Effects of Elevated CO2and Nitrogen on Ponderosa Pine Fine Roots and Associated Fungal Components

The effects of CO2and nitrogen treatments on ponderosa pine (Pinus ponderosa Dougl. ex P. Laws. & C. Laws.) fine roots and associated fungal structures were monitored for a year (October 1992 to October 1993) using a minirhizotron camera system. The trees were grown in native soil in open-top fi...

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Bibliographic Details
Published in:Journal of biogeography 1995-03, Vol.22 (2/3), p.281-287
Main Authors: Tingey, David T., Johnson, Mark G., Phillips, Donald L., Storm, Marjorie J.
Format: Article
Language:English
Subjects:
Carbon dioxide
Density
Elevated CO2 Interactions
Forest soils
Hyphae
Mycorrhizae
Nitrogen
Plant roots
Plants
Soil air
Soil water
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Summary:The effects of CO2and nitrogen treatments on ponderosa pine (Pinus ponderosa Dougl. ex P. Laws. & C. Laws.) fine roots and associated fungal structures were monitored for a year (October 1992 to October 1993) using a minirhizotron camera system. The trees were grown in native soil in open-top field-exposure chambers at Placerville, CA and exposed to ambient$(\thicksim 350 \mu mol mol^-1)$air or ambient air plus either 175 or 350 μ mol mol-1 CO2and three levels of nitrogen addition (0, 100 and 200 kg ha-1); however, the 100kg ha-1 N treatment at ambient plus 175 μ mol mol-1 CO2treatment was omitted from the experimental design. Roots were classified as new, white, brown, decaying or missing and their lengths and diameters measured. The occurrence of mycorrhizae and fungal hyphae was also recorded. The majority (>90%) of roots observed were smaller than 2 mm and the mean diameter decreased during the study. None of the root parameters measured showed a significant response to elevated CO2The elevated CO2treatments consistently showed an increase in root area density averaging 50% larger compared to ambient CO2, but this response was not statistically significant due to the high spatial variability of root distribution. Only new root area density showed a significant nitrogen response. The most new roots were initiated between April and June and the highest level of root loss occurred between June and August. The occurrence of mycorrhizae and fungal hyphae increased in response to CO2treatment but not the nitrogen. Their highest levels of occurrence were during August and October 93.
ISSN:0305-0270
1365-2699