Effects of tree shelters on planted red oaks after six growing seasons

A 22 year-old shelterwood treatment that failed to regenerate oaks on an upland site in Michigan was clearcut in the fall of 1986 and planted with 2-0 northern red oak (Quercus rubra L.) seedlings the following spring. The four planting treatments included: control (clearcut harvest only), brush control only, 48 inch tree shelters only, and brush control plus tree shelters. After three years, 65 percent of sheltered northern red oak seedlings were at least 47 inches tall and on average 21 inches taller than unsheltered seedlings. After six years, a total of 92 percent of sheltered trees had reached a minimum height of 47 inches. By 1992, the height growth of sheltered trees made DBH measurements possible on 80 percent of sheltered trees (height ≥ 4.6 ft) compared to only 52 percent of unsheltered trees. Sheltered trees had significantly greater average diameters. Tree shelters have improved survival, diameter and total height growth over the first six growing seasons. The data showed however, that average tree height growth was comparable between sheltered and unsheltered trees for the past three growing seasons. The 19 inch total height advantage appears to be the result of accelerated growth during the first three growing seasons when trees were within the 48 inch tall shelters.