With these data and the scanned photographs, a detailed strati graphical section (scale 1:1) was prepared for use during sampling. Sampling was per­ formed with a guillotine of our own design adapted to the shape of our cores. Samples were taken contiguously with an average thickness of 0.7 cm, each sample being split for the different analyses. After sampling a new stratigraphi­ cal section (Fig. 2) was constructed with lineally corrected Fig. 2 Core Cigiiela 4-2. Facies, vegetation-related geochemical parameters and dated samples Charophytes '<::tt... Vegetal remains ....... Carbonized veg. remains Cl" Gastropods _ Gastropods (fragments) Bivalm Bivatves (fragments) Parallel lamination ... Organic matte!" particles .... Mottling 8atlcarbonale nodules IN Irregulcw beddng Planar bedding """ Ch"Ojlh� • .", "'" � orgowcmalter • vego .. .", O M"" Charophyte muds & sands Organic-rich muds Gypsum-rich muds & sands depths and sample thicknesses (correcting for the mechan­ ical compaction produced by coring). Samples for geochemistry were sent to ALS Chemex lab­ oratories in Vancouver (Canada) where they were analysed for total carbon content (measured with a Leco© SC-444DR carbon and sulphur analyser), inorganic carbon (measured by CO2 coulometry with an UIC© CM1 40 Total Inorganic Carbon Analyzer) and organic carbon (calculated as the dif­ ference between total and inorganic C). N was detennined as extractable N (NH4, using a Technicon Autoanalyser©, and N03, colorimetrically using the CTA method) at ALS Environ Labs (Vancouver, Canada). AMS 14C dating of samples was done at the GADAM Centre (Gliwice, Poland) and 239. 240Pu and 2!Opo at the Centro de Investigaciones Medioambientales (CIEMAT, Madrid, Spain). Bulk samples were used as there was no evidence of contamination and all the C sources were biological (vegetal remains and bio-induced carbonates). The selection of samples was detennined by their strati­ graphical position and lack of evidence of contamina­ tion. The AMS dates were calibrated with CALIB vAA.2 (Stuiver and Reimer 1 9 9 3; Stuiver et a1. 2003) using the calibration datasets cited in Table 1 . Additionally, the 2!Opo and 239, 24°Pu profiles confinned that there was no evidence of mixing of sediment or of hiatuses in the uppennost 20 cm, as was also indicated from visual inspection of the cores. An age-depth model was constructed from these data and was tested against known (documentary) events recognisable in the sediments. From this a final recalibrated model was obtained. A good indication of the quality of the material was the fact that only minor adjustments were made to the age-depth model and these were probably re­ lated to the linear nature of the thickness correction method that does not allow for lack of homogeneity in the lithology. Table 1 Radiocarbon data. Calibration was performed with Lab. code Sample Depth 14C age cal ages, 2 (J probability CALIB vA.4.2 (Stuiver and (m) (yr B.P.) (cal B.P.) distribution Reliner 1993; Stuiver et al. 2(03) using calibration data GdA-308 4-2-79 0.56 521 ± 37 A.D.1321-1351 0.169 from Stuiver and Braziunas (599-629) (1993), Stuiver et al. (1998a, b) and McCorrnac et al. (2002) A.D. 1389-1445 0.831 (505-561) GdA-309 4-2- 10 1 0.73 1098 ± 39 A.D. 784-787 0.003 (1163-1166) A. D. 833-836 0.003 (1114-1117) A.D. 877-1020 0.994 (930-1073) GdA·306 4-2-132 0.99 2699 ± 53 972-957 B.C. 0.028 Data analyses were perfonned using R statistical software (R Development Core Team 2005). Samples were prepared for pollen analysis using stan­ dard palynological methods (Faegri et a1. 1 989 ; Moore et a1. 