Ecohydrological Niche of Big Sagebrush (Artemisia Tridentata) Shrubland/Steppe and of Its

Bradford and others Ecohydrology in adjacent sagebrush lodgepole-pine ecosystems

Appendix 3. Validation of Sagebrush Ecosystems Representation in SOILWAT

SOILWAT, a daily time step soil water simulation model, was developed and tested in the semiarid western US shortgrass steppe and previously used in shrublands . We compared SOILWAT model output with measured field data from the literature that met the following criteria: water balance measurement data is available and accompanied with a detailed soil and site description. Unfortunately, only a study with a sagebrush-grass site from southwestern Idaho, Reynolds Creek Experimental Watershed met enough criteria for a comparison. The site is a good representation of the median of sagebrush ecosystems, for example, soils are loam and MAP is 349 mm (compare Table 1). We ran SOILWAT using climate and soils inputs appropriate for Reynolds Creek, as detailed in . This procedure omitted information on local conditions (for example, weather station and soil profiles) and potentially causes worse than possible predictions; meanwhile, it guarantees comparability with the simulation results.

SOILWAT estimates of average daily volumetric soil water content are comparable with measured values (Figure A3.1). SOILWAT estimates of actual evapotranspiration (AET) described the pattern of inter- and intra-annual dynamics (Figure A3.2). The different measurements and simulations of

AET reported by Wight and others show a variability both in timing and size of mid-summer peak of

AET. SOILWAT predicted values for mid-summer peak of AET in the range of the published spread. A second late-season peak in AET is well captured by SOILWAT. The dynamics of transpiration were also well described by SOILWAT (Figure A3.3). Both in 1978 and 1979, published transpiration values were comparable to SOILWAT simulations, but in 1977, SOILWAT simulated smaller transpiration values.

The discrepancy in the year 1977 could be explained by precipitation inputs being derived from the gridded dataset compared to on-site measurements by Wight and others . We conclude that the proposed representation of sagebrush ecosystems in SOILWAT using the described data sources is realistic.

1 Bradford and others Ecohydrology in adjacent sagebrush lodgepole-pine ecosystems 3 0 T m i n ( C ) T m a x ( C ) 2 5 ) C (

e 2 0 r u t a r

e 1 5 p m e t

i 1 0 a

y l i a

Figure A3.1. Comparison between measured (black) − 5 and SOILWAT modeled (red) average daily volumetric 0 . 5 3 . 6− 6 . 6 c m ) )

0 . 4 m m m / (

m n soil water content (VWC) over 12 years (1999 to 2011) (

o i r t

e a t n

0 . 3 t i a a p e w i

l c i m e o r y l s i P for the Reynolds Creek Experimental Watershed in a c i n

r 0 . 2 D t a e 1 0 e m m

u l y l i o v 0 . 1 a southwestern Idaho. VWC was measured and modeled 5 D at 5 depths (bottom 5 panels). Shaded areas around the 0 . 0 0 0 . 5 lines are 1SD. 8 . 7− 1 1 . 7 c m )

) 0 . 4 m m / m ( m

e i t t n 0 . 3 a a Also included for comparison are mean daily maximum a r t e w l

i l f i m

n o I y

n a c i a

r 0 . 2 D 1 0 t e e and minimum temperature (top panel), precipitation m

m y l u i l a o v 0 . 1 5 D (blue; second panel), infiltration (light blue; second 0 . 0 0 panel), snow water equivalent (measured and modeled 0 . 5 1 8 . 8− 2 1 . 8 c m

) 0 . 4 m ) in blue and purple, respectively; third panel), and / m m ( m r (

e t n 0 . 3 E a a W e w

2 0 0 number of years of observations for each day of year o n y s l a i

e a c i

r 0 . 2 m D t

e y l i m a u l D

(gray; fourth panel). o 1 0 0 v 0 . 1

0 . 0 0

4 9 . 3− 5 2 . 3 c m

) 0 . 4

h m c e i / l h b m a w l

a o r f v

t r n e

0 . 3 a r a a e a

s f l n o i m

i r o t e y a l s b i v

r m c a e i u s r

0 . 2 n D b t 2 0 o e m u C m m i W u n l V i o M v 0 . 1 1 0

0 . 0 0

0 . 5 O b s : V W C S o i l W a t : V W C 1 0 0 . 1 1 0 3 . 1 c m − S o i l W a t : P r e c i p i t a t i o n S o i l W a t : I n f i l t r a t i o n

) 0 . 4

m S o i l W a t : S W E /

m O b s : S W E (

e t n 0 . 3 a a e w

o y l s i

r 0 . 2 D t e m u l o v 0 . 1

0 . 0 2 1 2 9 5 7 8 5 1 1 3 1 4 1 1 6 9 1 9 7 2 2 5 2 5 3 2 8 1 3 0 9 3 3 7 3 6 5 T i m e ( D a y o f y e a r ) T i m e ( d a y s o f y e a r ) Bradford and others Ecohydrology in adjacent sagebrush lodgepole-pine ecosystems

Figure A3.2. Comparison between evapotranspiration (ET) in the years 1977 to 1979 simulated by SOILWAT for the Reynolds Creek Experimental Watershed in southwestern Idaho and ET data measured (Lysimeter, Water Balance), simulated (SPAW, CREAMS, ERHYM) and averaged .

3 Bradford and others Ecohydrology in adjacent sagebrush lodgepole-pine ecosystems

Figure A3.3. Comparison between transpiration in the years 1977 to 1979 simulated by SOILWAT for the Reynolds Creek Experimental Watershed in southwestern Idaho and data simulated (SPAW, CREAMS, ERHYM) from Wight and others .

4 Bradford and others Ecohydrology in adjacent sagebrush lodgepole-pine ecosystems

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