Joint effects of resource supply and resource types on properties of population dynamic models

The Lotka–Volterra competition model is the foundation of many ecological theories including competitive exclusion principle, limiting similarity and modern coexistence theory. However, competition between species is often modelled phenomenologically without explicitly considering the underlying mechanisms (e.g. resource competition with various resource supply forms and resource types). Deriving phenomenological models from the first principles and linking parameters in phenomenological models to the mechanisms of competition are critical to advance our understanding of population dynamics and community assembly.

Here, we used time‐scale separation to theoretically derive phenomenological competition models from mechanistic consumer‐resource models with different resource supply forms (logistic and chemostatic) and resource types (substitutable and essential). We then compared the performance of the resulting phenomenological models with simulation experiments and observational plant dynamic data during 50 years of succession. We further explored how the resource supply ratio such as nutrient imbalance induced by human activities affected the critical parameters, including species' intrinsic growth rate and interaction strength in phenomenological models and consequently the population dynamics.

We found that consumer population dynamics can be described by the Lotka–Volterra competition model when consumers are competing for substitutable or essential resources under logistic supply. In contrast, a novel reciprocal model was derived when consumers are competing for essential resources under chemostatic supply. Results from simulation experiments supported the model derivations. We also found that the reciprocal model outperformed the Lotka–Volterra model in explaining and predicting the population growth of 90 herbaceous plants during 50 years of succession. Moreover, the resource supply ratio affected species' intrinsic growth rates and competitive strengths differently under various resource supply forms and resource types and thus determined competitive outcomes.

Synthesis. Our study provides an alternative model (reciprocal model) when organisms compete for essential resources under chemostatic supply and sets up a basis for the selection of phenomenological competition models through the lens of ecological processes and contributes to a more accurate prediction of population dynamics, especially those driven by human‐induced nutrient imbalance.