Roots, Root System, Root Structure, Root Cap & Root Development
Tree Root Architecture: Patterns and Geotechnical Roles … · Tree Root Architecture: Patterns and...
Transcript of Tree Root Architecture: Patterns and Geotechnical Roles … · Tree Root Architecture: Patterns and...
Tree Root Architecture: Patterns and Geotechnical Roles in Levees
Levee Vegetation Research SymposiumSacramento, California
August 28, 2012
Shih‐Ming Chung and Alison M. BerryUniversity of California, Davis
CollaboratorsGerald Bawden, U.S.G.S.; Keir Keightley, UC Davis; Sandra Bond, U.S.G.S.; John Lichter, Tree & Associates; Vic Claassen, UC Davis
California’s vegetated levees provide critical flood protection ‐
River Partners
Yet riparian forests provide critical habitat and ecosystem services.
How should levee trees be managed?G Fricker
Pocket Levee, Sacramento River
The central scientific question: What is the impact of trees and tree roots on levee safety?
Slope stabilizationSeepage
Key knowledge gap identified:How do tree roots actually grow in levees?
This symposium: What can science contribute?
CLVRP project created: Tree Root Architecture in Levees
2. To create 3D models of tree root architecture that will help determine the potential risks and benefits of tree roots in levees.
Project Objectives
1. To excavate and digitally map tree root systems in levees.
Tree root system properties
Limits of methodology
Prologue – what we know
WHERE: Surface 1-3.5 ft provide best conditions for growth. Typically 80% of the root system is in this zone.
1 meter
combinations of 3 or 4major woody systems
Root architecture: Structural rootsHorizontal rootsSinker rootsTap root – spp./soils
WHAT•Tree roots in many soil conditions grow horizontally more than vertically.
Conditions are usually best in the upper part of the soil profile.
HOW: The actual architectural pattern depends on key growth conditions:•Soil moisture•Aeration •Mechanical impedance (soil compaction)
Lyford 1980
Soil surface
1 meter
0
1
2
3
4
20 21 22 23 24 25 26 27 28 29 30 31 32
Horizontal (ft)
Dep
th (f
t)
Roots <10mm Roots 10-19 mm
zone with almost no roots
1.421.631.38
b.d.
• Tree root systems are LARGE.• Tree root systems in situ are SURROUNDED BY SOIL.• Tree root systems are THREE‐DIMENSIONAL.
Trench profile mapping could show that tree roots
avoid compacted soil layers in Mayhew Levee.
But this method is limited, because…
1. Air Spade excavation (pneumatic)
2. 3D laser imaging (ground‐based T‐ LiDAR)
3. Digitized data enables precise measurement and 3D modeling of key spatial parameters.
One way to overcome these hurdles
• As you will see, architectural patterns of trees growing in sandy levees in California have distinctive, quantifiable properties.
• The modeling methods in Shih‐Ming’s presentation can be widely applied.• However, specific configurations of tree root systems will vary according to soil,
climate and levee properties (see Caroline Zanetti’s presentation).
• This symposium brings together many approaches and new sources of information to understand behavior of tree root systems in levees, as we will hear in presentations to follow.
• We all contribute to a much‐needed scientific knowledge base about biomechanical and geotechnical properties of trees on levees, with insights from different angles, much like the story of the blind men and the elephant.
Summary
Tree root growth patterns and geotechnical roles on levee
•Shih‐Ming Chung and Alison M. Berry
Methods and Applications
Part II
1. New field method for acquiring root system data
2. Data processing and model building
3. Analyzing root system patterns along levees
4. Data/models applications
Fieldwork Lab processing
Quantitative model Applications
Systematic approach to acquire and categorize in situ root system data
• Consider root system complexityand spatial attributes
• Use critical variables of tree root architecture to determine the range (root system extent) and resolution (minimum unit)
• Include above‐ground, slope, below‐ground compartments
• Classify the data as spatial points (1D), linear connections (2D), surface patterns (3D), and resulting thematic spatial composition
1 Pneumatic excavation
2 T‐LiDAR scanning
Pneumatic Excavation And LiDAR Scanning (PEALS) system
• 15 Valley Oaks
• 5 Cottonwoods
• Most trees (18/20) on the water-side levee slope.
