The University of Arizona

Decomposition in Drylands: Soil Erosion and UV Interactions

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Death is an integral part of the cycle of life.  In ecosystems, plants acquire inorganic compounds from their environment (carbon, nitrogen, phosphorus, etc.) and build them into complex organic compounds that nourish animals either directly (e,g,, herbivores than consume plants) or indirectly (carnivores that consume herbivores). Eventually, all plants and animals in the ecosystem die.  What is the fate of the nutrients they have accumulated during their life-time? These nutrients are released back to the environment vial the process of ‘decomposition'.  Decomposition, the breakdown of dead plant and animal material, is a fundamental ecosystem process that affects long-term soil fertility and carbon storage. Most of what is known about decomposition is from studies in high rainfall areas, but this knowledge does not translate well to dryland ecosystems.  Some recent studies suggest solar ultra-violet radiation is a major driver of decomposition in drylands; however, other studies indicate the level of mixing of wind/water-transported soils with litter is the key factor.

 

A $1.1M grant from the National Science Foundation, entitled "Decomposition in drylands: Soil erosion and UV interactions", seeks to resolve these competing explanations. A collaborative effort initiated in 2008 involves scientists in the School of Natural Resources and the Environment at the University of Arizona (Steve Archer and Dave Breshears) , New Mexico State University (Heather Throop), the University of Kentucky (Rebecca McCulley) and Loyola University (Paul Barnes).  Field experiments at the Santa Rita Experimental Range and complimentary controlled environment studies will be used to ascertain how light energy-soil movement interact to affect decomposition rates in the context of woody plant encroachment into grasslands, a globally extensive vegetation change in drylands. The research is expected to yield new insights into processes that affect soil fertility and carbon storage in drylands by combining the disciplines of plant community ecology, ecosystem science and earth science in a novel framework. The findings will be relevant nationally and internationally, as dryland ecosystems characterize major portions of the US and global land area, and may be significant carbon sinks. The study will provide training opportunities for four graduate students and numerous undergraduates.

 

Many interacting drivers potentially influence decomposition. We propose to extend research on traditional decomposition drivers to include erosion-based drivers, and test the notion that development of the litter/soil matrix is a key but overlooked component of dryland decomposition. We hypothesize this matrix is controlled by wind/water transport of soil which, in turn, is controlled by vegetation structure. We further hypothesize that as the litter/soil matrix develops, key biotic (microbial activity) and abiotic forces (moisture, UV photodegradation) are mediated. 

 

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Posters:

 

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Presentations:

 

-2008-

Abbene ML, Barnes PW, Throop HL, Archer S. 2008. Interactive effects of UV radiation and soil coverage on leaf litter decomposition in velvet mesquite (Prosopis velutina). In Ecological Society of America Annual Meetings. Milwaukee,WI.

 

Throop, H. L., and S. Archer. 2008. Shrub encroachment, land management and litter decomposition. 5th Annual Research Insights in Semiarid Ecosystems (RISE) Symposium, Tucson, AZ

 

Throop, H., S. Archer, P. W. Barnes, M. L. Abbene, D. Hewin, and G. Okin. 2008. Addressing the dryland decomposition conundrum by integrating vegetation structure, soil transport and UV photodegradation. LTER Cross-Site Comparison Symposium, Albuquerque, NM.


-2009-
Hewins DB, HL Throop, SR Archer, GS Okin. 2009. Soil-litter mixing enhances decomposition rates in a Chihuahuan Desert grassland. Ecological Society of America Annual Meetings, Albuquerque, NM (poster)

 

Throop, H, Archer, S, Barnes, P. 2009. Addressing the dryland decomposition conundrum by integrating vegetation structure, soil transport, and UV photodegradation. Organized oral session: “What's New Under the Sun? Photodegradation and Novel Drivers of Decomposition in Dryland Ecosystems.” Ecological Society of America Annual Meetings, Albuquerque, NM. Talk.

 

Field, J.P., D.D. Breshears, C.B. Zou, and J.J. Whicker.2009. Wind and water erosion under global-change-type conditions and alternate land management practices. Ecological Society of America Annual Meetings, Albuquerque, New Mexico. Talk.

 

Breshears, D.D, J.P. Field, J.J. Whicker, S. Ravi, T.E. Huxman, P. D'Odorico, C.B. Zou. 2009. Toward a more holistic perspective of wind and water erosion within ecohydrology. AGU Chapman Conference "Examining Ecohydrological Feedbacks of Landscape Change Along Elevation Gradients in Semiarid Regions". Boise/Sun Valley, Idaho. Poster.

 

Moore, D., T.H. Melhem, J.P. Field, D.D Breshears, and S.R. Archer. Microclimate variation around individual shrubs and shrub clusters in semiarid ecosystems. University of Arizona Annual iPlant Teacher Fellowship Symposium. 10 July 2009. Tucson, Arizona.

  
-2010-
Field, J.P., D.D. Breshears, C.B. Zou, J.J. Whicker.2010. Aeolian and fluvial sediment fluxes under climatic extremes and land use change. International Conference of Aeolian Research (ICAR VII). Santa Rosa, Argentina. Poster.


Breshears D.D, T.B. Kirchner, J.J. Whicker, J.P. Field. 2010. Modeling omnidirectional aeolian horizontal sediment transport during succession and with disturbance: implications for contaminants. International Conference of Aeolian Research (ICAR VII). Santa Rosa, Argentina. Poster.


