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Modifying landscape connectivity by reducing wind driven sediment redistribution, Northern Chihuahuan Desert, USA

Rachal, D.M., Okin, G.S., Alexander, C., Herrick, J.E., Peters, D.P.C.
Aeolian research 2015 v.17 pp. 129-137
collectors, ecosystems, eolian deposits, grasslands, herbaceous plants, indigenous species, landforms, landscapes, monsoon season, recruitment, sediment transport, shrublands, shrubs, soil erosion, wind, Chihuahuan Desert, New Mexico
Shrub encroachment into perennial grasslands is occurring in many arid parts of the world. As shrubs displace perennial grasslands, bare patches can coalesce creating sediment transport pathways that further enhance sediment fluxes by wind transport. Reducing the connectedness of these 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 in bare gaps of existing shrublands to block sediment movement by wind transport on two sites: the basin floor and a bajada (i.e. piedmont slope) at the Jornada Basin LTER in southern New Mexico. Wind blown sediment collectors and short-lived radionuclides (²¹⁰Pbex, ¹³⁷Cs, and ⁷Be) were used to determine if these structures are affecting seasonal aeolian sediment transport within bare gaps. Net sediment flux rates at 10cm height indicate a loss of 2.5–14.2gm⁻²d⁻¹ for both sites for the monsoon season (Jul–Nov), while the basin floor site was the most responsive in reducing sediment transport by collecting 16.5gm⁻²d⁻¹ over the windy season (Dec–May). Con-Mods contained 30–50% higher surface radionuclide activities than the control plots for both transport seasons on the basin floor. However, there was no detectible difference between surface concentrations for the structures and controls seasonally on the bajada site. This study demonstrates that changes in connectivity can influence sediment movement. Altering sediment transport through bare gaps could influence ecosystem state changes in arid systems; thereby increasing the likelihood of recruitment of native plants.