Tundra ecosystems are vulnerable to hydrocarbon development, in part because small-scale, low-intensity disturbances can affect vegetation, permafrost soils, and wildlife out of proportion to their spatial extent. Scaling up to include human residents, tightly integrated arctic social-ecological systems (SESs) are believed similarly susceptible to industrial impacts and climate change. In contrast to northern Alaska and Canada, most terrestrial and aquatic components of West Siberian oil and gas fields are seasonally exploited by migratory herders, hunters, fishers, and domesticated reindeer (Rangifer tarandus L.). Despite anthropogenic fragmentation and transformation of a large proportion of the environment, recent socioeconomic upheaval, and pronounced climate warming, we find the Yamal-Nenets SES highly resilient according to a few key measures. We detail the remarkable extent to which the system has successfully reorganized in response to recent shocks and evaluate the limits of the system’s capacity to respond. Our analytical approach combines quantitative methods with participant observation to understand the overall effects of rapid land use and climate change at the level of the entire Yamal system, detect thresholds crossed using surrogates, and identify potential traps. Institutional constraints and drivers were as important as the documented ecological changes. Particularly crucial to success is the unfettered movement of people and animals in space and time, which allows them to alternately avoid or exploit a wide range of natural and anthropogenic habitats. However, expansion of infrastructure, concomitant terrestrial and freshwater ecosystem degradation, climate change, and a massive influx of workers underway present a looming threat to future resilience. tundra disturbance Rangifer tarandus reindeer nomadism oil and gas activities remote sensing

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High resilience in the Yamal-Nenets social-ecological

Tundra ecosystems are vulnerable to hydrocarbon development, in part because small-scale, low-intensity disturbances can affect vegetation, permafrost soils, and wildlife out of proportion to their spatial extent. Scaling up to include human residents, tightly integrated arctic social-ecological systems (SESs) are believed similarly susceptible to industrial impacts and climate change. In contrast to northern Alaska and Canada, most terrestrial and aquatic components of West Siberian oil and gas fields are seasonally exploited by migratory herders, hunters, fishers, and domesticated reindeer (Rangifer tarandus L.). Despite anthropogenic fragmentation and transformation of a large proportion of the environment, recent socioeconomic upheaval, and pronounced climate warming, we find the Yamal-Nenets SES highly resilient according to a few key measures. We detail the remarkable extent to which the system has successfully reorganized in response to recent shocks and evaluate the limits of the system's capacity to respond. Our analytical approach combines quantitative methods with participant observation to understand the overall effects of rapid land use and climate change at the level of the entire Yamal system, detect thresholds crossed using surrogates, and identify potential traps. Institutional constraints and drivers were as important as the documented ecological changes. Particularly crucial to success is the unfettered movement of people and animals in space and time, which allows them to alternately avoid or exploit a wide range of natural and anthropogenic habitats. However, expansion of infrastructure, concomitant terrestrial and freshwater ecosystem degradation, climate change, and a massive influx of workers underway present a looming threat to future resilience.

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High resilience in the Yamal-Nenets social–ecological system, West Siberian Arctic, Russia

The ongoing climatic changes potentially affect plant growth and the functioning of temperature-limited high-altitude and high-latitude ecosystems; the rate and magnitude of these biotic changes are, however, uncertain. The aim of this study was to reconstruct stand structure and growth forms of Larix sibirica (Ledeb.) in undisturbed forest–tundra ecotones of the remote Polar Urals on a centennial time scale. Comparisons of the current ecotone with historic photographs from the 1960s clearly document that forests have significantly expanded since then. Similarly, the analysis of forest age structure based on more than 300 trees sampled along three altitudinal gradients reaching from forests in the valleys to the tundra indicate that more than 70% of the currently upright-growing trees are o80 years old. Because thousands of more than 500-year-old subfossil trees occur in the same area but tree remnants of the 15–19th century are lacking almost entirely, we conclude that the forest has been expanding upwards into the formerly tree-free tundra during the last century by about 20–60 m in altitude. This upward shift of forests was accompanied by significant changes in tree growth forms: while 36% of the few trees that are more than 100 years old were multi-stem tree clusters, 90% of the trees emerging after 1950 were single-stemmed. Tree-ring analysis of horizontal and vertical stems of multistemmed larch trees showed that these trees had been growing in a creeping form since the 15th century. In the early 20th century, they started to grow upright with 5–20 stems per tree individual. The incipient vertical growth led to an abrupt tripling in radial growth and thus, in biomass production. Based on above- and belowground biomass measurements of 33 trees that were dug out and the mapping of tree height and diameter, we estimated that forest expansion led to a biomass increase by 40–75 t ha � 1 and a carbon accumulation of approximately 20–40 g C m � 2 yr � 1 during the last century. The forest expansion and change in growth forms coincided with significant summer warming by 0.91C and a doubling of winter precipitation during the 20th century. In summary, our results indicate that the ongoing climatic changes are already leaving a fingerprint on the appearance, structure, and productivity of the treeline ecotone in the Polar Urals.

