TITLE:
Tanoak (Notholithocarpus densiflorus) Coarse Root Morphology: Prediction Models for Volume and Biomass of Individual Roots
AUTHORS:
Brandon H. Namm, John-Pascal Berrill
KEYWORDS:
Belowground, Biomass, Carbon, Root Taper, Tree Root Architecture
JOURNAL NAME:
Open Journal of Forestry,
Vol.6 No.1,
December
9,
2015
ABSTRACT: Descriptions of tree root morphology inform design
of belowground biomass and carbon inventories and sampling for research. We
studied root morphology of tanoak (Notholithocarpus
densiflorus), an important component in mixed evergreen forests of
California and Oregon, USA. Tanoak re-sprouts from belowground lignotubers
after disturbances, and stores an unknown amount of carbon in coarse roots
underground. We sought to ascribe explanatory nomenclature to roots’
morphological features and to identify models describing tanoak root
morphology. Twelve tanoak root systems were excavated, dissected, and measured.
Roots tapered according to their circumference and location. Larger roots
closer to the lignotuber (located at the base of the tree stem) tapered more
rapidly per unit of length. Tanoak roots forked frequently. Root
cross-sectional area was preserved after forking events (i.e., the sum of
cross-sectional areas for smaller roots on one side of the fork correlated with
the adjoining large root). Occurrence and quantity of root branches (small
roots branching laterally from larger roots) was dependent upon length of the
source root segment. Our models of tanoak root morphology are designed to be
organized together to estimate biomass of any segment or collection of lateral
roots (e.g., roots lost/missed during excavation, or in lieu of destructive
sampling), given root diameter at a known distance from the lignotuber. The
taper model gives distal- and proximal-end diameters for calculation of volume
for segments of root tapering between forks. Frequency of forking and branching
can also be predicted. Summing the predicted mass of each lateral root segment,
branch, and forked segment would produce an estimate of mass for a contiguous
network of lateral roots.