Biomass and distribution of fine and coarse roots from blue oak (Quercus douglasii) trees in the northern Sierra Nevada foothills of California |
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Authors: | Millikin Catherine S Bledsoe Caroline S |
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Institution: | (1) Land, Air, and Water Resources Department, University of California, Davis, Davis, CA 95616, USA |
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Abstract: | This research adds to the limited data on coarse and fine root biomass for blue oak (Quercus douglasii Hook and Arn.), a California
deciduous oak species found extensively throughout the interior foothills surrounding the Central Valley. Root systems of
six blue oak trees were analyzed using three methods — backhoe excavation, quantitative pits, and soil cores. Coarse root
biomass ranged from 7 to 177 kg per tree. Rooting depth for the main root system ranged from 0.5 to 1.5 m, with an average
of 70% of excavated root biomass located above 0.5 m. Of the total biomass in excavated central root systems, primary roots
(including burls) accounted for 56% and large lateral roots (> 20 mm diameter) accounted for 36%. Data from cores indicated
that most biomass outside of the root crown was located in fine roots and that fine root biomass decreased with depth. At
surface depths (0–20 cm), small-fine (< 0.5 mm diameter) roots accounted for 71%, large-fine (0.5–2.0 mm) for 25%, and coarse
(> 2 mm) for 4% of total root biomass collected with cores. Mean fine root biomass density in the top 50 cm was 0.43 kg m−3. Fine root biomass did not change with increasing distance from the trees (up to approximately 5 m). Thus, fine roots were
not concentrated under the tree canopies. Our results emphasize the importance of the smallest size class of roots (<0.5 mm),
which had both higher N concentration and, in the area outside the central root system, greater biomass than large fine (0.5–2.0
mm) or coarse (> 2.0 mm) roots.
This revised version was published online in June 2006 with corrections to the Cover Date. |
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Keywords: | coarse root excavation core method fine root biomass quantitative pits Quercus douglasii root distribution |
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