1 9 9 1 ). A total terrestrial pollen sum (>250) was used in calculating percentages. The pollen percentages for each taxon are based on the main pollen swn that excludes aquatic plants and pteridophyte spores because of their over-representation in these deposits. Spores and aquatic pollen percentages were obtained from the total sum (pollen + spores). Pollen data are presented as the rel­ ative pollen frequency of each taxon in the pollen diagram (Fig. 3) prepared using the TILIA ® and TILIA-GRAPH® (© Eric C. Grimm) computer programs. The representa­ tion of all taxa in the pollen diagram has been exaggerated (shading) twice. Local pollen assemblage zones in the sense of Reille (1 9 9 0) were recognised on the basis of changes in the representation of at least two ecologically significant taxa (Watts 1 9 73; Reille 1 9 90). Vegetation indexes were also constructed as they give guidance on the environmental variables (Fig. 4). Thus, the arboreal vs. non-arboreal pollen (APjNAP) is used as a key for moisture. The ratio of evergreen Quercus to the sum of Pinus and Artemisia is considered indicative of the tem­ perature. Finally, the ratio of hydrophytes to hygrophylles reflects the extent of the open area of the water body (the area not occupied by aquatic-emergent vegetation). Three main facies were identified by visual inspection of the cores (Fig. 2): ( 1 ) gypsum-rich siliciclastic muds and sands, changing at 88.5 cm (corrected depth) to (2) organic muds, and from 74.5 cm upwards, (3) alternation of Charophyte layers with organic matter laminae (of veg­ etal origin). The Principal Component Analysis of geo­ chemical and mineralogical data confinned this division by coincidence of the main PCs with sample visual fa­ cies (Santisteban et a1. 2004a). These analyses show the strong link between vegetation and C (organic C is de- (2906-2921) 939-795 B.c. 0,972 (2744-2888) rived from terrestrial and aquatic vegetation while inor­ ganic C is derived from Charophyceae oospores and stems; Santisteban et a1. 2004b). Also N, more abundant in purely aquatic vegetation, is an indicative element of aquatic pro­ ductivity (Fig. 2). Thus, the relation between inorganic and organic C gives an indication of the relationship between the aquatic macro algae and the remaining vegetation while the N/organic C ratio gives clues about the ratio of aquatic to emerged vegetation. Results The pollen record can be split in six zones representing different stages of the vegetal cover in the Las Tablas de Daimiel during late Holocene times (Fig. 3). Zone 0 ( 1 00-89.5 cm) shows a landscape dominated by grasslands. The taxa best represented are Asteraceae (liguliflorae and tubuliflorae) and Poaceae followed by Artemisia, Brassicaceae, Chenopodiaceae-Amaranthaceae, Saxifraga and Rumex. The next group, Shrubs, is domi­ nated by an association of Calluna, Juniperus, Pistacia and Rosaceae, replaced by Ericaceae towards the top. Trees are represented by Pinus, which is scarce, and minor quanti­ ties of evergreen Quercus, which replaces Ulmus. Aquatic taxa are characterised by the relative abWldance of Ty­ pha monada and Cyperaceae together with the presence of Potamogeton, Typha tetrada and spores. Sediments are represented by gypsum-rich muds with very low contents of inorganic and organic C and N. Zone A (89.5-83 cm) shows an increase in arboreal taxa, mainly Pinus and some evergreen Quercus followed by Ut· mus and the presence of Oleaceae. Shrubs are represented by Ericaceae and Cistaceae; there is a minor event that shows a temporary replacement of Cistaceae by Juniperus, C alluna and Pistacia. Grassland commWlities are still dominated by Asteraceae (tubuliflorae and liguliflorae) Fig.3 Pollen diagram (taxa and groups in percentages) of the studied section, organic and inorganic C and N content and pollen zones; roman: calibrated ages, italic: linear interpolated ages : ::: �: i":l � u .f ; Fig.4 Vegetation and geochemical indexes related to environmental variables ( * : out-of-sequence values; ?: anomalous data, possible human interference) and climatic periods wttlIlId yllgflltlon ....... moiatJ.n Wmptfttllnl doled OJ*I It)' .. c:oIdW wermer "i'"",;';:,...:r,..,rr.-:;,,,:,, 20 0 2 100 0,. 