1. Comparison of Soil Organic Carbon Stocks Between
Residential Turf Grass & Native Soil
Acknowledge Dussita
Richard V. Pouyat, Ian D. Yesilonis, and Nancy E. Golubiewski

2. Residential: 40% of urban areas (Nowak et al. 1996)
40 million acres of lawn in conterminous USA (Milesi et al., 2005)
3 times more than acreage of largest irrigated crop (corn)
Lawns make up largest component of most urban landscapes, especially residential areas.
Read bullets
Many articles / discussions about benefits and potential environmental effects of turf grass. From an ecological perspective, low diversity, require maintenance (i.e., use of fossil fuels and other resources), replace more quality habitats
Others see turf grass as a good ground cover that prevents erosion, provides recreational space, and is aesthetically pleasing to look at. And more recently, biological virtues that include potential to sequester C in soil and retain N

3. LIFE ZONE
AREA (x10
AREA (x10 12 12 m m 2 2 ) )
C Density (kg m
C Density (kg m 2 2
) Soil C (x10
) Soil C (x10 15 15 g) g)
Temperate forest
Temperate forest - -
warm
warm
8.6
7.1
7.1
61.1
Temperate forest - -
cool
3.4
12.7
43.2
Cool temperate steppe
9.0
13.3
119.7
Temperate thorn steppe
3.9
7.6
29.6
Warm desert
14.0
1.4
19.6
Wetlands
2.8
72.3
202.4
Boreal forest - -
wet
6.9
19.3
133.2
Cultivated land
21.2
7.9
167.5
Due to differences in sensitivity between decay rates and NPP, get a wide variation is soil C densities.
Prior to widespread human modifications, net increase in soil C is estimated at % per yr. (Mostly in peatlands! Otherwise, inputs and outputs of soil C are closely balanced)
If we compare turf grass with other ecosystems in their capacity to accumulate C in soil, the data so far suggest lawns have a high capacity to sequester C in soil. Comparable to cool temperate steppe. If consider entire urban landscape, more comparable with temperate thorn steppe.
Residential turf grass ?
14.4 ?
Urban land
1.3 +
7.7
10.0
TOTAL WORLD
1500(±20%)
Adapted from Post et al. (1982) and Schlesinger and Andrews (2000)
*Milesi et al. 2005

4. SIMILARITY? Baltimore Phoenix
What I find interesting is that urban landscapes, due to human desires and subsequent efforts, often look more similar in vegetation structure than the systems they replaced. In this case, comparing Baltimore and Phoenix metro regions to the right. Native Phoenix landscape is a warm dessert that is characterized by very low stocks of above and below ground C storage. Add people—get increase in both stocks

5. URBAN LAND USE CHANGE?: Disturbance (initial, post-develop.)- SOC
Introduction of impervious surfaces
SOC- low, very slow change
Introduction of horticultural management (supplements)- SOC
Environmental change (biophysical)- SOC
If we consider potential impacts of urban land use change on SOC stocks, find that most changes result in a loss of C; however, with the introduction of management (mostly supplements of water and nutrients) potential to increase productivity and thus organic matter inputs into the soil.

6. TURFGRASS MAINTENANCE
$10.4 billion in USA
Range of fertilizer rates:
Golf courses, athletic fields—490 kg ha-1 yr-1
Residential lawns— kg ha-1 yr-1
16 million kg pesticides applied yr-1 (Aspelin, 1997)
Irrigation use?
And American population is willing and able to spend lots of money to maintain turf grass—in fact, Melesi et al. 2005, calculated that the vast majority of land area in conterminous US requires supplements to maintain grass except in north central and eastern US.

