The Marmara region in northwestern Turkey provides a unique opportunity for studying the vegetation history in response to climate changes and anthropogenic impacts because of its location between different climate and vegetation zones and its long settlement history. Geochemical and mineralogical investigations of the largest lake in the region, Lake Iznik, already registered climate-related changes of the lake level and the lake mixing. However, a palynological investigation encompassing the Late Pleistocene to Middle Holocene was still missing. Here, we present the first pollen record of the last ca. 31 ka cal BP (calibrated kilo years before 1950) inferred from Lake Iznik sediments as an independent proxy for paleoecological reconstructions. Our study reveals that the vegetation in the Iznik area changed generally between (a) steppe during glacials and stadials indicating dry and cold climatic conditions, (b) forest-steppe during interstadials indicating milder and moister climatic conditions, and (c) oak-dominated mesic forest during interglacials indicating warm and moist climatic conditions. Moreover, a pronounced succession of pioneer trees, cold temperate, warm temperate, and Mediterranean trees appeared since the Lateglacial. Rapid climate changes, which are reflected by vegetation changes, can be correlated with Dansgaard-Oeschger (DO) events such as DO-4, DO-3, and DO-1, the Younger Dryas, and probably also the 8.2 event. Since the mid-Holocene, the vegetation was influenced by anthropogenic activities. During early settlement phases, the distinction between climate-induced and human-induced changes of the vegetation is challenging. Still, evidence for human activities consolidates since the Early Bronze Age (ca. 4.8 ka cal BP): cultivated trees, crops, and secondary human indicator taxa appeared, and forests were cleared. Subsequent fluctuations between extensive agricultural uses and regenerations of the natural vegetation become apparent.
The reconstruction of past climatic and environmental conditions is crucial to understand the living conditions and migration processes of former societies. After the first spread of modern humans into Europe during the Last Glacial (e.g., Benazzi et al., 2011; Higham et al., 2011), different population dynamics into and out of Europe followed. These population dynamics also include the spatial expansion of farming and husbandry, which happened between ca. 11 600 and 5500 years ago. The Marmara region, situated between the Mediterranean Sea and the Black Sea at the principal corridor of human dispersal from Africa via the Middle East to the Balkans, functioned as an important bottleneck for all migrated societies (Richter et al., 2012).
The Last Glacial is characterized by unstable climatic conditions changing between stadial (and glacial) conditions and milder interstadial conditions. Several rapid climate changes described as Dansgaard-Oeschger (DO) events (Dansgaard et al., 1982) and Heinrich events (Heinrich, 1988; Bond et al., 1992) occurred. DO events are associated with an abrupt warming followed by a gradual re-cooling, which are well documented in the Greenland ice core records (e.g., NGRIP members, 2004). Heinrich events are associated with cold periods (also called Heinrich Stadials (HS); Sanchez Goñi and Harrison, 2010), when ice-rafted debris deposited in the North Atlantic due to massive discharges of icebergs (Bond et al., 1992). Climatic imprints related to DO events and HS are documented in many northern-hemispheric records (e.g., Hemming, 2004; Sanchez Goñi and Harrison, 2010; Müller et al., 2011; Panagiotopoulos et al., 2014; Pickarski et al., 2015). However, the magnitude, nature, and duration of each event might have varied from region to region (Sanchez Goñi and Harrison, 2010). Therefore, further records, also in Turkey, are needed to establish a complete picture of the influence of rapid climate changes on environmental conditions (Fletcher et al., 2010).
Lake Iznik, the largest lake in the Marmara region, serves as a valuable archive to study the relationship between vegetation, climate, and anthropogenic activities. The detection of human impacts on the vegetation is particularly interesting because the eastern Marmara region has a long occupation history, and archaeological settlements are in close proximity to Lake Iznik (e.g., Roodenberg and Roodenberg, 2008).
Previous studies reconstructed the paleoenvironmental and tectonic history of the Iznik Basin and investigated Lake Iznik's recent and paleo-limnology since the late Pleistocene based on seismicity, sedimentology, geochemistry, and mineralogy (Alpar et al., 2003; Franz et al., 2006; Öztürk et al., 2009; Roeser et al., 2012; Ülgen et al., 2012; Viehberg et al., 2012; Roeser, 2014). Those studies also revealed climate-related changes of the lake level and the lake mixing (Roeser et al., 2012; Ülgen et al., 2012; Roeser, 2014). A preliminary pollen analysis inferred from Lake Iznik sediments was published by Ülgen et al. (2012). The pollen record, which is only presented in ecological plant groups, encompasses the last 2400 years. A palynological investigation of sediments from Lake Iznik encompassing the late Pleistocene to late Holocene was still missing.
