The Effects of Different Sizes of Tree Shelters on Blue Oak (Quercus douglasii) Growth

Abstract

Tree shelters have been used effectively in many locations to establish a wide range of tree species including oaks. However, their efficacy in Mediterranean climates like the hardwood rangelands of California has not been thoroughly tested. This study evaluated the field performance of blue oak (Quercus douglasii)—a species that is reported to be regenerating poorly in many locations in the state—protected by several sizes of tree shelters and compared response of directly sown acorns to that of 4-month-old transplants. After five growing seasons, seedlings in all sizes of tree shelters are larger than their unprotected counterparts. Tree shelters have been especially effective in promoting rapid height growth. However, regardless of tree shelter size, when seedlings grew above the tops of the shelters, average height growth diminished and diameter growth increased. Differences among stock types were relatively small, although transplants tended to perform better than directly sown acorns. These results suggest that tree shelters can greatly reduce the time required by seedlings to grow to a size where they are less vulnerable to browsing. As such, they appear to be a promising tool in efforts to regenerate blue oak in California. West. J. Appl. For. 16(4):153-158.

Post‐Planting Treatments Increase Growth of Oregon White Oak (Quercus garryana Dougl. ex Hook.) Seedlings

“…In the FI trial, irrigation effects on height growth may have been influenced by tree shelter height. The fact that seedlings irrigated during year 1 grew less during their second year than those without year 1 irrigation was likely a result of the typical slowing of height growth (McCreary & Tecklin 2001) when the former group surpassed the tops of their solid‐walled tree shelters earlier than the latter group.…”

“…This phenomenon has been attributed to lack of stem movement inside solid‐walled shelters (Kjelgren & Rupp 1997; Johansson 2004) and etiolation due to the reduction in light (Gillespie et al 1996). Once oak seedlings grow beyond the top of tree shelters, there is a significant increase in stem diameter growth rate accompanied by a decrease in height growth rate, resulting in a sturdier stem (McCreary & Tecklin 2001). Although the height growth advantage of solid‐walled tree shelters eventually disappears after saplings grow above shelter height (Clatterbuck 1999), the primary function of shelters is protection from herbivory, and solid‐walled shelters reduce the length of time, relative to mesh shelters, for saplings to grow above the height of animal browse.…”

“…Post‐planting treatments may be necessary to protect and promote growth of planted oak seedlings so that they will reach a height at which terminal shoots are no longer susceptible to animal browse or overtopping by competing vegetation (Potter 1988; McCreary & Tecklin 2001). A variety of post‐planting treatments including tree shelters, mulching, fertilization, and irrigation have been tested on oak species other than Oregon white oak.…”

Effects of Tree Guards and Weed Mats on the Establishment of Native Tree Seedlings: Implications for Forest Restoration in Hong Kong, China

“…However, it has seldom been applied in Hong Kong for afforestation because seedling damage by browsing animals has not been considered a major threat locally. Further research on the use of tree guards has demonstrated that they could also help in modifying the microclimate in ways that improve survival and enhance growth of the seedlings (Potter 1991; West et al 1999; Benfeldt et al 2001; Hemery & Savill 2001; McCreary & Tecklin 2001; Sweeney et al 2002). Mulching applied in afforestation can suppress weed growth and conserve soil moisture, which should in turn improve the growth performance of tree seedlings (Greenly & Rakow 1995).…”

Techniques to Promote Garry Oak Seedling Growth and Survival in Areas with High Levels of Herbivory and Competition

“…Thus, survival of browsed seedlings may depend on the amount of reserves held by seedling oaks, which in turn depends on site conditions and cumulative growth of roots and other plant parts (Shaw 1974, Crow 1988. Given high ungulate pressure in many areas where Garry oaks occur, treatments that protect young oak seedlings may be necessary to enable them to attain a height at which shoots are no longer vulnerable to browsing (Potter 1988, McCreary and Tecklin 2001, Devine et al 2007a. Devine et al (2007a) observed that for Garry oak trees planted at a variety of sites near Olympia, WA, shelters provided young trees with essential protection until they reached a less vulnerable size.…”