1. Influence of dominant shrub species on exoenzyme activity in desert shrubland
Kathleen A. Roman1, Eleanor S. Keats2, Anthony Darrouzet-Nardi1, Jennie R. McLaren1
1 University of Texas at El Paso, 2 Earlham College
 The Chihuahuan desert has been transforming from a
desert grassland to desert shrubland for the past century
 Changing plant composition may also influence
biogeochemical cycling in these systems because of
species specific influences on soil properties
Exoenzyme Activity
Acknowledgments
A Changing Desert
Question:
Are there differences in soils under dominant shrub
species and bare soil in the activity rate of exoenzymes
involved in carbon, nitrogen, and phosphorus acquisition?
Our Approach
 Soil samples were taken from underneath
creosote shrubs, mesquite shrubs, and
unvegetated areas (n=8 for each)
 We examined exoenzyme activity for six
enzymes:
1. Phosphorous acquiring:
i. Phos (acid phosphatase)
2. Carbon acquiring:
ii. β-gluc (β-1,4-glucosidase)
iii.α-gluc (α-1,4-glucosidase)
iv.β-xyl (β-1,4-xylosidase)
v. β-cell (β-D-1,4-cellobiosidase)
3. Nitrogen acquiring:
vi.NAG (β-1,4-N-acetyl-
glucosaminidase)
 Samples were taken once a week for five
weeks during summer 2015
NSF Chihuahuan Desert Biodiversity-REU, UTEP Department of
Biology, Jornada Basin LTER, COURI
Jornada LTER
From top left clockwise:
Bare soil
Creosote (Larrea Tridentata)
Mesquite (Prosopis glandulosa)
What We Found
 Unvegetated soil maintained the
lowest enzyme activity
throughout the five weeks
Lack of vegetation in the soil
inhibits microbial activity
 Creosote soil enzyme activity
remained between mesquite and
bare soil
 Mesquite soil consistently had
the highest enzyme activity for
every exoenzyme
The fact that mesquite is a N-fixer
could contribute to its larger
impact on soil processes
Future Directions
 Comparing shrub effects on soil
processes with that of plants in
grassland desert will give evidence of
the effects of this landscape change
Sources:
Jornada LTER Map Retrieved from
http://jornada.nmsu.edu/files/chihua3.gif
Collecting various soil cores in
the Jornada
Collecting a soil sample from
under a creosote shrub
P-acquiring C-acquiring
C-acquiring C-acquiring
C-acquiring N-acquiring