Thornley, R. | Search bioRxiv

bioRxiv2025

Current estimates of population resilience do not predict resilience to directional environmental shifts

Natural systems worldwide are exposed to gradual changes imposed by directional environmental shifts, known as ramp disturbances. However, contemporary assessments of population resilience focus on the resistance and recovery of systems following one-off (i.e., pulse) disturbances. Thus, our current perception of demographic resilience overlooks the potential impacts of the cumulative effects of ramp disturbances on population dynamics. Simulating 50-year ramp disturbance scenarios upon the survival and fecundity dynamics of 511 populations across 344 species, we illustrate non-linear patterns in how directional environmental shifts will reshape the resilience of natural populations. Accordingly, existing estimates of population resilience are not robust against a backdrop of ongoing and continuous environmental change. Instead, we demonstrate the need to quantify how the relative partitioning of energetic resources across survival vs. fecundity informs population resilience. Our findings challenge the use of well-established approaches in forecasting population resilience to ongoing global change.

ecology↗

bioRxiv2024

Variation in precipitation drives differences in interactions and short-term transient instability between grassland functional groups: a stage-structured community approach

Climate change is expected to increase the frequency and severity of precipitation extremes, causing droughts and flooding. Consequently, grassland communities are forecasted to become increasingly unstable. To predict grassland responses, we need empirical information together with models that reliably extrapolate community dynamics from those observations. However, such prediction is challenging because community models typically simulate long-term (asymptotic) performance, and thus potentially neglect their short-term (transient) performance. Here, we use data from a precipitation experiment performed over eight years to model both short- and long-term responses of three functional groups - grasses, legumes, and non-leguminous forbs - to precipitation extremes. We use multi-functional-group Integral Projection Models and pseudospectral theory, to track grassland community dynamics. We show that the percentage-cover-stage-structure of functional groups shapes their transient instability, and that inter-functional-group interactions are competitive under increased precipitation but facilitative under decreased precipitation. IPMs and pseudospectra enable forecasting of how functional-group-stage-structure drives responses to climatic extremes.

ecology↗