Secondary succession, biotic interactions and the functioning of roadside communities: plant-soil interactions matter more than plant-plant interactions

Abstract

Soliveres, S., García-Palacios, P. 2019. Secondary succession, biotic interactions and the functioning of roadside communities: plant-soil interactions matter more than plant-plant interactions. Ecosistemas 28(2): 50-60. Doi.: 10.7818/ECOS.1718

Long-term assessments of the recovery of degraded ecosystems are scarce, and even more those focusing on attributes beyond plant species composition. Here, we evaluate changes in planta-plant and plant-soil interactions across a 20+ years-chronosequence in motorway slopes. Furthermore, we quantify the associations between these biotic interactions and changes in important ecosystem attributes (soil fertility, nutrient cycling, erodibility and plant and microbe composition). Plant-plant interactions did not change significantly between slopes 0-2, 7-9 or >20 years old, but plant-soil interactions did. Plant-soil interactions were negative in young slopes and shift to positive from 7 years onwards. Four of the 15 variables analysed (plant cover, P content, C/N ratio and the composition of soil microbes) reached levels comparable to those of the reference ecosystem. Other variables (plant composition and richness, root biomass, organic matter cycling) increased substantially between the 0-2 years and the 7-9 years period, although did not reach the same level as in the reference ecosystem. Plant-soil interactions were as important as slope age to determine the similarity (regarding the reference) in soil microbe composition, erosion resistance and C cycling, while planta-plant interactions were of little importance for those attributes. Our work illustrates how fundamental attributes of the ecosystem change through time. We also show the importance of plant-soil interactions to determine the functioning of plant communities linked to motorway slope