To provide a better view on the environmental conditions in the Marmara region during the last ca. 31 000 years, we investigated the pollen assemblage and selected non-pollen palynomorphs (NPP) of a ca. 18 m composite profile from Lake Iznik. It comprises a continuous and undisturbed sediment record with a robust chronology (Roeser et al., 2012; Ülgen et al., 2012; Roeser, 2014). Here, we present a new vegetation and climate study, which also concerns human activities in the catchment area of Lake Iznik.
Lake Iznik (Turkish: İznik Gölü) is located in the southeast of the Turkish Marmara region (Fig. 1). The Marmara region is a tectonically active area surrounding the Marmara Sea. Lake Iznik lies at the middle strand of the North Anatolian Fault, which is the boundary between the Anatolian and Eurasian plate (Öztürk et al., 2009).
Regional overview modified from Roeser et al. (2012). Dots indicate Lake Iznik (this study) and paleo records mentioned in the discussion: Ioannina (Lawson et al., 2004), Tenaghi Philippon (Tzedakis et al., 2004; Müller et al., 2011), GeoTü SL152 (Kotthoff et al., 2008), MAR94-5 (Mudie et al., 2002), MD01-2430 (Valsecchi et al., 2012), Yenişehir (Bottema et al., 2001), MD04-2788/2760 (Kwiecien et al., 2009), Sofular Cave (Fleitmann et al., 2009; Göktürk et al., 2011), Yeniçağa (van Zeist and Bottema, 1991), 22-GC3 (Shumilovskikh et al., 2012), 25-GC1 (Shumilovskikh et al., 2014), Arslantepe (Masi et al., 2013), and Lake Van (Wick et al., 2003; Litt et al., 2009).
With a surface area of 313 km
Lake Iznik with bathymetric curves in 5 m intervals modified from Roeser et al. (2012). Dots indicate the coring locations, and squares indicate settlements.
Lake Iznik's catchment area is situated in a climatic transition zone, which
is influenced by the Mediterranean climate and the Pontic climate. Warm, dry
summers and mild, moist winters are typical for the Mediterranean climate
(Köppen, 1900). In contrast, the Pontic climate is characterized by an
absence of summer drought due to higher precipitation throughout the year and
lower mean temperatures (Kürschner et al., 1997). The annual average air
temperature at the Iznik Basin is around 14.4
Average climate data and elevation of Iznik and Orhangazi (Wester, 1989; see Fig. 2 for the locations).
The potential natural vegetation of northwestern Anatolia is divided into five vegetation zones, from which three directly influence the catchment of Lake Iznik (Fig. 3).
A band of Euxinian and sub-Euxinian mesic deciduous and mixed forest extends
along the southern and eastern coasts of the Black Sea (Zohary, 1973;
Shumilovskikh et al., 2012). In northwestern Anatolia, it reaches into Thrace
(European Turkey) and south of the Marmara Sea almost to the Aegean Sea. The
forest is dominated by oriental beech (
The Aegean coasts and southeastern coasts of the Marmara Sea are
characterized by a climax of Mediterranean woodland. According to Zohary (1973),
there is an evergreen subzone from sea level to an elevation of
1000 m and an oro-Mediterranean subzone reaching up to 1600 m. The
evergreen subzone is dominated by
Natural potential vegetation of northwestern Turkey redrawn from Zohary (1973).
However, the potential natural vegetation differs considerably from the
vegetation one will find nowadays, which is shaped by human activities of
several thousand years (Mayer and Aksoy, 1986). Due to agriculture (e.g.,
olive cultivation, cereal cropping, and husbandry), forests were cleared,
large areas were overgrazed, landscapes were burned, and soils eroded
(Zohary, 1973; Mayer and Aksoy, 1986). Former Mediterranean woodlands
degraded to macchia vegetation with
Pollen diagram inferred from Lake Iznik sediments with selected terrestrial plants in percentages, selected aquatic plants in concentrations, total pollen concentrations, total pollen influxes (pollen accumulations), and local pollen assemblage zones (LPAZ). Radiocarbon dates from plant remains (circles) and bulk organic (stars) as well as tephra positions according to Ülgen et al. (2012) and Roeser (2014) are marked.
