consequences of stand age and structure on forest water yield

Consequences Of Stand Age And Structure On Forest Water Yield

Chelcy Ford Miniat, Pete V. Caldwell, A. Chris Oishi, Katherine ElliottUSDA Forest Service, SRS, Coweeta Hydrologic Lab, Otto, NC

Steven T. BrantleyJoseph W. Jones Ecological Research Center, Newton, GA

Kim A. NovickUniversity of Indiana, School of Public and Environmental Affairs, Bloomington, IN

Paul V. BolstadUniversity of Minnesota, College of Food, Agriculture and Natural Resource Sciences,

Department of Forest Resources, St. Paul, MN

USDA FS SRS

USDA FS SRSCaldwell et al., 2014

• 81% Forested (24% Nat’l Forest)• 23 billion m3/yr• 588 intakes• 336 communities• 10.7 million served

(4.9 M get >20%)

The southern Appalachians: Headwaters for drinking water supply

EPA SDWIS; WaSSI model output

Leuzinger and Korner 2010, GCBLabat et al. 2004, AWRGedney et al. 2006, Nature

Large-scale patterns in streamflow

Simple Water Balance

Input (Pre)– Output (Ro)= Loss (ET)

Surface water supplies are increasingly vulnerable to drought.

Rainfall distribution is the main driver of runoff under future warmer, higher CO2 world in a temperate deciduous forest.

River discharge across the globe has been increasing at a rate of 2% for each 0.5°C increase in global temperature.

USDA FS SRS

Post-1960 trend

Attribution of Post-1960 trend in ET

Local patterns in streamflow

Locally in the southern Appalachians, we see the opposite of the global and N. American trend.

Discharge in reference watersheds at Coweeta Hydrologic Lab has been decreasing at a rate of 1.3% for each 0.5°C increase in temperature.

USDA FS SRS

Ford et al., 2011

Hypotheses

USDA FS SRS

Over time water yield (Q) in unmanaged forests of the southern Appalachians has decreased

Both climate (precipitation and potential ET) and species changes in evapotranspiration (ET) have contributed to the decline

Coweeta Basin

N

• Established 1934• 1626 ha Basin

Coweeta Basin

N

• Established 1934• 1626 ha Basin• 16 active weirs

Coweeta Basin

N

• Established 1934• 1626 ha Basin• 16 active weirs• 5 climate stations

Coweeta Basin

N

• Established 1934• 1626 ha Basin• 16 active weirs• 5 climate stations• 10 rain gauges

Coweeta Basin

N

• Established 1934• 1626 ha Basin• 16 active weirs• 5 climate stations• 10 rain gauges• 676 vegetation plots

Elliott and Vose 2011

Changing forest species composition

USDA FS SRS

Major Forest Disturbances

Elm

Spa

nwor

m (1

961)

Hurr

ican

es F

ranc

is &

Ivan

(200

4)

Maj

or F

lood

(196

4)

Fall

Cank

erw

orm

(196

9-19

77)

Maj

or D

roug

ht (1

984-

1988

) SPB

and

Oak

Mor

talit

y

Hem

lock

Woo

lly A

delg

id (2

003-

pres

ent)

Hurr

ican

e O

pal (

1995

)

1900 1950 2000

Drou

ght (

1999

-200

1) SP

B m

orta

lity

1850

Ches

tnut

blig

ht (1

928-

1938

)

Logg

ing

(late

180

0s-1

920s

)

Hom

este

ads a

nd G

razin

gN

ative

Am

eric

an u

se o

f Fire

Hurr

ican

e (1

835)

Drou

ght (

2006

-200

8)

USDA FS SRS

Control Watersheds at Coweeta

USDA FS SRS

Quantifying changes in annual Q

AutoRegressive Integrated Moving AverageTime Series Modeling

• Can account for:• autocorrelation (memory)• transfer functions can combine independent

series (e.g., Q~P, PET) • external perturbations affecting the time series

(interventions, e.g., species data)

• Akaike’s Information Criterion (AIC) for model selection

USDA FS SRS

Q has changed in low elevation watersheds

Low elevation High elevation

• For WS14 and WS18, Q decrease began in 1974, declined by 22% or 64mm/decade

Hypotheses

Over time water yield (Q) in unmanaged forests of the southern Appalachians has decreased

Both climate (precipitation and potential ET) and species changes in evapotranspiration (ET) have contributed to the decline

USDA FS SRS

Precipitation has not changed

Change in P 1938-1946+373 mm/decade (p=0.0835) Checking standard rain

gauge at CS01 (1952)

