Hydrological response of a grassland invaded by Lehmann lovegrass in northern Mexico

Resumen

Objective: To calculate the runoff ratio, sediment yield, and infiltration capacity in an open bunchgrass grassland invaded by Lehmann lovegrass in northern Mexico.  

Design/methodology/approach: The runoff-rainfall ratio, infiltration capacity, and the sediment yield were calculated using the simulated rainfall approach. Each simulation (n = 20) lasted 30 min and involved two runs (i.e., dry and wet).

Results: Differences were non-significant for the analyzed variables. The dry run showed a runoff-rainfall ratio of 0.32, and an infiltration capacity of 112 mm h⁻¹, whereas the wet run recorded a runoff-rainfall ratio of 0.39 and an infiltration capacity of 96.9 mm h⁻¹. Regarding sediment yield,  a mean of 59.8 g m^-² and 53.8 g m^-² were recorded for the dry and the wet runs, respectively.

Limitations on study/implications: Our rainfall simulator use a single nozzle connected to a water pump. where is difficult to control the two rainfall properties of a natural rainfall event (rainfall intensity and drop-size characteristics). Therefore, the high application rate does not necessarily correspond to high-intensity storm characteristics if the drop size and velocity are reduced.

Findings/conclusions: Soil moisture content, soil bulk density, slope, and depth were determining factors in the hydrological response of this grassland. The runoff ratio was relatively low, even for the wet runs, suggesting that the sandy loam texture of the soil favors infiltration rates and that this effect is much higher than the ground cover effect in an invaded grassland.