The determination of erosion rates from exposed tree roots in the piceance basin, colorado

Abstract

Abstract Tree roots, exposed by hillslope erosion in the Piceance basin of Colorado, were inspected to determine average net erosion rates during the last four centuries. Twenty pinyon pine and juniper root sections were obtained from each of five sites in this region. The date when a root was first exposed by erosion was determined, for 83 of the sections collected, by one of three methods: 1. time of initial cambium dieback; 2. interpretation of annual ring growth pattern; and 3. the earliest occurrence of reaction wood. Analysis indicated no significant difference in erosion rates between the five study sites. However, a strong difference in erosion rates was noted between north‐facing (0–56 mm/yr) and south‐facing (1.18 mm/yr) slopes. No significant difference in erosion rates were found between various south‐facing aspects and local steepness of slopes. Significant differences were noted between erosion rate and the length of time the root was exposed to erosion. Rates of erosion on south‐facing slopes in the pinyon‐juniper community during the last four centuries are as follows: period (years ago) 0‐99 100‐199 200‐299 300‐399 erosion rate (mm/yr) 1‐79 0‐49 0‐33 0‐22. Although there appears to be a slow increase in erosion rates during the three earliest centuries the dramatic increase during the last century may have been substantially augmented by the introduction of cattle into this region approximately one hundred years ago.