PS 81-216
Leaf trait shifts with elevation in California alpine plants: A consequence of smaller plant size?
The physiological and ecological mechanisms underlying plant distribution along environmental gradients and the adaptations and degree of plasticity that affect species range limits remain poorly understood. No other terrestrial area has steeper environmental gradients than the alpine zone. In general, plant sizes decline with increasing altitude. We sought to determine to what degree shifts in plant traits along an elevational gradient are associated with or independent of this decline in plant size with altitude. We sampled 41 alpine dicot species at 10 sites from 3100 to 4100 m in the California Sierra Nevada and White Mountain ranges, and for five species, we sampled plants at 4-6 elevations. We measured plant height, diameter and functional traits such as leaf mass per area (LMA), leaf vein length per leaf area (VLA), leaf dry matter content (LDMC), leaf thickness (LT), leaf mass density (LD), and leaf shrinkage between full hydration and desiccation. We tested correlations of traits with elevation species that were found at four or more different elevations, and analyzed trait shifts within each species to determine the degree of correlation with changes in elevation and plant size, and the degree that these correlations were independent using partial correlation analyses.
Results/Conclusions
We found across all 41 species that plant size (height and basal diameter) strongly declined with increasing elevation. Within the five species sampled across elevations we similarly found trends for declining size with increasing elevation, and, for specific species, increases leaf thickness with elevation, increases in density, increases in LMA, and declining values for leaf shrinkage during dehydration. In the majority of cases, partial correlation analyses indicated that the relationship of leaf traits to elevation was independent of plant size. These findings indicate that plasticity in plant size and leaf traits with elevation are independent. Thus, variation in leaf traits with elevation is not simply a consequence of smaller plant size. These findings point to an importance for leaf trait shifts in plant performance across elevational ranges, and suggest that models for plant performance and distributions need to be developed that incorporate differences in plant size and leaf traits across species, and plasticity within species.