PARENT SESSION
Contributed Oral Session 12: Arid Lands: Plant Response to Precipitation
Monday, August 8, 8:00 AM - 11:25 AM, Meeting Room 520 B, Level 5, Palais des congrès de Montréal
Do desert plants partition water by soil depth or time?
Schwinning, Susanne*,1, Chesson, Peter2, 1 Texas State University, San Marcos, TX2 University of Arizona, Tucson, AZ
ABSTRACT- H. Walter and others hypothesized that plants in water-limited environments can coexist through the spatial partitioning of soil water, if there are sufficient differences in the rooting depths of species. Mounting evidence suggests that this mechanism of resource partitioning may not be effective in arid regions where precipitation rarely recharges deeper soil layers. An alternative to water partitioning in space is partitioning in time, facilitated through differences in the timing of water uptake and utilization. We conducted a modeling study, using a mechanistic plant-soil-atmosphere simulation model, to explore the impact of spatial resource partitioning mechanisms (facilitated by differences in root distribution) and of temporal mechanisms (facilitated by differences in phenology) on the competitive interactions of plant species in arid settings. Our results suggest that the effect of water partitioning by soil depth can be underestimated if it is assumed that competitors have identical phenological schedules. Likewise, differences in root distributions can enhance the temporal partitioning of soil water among competitors. Thus, even in a simple model that considers only one limiting resource (water), no single coexistence mechanism can be said to dominate.
Key words: coexistence mnechanisms, niche separation, water relations