Drenovsky, Rebecca E. , Richards, James .
Low soil nutrient availability increases nutrient resorption in perennial serpentine species.
NUTRIENT resorption, the withdrawal of nutrients prior to leaf senescence, is an important plant nutrient conservation mechanism. Consequently, it has been hypothesized that low nutrient soils should select for greater nutrient resorption in perennial species endemic to these conditions. However, there is mixed support for this hypothesis. We propose that factors, such as phylogeny, phenotypic plasticity, and environment (e.g., water availability) may obscure the relationship between nutrient availability and leaf nutrient resorption. To address this hypothesis, we collected senescent leaf tissue from congeners (Arctostaphylos manzanita, A. viscida, Ceanothus cuneatus, C. jepsonii, Quercus berberidifolia, Q. durata) found in similar geographic locations (northern California Coast Range), but dissimilar edaphic conditions (on and off serpentine soils) over a two year period. We predicted that within congener pairs, nitrogen and phosphorus concentrations would be reduced to lower levels in serpentine than non-serpentine species, reflecting greater resorption. As a result, carbon-to-nitrogen and carbon-to-phosphorus ratios would be higher in senescent leaves of serpentine species, resulting in litter more resistant to decomposition. Overall, N and P concentrations in senescent leaf tissue were 1.2 and 2-fold lower in serpentine species compared to non-serpentine species (P=0.03 and P=0.003, respectively), despite differences among genera and years for N. Lower P concentrations did translate into a 2.5-fold increase in C-to-P ratios in serpentine species relative to non-serpentine species (P=0.004), but there were no significant differences in C-to-N ratios (P>0.05). Together, these data suggest that low nutrient serpentine soils have been a consistent selective force for greater nutrient resorption in species endemic to these soils. Additionally, shedding of low nutrient litter by the serpentine species likely slows nutrient cycling, exacerbating the already low nutrient conditions.
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1 - John Carroll University, Biology Department, 20700 North Park Blvd, University Heights, Ohio, 44118, USA
2 - University of California Davis, Lawr, One Shields Avenue, Davis, California, 95616-8627, USA
Presentation Type: Poster:Posters for Sections
Location: Auditorium/Bell Memorial Union
Date: Tuesday, August 1st, 2006
Time: 12:30 PM