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EFFECT OF SOIL N ON FINE ROOT PRODUCTION AND MORTALITY IN PSEUDOTSUGA MENZIESII
Citation:
Tingey, D T., M G. Johnson, D L. Phillips, AND P T. Rygiewicz. EFFECT OF SOIL N ON FINE ROOT PRODUCTION AND MORTALITY IN PSEUDOTSUGA MENZIESII. Presented at 4th North American Forest Ecology Workshop, Corvallis, OR, June 16-20, 2003.
Description:
The influence of soil N level on fine (diameter < 2 mm) root standing crop, production and mortality was assessed over a three-year period using minirhizotron tubes. Study sites were located in the central Oregon Cascade mountains in mature stands (> 100 years old) of Pseudotsuga menziesii growing on soils containing different N levels. The high N site (0.25 %N) was at 530 m where precipitation occurs primarily as rain, while the low N site (0.15 %N) was at 1200 m where snow remains on the ground for several months each year. Minirhizotron tubes (2 plots of 5 tubes each) were installed at each site during August 1994. To allow time for recovery from tube installation, the first root images were collected in June 1995 and then at a ~4 week intervals thereafter, except at the low N site when snow prevented sample collection. Root data from soil cores collected near the minirhizotron tubes were used to convert the minirhizotron data to the units of g m-2 (to a depth of 60 cm). There was no clear seasonal pattern in fine root standing crop, production, or mortality, at either site. This suggests that climate differences between sites did not have a significant influence. Over the study, fine root standing crop, production and mortality were consistently higher in the low N soil than in the high N soil. These findings are consistent with the concept that plants allocate more C to fine roots when soil N is low.