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Publication Title: Production and turnover of fine roots of mature Douglas-fir in relation to site
Year: 1982 Publication Type: Thesis
H. J. Andrews Publication Number: 1983
Citation: Santantonio, Daniel. 1982. Production and turnover of fine roots of mature Douglas-fir in relation to site. Corvallis, OR: Oregon State University. 93 p. Ph.D. dissertation.
Online PDF: http://andrewsforest.oregonstate.edu/pubs/pdf/pub1983.pdf
Abstract: Fine roots are a dynamic component of Douglas-fir ecosystems.Changes in standing crops indicate that fine roots require a majorportion of the stand's energy resources to fulfill their role in thefunctioning of these systems. We observed standing crops of live anddead fine (< 1 mm diameter) and small (1-5 mm diameter) roots over a30-month period based on intact soil core samples taken monthly fromgrids established in dry, moderate, and wet stands of mature Douglas-fir. Environmental measurements included temperature of soil and air,water potential of soil and xylem at predawn, and potential evapora-tion. Changes in standing crops of live and dead fine roots in thetop 75 cm of soil indicate that seasonal patterns vary from one yearto next and can vary by site, but may not. Differences from one yearto the next may be greater than differences between sites. Largechanges in standing crop can occur within a few months. Fine rootsare most abundant in the uppermost layer of soil; 75% are in the top25 an of soil. Changes within various layers by depth are statisti-cally significant during seasonal and "long-term" time frames and aremost pronounced in upper layers. Counts of "new" root-tips taken fromthese samples permit an assessment of root activity independent of necessarily correspond to changes in standing crop, indicating thatfine—root growth and mortality can occur simultaneously in the samearea. Based on a simple conceptual model of fine—root dynamics weestimated fine—root production and turnover by inferring transfersneeded to account for observed standing crops of live and dead fineroots. When averaged over the entire study period, we estimate fine—root growth as 6.5, 6.3, and 4.8 Mg/ha/yr, fine—root mortality as 7.2,7.2, and 5.5 Mg/ha/yr, and decomposition of fine roots as 8.2, 8.0,and 6.9 Mg/ha/yr for the dry, moderate, and wet sites, respectively.These values are 3-5 times greater than foliage litterfall. Thus fineroots constitute a major sink of carbohydrates and source of detritusfor the belowground ecosystem.
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