The Geomorphic Effects of Gophers on Soil Characteristics and Sediment Compaction: A Case Study from Alpine Treeline, Sangre de Cristo Mountains, Colorado, USA

Digging by gophers disturbs near-surface soils, deposits sediment in mounds and “eskers” in non-uniform surface patterns, and affects surface penetrability of soils at alpine treeline. Soil samples were collected and soil compaction was measured at three sites in the Culebra Range of the Sangre de Cristo Mountains in southern Colorado, to determine the effects of gophers on surface compaction and soil characteristics there. At each of these three sites, soil samples were collected from two gopher mounds, two eskers, and two undisturbed sites. Penetrometer measurements were taken on thirty gopher mounds, thirty gopher “eskers” that represent redistributed soil deposited in snow tunnels during winter, and thirty adjacent surfaces not affected by gopher digging. Hydrometer analysis was employed to determine particle size distribution for the soil samples, and each soil sample was color-keyed using the Munsell soil color system. Particle sizes and colors did not substantially differ among the three soil types, or by sample site. Eskers and mounds were significantly less compacted (ANOVA) than surface samples taken from locations unaffected by gopher digging, and not significantly different from each other (eskers and mounds 1.38 and 1.43 kg cm -2 average compaction; unaffected soils, 2.83 kg cm -2 average). Excavating by gophers produces lower surface compaction at treeline that may aid tree seedling establishment.