Recent changes in alpine vegetation differ among plant communities

Abstract

Aim Reports on recent changes in high‐mountain vegetation are mostly based on re‐surveys of mountaintop floras. Summits are very specific habitats, however, and detected trends may not necessarily represent alpine vegetation in general. Here, we analyse re‐samples of three prevalent plant communities in non‐summit alpine habitats (snowbeds, two grassland types). Location Northeastern European Alps. Methods In 2013 we re‐sampled a total of 91 relevés of three plant communities from the 1990s. We compared original and re‐samples in terms of species richness (α‐diversity), pair‐wise compositional dissimilarity (β‐diversity) and species pool size (γ‐diversity). Moreover, we calculated mean ecological indicator values (temperature, moisture, nutrient status and soil acidity) as well as potential plant height for each of the 182 relevés. Differences in species pool sizes between the two sampling campaigns were evaluated by randomization tests based on rarefaction curves. In all other cases, differences were compared using paired t‐tests or Kruskal–Wallis tests. Results Of all the community attributes analysed, changes were most consistent with respect to increasing mean species' temperature indicator values. Mean potential plant height also increased slightly in all three communities, but differences were statistically significant only in the case of Carex sempervirens grasslands. Changes in species richness varied among communities, with only the Carex firma grasslands accumulating significantly more species at both the local and regional scales. For the other two plant communities, α‐ and γ‐diversity remained constant, but β‐diversity increased. Indicator values other than temperature either did not change or changed idiosyncratically in the different communities. Conclusions Our results indicate that some long‐term changes occurred in high mountain grassland and snowbed vegetation of the study area. Consistent changes in mean species' temperature indicator values suggest that climate warming was an important driver. However, trends in biodiversity metrics differed substantially between the studied communities. We conclude that recent increase in species numbers commonly reported from temperate and boreal mountaintops cannot readily be generalized to all temperate and boreal high‐mountain vegetation.

Extinction debts and colonization credits of non-forest plants in the European Alps

“…While modeling studies have predicted considerable lags in the future response of Alpine plants to climate warming 15 , empirical data about dynamics of the recent past appear contradictory. Some studies concluded that mountain vegetation follows climate almost without delay 5,17 , whereas other results indicated considerable inertia, especially in case of subalpine and alpine grassland vegetation 31,32 . Importantly, most empirical analyses available so far took a ‘community perspective’, i.e., they analyzed how local assemblages of plants have reacted to climate change in terms of attributes like species richness or composition 5,17 .…”

Low resistance of montane and alpine grasslands to abrupt changes in temperature and precipitation regimes

“…Hence, our results suggest that montane grasslands may be less resistant to periods of water scarcity than grasslands of high, alpine elevation. Alternatively, as longlived and clonal species inhabit plant communities of high, alpine elevation, they could be particularly slow in response to changing environments (Dullinger et al 2012;Gritsch, Dirnböck, and Dullinger 2016).…”

Scale sensitivity of the relationship between alpha and gamma diversity along an alpine elevation gradient in central Nepal

“…In the mountainous regions, the degree of climate driven changes can vary significantly even within a single mountain range (Gritsch et al 2016). This means that the nature, intensity, and frequency of climate change may be redistributed from one to the next spatial scale, and therefore, may not act uniformly across specific vegetation types and landscapes (Garcia et al 2014).…”