Expanding forests and changing growth forms of Siberian larch at the Polar Urals treeline during the 20th century

Kirdyanov, A V, Hagedorn, F, Knorre, A A, Fedotova, E V, Vaganov, E A, Naurzbaev, M M, Moiseev, P A & Rigling, A 2012 (January): 20th century tree-line advance and vegetation changes along an altitudinal transect in the Putorana Mountains, northern Siberia Boreas, Vol 41, pp 56–67 101111/j1502-3885201100214x ISSN 0300-9483



Ongoing climatic changes potentially affect tree-line ecosystems, but in many regions the observed changes are superimposed by human activities We assessed how the forest-tundra ecotone has changed during the last century in the Putorana Mountains, northern Siberia, an extremely remote and untouched area in Eurasia A space-for-time approach was used to determine the spatio-temporal dynamics of forest structure and biomass along an altitudinal transect From the closed larch forest to the upper tree line, the mean age of Larix gmelinii (Rupr) decreased considerably from 220 to 50 years ago At the current upper species line, there is a strong and successful germination of larch, with 1500 saplings per hectare, indicating an ongoing filling-in, a densification of a formerly open forest and an upslope shift of the tree-line position (approximately 30 to 50 m in altitude during the last century) The forest expansion coincided with large increases in winter precipitation during the 20th century In contrast, tree growth rates were significantly positively related to summer temperatures, neither of which increased markedly The total aboveground biomass decreased from approximately 40 t ha−1 in the closed larch forest to 5 t ha−1 at the tree line Our study demonstrates that ongoing climatic changes lead to an upslope expansion of forests in the remote Putorana Mountains, which alters the stand structure and productivity of the forest-tundra ecotone These vegetation changes are very probably of minor importance for aboveground carbon sequestration, but soil carbon data are needed to estimate the impact of the forest expansion on the total ecosystem carbon storage

20th century tree-line advance and vegetation changes along an altitudinal transect in the Putorana Mountains, northern Siberia

Biome interfaces are expected to exhibit chorological symmetry, i.e., decreasing trends in the number of species associated with each of the two neighbouring biomes as we progress from one into the other. Our aim was to test for such a pattern within the forest steppe biome, which is a transition zone in itself between the temperate deciduous forests and the steppe biome. Presence of chorological symmetry would provide indirect evidence for the prehuman presence of zonal steppes in the Carpathian basin. We also whished to provide an example with this analysis for drawing biogeographical conclusions based on quantitative species occurrence data, an information source hitherto neglected in Central Europe. Occurrence patterns of forest and steppe species were analysed at the Duna-Tisza koze (Danube-Tisza Interfluve) by the traditional qualitative biogeographic method and by hierarchical classification of predicted spatial pattern based on Generalized Linear Models with logistic link function. Species presenc...

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Is chorological symmetry observable within the forest steppe biome in Hungary? — A demonstrative analysis of floristic data

Interest in studies on the rate of plant debris decomposition (however labor-consuming they are) is maintained owing to the desire to comprehensively describe the structural and functional characteristics of the Earth’s biogeocenotic cover and to solve the problem of monitoring and long-term prognosis. Numerous attempts to use a simplified approach to the assessment of decomposition rates (substitution of plant samples by standard cellulose squares or one-year experiments followed by extrapolation of their results to a longer period of time) stimulated us to perform a critical analysis of the properties and limitations of the methods most widely used in the field (Andreyashkina, 1987).

On Assessing Decomposition Rates of Plant Debris and Standard Cellulose Samples in Tundra Communities

Parameters of the production and destruction processes in different types of tundras are compared. It is shown that there is a fairly high degree of correspondence between the structure of tundra communities and the ecotopes occupied by them. On the other hand, typologically similar lowland and mountain tundras markedly differ in the functional respect. The rate of decomposition processes is higher under environmental conditions of the mountain tundra belt.

On characteristics of production and destruction processes in lowland and mountain tundras of the extreme north.

Specific features in the overgrowing of technogenically disturbed areas with completely destroyed soil and plant cover (a sand pit, a causeway, and an off-road vehicle trail) have been studied in the environs of the Bovanenkovo Oil-Gas Condensate Field. It is shown that the vegetation of natural ecotopes and ecotopes disturbed approximately 20 years ago is characterized by a relatively high similarity in the composition of vascular plants. The total species composition of plant communities (including mosses and lichens) and their structure show a considerable loss of floristic and phytocenotic diversity.

Composition of plant communities in natural and technogenically disturbed ecotopes on watersheds of the Yamal Peninsula: Floristic diversity

Typologically identical (dwarf birch-herb-dwarf shrub-moss) open and closed larch forests growing on the same altitudinal transect have proved to differ in the structural-functional organization of lower vegetation layers. Coverage, general species composition, and species richness of the herb-dwarf shrub layer are higher in the open forest than in the closed forest. Correlations between individual species of vascular plants weaken upon transition from the open to the closed forest. Conversely, the coverage of the lichen-moss layer increases in the closed forest, which contributes to its role as a factor of selection of vascular plant species against the background of the prevailing influence of the tree layer.

Structural-functional organization of lower vegetation layers in tree communities of the upper timberline ecotone in the Polar Urals

Global climate warming in the past centuries is an irrefutable fact. According to the INTAS project no. 010052, the regions of early response to climate change in Eurasia include the Polar Urals (the eastern macroslope in the vicinity of Mount Chernaya), where the spatiotemporal dynamics of forest vegetation at the timberline is being studied (Shiyatov and Mazepa, 2002). Such studies at the timberline and the upper limit of separate tree growth (these terms should be distinguished; Berg, 1947) should involve an analysis of the structure and productivity of lower vegetation layers in tree communities. Such an analysis should also be performed in the tundra communities situated at higher elevations, because it is there that the limit of distribution of separate trees and open forests ascends due to climate warming. In the Polar Urals, this limit moved upward for 20–40 m over the period from 1910 to 2000 (Shiyatov, 2003).

N. I. Andreyashkina

Papers

On Assessing Decomposition Rates of Plant Debris and Standard Cellulose Samples in Tundra Communities

On characteristics of production and destruction processes in lowland and mountain tundras of the extreme north.

Composition of plant communities in natural and technogenically disturbed ecotopes on watersheds of the Yamal Peninsula: Floristic diversity

Structural-functional organization of lower vegetation layers in tree communities of the upper timberline ecotone in the Polar Urals

Changes in Plant Cover Structure and Productivity along an Altitudinal Gradient (the Polar Urals)