a path forward to improve the representation of fine roots...

A path forward to improve the

representation of fine roots in

terrestrial biosphere models

Colleen M. Iversen

Climate Change Science Institute and

Environmental Sciences Division

Oak Ridge National Laboratory

13 August 2014

Co-conspirators:

Luke McCormack (CAS)

Jeff Warren (ORNL)

Anthony Walker (ORNL)

Xiaojuan Yang (ORNL)

Dali Wang (ORNL)

A continuing goal is to LINK

empirical data with model

structure and process.

Models may help pinpoint mechanisms and

explain dynamic responses

Iversen, 2010 (New Phytologist)

a. G’DAY

2.0

7 m



a. G’DAY b. LPJ

2.07

m

1.5

m




a. G’DAY b. LPJ c. CLM-CN

2.07

m

1.5

m

3.43

m




Warren et al., 2014 (New Phytologist)

Continuing issue is appropriate representation

of root form & function at multiple scales

At the global scale, plant

functional types (PFTs) are

groups of traits that represent,

or relate to, PLANT FUNCTION in

large-scale models.

‘Tree Roots’, Vincent van Gogh, 1890

Most plants are grouped into PFTs

according to ABOVEGROUND traits.

How can we inform the

representation of BELOWGROUND

PROCESSES in large-scale

models through PFTs?

We (empirical scientists) need

to PROACTIVELY provide the

information needed for model

parameters and processes.

Improve the representation of

roots in the next-generation

TERRESTRIAL BIOSPHERE

MODELS.

WORKSHOP GOAL:

*Workshop support from Office of Biological

and Environmental Sciences in the Department

of Energy’s Office of Science

It was important to bring

together an interdisciplinary

team of ROOT AND RHIZOSPHERE

ECOLOGISTS, MODELERS, and

DATABASE MANAGERS.

Workshop continued a historical focus on

fine roots and their representation in models

1980 1985 1990 1995 2000 2005 2010 2015

1980 1985 1990 1995 2000 2005 2010 2015

…UM, WHAT

ABOUT

MYCORRHIZAE?

YES, ROOTS ARE

IMPORTANT

ROOTS SHOULD PROBABLY

BE BETTER REPRESENTED

IN LARGE-SCALE MODELS

LET’S DO IT!

*

HOW CAN THIS

BE DONE?

ARE ROOTS

IMPORTANT?

THE INCLUSION OF

BELOWGROUND

PROCESSES AFFECTS

MODEL OUTCOMES

Workshop continued a historical focus on

fine roots and their representation in models

What are the gaps between current

MODEL REPRESENTATION of roots and

EMPIRICAL UNDERSTANDING of roots

based on current measurements?

WORKSHOP DISCUSSION:

PF

T p

ara

mete

r va

lue

s

0.0

0.5

1.0

1.5

2.0

Plant functional type

1 2 3 4 5 6 7 8 9 10 11 12 13 14

30

35

40

45

PF

T p

ara

me

ter

va

lue

s

0.0

0.5

1.0

1.5

2.0


1 2 3 4 5 6 7 8 9 10 11 12 13 14

30

35

40

45

PF

T p

ara

mete

r valu

es

0.0

0.5

1.0

1.5

2.0


1 2 3 4 5 6 7 8 9 10 11 12 13 14

30

35

40

45

Root C/N ratio

PF

T p

ara

mete

r va

lue

s

0.0

0.5

1.0

1.5

2.0


1 2 3 4 5 6 7 8 9 10 11 12 13 14

30

35

40

45

PF

T p

ara

me

ter

va

lue

s

0.0

0.5

1.0

1.5

2.0


1 2 3 4 5 6 7 8 9 10 11 12 13 14

30

35

40

45

PF

T p

ara

mete

r valu

es

0.0

0.5

1.0

1.5

2.0


1 2 3 4 5 6 7 8 9 10 11 12 13 14

30

35

40

45

Root C/N ratio = 42

New roots / new leaves = 1 (or 2)

Cellulose fraction = 0.5

Labile and lignin fractions = 0.25

Do we agree on an IDEAL

CONCEPTUAL REPRESENTATION of root

processes that could be made

numerical in a model? What are the

PRIORITIES for the next steps in the

evolution of model representation?


What are the BEST ROOT DATA

AVAILABLE across the globe for

model use?


Number of entries

0 100000 200000 300000 400000

Y D

ata

1

2

3

4

5

Plant traits

Leaf traits

Seed traits

Stem traits

Root traits

Root traits underrepresented in TRY

J. Kattge, MPI

Do we have continuous

measurements of the relationships

between ROOT PROCESSES AND

ENVIRONMENTAL CONDITIONS for

representation in models?

Allen & Kitajima, 2013 (New Phytologist)

Continuous sensor and observation systems are needed

We developed a PATH FORWARD to

improve the representation of fine

roots in terrestrial biosphere models.

