Utilizing gradient simulations for quantifying community‐level resistance and resilience

Abstract

. 2017. Utilizing gradient simulations for quantifying community-level resistance and resilience. Ecosphere 8(9):e01953. 10. 1002/ecs2.1953 Abstract. Resilience is a complex, multidimensional property of ecosystems that describes how ecosystems respond to disturbance and likely results from the interactions of species and their environments across temporal and spatial scales. Due to the complexity in how ecosystems function and respond to disturbance, measuring resilience is a challenge. Gradient analysis provides a familiar, yet somewhat neglected framework for understanding and characterizing resilience. With simulations parameterized on existing biomonitoring data, we used distance-based measures in ordination space to characterize community-level resilience, here defined as a function of resistance and recovery. Our simulations and analyses involved five steps: (1) We generated regional species pools by simulating species distributions across environmental gradients; (2) we sampled from these regional species pools to emulate temporal changes in reference (i.e., minimally disturbed) and impacted communities responding to disturbance; (3) we performed ordinations on observations from both impacted and reference communities to summarize multivariate data; (4) we calculated distance-based measures for individual community trajectories in the ordinations to quantify their relative resistance and resilience; and (5) we compared these distance-based metrics between reference and impacted communities. We conclude with an empirical example demonstrating the lack of resistance of the Harp Lake (Ontario, Canada) zooplankton community to invasion relative to the changes observed among minimally disturbed reference communities. Overall, distance measures on ordinations provide a simple and effective visual framework to quantify the relative resistance and resilience of communities to disturbance, and our simulation approach provides a novel technique to develop and evaluate quantitative metrics related to ecosystem or community-level processes.

Linking the ball‐and‐cup analogy and ordination trajectories to describe ecosystem stability, resistance, and resilience

“…, Lamothe et al. ). Communities that travel relatively short distances in ordination space over time are considered stable (Fig.…”

“…Saltatory, directional patterns in ecosystem trajectories may occur due to the sudden appearance of species such as species invasions (Lamothe et al. ) or due to the loss of species from disturbances like drought (Bogan and Lyle ).…”

“…Each of the time-trend scenarios presented in Fig. 2 can be observed in an ordination plot (Lamothe et al 2017). In each panel, a dot or arrowhead represents the ecosystem state (here, community composition) at a given space and time (i.e., an observation).…”

“…, Lamothe et al. ), stability (Bloom , Hughes ), and regime shifts (Warwick et al. , Daufresne et al.…”

“…For example, ordinations of species community composition data enabled ecologists to illustrate how communities were changing over time (i.e., temporal trajectories of communities in ordination space), whether impacted by disturbance or not (Lake et al 2007, Smith 2012, Matthews et al 2013. Like the ball-and-cup analogy, ordinations are routinely used to illustrate ecological responses to disturbance (Boulton et al 1992) and provide a canvas for explaining concepts such as resistance and resilience (Seidl et al 2016, Lamothe et al 2017, stability (Bloom 1980, Hughes 1990, and regime shifts (Warwick et al 2002, Daufresne et al 2007.…”