Impact of deer traffic on physical soil erosion and changes in infiltration capacity at forest edges

This study investigated forest edge areas adjacent to a residential road in a hilly area of Nagano Prefecture, Japan, to examine the impact of Cervus nippon (hereafter referred to as “deer”) movements on physical erosion and changes in infiltration capacity of forest soils. The survey area included the edges of cypress and larch forests bordering a residential road west of the Mochizuki Highland Ranch in Mochizuki-machi, Saku City, Nagano Prefecture. Soil erosion was assessed by measuring the height and direction of exposed roots at multiple points. Analysis of root system exposure height (Rh) revealed higher values in the larch forest than in the Japanese cypress forest. Furthermore, the polar coordinate distribution of exposed roots indicated predominant exposure in the steepest slope direction, with some deviations, suggesting that slope angle influences deer movement patterns. Comparisons of cumulative infiltration capacity showed lower values in the cypress forest compared to the larch forest. Soil with clear deer hoof prints exhibited lower infiltration capacity in both areas. The unsaturated hydraulic conductivity (K) for disturbed soil along the deer migration route was approximately half that for natural soil, and in soil with clear deer hoof prints, it decreased to about 1/10 that for natural soil. These findings demonstrate that deer traffic significantly reduces soil infiltration capacity. The results indicated that in forested areas with high levels of deer traffic, K may decrease to 1/2 to 1/10 of normal levels, highlighting the substantial impact of deer activity on forest soil properties.