For the current study, a composite profile was constructed by using different sediment cores, which were collected in two separate coring campaigns. All of these cores descended from the central sedimentary ridge of Lake Iznik, which separates the northern and the southern basin, at a water depth of ca. 50 m (Fig. 2). The cores were recovered from floating platforms with the help of percussion piston corers (Roeser et al., 2012; Ülgen et al., 2012).
Sediment samples for pollen analyses originated from different cores: core
IZN05/LC1 (coring location: 40
The composite profiles IZN05/SC4E&LC1 and IZN09/LC2&LC3 could be
clearly correlated through Ca
33 sediment samples from core IZN05/LC1 were taken in a mean resolution of
12.6 cm ranging from the uppermost part of the core (0.51 m composite depth)
to the AP tephra (4.58 m composite depth). After a first low-resolution
screening of the composite profile IZN09/LC2&LC3, additional samples were
processed in sections where climatic events were already known from
geochemical analysis (Roeser et al., 2012; Roeser, 2014), the temporal
resolution was very low, or palynological events were detected. Finally, 78
sediment samples from composite profile IZN09/LC2&LC3 were taken in a mean
resolution of 17.5 cm ranging from the AP tephra to the end of the record
(18.14 m composite depth). All samples had a sediment volume of mostly ca. 4 cm
For the pollen preparation of the 111 sediment samples, we followed a
standard protocol described in Faegri and Iversen (1989). The chemical
treatment included 10 % hot hydrochloric acid (HCl) to remove carbonates
(10 min), 40 % hydrofluoric acid (HF) to remove silicates (at least 48 h),
10 % hot HCl (10 min), glacial acetic acid
(C
Microscopic analyses were carried out with Zeiss Axio Lab.A1 light
microscopes using a magnification of 400. The pollen reference collection of
the Steinmann Institute (University of Bonn) and palynomorph keys (Faegri and
Iversen, 1989; Moore et al., 1991; Reille, 1995, 1998, 1999; Chester and
Raine, 2001; Beug, 2004) were used for the palynomorph identification. We
mainly followed Beug (2004) for the nomenclature of pollen types. A minimum
of 500 terrestrial pollen grains were counted in each sample (joint analyses
by Phoebe Niestrath (0.51–4.58 m) and Andrea Miebach (4.58–18.14 m)).
Obligate aquatic plants were excluded from the total pollen sum to exclude
local taxa growing in the lake (Moore et al., 1991). Furthermore, destroyed,
immature, and unknown pollen were excluded from the total pollen sum, which
was used to calculate percentages of the pollen assemblage. Pollen types were
grouped as follows: conifers, arid trees and shrubs (
Pollen diagrams were prepared with Tilia, Version 1.7.16 (©1991–2011 Eric C. Grimm). A stratigraphically constrained cluster analysis using a square root transformation was applied by CONISS (Grimm, 1987). All taxa with more than 2 % of the total pollen sum and the sum of arboreal pollen (AP) were used for the cluster analysis. On this basis and visual pattern, local pollen assemblage zones (LPAZ) were determined.
Selected pollen and spore data are presented in Fig. 4. According to the present age-depth model (Roeser et al., 2016), the temporal resolution of the record varies between 1139 and 57 years with an average of 278 years. Eight local pollen assemblage zones (LPAZ) were defined and are summarized in Table 2. The LPAZ are in agreement with previously defined lithological units, which are known to relate to specific climate phases (Roeser et al., 2012; Roeser, 2014). A complete pollen diagram with all taxa can be found in the Supplement.
Local pollen assemblage zones (LPAZ) with composite depths, ages, the number of pollen samples, the temporal resolution, main components of the pollen assemblage (AP: arboreal pollen, NAP: non-arboreal pollen, percentages refer to the total pollen sum and give minimal and maximal values for the respective LPAZ), pollen concentrations (PC), definitions of lower boundaries (LB), and the inferred dominant vegetation type.
