At what spatial scales are alternative stable states relevant in highly interconnected ecosystems?

Abstract

Citation: Karatayev, V. A., and M. L. Baskett. 2020. At what spatial scales are alternative stable states relevant in highly interconnected ecosystems? Ecology 101(2):Abstract. Whether ecosystems recover from disturbance depends on the presence of alternative stable states, which are theoretically possible in simple models of many systems. However, definitive empirical evidence for this phenomenon remains limited to demographically closed ecosystems such as lakes. In more interconnected systems such as temperate rocky reefs, the local relevance of alternative stable states might erode as immigration overwhelms local feedbacks and produces a single stable state. At larger spatial scales, dispersal might counter localized disturbance and feedbacks to synchronize states throughout a region. Here, we quantify how interconnectedness affects the relevance of alternative stable states using dynamical models of California rocky reef communities that incorporate observed environmental stochasticity and feedback loops in kelp-urchin-predator interactions. Our models demonstrate the potential for localized alternative states despite high interconnectedness likely due to feedbacks affecting dispersers as they settle into local communities. Regionally, such feedbacks affecting settlement can produce a mosaic of alternative stable states that span local (10-20 km) scales despite the synchronizing effect of long-distance dispersal. The specific spatial scale and duration of each state predominantly depend on the scales of environmental variation and on local dynamics (here, fishing). Model predictions reflect observed scales of community states in California rocky reefs and suggest how alternative states co-occur in the wide array of marine and terrestrial systems with settlement feedbacks.

Grazer behavior can regulate large-scale patterning of community states

“…Similarly, on Macrocystis-dominated reefs of central Chile, urchins rely primarily on passive grazing (Vásquez et al 1984) but in other areas can form barrens. A second reef-scale feedback that can contribute to reef-scale forests and barrens arises when kelp facilitate recruitment of urchin predators (Karatayev & Baskett 2020), which freely forage across entire reefs (Topping et al 2005). Our results highlight that behavior might strengthen this feedback by detecting declines in grazing activity with predator density in both regions, complementing analogous findings in California (Ebeling et al 1985;Caselle et al 2018).…”

Transient dynamics during kelp forest recovery from fishing across multiple trophic levels

“…In addition, stochastic recruitment pulses may be particularly important in the case of recovery dynamics by determining the likelihood of return to the unexploited equilibrium (Nickols et al 2019). Sea urchins and spiny lobsters can exhibit episodic recruitment (Pringle 1986, Shears et al 2012, which can cascade to kelp abundance and determine the community state under feedbacks that lead to alternative stable states (Karatayev and Baskett 2019). Second, we describe only a sub-module of the diverse kelp forest food web, and the alternative predators and prey not included could strongly influence recovery trajectories.…”

Stress gradients interact with disturbance to reveal alternative states in salt marsh: Multivariate resilience at the landscape scale

“…Mapping resilience along stress gradients will additionally allow the quantification of both imperiled and resilient patches of habitat at several spatial scales, giving managers and restoration practitioners spatially explicit guidance on ecosystem management options before state changes occur. Beyond management implications, resilience may exhibit spatial clustering or patterns at specific scales (Karatayev & Baskett, 2020) that can provide greater mechanistic insight, but may not be obvious from patch-level analyses or experimental plots (Coop et al, 2019;Falk et al, 2019).…”