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Restoring Grazed Riparian Areas With Oaks and Willows

Oaks ‘n’ Folks – Volume 11, Issue 2 – September, 1996

Common land management practice in California in the 1960s was the removal of all woody vegetation on hardwood rangelands to promote increased forage production for livestock. This practice was particularly prevalent in the northern part of the Sacramento Valley, and though it is rare today, the effects of previous clearings remain. These can include land slips, soil erosion, and sedimentation in water ways; degradation of wildlife habitat;and vast expanses of visually barren hillsides.

At the University of California Sierra Foothill Research and Extension Center near Browns Valley, a large wooded area known as Forbes Hill and comprising close to 1000 acres, was cleared of woody vegetation about 30years ago. This conversion was undertaken to improve forage production for a research cattle herd, and to provide a set of relatively uniform pastures for fertilization trials. Today, the cleared hillside includes a perennial stream that has little vegetation along its banks except for cattails.

In 1994, we initiated a project to restore a 2,000-foot portion of this stream, known as Slicks Canyon, with woody plants. We wanted to evaluate what techniques or practices would be effective in restoring several tree species in a riparian area that is relatively intensively grazed by cattle. We also wanted to be able to show the public during field days and training sessions what they could expect from various approaches.

Eight-hundred-forty native seedlings and cuttings for this project were planted in spring 1994, including three species of oaks and two species of willows. Five treatments were evaluated, including individual plantings protected with securely staked tree shelters; planted plots with livestock excluded; planted plots accessible to livestock; plots not planted, but livestock excluded; and plots not planted and livestock not excluded.

While this project has been underway only for a little over two years and the data is preliminary, it suggests that willows can be successfully established if cattle are fenced out of planting areas, or securely staked tree shelters are placed around individual cuttings. In fenced areas, some of the willows are now over 12 feet tall and well on their way to becoming established trees. Oaks, on the other hand, have survived and grown well only when they were protected by tree shelters. To date, some are approaching seven feet tall and are growing vigorously. However, in fenced areas, where individual seedlings are not protected, mortality of oaks has been almost complete from a combination of grasshopper, vole, and deer herbivory, as well as from weed competition. In areas accessible to livestock, but unprotected by tree shelters, survival (and growth) of all species has been negligible.

These results suggest that the approaches used for establishing trees along cleared streams that are grazed by cattle may vary depending on the species being planted, with fencing suitable for willows, but individual tree shelters necessary for oaks.

prepared and edited by Richard B. Standiford and Pamela Tinnin