PARENT SESSION
Poster Session #4: Invasions.
Monday, August 6, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall
110
Variation in soil nitrogen availability affects leaf characteristics and photosynthesis of Japanese barberry (Berberis thunbergii) .
Harrington, Robin1, Cassidy, Tim1, Fownes, James1, 1
ABSTRACT- We investigated the physiological response of Japanese barberry to soil N to determine the reasons for its success in invading intact New England forests. We hypothesized that variation in barberry growth among differing sites was explained by photosynthetic responsiveness to N rather than variation in light or soil pH. A field experiment using 4 replicate plots per treatment at two sites altered N availability through N (10 g urea m-2 y-1) or C addition (200 g sugar m-2 month-1 plus 650 g sawdust m-2 y-1). Ten months after treatments began, foliar N ranged from 0.94% (C addition) to 2.74% (N addition). Light-saturated photosynthesis increased and leaf mass per unit area decreased with foliar N concentration. Surprisingly, photosynthesis increased relatively more than foliar N concentration, resulting in increased photosynthetic N-use efficiency. Foliar C13 content was not significantly correlated with foliar N, but it increased (became less negative) with leaf mass per area, suggesting higher intrinsic water-use efficiency in low N plants. Barberry apparently succeeds in invasion of forest understories through a high degree of responsiveness to increased N, suggesting that more fertile sites are more invasible and that management that increases available N increases the likely success of barberry.
KEY WORDS: Berberis thunbergii, invasions, N availability, photosynthesis