Road Disturbance Shapes the Functional Composition of Native Plant Species but Not That of Non-Natives in the Arid Andes

Prepared by María Alisa Alvarez, Lohengrin A. Cavieres, Valeria Aschero, Lorena de Jesús Bonjour & Agustina Barros

An exciting and integral way to study plant communities is through looking at the functional traits of their species, i.e., morphological, physiological, and phenological characteristics. These traits play a relevant role in growth, reproduction, and survival, the three components of individual performance. In other words, it provides us with new insights for understanding how species are distributed and inferring ecosystem processes.

We applied this approach to the study of plant communities in the Cordon del Plata Provincial Park, in the arid Andes of Argentina. This protected mountain area is of great conservation value due to its species diversity, freshwater reserves, and scenic beauty.

We examined the functional responses of native and non-native plant communities along elevation gradients and in disturbed sites, at the edges of a vehicular road vs. remote sites. Non-native plants are those that are intentionally or accidentally introduced by humans outside their natural range.

We focused on roads because they are one of the main routes for the introduction of non-native plants and cause recurrent disturbance along the elevation gradient. We measured some plant traits, including leaf area, the percentage of dry matter content of the leaf, plant height, and specific leaf area, a measure that relates leaf size to dry weight. We then calculated the average of these traits, considering how abundant the different species were in the area.

We also examined whether the changes we observed on plant traits along the gradients were because of the differences between individuals of the same species or because there are different species in the community along the gradient.

We found that compared to native species, non-native species exhibited more acquisitive traits, associated with rapid growth, greater competitive capacity, and rapid assimilation of resources. Non-native species traits were only influenced by the elevation, showing lower height and dry matter content at increasing elevations. In contrast, native species traits were affected not only by elevation but also by disturbance. Near roads, they showed more acquisitive leaf traits, and with increasing elevation, there were variations in leaf size and plant height.

Our results also suggest that, although changes in traits at the community level were mainly due to different species present along the elevation gradient, non-native species showed a greater variability within the same species than native species.

Our results show that human disturbances, such as roads, altered the functional composition of native plant communities. In contrast, non-native species maintained similar traits whether they grew near the road or further away, indicating that they are less sensitive to disturbances. This highlights the need to reduce non-natives propagule pressure, as plants that establish themselves along roads may end up invading and affecting undisturbed mountain areas.

This is a plain language summary of the paper by María Alisa Alvarez and colleagues (2025), published in Applied Vegetation Science (https://doi.org/10.1111/avsc.70031)