Lake Iznik's LPAZ 8 corresponds to the transition of Marine Isotope Stages
(MIS) 3 and 2 (definition after Lisiecki and Raymo, 2005). The pollen
assemblage documents a predominance of steppe vegetation with dwarf shrubs,
herbs, and grasses dominated by wormwood (
However, two distinct rapid vegetation changes are evident, which are
characterized by an increase of grasses (Poaceae) followed by a spread of
pines, deciduous oaks (
Comparison of different proxies inferred from Lake Iznik sediments:
(a) pollen assemblage, (b) total pollen concentrations, (c) non-pollen
palynomorph (NPP) concentrations, (d) calcium/titanium (Ca
The sparse vegetation cover in the Iznik area during stadial conditions is
supported by low loads of terrestrial organic material into Lake Iznik
documented by geochemical indicators, e.g., low ratios of total organic carbon and total
nitrogen (TOC
The comparison of this study to vegetation studies from the southern Black Sea (Shumilovskikh et al., 2014; Fig. 6) and the Marmara Sea (core MAR94-5; Mudie et al., 2002) suggests a rather uniform vegetation in northwestern Turkey. However, higher pollen concentrations and higher abundances of AP in core MAR94-5 suggest a denser vegetation and more favorable conditions for tree growth in the central Marmara region (Mudie et al., 2002). The spread of deciduous oaks during DO events seems to be a general pattern in the northeastern Mediterranean, although several pollen records do not show a response to every interstadial. In fact, climatic conditions during DO-3 and DO-4 were probably still too harsh or favorable conditions were too short-lasting that several records do not show significant changes in the vegetation (Fletcher et al., 2010 and references therein).
Comparison of pollen assemblages from (a) Lake Iznik (this study), (b) Marmara Sea, core MD01-2430 (Valsecchi et al., 2012), (c) Black Sea, core 22-GC3 (Shumilovskikh et al., 2012), and (d) Black Sea, core 25-GC1 (Shumilovskikh et al., 2014) with (e) isotope data from Sofular cave (Fleitmann et al., 2009), (f) isotope data from Greenland (NGRIP members, 2004), (g) mid-June and mid-January insolation (Berger, 1978; Berger et al., 2007), and (h) marine isotope stages (MIS; Lisiecki and Raymo, 2005). Dots mark Dansgaard-Oeschger events (DO), the Younger Dryas (YD), and the 8.2 event.
A temporal offset of the Lake Iznik record is recognized by comparing it to
the NGRIP
A steppe vegetation predominated in the Iznik area during the pre-LGM and LGM
(Last Glacial Maximum, i.e., the period with maximal global ice volume dating
back to 23–19 ka cal BP according to Yokoyama et al., 2000 and Tzedakis,
2007). The abundance of the arboreal species
The geochemical and sedimentological results from Lake Iznik indicate a low
lacustrine bioproductivity coupled to a low endogen carbonate production (low
Ca
In general, most paleoclimate records and models of the Eastern Mediterranean agree on cold and arid conditions during the LGM (van Zeist and Bottema, 1988; Robinson et al., 2006; Tzedakis, 2007; Valsecchi et al., 2012 (Fig. 6); but also see Şenkul and Doğan (2013) for another conclusion). Likewise the pollen record from the southern Black Sea indicates colder and drier climatic conditions compared to today, although an increased moisture availability compared to MIS 3 allowed the expansion of woodland (Shumilovskikh et al., 2014; Fig. 6).
However, ambiguous data are present for the millennia prior to the LGM, including
the detection of rapid climate events. Although many high-resolution Eastern
Mediterranean pollen records generally document vegetation changes in
response to DO events, DO-2 (23.3–22.9 ka cal BP; Rasmussen et al., 2014)
is not registered by the majority of records (Fletcher et al., 2010 and
references therein). Compared to other DO events, the amplitude of the
The onset of LPAZ 6 corresponds to the termination of the LGM and is marked
by a ratio change of steppe components in Lake Iznik's pollen record: mainly
Steadily increasing Ca
An ongoing dominance of steppe vegetation during the post-LGM is reflected in many Eastern Mediterranean records. Still, regional variations occurred: while eastern Anatolia was dominated by a cold semi-desert steppe with almost no arboreal taxa (Litt et al., 2009), more trees (primary pines) occurred in northern Turkey (van Zeist and Bottema, 1991; Shumilovskikh et al., 2012; Fig. 6), and the amount of arboreal pollen was even higher in the Aegean region (Kotthoff et al., 2008) and in Greece (Lawson et al., 2004; Müller et al., 2011). In contrast to our study, Kwiecien et al. (2009) and Valsecchi et al. (2012) proposed harsher climatic conditions during the post-LGM compared to the LGM for northwestern Turkey in response to Heinrich Stadial 1 (18–15.6 ka cal BP; Sanchez Goñi and Harrison, 2010). Valsecchi et al. (2012) suggested colder and/or drier conditions in the Marmara region due to increased pollen percentages of steppic plants and decreased percentages of temperate trees (Fig. 6).
