A modern analogue of the Pleistocene steppe‐tundra ecosystem in southern Siberia

Abstract

Steppe‐tundra is considered to have been a dominant ecosystem across northern Eurasia during the Last Glacial Maximum. As the fossil record is insufficient for understanding the ecology of this vanished ecosystem, modern analogues have been sought, especially in Beringia. However, Beringian ecosystems are probably not the best analogues for more southern variants of the full‐glacial steppe‐tundra because they lack many plant and animal species of temperate steppes found in the full‐glacial fossil record from various areas of Europe and Siberia. We present new data on flora, land snails and mammals and characterize the ecology of a close modern analogue of the full‐glacial steppe‐tundra ecosystem in the southeastern Russian Altai Mountains, southern Siberia. The Altaian steppe‐tundra is a landscape mosaic of different habitat types including steppe, mesic and wet grasslands, shrubby tundra, riparian scrub, and patches of open woodland at moister sites. Habitat distribution, species diversity, primary productivity and nutrient content in plant biomass reflect precipitation patterns across a broader area and the topography‐dependent distribution of soil moisture across smaller landscape sections. Plant and snail species considered as glacial relicts occur in most habitats of the Altaian steppe‐tundra, but snails avoid the driest types of steppe. A diverse community of mammals, including many species typical of the full‐glacial ecosystems, also occurs there. Insights from the Altaian steppe‐tundra suggest that the full‐glacial steppe‐tundra was a heterogeneous mosaic of different habitats depending on landscape‐scale moisture gradients. Primary productivity of this habitat mosaic combined with shallow snow cover that facilitated winter grazing was sufficient to sustain rich communities of large herbivores.

Habitats of Pleistocene megaherbivores reconstructed from the frozen fauna remains

“…In contrast, the similarity to steppe vegetation types was lower than we could expect if the predominant ecosystem were the steppe-tundra complex. Only recently, Chytrý et al (2019) proposed the Altai Mountains ecosystem in southern Siberia to be a close modern analogue of the LGM steppetundra biome, supporting their suggestion by multi-proxy evidence based on flora, fauna and long-term climate stability. They described the steppe-tundra as a predominantly treeless landscape mosaic of several habitat types (including woodlands) depending on precipitation and topography-related distribution of moisture across the landscape.…”

“…Deducing from the number of megafauna finds (Ukraintseva 2013), it is supposed that northern Siberia and Beringia offered suitable habitats to large populations of megafauna over most of the Pleistocene (Guthrie 1990, Zimov et al 1995. Although low-productive habitats might have been common in the landscape, we can expect that animals preferentially selected more productive vegetation bound to mesic or wet sites (see also Chytrý et al 2019, or recent meta-analysis of stable isotopes from mammoth bone collagen by Schwartz-Narbonne et al 2019). In general, the biology and feeding ecology of extinct megaherbivores can be reconstructed based on the morphology of particular species, biology and ecology of their closest living relatives, although with some degree of uncertainty.…”

“…In general, our results are similar to the reconstructions proposed in the previous literature, however, both macrofossils and to a lesser extent also pollen data indicate higher representation of tundra vegetation, while previous reconstructions suggested tundra to be limited to maritime areas (Troeva et al 2010). It is possible that tundra was not covering the landscape continuously; it may have occurred in discontinuous patches on windexposed elevations or in wet depressions (compare Yurtsev 2001, Chytrý et al 2019.…”

“…However, there are several differences between the mountain systems of southern Siberia and northern Siberia and Beringia. Firstly, northern Siberia and Beringia currently lack many steppe species typical of European and southern Siberian LGM steppe-tundra (Yurtsev 1982, Chytrý et al 2019. Similarly, many typical species of the LGM mammalian fauna have never occurred in the north (Pavelková Řičánková et al 2014(Pavelková Řičánková et al , 2018.…”

Coleoptera assemblages from the Quaternary deposits of Kizikha river, the southernmost late Pleistocene insects of the West Siberian Plain

“…Many of these species are known from Chuiskaya Hollow and neighbouring territories of South-Eastern Altai and this fact may affirm similarity between recent landscapes of South-Eastern Altai and late Pleistocene landscapes of southern part of West Siberia. A conclusion about close similarity of the contemporary ecosystems of South-Eastern Altai and Pleistocene steppe-tundra of Southern Siberia and Europe has been deduced on the basis of plant and small mammal material (Chytrý et al, 2019).…”