Geomorphic Disturbance as a Driver of Species Phenotypic Plasticity, Vegetation Cover, and Biodiversity in High-Elevation Belts

Climate change imposes increasing stress on ecosystems worldwide through rising temperatures, altered precipitation regimes, and more frequent extreme events. In high-elevated environments, these pressures are often compounded by geomorphological disturbances, which represent a major stress factor shaping vegetation dynamics and biodiversity. Understanding how plant traits and functional diversity respond to such disturbances is therefore essential for predicting ecosystem responses to ongoing environmental change.

In this study, we investigated how geomorphic disturbance influences plant functional traits and biodiversity along elevational gradients in subalpine to alpine ecosystems. We hypothesised that: (i) disturbance-driven differences in species composition leads to functional differentiation at the community level, (ii) disturbance acts as a stressor inducing intraspecific variability in functional traits, and (iii) the proportion of thermophilic species increases on disturbed plots, particularly at higher elevations. Across three study sites, we sampled the five most abundant species per plot to test the interspecific variability as well as the three most frequent species shared across plots to test the intraspecific variability along elevation gradients. Key plant functional traits (leaf area, leaf dry weight, SLA, plant height) were measured and analysed using t-tests and non-parametric statistical approaches. For explaining the differences found Generalise Additive Models were performed.

Our results showed that, at the community level, only Specific Leaf Area (SLA) differed significantly between disturbed and undisturbed plots for the five most common species (interspecific variability). Furthermore, we could observe significant differences for the relative cover of bryophytes, lichens, dwarf shrubs, and trees. For herbs and graminoids the climate-induced growth (RC1) and the improved edaphic conditions (RC2) revealed to be more important. At the species level, disturbance-related stress led to significant intraspecific trait variability in several species, highlighting flexible trait responses under changing environmental conditions. Contrary to our expectations, the proportion of thermophilic species was consistently lower on disturbed plots compared to undisturbed plots across the entire elevational gradient, although it decreased with elevation in both plot types as expected.

Overall, differences in SLA likely reflect shifts in functional group composition under disturbance stress. Observed intraspecific trait variability along abiotic and disturbance gradients provides valuable insight into the capacity of alpine plant species to adjust their morphology and physiology in response to environmental stress, with important implications for biodiversity and ecosystem resilience under climate change.