Vegetation history of Spasskaya Gora
Pollen record from Lake Krugloe indicates forest presence at the Spasskaya Gora during the last 3500 years, indicated by 59–93% arboreal pollen (AP). Although the most herbaceous plants have low pollen productivity and dispersal capability, NAP values in recent surface samples from forests vary between 11 and 35% and meadows between 40 and 77% in Spasskaya Gora (Shumilovskikh et al.
2020b), indicating high load of herbs pollen in modern open forests. In comparison, the pollen record Chernaya from a peat bog Paltinskoe located in a hemiboreal forest around 100 km NW of Spasskaya Gora shows that NAP values vary between 1 and 27% during the late Holocene (Shumilovskikh et al.
2020a). Pollen records from the East European forest -steppe (Shumilovskikh et al.
2018; Feurdean et al.
2021) show variation of AP values between 10 and 75% since the Middle Holocene, indicating that Spasskaya Gora was covered by forests rather than typical forest-steppe. Heterogenous local topography and presence of dry soil conditions due to underlying gypsum at Spasskaya Gora might have led to a formation of herb-rich deciduous forests on upland areas, suggested by presence of Greyzemic Phaeozems. Petrophytic steppe vegetation might have existed on steep slopes where rendzina is developed.
Between 3500 and 2800 years BP, pollen spectra indicate the presence of forests with pine, birch, spruce, fir and elm. High values of
Ulmus and
Picea are remarkable.
Ulmus is known to produce low amounts of pollen with moderately good dispersal that rarely travel beyond 30 km (Bradshaw and Webb
1985; Broström et al.
2008), while Abraham et al. (
2014) report high pollen productivity estimates (PPE) for
Ulmus in Czech Republik. Surface samples from Spasskaya Gora show 1% of
Ulmus in moss pollen spectra collected from plots lacking elms in 100 m radius and < 1% in 1 km radius (Shumilovskikh et al.
2020b). Today, the shore of Lake Krugloe is overgrown by
Ulmus laevis stands, which, however, results in just ~ 5% of
Ulmus pollen on the top core sample. High values up to 26% very likely indicate forests with a high proportion of elm growing in the vicinity of the lake. It is also possible that the uplands supported forests dominated by elm. The grey-luvic phaeozems in the upland areas are usually formed by deciduous forests with a herb-rich layer (Shoba
2011).
Picea is a moderate pollen producer with moderate pollen dispersal that is lower than that of pine (Broström et al.
2008). The top sample of the studied core has 9% spruce and 2% fir, reflecting the low proportions of these taxa in Spasskaya Gora. This is in accordance with the surface sample studies with rare presence of
Abies and
Picea pollen varying between 1 and 6% in the plots without fir and spruce in 100 m radius and just few trees in one km radius (Shumilovskikh et al.
2020b).
Picea reaching 30% and
Abies with 4% between 3500 and 2800 years BP strongly suggest the presence of hemiboreal forests in the vicinity of the lake to much larger extent than today.
High Poaceae values together with
Senecio-type,
Cirsium,
Sanguisorba officinalis and
Phyteuma-type indicate the presence of meadows or steppe meadows. High microcharcoal percentages are related to an increased fire activity, while few types of coprophilous fungi suggest presence of herbivores.
Glomus-type is a spore of the mycorrhizal fungi Glomeromycota, growing on plant roots. Its increase, together with a higher proportion of minerogenic content in the sediment indicates enhanced soil erosion (Kołaczek et al.
2013; Shumilovskikh and van Geel
2020; Van Geel
1978). Taken together, these indicators strongly suggest anthropogenic activities close to the lake such as lumbering, pasture or haymaking, leading to overall openness of the study area. In contrast to our observations, the known Late Bronze Age settlements are about 30 km from the lake (Fig.
3). Most possibly further archaeological investigations will bring a discovery of new sites closer to the study site.
During the period 2800–2200 years BP, the forest recovers with an increased proportion of pine and birch and a decline in elm and spruce. Denser forests around the site are indicated by a decrease in the percentages of grasses and lower diversity of herbs. Forest growth might have reduced soil erosion. Fires reduced strongly at this time. Most possibly, the area was abandoned for about 600 years. Ulmus experienced a decline, possibly due to a general climate cooling in the late Holocene.
