Soil moisture impacts of redcedar encroachment

in the Cross Timbers ecoregion

Chris Zou, Lei Qiao, Elaine Stebler, Bharat Acharya Department of Natural Resource Ecology and Management

Oklahoma State University

Multiple million acres of redcedar encroachment in Oklahoma

OSU Rangeland Research Station (OSURRS)

10 – 30%, 44,522 ac.

30 – 70%, 27,289 ac.

> 70%, 8,420 ac.

Modified from Mark & Dickinson 2008 Frontiers in

Ecology and the Environment

“In areas where

natural runoff is less

than 10% of mean

annual precipitation,

afforestation can result

complete loss of

runoff.”

“Water levels going back

to 1925 for four of

Texas’s biggest rivers”

revealed “Rivers on the

Edwards Plateau are not

disappearing, but they

are increasing in flow.” Wilcox and Huang 2010 Geophysical Research Letter

E grass T grass

Recharge

Runoff

E grass T grass T cedar

Runoff

Recharge

Cedar trees

E cedar

ECH2O Station

ΔSoil ⌫ ⌫

⌫ Sapflow Unit

⌫

⌫

⌫

⌫

Acknowledgement

Jenny Hung Amanda West Shujun Chen Giulia Caterina Elaine Stebler

Dave Engle Don Turton Rod Will Sam Fuhlendorf Kim Winton

Funding sources

• South-central Climate Science Center

• Oklahoma Agricultural Experiment Station

• USGS/NWRI grant (G09AP00146)

• NSF DEB-1413900

• NSF EPSCoR (NSF-1301789)

Use of temporal soil moisture data to

interpret streamflow responses

High resolution soil moisture data to

constraint and parameterize hydrological

model

Infiltration excess overland flow

Saturation excess overland flow

Subsurface runoff

Streamflow generation in rangeland

E01

E02

G01 G02

G03

E03

F01

F02

F03

H flume

Soil moisture station

Watershed boundary

100 m N

E1

E3

E2

F1

E04

E05

E06

E07

E08

E09

G04

G05

G06

G07

G08

G09

G1

G2

G3

• 3 grassland watersheds and 4 redcedar

watersheds;

• 3 EC-5 swc arrays for each watersheds

(a total of 21 stations);

• Add 9 stations in oak watersheds in 2015

from NSF EPSCoR

Soil water content (SWC) and Water Depth

• Grassland watersheds (n = 9)

• Encroached watersheds (n = 12)

• Water content at 4 depths every 15 min

• Soil water storage (1 meter soil)

= SWC5 * 0.1+SWC20*0.2+SWC45*0.3 + SWC80*0.4

Streamflow

Grassland watersheds Redcedar watersheds

Construction of flumes and weirs

Volu

metr

ic w

ate

r conte

nt (m

3 m

-3)

0.0

0.2

0.4

0.0

0.2

0.4Grassland

Encroached

0.0

0.2

0.4

0.0

0.2

0.4

Date

6/09 12/09 6/10 12/10 6/11 Wate

r depth

(mm

)

150

300

450 Grassland

Encroached

B4:80 cm

C2: 0 - 100 cm

B3: 45 cm

B2: 20 cm

B1: 5 cm

6/09 12/09 6/10 12/10 6/11

Pre

cip

.(m

m)

0

50

100

150

200

-500

50

A1: Monthly rainfall

A2: Divergence from mean (P - P)

DormantActive

Juniper trees

Grasses

C1: Phenology

Zou et al. 2014. Hydrological Process

Ru

no

ff d

ep

th

0

2

4

6

8

10

12

14

16

Grassland

Encroached

Pre

cip

itati

on

0

10

20

30

40

50

2010 20112009

86 10 12 2 4 6 8 10 12 2 4

Wa

ter

de

pth

0

100

200

300

400Saturation excess runoff threshold

A.

B.

C.

Coupling of runoff and soil water storage

Precipitation = 915 mm

G E

An

nu

al

run

off

de

pth

(m

m)

0

40

80

120

160

2008 15%

2%

G E G E

2009 2010

Precipitation = 902 mm Precipitation = 668 mm

15% 14%

2% 5%

Do water retreat when redcedars move in?

Use of temporal soil moisture data to

interpret streamflow response

High resolution soil moisture data to

constraint and parameterize hydrological

model

• Models mostly developed for cropland, grassland

or forest

• Lack of species specific parameter for eastern

redcedars

• Lack of long term streamflow data from large

eastern redcedar watersheds for calibration and

validation

• Limited runoff events from experimental

watersheds

Challenges in simulating redcedar impact on streamflow

Wu et al. [2001]: (SPUR-91) model: 200 mm

increase of streamflow assuming woody cover being

reduced by 40%.

Afnowicz et al. [2005]: SWAT modeling within the

Edwards Plateau. ET reductions ranging from 31.94

to 46.62 mm/yr by removing juniper.

Bumgarner and Thompson [2012] suggested water

yield increase by an average of 36 mm by removing

juniper.

SIM

. Woody encroachment impacts on water budget: Uncertainty

High resolution soil moisture data to constraint

and parameterize hydrological model

Daily Stats

Model Validation in lower Cimarron River Basin Sim 1 Sim 2

Gauge

#1

Gauge

#2

Gauge

#3

Gauge

#4

Sim 1

Sim 2

Spatial and temporal swc data holds the key to

interpret streamflow response, especially in water-

limited system

Local swc network is effective in improving

hydrological models

Summary and future research opportunities

Summary and future research opportunities

Subsurface flow and recharge

Summary and future research opportunities

Integration of local, regional swc network (such as

Oklahoma Mesonet) with COSMOS, SMAP,

AirMOSS should provide new opportunity to

improve or build ecohydrological models