Human–landscape interactions in the Conquezuela–Ambrona Valley
(Soria, continental Iberia): From the early Neolithic land use to the
origin of the current oak woodland
⁎, Penélope González-Sampériz
, Eneko Iriarte
, Manuel Rojo-Guerra
, Blas Valero-Garcés
, Maria Leunda
, Eduardo García-Prieto
, Miguel Sevilla-Callejo
, Donatella Magri
, Julio Rodríguez-Lázaro
Instituto Pirenaico de Ecología-CSIC, Avda. Montañana 1005, 50059 Zaragoza, Spain
Dipartimento di Biologia Ambientale, Sapienza Università di Roma, Piazzale Aldo Moro, 5, 00185 Rome, Italy
Departamento de Estratigrafía y Paleontología, Universidad del País Vasco-Euskal Herriko Unibertsitatea, B. Sarriena s/n, Ap. 644, 48080 Bilbao, Spain
Laboratorio de Evolución Humana, Departamento Ciencias Históricas y Geografía, Universidad de Burgos, Plaza de Misael Bañuelos, Ediﬁcio I+D+i, 09001 Burgos, Spain
Departamento de Prehistoria, Universidad de Valladolid, Plaza del Campus s/n, 47011 Valladolid, Spain
Escuela Española de Historia y Arqueología en Roma-CSIC, Via di Torre Argentina 18, 00186 Rome, Italy
Received 17 November 2014
Received in revised form 22 June 2015
Accepted 25 June 2015
Available online 30 June2015
The sedimentological, geochemical and palynological analyses performed in the Conquezuela palaeolake (41°11′
N; 2°33′W; 1124 m a.s.l.) provide a detailed, multiproxy palaeoenvironmental reconstruction in one of the key
areas of inner Iberian Neolithic colonization. Combined with archaeobotanical and archaeological data from
well-dated settlements along the Conquezuela–Ambrona Valley we investigate how environmental conditions
may affect both socio-economic adaptations and livelihood strategies of prehistoric communities. The ﬁrst evi-
dences of early Neolithic occupation in the valley ca. 7250–6450 cal yr BP (5300–4500 BC) coincided with the
onset of a period (7540–6200 cal yr BP, 5590–4250 BC) with higher water availability and warmer climate as
alluvial environments were substituted by carbonate-wetland environments in the basin. The Conquezuela re-
cord supports an early Neolithic colonization of the inner regions of Iberia favored by warmer and humid climate
features and with preferentialsettlement patterns associated to lakes. The maximum human occupation of the
valleyoccurred during themid–late Neolithic andChalcolithic (6200–3200 cal yr BP, 4250–1250 BC) as evidenced
by the high number of archaeological sites. Although a number of hydrological oscillations have been detected
during this period, the intense landscape transformation at basin-scale, leading to a deforested landscape, was
largely a consequence of widespread farming and pastoral practices. Socio-economic activities during Bronze,
Iron and Roman times modiﬁed this inherited landscape, but thesecond largest ecosystem transformation only
occurredduring Mediaeval times when a new agrarian landscape developedwith the expansionof stockbreeding
transhumance. The current vegetation cover characterized by patches of holm and marcescent oaks and ﬁelds re-
ﬂects an intense human management combiningboth extensiveherding with agrarian activitiesin order to trans-
form the previous forested landscape into a dehesa-likesystem.
© 2015 Published by Elsevier B.V.
Modes and rates of early agriculture spread and the onset of the
cultural landscapes at Mediterranean-scale have grabbed the attention
of the European archaeological scene during the last decade (Pinhasi
et al., 2005; Cortés Sánchez et al., 2012; Zapata et al., 2013; Mercuri,
2014). Since the pioneering study carried out by Sokal (1991), combined
phylogenetic analysis and detailed archaeobotanical works have clearly
identiﬁed ﬁrst traces of agriculture in the early Holocene (Coward
et al., 2008) and related them with the onset of humid climate conditions
(Willcox et al., 2009; Haldorsen et al., 2011). Nowadays, it is well-
accepted that the European Neolithisation process followed a demic
Palaeogeography, Palaeoclimatology, Palaeoecology 436 (2015) 41–57
⁎Corresponding author at: InstitutoPirenaico de Ecología-CSIC,Avda. Montañana1005,
50059 Zaragoza, Spain.
E-mail addresses: firstname.lastname@example.org,email@example.com (J. Aranbarri),
firstname.lastname@example.org (P. González-Sampériz), email@example.com (E. Iriarte),
firstname.lastname@example.org (A. Moreno), email@example.com (M. Rojo-Guerra),
firstname.lastname@example.org (L. Peña-Chocarro), email@example.com (B. Valero-Garcés),
firstname.lastname@example.org (M. Leunda), email@example.com (E. García-Prieto),
firstname.lastname@example.org (M. Sevilla-Callejo), email@example.com (G. Gil-Romera),
firstname.lastname@example.org (D. Magri), email@example.com (J. Rodríguez-Lázaro).
0031-0182/© 2015 Published by Elsevier B.V.
Contents lists available at ScienceDirect
Palaeogeography, Palaeoclimatology, Palaeoecology
journal homepage: www.elsevier.com/locate/palaeo
diffusion model originated at the Fertile Crescent (Coward et al., 2008),
ﬁrstly spreading across southern Levant and eastern Mediterranean
islands (Vigne et al., 2012) and reaching the westernmost areas at ca.
7350 cal yr BP (5400 BC) (Zilhão, 2001; Bocquet-Appel et al., 2009).
This wave of advance was characterized by the introduction of new
crop varieties (Fuller et al., 2014), livestock domestication (Zeder,
2008) and forest clearance, modifying, at least locally, the landscape
physiognomy and vegetation structure.
In geographical terms, the early adoption of Neolithic agriculture in
the Iberian context followed the previously explained east–west pat-
tern, although controversy exists regarding the timing (Zilhão, 2001).
In Mediterranean coastal environments, numerous evidences demon-
strate that agriculture was early adopted (Antolín and Buxó, 2011;
Cortés Sánchez et al., 2012; Morales et al., 2013; Zapata et al., 2013;
Antolín et al., 2015). However, continental areas have been relatively
less studied and the paradigm that inner Iberia followed a marginal
and secondary colonization has been widely accepted. Recent studies
have changed this traditional view and seriously questioned the
whole chronological framework of the Iberian Neolithisation
(Rojo-Guerra et al., 2006; Alday, 2011; Zilhão, 2011; Utrilla et al.,
2013). Particularly, radiocarbon dates performed in short-lived pulse
and cereal samples (e.g., Peña-Chocarro et al., 2005a, 2005b; Stika,
2005; Rojo-Guerraet al., 2006, 2008) revealed the presence of Neolithic
settlements dispersed in inner Iberia as soon as ca. 7350 cal yr BP (Rojo-
Guerra et al., 2008 and references therein).
Multiproxy-based studies provide an unambiguous evidence reveal-
ing traces of agricultural and landscape management (López-Merino
et al., 2010; Di Rita and Melis, 2013; Revelles et al., 2015), but clear ev-
idences for an intense and early landscapetransformation in inner Ibe-
ria during Neolithisation are still scarce (Carrión et al., 2010 and
references therein). Terrestrial archives (particularly lakes) provide
integrated reconstructions at a basin-scale of past land use changes
and vegetation dynamics (e.g., Morellón et al., 2011; Rull et al., 2011;
Corella et al., 2013) and allow a better constrain of the environment
where past cultures took place (Cañellas-Boltà et al., 2013). Comparison
between changes in arboreal pollen frequencies and synchronous
increase in charcoalparticles help to evaluate anthropogenicdeforesta-
tion processes (e.g., Gil-Romera et al., 2008; Morales-Molino et al.,
2011). In addition, when archaeobotanical and plant macrofossils are
available from nearby, well-dated archaeological settlements, human-
induced landscape transformations are easier to infer (Sadori et al.,
2010). In fact, the integrated interdisciplinary collaboration including
palaeoenvironmental and archaeological research is crucial to achieve
a better understanding of human–environment interactions and to
explore possible feedbacks between settlement patterns and climate
variability (González-Sampériz et al., 2009; Fiorentino et al., 2013;
Mercuri et al., 2015; Montes et al., in press).
