Foliar retention of 15N tracers: implications for net canopy exchange in low- and high-elevation forest ecosystems
- ORNL
Nitrogen-15 ({sup 15}N) labelled ammonium and nitrate were applied to understory saplings in a low-elevation deciduous forest and a high-elevation coniferous forest during the 1993 growing season to estimate the minimum retention of inorganic N from wet deposition. Tissue samples were collected at both sites before and after the tracer applications to determine the initial and the final {sup 15}N content. The fraction of the tracer application retained by deciduous leaves or by current-year leaves and stems on conifers was calculated from measurements of {sup 15}N and total N content. At both study sites, tracer applications significantly increased the {sup 15}N content of sapling tissues, although there was no significant difference between the fractional retention of ammonium and nitrate. The results support earlier studies indicating that the foliar retention of {sup 15}N applied in simulated wet deposition is small. Our estimates of annual N uptake from wet deposition by the forest canopy at the low- and high-elevation study sites were only 14 and 7%, respectively. This study, along with prior studies of the different chemical forms of N deposition, indicates that canopy uptake of dry N deposition is a major contributor to the net canopy exchange of N in both forests.
- Research Organization:
- Oak Ridge National Laboratory (ORNL); Oak Ridge National Environmental Research Park
- DOE Contract Number:
- AC05-00OR22725
- OSTI ID:
- 989689
- Journal Information:
- Forest Ecology and Management, Journal Name: Forest Ecology and Management Journal Issue: 2-3 Vol. 103; ISSN 0378-1127
- Country of Publication:
- United States
- Language:
- English
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