Disturbance and the (surprising?) role of ecosystem engineering in explaining spatial patterns of non‐native plant establishment. Issue 17 (13th August 2021) - Root‐Bernstein, Meredith
Abstract: Different conceptions of disturbance differ in the degree to which they appeal to mechanisms that are general and equivalent, or species‐, functional group‐, or interaction‐specific. Some concepts of disturbance, for example, predict that soil disturbances and herbivory have identical impacts on species richness via identical mechanisms (reduction in biomass and in competition). An alternative hypothesis is that the specific traits of disturbance agents (small mammals) and plants differentially affect the richness or abundance of different plant groups. We tested these hypotheses on a degu ( Octodon degus ) colony in central Chile. We ask whether native and non‐native forbs respond differently to degu bioturbation on runways versus herbivory on grazing lawns. We ask whether this can explain the increase in non‐native plants on degu colonies. We found that biopedturbation did not explain the locations of non‐native plants. We did not find direct evidence of grazing increasing non‐native herbs either, but a grazing effect appears to be mediated by grass, which is the dominant cover. Further, we provide supplementary evidence to support our interpretation that a key mechanism of non‐native spread is the formation of dry soil conditions on grazing lawns. Thus, ecosystem engineering (alteration of soil qualities) may be an outcome of disturbances, in which each interacts with specific plant traits, to create the observed pattern of non‐native spread in the colony. Based on these results, we propose to extend Jentsch and White (Ecology, 100, 2019, e02734) concept of combined pulse/ disturbance events to the long‐term process duality of ecosystem engineering/ disturbance. Abstract : Non‐native plant species accumulate on the centers of native degu ( Octodon degus ) colonies. We show that this is the result of the interaction and accumulation of two kinds of disturbances (biopedturbation and herbivory) with different effects on plant species over time. Although disturbance is usually represented as different from, or indeed opposite to, ecosystem engineering, we show that ecosystem engineering best explains the outcome of these two disturbances over time.