In this paper we reconstruct the palaeoenvironmental history of the
Conquezuela–Ambrona Valley (Soria, Northern Iberian Plateau; Fig. 1)
during the last 13,000 cal yr BP based on the Conquezuela palaeolake re-
cord. The region has been intensively surveyed from an archaeological
(Shipman and Rose, 1983; Falguères et al., 2006; Terradillos-Bernal
and Rodríguez, 2012), palaeobotanical (Ruiz-Zapata et al., 2003) and
palaeontological (Villa et al., 2005) point of view. The ﬁrst human occu-
pations in this area occurred during the Acheulean industrial complex,
Mid Pleistocene (ca. 350,000 cal yr BP, Villa and D'Errico, 2001;
Falguères et al., 2006; Santonja and Pérez-González, 2010). However,
the environmental conditions during the ﬁrst postglacial settlements
are not well-constrained. In this contribution we document and date
the ﬁrst evidence of human-induced landscape transformation in a
Fig. 1. Location of the Conquezuelapalaeolake in the Iberian Peninsula (shown by a star).The sites cited in the discussionare also included; 1)La Vaquera Cave (LópezGarcía et al., 2003);
2) Espinosadel Cerrato (Franco-Múgicaet al., 2001b); 3) Pelagallinaspeatbog (Franco-Múgica et al.,2001a); 4) Somolinostufa Lake (Currás et al.,2012);5)QuintanardelaSierra(Penalba,
1994);6) Lake Arreo (Corella et al.,2013); 7) Ambrona archaeologicalsite (Stika, 2005);8) Los Cascajos archaeological site (Peña-Chocarro et al., 2005a);9) Ojos del Tremedal(Stevenson,
2000); 10)Taravilla Lake (Morenoet al., 2008); 11) Villarquemado palaeolake (Aranbarri et al.,2014); 12) Les Ascusses sequence (Tallón-Armada et al.,2014); 13) Navarrés (Carrión and
van Geel, 1999); 14) Basa de la Mora (Pérez-Sanz et al., 2013); 15) Lake Estanya (Morellón et al., 2011) and 16) Lake Montcortès (Rull et al., 2011).
42 J. Aranbarri et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 436 (2015) 41–57
continental area of the Iberian Peninsula, applying a multiproxy strategy
to a lacustrine record. Comparison with local archaeobotanical data
allowed us to test possible environmental and/or socio-economic
processes involved in the cultural changes during the onset of the
Neolithic and the relationships between climate conditions and vegeta-
tion dynamics up to Mediaeval times.
2. Site description
The Conquezuela palaeolake (41°11′N; 2°33′W; 1124 m a.s.l.;
Fig. 2A) is located in the eastern fringe of the Iberian Northern Plateau,
among the headwaters of the Duero, Tajo and Ebro River Basins
(Fig. 1). The Conquezuela Basin sits on Upper Triassic claystones
(Keuper facies) bounded by Triassic sandstones to the north and
Jurassic and Cretaceous sandstones and marls to the south
(Terradillos-Bernal and Rodríguez, 2012). The formation of the
Conquezuela Basin was likely favored by karstiﬁcation processes affect-
ing the Upper Triassic formation since the Early Pleistocene. Active
karstic, weathering and denudation processes culminated with the de-
velopment of the endorheic Conquezuela–Ambrona Basin, later cap-
tured by the Masegar River, a tributary of the Jalón River
(Pérez-González et al., 1997; Falguères et al., 2006). While the eastern
Ambrona sector was captured by the Jalón River drainage basin and
progressively eroded by ﬂuvial incision, the western Conquezuela sub-
basin remained a semi closed-basin, only fed by small creeks and with
an ephemeral outlet to the northeast (Fig. 2A).
Low annual rainfall values and large thermal amplitude deﬁne the
regional climate as continental Mediterranean type. The mean annual
temperature (Valdelcubo station, 1103 m a.s.l.) is 10.8 °C, with large
daily and monthly oscillations, and the precipitation (annual average
471 mm) follows the typical Mediterranean pattern with maximum
values during spring and autumn. Annual potential evapotranspiration
rate is relatively high (up to 656 mm) and there is negative water
balance at least from June to September.
The vegetation landscape in the Conquezuela–Ambrona Valley has
been noticeably modiﬁed in order to expand agrarian activities
(Fig. 2B). Main crops are cereals but also sunﬂowers and ﬂax have
been extensively cultivated (Stika, 2005). The natural vegetation
belongs to the current mesomediterranean bioclimatic belt, and
includes Quercus rotundifolia and Quercus faginea communities along
with Juniperus communis,Cistus laurifolius,Thymus zygis,Thymus
vulgaris,Thymus mastichinia and Lavandula pedunculata. Siliceous soils
developed on the Upper Triassic sandstones (Buntsandstein Formation)
support patches of Quercus pyrenaica with a shrubland composed of
Crataegus monogyna,Rosa canina and Prunus spinosa.Thornyscrubs
such as Genista scorpius,Genista pumila andErinacea anthyllis dominate
Fig. 2. (A) Geological setting and (B) main vegetation communities in the Conquzuela–Ambrona Valley. The location of modern moss polster (CQM) are included. C) Neolithic and
Chalcolithic period archaeological sites surveyed along the Conquzuela–Ambrona Valley. Data have been modiﬁed from Morán-Dauchez (2006). Most important archaeological settle-
ments cited in the text are also shown and follow 1) La Lámpara; 2) La Revilla; 3) La Sima; 4) La Peña de la Abuela and 5) La Tarayuela.
43J. Aranbarri et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 436 (2015) 41–57
the more degraded and open areas. SparsePinus nigra stands are located
in the eastern sector of the basin and some Pinus sylvestris and Pinus
pinaster reforestations are also present (Fig. 2B). Regarding the
hydroseral communities, Typha sp. and Phragmites australis predomi-
nate, although some species of the genus Scirpus,Epilobium or Ranuncu-
lus are also visible. Diverse tree stands formed by Populus alba,Ulmus
minor or Salix sp. are also found in the palaeolake surroundings.
The Ambrona–Conquezuela Basin has a large number of Neolithic
and Chalcolithic sites (Stika, 2005; Rojo-Guerra et al., 2010)(Fig. 2C).
There is no archaeological evidence pointing to a previous regional
Mesolithic occupation. Neolithic settlements are chronologically
placed in two different phases;1) four sites belong to the early Neolithic
period (7250–6450 cal yr BP, 5300–4500 BC) and they had been
archaeobotanically studied in detail by Stika (2005), and 2) complex
megalithic tombs wide spreading along the valley belong to the mid-
late Neolithic (6450–4950 cal yr BP, 4500–3000 BC) (Rojo-Guerra
et al., 2010). Finally, during the Chalcolithic (4950–3950 cal yr BP,
3000–2000 BC), an exponential increase in the number of settlement
occurred (Fig. 2C).
3. Material and methods
In 2010, a 206 cm-long core was retrieved from the Conquezuela
palaeolake area using a Van Walt/Eijkelkamp mechanical drilling
machine. The core was split lengthwise, and sedimentary units and
facies described following Schnurrenberger et al. (2003) criteria. Images
were obtained using a digital Color Line Scan Camera attached to the
Avaatech XRF Core Scanner.
XRF measurements at 1 cm resolution were obtained with an
Avaatech XRF Core Scanner using two different settings: 10-s count
times, 10 kV X-ray voltage, and an X-ray current of 1000 μA for light
elements (Al, Si, S, Cl, K, Ca, Ti, V, Mn and Fe) and 25-s count times,
30 kV voltaje and 2000 μA for heavy elements (Ni, Cu, Zn, Ga, As, Rb,
Br, Y, Zr and Pb). Element concentrations are not directly available but
the obtained intensity values in counts per second (cps) can be used
to estimate relative concentrations. In addition, 79 samples for total
organic carbon (TOC), total inorganic carbon (TIC) and total nitrogen
content (TN) were analyzed in the IPE-CSIC laboratory of Zaragoza,
with LECO SC 144 DR and VARIO MAX CN elemental analyzers. TOC
and TIC values are expressed in percentages.
