Documenting Soil Change using Dynamic Soil Properties and Ecological Site Descriptions

Skye Wills

NCSS, 2011

Soil and Ecosystem Change

• Soil Change Guide– Document change in soil function applicable

over the entire extent of a soil series or component phase

– When possible, Ecological Sites and associated State and Transition Models inform study design and interpretation

– Dynamic soil properties collected concurrently with vegetation properties

Space and Time

• Some conceptual model is needed to separate the soil component being evaluated into conditions that can be compared in space– Space for time substitution allows us to

interpret change over time or caused by management system

– Statistical inference: where can results be applied

Conceptual Model

• Ecological Site with State and Transition Model

Begay DSP Project (Utah)

• Used STM to separate ecological site (R035XY215UT) and the correlated soil map component phases into conditions for comparison– Reference State -Community Phase

• 1.1 Perennial grassland/shrubland

– Alternative State -Community Phase• 4.1 and 4.2 Cheatgrass Dominated/Monoculture

Sub-state

Bul

k de

nsity

(<

2mm

) g/

cm3 :0

-2 c

m

1.25

1.30

1.35

1.40

1.45

1.50

1.55

1.60

PG-S AG

Sub-state

Db

(<2m

m)

g/cm

3 : A

hor

izon

with

out

0-2

cm

1.35

1.40

1.45

1.50

1.55

1.60

PG-S AG

Sub-state

Db

(<2m

m)

g/cm

3 : B

hor

izon

to

25 c

m

1.46

1.48

1.50

1.52

1.54

1.56

1.58

1.60

PG-S AG

Bulk density

Sub-state

Org

anic

car

bon

%: 0

-2 c

m

0.3

0.4

0.5

0.6

0.7

0.8

PG-S AG

Sub-state

Org

anic

car

bon

%: A

hor

izon

with

out 0

-2 c

m

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

PG-S AG

Sub-state

Org

anic

car

bon

%: B

hor

izon

to 2

5 cm

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

PG-S AG

PG-S = perennial grass-shrub; AG = Annual grass (cheat grass) n=4

Organic carbon %

0-2

cm2

cm t

o ba

se o

f AB

to

25 c

m

High and low values of reference state

Org

anic

car

bon

%: 0

-2 c

m

0.3

0.4

0.5

0.6

0.7

0.8

PG-S AG

Conceptual Model

• Ecological Site with State and Transition Model• Add additional land uses – assume

these represent different states and that we understand the dynamics at work between these land uses.

MLRA 77C (TX)Amarillo DSP Project

• Chose conditions for study based on past and current land use– Rangeland – ‘Degraded’ shortgass, shrub

invaded (R077CY034TX; Shrub Dominant Community 3.1)

– Conservation Reserve Program – previously cropped, currently dominated by ungrazed introduced grasses

– Cropland –Irrigated conventionally tilled cotton

CRP – variable conditions and past management difficult to fit within STM concepts

Cropland – could conceivably be considered a separate state. However, the large energy inputs available could overwhelm any subtle ecological dynamics in the site.

Amarillo: Wet Aggregate Stability

  Mean Weight 

Diameter

Standard ErrorMean Weight 

Diameter

Mean Proportion  > 0.25 mm

Standard Error

 Proportion    > 0.25 mm

mm mm % %

Shrub (3.1) 4.81a* 0.25 0.84a 0.04

CRP 2.73b 0.22 0.55b 0.03

Crop 0.43c 0.22 0.14c 0.03

* Means with same letter are not significantly different (P=0.05)Ted Zobeck, personal communication 4/20/11

Conceptual Model

• Ecological Site with State and Transition Model• Add additional land uses – assume these represent

different states and that we understand the dynamics at work between these land uses.

• Chose to evaluate management systems within one land use– Pasture– Forest – Crop

Idaho Threebear project

• Chose to evaluate management conditions in forest land– Mature forest– Clear-cut and planted forest

Threebear Results

MLRA 106 (NE and KS): Kennebec Soil

• Chose to evaluate management systems within cropland– Generally, corn/soybean rotation with

• Conventional tillage system• No-till system• “organic” system

– While this sounds like a straightforward comparison there are many variations of each of these management systems. Deciding what to compare and what to include in each was a major difficulty.

Kennebec Results%

WA

S

To

tal C

sto

cks

(Mg

ha-1

to

40cm

)

Using ESDs to Interpret Soil Change

• An ESD and particularly the state and transition model provide context for making management recommendations and interpretations

• It also segments a soil map unit component phase into conditions relevant for management– That is – this component with the same

community phase present will likely have the same properties and respond to management in the same way

Using ESDs to Interpret Soil Change

• Begay Project – the STM supplies contextual information about the ecological dynamics of the site

• Amarillo Project – While the STM provides information about range and CRP land – it doesn’t tell us how broadly we can apply the results from the cropland or what processes are important for maintaining or restoring ecosystem function

Ongoing Projects• MLRA 133A (GA)Tifton – Longleaf

Pine/Wiregrass vs. Pasture – Data collection being done concurrently with

ecological site data collection– Presents challenges …………but should allow

us to interpret and infer ecosystem change• MLRA 80A (OK and KS) Kirkland –

Claypan Prairie Rangeland vs. Cropland– Conventional and no-till management

systems within cropland land use will be sampled

Acknowledgements

• Arlene Tugel• Cindy Stiles• Ted Zobeck• Laurie Kiniry• Craig Bird• Gerald Crenwelgie

• Dave Kohake• Bruce Evans• Judy Ward• Brian Gardner