7. Cd Turf grass? 20 Agricultural Conversion Urban Conversion
Boreal
Cool Temperate Steppe
Cool Tropical Forest
Moist Tropical Forest
Warm Temperate Forest
Warm Desert 20
Agricultural Conversion
Urban Conversion Cd
Urban Range at Equilibrium
Global Range at Equilibrium
This desire to maintain turf grass, trees and other horticultural plantings regardless of climate results in what has been called an “ecosystem convergence”. Range in ecosystem attributes gets reduced due to human supplements and other activities. In the case of SOC, turf grass is an important component of a “convergence.”
1.4
Time
Edaphic Cultivation Urban
Turf grass?
Milesi et al., 2005
Pouyat et al. (2001) & Pouyat et al. (2003)

8. OBJECTIVES:
Compare residential turf grass vs. native SOC in Baltimore, MD and Denver, CO areas
Climatologically distinct regions
Compare residential turf grass vs. native cover types (0.2 and 1 m depth)
Field collected data, NRCS Soil database, and data from literature
To test this idea, we . . .

9. Estimate net effect of urban land-use change on SOC densities in both metropolitan areas
Calculate SOC densities on area weight basis (including impervious areas)
Pre-urban, agriculture, and post-urban landscapes

10. EXPECTED RESULTS:
SOC densities of native soils will differ more than for residential soils
2. Net differences between pre- and post-urban SOC densities will be positive in arid shortgrass steppe (Denver) and negative in mid-Atlantic hardwood deciduous forest (Baltimore)

11. NRCS Soil Characterization Database
1 m DEPTH SOIL CORES
NRCS Soil Characterization Database
605 pedons northeastern and north central USA
Data required (bulk density, coarse fragments, C fraction, horizon thickness)
0-20 cm, 0-1 m, proportion of C to 1 m depth occurring in surface 20 cm
Extrapolated to 1 m only if reached C horizon

12. BALTIMORE UFORE PLOTS
Birdsey (1992)
n=19
n=19
n=5
n=7
NRCS DATA

13. CUB HILL PLOTS
Birdsey (1992)
n=7
n=8
n=6

14. DENVER METROPOLITAN AREA
Schimel et al. (1985)
NRCS
Adapted from Galubiewski (2006)

15. COMPARISON OF RESIDENTIAL AREAS

16. COMPARISON OF NATIVE SOILS?
n=7
n=19

17. NET Change? Denver Baltimore (kg m-2) Pre-agriculture 7.3 11.2 (6.7)
Denver
Baltimore
(kg m-2)
Pre-agriculture
7.3
11.2 (6.7)
Agriculture
~2.5
5.4
Urban*
8.5
7.1
+1.17
-4.1 (+2.6)
*includes impervious surfaces (3.3 kg m-2)

18. CONCLUSIONS
Residential soils differ less than native soils in SOC densities
Residential soils in Denver significantly higher than native short grass (Baltimore less clear)
Net change Denver (increase SOC), Baltimore (+ or – change?)
Turf grass potential to sequester C in soil (BUT, entire budget required)

19. (x10 (x10 m2) (kg m (kg m ) ) (x10 (x10 g) g) - - LIFE ZONE LIFE ZONE
AREA C Density Soil
AREA C Density Soil C C
(x10
(x10 10 10
m2)
(kg m
(kg m - - 2 2 ) )
(x10
(x10 14 14 g) g)
Northeast Forest*
Northeast Forest*
20.81
16.2
16.2
33.7
Northeast Cropland*
Northeast Cropland* - -
6.0
6.0 - -
Mid
Mid - -
Atlantic Forest*
Atlantic Forest*
20.29
20.29
11.2
11.2
22.7
Mid
Mid - -
Atlantic
Atlantic
Cropland*
Cropland* - -
4.2
4.2 - -
Southeast
Forest*
34.22
7.7
26.3
Southeast
Cropland* -
2.6 -
Urban (residential)
6.35
6.35
14.4 (
1.2)
1.2)
9.84
9.84
USA Urban (total)
USA Urban (total)
30.06**
30.06
7.7 (±0.2)***
23.15
USA (total)
USA (total)
915.9
915.9
6.8 (?)
6.8 (?)
619.15 * *
Birdsey
Birdsey
(1992)
(1992)
***Pouyat et al. (2006)
**Nowak et al. (1996)