The link between climate change and biodiversity of lacustrine inhabitants and terrestrial plant communities of the Uvs Nuur Basin (Mongolia) during the last three millennia

Abstract

The paper is focused on changes in biodiversity, the environment, and human activity in the Uvs Nuur Basin during the last three millennia based on biological and geochemical proxies from the lake Bayan Nuur. Regions with high biodiversity and relatively low anthropogenic pressures are typically the most vulnerable to both climate change and human activities. One such area is the Uvs Nuur Basin located on the north of the Great Lake Depression of Mongolia. The main objective of this study is to assess changes in the past biodiversity of the lake’s microflora and microfauna, and surrounding vegetation biodiversity in the Uvs Nuur Basin, and to determine the main drivers of diversity change. Based on the analysis of pollen and chironomids we conclude that the most humid and afforested phase was between 1400 and 1800 CE. We assume that the Little Ice Age in the Uvs Nuur Basin was humid with mean annual precipitation ca. 305 mm/year and mean July temperature about 13°C. Conversely, the warmest and most arid period was between 650 and 1350 CE with mean annual precipitation ca. 280 mm/year and mean July temperature of about 16°C, attributed to the Medieval Warm Period. The biodiversity of terrestrial plants, chironomids, and Cladocera positive react to changes in annual precipitation and July temperature, whereas diatoms do not correlate directly to the climatic factors. The diversity and the evenness of plants are strongly correlated with the change in the leading biomes. The calculated species turnover suggests no significant changes in plant and Cladocera taxa composition, but significant changes in diatom and chironomid communities. This may be explained by the instability of lake ecology due to the fluctuation of the salinity and acidity of the water. An additional aim was to assess if dung fungi in lacustrine sediments reflect changes in human population density around the lake. We found that neither historical sources of human presence nor the influx of coprophilous fungi are correlated with the inferred climate changes. Coprophilous fungi can be used as individual or additional sources of assessment for the peopling and human-related herbivore density including overgrazing of the studied area.

Holocene Temperature Variations in Semi-Arid Central Mongolia—A Chronological and Sedimentological Perspective From a 7400-year Lake Sediment Record From the Khangai Mountains

“…The TSI controlled variation in growing season temperatures at Shireet Naiman Nuur during the Late Holocene was previously described for another high-altitude site from the Mongolian Altai (Bliedtner et al, 2021). Although the MCA is not that pronounced in both records, they well reflect the Late Holocene climate anomalies that were also regionally reported from pollen reconstructions (Yang et al, 2020;Rudaya et al, 2021), a glycerol dialkyl glycerol tetraether based temperature reconstruction (Dugerdil et al, 2021) and an isotope based moisture reconstruction (Struck et al, 2022).…”

“…This cooling phase includes the Dark Ages Cold Period (DACP) and/or Late Antique Little Ice Age (LALIA) from ~1.6 to 1.2 ka BP (Büntgen et al, 2016;Helama et al, 2017). Compared to Mongolian lowland records (Yang et al, 2020;Rudaya et al, 2021;Struck et al, 2022), the following Medieval Climate Anomaly (MCA) does not appear that pronounced as a warm period in the Shireet Naiman Nuur sediments. However, colder conditions are evident during the Little Ice Age (LIA) and growing season temperatures especially decrease during the Maunder Minima (Figure 6).…”

Late Holocene Climate Changes in the Altai Region Based on a First High‐Resolution Biomarker Isotope Record From Lake Khar Nuur

“…Colder conditions prevail during the Medieval Climate Anomaly (MCA; ∼1.1-0.8 ka BP) and the Little Ice Age (LIA; ∼0.8-0.1 ka BP) at Lake Khar Nuur. Colder conditions recorded in our record during the MCA are exceptional in the region since other regional paleorecords mostly report warmer conditions during this time (e.g., Uvs Nuur basin, Rudaya et al, 2021;Bayan Nuur, Yang et al, 2020;Lake Teletskoye, Rudaya et al, 2016). However, we have to emphasize that some uncertainties might exist in the upper 45 cm of the sediment core because of a potentially slightly increased "hardwater" effect during et al, 2012).…”

“…The yellow star indicates the investigated site at Lake Khar Nuur. White dots refer to regional pollen records from the Altai: (1) Kanas Lake (Huang et al., 2018), (2) Hoton Nuur (Rudaya et al., 2009), (3) Tsambagarav ice core (Brugger et al., 2018), (4) Lake Grusha and (5) Lake Akkol (Blyakharchuk et al., 2007), (6) Lake Teletskoye (Rudaya et al., 2016), (7) Uvs Nuur basin (Rudaya et al., 2021) and (8) Bayan Nuur (Yang et al., 2020). (b) Picture of the southern part of Lake Khar Nuur and its catchment.…”

“…Geochemical analyses -namely XRF core scanning, CN analyses and their stable isotopes (δ 13 C TOC and δ 15 N) and biogenic silica (BiSi) -were carried out to characterize the lake sediment compounds (see Text S2 in Supporting Information S1 for detailed analytical information and results) and compile the Productivity The yellow star indicates the investigated site at Lake Khar Nuur. White dots refer to regional pollen records from the Altai: (1) Kanas Lake (Huang et al, 2018), (2) Hoton Nuur (Rudaya et al, 2009), (3) Tsambagarav ice core (Brugger et al, 2018), ( 4) Lake Grusha and (5) Lake Akkol (Blyakharchuk et al, 2007), (6) Lake Teletskoye (Rudaya et al, 2016), ( 7) Uvs Nuur basin (Rudaya et al, 2021) and ( 8) Bayan Nuur (Yang et al, 2020). (b) Picture of the southern part of Lake Khar Nuur and its catchment.…”