PARENT SESSION
Oral Session #63: Plant Ecology: Water Relations. Presiding: J. Cleverly.
Thursday, August 9, 2001. 8:00 AM to 12:00 PM. Hall of Ideas H.
Comparative phenology and water relations of yellow bush lupine (Lupinus arboreus) in coastal north-central California.
Reich, Alexandra1, Sharifi, Rasoul2, Connors, Carolyn3, Bentley, Barbara 4, Rundel, Philiop2, 1 2 3 4
ABSTRACT- We examined climatological data, plant and soil water relations, and plant phenology in two subpopulations of Lupinus arboreus (Fabaceae) at the Bodega Marine Reserve (Sonoma County, California). With a coastal mediterranean-type climate, weekly air temperatures were cool (7-15°C/12-19°C, minimum/maximum) throughout the year, and relative humidity was 85%-100%. Mid-summer soils at both sites were nearly water-saturated at 50 cm depth. Midday shoot water potentials were moderate at both sites (-0.8 MPa to -1.4 MPa) throughout the year. On foggy days, plants in both sites exhibited slightly greater midday water stress (-1.02 MPa to -1.07 MPa) than on sunny days (-0.93 MPa to -0.97 MPa). Growth initiation times, magnitudes of shoot diameter increments and shoot elongation rates differed between sites. Both subpopulations exhibited maximal shoot elongation in the spring (April), which decreased after the onset of flower production. Leaf area also differed between the two sites (8.1 cm2 vs. 6.4 cm2), while specific leaf weight varied seasonally. We conclude, from the different patterns of growth in the two subpopulations, that the phenology of L. arboreus is decoupled from climatic conditions and soil moisture content. To date, much of the work on L. arboreus has implicated insect herbivory as the cause of lupine stand die-offs. We suggest timing of growth initiation and reproduction plays a role in enabling some subpopulations to persist better than others.
KEY WORDS: dune, habitat, Lupinus