The research team, publishing in the journal Caucasiana, examined plant community structure along an elevation gradient spanning 1,884 to 2,685 metres above sea level, covering montane, subalpine, and alpine vegetation zones. They compared 36 ski piste plots — 18 on standard tracks and 18 on eroded sections crossed by maintenance roads — with 25 adjacent undisturbed control plots. In total, 211 plant species were recorded across the 62 sampled plots, with 103 species occurring in at least five plots retained for multivariate analysis. The study area has a long and layered history of human use: alpine skiing has been practised on this mountain since 1932, and before that the terrain served as summer pasture, a grazing tradition that continues today with cattle and sheep transferred to the mountain from late May until September.

The statistical architecture of the study was rigorous. Principal Component Analysis (PCA) in between-group mode revealed that the first component, explaining 66.91% of total variation, was strongly associated with bare soil surface (negatively) and with soil depth, species richness, and aboveground biomass (positively). In other words, the dominant axis of variation in the data was not elevation or slope — the natural environmental variables that dominated the second component — but a gradient of human impact intensity. A subsequent Canonical Correspondence Analysis (CCA), using the PCA components as composite environmental variables and based on Bray–Curtis dissimilarity, confirmed that species distributions closely tracked this impact gradient. Both CCA axes were highly significant (p < 0.001, 999 permutations), with the first axis accounting for 68.62% of constrained variation and clearly separating control plots from disturbed ones.

Hierarchical cluster analysis, using Jaccard distances and Ward’s minimum-variance linkage, identified four floristically distinct groups whose membership was significantly associated with plot category (χ² = 21.10, simulated p = 0.0005). The first cluster was dominated by control plots, representing undisturbed habitats; the second contained predominantly eroded and track plots, reflecting moderate-to-high disturbance; the third was compositionally heterogeneous, corresponding to transitional communities at higher elevations where harsh abiotic conditions exert a strong compositional filter; and the fourth was small and predominantly control-associated. Together, the clusters confirmed that disturbance is a primary determinant of compositional differentiation, with natural environmental variation playing a secondary role, particularly at extreme elevations where control and track plots showed greater similarity — possibly because extensive artificial snowmaking at lower elevations shortens the growing season and reduces diversity there.

Indicator Species Analysis (ISA), performed with the IndVal.g association measure and 999 permutations, revealed clear floristic signatures for each condition. Undisturbed control plots were characterised by typical alpine meadow species: Gentiana septemfida (IndVal 0.683), Bromus variegatus (0.670), Veratrum lobelianum (0.636), Bistorta carnea (0.628), and Silene saxatilis (0.585). Eroded plots were associated with disturbance-tolerant taxa — Draba hispida (0.451) and Arctium lappa (0.427) — while track plots were most strongly characterised by Calamagrostis pseudophragmites (0.430), a compaction-tolerant grass that thrives in compressed soils and along drainage channels. Notably, two species — Rhinanthus major var. apterus (0.722) and Anthoxanthum odoratum (0.690) — were shared indicators of control and track plots, suggesting that moderate piste disturbance does not eliminate all meadow-adapted species. Rhinanthus, a summer annual, is less affected by winter mechanical stress, and the vegetation gaps created by disturbance may actually facilitate its seed germination.

The biomass data were equally dramatic. Mean aboveground biomass on control plots reached 2,526 kg per hectare — 2.1 to 3.0 times higher than on track plots (1,175 kg ha⁻¹) and eroded plots (833 kg ha⁻¹). Vegetation cover on control plots averaged 85%, with maximum herbaceous height of 68 cm, compared with just 45% cover and 44 cm maximum height on piste plots, where minimum cover occasionally dropped as low as 15%. A further PCA of functional-group biomasses showed that the first component (74.1% of variation) was positively associated with soil depth and the biomasses of all three functional groups, especially graminoids, indicating that deeper soils sustain higher productivity. Graminoid biomass on control plots was 2.5 times higher than on track plots and 3.5 times higher than on eroded plots; forb biomass was three times higher than on track and four times higher than on eroded plots.