USDA FS SRS

PET has increased in recent years

USDA FS SRS

1938-1949-50 mm/decade

p=0.0463

1997-2013+46 mm/decade

p=0.0023

CS01 Evaporation Pan:Measured daily since 1936

ET initially declined, but has increased markedly since the 1980s


• Increase began in 1980-1999, increasing by 37-93 mm/decade

Elliott and Vose 2011

Changing forest species composition

USDA FS SRS

Water use varies by species

Ford et al., 2011; Vose and Ford, 2011

Diffuse porous and tracheid xylem

Ring porous xylem

Red mapleTulip poplarWhite pineHemlock

Red oakChestnut oak

Semi-ring porous xylem Hickory

Disturbance has shifted tree abundance and composition

• Residuals from a model predicting Q as a function of climate only (P and PET)

Climate can explain some of the changes in Q, but not all


• Residuals from a model predicting Q as a function of climate only (P and PET)

• Residuals from a model predicting Q as a function of climate (P and PET) and species change


These changes in forest structure and species composition may have decreased water yield by as much as 18% in a given year since the mid-1970s after accounting for climate.

Summary

• There have been changes in water yield (Q) in unmanaged forests of the southern Appalachians• Q increased 30-55% in low elevation watersheds from 1938-1970s• Q decreased 22% from early 1970s to 2013 in some low elevation

watersheds

• There have been changes in P and PET that explain some the changes in Q and ET

• Changes in forest species composition and structure also played a role on Q and ET• Significant interventions indicate changes in Q by up to 10%• Canopy interception increases with age• Shift to dominance of diffuse porous species

USGS gauge 03500000, Little Tennessee River at PrentissReference gage

How widespread are these changes?

Departures from 1960-1980 line of fit

USDA FS SRS

Caldwell et al., in prep

Dr. Steven Brantley, AFRI project post-doc, now permanent Eco-hydrologist at Joseph W. Jones Ecological Research Center

Training, Mentoring and Products

Changes in interception with forest age

USDA FS SRS

Brantley et al., in prep

This AFRI project has successfully trained and mentored 3 post-doctoral research scientists, 2 graduate students, and 1 undergraduate student

Brantley, S. T., M. Schulte, P. V. Bolstad, and C. F. Miniat. 2016. Equations for estimating biomass, foliage area and sapwood of small trees in the southern Appalachians. Forest Science 62: 414–421

Equations for estimating structural characteristics of mid-canopy trees and shrubs in the Southern Appalachians.

USDA FS SRS

Ms. Morgan Schulte, AFRI project undergraduate student

Dr. Kim Novick, FS/AFRI project post-doc, now faculty at University of Indiana Bloomington

USDA FS SRS

Novick, K. A., et al. (2013). Eddy covariance measurements with a new fast-response, enclosed-path analyzer: Spectral characteristics and cross-system comparisons. Ag For Met, 181, 17-32.

Novick, K., Brantley, S., Miniat, C. F., Walker, J., & Vose, J. M. (2014). Inferring the contribution of advection to total ecosystem scalar fluxes over a tall forest in complex terrain. Ag For Met, 185, 1-13.

Dr. Chris Oishi, AFRI project post-doc, now permanent Ecologist with USDA Forest Service Coweeta Hydrologic Lab

ET flux from canopy and subcanopy across forest

ages forest age

USDA FS SRSOishi et al., in prep

Benson, M., Oishi, A.C., Miniat, C.F., Domec, J.-C., and Novick, K.A. “Climate and age influence on drought-induced cavitation vulnerability in eastern deciduous forests”Oral presentation, Ecological Society of America Annual Meeting Ft. Lauderdale, FL. August 7-12, 2016. Poster presentation, AmeriFlux Annual Meeting, Golden, Colorado, September 21-23, 2016

Safety Margin (P50 - ΨL)across chronosequence:

• LITU – juvenile stands in more mesic site are at highest risk for drought induced mortality.

• QUAL – mature species in more mesic site are at the highest risk for drought induced mortality

Mr. Michael Benson, AFRI project undergraduate, now a MS student with Novick at IU

Oishi, A.C., et al. "Baseliner: An open-source, interactive tool for processing sap flux data from thermal dissipation probes." SoftwareX (2016).

Dehnam, S.O., Oishi, A.C., Miniat, C.F., Brantley, S.T., Novick, K.A. “Tree water use dynamics across different sites and age classes in the Southern Appalachians”. Poster presentation, Ecological Society of America, Annual Meeting Ft. Lauderdale, FL. August 7-12, 2016.

Ms. Sander Denham, AFRI project post-MS student, now a PhD student with Novick at IU

USDA FS SRS

Special thanks to Chris Sobek, Charles Marshall, Neal Muldoon, and all scientists, technicians and students who have contributed to the long-term

dataset.

This project was supported by:

Agriculture and Food Research Initiative Competitive Grant number 2012-67019-19484 from the USDA National Institute of Food and

Agriculture

USDA FS SRS

USFS/UMN cooperative agreement (agreement #12-CS-11330140-128)

Acknowledgements