Vigor and Density of Shelterbelt Conifers can be Improved

Rows of ponderosa pine and eastern redcedar were released ht 1959 after nearly 20 years of suppression by Russian-olive and green ash in five Nebraska shelterbelts. Three treatments were applied: release on two sides, release on one side, and no release. Treatments increased diameter growth of both conifer, relative to the amount of release; however, height growth was stimulated only when they were released on both sides. Terminals of conifers released on one side only continued to be damaged by overhanging branches of green ash. Foliage density increased markedly in both conifers, and rate of mortality was reduced in pine following release; redcedar suffered no mortality. Release reduced the incidence of Dothistroma needle blight in pine, increased the incidence of cedar-apple rust in redcedar, and increased tip moth damage in pine. Sprout clumps developed rapidly from stumps of cut deciduous trees. Rows of suppressed conifers should be released on both sides. The outside row, if Russian-olive, should be either pulled out, or cut and the stumps poisoned. The inside row of green ash should be cut, and its coppice growth managed for several years to provide temporary low-level density for the shelterbelt until the released conifers can provide it.