The onset of LPAZ 5 is characterized by shortly peaking values of Poaceae
followed by an enormous increase of deciduous oaks and a peak of
During LPAZ 5, two retreats in the forest expansion are noticeable. A peak of
The rapid increase of deciduous oaks at ca. 15 ka cal BP coincides with a
rapid rise of
During DO-1, a short phase of lower algae concentrations (Fig. 5), lower
Ca
The spread of deciduous oaks in response to the onset of DO-1 is a common
pattern in the Eastern Mediterranean. It is registered in many pollen records
from northwestern Turkey and Greece, e.g., from Tenaghi Philippon (Müller
et al., 2011), Ioannina basin (Lawson et al., 2004), the Marmara Sea
(Valsecchi et al., 2012; Fig. 6), and the southern Black Sea (Shumilovskikh
et al., 2012; Fig. 6). In addition, rapidly increasing
The retreat of mesic forests and the spread of steppic vegetation is a
typical expression of the Younger Dryas in the Marmara region (Mudie et al.,
2002; Valsecchi et al., 2012; Fig. 6) and in general in the Eastern
Mediterranean (Bottema, 1995; Rossignol-Strick, 1995). Also rapidly
decreasing
The lower boundary of LPAZ 4 coincides with the Pleistocene-Holocene
boundary, which was dated to 11.7 ka cal BP (e.g., Walker et al., 2008).
The early Holocene of Lake Iznik's pollen record is characterized by
constantly high percentages of
Pollen diagram of the last 9 ka cal BP inferred from Lake Iznik sediments with archaeological periods (Eastwood et al., 1998; Sagona and Zimansky, 2009), settlement activities of archaeological settlements in the vicinity of Lake Iznik (Ilıpınar, Hacılar tepe, and Menteşe after Bottema et al. (2001) and Barcın Höyük after Gerritsen et al. (2013a, b); see Fig 8. for the locations), the foundation of Antigoneia (later Iznik; Abbasoğlu and Delemen, 2003), and the two ecumenical councils of Nicaea (later Iznik; Şahin, 2003).
During the early Holocene, the lake level of Lake Iznik was relatively low
(Roeser et al., 2012), which resulted together with summer insolation maxima
(Berger, 1978; Berger et al., 2007; Fig. 6) in overall highest Ca
Similar to the rapid spread of forests in the Iznik area at the beginning of
the Holocene, also
The first consistent occurrence of the
The mid-Holocene in the Iznik area was characterized by a general continuing
of temperate deciduous forest and mild and warm climatic conditions (Figs. 4,
7). However, the amount of conifers raised. The increased frequency of
Several phases of decreased forest cover and simultaneous drops of pollen concentrations and influxes are visible in LPAZ 3. Potential climatic triggers causing these vegetation changes are especially probable for periods when no or few anthropogenic indicator taxa (cultivated plants and non-cultivated plants, which benefit from anthropogenic influences; e.g., Behre, 1990; Bottema and Woldring, 1990; Fig. 7) appeared simultaneously. The most pronounced of these periods are centered at ca. 8, ca. 6.5, and ca. 4.1 ka cal BP. However, the determination of the exact duration of those changes is challenging because possible rapid fluctuations of the sedimentation rate would potentially affect the duration of recorded events and eventually also bias the pollen influx. Such expected rapid fluctuations are generally not accounted for by age-depth models, which reflect rather the average sedimentation. The high synchronicity of pollen concentrations and NPP concentrations support this assumption (Fig. 5).