Luis M.M, J.P. Field, J.C. Villegas, J.J. Whicker, D.D. Breshears, D.J. Law, A.M. Urgeghe. 2010. Characterizing Regional and Local Aerosol Components Associated with Wind Erosion Following Grassland Fire. Ecological Society of America Annual Meetings, Pittsburg, Pennsylvania. Poster.


Field, J.P., D.D. Breshears, J.J. Whicker, and C.B. Zou. 2010. Wind and water sediment transport under climate extremes and land management practices. Research Insights in Semiarid Ecosystems (RISE) Symposium. University of Arizona Tucson, Arizona. Invited Talk.

 

Power, R.C., T.H. Melhem, J.P. Field, D.D Breshears, and S.R. Archer. Wind and water-driven resource redistribution at the vegetation-patch scale in a semiarid shrubland: Characterizing rates of soil-litter mixing. Seventh Annual Research Insights in Semiarid Ecosystems (RISE) Symposium. 2 October 2010. Tucson, Arizona. 

 

Power, R.C., T.H. Melhem, J.P. Field, D.D Breshears, and S.R. Archer. Dynamic soil/litter surfaces in shrubland vegetation patches: Implications of wind and water erosion for litter decomposition. 15th Annual University of Arizona Graduate College Undergraduate Research Opportunities Consortium Conference. 10 August 2010. Tucson, Arizona.


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Funding:

  

NSF Ecosystems Program, Collaborative Research: Decomposition in drylands: Soil erosion and UV interactions

 

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Publications:

 

Throop, H. L., and S. Archer. 2007. Interrelationships among shrub encroachment, land management and leaf litter decomposition in a semi-desert grassland. Ecological Applications 17:1809-1823.


Okin, GS; D'Odorico, P; Archer, SR, "Impact of feedbacks on Chihuahuan desert grasslands: Transience and metastability", J. Geophysical Research-Biogeosciences vol. 114, (2009). Published, 10.1029/2008JG00083


Field JP, Breshears DD, Whicker JJ, "Toward a more holistic perspective of soil erosion: Why aeolian research needs to explicitly consider fluvial processes and interactions", Aeolian Research, p. 9, vol. 1, (2009). Published


Field, J.P., J. Belnap, D.D. Breshears, J.C. Neff, G.S. Okin, J.J. Whicker, T.H. Painter, S. Ravi, M.C. Reheis, R.L. Reynolds, "The ecology of dust", Frontiers in Ecology and the Environment, p. , vol., (2010). In Press, 10.1890/090050

 

Field, J. P., D.D. Breshears, C.B. Zou, J.J. Whicker, "Interactive effects of grazing and burning on wind- and water-driven sediment fluxes: rangeland management implications", Ecological Applications, p. , vol., (2010). In Press

 

Throop, HL, SR Archer. 2008. Resolving the dryland decomposition conundrum: some new perspectives on potential drivers.  Progress in Botany: 70:171-194.

 

Breshears, D. D., J. J. Whicker, J. P. Field, C. B. Zou, and C. D. Allen. 2009. A conceptual framework for dryland aeolian sediment transport along the grassland-forest continuum: effects of woody plant canopy cover and disturbance. Special Issue on Wind Erosion Measurements. Geomorphology: 105: 28-38.


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Key Collaborators:  

 

Betsy Arnold (Division of Plant Pathology and Microbiology, University  Arizona)

 

Jeannie McLain (USDA-ARS, US Arid-Land Agricultural Research Center, Maricopa, AZ)

 

Curtis Monger (New Mexico State University)

 

Greg Okin (University of California, Los Angeles)

 

Thom Rahn (Los Alamos National Laboratory)  

 

Jeff Whicker (Los Alamos National Laboratory)  

 

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Research Experience for Undergraduates (REU) is an NSF--‐sponsored program that provides undergraduates a summer stipend to conduct independent research projects in conjunction with NSF funded projects under the mentorship of the project’s senior investigators.
 
Who is eligible?
Students who are U.S. citizens or permanent residents enrolled in an undergraduate degree program. Members of underrepresented groups are especially encouraged to apply.
 
What is expected?
Students will develop an independent research project in conjunction with an ongoing collaborative research project at the University of Arizona conducted by Dr. Steve Archer and Dr. David Breshears. Students will summarize their findings in a written report and Present their research in an oral or poster presentation during the Fall Semester of 2011.
 
What is the starting date?
Flexible, but mid--‐May 2011 is preferred.
 
How much is the stipend?
Up to $6,000 or $500 per week.
 
How do I apply?
 
When is the application deadline?
March 15, 2011 or until suitable candidate found.
 
What is the research about?
Decomposition, the breakdown of dead plant and animal material, is a fundamental process that cycles nutrients and carbon through ecosystems. Most of what is known about decomposition comes from studies in High rainfall areas, but this knowledge does not translate well to dryland ecosystems. Decomposition affects long-term soil fertility and carbon storage and therefore plays an important part in determining the role of drylands in the global carbon cycle. Recent studies suggest that ultra‐violet radiation and mixing of eroded soils with litter are important drivers influencing dryland decomposition. Our research tests the importance of these drivers. We hypothesize that the formation of this soil‐litter matrix is determined by wind and water erosion and that once it develops the role of ultra‐violet radiation is mediated. REU students will interact with collaborators at New Mexico  State University (Dr. Heather Throop), Loyola University (Dr. Paul Barnes) and the University Of Kentucky (Dr. Rebecca McCulley).
 

 

 

 

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