The role of overland flow in sediment and nitrogen budgets of mesquite dunefields, southern New Mexico

Rainfall-simulation experiments were conducted within the Jornada Experimental Range, southern New Mexico, on small plots located on mesquite nabkha and interdune spaces. Data from these experiments were used to determine runoff, sediment and nitrogen losses, and to measure the effect of soil crusts in interdune spaces on these quantities. Results show that runoff from the nabkha plots amounted to only 7.8% of the applied rainfall, whereas from the interdune plots it was 75.7%, rising to 90.8% from plots where the soil crust was protected from raindrop impact. Sediment yield from the nabkha plots averaged 0.24 g m(-2) s(-1) and from the interdune plots it averaged 0.70 g m(-2) s(-1), with no difference between the protected and unprotected plots. Nitrogen losses in runoff averaged 1.45 mg l(-1) from the nabkha plots and 0.61 mg l(-1) from the interdune plots. However, because of the much greater runoff from the interdune areas total nitrogen loss from interdune plots was three times that from the nabkha plots. Rates of annual sediment loss by runoff are estimated to be similar to rates of aeolian erosion, but rates of dissolved nitrogen loss are estimated at only between 2% and 7% of total atmospheric deposition and less than 1% of nitrogen fixation by mesquite. (C) 2002 Elsevier Science Ltd.