Several anthropogenic indicator taxa appear in LPAZ 3 (Fig. 7). For instance,
a small peak of
Moister conditions since ca. 9 ka cal BP are also suggested by geochemical
analysis from Lake Iznik (Roeser et al., 2012; Roeser, 2014). The abrupt
retreat in carbonate accumulation indicates a lake level rise that lasted
circa 500 years (decreasing Ca
Similar to the Lake Iznik record, also other studies document a moisture rise
during the mid-Holocene. An increase in humidity since ca. 9.6 ka cal BP
was inferred from the Sofular cave record based on high stalagmite growth
rates and low (
The 8.2 ka cold event is the most prominent rapid climate change (RCC) at northern high latitudes during the Holocene (Johnsen et al., 2001; NGRIP members, 2004; Fig. 6). Phases with reduced precipitation were described in several Eastern Mediterranean records, but they often lasted longer compared to the sharp and short 8.2 ka event at northern high latitudes (e.g., Staubwasser and Weiss, 2006; Kotthoff et al., 2008; Weninger et al., 2009; Göktürk et al., 2011). The vegetation change in the Iznik area around 8 ka cal BP might also correspond to the 8.2 event. However, the synchronous appearance of several archaeological settlements (Bottema et al., 2001; Gerritsen et al., 2013a, b; Fig. 7; see Fig. 8 for the locations) makes it difficult to separate anthropogenic and climatic influences on the vegetation. Also Bottema et al. (2001) considered human impacts for a contemporaneous destruction of forests in the Yenişehir area, south of Lake Iznik.
Archaeological settlements (red triangles) in the vicinity of Lake Iznik.
According to Roberts et al. (2011), a dry phase took place in the Eastern
Mediterranean ca. 6600 years ago. The forest retreat in the Iznik area
around 6.5 ka cal BP might correspond to this climate event (note that the
age-depth model during this phase is based on radiocarbon dates subjected to
reservoir effects; Roeser et al., 2014). However, the magnitude of the
vegetation change is large, which leads to the assumption of (additional)
anthropogenic influences. Although anthropogenic indicator species are rare
and there is no evidence for settlements near Lake Iznik at that time (Fig. 7),
the subsequent spread of pines might indicate a permanent opening of
forests by humans. Pines can have a pioneer role in anthropogenic influenced
landscapes, and they quickly distribute in abandoned areas (Litt et al.,
2012). Though, a similar spreading pattern of
The unambiguous evidence for human-induced vegetation changes in the Iznik area at ca. 4.8 ka cal BP is in accordance with documented settlement activities in the vicinity of Lake Iznik (Bottema et al., 2001; Gerritsen et al., 2013a, b; Fig. 7). Also Bottema et al. (2001) postulated the relationship of these settlements and a deforestation in the Yenişehir area.
According to Mayewski et al. (2004), there is evidence for an RCC at 4.2–3.8 ka cal BP in some paleo records on global scale (the so-called 4.2 ka event). A pronounced aridity prevailed in the Eastern Mediterranean around 4.2 ka cal BP, although timing and magnitude of changes varies considerably among different records (Bar-Matthews and Ayalon, 2011; Finné et al., 2011 and references therein; Masi et al., 2013). The forest retreat around ca. 4.1 ka cal BP in the Iznik area might also be associated with this dry period. However, an extensive cultural network across Anatolia was already established by the end of the Early Bronze Age (Sagona and Zimansky, 2009). Therefore, persistent anthropogenic influences on the vegetation are also possible.
During the Late Bronze Age, at ca. 3.5 ka cal BP, an enormous change in
the vegetation took place in the catchment of Lake Iznik (Fig. 7). At least
since that time, the vegetation development was overprinted by human impacts
and the detection of climate influences on the vegetation is hardly possible.
Natural forests got cleared, from which mainly deciduous oaks and pines were
affected. People probably cleared the low-altitude forests, where
A conspicuous palynologically identifiable settlement period firstly described from southwestern Turkey, the Beyşehir occupation phase (BOP), started at ca. 3.4 ka cal BP (van Zeist et al., 1975; Eastwood et al., 1998). Correlating phases in pollen records were subsequently observed in greater parts of Turkey and in the Aegean region (Eastwood et al., 1998; Bottema, 2000). The similar timing of vegetation changes in the Iznik pollen record prompts to a correlation to this phase. Although the assemblage and abundance of cultivated taxa during the BOP varies among the different records (Eastwood et al., 1998; Bottema, 2000), the secondary role of arboriculture in the Iznik area depicts a major difference compared to other records. It is still not fully understood which culture accounted for the observed vegetation changes during the BOP (Eastwood et al., 1998). The Late Bronze Age was the time of the Hittites, who dominated large parts of Anatolia. However, no Hittite sites are known from northwestern Turkey including the Iznik area. The Iron Age in northwestern Turkey was politically shaped by the Kingdom of Phrygia, which was bordered by the Assyrian Empire to its southeast and the Kingdom of Urartu to its northeast (Sagona and Zimansky, 2009).