Develop a ROOT TRAIT DATABASE,

and let it guide our priorities for

future data collection.

*PLEASE SEND US DATA!*

([email protected])

1. A ROOT TRAIT DATABASE:

http://www.try-db.org/TryWeb/Home.php

Root

diameter (mm)

Specific

root length (m g-1)

Root tissue

density (g cm-1)

Branching

intensity (# roots per higher

order root)

Branching

architecture (root length per

higher order root)

Type of

mycorrhizae (AM or EM)

EM

colonization (% tips colonized)

% AM

colonization (% length colonized)

Survivorship (roots year-1)

Lifespan (days)

Turnover rate (% growing season-1)

Respiration

rate (nmol O2 g

-1 s-1)

Respiration

rate by mass (nmol s-1 m-2)

Stele

diameter (µm)

Cortex

diameter (µm)

Root

porosity (area)

Vessel

diameter (µm)

Absolute

biomass (g m-2)

Total root

biomass (%)

Annual

production (g m-2)

Annual

mortality (g m-2 year-1)

Biomass

turnover (g m-2 year-1)

Root C, N, K, P,

Al, Ca, Mg (mg g-1)

Root Cr, Ni, Cu,

Zn, As, Cd, Pb (mg kg-1)

C:N ratio

Ion

concentration

(Na+ and Cl-) (mg g d.wt-1)

Carbohydrates

(TNC) (mg g-1)

Mean root

stable δ15N (%)

Develop a MODULARIZED VERSION

OF THE COMMUNITY LAND MODEL to

test effects of environmental drivers

on root and rhizosphere dynamics,

and effects of changing model

parameters on ecosystem

processes.

2. IMPROVED MODEL INTERFACE:

“Root Window”

Function

• Allocation

• Phenology

• Mortality

• Water uptake

• Nutrient uptake

• Respiration

Structure

• Vertical dist.

• Horizontal dist.

• Size classes

• C:N:P

Wang et al., 2014 (EMS)

Add an ADDITIONAL FINE-ROOT POOL

to the Community Land Model

representing ephemeral,

ABSORPTIVE ROOTS, and

parameterize PFTs with data

compiled in the root trait database.

3. MODIFIED MODEL STRUCTURE:

Where global data are unavailable,

begin with phylogeny

Species

Root

dia

mete

r (

m)

0

200

400

600

800

1000Euphorbiaceae

Magnoliaceae

Lauraceae

Fagaceae

Other families

Kong et al. 2014. (New Phytologist)

Gain a CONSENSUS FROM THE

BROADER COMMUNITY on the relative

importance of different root traits.

4. CONTINUE TO SOLICIT COMMUNITY INPUT:

There are some things that WE

DON’T UNDERSTAND well enough to

represent in terrestrial biosphere

models.

The NEXT STEPS in our

understanding of roots and their

role in the ecosystem involve NEW

QUESTIONS, NEW METHODS, NEW

TECHNOLOGY, and IMPROVED

REPRESENTATION of root

processes in models of all scales.

Henning, Weston, Schadt; ORNL

Taylor et al. 2013 (Ecology Letters)

De Graaff et al., 2014 (SBB)

Yang et al., 2014 (Biogeosciences)

Wei et al., 2014 (DAAC)

Warren et al., 2013 (Plant and Soil)

RhizoSystems, LLC

Iversen, Childs, 2014

www.rhizonetscience.com

Fine roots are where I START

thinking about ecosystem

processes, but not where I stop,

and models need the bigger

picture too.

WHAT IF MY RESEARCH ISN’T ON FINE ROOTS?

WHOLE-PLANT C ALLOCATION · SOIL NUTRIENT AVAILABILITY · SOIL C STORAGE

To track our progress, and LEND

YOUR VOICE (and your data) to the

effort, following us at:

http://web.ornl.gov/~ciz/Roots_in_Models.html

Funding:

Office of Biological and Environmental Research in the DOE Office of

Science supported the Roots in Models Workshop and continuing

work.

Workshop attendees:

Mike Allen, Allison Boyer, Eddie Brzostek, Joanne Childs, Bob Cook,

Marie-Anne De Graaff, Dave Eissenstat, Adrien Finzi, Josh Fisher,

Lianhong Gu, Paul Hanson, Colleen Iversen, Andy Jones, Shujiang

Kang, Jens Kattge, Tong King, Jitu Kumar, Hans Lambers, Roser

Matamala, Melanie Mayes, Rich Norby, Rich Phillips, Shafer Powell,

Seth Pritchard, Dan Ricciuto, H. Jochen Schenk, Ingrid Slette, Jens-

Arne Subke, Peter Thornton, Collin Timm, Anthony Walker,

Gangsheng Wang, Jeff Warren, Dave Weston, Stan Wullschleger,

Xiaojuan Yang

Acknowledgements http://web.ornl.gov/~ciz/Roots_in_Models.html

[email protected]

a path forward to improve the representation of fine roots...

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