58 samples for pollen and non-pollen palynomorphs (NPPs) were
taken every 2–3 cm and prepared at the IPE-CSIC. In addition, 12 moss
samples (labeled as CQM) were collected in order to characterize the
modern pollen rain–vegetation relationship in the Conquezuela
palaeolake surroundings (Fig. 2B). Laboratory procedure follows
standard chemical method (Moore et al., 1991)withHF(40%),HCl
(37%), KOH (10%) and Thoulet solution (density = 2.0). Acetolysis
was performed on moss samples.
Pollen identiﬁcation was supported by the reference collection from
IPE-CSIC, determination keys and photo atlases (Reille, 1992). The
pollen sumsrange from 108 to 449 grains with an average and standard
deviation of 337 and 97 respectively. A total of 110 palynomorph taxa
were identiﬁed. Pinus pinaster/halepensis pollen type was differenced
from Pinus nigra/sylvestris type following the suggestions of Carrión
et al. (2000).Spirogyra algae as well as the Type 128 palynomorph
were recognized based on speciﬁc literature (van Geel, 1978; Carrión
and van Geel, 1999). Palynological results are expressed as percentages,
excluding hygrophytes, hydrophytes, ferns and NPPs from the pollen
sum. A stratigraphically constrained cluster analysis by the method of
incremental sum of squares (Grimm, 1987), has been applied to the ter-
restrial pollen dataset in order toestablish pollen zones. CONISS analysis
was performed in Psimpoll v.4.27 (Bennett, 2009).
The pollen rain–vegetation relationship was explored aiming to
deﬁne the real presence of oaks in our fossil spectra. We deﬁned palyno-
logically the oak communities in the near vicinity of the palaeolake by
applying a Bray Curtis dissimilarity coefﬁcient to our 12 modern pollen
samples. We used a paired, UPGMA clustering method to the surface
pollen data. UPGMA dendrogramhas been constructed in Rv.3.03 soft-
ware (Vegan package, R Core Team, 2012).
Fig. 3. Depth-age modelfor the Conquezuelapalaeolake based on lineal interpolation of
Cdata(Table 1), obtained usingthe Clam software (Blaauw, 2010).The grey envelope showsthe
95% conﬁdence interval. Sedimentological units have been also included.
Radiocarbon dates (AMS) for the Conquezuela sequence obtained from bulk sediment.
Lab. number Depth (cm) Radiocarbon date
C AMS yr BP)
Calibrated age (2σ)
(cal yr BP)
Poz-54171 15.5 510 25 551–507
Poz-60559 50 1365 30 1337–1261
Beta-384641 65 3010 30 3244–3168
Poz-54172 77.5 4655 35 5469–5311
Poz-50557 90 5145 35 5950–5877
Beta-384641 128 6280 40 7307–7156
Poz-60556 147 6670 40 7606–7474
Poz-60727 188 6970 60 7857–7726
Poz-60553 203 11,170 90 13,204–12,803
44 J. Aranbarri et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 436 (2015) 41–57
Fig. 4. Main sedimentological units, selected XRF curves and ratios and elemental geochemical analysis (TOC, TIC and atomicTOC/TN) for the Conquezuela sequence. XRF intensities are expressed in counts per second (cps) and TOC and TIC values in
45J. Aranbarri et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 436 (2015) 41–57
The Conquezuela palaeolake depth-age model is based on 9 AMS
samples obtained from bulk sediment and performed using Clam soft-
ware package (Blaauw, 2010).
4.1. Sedimentary sequence
Visual description, smear slides microscopic observation and
geochemical analyses (XRF elements and ratios together with TOC, TIC
and atomic TOC/TN) allowed characterization of sedimentary facies
and sedimentological units in the Conquezuela sequence. From base to
top, four main sedimentary units have been deﬁned (Fig. 4).
UNIT-4 (206–153 cm depth) is composed of massive, carbonate
and siliciclastic gravels and sands, with a very low organic content
(TOC b1%). Geochemically, this unit is characterized by the highest
Zr/Rb ratio coherent with the coarser and detrital nature of the sedi-
ments, and the lowest Sr/Ti also indicative of dominance of allochtonous
siliciclastic minerals. Both, sedimentary and geochemical features point
to deposition in an alluvial setting.
UNIT-3 (153–95 cm depth) groups light-colored carbonate-rich
massive to banded silts. Thesesediments are characterized by a decreas-
ing grain-size trend (lower Zr/Rb values), lower siliciclastic content
(low Al, Si values) and increasing carbonate content (higher Ca/Ti,
Sr/Ti ratios and TIC percentages). This unit represents the onset of
sedimentation in a shallow lake still with low bioproductivity but
high rates of carbonate production in the palustrine belt.
UNIT-2 (95–44 cm depth) is composed of organic and carbonate-
rich silts. The unit is characterized by an increase in organic matter
and a decrease in atomic TOC/TN ratio, indicative of the change from
land-based vascular plants (values around 18–20) to mainly algal
dominance (values 11–13) (Meyers and Lallier-vergés, 1999). This
unit can be divided into three sub-units. Sediments in SUB-2C (95–
80 cm depth) have higher siliciclastic content, although with increasing
values of Ca/Ti and Fe/Mn ratios (Fig. 4). During SUB-2B (80–60 cm
depth), this trend is reverted with a marked reduction in the carbonate
content (Ca/Ti) and an increase in ﬁne siliciclastics (Al, Si). In SUB-2A
(60–44 cm depth) carbonate content rise again (Fig. 4). The sediment
variability in UNIT-2 is common in wetland-shallow lake settings,
where a mosaic of depositional environments occurs. Changes in car-
bonate content in the sediments are associated to better development
of littoral paludal environments, commonly related to a decrease in
UNIT-1 (44–0 cm depth) is composed of organic-rich silts with
the highest percentages of TOC (up to 5%) and the lowest values of
TOC/TN ratio (up to 10). Besides, maximum valuesof the ﬁne siliciclastic
fraction are attained in this unit (high Si andAl and low Zr/Rb), carbon-
ate contentare the lowest (Fig. 4). These sediments were deposited in a
wetland dominated by organic productivity with limited palustrine
carbonate forming processes. The top 15 cm interval shows evidence
of modern soil processes and bioturbation.
4.2. Chronological model
The depth-age model for Conquezuela palaeolake sequence (Fig. 3)
is based on 9 AMS
C samples obtained from bulk sediment (Table 1)
and calibrated using the latest INTCAL13 curve (Reimer et al., 2013)im-
plemented in Clam, software package for classical, non-Bayesian, age
modeling (Blaauw, 2010). The sedimentary record (from ca. 13,000 to
540 cal yr BP) shows a highly variable sedimentation rate (Fig. 3). A
sedimentary hiatus likely occurs within UNIT-4, between the two low-
ermost dates. Abrupt sedimentological changes in UNIT-4 (Fig. 4) and
the null pollen preservation (see further details below), also suggest a
major hiatus covering the Lateglacial and early Holocene periods.
The sedimentation rate increases during UNIT-3, reaching up to
14.45 yr cm
and greatly decreases in UNIT-2 (ca. 114 yr cm
top UNIT-1 has an intermediate accumulation rate, ca. 21.74 yr cm
(Fig. 3) as a response to a rapid organic accumulation in the wetland
(Fig. 4). Periods of higher sedimentation rate correspond to phases of
dominant carbonate (UNIT-3) or organic (UNIT-1) production in the
4.3. Pollen sequence
According to the CONISS analysis, 5 main vegetation zones (CQ)
have been deﬁned and roughly follow the units established by the
sedimentological sequence. Pollen, spore and NPP preservation and di-
versity was good except in sedimentary UNIT-4. The summary pollen
diagrams are plotted in the Fig. 5.
CQ-5 (206–145 cm depth, 13,020–7540 cal yr BP, UNIT-4): 13 sam-
ples have been analyzed in this section; however none of them contains
enough pollen to be included in the diagrams.
CQ-4 (145–99 cm depth, 7540–6200 cal yr BP, UNIT-3): The highest
frequencies of Pinus nigra/sylvestris type (N60%) together with the con-
tinuous presence of Juniperus,Quercus faginea/pyrenaica type and
Quercus ilex/coccifera type characterize the pollen assemblage of this pe-
riod (Fig. 5). The ﬁrst Cerealia type record is found at ca. 7380 cal yr BP
while Fabaceae, Cichorioideae or Asteraceae appear but still showing
low values. Hygro-hydrophytes, Spirogyra, as well as Type 128
palynomorph, attain the lowest frequencies of the whole sequence
while Glomus peaks are recorded (Fig. 5).
