Soil nitrogen (N) is a major factor limiting forest growth. While inorganic N forms such as ammonium (NH4) and nitrate (N03-) have been the focus of plant N nutrition studies, a growing body of research has shown direct uptake of organic N forms (including amino acids) is common across the plant kingdom. However, there are few examinations of the contribution amino acid N makes to plant nutrition in temperate forest regions. The main goals of this thesis were to determine i) potential contributions amino acid-N and inorganic-N could make to N-nutrition of some temperate forest plants, ii) N-form adaptations among species that could lead to N-niche partitioning among them, and iii) the influence of m ycorrhizae on plant growth and N-form uptake. I determined the relative availabilities of amino acid N and inorganic N in three sites near Jordan River, British Columbia, biomass production of four species of forest plants. some associated with m ycorrhizae, when given inorganic (NH4-, N03-) or organic (glycine, glutamic acid) N, and short-term uptake (24 hours) of labelled N H4+, N03-, glycine, and glutamic acid using Sitka spruce (Picea sitchensis ), Douglas-fir (Pseudotsuga menziesii ), blueberry (Vaccinium ovalifolium) and salmonberry (Rubus spectabilis). All species performed well when supplied with N prim arily as NH4+, and NH4+ tended to be the most available N -source in all soils tested. Soils dominated b y salmonberry tended to have greater N03- production and lower amino acid-N: inorganic-N ratios compared to soils dominated by blueberry. This corresponded to the good growth and short-term 15NO3-uptake of salmonberry when grown with N supplied primarily as N03-, compared to other N-form treatments. Blueberry grew significantly more when given NH4- and N03-compared to amino acids. Thus, while blueberry has the ability to take up and use N03-for growth, sites on which it was dominant had low N03- availability. Mycorrhization did not improve biomass production, and in some cases actually decreased biomass. However, 15N uptake tended to be improved in mycorrhizal plants compared to non¬mycorrhizal plants. The comparable rates of short-term 15N uptake from amino acids and inorganic-N by all plants. in addition to the coin parable amino acid-N and inorganic-N availability in soils, suggested that am ino acids may be significant contributors to the N - nutrition of these tern perate species. However, biomass production was often reduced in amino acid treatments, which this was not always reflected by short-term '5N uptake.
| Identifer | oai:union.ndltd.org:uvic.ca/oai:dspace.library.uvic.ca:1828/2510 |
| Date | 07 April 2010 |
| Creators | Metcalfe, Rebecca Joy |
| Contributors | Hawkins, Barbara J. |
| Source Sets | University of Victoria |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Rights | Available to the World Wide Web |
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