Evaluation of silvicultural treatment effects on infiltration, runoff, sediment yield, and soil moisture in a mixed conifer New Mexico forest

Clearing ponderosa pine forests often increases post-harvest runoff and sediment yield, yet there is little research to show if partial thinning of mixed conifer forests similarly produces more runoff and sediment. Rainfall simulations were used to evaluate silvicultural treatment effects on infiltration, runoff, sediment yield, and soil moisture in a southern New Mexico mixed conifer forest. Silvicultural treatments included: untreated control; precommercial thin with slash piled; and precommercial thin with slash scattered. There were no significant differences in infiltration rates, runoff rates, or soil moisture. Time to peak runoff was greater on pile and scatter treatments than on the control during both dry and wet runs. Sediment yield was greater on pile and scatter treatments than on the control during wet runs, yet was very low in all cases. We conclude that southwestern mixed conifer forests may be partially thinned without risk of significant increases in hillslope runoff and sediment yield.