Vegetation history and palaeoclimate at Lake Dojran (FYROM/Greece) during the Late Glacial and Holocene

Abstract

Abstract.A new high-resolution pollen and NPPs (Non-Pollen Palynomorphs) analysis has been performed on the sediments of Lake Dojran, a transboundary lake located at the border between Greece and Former Yugoslavian Republic of Macedonia (FYROM). The sequence covers the last 12500 years and provides information on vegetational dynamics of the Late Glacial and Holocene for southern Balkans. A robust age-model, sedimentological, diatom, and biomarker analyses published previously have been the base for a multi-perspective interpretation of the new palynological data. Pollen analysis revealed that the Late Copyright statement.

Investigating the environmental interpretation of oxygen and carbon isotope data from whole and fragmented bivalve shells

“…A gap in shell fragment data (7.7-2.7 cal kyr BP) is probably due to a high lake level increasing the distance from coring location to the shore, thereby reducing the focussing of shell material and widening the non-habitable zone in the central basin due to a finer substrate. In the late Holocene, a lower lake level is suggested by fewer planktonic diatoms (Zhang et al, 2014), and is consistent with lower temperatures and a regional shift to drier conditions (Roberts et al, 2008;Thienemann et al, 2017). A change to higher δ 13 C is likely due to reduced water input (less soil CO2 inflow) and a lower precipitation to evaporation ratio, both driving higher δ 13 CDIC.…”

“…Increasing water depth and higher trophic levels are also indicated by a shift to a plankton-dominated diatom assemblage (Figure 5; Zhang et al, 2014). A change to lower δ 13 C under higher trophic levels suggests δ 13 CDIC is likely a function of increasing catchment soil development (higher AP; Masi et al, 2017;Rothacker et al, 2018), and the delivery of respired soil CO2 with low δ 13 C (as suggested for nearby Lake Ohrid; Lacey et al, 2015). A gap in shell fragment data (7.7-2.7 cal kyr BP) is probably due to a high lake level increasing the distance from coring location to the shore, thereby reducing the focussing of shell material and widening the non-habitable zone in the central basin due to a finer substrate.…”

“…The trend to lower δ 13 C starting around 10 cal kyr BP traces increasing arboreal pollen (AP), particularly mesophilous plants, and higher reconstructed temperatures (Masi et al, 2017;Thienemann et al, 2017). Increasing water depth and higher trophic levels are also indicated by a shift to a plankton-dominated diatom assemblage (Figure 5; Zhang et al, 2014).…”

“…While each individual fragment may span a few years, collectively they are presumably the remains of littoral shell beds and therefore provide a relatively low-resolution indicator of environmental change. Larger fragments were more abundant in sections of the core that broadly coincide with a higher sedimentation rate, which are associated with periods of lower lake level (Francke et al, 2013;Zhang et al, 2014;Masi et al, 2017). These periods may have been characterised by a higher energy environment capable of moving the fragments from the littoral zone to the coring location, which would also promote faster burial rates and reduce the potential for reworking.…”

“…Around 9.6 cal kyr BP, there is little difference between average δ 18 Ofrag and δ 18 Ocarb (+0.3 ‰) and average δ 18 Oshell overlaps with δ 18 Ocarb (Figure 5). The early Holocene is characterised by a rise in benthic diatom taxa suggesting a low lake level under higher temperatures (Figure 5; Zhang et al, 2014;Thienemann et al, 2017), which would reduce the lakewater temperature gradient and result in a smaller offset between δ 18 Ofrag and δ 18 Ocarb. At ~8 cal kyr BP there is a larger offset of ~ +2 ‰.…”