Landscape-soil interactions in the Chihuahuan desert

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Landscape-soil interactions in the Chihuahuan
desert

• Brian Murtaugh
• Meredith Albright
• Soils Geography
• November 6, 2007
• Univ of Colorado, Boulder

http//museum.utep.edu/chih/NHCD/images/desertview
.jpg
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Introduction

• Located in Chihuahuan Desert
• 60 km apart
• Sevilleta
• 250 mm annual precipitation
• Moisture deficit most of the year
• Low 1.6 C
• High 25.1 C
• Jornada
• 250 mm annual precipitation
• Low 5 C
• High 25 C

SEV
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Desertification and Soil

• Jornada Basin
• New Mexico, USA

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Site
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Desertification
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5 Major Ecosystem Types

• Grasslands
• Black grama
• Playa
• Shrublands
• Creosotebush
• Honey mesquite
• Tarbush

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Grasslands

• Little bare soil
• Even soil dispersal
• Being overtaken

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Black grama grasslands

• Sandy/gravely sites
• Deep loam
• CaCO3
• Relatively higher moisture content

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Playa grasslands

• Low-lying
• Clayey soils
• Consistent texture

Burrograss
Tobosa
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Shrublands

• Vegetation spread out
• Nutrient islands
• Slowly take over grasses

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Creosotebush

• Locations vary
• Soils vary
• Little difference in soil moisture
• Produce compounds that influence other growth

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Honey mesquite

• Deciduous shrubs
• Deep roots
• Most soil types

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Tarbush shrublands

• Deciduous
• Clay-loam soils
• Might receive run-in water
• Use deeper water

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Climate and Soil

• Soil profiles hold evidence of past
• Clay mineralogy
• Carbonates

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Carbonates

• Illuvial
• Tell age of horizon
• Grasses -gt C4
• Shrubs -gt C3
• C4 dominates

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Future Research

• Soil moisture content, texture, vegetation type
• Ecosystem dynamics

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Takehome from Jornada

• Grasslands overrun by shrublands
• Carbonates tell history of region
• Low variance of soil types
• Soil moisture changes throughout site

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Sevilleta National Wildlife Refuge

• 80 km south of Albuquerque
• Importance of site
• Ecotones
• Focus Chihuahuan desert grassland to shrubland

http//sev.lternet.edu
Google Earth
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Grama-dominated grassland

• Invasion of creosotebush
• (Larrea tridentata) into grasslands
• Potential causes climate change, increased
  rodent activity, altered fire frequency, land-use
  changes, shift in groundwater levels
• Changes in species composition
• Changes in surface soil
• How do soils change with the transition from
  grasslands to shrublands?
• Soil profile
• Texture
• Nutrients

http//sev.lternet.edu/
Creosotebush
http//sev.lternet.edu/
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Distribution of Vegetation
Grassland

• Grassland to shrubland
• Decreased biomass
• Decreased soil coverage
• Affects soil characteristics
• Soil profile
• Texture
• Nutrient levels

Shrubland
(Cross and Schlesinger, 1999)
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Soil Profile
Grassland

• Grassland
• Argillic horizon over a CaCO3 horizon
• Shrubland
• Patchy erosion of argillic horizon
• Under shrubs - relics
• Between shrubs exposure of CaCO3
• Positive Feedback

Inhibits grass establishment
Shrubland
(Kieft et al., 1998)
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Nutrients

• Essential nutrients (N, K, organic C)
• More highly concentrated under shrubs
• Microbial microsites (greater moisture and OM)
• Positive feedback

Increased nutrient cycling
(Kieft et al., 1998)
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Texture

• Soil Texture
• Grassland
• uniform texture
• 83 sand, 8 silt, 9 clay
• Shrubland
• Heterogeneous
• 64 sand , 26 silt, 10 clay
• Consequences
• Under shrubs
• Higher water holding capacity
• Increased CEC
• Positive feedback

Deposition of fine particles
(Kieft et al., 1998)
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Conclusions

• Positive feedback towards shrublands
• Patchy distribution of fine-textured soils
• Loss of the argillic layer between shrubs
• Patchy distribution of essential nutrients
• Shrubland encroachment is widespread
• Creation of islands of fertility in Sevilleta and
  Jornada
• Characteristic soil qualities under grasses vs.
  shrublands in both sites

http//www.nsf.gov/news/mmg/media/images/eco4_f.jp
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References - Sevilleta

• Kieft, T.L., C.S. White, S.R. Loftin, R. Aguilar,
  J.A. Craig, D.A. Skaar. 1998. Temporal Dynamics
  in soil carbon and nitrogen resources at a
  grassland-shrubland ecotone. Ecology 79(2)
  671-683.
• Cross, A.F., W.H. Schlesinger. 1999. Plant
  regulation of soil nutrient distribution in the
  northern Chihuahuan Desert. Plant Ecology 145
  11-25.
• White, C.S., D.I. Moore, J.A. Craig. 2004.
  Regional-scale drought increases potential soil
  fertility in semi-arid grasslands. Biology and
  Fertility of Soils 40 73-78.
• Schlesinger, W.H., J.A. Raikes, A.E. Hartley,
  A.F. Cross. 1996. On the spatial pattern of
  soil nutrients in desert ecosystems. Ecology
  77 364-374.
• Kurc, S.A., E.E. Small. 2007. Soil moisture
  variations and ecosystem-scale fluxes of water
  and carbon in semiarid grassland and shrubland.
  Water resources research 43 1-13.
• Long Term Ecological Research, Sevilleta.
  http//sev.lternet.edu/
• Brady, N.C., R.R. Weil. The Nature and Properties
  of Soils. Pearson Prentice Hall, 2008.
• Buxbaum, C.A.Z., K. Vanderbuilt. 2007. Soil
  Heterogeneity and the distribution of desert and
  steppe plant species across a desert-grassland
  ecotone. Journal of Arid Environment 69 617-632.

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References - Jornada

• Havstad, Kris M., L.F. Huenneke, William H.
  Schlesinger (Eds.), Debra P.C. Peters, Robert P.
  Gibbens, Structure and Function of a Chihuahuan
  Desert Ecosystem The Jornada Basin Long-Term
  Ecological Research Site,Oxford University
  Press 2006