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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.


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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


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