The next occupation phase started at 2200 years BP, correlating well with the spread of the Early Iron Age Glyadenovo culture in the surroundings (Fig.
3). Anthropogenic activities such as deforestation causing further decline in pine and elm, spread of meadows and pasture, increased soil erosion and enhanced fire activities are suggested from palynological data. An intensification of activities occurred between 1600 and 1000 years BP, corresponding to the establishment of Nevolino culture sites at Spasskaya Gora (Fig.
3). Although Cerealia-type includes a range of wild species producing large pollen grains (Beug
2004), values of ~ 1% together with increased charcoal likely indicate the presence of slash-and-burn agriculture in the vicinity of the lake. Applying low PPE of Cerealia-type estimated for forest-steppe regions (Grindean et al.
2019) results in large cropland cover by REVEALS reconstructions (Feurdean et al.
2021). In general, strong anthropogenic deforestation and transformation to cropland are known from the Central and East European forest-steppe in the Early Iron Age (Shumilovskikh et al.
2018; Feurdean et al.
2021).
The period between 1000 and 200 years BP is characterized by decreasing human impact. Forest recovery with pine, birch and spruce occurred, the landscapes were less open. This reduced the soil erosion. However, a rather high amount of charcoal, high values of Poaceae and a high number of herbaceous pollen types indicate continuing anthropogenic activities in the surroundings.
The last opening up of the landscapes occurred in the last 300 years, correlating to the Russian colonisation. This period is characterized by the strongest deforestation with a reduction in spruce, pine and birch. The spread of meadows is indicated by an increase in Poaceae and diverse herb pollen assemblages. A strong increase in Cerealia-type,
Secale and the presence of
Centaurea cyanus suggests large areas with arable fields with rye and other cereals at Spasskaya Gora. Historical data demonstrate that industrial development and rapid population growth led to a massive deforestation of the pre-Ural region during the eighteenth century (Yastrebov
1970; Neulybina
1970). Ancient forests were quickly disappearing especially along the rivers through intensive deforestation, frequent fires, spreading of agriculture and widespread grazing (Siuzev
1912).
To sum up, palynological data indicate that the landscapes of Spasskaya Gora were largely forested during the Late Holocene. Opening of the vegetation ~ 3500–2800, 2200–1000 and 200 years BP-present strongly correlates with human presence and anthropogenic activities such as lumbering, agriculture, grazing and haymaking. The modern Pinus and Betula-dominated forests as well as strong opening of the vegetation appear in the last 300 years and are caused by increased human activity.
Evaluation of the concepts on the origin and development of the Kungur forest-steppe
The Tertiary as well as the Pleistocene vegetation history of the Kungur forest-steppe has so far not been palynologically studied. However, the suggested vegetation history during the Holocene can be evaluated (Fig.
6). Few existing radiocarbon-dated records from the Perm region cover the period over the last ~ 11,000 years (Elovicheva
1991; Demakov et al.
2016; Lapteva et al.
2017; Zaretskaya et al.
2020; Shumilovskikh et al.
2020a). The data suggest the presence of the open pine–birch–spruce forests during the early Holocene until ~ 8000 years BP. Most possibly, Siberian type pine–birch–spruce forest-steppe was widespread in the pre-Urals during the late glacial. The forest-steppe species might have been widespread in the region, supporting the idea of the late Pleistocene/early Holocene migration suggested by Ponomarev (
1948; Fig.
6). Record from Paltinskoe peat bog (Shumilovskikh et al.
2020a) demonstrates the spread of spruce and a gradual arrival and spread of alder at ~ 7500 years BP, elm at ~ 7200 years BP, and hazel, oak and lime after ~ 6800 years BP. Broadleaved trees probably migrated from local refugia in the Urals. Finally, fir arrived from Siberia at ~ 4000 years ago. Pollen record Osintsevo located close to the Kungur forest-steppe (Fig.
1) shows dominance of pine and birch during the entire Holocene (Elovicheva
1991). In contrast to the suggested mid-Holocene migration wave (Ponomarev
1948; Fig.
6), the well-dated records from Upper (Zaretskaya et al.
2020) and Middle Kama (Shumilovskikh et al.
