Organic and inorganic nitrogen nutrition of western red cedar, western hemlock and salal in mineral N-limited cedar-hemlock forests.
Western red cedar (Thuja plicata Donn.), western hemlock (Tsuga heterophylla Raf. Sarge) and salal (Gaultheria shallon Pursh) are the main species growing in cedar-hemlock forests on Vancouver Island, Canada. Based on the dominance of organic N in these systems, we tested the hypotheses that: (1) organic N can be utilized by the three plant species; and (2) salal, which is ericoid mycorrhizal and has high tannin concentration in its tissues, would absorb more N from the complex organic N compounds than the other two species. The abilities of cedar, hemlock and salal to take up 15N,13C-labelled glutamic acid were measured and the capacities of the three species to use nitrate (NO3-), ammonium (NH4+), glutamic acid, protein and protein-tannin N were compared over a 20-day period. Based on 13C enrichment, all three species absorbed at least a portion of glutamic acid intact. Cedar, hemlock and salal also showed similar patterns of N uptake from the NO3-, NH4+, glutamic acid, protein and protein-tannin treatments. The largest proportions of applied N were taken up from the NO3- and NH4+ treatments while smaller amounts of N were absorbed from the organic N compounds. Thus organic N was accessed to a modest degree by all three species, and salal did not have a greater capacity to utilize protein and protein-tannin-N.
Bennett
Jennifer N
JN
Forestry Department, North Carolina State University, 3106 Jordan Hall, Raleigh, NC 27601-8008, USA. jbennett@ncsfnc.cfr.ncsu.edu
Prescott
Cindy E
CE
D002247:Carbon Isotopes / Q000032:analysis; D031282:Gaultheria / Q000502:physiology*; D009584:Nitrogen / Q000378:metabolism*; D009587:Nitrogen Isotopes / Q000032:analysis; D011506:Proteins / Q000378:metabolism; D029783:Thuja / Q000502:physiology*; D014197:Trees; D028225:Tsuga / Q000502:physiology*
D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D011506:Proteins; D009584:Nitrogen