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

Aims

Species assemblages in mountains are affected by variation in environmental conditions linked to elevation and anthropogenic disturbance. How species respond to these factors may vary based on the species origin. We examined the functional response of non-native and native assemblages and the relative contribution of intraspecific variation to road disturbance and elevation.

Location

Cordón del Plata Provincial Park, Andes, Argentina.

Methods

We used the functional ecology approach. We calculated community-weighted means (CWM) and functional divergence of leaf area, SLA, LDMC, and plant height of natives and non-natives in transects along elevation, at roadsides and 52 m away from the road. We used linear models to assess changes with elevation and disturbance and estimated the contribution of intraspecific variability using variance partitioning.

Results

Non-natives showed more acquisitive traits than natives. Non-natives responded only to elevation by lower stature and LDMC and higher SLA. For native species, road proximity was related to more acquisitive foliar traits, while community leaf area, SLA, and plant height varied with elevation. Species turnover explained most of the variability observed in the CWMs in both species' origin. The contribution of intraspecific variability was greater in non-native species.

Conclusions

Human disturbance affects the functional composition of native species. In contrast, the community traits of non-natives did not differ between road edges and the interior plots, suggesting that they are not affected by disturbance. Therefore, it is critical to reduce propagule pressure because of the potential of roadside species to invade undisturbed sites.