2020a) do not show any long-term dry phases that could cause a northward spread of the steppe vegetation. Nevertheless, both datasets reveal a maximum of broadleaved deciduous trees between 4700 and 3400 years BP in the Upper and 4000 and 2300 years BP in the Middle Kama regions, indicating rather warm climate conditions. If the migration of warm-steppe species is unlikely during the mid-Holocene, earlier migrations of these species during the Pleistocene have to be considered. In the Kungur forest-steppe, warm-steppe species might represent relicts of long-term persisting populations similar to European steppe outposts (Kirschner et al.
2020). This issue is highly relevant for conservation purposes and should be tested by studies on macroremains, ancient DNA and population genetics.
The archive from the Lake Krugloe sheds light on the late Holocene vegetation history of the northern border of the Kungur forest-steppe. The palynological data demonstrate that during the last 3500 years, the landscapes at Spasskaya Gora were covered by hemiboreal forests with spruce, fir, pine and birch. This observation supports the ‘anthropogenic’ hypothesis, suggesting dominance of the hemiboreal forests during the Holocene (Fig.
6). However, in comparison to the typical hemiboreal forests (Shumilovskikh et al.
2020a), the forests around Lake Krugloe had either a more open or mosaic character and broadleaved deciduous species
Ulmus, Tilia, Quercus, Corylus were more abundant. Especially elm forests were widespread between 3500 and 2800 years BP. The heterogeneous relief with steep slopes allows non-woody vegetation to persist. The gypsum strata of the Kungur series of the Permian geological period causes high water permeability and therefore rather dry edaphic conditions, providing the best growing conditions for forest-steppe species (Bankovskiy
1983; Ovesnov
2009b).
The taxonomical resolution of the pollen record does not allow justification of distinctive forest-steppe species present in the past. The majority of pollen taxa indicative for the forest-steppe vegetation include entomophilous plant species with very local pollen distribution (Supplementary Table). It is reflected well by the pollen diagram from Krugloe showing mainly anemophilous taxa. From indicative forest-steppe taxa,
Adonis vernalis, Asparagus officinalis-type,
Helianthemum nummularium-type and
Sanguisorba officinalis occur or increase during the Early Iron Age deforestation phase (Fig.
5), indicating important human role in creation of open habitats suitable for forest-steppe species. Surprisingly, the palynological record from Lake Krugloe reveals the presence of
Pulsatilla alpina. In comparison to
Pulsatilla patens and
P. flavescens, which have pollen morphologically belonging to
Ranunculus acris-type,
P. alpina produces characteristic pericolpate microechinate pollen grains (Beug
2004). According to Baladehi et al. (
2013), several other species of
Anemone and
Pulsatilla produce similar pollen types:
A. coronaria, A. biflora, A. tschernjaewii and
P. albana. Pollen of
P. alpina is documented by the Krugloe record at approximately 1500 years ago, suggesting the presence of further pollen-producing species of
Anemone or
Pulsatilla, which is not present at Spasskaya Gora today.
High values of
Ulmus are most possibly a local phenomenon of the Spasskaya Gora. Peat pollen records near the village of Kriukovy (Genkel
1957) and near Kishert (Golubeva
1956) show high values of
Tilia and both
Ulmus and
Tilia, respectively. Originally, these records were correlated to the Blytt–Sernander classification and suggested to cover the entire Holocene. However, almost all records show continuous presence of
Abies, which migrated to the Middle Kama region from Siberia between 4000 and 5000 years ago (Shumilovskikh et al.
2020a; Monika Schmidt unpubl.). Therefore, we assume that the age of these peats should not be much older than 5000 years BP. In this case, spread of
Betula forests suggested by Genkel (
1957) and Golubeva (
1956) could correspond to the Early Iron Age anthropogenic activities and have secondary character (Fig.
6).
The palynological data of Lake Krugloe provides a very important message with respect to the formation of the modern forest-steppe landscapes. Distinctive vegetation opening phases and spread of forest-steppe elements correlate with more frequent fires, higher erosion and grazing (Fig.
5). Taken together, they indicate increased human activities in the past that are also confirmed by archaeological data. This speaks in favour of the “anthropogenic” hypothesis, suggesting the establishment of secondary birch forests and spread of forest-steppe species in the deforested open landscapes. A reduction in human impact led to forest recovery. Finally, pollen data clearly show that the modern forest-steppe-like vegetation with birch and pine forest patches developed over the last 300 years and should be defined as human-made.
