A peek down under:

structural root architecture of some New Zealand native plants

Chris Phillips

Mike Marden, Jagath Ekanayake & Alex Watson

Disclaimer

We are not botanists!

We are not plant ecologists!

We are on the edge!

We play in the dirt!

We are statistically challenged!

Wadda ya know?

•• Context Context –– 3 strands3 strands•• What weWhat we’’ve done ve done –– 2 trials2 trials•• How we do itHow we do it•• What weWhat we’’ve foundve found•• How we use the informationHow we use the information•• Wrap upWrap up

In this talk….

•• Plantation forests for erosion controlPlantation forests for erosion control•• Pinus radiata and other exoticsPinus radiata and other exotics•• 19801980’’s to 1990s to 1990’’ss•• Effectiveness, densities, harvesting etcEffectiveness, densities, harvesting etc

Context 1 – hillslope stability

Context 1 – hillslope stability

Context 1 – hillslope stability

Context 1 – hillslope stability

•• Off the hills and into the rivers Off the hills and into the rivers –– ICM ICM •• Riparian restoration/rehabilitation effortsRiparian restoration/rehabilitation efforts•• Natives Natives vsvs exotics, Ecology exotics, Ecology vsvs function function •• Performance, build the K basePerformance, build the K base

Context 2 – river bank stabilisation

Context 2 – river bank stabilisation

• MAF – Govt policies - convergence• Climate change mitigation & Sustainable land

management (SLM) >> HCE• What to use, how effective, how much C,

what rate, where, management etc

Context 3 – Carbon & SLM

The Big Question?Can our New Zealand native plants perform E & SC Can our New Zealand native plants perform E & SC

functions as well as introduced plants?functions as well as introduced plants?

In geotechnical terms, how do we quantify the benefits of In geotechnical terms, how do we quantify the benefits of vegetation to soil stabilisation? vegetation to soil stabilisation?

Shear displacement

Without roots

With roots

What we’ve been doing

• Exotic species• 2 native trials • 1 MSc. on Cordyline

Riparian plant trial Cabbage trees

Czernin (2002) Czernin & Phillips (2005)

Marden, Rowan, Phillips (2007; 2005)Phillips & Marden (2006)

Common nameKaramu RibbonwoodKowhaiLemonwoodKohuhuLacebark MapouFivefingerCabbage treeRewarewaManukaTutu

Common nameKauri RimuKahikateaMiroTotaraMataiPuririTitoki

Sedge grass NZ Mountain flaxToe toe

Podocarp trial

What we’ve been doing - natives

Still in progress

The old The newThe hard

How we do it

• General growth patterns• Biomass• Root length• Root depth• Site occupancy• Root strength

What we’ve found

Root architecture

Root definitions

Root bole

Sinker

Sinker

Taproot

Lateral

Root architecture

• plateroot

• heartroot

• taproot

Tree root forms

5

7

25

13

What we’ve found – growth

Cabbage tree

(Cordyline australis)

Czernin (2002) Czernin & Phillips (2005)

1 year old 2 year old 3 year old4 year old

3.35 mWhat we’ve found – growth

(Psuedopanax arboreus)m

m

1 m

What we’ve found – growth

Kauri

Totara4 yr old

0

3 year oldsToe toe

Flax Carex

Kahikatea & Puriri

4m

What we’ve found – growth

1m

Coprosma robusta (karamu)

Pittosporum tenuifolium (kohuhu)

What we’ve found – root spread

5 year old

Mean max. root spread – 5 year old

What we’ve found – root spread

0

1

2

3

4

mapou

reware

wafiv

e.fing

erman

uka

karam

uko

whai

lacebark

cabb

age.tre

eko

huhu

ribbo

nwood tutulemon

wood

Roo

t Spr

ead

(m)

Mean max. root depth – 5 year old

50

45

40

35

30

25

20

15

10

5

0

mapou

five.f

inger

kohu

huko

whai

lemon

wood

manuk

arew

arewa

laceb

arktut

u

karam

urib

bonw

ood

cabb

age.t

ree

(cm)

What we’ve found – root depth

What we’ve found – root depth

RibbonwoodCabbage tree

5 year old

4202468

101214

mapou

reware

wafiv

e.fing

erman

uka

kowha

ilac

ebark

kohu

hulem

onwoo

dka

ramu

ribbo

nwoo

dtut

uca

bbag

e.tree

(kg)