20 to 0 4 8 AD "" and Poaceae, but there is an evident upwards trend in Chenopodiaceae-Amaranthaceae together with Poaceae. Aquatic taxa show the major changes. This zone opens with a noticeable increase in Typha monada together with Cyperaceae and towards the top this association grows with the incorporation of Ranunculaceae, Polygonum and Potamogeton and the spore content increases. This zone marks the base of the organic-rich muds, which is characterised by a sudden increase in organic C, a decrease in gypsum, and low inorganic C and N content. Zone B (83-75 cm) shows a reduction in arboreal pollen, mainly recorded in the drop of evergreen Quercus. Pinus is still the main taxon and there is a presence of Tilia and Alnus. Shrubs increase slightly; their main association is Ericaceae and Cistaceae together with Juniperus (to the bottom) andPistacia and Rosaceae (towards the top). Herbs are still the main group but the composition of the associ­ ation changes. Asteraceae liguliflorae values fall suddenly and Chenopodiaceae-Amaranthaceae, Poaceae and Aster­ aceae tubuliflorae increase. Artemisia values are still high but fluctuating. The aquatic taxa show the highest values in Typha monada and there is an increase in Cyperaceae, while RanWlculaceae, Po lygonum, Potamo geton and spores content increase. This zone covers the upper part of the organic-rich muds, characterised by a progressive increase in Charophyceae (inorganic C) and a slight increase in N. Zone C (75-67 cm) starts with a sudden drop in content of arboreal and shrub pollen. Trees recover slowly with a clear increase in evergreen Quercus accompanied by Pi­ nus (which never reaches its previous values), Tamarix and minor amounts of Oleaceae. Other arboreal taxa present are Ulmus, Betula and Fraxinus. Shrubs are dominated by Ericaceae together with Juniperus and Pistacia and mi­ nor quantities of Rosaceae, with a very low component of Calluna and Cistaceae. Main features of the grass­ land commWlity are an important rise in Chenopodiaceae­ Amaranthaceae and Poaceae and a decrease in Asteraceae (the liguliflorae forms almost disappear), minimum val­ ues of Artemisia, an abrupt increase in Plantago, which shows its maximwn values, and an increase in nitrophyllous taxa (Rumex, Sanguisorba minor, Urtica). Of the aquatic � - -, Little Ice Age (>AD 1400): CCJk:J.w8mllh & sligh� coIde!' end drief - 55 AD 141 7 IJood.<1rough/ Irend than pJeVious period � , .. AD 'OBI , rn Letfd.iJse & ownership Med/aval w.rm period "'-, (AD 950·1400): warm and ineteaslngly M.n�dim8/e hlllTlid perbd induced cltenge AD .. 9 around Xlh c. ? - � 04rl1 Agu (AD 2100$50): � cold and and period "" .. " Rom.n _rm period (150 BC -AD 270): • leu coId.nd arid period � " ISIBC La/./fOII cold perlod(.c150BC): cold and and period 866SC taxa, Cyperaceae reaches its maximwn values while Typha monada decreases, RanWlculaceae also shows a maximwn and is present together with Polygonum, Lemna and a few Nymphaceae; trilete spore values are also the highest. This zone comprises the basal portion of the charophyte mud and sands, which are characterised by high and similar values of inorganic and organic C, plus an increase in the N/organic C ratio (related to an N increase in the sediments) and in the average values of the inorganic/organic C ratio. Zone D (67-57 cm) records the rapid spread of evergreen Quercus along with Tamarix and Alnus and the practical disappearance of Pinus. Ericaceae and Juniperus (which reaches its maximwn content) dominate the shrubs, fol­ lowed by Pistacia and traces of Cistaceae, while Calluna and Rosaceae disappear. The main change in the grassland community is the drop in Asteraceae (tubuliflorae and liguliflorae) and Chenopodiaceae-Amaranthaceae, which almost disappears, and the decrease in Poaceae and Plantago along with the increase in Artemisia, Rumex and Fabaceae, and the presence of Apiaceae, Brassicaceae, Liliaceae, Campanulaceae and Sanguisorba minor. The aquatic taxa suffer major changes as there is a sudden reduction in Typha monada, Typha tetrada is absent, Cyperaceae decreases and Ranunculaceae disappears. On the other hand, Polygonum rises and monolete spores show an abrupt increase (reaching their maximum values). This section of the charophyte muds and sands is characterised by higher values of the ratio inorganic/organic C, while the N/organic C ratio shows values similar to the previous zone. Zone E (57-48 cm) reintroduces Pinus, along with sparse Ulmus and Oleaceae, in the arboreal assemblage that is composed mainly of evergreen Quercus, with Tamarix and