Modeling landscape wind erosion processes on rangelands using the APEX model

Abstract

Rangelands provide vital ecosystem services and comprise 36% of U.S. and 25% of world lands. Approximately 20 to 73% of these rangelands are already degraded. Soil erosion driven by winds is a significant cause of this degradation. Minimal work has been done to evaluate the influence of wind erosion on rangeland dominated landscapes or to assess the effect of landscape-scale soil and water conservation and management practices on reducing wind erosion due to its inherent complexity and nonpoint source nature. Our approach is to use an integrated and holistic eco-hydrologic model. The main objective of this study is to integrate process-based landscape wind erosion modeling schemes into the Agricultural Policy/Environmental eXtender (APEX) model (version 1905; APEX1905) for simulating horizontal aeolian sediment transport and vertical particles transport on rangelands. We demonstrate the performance and capability of the model using field data collected at the USDA ARS Jornada Experimental Range in New Mexico, U.S. A benchmark APEX1905 model that runs on high-resolution sub-daily wind speed data and daily average vegetation gap distribution derived from monthly field measurements. The benchmark APEX1905 model captured the variability in observed aeolian sediment transport during 2015–2017 reasonably well with an R2 = 0.58 and a RMSE = 2.60. When the highly variable sub-daily measured wind speed and vegetation gap distribution data were substituted with the daily average wind speed and APEX1905 estimated daily vegetation gap, the APEX1905 reproduced well the benchmark model estimates with the performance statistic of R2 = 0.77 and RMSE=0.54 for the horizontal aeolian sediment transport; and R2 = 0.82 and RMSE = 0.85 for vertical particle transport. Overall, provided limited aeolian watershed data sets, the APEX1905 is demonstrated to be reliable in estimating wind erosion in arid, desert rangeland landscapes using daily average wind speed and simulated vegetation characteristics. Benefiting from the long-established algorithms of simulating plant growth dynamics and topsoil moisture content in APEX, APEX1905 offers a robust and process-based estimation of wind erosion in areas where wind and vegetation data are scarce.