CQ-3 (99–64 cm depth, 6200–3200 cal yr BP, SUB-2C, SUB-2B):
The frequency of anthropogenic-related indicators increase at the
same time of a remarkable and long-term decrease in Pinus nigra/
sylvestris type (Fig. 5). Cichorioideae attach the highest frequencies,
followed by Chenopodiaceae, Brassicaceae, Fabaceae, Polygonaceae
and Lamiaceae, denoting a progressive landscape opening (Fig. 5).
Juniperus,Quercus faginea/pyrenaica type and Quercus ilex/coccifera
type are also continuously recorded. Overall, both mesophytes
and Mediterranean taxa do not attain high frequencies. Hygro-
hydrophytes, Spirogyra algae and Type 128 do not show marked chang-
es with respect to the previous trend (Fig. 5).
CQ-2 (64–40 cm depth, 3200–930 cal yr BP, SUB-2A): A partial recov-
ery in the arboreal pollen is recorded, Pinus nigra/sylvestris type being the
main favored taxon. Pinus pinaster/halepensis type also increase and
Juniperus is continuously recorded. Anthropogenic-related indicators,
however, remain high and probably well-represented locally (Fig. 5). To-
is observed, synchronous to the development of Spirogyra and the Type
128 palynomorph (Fig. 5). Sordariales shows an exponential increase.
CQ-1 (40–16 cm depth, 930–540 cal yr BP, UNIT-1): Arboreal pollen
presents minimum values as a consequence of Pinusnigra/sylvestris type
decrease. However, Pinus pinaster/halepensis type, Juniperus,Quercus
faginea/pyrenaica type and Quercus ilex/coccifera type report slight in-
creases (Fig. 5). Cerealia type, Fabaceae and Trifolium type are well rep-
resented, paralleling other nitrophilous and ruderal taxa like Artemisia,
Cichorioideae, Asteroideae, Chenopodiaceae, Brassicaceae, Plantago,
Urtica and Polygonaceae that reveal a noticeable expansion (Fig. 5).
Olea and Juglans report continuous frequencies. An exponential increase
is observed in Cyperaceae that is followed by Juncus,Myriophyllum
alterniﬂorum type, Spirogyra and Type 128 (Fig. 5). Sordariales reach
their highest values together with Glomus. The change observed in the
hygro-hydrophyte assemblage is also highlighted by the sedimentolog-
ical and geochemical proxies deﬁned in UNIT-1.
4.4. Modern pollen-vegetation relationship
The 12 moss polsters collected from the surroundings of the
Conquezuela–Ambrona Valley (Fig. 2B) reveal different pollen spectra
in comparison to the fossil assemblages, especially regarding the fre-
quencies acquired by both evergreen and marcescent oaks. The results
46 J. Aranbarri et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 436 (2015) 41–57
Fig. 5. (above) Summarypollen diagram fortrees, shrubs and herbsfor the Conquezuelapalaeolake sequence. Mesophytes comprises Betula,Corylus,Tilia,Alnus,Salix,Populus,Ulmus,Celtis,
Fraxinus,Juglans,Fagus, Deciduous Quercus,Quercus faginea/pyrenaica type, Buxus,Cornus,Myrtus,Vitis,Hedera andSmilax. Mediterranean taxa englobes Quercus ilex/coccifera type, Quecus
suber,Pistacia,Rhamnus,Thymelaea,Phillyrea,Olea,OleaceaeandArbutus. Anthropogenic indicators and ruderals groupis composed of Cerealiatype, Artemisia, Cichorioideae, Asteroideae,
Cirsium/Carduus type, Centaurea, Chenopodiaceae, Caryophyllaceae, Plantago, Brassicaceae, Fabaceae, Trifolium type, Lotus type, Boraginaceae, Urtica,Rumex,Euphorbia,Papaver,
Geraniaceae, Malvaceae, Polygonaceae, Asphodelus and Linum. Xerophytic and thorny scrubland includes Juniperus,Rosaceae,Prunus type, Ribes,Genista,Cistus,Helianthemum,Ephedra
distrachya type, Ephedra fragilis type, Lamiaceae and Teucrium. (below) Summary pollen diagram for hygrophytes, hydrophytes and NPPs. Hygro-hydrophytes group comprises Ranuncu-
lus,Juncus, Cyperaceae, Typha/Sparganium type, Typha latifolia type, Thalictrum/Alisma type, Myriophyllum alterniﬂorum type, Myriophyllum spicatum/pectinatum type, Potamogeton,
Utricularia,Nuphar,Nymphaea and Callitriche. Dots represent percentages b0.5%. Sedimentological units have been also included.
47J. Aranbarri et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 436 (2015) 41–57
of the cluster analysis separate two main groups of moss samples
The ﬁrst cluster comprises pollen types corresponding to the samples
collected from open and degraded areas (samples CQM-11, CQM-3,
CQM-12, CQM-10, CQM-8, and CQM-9) where an open, patched thorny
scrubland of Genista scorpius,Genista pumila and Erinacea anthyllis domi-
nate (Fig. 2B). Overall, Poaceae, anthropogenic and nitrophilous indicators
like Cerealia type, Asteroideae, Cirsium/Carduus type, Chenopodiaceae
and Plantago characterize the pollen assemblage. Shrubs like Juniperus,
Genista,Cytisus/Ulex type and heliophytes such as Cistus and
Helianthemum are also well represented. Quercus faginea/pyrenaica type
and Quercus ilex/coccifera type do not present high values. Although
sparsely recorded and conﬁned to the eastern sector of the
Conquezuela–Ambrona Valley (Fig. 2B), Pinus nigra/sylvestris type values
are well recorded in the samples collected from the open environments.
The second cluster (samples CQM-4, CQM-6, CQM-7, CQM-1, CQM-2,
and CQM-5) indicates noticeable frequencies of Quercus faginea/
pyrenaica type and Quercus ilex/coccifera type, followed by Olea and
shrubs like Rosaceae, Prunus type and Lamiaceae (Fig. 6). This assem-
blage deﬁnes well the landscape where the moss samples were collect-
ed, comprising diverse patches of Quercus rotundifolia,Quercus faginea
and Quercus pyrenaica along with diverse shrubs such as Rosa canina,
Crataegus monogyna,Prunus spinosa and Lavandula pedunculata,as
shown in the Fig. 2B. In these moss samples, Pinus nigra/sylvestris type
does not present high frequencies whereas Poaceae, anthropogenic
and nitrophilous indicators are almost absent (samples CQM-4, CQM-
6, CQM-7) (Fig. 6).
The sedimentological, geochemical and palynological analyses carried
out in the Conquezuela palaeolake provide a detailed reconstruction of
the landscape evolution in one of the most representative areas of the
Neolithic colonization in inner Iberia (Rojo-Guerra et al., 2008). Compar-
ison of the carpological research carried out by Stika, (2005) from the
nearby La Lampara and La Revilla settlements and our pollen results
(Fig. 5) helped to characterize the land use changes developed in the re-
gion since the early Neolithic. The occurrence of a large number of well-
dated archaeological sites in the Ambrona–Conquezuela Valley also
allow discussing the links between environmental factors and human set-
tlement patterns since the ﬁrst postglacial occupations. Overall, six phases
in the landscape evolution have been established.
5.1. Pre-Neolithic alluvial environment in the Conquezuela–Ambrona
Valley (13,000 to 7540 cal yr BP)
Coarse siliciclastic sediments at the base of the sequence indicate a
dominant alluvial environment in the basin during the Lateglacial and
early Holocene (ca. 13,000–7540 cal yr BP). Alluvial fans from the
basin margins developed and reached the coring site and the center of
the basin. Unfortunately, the lack of a coherent chronological model
for this interval (Fig. 3) and the absence of pollen remains prevent
further interpretation of landscape characteristics during this period.