Above-ground

Below-ground

What we’ve found – biomass

What we’ve found – root length

3 year old - woody

What we’ve found – root length

3 year old - all

What we’ve found – root length

3-5 year old - all

What we’ve found – variation

What we’ve found – variation

What we’ve found – variation

What we’ve found – variation

Data range – max, mean, min5 year old - woody

0

10

20

30

40

50

60

RataLac

ebark

Hard bee

chKowhai

Manuka

-1Man

uka-2

Red bee

chKan

ukaKohuhuKam

ahi

Fivefin

gerRew

arewa

Cabbag

e tree

Mountain bee

chDouglas

firRibbonwoodRad

iata p

ineLem

monwood

TutuKara

mu

Mea

n m

ax. t

ensi

le s

tren

gth

(MPa

)

Exotics

Watson & Marden (2005)

Willows 30 - 125 MPa

(1-4 mm diameter)

Riparian plant trial

What we’ve found – root tensile strength

Old FRI data

How we use it – Knowledge delivery

http://icm.landcareresearch.co.nz/

Planting types – radiata pine 3 yr old

Watson & Tombleson (2004)

How we use it – management

y = 4.8813xr2 = 0.9617

0255075

100125150175200

0 10 20 30 40

Mean root collar diameter (cm)

Roo

ting

dept

h (c

m)

11 yrGisborne plant trial

Cabbage tree root depth

How we use it – Allometry

1. Kanuka 16000 spha

2. Radiata 1250 spha

3. Radiata 800 spha

4. Radiata 500 spha

How we use it – relative root reinforcement

“Window of vulnerability”

Watson, Phillips, Marden (1999)

100% root site occupancy

Root site occupancy

How we use it – Models

100% root site occupancy

What about these bits?

Root site occupancy

How we use it – Models

Poplars5 yr

7 yr

9.5 yr

McIvor et al (2007)

Cabbage tree

Czernin & Phillips (2005)

4 yr 8 yr 25 yr

Totara

Marden & Phillips (unpub.)4 yr

?

?

?

?

?

Site occupancy

Mean maximum root length radius

100%

0%

“Effective” root spread radius

Root reinforcement index (RFI) = Root surface area

Root spread area

??

How we use it – root site occupancy model

Effective root spread measured & predicted using model equation

0

20

40

60

80

100

120

2 3 4 5Time (years)

Effe

ctiv

e R

oot S

prea

d di

stan

ce fr

om s

tum

p(c

m)

5-Finger5-FingerCabage_TreeCabage treeKaramauKaramauKohuhKohuhuKowhaiKowhaiLacebarkLacebarkLemonwoodLemonwoodmanukaManukaMapouMapouRewarewaRewarewaRibbonwoodRibbonwoodTutu

)exp(5.0 xc

xbay ++=

Site occupancy (%) for planting density 1m x 1m

25

50

75

100

2 3 4 5 6 7Time (years)

Site

occ

upan

cy (%

)

5-FingerCabage treeKaramauKohuhuKowhaiLacebarkLemonwoodRewarewaRibbonwoodTutuMapou

How we use it – root site occupancy & density

Site occupancy (%) for planting density 2m x 2m

0

25

50

75

100

2 3 4 5 6

Time (years)

Site

occ

upan

cy (%

)

5-FingerCabage treeKaramauKohuhuKowhaiLacebarkLemonwoodRewarewaRibbonwoodTutu

How we use it – root site occupancy & density

Avondale Stream, existing channel, May 2004How we use it – Visualisation

Avondale Stream, Carex added

Avondale Stream, Juncus added

Avondale Stream, native trees added

Existing channel has little in-stream cover

Riparian grasses provide cover & spawning habitat

Cabbage trees suitable above the wetland grasses

Tree ferns also suitable above wetland grasses

Chockie fish time…

• What native had the greatest tensile root strength?

• What do we call the gadget we use to expose the root systems of plants?

• What’s so special about the root systems of cabbage trees?

Fivefinger

• We know more than we did before• Hard won data• Natives can grow quickly • Maybe need to look more at function• Opportunities for further research

– Optimisation for site reinforcement– Carbon modelling …..– Modelling in general…

Wrap up

“The unhealthiness in our world today is in direct proportion to our inability to see it as a whole.”

Peter Senge