• Two control trees (flat)
20 TREES IN TOTAL
3D and in-situ
1 2
3 4
Pneumatic excavation (compressed air) in situ root systems
Ground‐Based Tripod LiDAR scanning
1 2 3
4 5
Process field data and acquirethe resulting models
• Stage I: T-LiDAR point cloud data (3D)
• Stage II: conversion of point-cloud data
- Tomographic slicing, hierarchical nested dataset, biomass model
- Vectorization of polylines, topological dataset, vector model
Stage I
Prescan: aboveground architecture and soil surface
LiDAR scan after root excavation Assembly of aboveground, soil surface, and root system
3D LiDAR image assembly of Pocket Levee Oaks (The Pocket site, Sacramento, CA)
1 2 3
4
Stage II
• Tomographic slicing (hierarchical nested dataset) ‐‐ Root Biomass Model
• Vectorization of polylines (topological dataset) ‐‐ Root Vector Model
(x1, y1, z1)
(x2, y2, z2)
(x3, y3, z3)
(xn, yn, zn)
3D Point‐cloud data, XYZ format
Set up the coordinate system
z axis: vertical axis
x axis: parallel to the levee
y axis: perpendicular to the levee
Origin of the coordinate systemtree trunk center at the slope surface
Upslope Downslope
Root biomass model
• Design the model based on spatial patterns: size, linkage, distribution
• Use root cross‐sectional area or diameter as the critical variable
• Sample the variables in virtual trench profile (2D sampling)
• Tomographically reconstruct the 3D hierarchical nested dataset
Virtual trench profile as the tomographic slices
Root CSA
Virtual trench profile
Longitudinal Radial(Upslope, Downslope, Vertical)
Tomographic reconstruction can use linear or radial slices
2D plotR statistical program
Spatial analysis formatArcGIS
Spatial metricsFragstat
Slice ID Root # Root CSA /Slice Root Cumulative CSA DTC
n n (m2) % (m)
Data sheet for root biomass model
Root vector model branching pattern and directionality
• Vectorize the point‐cloud data as “polylines”• Using azimuth angle (to the north pole), zenith
angle (to sky), root length, root order as the critical variables
• Reconstructing Topological relationship
Vectorizing the point‐cloud data
Point-cloud data
Making Polylines
Root ID Root order Azimuth angle Vertical angle Branching angle
Root length Branching point Root Type
n n Degree (˚) Degree (˚) Degree (˚) m m H, V, O
Data sheet for root vector model
Data analysis• Root system info• Root system morphological plasticity in relation to levee geometry
Root system morphological plasticity in relation to levee geometry
0o 360oAlternating growth directions
Shallow surface growth pattern
Tap root
2nd order
3rd
4th
5th
3rd
asymmetrySlope profile
symmetryParallel to the levee
Horizontal growth pattern
Root system Upslope VS. Downslope asymmetry
• Downslope side: more trees have further root extent, greater biomass, and higher root number
• Why are more roots on downslope side of the levee than upslope side?
Upslope Downslope
Further Root Extent 5 11
Greater Biomass 5 11
Higher Root Number 4 12
UpslopeLevee side
Downsloperiver side
Bulk density
0 m
150 m
Trees growing in flat ground
• General patterns of root systems on a flat plain may be more symmetrical (Stokes and Mettheck, 1996)
• Our results (One cottonwood and one valley oak in Vernalis) correspond with the previous study
• Symmetrical and absence of taproot
• Root biomass radially distributes with an exponential decreasing trend
Valley OakCottonwood
Data/Model applications
1.Below‐ground biomass estimation2.Levee slope stability modeling3.Levee slope surface erosion mapping4.Levee vulnerability assessment
2. Levee slope stability modeling
• Virtual trench profiles can be used to locate the root system within the potential failure plane of levee slope for modeling
• RAR and CSA can then be used to determine Factor Of Safety (FOS) in levee slope stability model
• RAR and CSA
Virtual trench profile of potential failure plane
3. Levee slope surface erosion mapping
• Land use and land cover mapping• General geomorphology mapping• Hydrological process mapping (soil – plant/root system – water dynamics)
• Resulting thematic map: Slope surface erosion map
4. Levee vulnerability assessment
• Surface process evaluation• Subsurface connectivity and slope stability evaluation
• Potential root system occurrence evaluation• Resulting vulnerability assessment map
Oliver KreylosJeffrey WuMolly FerrellJaylee TuilRon Lane
Student field crews:5 seasons/4 locations
Student lab interns:Stephanie LauGary BladenHannah StoneRyan SresovichJoe SchlottmanSan Joaquin River
National Wildlife RefugeEric Hopson
DWRRoy KrollDave Williams
River PartnersStephen SheppardJulie Rentner
Collaborators
Gerald Bawden, U.S. Geological SurveySandra Bond, U.S. Geological Survey
John Lichter, Tree & Associates
Vic Claassen, Soils & Revegetation, UC Davis
Keir Keightley, Geography, UC Davis
RD 1000 Paul Devereux
Acknowledgments