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ARS Home » Plains Area » Las Cruces, New Mexico » Range Management Research » Research » Publications at this Location » Publication #291337
Title: Modifying landscape connectivity by reducing wind driven sediment redistribution, northern Chihuahuan Desert, USA

Author
item RACHAL, DAVID - New Mexico State University
item OKIN, GREGORY - University Of California
item ALEXANDER, C - Skidaway Institute Of Oceanography
item Herrick, Jeffrey - Jeff
item Peters, Debra

Submitted to: Aeolian Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/2/2015
Publication Date: 6/1/2015
Publication URL: http://handle.nal.usda.gov/10113/60828
Citation: Rachal, D.M., Okin, G.S., Alexander, C., Herrick, J.E., Peters, D.C. 2015. Modifying landscape connectivity by reducing wind driven sediment redistribution, northern Chihuahuan Desert, USA. Aeolian Research. 17:129-137.

Interpretive Summary: Shrub encroachment into perennial grasslands leads to the coalescence of bare patches and an increase in soil erosion and sediment fluxes by wind and water. Reducing the connectedness of these sediment transport pathways could slow or stop grassland loss by limiting sediment redistribution. We tested this hypothesis using sediment retention structures, hereafter called “Connectivity Modifiers” (Con-Mods), placed within bare gaps of shrublands on two sites: the basin floor and a bajada at the Jornada Basin USDA- LTER in southern New Mexico. Short-lived radionuclide (210Pbex, 137Cs, and 7Be) and sediment collectors were used to determine if these structures are affecting seasonal aeolian sediment transport within bare gaps. Con-Mods contained 30 to 50% higher surface radionuclide activities than control plots on the basin floor. However, there was no detectible difference between structures and control plots on the bajada site. Net sediment flux rates at 10 cm height indicate a loss of -2.5 to -14.2 g m-2 d-1 for both landform units for the monsoon season (Jul-Nov), while ConMods on the basin floor reduced sediment transport by collecting 16.5 g m-2 d-1 over the windy season (Dec-May). This study demonstrates that changes in connectivity by wind can influence sediment movement. Altering sediment transport could influence ecosystem state changes in arid and semi-arid systems by increasing the likelihood of recruitment of native grasses and other herbaceous plants.

Technical Abstract: Shrub encroachment into perennial grasslands is occurring in many arid and semi-arid parts of the world. As shrubs displace perennial grasslands, bare patches coalesce to enhance soil erosion and sediment fluxes by wind and water transport. Reducing the connectedness of these sediment transport pathways could slow or stop grassland loss by limiting sediment redistribution. To test this hypothesis, sediment retention structures, hereafter called “Connectivity Modifiers” (Con-Mods), were placed within bare gaps of existing shrublands on two sites: the basin floor and a bajada at the Jornada Basin USDA- LTER in southern New Mexico. Short-lived radionuclide (210Pbex, 137Cs, and 7Be) and sediment collectors were used to determine if these structures are affecting seasonal aeolian sediment transport within bare gaps. Con-Mods contained 30 to 50% higher surface radionuclide activities than control plots on the basin floor. However, there was no detectible difference between surface activities for the structures and control plots on the bajada site. Net sediment flux rates at 10 cm height indicate a loss of -2.5 to -14.2 g m-2 d-1 for both landform units for the monsoon season (Jul-Nov), while the basin floor site was the most responsive in reducing sediment transport by collecting 16.5 g m-2 d-1 over the windy season (Dec-May). This study demonstrates that changes in connectivity by wind can influence sediment movement. Altering sediment transport through bare gaps could influence ecosystem state changes in arid and semi-arid systems; thereby increasing the likelihood of recruitment of native grasses and other herbaceous plants.