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

Functional ecology of long-lived creosotebush clones in the Mojave Desert.

Hamerlynck, Erik^*,1, McAuliffe, Joseph², Eppes, Martha³, ¹ Rutgers University, Newark, NJ, USA² Desert Botanical Garden, Phoenix, AZ, USA³ University of North Carolina, Charlotte, VA, USA

ABSTRACT- Large creosotebush (Larrea tridentata) clones in the Mojave Desert are some of the longest-lived vascular plants in the world. The remarkable persistence of these clones depends on the development of a coppice of fine windblown soil material imported from highly localized sources, and serves as an additional source of limiting soil water and nutrient resources. However, coppiced creosotebush clones are found across a range of distinct depositional surfaces with soil characteristics that may alter the effectiveness of coppice development on plant performance. To address this, we measured the co-variation of basal area and coppice height with predawn water potential (_pd), carbon isotope discrimination (), specific leaf mass (g m²), and leaf N-content in juvenile and adult plants possessing intact and degrading coppices, across surfaces varying in age, depositional history, and soil horizon development under extremely dry and wet conditions. _pd was positively correlated with coppice height, both under dry and wet conditions, but with no significant differences between plant types or sites in the measured parameters under dry conditions. Under wet conditions, coppiced adults had significantly higher _pd and compared to juveniles and degraded coppice plants, suggesting well-developed coppices facilitate favorable water status and prolonged photosynthetic activity. However, coppiced plants unexpectedly showed pronounced site-specific _pd, but little variation in between sites. In contrast, juveniles and degraded coppice plants had more limited response in _pd but greater variation in . These findings suggest that while coppices do provide a buffer from extreme variations in soil water, it may be that relatively static stomatal dynamics and the extensive rooting volumes of large adult clones may allow the surrounding soil environment to have a marked affect on seasonal plant performance.

Key words: creostoebush, clone, geomophology, photosynthesis