5.2. Early Neolithic settlements, pinewoods and ﬁrst traces of landscape
management (7540–6200 cal yr BP, 5590–4250 BC)
The mid Holocene (7540–6200 cal yr BP, 5590–4250 BC) landscape
in the Conquezuela–Ambrona Valley was characterized by a conifer
forest, mainly composed of Pinus sylvestris and/or Pinus nigra stands
with juniper (Fig. 5). More than 1600 needle fragments were discovered
in La Peña de la Abuela settlement (Fig. 2B) (Stika, 2005) and also the
anthracological data collected from archaeological sites suggest local
pinewoods dominance (Carrión and Badal, 2005). Radiocarbon dates
performed on Pinus nigra/sylvestris type charcoal remains revealed
that montane pine was the main collected taxon near La Lámpara
settlement (Fig. 2C) at least between 7136 ± 33 and 6608 ± 35 yr BP
(7965–7500 cal yr BP, 6015–5550 BC) (Figs. 7 and 8B) (Table 2). The
complete dominance of Pinus nigra/sylvestris type in the Conquezuela
palaeolake pollen record noticeably differs from other continental Med-
iterranean regions where Quercus ilex together with Quercus faginea
types were the main spread communities during this period (Carrión
et al., 2001). However, montane pinewoods dominance even during
the most humid and thermal Holocene phases, is not limited to our
study area. It has been well-documented by means ofpollen and macro-
fossil data in numerous sequences located along the Central Range
(Franco-Múgica et al., 1998; Rubiales et al., 2007; Rubiales and
Génova, in press), northern Iberian Range (Peñalba, 1994; García
Antón et al., 1995; García-Amorena et al., 2011)orintheAlbarracín
Range (Stevenson, 2000; Aranbarri et al., 2014). A modeling approach
carried out by Benito Garzón et al. (2007) coupled with the results ob-
tained by Cheddadi et al. (2006), highlights a broader distribution of
Pinus sylvestris in the Iberian Peninsula for the mid Holocene, especially
at the meso- and supramediterranean belts. Pinewood persistence in
continental Iberia throughout the whole Holocene responds to pine
ecophysiological traits as distribution is deﬁned by complex soil-
related autoecological aspects and the lack of potential competitors
(Rubiales et al., 2010). The vegetation around Conquezuela palaeolake
seems to have followed a similar pattern revealing a new example of
pinewood resilience in inner Iberia.
Regarding hydrological ﬂuctuations, the progressive change in both
sedimentological and geochemical indicators in the Conquezuela
sequence atthe top of UNIT-4 revealed the development of carbonate-
producing lake environments at least since ca. 7540 cal yr BP
(5590 BC) (Fig. 4). This depositional change from alluvial to lacustrine
reﬂects a signiﬁcant increase in the local water-table and a more posi-
tive water balance in the basin. In particular, the decrease in Zr/Rb, the
coeval increase in TIC, Ca/Ti and Sr/Ti ratios illustrate the establishment
of a carbonate lake (Fig. 4). Carbonate formation in the palustrine belt
could have been favored by the increase in temperatures. The lower Al
and Si values suggest a runoff decrease. At a regional scale, slightly
higher lake levels compared to the onset of the Holocene have been
also registered in other Mediterranean-climate sequences like Lake
Estanya (Morellón et al., 2009) or Villarquemado palaeolake
(Aranbarri et al., 2014)(Fig. 1), as a possible effect of southern penetra-
tion of westerlies (Vannière et al., 2011).
The archaeobotanical remains described by Stika (2005) in several
Ambrona sites revealed the oldest cultivated cereals in continental
Iberia dated between 7240 and 7010 cal yr BP (5290 and 5060 BC).
Triticum monococcum (einkorn) and Triticum dicoccum (emmer) domi-
nated the overall crop spectrum, but also some Hordeum vulgare
(barley) remains were identiﬁed in La Lámpara and La Revilla settlements
(Fig. 8C). The ﬁrst appearance of Cerealia type in the Conquezuela pollen
sequence occurred at ca. 7380 cal yr BP (5430 BC) although it is just a
presence not indicative of signiﬁcant agricultural activities (Fig. 5). The
limited presence of pollen grains in the sequence, however, is to be ex-
pected because of the cereal pollen production strategy, since some gen-
era are autogamous (e.g., Hordeum or Triticum) and their large pollen size
(N40 μm) greatly hampers the surface area distribution (Fyfe, 2006). Pal-
ynological data demonstrate that cereal presence is not continuously re-
corded far from cultivated ﬁelds (Mercuri et al., 2013a). In the
Ambrona–Conquezuela Valley, early agricultural practices seem to have
been conﬁned in the eastern areas, next to La Lámpara and La Revilla set-
tlements (Fig. 2C), but not necessarily around the palaeolake.
Human responses to climate variability during the Neolithic have
been widely reported in the Mediterranean Basin (Roberts et al., 2011
and references therein). Recently Fiorentino et al. (2013) concluded
that variations in agricultural practices were directlyrelated to changes
in the precipitationregime, with drastic reduction of occupation linked
to recurrent arid spells. Changes in the human livelihood strategies and
cultural trajectories seem to have been coincident to major climate
changes at the circum-Mediterranean Basin (Mercuri et al., 2011).
48 J. Aranbarri et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 436 (2015) 41–57
Although taking into account that the Neolithisation process is a really
complex cultural period with many abiotic, biotic and social factors
intrinsically involved, early Neolithic colonization of the inner regions
of Iberia seems to have occurred under warm and humid climate
conditions with settlement patterns commonly associated to large
5.3. Pinewoods deforestation, landscape management and hydrological
variability during the mid–late Neolithic and Chalcolithic
(6200–3200 cal yr BP, 4250–1250 BC)
The human impact near the Conquezuela palaeolake landscape
increased during this phase (6200–3200 cal yr BP, 4250–1250 BC),
considerably modifying the vegetation physiognomy. Pinewoods were
cleared inorder to obtain new farmlands, but probably also for building
purposes (Fig. 5)(Carrión and Badal, 2005). Anthracological data reveal
that the montane pine still was the main exploited taxon between
5308 ± 31 and 4773 ± 29
C yr BP (6085–5520 cal yr BP, 4135–
3570 BC) (Table 2)(Carrión and Badal, 2005). This is coherent with
the Conquezuela palaeolake pollen signal of a long-term use of pine
wood (Figs. 8Aand8B). Some pine wood remains presented wood-
working activity. Montane pine was probably chosen for supporting
structures like beams and posts, due to its high wood durability and
density (Ntinou et al., 2013). In fact, the mid–late Neolithic period
(6450–4950 cal yr BP, 4500–3000 BC) in the Conquezuela–Ambrona
Valley was characterized by the development of semicircular funerary
structures demanding large amount of fuel for combustion and crema-
tory practices (Rojo-Guerra et al., 2005, 2010). All the radiocarbon
dates were correlated with the high amount of Bell-Beaker pottery
fragments discovered along the numerous archaeological settlements
of the area (Fig. 2C) (Morán-Dauchez, 2006).
Weeds like Atriplex sp., Chenopodium cf. album (Chenopodiaceae),
Heliotropium cf. europaeum (Boraginaceae), Polygonum aviculare
(Polygonaceae), Fallopia convolvulus,andDescurainia sophia (Brassi-
caceae) havebeen identiﬁed as the commonplants growing in the near-
by fertile arable lands, at least during the early Neolithic (Stika, 2005).
During this period also the Conquezuela pollen spectra included
Chenopodiaceae, Polygonaceae and Brassicaceae curves (Fig. 5). Cereals
continued to be poorly represented in our pollen results. As seen in the
previous phase, only isolated grains were identiﬁed, those were not cul-
tivated in the lake surroundings. Fabaceae seem not to be especially
abundant in the pollen assemblages, neither in the archaeobotanical
ﬁnds (Stika, 2005). The Neolithic levels of Los Cascajos open-air settle-
ment (Fig. 1) reported similar conclusions (Peña-Chocarro et al.,
2005a) while in La Vaquera cave only few ﬁnds of Lens sp. (lentil) and
Vicia sativa (common vetch) were recovered from the post-Neolithic
layers (López García et al., 2003)(Fig. 1). The explanation for the rela-
tively reduced crop diversity in the settlements located along the
Conquezuela–Ambrona Valley may be attributed to the harsh environ-
mental conditions and the low fertility soils. This contrasts with the
broad spectrum of legumesproduced by the early Neolithic sites located
in the IberianMediterranean coast (Antolín et al., 2015), northern Africa
(Morales et al., 2013), or the Pyrenees (Lancelotti et al., 2014).
