Functional traits can be used to understand and predict a number of ecological processes including plant response to environmental change. While drought tolerance is fairly well understood in woody species, less is known about how traits correlate with drought tolerance in herbaceous species. We examined above- and belowground traits and drought survival time in 23 herbaceous species occurring in a southern California coastal sage scrub community, including grasses and forbs from annual and perennial life history groups. Plants were grown in full sun and watered daily to saturation for six weeks. During the sixth week, we stopped watering the plants to simulate a drought scenario. We monitored plants for eight weeks during the drydown to determine plant mortality.
Results/Conclusions
We measured traits pertaining to leaf physiology, root morphology, and plant-level biomass allocation including photosynthetic rate, water-use efficiency, leaf nitrogen concentration, leaf mass per area, specific root length, root length density, root diameter, root tissue density, root mass fraction, and leaf mass fraction. Species with high leaf mass fraction and root length density had high mortality rates, suggesting that rapid growth in young seedlings is a liability in drought years. Plants with high leaf mass likely lose more water via transpiration and quickly deplete soil water. Our dataset included five invasive species, which collectively had higher values of leaf mass fraction and root length density relative to native species. Thus, projections for reduced rainfall in southern California ecosystems may have deleterious impacts on invasive species populations.