Abstract Detail

Ecophysiology

Angelo , Courtney Lynn [1], Pau, Stephanie [1].

The photosynthetic pathway effect on foliar δ¹⁵N along a climatic gradient in Hawaii.

The negative relationship between water availability and foliar δ¹⁵N has been shown in Hawaii, with δ¹⁵N acting as an indicator of the ‘openness’ of the N-cycle. Until recently, there has been little evidence of a photosynthetic effect (C₃ vs. C₄) on foliar δ¹⁵N. A known difference in nitrogen metabolism in C₃ and C₄ plants suggests that there may be a photosynthetic effect on foliar δ¹⁵N. In this study, we collected tissue samples of dominant grass species from field plots at 100 - 150 m elevation intervals along a climatic gradient in Hawai‘i Volcanoes National Park. We examined the relationship of C₃ and C₄ grasses, foliar δ¹⁵N, and water availability. Foliar percent nitrogen of C₃ and C₄ plants was found not to differ, however, C₄ grasses had lower mean nitrogen values than C₃ grasses. Using a t-test, we found that C₃ grasses had higher δ¹⁵N values than C₄ grasses (P = 0.006; C₃ mean = -1.253, C₄ mean = -3.530). C₃ grasses coexisting with C₄ grasses had mean δ¹⁵N values 70% higher than C₄ grasses within the same site. Using regression analyses, foliar δ¹⁵N (C₃ and C₄ grasses) was found to have a significant negative relationship with increasing precipitation (P = 0.018, r² = 0.221). There was also evidence that the relationship between foliar δ¹⁵N and water availability was influenced by photosynthetic pathway (C₃ and C₄) (P = 0.010, r² = 0.325). These results have important implications for how grassland ecosystem nitrogen dynamics may change with shifting patterns of C₃-C₄ grasses.

1 - Florida State University, Geography Department
2 - Florida State University, Geography Department

Keywords:
C3 and C4 grasses
climatic gradient
foliar N.

Presentation Type: Oral Paper:Papers for Topics
Session: 15
Location: Firs South/Boise Centre
Date: Tuesday, July 29th, 2014
Time: 9:30 AM
Number: 15007
Abstract ID:713
Candidate for Awards:None