some Alnus. Shrubs show a slight decrease in Ericaceae and, more noticeably, in Juniperus, while Pistacia shows similar values to zone D and Rosaceae reappears. The grassland assemblage is similar to that of zone D. Poaceae decrease and Chenopodiaceae­ Amaranthaceae and Asteraceae (liguliflorae disappears) are mere present while Rumex is the main taxon. However there are increases in Artemisia, Plantago, Brassicaceae, Scrophulariaceae and Solanaceae. In the aquatic domain, Typha monada recovers slightly but Polygonum is the more representative taxon together with Cyperaceae. Monolete spores decrease noticeably, but not drastically. This is the uppermost part of the charophyte muds and sand studied in this paper and the main change in the composition of the sediment is the higher and fluctuating values of organic C and N and the decrease in the N/organic C ratio. Discussion The sequence starts, Zone 0 (around 2800-21 00 cal B.P. or < 1 50 B.C.), with open landscapes, as it is revealed by the very low content of C and N, dominated by grass lands with sparse trees (Pinus) and shrubs (Calluna). Halophyte taxa, together with Asteraceae and the low values of the arboreal/non-arboreal pollen (AP/NAP) ratio, reveal arid to semiarid conditions and saline soils (Figs. 3 and 4). Similar features have been interpreted as arid conditions in the pollen record from Castillo de Calatrava (Garcia­ Anton et a1. 1 986) and Daimiel II (Menendez-Amor and Florschiitz 1 9 68), where Artemisia and Chenopodiaceae­ Amaranthaceae increase simultaneously. This arid phase has also been identified in Tigalmamine (Atlas Range, Morocco) around 2500 to 2000 cal B.P. (Roberts et a1. 1 9 9 4) and in the Ebro Basin (Spain) around 2500 years ago us­ ing geomorphological (Gutierrez-Elorza and Pena-Monne 1 9 98) and other criteria (Davis 1 994). It has also been recognised by an arboreal (Quercus,Pinus and Salix) retreat in Huelva (SW Spain) around 2200 B.P. (2220 ± 80 B.P.; 404-54 B.C.) (Menendez-Amor and Florschiitz 1 964) and the beginning of aeolian deposits (dunes) and changes in the wind direction both in SW (Borja et a1. 1 9 9 9 ) and SE (Goy et a1. 1 998) Spain around 2700 cal B.P. Despite such arid conditions, ground waters were near the surface, as revealed by the association Typha-Cyperaceae and the nitrophyllous taxa, and there were short wet periods that permitted the development of small ponds colonised by aquatic communities composed of Potamogeton and algae. Despite the low presence of arboreal taxa, the ratio of evergreen Quercus to Pinus and Artemisia seems to indicate a gentle cooling trend and temperatures a little colder than the succeeding episode (Fig. 4). This event could correspond to the change in solar activ­ ity described by van Geel et a1. (1 9 9 9), identified in many places around the world. In Spain it has been identified in the northwest by Desprat et a1. (2003) and in the northeast by Gutierrez-Elorza and Pena Monne ( 1 9 98). In the Andean region van Geel et a1. (2000) recognised it through the anal­ ysis of the palaeolimnological, palaeobotanical and glacial records. In raised bogs of England and Ireland, Barber et a1. (2003) identified a climatic deterioration around 2700 cal B.P. Also, through analysis of human settlements, colluvial, lake and fluvial deposits, Zolitschka et a1. (2003) identified a similar climatic change around the Bronze Age/Iron Age transition. Recovery of the arboreal taxa in Zone A (2100-1680 cal B.P., 150 B.C.-A.D. 270), the higher diversity of the aquatic assemblage and the decrease in Calluna together with the increase in organic C (local vegetation-derived organic mat­ ter)' suggest wetter conditions and a rise of the seasonal water table that allowed the development of wet mead­ ows. This is confirmed by the N/org. C ratio, which indi­ cates emerged vegetation as the main source for the organic matter. The AP/NAP ratio suggests an increase in rainfall although arid conditions still remain. The increase in ever­ green Quercus as opposed to the Pinus and Artemisia swn (Fig. 4) reveals slightly higher temperatures. This improve­ ment in the climate has