Perhaps the most intriguing finding concerns legumes. Unlike graminoids and forbs, which declined sharply under disturbance (both differing significantly among land-use types, p < 0.001), legume biomass was statistically indistinguishable among land-use types (p = 0.515) and increased strongly over time across all categories (p < 0.001). The researchers attribute this resilience to nitrogen fixation, which gives legumes a competitive advantage in the nutrient-poor soils characteristic of high-altitude environments. Nitrogen limitation is a prominent feature of such soils, and legumes are frequently among the first colonisers of degraded alpine substrates. The elevated legume biomass on piste plots could also partly reflect deliberate sowing during restoration, as practised in some European ski areas. This contrasts with findings from the Pyrenees, where very intense mechanical disturbance reduced even legume cover — suggesting that the degree of impact, soil phosphorus levels, and mechanical disturbance are interdependent limiting factors.

Temporal monitoring from 2020 to 2023 painted a sobering picture of recovery capacity. Control plots showed stable or increasing biomass, with forb biomass increasing significantly between 2020 and 2021 (p = 0.0019), likely reflecting natural inter-annual variation. Eroded plots showed no significant temporal changes at all (p > 0.3), indicating persistent environmental stress and essentially no recovery. Track plots exhibited a modest increase in graminoid biomass between 2020 and 2021 (p = 0.044) that did not persist into 2023 — brief episodes of partial recovery that were insufficient for sustained restoration. Linear mixed-effects models, with year and land-use type as fixed effects and plot as a random effect, confirmed these patterns. The absence of any significant change on eroded plots over the study period points to ongoing environmental stress, and the short-lived graminoid increase on track plots suggests that recovery trajectories, where they occur at all, are multi-year processes consistent with experimental restoration studies in the Alps.

The context makes these findings urgent. Tourism is central to Georgia’s economy: in 2025 the country received over 5.5 million international visitors, nearly twice its resident population, and mountain and ski resorts recorded a 340% increase in visitor numbers between 2010 and 2017. The National Tourism Strategic Plan explicitly provides for the expansion of ski piste infrastructure. Bakuriani, among the most visited ski resorts in Georgia, hosted the freestyle ski and snowboarding world championships in 2023, events that further intensify impacts on piste vegetation. The resort sits within the Borjomi Municipality, adjacent to the Borjomi-Kharagauli National Park — one of the most extensively protected regions in the Caucasus — and is recognised as one of the most thoroughly documented floristic localities in the country. Yet no study had previously assessed the condition of vegetation on its pistes, nor on any piste in the South Caucasus.

The study’s authors recommend that future piste development minimise soil disturbance, prioritise ecological restoration of eroded sections using locally sourced seed mixtures, and incorporate long-term vegetation monitoring as a standard component of ski resort management. They also note limitations: control plots were situated 50–100 metres from the piste boundary, so indirect effects extending beyond that distance cannot be completely excluded, and the relatively short monitoring period limits the ability to distinguish persistent recovery trends from interannual climatic variability. Grazing, which occurs on and adjacent to the pistes throughout summer, likely interacts synergistically with skiing impacts — piste vegetation already weakened by soil compaction and erosion is particularly vulnerable to herbivory and trampling. The semi-natural grasslands of the Caucasus have been shaped by thousands of years of pastoral management, support exceptional plant diversity, and form a distinctive element of the mountain landscape. Reconciling the economic importance of ski tourism with the conservation of this unique heritage, the researchers conclude, requires careful ecological assessment and adaptive management — measures essential for protecting the Caucasus mountain biodiversity that draws visitors to these slopes in the first place.

Subject of Research: Ecological impacts of ski piste construction and maintenance on mountain grassland vegetation in the Lesser Caucasus, Georgia

Article Title: Vegetation of Ski Pistes in the Lesser Caucasus (Bakuriani, Georgia): Species Composition, Functional Traits, and Temporal Dynamics

Article References: Vegetation of Ski Pistes in the Lesser Caucasus (Bakuriani, Georgia): Species Composition, Functional Traits, and Temporal Dynamics. (n.d.). https://doi.org/10.3897/caucasiana.5.e207119

Image Credits: AI Generated

DOI: 10.3897/caucasiana.5.e207119

Keywords: ski tourism, Lesser Caucasus, Bakuriani, plant biodiversity, biomass, restoration ecology, Vegetation, Pistes, Lesser, Caucasus, Georgia, Species