SEARCH

SEARCH BY CITATION

FilenameFormatSizeDescription
pce12087-sup-0001-si.pdf215K

Figure S1. Different processes control foliar Δ15N and Δ13C. Temperature has a strong effect on Δ15N, whereas stomatal conductance has a strong effect on Δ13C. The Δ15N model described in this article was parameterized to describe a tropical forest canopy by specifying soil source 15N = 0, tree molar C:N stoichiometry of 200:1, and atmospheric [NH3] = 5 ppb. The Δ13C model of Farquhar et al. (1982) was parameterized using isotope effects for boundary layer conductance (ab = 2.9), stomatal conductance (a = 4.4), mesophyll conductance (am = 1:8), Rubisco (b = 29), photorespiration (f = 11.6), and dark respiration (e = −6).

Figure S2. Foliar Δ15N and Δ13C vary with canopy height in a tropical forest. After filtering the Ehleringer et al. (2010) dataset to exclude samples <1 m in height (i.e. predominantly C4 grasses), foliar Δ13C was significantly positively correlated with Δ15N (Δ15N = β * Δ13C + α: β = 0.71, α = −22.7, t = 666.8, d.f. = 685, P < 0.001).

Figure S3. Influence of assumptions about control of the NH+4(aq) pool on the overall isotope effect associated with leaf-atmosphere NH3 exchange. The contours illustrate the enrichment in 15N (‰) of glutamate when (a) the NH+4(aq) pool is fixed at 200 μM versus (b) allowed to vary linearly with flux through the photorespiratory NH3 cycle. In both cases, results are plotted for a leaf importing 100 nmol NH-3(aq) m−2 s−1 while photosynthesizing at 1500 μmol PAR m−2 s−1 and 394 ppm CO2(g).

Appendix S1. Parameterization.

Appendix S2. Equation set.

Please note: Wiley Blackwell is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.