dr. ashley m. matheny department of geological sciences ...jackson school of geosciences department...

Department of Geological SciencesJackson School of Geosciences

The theoretical basis for tree hydraulics

Dr. Ashley M. MathenyDepartment of Geological Sciences

University of Texas at Austin

Keck Institute for Space StudiesSensing Forest Water Dynamics From Space: Towards Predicting the Earth

System Response to Droughts October 14-18. 2019


Nevada.usgs.gov

Vegetation-atmosphere feedbacks

Below ground processes

Atmospheric processes

Vegetation

C H2O


Sap leaks from a birch tree during sensor installation in real time

How much water is flowing?


Water transport: the basics


Water movement inside of a plant

From Bohrer et al 2005, WRR


The onset of hydraulic limitations

From Brodribb et al. 2015, New Phytologist


Cavitation and hydraulic vulnerability

From Maherali et al. 2006, PC&E

Xylem water potential (-Mpa)

Perc

ent l

oss c

ondu

ctiv

ity


Trading safety for efficiency?

• A perfect tradeoff of safety and efficiency doesn’t exist (Gleason 2016, New Phytologist), because compounding variables abound

From Manzoni 2013, New Phytologist

Xylem water potential gradient @ max transpiration

Xyl

em h

ydra

ulic

con

duct

ance


Trading carbon for water:Carbon maximization theory

Max

xyl

em te

nsio

n ef

ficie

ncy

From Anderegg et al. 2018, Ecology Letters

Department of Geologic SciencesJackson School of Geosciences

Day of year

Sap

flow

(g m

-2s-1

)

Soil

moi

stur

e (%

)

Prec

ipita

tion

(mm

)Consequences of hydraulic strategies

Matheny et al. 2017, Ecohydrology

“Mini drought”


Diurnal leaf water dynamics

Red oakRed maple

Pre-

daw

n Ψ

L (b

ar)

Mid

-day

ΨL

(bar

)

Soil moisture (%) Soil moisture (%)

Thomsen et al. 2013, Forests

*Note: 10 bar = 1 MPaMeasuring leaf water potential with Alyssa Wunderlich (REU), summer 2014

N.S.

N.S.


Reliance on biomass capacitance

Matheny et al. 2015, Ecosphere

“Mini drought”

Stor

age

(kg)

Soil

wat

er c

onte

nt (m

3 m-3

)

OakMapleSoil water content

Stor

age

(kg)

Soil

wat

er c

onte

nt (m

3 m-3

)Capacitance sensor in maple, 2016

Day of year


Maple

R2 = 0.53P < 0.0001

Water storage dynamics with declining soil water

WETDRY

Diu

rnal

wat

er w

ithdr

awal

(kg)

Soil water potential (MPa)


Differential access to water in the root-zone

• D-excess:δD-8* δ18O


δ2 H (‰

VSM

OW

)

δ18O (‰ VSMOW)

(+) d-excess

(-) d-excess


The framework for a whole plant hydraulic strategy

McCulloh et al. 2019, PCE


Isohydricity as a whole plant response

Martinez-Vilalta & Garcia-Forner 2017, PCE


Isohydricity as a whole plant response

McCulloh et al. 2019, PCE

Novick et al. 2019, PCE

= + +

= +


Can we classify species based on hydraulics?

Meinzer et al. 2016, Ecology Letters

Blue Oak Scouler’s Willow


Correlations among hydraulic traits?

Fu et al. 2019, PCE Hydroscape area

Stem

Cap

acita

nce

(kg

m-3

MPa

-1)

Leaf

Cap

acita

nce

(kg

m-3

MPa

-1)

Leaf

hyd

raul

ic

cond

ucta

nce

(mm

olm

-2M

Pa-1

)

Stem

hydr

aulic

co

nduc

tivity

(kg

m-1

s-1M

Pa-1

)


Hydraulic “trait spaces”

Mursinna, et al. Forests 2018


Its not just about depth anymore Underrepresented parameters: Roots

Agee, et al. In prep


Hydraulic strategy influences growth


• 2001-2014• Maple: n = 423• Oak: n = 114

Dendrometer (Saskatchewan)


Changes to canopy structure and composition

Disturbance

Leaf

are

a in

dex

(m2

m-2

)

Control

• Control LAI ≈ 3.89 m2m-2

• Disturbance LAI ≈ 3.68 m2m-2


Water limitation produces largest plot-scale differences

WETDRY


Within ecosystem divergent hydraulic function is common!


The difficulties of scale

Can we connect hyper-local measurement to big-picture understandings of ecosystems?


Scaling from tree to ecosystem level

DBH (cm)

Control Disturbance

• Trees within the same histogram ‘bin’ are assumed to transpire similarly.

Multispectral imagery of UMBS

Aerial LiDAR of UMBS


Scaling from tree to ecosystem level

Sap flux Latent heatTota

l sea

sona

l flu

x (W

m-2

grou

nd)

Control


Intra-specific trait variation

Anderegg 2015, New Phytologist


How does drought effect the trees that live?

New challenges

Bohrer, et al. AGU 2018


Hysteretic responses to water stress

Bohrer, et al. AGU 2018


A deeper perspective on xylem networks

Mrad, et al. 2018 PCE


Acknowledgements

Gil Bohrer, Peter Curtis, Liz AgeeRich Fiorella, Chris Vogel, Tim Morin, Camilo Rey-Sanchez, Alyssa Wunderlich,Valeriy Ivanov, Karina Schäfer, Chris Gough, Luke Nave, Julia Thomsen, Golnaz Mirfenderesgi, Ana Maria Restrepo Acevedo, Austin Rechner, A. Rio Mursinna, Airborne LiDAR – NCALM (UMBS data)P.E.O. Chapter AV


Vegetation plays a central role in water, energy, and nutrient cycles

Plants control hydraulic function dynamically!

New measurements and models can improve our understanding of hydrosphere-biosphere-atmosphere exchange

dr. ashley m. matheny department of geological sciences ...jackson school of geosciences department...

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