Action: Use tree guards or shelters to protect planted trees
- One replicated, randomized, controlled study in the USA found that using light but not dark coloured plastic tree shelters increased the survival rate of planted tree seedlings. One replicated, controlled study in Hong Kong found that tree guards increased tree height after 37 but not 44 months.
Tree guards can be used to protect planted tree seedlings from browsing, cold etc. and increase their establishment chances.
Supporting evidence from individual studies
A replicated, randomized, controlled study in 1996-1997 in temperate coniferous forest in Colorado, USA (Jacobs & Steinbeck 2001) found that tree shelters increased the survival rate of Engelmann spruce Picea engelmannii seedlings. The survival rate of Engelmann spruce was higher with the three light-coloured tree shelters (95-99%) than the controls (70%) and the lowest with the dark brown shelters (5%). Four replicates of each of five treatments were randomly assigned to 20 plots in each of three blocks (0.5 ha): four colours of recycled polyethylene plastic tree shelters (31 cm height and 9 cm diameter), ranging from nearly clear to brown, and a control (using materials from within the site, e.g. logs, stumps, shrubs, rocks, to protect seedlings). In August-September 1996, 25 seedlings were planted in each plot (total of 1,500 seedlings). Data were collected in 1997.
A replicated, controlled study in 1999-2002 in a degraded tropical forest in Hong Kong (Lai & Wong 2005) found that using tree guards increased the height of thick-leaved oak Cyclobalanopsis edithae seedlings, also covered with weed mats, but only in the first three years. After 37 months, seedling height was greater with tree guards (80 cm) than control (57 cm). However, after 44 months, there was no difference between treatments (control: 85; tree guards: 96 cm). Fifteen oak seedlings were planted in each of four replicate (rows) of each tree guards (45 cm high plastic tree guard) and control treatments. All rows were covered with weed mats (0.4 × 0.4 m hessian cloth around each seeding). Seedlings were planted in June 1999 and observed for approximately 44 months.
- Jacobs D.F. & Steinbeck K. (2001) Tree shelters improve the survival and growth of planted Engelmann spruce seedlings in southwestern Colorado. Western Journal of Applied Forestry, 16, 114-120
- Lai P.C.C. & Wong B.S.F. (2005) Effects of tree guards and weed mats on the establishment of native tree seedlings: implications for forest restoration in Hong Kong, China. Restoration Ecology, 13, 138-143