COS 87-7 - Whole tree root excavation to learn about root water extraction

Thursday, August 11, 2011: 10:10 AM
Ballroom F, Austin Convention Center
Peter C. Hartsough1, Armen Malazian1, Ekaterina Roudneva1, Rune Storesund2 and Jan W. Hopmans3, (1)Land, Air and Water Resources, University of California, Davis, Davis, CA, (2)Storesund Consulting, (3)Soil Science Society of America President

In September of 2010 we excavated the root system of a mature (> 60years old) white fir (Abies concolor), using compressed air to remove the soil surrounding the roots.  This method left the roots intact and enabled quantification of root density with depth in addition to in situ root structure.  The roots were imaged using Terrestrial LiDAR to build a 3-D model of root size and density with respect to various soil horizons.  The LiDAR images allowed us to also determine root volume of this tree.  


The results from this experiment were used to test some of the assumptions about water extraction from the subsurface in an adjacent monitored tree, Critical Zone Tree One (CZT-1).  We have been monitoring soil moisture extraction by white firs at the site since the fall of 2008 and have used that data to develop a regional water balance.  Uncertainty exists in the depths from which the roots can extract water, the depths that the roots are able to penetrate into the underlying saprolite/ bedrock, and the roll that mycorrhizal associations play in this soil/tree coupled system.  Multiple mycorrhizal layers were observed during the root excavation, mostly in the top 75cm.  Below that level, there were few fine roots and even fewer mycorrhizal layers.  Stable isotopes can also be used to trace water extraction from shallow vs deep soil and potentially provide some insight into fungal assisted soil water extraction.

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Banner photo by Flickr user greg westfall.