Species’ abundance patterns interpreted in the light of Liebig’s Law of the Minimum

Background/Question/Methods

: Describing the environmental determinants of species distribution patterns is a central theme in ecology. Species’ abundances vary significantly across their range, reflecting populations' response to a range of limiting conditions. We propose a new approach to the study of these limiting relationships based on Liebig's Law of the Minimum (1840), which predicts that species’ abundance at a specific point in time and space does not depend on multiple environmental factors but on the most limiting factor. We analyzed abundance-climate relationships in 187 tree and 114 bird species in continental US, and found that patterns compatible with the Law of the Minimum are widespread among species. Moreover, we fitted quantile regressions to estimate the limiting influence of water availability and growing degree days (GGD) on the maximum potential abundance of these species.

Results/Conclusions

: About 59% of tree species and 52% of bird species had their maximum abundance significantly affected by at least one of the environmental predictors. There was an overall linear negative effect of GDD and water availability in tree maximum abundance. For birds, the most influential predictor was GDD, with great inter-specific variation in the direction of abundance-environmental relationships. Our results highlight the interest of Liebig’s Law of the Minimum in ecology and biogeography, and open new perspectives to study limiting relationships in the context of global climate change.