The exponential rise in Cichorioideae characterizing the Conquezuela
palaeolake sequence during the mid Holocene deserves a special
mention (Fig. 5). Despite high Cichorioideae pollen frequencies in Med-
iterranean archaeological contexts have been traditionally associated to
human presence, recently, it has been clearly identiﬁed as pasture indi-
cator, revealing traces of animal breeding and grazing areas where no
Fig. 8. Main vegetation composition obtained from the Conquezuela–Ambrona Valley (A) and comparison with local anthracological (B) and archeobotanical data (C). Cultural phases
describedin the text have been also introduced. Pollen-based ecological groups are deﬁnedin the Fi g. 5 caption.Charcoal identiﬁcation and SEM images havebeen obtained from Carrión
and Badal, (2005). Carbonized plant remains follow Stika, (2005).
Fig. 7. Distribution ofradiocarbon dates performed on Pinus nigra/sylvestris type macrofossils retrieved from archaeological settlements located along the Conquezuela–Ambrona Valley
(Fig. 2C). Charcoal identiﬁcation and SEM images have been obtained from Carrión and Badal, (2005). Radiocarbon dates follow Rojo-Guerra et al. (2006).
50 J. Aranbarri et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 436 (2015) 41–57
51J. Aranbarri et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 436 (2015) 41–57
apparent pollen re-deposition, concentration or preservation issues are
present (Florenzano et al., 2015). Modern pollen analogs performed in
continuously grazed areas show simultaneous, local occurrence of
Cichorioideae, Asteroideae or Cirsium type in the pollen results
(Mazier et al., 2006) similar to the assemblage recorded in the
Conquezuela palaeolake (Fig. 5) but also in the surface moss polsters
(Fig. 6). This is coeval to the rise of nitrophilous and ruderal taxa like
Plantago and Urtica (Mercuri et al., 2013b)andofGlomus, commonly
associated with trampled areas (Abel-Schaad and López-Sáez, 2013).
These characteristics, continuously recorded in our study during the
late Neolithic and Chalcolithic (Fig. 5), were followed by peaks in
Sordariales, pointing to pastureland management of the nearby
areas. Animal husbandries in intensive Neolithic farming systems
like those found in Conquezuela–Ambrona Valley, have been linked
to both production and traction as well as to woodland clearing prac-
tices (Antolín et al., 2014). The zooarchaeological data retrieved
from La Peña de la Abuela and La Sima sites (Fig. 2C) reveal the
presence of a local husbandry dominated by ovicaprine herding
with occasional remains of Bos sp. and Sus sp. (Liesau and Montero,
2005). Economic activities centered on pastureland management
and cereal farming, along with large-scale woodland deforestation
and animal production, suggests a specialized economy, a common
feature in Neolithic societies (Antolín et al., 2014).
Sedimentological and geochemical indicators from Conquezuela
palaeolake sequence reveal recurrent hydrological oscillations in a
wetland setting from carbonate-producing to more detrital depositional
environments during the 6200–3200 cal yr BP (4250–1950 BC) interval
(Fig. 4). Carbonate formation (higher Ca/Ti, Sr/Ti, TIC) and frequent
oxidation processes (higher Fe/Mn) continue to be dominant during
SUB-2C (until ca. 5120 cal yr BP, 3170 BC), highlighting the abundance
of palustrine environments in a relatively shallow lake. By contrast,
this trend is slightly reverted during SUB-2B (5120–3200 cal yr BP,
3170–1950 BC), with the simultaneous increase in detrital input
(Si, Al) along with the coeval decrease in carbonate proxies (Ca/Ti,
Sr/Ti, TIC). This short period of augmented runoff could be related to
an increase in precipitation or changes in the forest cover in the water-
shed as shown by the pollen diagram (decrease in pine, numerous
pollen indicators of disturbance) (Fig. 4).
The long-term hydrological variability recorded in Conquezuela
palaeolake from a carbonate lake to an organic-dominated wetland
reﬂect a water table lowering that matches the general western
Mediterranean palaeoenvironmental history, with higher lake levels
during the early Holocene and an increased aridity toward the mid
Holocene (Magny et al., 2012). Well-dated hydrological and palynolog-
ical sequences evidenced a remarkable shift in the precipitation regime
toward more seasonal conditions that started during the second half of
the Holocene (Di Rita and Magri, 2009; Sadori et al., 2011; Magny et al.,
2012; Magri et al., 2015). Roughly, broadleaves trees start losing their
dominance at the Iberian-scale (Carrión et al., 2010 and references
therein) while pinewoods and sclerophytes spread in continental
Mediterranean environments (Carrión and van Geel, 1999; Aranbarri
et al., 2014). Similarly, Lake Estanya (Morellón et al., 2009), Basa
de la Mora (Pérez-Sanz et al., 2013) and Villarquemado palaeolake
(Aranbarri et al., 2014)(Fig. 1)reportedatrendtowardlowerlakelevels
after ca. 5000 cal yr BP. Atmospheric mechanisms explaining pro-
nounced and recurrent droughts in the western and central Mediterra-
nean Basin, has been presumably linked to the southward migration of
the ITCZ (Di Rita and Magri, 2009; Vannière et al., 2011).
In the Conquezuela–Ambrona Valley, anthropogenic impact clearly af-
fected the surrounding vegetation structure, hampering to easily discern
its natural dynamic. Long-term disturbed landscapes like those inferred
by the Conquezuela palaeolake record likely represent locally-induced
land use changes. Nevertheless, the background trend toward an arid cli-
mate (Carrión et al., 2010; Sadori et al., 2011) may have also contributed
buffering the regional vegetation replacement and therefore, both anthro-
pogenic and climate variables should be considered as possible drivers.
5.4. Pinewoods recovery and long-termlake lowering (3200–930 cal yr BP,
1950 BC–1020 AD)
After 3200 and till 930 cal yr BP (1950 BC–1020 AD) montane
pinewood recovered (Fig. 5), although the lack of archaeobotanical
remains and macrofossil evidences make it difﬁcult to discern if pines
were located near the lake or in the surrounding mountains. Pollen se-
quences relatively close to the Conquezuela palaeolake, like Somolinos
tufa Lake (Currás et al., 2012) or Pelagallinas peatbog (Franco-Múgica
et al., 2001a)(Fig. 1), also showed the presence of pinewoods during
the late Holocene, occasionally punctuated by human-induced defores-
tation processes linked to increased ﬁre-activity and contemporaneous
rise in ruderal and nitrophilous elements. Nevertheless, a trend toward
oak dominated open woodland, shaping the present landscape, was
progressively appreciable in many different sequences during pre-
Roman (Uzquiano et al., 2011) and Roman times (Moreno et al., 2008;
Currás et al., 2012).
In the Conquezuela palaeolake sequence, woodland recovery may
have been related to a change in the local settlement pattern toward
more-strategically positioned elevations. In addition, a demographic
reduction or large-scale migration pattern may have also caused a
lower human impact in the regional vegetation. Post-Chalcolithic sites
signiﬁcantly reduced in number along the Conquezuela–Ambrona
Valley and those found were located at higher altitudes (Morán-
Although it is not possible to deﬁne the spatial distribution of
communities and human activities using exclusively regional palyno-
logical proxies, the coeval increase in Cerealia type and the rise in
arboreal pollen, mainly Pinus nigra/sylvestris type, suggest different pol-
len source areas reaching the basin. Cereal-based agriculture continued
or even spread in the Conquezuela palaeolake surroundings (Fig. 5).
Ruderals, nitrophilous taxa and indicators of pastoral activities
(Cichorioideae, Asteroideae, Cirsium/Carduus type, some Fabaceae,
Trifolium type, Chenopodiaceae, Polygonaceae) still predominated local-
ly, although in lower frequencies than during the mid-late Neolithic and
Chalcolithic periods (Fig. 8A). This maypartially reﬂect the reforestation
of wide areas by montane pinewoods, previouslydedicated to extensive
herding management (Fig. 5), and therefore, partial abandonment of
pastureland activities. In fact, Plantago and Sordariales did not attain
the high values previously recorded.
