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.
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.
Hewins, D., H. Throop, S. Archer, and G. Okin. 2008. An exploration of soil movement effects on leaf litter decomposition in a Chihuahan Desert landscape. Fifth Annual Research Insights in Semiarid Ecosystems (RISE) Symposium, University of Arizona, Tucson.
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-
Archer, S, H Throop, G Okin, C Monger, H Lee, DH Smith, M Abu-Salem, J Fitzgerald. 2009. Transport vectors as drivers of dryland decomposition. LTER V Site Review, Sept 2009, Las Cruces, NM.
Archer, S, H Throop, D Browning, K Predick. 2009. Does woody plant encroachment increase ecosystem carbon stocks? Ecological Society of America Annual Meetings, Albuquerque, NM.
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).
Field, J.P., D.D. Breshears, C.B. Zou, and J.J. Whicker. Wind and water erosion under global-change-type conditions and alternate land management practices. Ecological Society of America 94th Annual Meeting. 2-7 August 2009. Albuquerque, NM (talk).
Hewins, D., H. Throop, S. Archer, and G. Okin. 2009. Soil-litter mixing enhances decomposition rates in a Chihuahuan Desert grassland. Ecological Society of America Annual Meetings, Albuquerque, NM (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.
Throop, H., S. Archer, G. Okin, C. Monger, H. Lee, D. H. Smith, M. Abu-Salem, and J. Fitzgerald. 2009. Transport vectors as drivers of dryland decomposition. LTER V Site Review, Sept 2009, Las Cruces, NM.
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).
-2010-
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).
Duerr, A., E. Levi, S. Archer, and K. Predick. 2010. Rates and dynamics of decomposition in drylands. AZ START workshop, University of Arizona. August 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).
Field, J.P., D.D. Breshears, and J.J. Whicker. 2010. Biophysical drivers of erosion and aeolian transport in semiarid grasslands: Consequences of prescribed fire, livestock grazing and climate variability. American Geophysical Union Fall Meeting. 13-17 December 2010. San Francisco, California.
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.
Hewins, D., H. Throop, S. Archer, and G. Okin. 2010. Soil-litter mixing accelerates decomposition and may promote soil aggregate formation in the Chihuahuan Desert. American Geophysical Union, Session B30: Aeolian Processes: Biophysical Drivers and Biogeochemical Implications, San Francisco, CA (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, PA (poster).
Power, R. C., T. H. Melhem, J. P. Field, D. D Breshears, and S. R. Archer. Rates of soil-litter mixing beneath and between shrub canopies in a semiarid shrubland: Combined effects of aeolian/fluvial redistribution. American Geophysical Union Fall Meeting. 13-17 December 2010. San Francisco, CA (poster).
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.
Throop, H., P. Barnes, and S. Archer. 2010. Wind and water transport of soil mediate dryland biogeochemical processes via effects on decomposition. Session B30: Aeolian Processes: Biophysical Drivers and Biogeochemical Implications, American Geophysical Union, San Francisco, CA.
-2011-
Archer, S. 2011. Woody plant imperialism: new perspectives and current challenges. R.D. Watt Centenary Lecture, Faculty of Agriculture, Food and Natural Resources, University of Sydney (March 10, 2011).
Archer, S. 2011. Shrubs gone wild: the ecology of woody plant encroachment. Faculty of Agriculture, Food and Natural Resources, University of Sydney. (March 2011) .
Breshears, D.D. H.D. Adams, C.D. Allen, P.D Brooks, N. S. Cobb, J. P. Field, L. J. Graumlich, M. Guardiola-Claramonte, L. Lopez Hoffman, T. E. Huxman, D. J. Law, A. Macalady, N. G. McDowell, P. D. Royer, P. A. Troch, and J.J. Whicker . Drought, dust and tree death: rapid and widespread landscape transformations. Maurice Kremer Memorial Lecture. University of Nebraska, Linocln. April 4, 2011.
Hewins, D. B., H. L. Throop, S. R. Archer, and G. S. Okin. 2011. Soil-litter mixing accelerates decomposition and facilitates soil aggregate formation in a Chihuahuan Desert grassland. Ecological Society of America Annual Meetings, Austin, TX. Talk.
Levi EM. 2011. Resolving uncertainties in the global carbon cycle: Woody plant encroachment, decomposition and soil formation in dryland ecosystems. University of Arizona Environmental Research Grad Blitz. 1 Feb 2011.
Levi EM, Archer SA, Rasmussen C, Throop H, and D Hewins. 2011. Decomposition and soil aggregate formation in a shrub-invaded Sonoran Desert grassland. 96th Annual Meeting of the Ecological Society of America. 7-12 August 2011. Austin, Texas.
