A field study at the Niwot conifer forest
within
the footprint of an AmeriFlux tower site used fluorometry (chlorophyll
fluorescence) to identify a mechanism by which canopy uptake of
atmospheric/anthropogenic N deposition may influence photosynthesis
and net ecosystem
exchange (NEE). Correlation of daytime NEE with canopy N uptake (CNU)
had suggested a linkage. Strongly differing N additions were
spray
applied (simulating wet deposition) to spruce branches. Photochemical
efficiency was markedly enhanced in N-treated branches under high light
with a
concomitant reduction in foliar photodamage and/or in PAR-induced
foliar heat dissipation. Photosynthesis
and NEE enhancement were statistically related to CNU.
Author: H. Sievering, T. Tomaszewski, and R. Boyce (hsieveri at carbon dot cudenver dot edu)
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