Implementation for nature conservation
Today, a network of protected areas on the territory of the Kungur forest-steppe includes 33 defined areas with a total area of 25.8 thousand hectares, which covers ~ 3.8% of the area. However, only 20 areas with a total of 300–400 ha include steppe or forest-steppe ecosystems. In most cases, areas of steppe or forest-steppe communities are quite small, < 20 ha. Sannikov et al. (
2014a,
b) consider the current level of steppe ecosystem conservation to be insufficient. According to the Strategic Plan for Biodiversity 2011–2020 and the Aichi Targets (Strategic Plan
2011), at least 17% of terrestrial ecosystems must be covered by a network of protected areas by 2020. According with EU Biodiversity Strategy (
2030) at least 30% of the land should be protected by 2030. In 2018–2019, the proportion of protected areas in the world was 14.9% (UNEP-WCMC, IUCN and NGS
2018). In the Russian Federation it was 14.6% (Gosudarstvenniy doklad
2019) and only 10.7% in the Perm region. Within the Perm region, the protected areas are distributed unequally and just 3.8% of the total protected area is located in the Kungur forest-steppe (Buzmakov
2020). According to the plan, new protected areas in the Kungur forest-steppe have to cover over 1000 ha of well-preserved steppe communities (Buzmakov et al.
2011; Sannikov and Buzmakov
2015; Sannikov
2019).
In accordance with the guiding principle for preservation of biological and landscape diversity in Russia (Ob okhrane
2002,
2009), two forms of protection are implemented in the Kungur forest-steppe. The main form is a creation of protected areas for places with high nature conservation significance. Here, special rules for management of natural resources are implemented, strictly prohibiting ploughing, mining, campfires, construction activity but allowing ecological tourism and education, and reconstruction of existing buildings. The second form is a conservation of habitats of rare and endangered species. According to current legislation (Ob utverzhdenii
2009), human activities with a negative impact on these species are excluded. The identification and monitoring of the state of the habitats of these rare species is ensured by annual surveys to update the Red lists of Perm Region and Russia. A further potential step is the conservation of valuable soils. In the Kungur forest-steppe, such rare soils are grey and dark-grey soils (Greyzemic Phaeozems) (Eremchenko et al.
2010,
2015). The approval of the Red List of soils of the Perm Region and declaration of protection for valuable soils is planned for the near future.
The numerous studies at Spasskaya Gora and Podkamennaya Gora demonstrated that these areas represent one of the most important clusters for the preservation of the Kungur forest-steppe (Belkovskaya
1983; Gorchakovskiy
1967; Kerzhentsev and Anikina
1960; Korzhinskiy
1887,
1891; Ponomarev
1948; Shilova
1983). As a result, the natural monuments “Spasskaya gora” and “Podkamennaya gora” were declared in 1965 and 1981, respectively, and both areas were merged to one protected area “Spasskaya i Podkamennaya gory” in 2008 (Sannikov et al.
2017; Stenno
2006).
The danger of excessive human activities for steppe communities at Spasskaya Gora was documented by botanical surveys in 1976–1977 and 1980–1990 (Stenno
2006). These studies recognized factors causing the degradation of steppe ecosystems, such as ploughing of virgin steppe areas, unauthorized road building, overgrazing, campfires, and gathering of medicinal plants. A special danger is the process of synanthropization of the meadow and meadow-steppe phytocenoses. A strong need for the protection of the forest-steppe plant associations led to a total prohibition of pasturing in some protected areas of the Kungur forest-steppe at the end of 1990s (Stenno
2006). However, this led to a degradation of steppe communities through the suppression of typical steppe species by mesophyte meadow species and trees. Further active management strategies have not yet been implemented.
The results of our palaeoecological investigations from Lake Krugloe strongly suggest that the absence of human activities leads to a rapid spread of forests and a reduction of open vegetation. And vice versa, moderate human impact in the past in the form of deforestation, fires, grazing or haymaking played an important role for maintaining the open vegetation of Spasskaya Gora, providing new habitats for the spread of steppe species. Based on these data, we conclude that the prohibition of any anthropogenic activities in the protected landscape will lead to loss of diversity of steppe assemblages in mid-term. Modern (Abdullin and Shikhov
2019; Shalaumova et al.