During the Archaic and Classical Period (ca. 2.6–2.2 ka cal BP) deciduous
oaks recovered to a certain extent and open land vegetation as well as
The uppermost LPAZ is characterized by an abrupt increase of
The maximal percentages of
During the Byzantine Period (1.15–0.8 ka cal BP), a repeated foray of humans is documented in Lake Iznik's pollen record. The cultivation of olives and cereals increased once more, although it did not reach dimensions comparable to earlier times. Pines retreated quickly and strongly again, while deciduous oaks were not affected by the probable forest clearing. Simultaneously, in 787 AD (1163 BP), a second famous ecumenical council took place in Iznik (Şahin, 2003).
The uppermost part of LPAZ 1 shows a less intense human exploitation on the vegetation. The forest recovered and anthropogenic indicator taxa were not very abundant. This study covers the time period until ca. 0.55 ka cal BP (1400 AD) and therefore does not include the last centuries.
This study reveals the vegetation and climate history of the last ca. 31 000 years inferred from lacustrine sediments of Lake Iznik, the largest
lake in the Marmara region. Special emphasis is given to climate variability
based on signal analysis of biotic proxies such as pollen. A steppe with dwarf-shrubs, grasses, and other herbs dominated during
glacial/stadial conditions indicating dry and cold climatic conditions. In
particular between ca. 28.4 and 18.4 ka cal BP (MIS 2), very low pollen
concentrations and influx rates (pollen accumulation) suggest a very sparse
vegetation cover and a very harsh climate. Therefore, pollen percentages are
considerably biased amongst others by long distance transported pollen like
Forest-steppe with scattered stands of trees and shrubs (mainly deciduous
oaks and pines) developed during interstadial conditions associated with
Dansgaard-Oeschger events 4 and 3. Deciduous oaks spread rapidly since the Lateglacial, which indicates
warmer and moister climatic conditions. They were successively accompanied
by other deciduous, coniferous, and evergreen trees. The spread of forests
suffered a setback during the Younger Dryas caused by cold and/or dry
climatic conditions. Subsequent forest retreats were either caused by climatic anomalies
(particularly the 8.2 event), human influences, or a combination of both.
However, a clear anthropogenic impact on the vegetation is document in Lake
Iznik's pollen record since ca. 4.8 ka cal BP. The vegetation development
was overprinted by human impacts at least since the Late Bronze Age, which
makes it hardly possible to detect climate-induced vegetation changes. Cereals, olives, and walnuts were among the most important cultivars in
the Iznik area. Oriental planes were probably planted to provide shade in
settlements. Grape vines, mamma-ashes, stone fruit trees of the rose family
( Phases of different agricultural use alternated with phases of forest
regeneration. A strong coincidence of vegetation changes and the regional
archaeological history becomes apparent. Rapid fluctuations in pollen
concentrations since the mid-Holocene might indicate rapid changes of Lake
Iznik's sedimentation rates caused by catchment erosion.
The complete pollen and NPP data set is available online at
A part of this work is based on the unpublished master theses of Andrea Miebach and Phoebe Niestrath carried out at the Steinmann Institute at the University of Bonn under the supervision of Thomas Litt and Jens Mutke, and Thomas Litt and Georg Heumann, respectively. We thank the teams of the coring campaigns at Lake Iznik in 2005 and 2009. We acknowledge Karen Schmeling for her technical support. We are very grateful for useful discussions with Nadine Pickarski and her improvements of the manuscript. Furthermore, we thank Verushka Valsecchi, Maria Fernanda Sanchez Goñi, and Umut Barış Ülgen for providing pollen and geochemical data. We acknowledge Fabienne Marret-Davies for her help to identify dinoflagellate cysts. This project is affiliated to the CRC 806 “Our way to Europe”. We thank the German Science Foundation (DFG) for funding this project. We also thank Laura Sadori and an anonymous referee for reviewing this manuscript and Dominik Fleitmann for editorial handling. Edited by: D. Fleitmann