Osmotic potential explains variation in whole plant economics stectrum model
Recent work in trait-based ecology has moved beyond the leaf economics spectrum (LES) framework toward a whole plant economic spectrum as a means to understand plant strategies and life history trade-offs. This framework places plants on a continuum from a “fast” to “slow” rate of return, based on their assembly of life history strategies. However, these models have had mixed success in explaining plant function in arid systems and have only recently accounted for water as a resource. Our study examined how leaf osmotic potential, a trait indicative of drought tolerance, helped explain plant trade-offs when combined with a traditional suite of LES traits.
We used four drought adapted shrub species (Encelia californica, Isocoma menziesii, Salvia apiana, and Atemisia californica) native to arid southern California, grown in a common garden in Orange County, CA. These species were chosen for the ubiquity across the landscape along with their differing drought avoidance / tolerance traits. We measured leaf osmotic potential at full turgor along with several LES traits (photosynthetic rate, specific leaf area, leaf nitrogen content), physiological and morphological traits (e.g., stomatal conductancea, specific root length) and measures of growth rate and reproductive fitness.
Preliminary results indicate osmotic potential mean values reflective of the plants drought avoidance/tolerance strategies with higher osmotic potentials found in drought tolerant plants (Artemisia californica: -3.71MPa, Isocoma menziesii: -2.51MPa) and lower osmotic potentials in plants with drought avoidance strategies (Encelia californica: -2.15MPa, Salvia apiana: -1.52MPa). These results demonstrate this trait may explain some of the variation in an LES or whole plant economics spectrum model.
LES along with the more recent integrated whole plant economics spectrum framework have been important tools for understanding trait variation in plant strategies and life history trade-offs. Osmotic potential has yet to be examined in an LES context and may help strengthen our understanding of some key plant trait relationships. Additionally, an expansion of our economics approach to trait-based ecology may have implications for understanding processes such as community assembly and ecosystem functioning.