What does the leaf economic spectrum tell us about the performance of individuals, populations, communities, and ecosystems?

Background/Question/Methods

Leaf traits result from evolutionary and physiological processes, within a complex (a)biotic milieu, and reflect variation in ecological strategies. They provide a lens through which those ecological strategies, and their consequences, can be compared among taxa that co-occur locally, as well as across climate zones and vegetation types worldwide.

Results/Conclusions .

So, what does the leaf economic spectrum (LES) tell us?

Traits matter.  The LES is the name given to the pattern and distribution of leaf traits (morphological, biochemical, metabolic, longevity) in multi-dimensional trait space and represents our interpretation of its causes.  Not all trait combinations exist in nature, because they are selected against, are biophysically impossible, or both.  What does exist is a multiple-trait envelope that demonstrates that all taxa have leaf traits that reside somewhere along a continuum from a ‘slow’ to a ‘fast’ return on investment design strategy. The causes of the diversity of successful strategies must reside in the trade-offs that equalize fitness at multiple positions along the LES. The LES position influences whole-plant function, biotic interactions, and plant-environment interactions, and hence, the assembly, dynamics, structure, and function of communities and ecosystems. The universal LES rules about leaf design also influence scaling of physiology from seedling to adult, cell to ecosystem, and stand to the globe. The LES thus links leaf to plant and ecosystem-scale gas fluxes, to decomposition and soil mineral element cycling, and to feedbacks between ecosystems and the coupled carbon cycle - climate system.

The generality embedded in the LES has led to its use in research on diverse themes, including ecotypic adaptation, community assembly, metabolic theory of ecology, paleoecology, disturbance ecology, invasion ecology, biogeography, biogeochemistry, and global change biology. Neither my abstract nor presentation have room to do more than provide an overview of such examples and show the connections and interactions among and across these ecological strands. Of course the LES is only part of the plant trait story: stem, root, reproductive, architectural (e.g., plumbing, leaf display), and biotic defense traits, often weakly coordinated with the LES, influence many aspects of plant, community and ecosystem processes.  In fact, it is a wonder that a single attribute, such as the position on the LES, can tell us much at all. Therefore, we should remember that failure to explain everything with the LES is not the same as failure to explain some very important things.