DETERMINATION OF EROSION RATES FROM EXPOSED TREE ROOTS IN THE PICEANCE BASIN, COLORADO.

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 and juniper root sections were obtained from each of five sites in this region. The data 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. 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.