Although a lowering lake level trend started at the base of UNIT-2
(ca. 5800 cal yr BP, 3850 BC), changes in sedimentation patterns at the
base of SUB-2A (around 3200 cal yr BP, 1950 BC) suggest a decreasing
lake level conducive to development of paludal environments where
carbonate production and organic accumulation increased while
siliciclastic supply to the lake slightly decreased (Fig. 3). The onset of
UNIT-1 brought a larger hydrological shift, with the deﬁnitive coloniza-
tion of the basin by vegetation and the concomitant development of
dense sedge and reed communities (Juncus, Cyperaceae and overall,
hygro-hydrophytes) (Fig. 5).
The reduction or even absence of Iron Age, pre- and Roman-period
sites in the Conquezuela–Ambrona Valley was directly associated with
changes in the settlement patterns linked to defensive positions instead
of climatically-induced adaptations. Population migration toward urban
areas likely represented a social and economic change in an urban live-
lihood, especially under the Roman Hispania (i.e. Occilis, current town
of Medinaceli), leading reforestation processes occur in the previous
disturbed rural areas.
5.5. Agrarian landscape development between 930 and 540 cal yr BP
(1020–1410 AD) in the Conquezuela–Ambrona Valley
Forest communities presented the minimum values of the whole
sequence during this period (Fig. 5), while an agrarian landscape
expanded in the area. Cereal ﬁelds widespread as deduced by the con-
tinuous and high values of Cerealia type. Overall, the same trend was
52 J. Aranbarri et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 436 (2015) 41–57
followed by ruderals and nitrophilous taxa like Chenopodiaceae,
Brassicaceae, Fabaceae, Trifolium type and Polygonaceae (Figs. 5 and
8A). Additionally, regional sequences, like the nearby Somolinos tufa
lake (Currás et al., 2012) but also in many continental records like
Taravilla Lake (Moreno et al., 2008), Espinosa del Cerrato (Franco-
Múgica et al., 2001b), Lake Arreo (Corella et al., 2013), Lake Montcortès
(Rull et al., 2011) or Lake Estanya (Morellón et al., 2011)(Fig. 1),
showed a continuous Cerealia type curve with values up to N3% since
Roman times, indicating that the agricultural intensiﬁcation occurred
simultaneously at a regional scale. In general, cereal-based agricultural
landscape in both Northern and Southern Iberian Plateaux, as well as
in the Ebro Valley, were more intensively developed during Mediaeval
times, being barley (Hordeum vulgare) and free-threshing wheat
(Triticum aestivum/durum) the main produced crops (Alonso, 2005;
Vigil-Escalera et al., 2014).
The rise in arboricultural pollen indicators was also remarkable
(Fig. 5). Although walnut pollen is discontinuously recorded since
5330 cal yr BP (3380 BC) and therefore demonstrating its native charac-
ter (Carrion and Sanchez-Gomez, 1992), the coeval increase of olive
groves likely represent a regional cultivation especially during post-
Roman times. The synchronous increase in Olea and Juglans together
with Castanea and Vitis in the pollen assemblages have been deﬁned
as a clear marker for tracing human pressure in Mediterranean environ-
ments (Kouli, 2012; Abel-Schaad and López-Sáez, 2013; Mercuri et al.,
2013a). Nevertheless, a detailed archaeobotanical research is needed
in order to detect the local exploitation of economic valuable taxa and
infer changes in the local production systems.
The exponential rise in Sordariales along with the contemporaneous
increase in Poaceae, Plantago,Urtica,Glomus chlamydospores and
moderate Cichorioideae values suggests pasturelands management in
the watershed (Fig. 5). It is well-known that Mesta system played a
major role in Castilian rural territories since the 13th century
(Rodríguez-Picavea, 2010). Protected under the Crown of Castile,
woodlands were leaved at service of transhumant livestock shaping
the forested landscape into open pasturelands (Valbuena-Carabaña
et al., 2010).
The change toward a vegetated wetland environment with limited
open-water areas is recorded by the expansion of sedges and meadows
that densely colonized the basin (Fig. 5). The simultaneous increase in
TOC and atomic TOC/TN curves coeval to the spread of diverse hygro-
hydrophyte taxa like Juncus or Cyperaceae indicate the development
of an environment conducive to organic-rich silt deposition and peat
accumulation (Figs. 4 and 5). The continuous lake-inﬁlling is also well-
demonstrated by the expansion of Spirogyra that commonly grows
under shallow and stagnant waters (van Geel, 1978). However, the per-
sistence of submerged aquatic plants (i.e. Myriophyllum alterniﬂorum
type, Potamogeton) and NPPs like Type 128 indicative of eutrophic wa-
ters (van Geel, 1978)(Fig. 5), may reﬂect a fragmented depositional en-
vironment with small ponds near the coring site.
Climate conditions during Mediaeval times have been recently
inferred to be dry and warm at Iberian-scale (Moreno et al., 2012).
This causeda prominent changein both hydrological and vegetation dy-
namics and probably allowed the spread of many cultivars (e.g., Olea).
The development of agrarian practices and the potential role of climate
changes, however, should be analyzed carefully and when possible
using a high-resolution and multiproxy approach.
In the uppermost 15 cm sediment corresponding to the last
500 years, bioturbation processes and agricultural practices notably
disturbed the sediment. Therefore pollen and geochemical analyses
have not been taken into account (Figs. 4 and 5). In 1959, the wetland
was drained in order to expand agrarian activities and to eradicate
possible malarial-ridden swampy areas.
5.6. A human-induced origin of the current mixed oak woodlands?
One of the most conspicuous features of the Conquezuela vegetation
history is the reduced spread of evergreen and mascescent oak forest
throughout the last ca. 7540 cal yr BP (Fig. 5), especially during the
mid Holocene, when sclerophyllous woodland is well recorded in conti-
nental Mediterranean Iberia (Carrión et al., 2010; Aranbarri et al., 2014
and examples therein). In fact, pollen-based reconstructed vegetation
along the Holocene record noticeably differs from the current land-
scape, where diverse Quercus rotundifolia,Quercus faginea and
Quercus pyrenaica communities dominate in the more-protected upland
areas of Conquezuela basin (Fig. 2B). To understand the dynamics of oak
populations in the past, we have performed a palynological analysis on
modern moss samples to evaluate how current vegetation is represented
in the pollen rain at basin-scale. Overall, the pollen spectra obtained from
the moss polsters yielded a noticeable variability among them. This might
be partially explained by the degree of openness in where the samples
were collected (Fig. 6). As expected, both Quercus ilex/coccifera and
Quercus faginea/pyrenaica types are better represented in Quercus-
dominated dense patches, but they reveal a completely different pollen
signature in those samples collected from more open areas. Overall,
Pinus nigra/sylvestris type attains higher values (Fig. 6), whereas Quercus
pollen frequencies show values similar to our fossil spectra (b10%)
(Fig. 5) and to those results obtained from previous palynological works
carried out along the Conquezuela–Ambrona Valley (Ruiz-Zapata et al.,
So, different questions related to the origin of current oak woodland
remain unresolved: 1) is the current vegetation the result of a cultural
landscape where oak woodland was favored for economic purposes?
If so, since when?; 2) is it possible that climate variability occurred
during the last 500 years buffered a regional-scale landscape transfor-
mation? If so, how?; or 3) is it the sparse presence of oak pollen in the
palaeoenvironmental sequence related only to statistical facts or also
to pollen productivity and dispersal?.
Regarding the third question, a detailed study focused on oak's PPE
(Pollen Productivity Estimates) is needed (Bunting et al., 2004), but
this will be the subject of future work.
In relation to natural climate variability, the modern spread of
drought-tolerant holm oaks in the area seems not to be directly linked
Radiocarbon dates performed on Pinus nigra/sylvestris type macrofossils retrieved from
archaeological sites located along the Conquezuela-Ambrona Valley (Fig. 2B). All dates were
calibrated with Calib v. 7.0 (Stuiver and Reimer, 1993). The LA, SI, PA and TA abbreviations
refer to La Lámpara, La Sima, La Peña de la Abuela and La Tarayuela sites, respectively.
