Dynamics and evolution of Turgay‐type vegetation in Western Siberia throughout the early Oligocene to earliest Miocene—a study based on diversity of plant functional types in the carpological record

Abstract

Based on ecospectra of 66 published carpofloras we study dynamics and evolution of Turgay vegetation in Western Siberia during the early Oligocene to earliest Miocene. The ecospectra are obtained using a Plant Functional Type (PFT) classification system comprising 26 herbaceous to arboreal PFTs. The carpofloras originate from seven floristic levels covering the time‐span from the Rupelian to early Aquitanian. Key elements of these levels are documented based on original collection materials. Although impacted by local edaphic conditions, the ecospectra can be interpreted in terms of changing vegetation. Our data show that warm temperate mesophytic, mixed conifer‐broad‐leaved deciduous forest assemblages persisted throughout the Oligocene and earliest Miocene in this core area of Turgai type vegetation. This is in line with comparatively stable climate conditions persisting in the studied time‐span, showing a minor temperature decline and coeval moderate increase in seasonality and precipitation. Concurrently, the reconstructed ecospectra contradict significant continental drying throughout the Oligocene and earliest Miocene. Spatial variability of the proportions of PFTs within the single floristic horizons primarily reflects local edaphic conditions. High diversities of PFTs characteristic for swamp vegetation are mainly confined to the early Oligocene and have a regional focus. Our results indicate that taxonomical diversity, particularly concerning mesic herbs and deciduous shrubs and trees, increased towards the end of the Oligocene. This increase in biodiversity probably can be attributed to an increase in rainfall and extension of terrestrial habitats after the final retreat of the Paratethys.

Oligocene vegetation of Europe and western Asia—Diversity change and continental patterns reflected by plant functional types

“…Apart from a few exceptional cases, the ecospectra obtained for Early and Late Oligocene floras of western Siberia are comparatively close to each other regarding their climatic inference. This is in line with earlier studies suggesting the persistence of relatively warm and mostly frost‐free conditions throughout the Oligocene to Early Miocene, with MAT in the order of 12–15°C and CMT at 0–7°C (Popova et al, 2019).…”

“…In western Siberia the significant decline in evergreen elements predated the EOT and the Early Oligocene floras represent the typical Turgai type (Popova et al, 2013). Mixed conifer‐broadleaved deciduous forest assemblages with a minor diversity proportion of broadleaved evergreen elements persisted in western Siberia and large parts of Kazakhstan throughout the Oligocene and earliest Miocene (Popova, Utescher, Gromyko, Mosbrugger, & François, 2019; Zhilin, 2001). A considerable increase in taxonomic diversity in the Late Oligocene of western Siberia involving the appearance of various typical Miocene taxa, for example, from the mainly deciduous Betulaceae and Rosaceae families, and a variety of zonal mesic and intrazonal herbaceous species, was probably triggered by increasing humidity (Popova et al, 2019).…”

Paleogene vegetation changes in Primorye, Far East of Russia: A study based on diversity of plant functional types

“…In the LF, the proportion of herbaceous plants is higher (0–26.3%) and varies more significantly (Table 4 and Figure 3). Usually, herbs are not well represented in LF but diverse in PF and carpofloras (Popova, Utescher, Gromyko, Mosbrugger, & François, 2018; Utescher et al (2020)). In our floras, high percentages of herbs are obtained in a single leaf flora only (the Late Eocene LF 18).…”

Early Miocene flora of central Kazakhstan (Turgai Plateau) and its paleoenvironmental implications

“…This floristic concept was introduced by Kryshtofovich (1955) and primarily implied its geographical distribution. However, in more recent studies, the Turgai flora has been treated as an ecological flora type (Dorofeev, 1963, Akhmetjev, 1985, Akhmetjev and Iljinskaja, 1989, Bruch and Zhilin, 2007; Tarasevich and Tropina, 2017, Popova et al., 2018).…”