Stoichiometry of mosses across an elevation and temperature gradient on Mauna Loa, Hawaii: Testing predictions from global theory

Background/Question/Methods Recently, general hypotheses have been framed relating nutrient stoichiometry to physiology for many organisms across resource gradients.  However, these theories have not been tested on mosses despite their wide ecological ranges and importance in ecological fluxes.  To test these theories, six moss species were sampled along an elevational gradient on Mauna Loa, Hawaii. N and P concentrations were expected to decline with increasing elevation and decreasing mean annual temperature (MAT), as shown previously for Metrosideros polymorpha, the dominant tree species across the gradient.  Alternatively, mosses were hypothesized to follow global trends for vascular plants across latitudes and elevational gradients, where N is independent of MAT, but P increases, and N:P decreases, with decreasing MAT. 

Results/Conclusions

We found for the mosses that N was independent of elevation and MAT, consistent with the global trend for vascular plants.  Further, consistent with these trends, P was positively correlated with elevation, and negatively correlated with MAT, while N:P showed the opposite trends.  These results confirmed the global trends for vascular plants, and contrasted with the distinctive trends found for M. polymorpha at these sites.  These results indicate the potential for convergent physiological responses driving stoichiometric trends among mosses and vascular plants, operating across local as well as global resource gradients.