Grasslands change differently at different elevations

Prepared by Gianmaria Bonari, Alessandro Bricca, Davide Andreatta, and Francesco Maria Sabatini

This Behind the paper post refers to the article Grassland Changes in the Eastern Alps Over Four Decades: Unveiling Patterns Along an Elevation Gradient by Gianmaria Bonari and colleagues, published in Applied Vegetation Science (https://doi.org/10.1111/avsc.70012)

Over the past forty years, the grasslands of a major Alpine valley have undergone significant transformations, with changes that vary significantly depending on elevation. A detailed resurvey study conducted in the Valsugana Valley, in the Italian Eastern Alps, analyzed these changes by comparing 115 grassland vegetation plots along an elevation gradient of 2000 m sampled between 1986-1988 and resurveyed in 2022.

The results reveal that many types of grasslands have been replaced by other grassland types, with a particular decrease in dry grasslands in favor of mesic ones, and by wooded or anthropogenic areas. Although the overall plant species richness has not changed much over time — except for high elevation that experienced an increase of number of species — the composition of plant communities changed with respect to original plant communities.

Plant species that prefer dry and sunny conditions have decreased, while those that prefer nutrient-rich soils have increased. There has also been an increase in “neophyte” species, that is, alien plants non-native to the region, particularly evident at low elevations. Plant life forms have also undergone substantial changes: plants storing their reserves in bulbs and rhizomes (geophytes) and annual species (therophytes) have increased at both low and high elevations, while herbaceous plants whose overwintering buds are located at ground level (hemicryptophytes) have decreased at low and medium elevations. In addition, woody plants, such as shrubs and trees, have increased their presence, especially at medium elevations.

We also found a substantial turnover in recorded species, which differed across elevation belts. We classified species as winning, losing, or stable, based on whether their occurrences increased, decreased, or remained unchanged over time. At high elevations, there was a greater contribution of “winning” and “stable” species, with a lower presence of “losing” species compared to other elevations.

These changes are likely the result of several factors: at low elevations, urban and agricultural areas, especially vineyards, orchards, and cropland, have replaced many grasslands. At intermediate middle and high elevation, we observed a twofold trend, with some pastureland being abandoned and others whose use has become more intense. These transformations in land use have caused a replacement of the original species with others more suited to these new conditions. In summary, the grasslands of Valsugana (Eastern Alps, Italy) have undergone profound transformations over the last four decades, as exemplified for different elevations in the animated figure below. Our study shows how socio-ecological changes influence vegetation differently depending on elevation. For this reason, it is essential to take these dynamics into account when planning conservation strategies. Conservation management strategies must be adapted to address the specific transformations of biodiversity that occur at different elevations in the Alps.