been also identified in NW Spain by Desprat et a1. (2003), who assigned it to the Roman Warm Period, but these authors extend this phase until A.D. 450. Roos-Barraclough et a1. (2004) identified a similar period (B.C. 40-A.D. 350) in peat humification profiles in Switzer­ land. McDermott (2004) presents the isotopic record of a stalagmite in southern Ireland where he identifies this pe­ riod. Also Jiang et a1. (2005) recognise this period in a similar time slice from reconstruction of the sea surface temperature off Northern Iceland. At the start of Zone B (1680-1000 cal B.P., A.D. 270- A.D. 9 50), the rise of the water table allowed the exis­ tence of relatively stable water bodies as evidenced by the progressive rise in Charophyceae (inorganic C), aquatic biomass (rising N/organic C ratio) and the increase in Poaceae, Cyperaceae, Typha, Ranunculaceae, Polygonum, Potamogeton and spores (Fig. 3). However the increase in Chenopodiaceae-Amaranthaceae (which reveals the exis­ tence of saline soils in the surroWldings) together with the almost imperceptible drop of the AP/NAP ratio point to slightly more arid conditions (Fig. 4). The drop in ever­ green Quercus together with the constant values of Pinus and Artemisia reveal a climatic deterioration that could be related to slightly lower temperatures assigned by Desprat et a1. (2003) to the Dark Ages. Riera et a1. (2004) also iden­ tified similar conditions, an increase in salinity and more arid conditions, in lakes in NE Spain during their stage viia (A.D. 160-820). Roos-Barraclough et a1. (2004) also found climatic deterioration centred on A.D. 550 in their Swiss peat humification profiles. Zone C (1 000-860 cal B.P., A.D. 950-1090) data show an important anomaly as arboreal and shrub taxa disappear to the bottom of the zone to recover later and drop again to the top (Figs. 3 and 4). Human influence (Riera et a1. 2004) or climatic causes (Desprat et a1. 2003) have been invoked to explain similar changes in other areas. In tenns of anthropic influence, the area was entered by Muslims in around the 8th century and was re-conquered by the Christians in late 1 1 th century. The Muslims introduced water mills and herding so clearance for pasture is a pos­ sible explanation for the extremely low values of arboreal and shrub pollen, the increase in Plantago, Boraginaceae, Brassicaceae and Lamiaceae and the presence of Oleaceae and Solanaceae. Also, the fighting that occurred towards the end of this period can explain the "drop" in arboreal and pasture taxa and the relative increase in shrubs at the top of this zone (Fig. 3). However, this is the period of maximum diversity in the aquatic environment, coinciding with high values of inor­ ganic C and of the N/organic C ratio (aquatic productivity), reflecting an increase in water depth (Fig. 4). The increase in riparian taxa (Poaceae, Cyperaceae and Tamarix) sup­ ports this water level rise and, together with the presence of Betula and Fraxinus and the decrease in Asteraceae and Chenopodiaceae-Amaranthaceae, implies a gradual shift to wetter conditions. Also, the higher ratio of evergreen Quer­ custo Pinus and Artemisia, as seen towards the bottom, may reveal a warming trend that would reach its highest point in Zone D (Fig. 4). As a hypothesis, this zone records climatic control of the vegetation plus a low intensity of anthropic action. In Zone D (860-530 cal B.P., A.D. 1090-1400), the no­ ticeable increase in evergreen Quercus, both in percentage and in absolute numbers, together with an increase in pas­ ture and nitrophyllous taxa reveal a more densely vegetated landscape very similar to the present Spanish "dehesas" (mediterranean forest with Quercus and grasslands used for herding; Fig. 3). However there are also evident changes in the aquatic environment. The drop in emergent vegetation (Cyper­ aceae, Typha and Poaceae), the sudden increase in mono­ lete spores, the low diversity in the aquatic taxa and the high inorganic C (Charophyceae) and N/organic C ratio values reveal the expansion of a very productive aquatic environment with a high nutrient load (Fig. 4) that could lead to frequent eutrophication episodes and algal blooms. These changes are consistent with the wanner and wetter conditions revealed by the increase in the evergreen Quer­ cus to Pinus and Artemisia and AP/NAP ratios (Fig. 4), similar to those identified as being typically mediterranean by Dorado et a1. (2002). Comparable changes are described by Desprat et a1. (2003), Julia et a1. ( 1 9 98) and Riera et a1. (2004) in NW, central and NE Spain, and these authors recognise this period as the "Medieval Warm Period" (Lamb 1 977). This episode is identified at about a similar date all around the world (China: Chu et a1. 