2010; Shikhov et al.
2020) and future (Feng et al.
2019) increases in precipitation in the Urals make the problem of steppe protection more difficult to solve. We emphasize that conservation of high plant diversity has to include disturbance factors in the form of selective lumbering, prescribed fires, moderate grazing or traditional mowing management. They will contribute to a mosaic-like landscape and generate open habitats for a diversity of light-loving steppe plants. For example, Erdös et al. (
2018b) emphasize the importance of the preservation of habitat heterogeneity provided by a mosaic structure of grasslands and forests for the preservation of high diversity of forest-steppe vegetation. Furthermore, organic accumulation in soil typical for herbaceous phytocenoses increases the amount of humus, mineral forms of nitrogen, humidity, and acidity as well as reducing carbonates. In such conditions, steppe species are less competitive and can be replaced by meadow and forest species. Therefore, disturbances in form of mowing, grazing and prescribed fires lead to the removal of dead plant material, supporting steppe vegetation.
These disturbances have their pros and cons. Mowing is a purely anthropogenic process and should be implemented carefully. Heavily mechanized haymaking in early summer can lead to the disappearance of plant species that produce their fruits and seeds in late summer. However, traditional haymaking in late summer or early autumn is an established method for conservation of steppe ecosystems (Filatova
2016). Although haymaking or moderate grazing contributes to increase and sustain plant diversity in xerophytic steppe (Mirkin and Naumova
2014), it is not always sufficient to preserve steppe associations in mesophytic steppe. For example, studies in the Central Chernozem Natural Reserve demonstrate that mowing of areas over 100 years does not protect steppe species from replacement by meadow species, which is explained by establishment of more humid conditions during the last 50–60 years (Bobrovskaya et al.
2014,
2018).
Moderate grazing contributes to an increase in plant diversity by suppressing dominant species (Filatova
2016; Mirkin and Naumova
2014). Musina (
2003) emphasizes that horses are the best means of sustainable management for xerophyte associations in Bashkortostan, cattle are less favourable, and sheep pasturing leads to the strongest degradation. Brandmayr et al. (
2002) consider cattle grazing and burning as the most effective rejuvenation methods for
Stipa austroitalica. However, overgrazing can easily lead to degradation of plant communities by decreasing plant diversity, vegetation cover, height of herbs and grasses and by causing the spread of weeds and intensifying soil erosion (Mirkin and Naumova
2014; Morozova
1985).
The positive influence of fires on animals, plants and soil fertility has been shown by multiple studies of grassland ecosystems (e.g. Basov and Zakharova
2002; Beal-Neves et al.
2020; Smelianskiy
2015). Fire is successfully used in the steppe natural reserves “Galich’ya gora” (Danilov and Nedosekina
2005), “Mikhailovskaya tselina” (Tkachenko
1999; Tkachenko and Lisenko
2005) and “Askanii-Nova” (Shalyt and Kalmykova
1935). The decrease in the natural frequency of wild fires in the western USA at the end of the nineteenth century led to the overgrowth of the steppe by juniper (Miller and Rose
1999; Davies et al.
2019). However, many studies report a negative influence of wild fires on steppe biocenoses. In southern xerophytic steppe, pyrogenic damage has long-term consequences. Strong vegetation transformation has been documented at frequencies of one or more fires in 3 years and in the middle of the growing season (Smelianskiy
2015). A decrease in soil fertility and stability was observed over 2–3 years after fire in the xerophytic steppes of the southern Urals (Galaktionova and Vasilchenko
2019). In addition to overgrazing and climate change, wildfires might have caused the regional degradation of steppes in Mongolia (Liu et al.
2013).
Although the data of our study strongly suggest integrating disturbance into management strategies for the protection of the highly diverse Kungur forest-steppe, the elaboration of a specific regime in the protected landscape ‘Spasskaya and Podkamennaya Gory’ requires special studies and scientific assistance. The choice and combination of methods, as well as their timing and frequency, has to consider individual features of vegetation assemblages, their relief and forest proximity.