Lab. number Settlement Radiocarbon date
C AMS yr BP)
(2σ) (cal yr BP)
age (cal yr BP)
KIA 16576 LA 7136 ± 33 8014–7929 7964
KIA 16581 LA 7075 ± 44 7979–7823 7900
KIA 16580 LA 6989 ± 48 7933–7708 7825
KIA 16570 LA 6956 ± 39 7864–7690 7789
KIA 16569 LA 6920 ± 50 7858–7664 7752
KIA 16577 LA 6915 ± 33 7802–7677 7741
KIA 16575 LA 6744 ± 33 7665–7568 7605
KIA 16574 LA 6729 ± 45 7670–7556 7596
KIA 16579 LA 6610 ± 32 7525–7440 7503
KIA 16571 LA 6608 ± 35 7565–7438 7501
Bln 5349 SI 5308 ± 31 6185–5994 6086
Bln 5377 SI 5303 ± 34 6185–5990 6084
Bln 5376 SI 5048 ± 27 5898–5730 5825
Bln 5378 SI 5068 ± 33 5906–5740 5818
Bln 5349 SI 5082 ± 31 5834–5747 5815
Bln 5376 SI 5001 ± 32 5764–5650 5728
Bln 5054 PA 5110 ± 39 5833–5747 5823
Bln 5053 PA 5099 ± 39 5835–5746 5819
Bnl 5052 PA 5054 ± 39 5909–5713 5816
Bnl 5026 PA 5033 ± 32 5896–5709 5815
KIA 4781 PA 5050 ± 50 5909–5707 5808
Bln 5055 PA 5029 ± 39 5895–5706 5797
Bln 5056 PA 4773 ± 29 5589–5467 5520
Bln 5541 TA 5000 ± 38 5772–5644 5729
Bln 5540 TA 4892 ± 36 5664–5585 5626
53J. Aranbarri et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 436 (2015) 41–57
to recent climatic change. Despite the increase intemperatures record-
ed in the Mediterranean Basin during the last decades (Giorgi et al.,
2004), centennial Quercus individuals compose the current oak
woodland in the area. In addition, it is well-known that during the last
500 years climate in the Iberian Peninsula has been generally more
humid and colder (Morellón et al., 2012) in comparison to the previous
drier and warmer Mediaeval period (Moreno et al., 2012). Besides, re-
gional pollen records covering this period report pine and broadleaved
forest expansion (Moreno et al., 2008; Corella et al., 2013; Pérez-Sanz
et al., 2013), synchronous to minor glacier ﬂuctuations (García-Ruíz
et al., 2014) and sharp decreases of evergreen Quercus pollen frequen-
cies (Pérez-Sanz et al., 2013), chronologically-placed within the
Little Ice Age Period. Therefore, climate as a single driver is not able to
explain the vegetation change from pine to oak communities in the
Conquezuela–Ambrona Valley area during the last centuries, and other
variables have to be considered.
The replacement of pinewoods by evergreen Quercus communities is
not common in the Iberian palaeonvironmental literature, although
some records have evidenced the complex interplay between
anthropogenic-origin activities and Mediterranean woodland opening,
triggered by punctual perturbations such as an increased ﬁre disturbance
(Gil-Romera et al., 2010). For example in Navarrés, located in eastern Ibe-
ria (Fig. 1), palynological data reveal a prominent substitution of Pinus by
more ﬁne-prone Quercus especies as Kermes oak (Quercus coccifera)trig-
gered by intermittent episodes of anthropogenic-origin ﬁre activity
(Carrión and van Geel, 1999; Gil-Romera et al., 2010). Similar conclusions
were obtained from the recently published Neolithic site of Les Ascusses
(Fig. 1), where a slight decrease in Pinus pinea is observed followed by
the expansion of evergreen Quercus and the pyrophilous NPP Chaetomium
(Tallón-Armada et al., 2014). In the nearby Somolinos tufa Lake, Currás
et al. (2012) report a long-term substitution of Pinus by Quercus ilex
type and linked with the maximum presence of macrocharcoal in the
sediment, chronologically placed within the Muslim conquest.
Additionally, both evergreen and marcescent oaks, the dominant
taxa in current vegetation landscape of Conquezuela area, are strong
re-sprouters and they formed multi-stemmed tree forests after recur-
rent coppicing (Fig. 6, photo from CQM6). Thus, expansion of both
Quercus types is granted after disturbance, quickly recolonizing cleared
landscapes (Pons and Pausas, 2006). Nevertheless, it is not possible con-
ﬁrm that ﬁre disturbances have been the origin of current oak formation.
In any case, in the Conquezuela palaeolake it is likely that recent oak
woodlands expansion was mainly favored by human activities, shaping
the landscape into a dehesa-like ecosystem. In this kindof human-made
environment, typical of the Iberian Mediterranean landscape, econom-
ical activities are integrated with the scattered trees that are viewed as
an important part of the system (Joffre et al., 1999). The oak-dominated
woodland may have persisted under a controlled landscape manage-
ment combining cultivars and arable lands with more extensive activi-
ties like animal husbandry or accord production.
6. Final remarks
The sedimentological, geochemical and palynological proxies
performed in the Conquezuela palaeolake sequence, combined with
the archaeological surveys and archaeobotanical research carried out
in the nearby Ambrona Valley, have helped to deﬁne six main phases
of landscape transformation between 13,000and 540 cal yr BP for a con-
tinental region of inner Iberia.
1) A basin-scale alluvial environment persisted during the Lateglacial
and early Holocene (ca. 13,000–7540 cal yr BP).
2) The development of a wetland–shallow lake environment ca.
7540 cal yr BP (5590 BC) marks the onset of a phase of positive
hydrological balance that concurs with the higher temperature and
humid conditions reconstructed in many Mediterranean Iberian
sites for the mid Holocene. These favorable climate features coincide
with the beginning of the Neolithisation in the area. The regional
vegetation landscape was composed of a dense montane pine forest,
also supported by the anthracological results obtained from the
nearby early Neolithic site of La Lámpara. During this period, ﬁrst
clear but scattered agricultural(Cerealia type) and nitrophilous indi-
cators (Plantago, Brassicaceae, Polygonaceae, Urtica)appearedinthe
pollen sequence as reported in the archaeobotanical ﬁnds.
3) Hydrological oscillations characterize the period between 6300
and 3200 cal yr BP (4350 and 1250 BC), alternating carbonate-,
organic- and detrital-rich depositional sub-environments. The fre-
quency and diversity of anthropogenic-related indicators attained
the maximum representation at the expenses of the locally-
conﬁned montane pine, stressing a noticeable human pressure in
the vegetation landscape, intensiﬁed by broader climate conditions.
4) The dominance of carbonate-richwetland environments during the
period 3200–930 cal yr BP (1250 BC–1020 AD) highlights a progres-
sive inﬁlling of the lake basin, where more-organic conditions
paralleled the expansion of diverse hydroseral communities.
Pinewoods recovered during this period at regional-scale as a result
of climate and socio-economic changes, whereas anthropogenic-
related indicators still remained high in the palaeolake surroundings
denoting a marked change in the patterns of settlement.
5) After 930 cal yr BP (1020 AD) the basin was deﬁnitively colonized by
sedges and a peat-like environment was established. Woodlands
attained the minimum representation while the presence of olive
groves and walnut cultivars suggests arboricultural practices during
Mediaeval times, next to the cereal ﬁelds. Mesta system and the
well-known Mediaeval rural livelihood may have acquired especial
relevance explaining the vegetation landscape during this phase.
6) The modern landscape, deﬁned by intercalated holm oak and
marcescent oak patches, is probably result of intense human
management in order to transform the previous vegetation land-
scape into a dehesa-like system, combining both extensive herding
with agrarian activities. The timing of this vegetation landscape in
the Conquezuela surroundings remains still unknown.
The funding for the present study derives from DINAMO2 (CGL-BOS
2012-33063) and AGRIWESTMED (ERC Grant Agreement #230561)
projects, provided by the Spanish Inter-Ministry Commission of Science
and Technology (CICYT) and the European Research Council under the
European Union's Seventh Framework Programme (FP7/2007–2013).
XRF data were obtained at the XRF Core Scanner Laboratory (CRG Ma-
rine Geosciences, Universityof Barcelona). Josu Aranbarri acknowledges
the predoctoral funding provided by the Basque Country Government
(ref: FI-2010-5). Graciela Gil-Romera hold a post-doctoral contract
funded by “Juan de la Cierva”(ref: JCI2009-04345) program. Eduardo
García-Prieto and Maria Leunda are supported by predoctoralFPI grants
BES-2010-038593 and BES-2013-063753, respectively. We also thank
Elena Royofor her help with the lab procedures and the twoanonymous
referees for their valuable suggestions.
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