Riparian Cottonwoods:

Hydrology, Hydraulics and Health

Stewart Rood, David Pearce, Karen Zanewich and Larry Flanagan

Cottonwood Park

Lethbridge, AB

January

2019

Balsampoplar

Prairiecottonwood

Blackcottonwood

Narrowleafcottonwood

A Continental

Convergence of Cottonwoods

5 Poplars,

4 Interbreeding Cottonwoods

Cooke & Rood (2007) Botany

*

P. tremuloides

Hydrology – Water in open systems

≈ 0 MPa

Stream Flow: Declining due to human use & climate change

Alluvial Groundwater: Recharged with stream flow

Hydraulics – Water in constrained systems

≠ 0 MPa

Plant Hydraulics: < 0 MPa, negative tension

Water Potential (, psi) – Water availability

Alluvial Groundwater

(Phreatic, 0 MPa)

River

Capillary fringe

Soil moisture

(Vadose)

Transpiration, Tension, Cohesion

Xylem water: strands

Dry air, -100 MPa

Vapor Pressure Deficit

Demand

Supply

Leaf

Pre-dawn -0.5 MPa

~ Root zone

Mid-day -2 MPa

> Cavitation thresholds = Healthy

Pressure

Chamber

$2K

peltate trichomes

Elaeagnus commutata

Decre

asin

g

Water table

Water tracking – 2H,18O

Trees

Trout

Big Lost R., ID

Aquatic and Riparian

Ecosystems

Require Instream Flow

Healthy

Unhealthy

Stressed

(Dead)

Rood et al. (2003) Tree Physiol

Health

Lower St. Mary River

male

female

Rood et al. (2016) River Res Appln

Chronology: ~99% mortality – 1951-2015

Aerial photos, tree cores, river Q, groundwater patterns

Flow restoration

Indicators = Health Measures

Diagnostic

Quantitative

Near Real-Time

‘Dendroscope’

Bridge Grove

Irrigated

Golf Course

Oxbow &

Wetland

River

Gauge

Flux

Tower

*

*

*

*

Groundwater

Well

Lethbridge – High Level Bridge

5

15

25

m

Seasonal & Interannual Variation

Yang, Rood, Flanagan (in press) Ag For Meteor

wet drydry

5

2. 5

0

10

20

30

40

0:00 3:00 6:00 9:00 12:00 15:00 18:00 21:00 0:00

Sa

p F

low

(g

h-1

cm

-2)

Time (hour)

After Irrigation

DOY 240

‘Maria’ – P. angustifolia

Diurnal Variation

~(Cox et al. (2005) W N Am Nat)

Thermal Dissipation Probes

(TDPs)

High Flow & Wet = Healthy8/13/2014

Low Flow & Dry = Stressed8/8/2018

Irrigated

Golf Course

Riparian

Woodland

Normalized Difference Vegetation Index (NDVI, below), and

Near Infrared Reflectance of Vegetation (NIRV; Badgley,Field,Berry (2017) Sci Advances)

What does this reveal?

Assim

ilatio

n?

Tai, Mackay, Sperry, Brooks, Anderegg,

Flanagan, Rood, Hopkinson

Perc

ent Loss C

onducta

nce

0

10

20

30

40

50

60

70

80

90

100

-3.5 -3 -2.5 -2 -1.5 -1 -0.5 0

Xylem pressure (MPa)

Pe

rce

nt

loss

co

nd

uct

ivit

y

PLC = 100/(1+ ea(ψ-ψPLC50))

Male tree 1, shoot 1

ψPLC50 = -2.11 MPa

Female tree 1, shoot 1

ψPLC50 = -1.94 MPa

-2.5

-2

-1.5

-1

-0.5

0

Females Males

ψP

LC5

0 (

MP

a)

4 trees, 3 shoots per tree

Cavitron embolized

functional

P. angustifolia P. x acuminata P. deltoides

Complexity or Opportunity?

$2K

Water

River Q, stage, regime

Groundwater depth

Soil water

Source tracking – 2H,18O

Hydrology – Hydraulics

Health Indicators

Canopy

Leaf Area Index

Phenology

Thermal Imaging

Branch Sacrifice

Dieback

Weather: T, Ppt

Vapor Pressure Deficit

Ecosystem

Fluxes

Satellite Derived

Vegetation Indices

Leaf

Morphology/Stomata

Water Potential

Conductance/Transpiration

Photosynthesis/Water Use Efficiency13C, N

Branch

Seasonal & Annual Growth

Sap Flow

Xylem Water

Water Potential

Hydraulic Conductance

Xylem Cavitation

Trunk

Seasonal Growth

Annual Rings – 13C, 18O

Sap Flow

Root

Distributions

Symbionts

0.55

0.60

0.65

0.70

232 234 236 238 240 242 244 246 248

Wate

r le

vel (m

)

Time (DOY)

2017 - Dry

2012 - Normal

Water Table

Daily Drawdown

Year Diurnal

Amplitude

Phreatic

Water Use

Condition

2012 ~ 2 cm 5 mm/d Healthy

2017 ~ 1 cm 2.5 mm/d Stressed

specific yield

$2K – 2 & telemetry

Rood et al. (2013) Plant Cell Environ

Scale

Leaf to woodland,

Spatial area

Accessibility

Cost, Time effort,

Complexity,

Instrumentation

Diagnosis

Useful information,

Time frame &

Dynamics

0

2

46

810

0

1

2

3

4

5

6

7

8

9

10

0 1 2 3 4 5 6 7 8 9 10

Dia

gn

osis

Remote Sensing

Vegetation Indices

Flux Tower

Scale

Accessibility

Water Well

Observation

Riparian Cottonwoods:

Hydrology, Hydraulics and Health

Stewart Rood, David Pearce, Karen Zanewich and Larry Flanagan

Cottonwood Park

Lethbridge, AB

January

2019

Perf

orm

ance

low highelevation

wet dryflood drought

water

reproductiveallocation

female male

broaderniche

♀♂

seedlingrecruitment

pollen

seeds