Tobler, M. A., M. K. Grabner, H. L. Throop, S. R. Archer, and P. W. Barnes. 2011. Soil deposition and UV radiation interact to affect dryland litter decomposition. Ecological Society of America Annual Meetings, Austin, TX.
Barger, NN, SR Archer, JL Campbell, CH Huang, J. Morton, AK Knapp. Woody plant proliferation in North American drylands: a synthesis of impacts on ecosystem carbon balance. Journal of Geophysical Research Biogeosciences, 116, G00K07, DOI: 10.1029/2010JG001506
Barnes, PB, HL Throop, DB Hewins, ML Abbene, SR Archer. 2012. Soil coverage reduces photodegradation and promotes development of soil-micorbial films on dryland leaf litter. Ecosystems 15:311-321. DOI: 10.1007/s10021-011-9511-1.
Belnap, J, SM Munson, JP Field, Aeolian and fluvial processes in dryland regions: the need for integrated studies. Ecohydrology 4:615-622.
Bestelmeyer, BT, DP Goolsby, SR Archer. 2011. Spatial patterns in state-and-transition models: a missing link to land management? Journal of Applied Ecolog, 48:746-757.
Breshears, DD, JJ Whicker, JP Field, CB Zou, and CD 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. Geomorphology105: 28-38.
Breshears, DD, TB Kirchner, JJ Whicker, JP Field, CD Allen. 2012. Modeling aeolian transport in response to succession, disturbance and future climate: Dynamic long-term risk assessment for contaminant redistribution. Aeolian Research 3:445-457.
Field, JP, J Belnap, DD Breshears, JC Neff, GS Okin, JJ Whicker, TH Painter, S Ravi, MC Reheis, RL Reynolds. 2010. The ecology of dust, Frontiers in Ecology and the Environment 8:423-430. DOI: 10.1890/090050.
Field JP, DD Breshears, JJ Whicker. 2009. Toward a more holistic perspective of soil erosion: Why aeolian research needs to explicitly consider fluvial processes and interactions. Aeolian Research. 1:9-17. DOI:10.1016/j.aeolia.2009.04.002.1:9-17. 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. 423, vol. 8, (2010). Published, 10.1890/090050.
Field, JP, DD Breshears, JJ Whicker, CB Zou. 2012. Sediment capture by vegetation patches: implications for desertification and increased resource redistribution. J. Geophysical Research-Biogeosciences 117, G01033, DOI: 10.1029/2011JF001663.
Field, JP, DD Breshears, JJ Whicker, CB Zou. 2011. Interactive effects of grazing and burning on wind- and water-driven sediment fluxes: rangeland management implications. Ecological Applications 21:22-32.
Field, JP, DD Breshears, JJ Whicker, CB Zou. 2011. Conserving soil under global-change-type extreme events: On the ratio of wind-to-water-driven sediment fluxes. Journal of Soil and Water Conservation 66:51A-56A. DOI: 10.2489/jswc.66.2.51A.
Okin, GS, D'Odorico, P, Archer, SR. 2009. Impact of feedbacks on Chihuahuan desert grasslands: Transience and metastability. J. Geophysical Research-Biogeosciences 114, 10.1029/2008JG00083.
Ravi, S., DD Breshears, TE Huxman, P D'Odorico. 2010. Land degradation in drylands: interactions among hydrologic-aeolian erosion and vegetation dynamics. Geomorphology 116:236-245. DOI:10.1016/j.geomorph.2009.11.023.
Ravi, S, P D'Odorico, DD Breshears, JP Field, A Goudie, TE Huxman, J Li, GS Okin, R Swap, A Thomas, RS van Pelt, JJ Whicker, T Zobeck. 2011. Aeolian processes and the biosphere: Interactions and feedback loops. Reviews of Geophysics 49, RG3001, DOI: 10.1029/2010RG000328.
Throop, HL, SR Archer. 2008. Resolving the dryland decomposition conundrum: some new perspectives on potential drivers. Progress in Botany: 70:171-194.
Throop, HL, S Archer. 2007. Interrelationships among shrub encroachment, land management and leaf litter decomposition in a semi-desert grassland. Ecological Applications17:1809-1823.
Throop, HL, SR Archer, HC Monger, S Waltman. 2012. When bulk density methods matter: implications for estimating soil organic carbon pools in coarse soils. Journal of Arid Environments. In Press. doi:10.1016/j.jaridenv.2011.08.020.
vironment (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, o
ther studies indicate the level of mixing of wind/water-transported soils with litter is the key factor.
ovel 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.
