The Use of Tree Shelters with Northern Red Oak Natural Regeneration in Southern New England

he use of tree shelters with naturally established red oak seedlings was studied in southern New England mixedhardwood stands where deer browsing limited regeneration height growth. Seedlings of three size classes (basal diameters of 5 mm, 8 mm, and 15 mm) were cut off just above ground level during the dormant season to induce sprouting. Plastic tree shelters were placed over one group in each size class; another group was left without shelters but was protected from deer browsing by fencing. In the first growing season, seedling sprouts inside shelters in the two larger size classes had double the height growth (with some terminals growing out of the 150-cm tall shelters) but less diameter growth, compared to sprouts outside shelters. The height difference was maintamed but not increased over the next 2 growing seasons. Height growth for sprouts from the smaller size class was not •ncreased byshelters. The use of tree shelters with large diameter seedlings stunted 1 The authors are grateful to Yale University and the Massachusetts Metropolitan District Commission (MDC) for use of the study sites, and for the advice and assistance of Bruce Spencer, Paul Lyons, and Thom Kyker-Snowman of the MDC. by browsing may have potential for ensuring successful red oak regeneration without the costs of planting. North. J. Appl. For. 9(4):141-145. The use of tree shelters for protecting planted hardwood seedlings from deer browsing has become widespread in Great Britain over the past 10 years (Potter 1991) and is presently being studied in many other regions (Windell 1991). Tree shelters are tubes made of translucent plastic; they are available in square, circular, or hexagonal shapes, generally 7 to 15 cm in width and 100 to 150 cm in height. They are held in place over individual seedlings by stakes driven into the ground. Tree shelters were originally developed in Great Britain in 1979 by Graham Tuley (Tuley 1983, 1985), principally to protect seedlings from browsing. They provide an additional advantage by altering the microclimate inside the shelter such that seedling height growth is increased over that of unbrowsed, unsheltered seedlings. Temperature and humidity levels are higher inside shelters (Potter 1991), and carbon dioxide levels are also increased, especially if the bottom of the shelter is sealed with mounded soil (Frearson and Weiss 1987). Studies of the operational use of shelters have focused on hardwood plantation establishment, with oak species receiving much of the attention. The use of shelters has been most quickly adopted where investment in planting of hardwoods is already a part of management, as in Great Britain. A study of shelters used for protecting planted northern red oak in Michigan has shown increased height growth over two growing seasons (Lantagne 1990). Red oak is the most commercially important hardwood species in southern New England, occurring in mixed hardwood stands primarily with black birch, red and sugar maple, and other oak species. Natural regeneration often becomes established in the understory of these stands, but seedlings may be prevented from developing in height because of repeated browsing by white-tail deer (Kittredge and Ashton, in prep.). Under these circumstances, savannah-like conditions can develop, in which the understory growing space is usurped by woody shrubs that spread vegetatively, such as mountain-laurel, or by herbaceous ferns and grasses (Horsley 1988), further inhibiting oak seedling development. The potential exists in these situations for using shelters with naturally established oak seedlings to prevent browse damage and accelerate height growth. It would be possible to place shelters directly over the seedlings, but the stems are usually deformed from repeated browsing. An alternative is to cut the stems back to the ground during the dormant season to stimulate the development of a seedling sprout within the shelter. This approach to the use of shelters may be more compatible with the lowinvestment management practiced in many areas, where planting is not