2002; Arabia: Fleitmann et a1. 2004; Africa: Filippi and Talbot 2005; Iceland: Doner 2003; central Europe: Filippi et a1. 1 9 99 ; New Guinea: Haberle and David 2004; USA: Cabaniss Pederson et a1. 2005; Argentina: Mauquoy et a1. 2004; etc.) and despite particular features, it is characterised by lower climatic variability than other periods. After A.D. 1400, Zone E, the landscape was very similar to before, but the progressive rise in Pinus and Artemisia indicates lower temperatures (Fig. 3), which are also indi­ cated by fewer eutrophication episodes (monolete spores) and higher accumulation rates of organic matter (sudden increase in organic C and decrease of the N/organic C ra­ tio). Despite this the period was still wet (Fig. 4, AP/NAP ratio) and the water table rose. The higher, fluctuating val­ ues of organic C (Fig. 3) and the presence of eutroph­ ication episodes indicate frequent alternation of cold and wann periods. These characteristics suggest that this period represents the start of the "Little Ice Age" (Lamb 1 9 77), also identified by Desprat et a1. (2003), Julia et a1. ( 1 9 98), Gutierrez-Elorza and Pena Monne ( 1 998) and Riera et a1. (2004) in other records in Spain. This period is consistently fOWld in the sedimentary record and it is characterised by a higher variability in climatic conditions (Adhikari and Kumon 2001; Barber et a1. 2003; Lamb et a1. 2003; Valero­ Garces et a1. 2003; Cabaniss Pederson et a1. 2005; Cohen et a1. 2005; Dalton et a1. 2005; etc.). Conclusion Despite many studies that have pointed to the sun-climate relation (van Geel et a1. 1 9 9 9 ; Cooper et a1. 2000; Dean 2000; Bond et a1. 200 1; Mauquoy et a1. 2002; Labitzke and Matthes 2003; Gimeno et a1. 2003; Blaauw et a1. 2004; etc.) and the validity of the classical climatic oscillations described for the Late Holocene (Medieval Warm Period, Little Ice Age, etc.) there is a research line that suggests the non-global signature of these periods (IPCC 200 1; Jones and Mann 2004). Looking at Fig. 1 in Mann et a1. ( 1 9 98), the spatial dis­ tribution of the proxy series can be seen, allowing for the scarcity of infonnation coming from Mediterranean area. More precisely, in the case of Spain, this infonnation is restricted to two tree-ring series coming from mountain areas. The best way to solve this controversy would be to in­ crease the number of high-resolution records covering the last millennia and to increase the spatial coverage of these records. The present paper shows that the record of those Late Holocene climate oscillations identified by other authors in NE and NW Spain can be identified in the Iberian Peninsula interior, and in environments not used until now as high­ resolution climatic records. Despite human impact, which most authors agree adds a signal to the pollen record from A.D. 1 000, the use of the pollen record together with geochemical parameters permits the identification of five climatic stages for the last 3000 years. These are a cold and arid phase during the Subatlantic (Late Iron Cold Period, < B.C. 1 50), a warmer and wetter phase (Roman Warm period, B.C. 1 50-A.D. 270), a new colder and drier period coinciding with the Dark Ages (A.D. 270-9 00), the warmer and wetter Medieval Warm Period (A.D. 900-1400), and finally a cooling phase (Little Ice Age, >A.D. 1400). Acknowledgements We acknowledge the Spanish Ministry of Education and Science projects REN2002-04433-C02-01 and REN2oo2-04433-C02-02. 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