Action: Manage woody debris before tree planting
- One replicated, randomized, controlled study in Canada found that removal of woody debris increased the survival rate of planted trees.
- One replicated, controlled study in the USA found mixed effects of removing, chopping and burning woody debris on the size of planted trees.
In forests at higher elevation, where low soil temperatures are limiting factor, the removal of coarse woody debris before restoration planting can affect the establishment of the planted trees.
Supporting evidence from individual studies
A replicated, controlled study in 1988-1994 in temperate coniferous forest in Washington state, USA (Zabowski et al. 2000) found that removing, chopping or burning woody debris had mixed effects on the growth of planted Douglas-fir Pseudotsuga menziesii and lodgepole pine Pinus contorta seedlings. The average total height growth of both species was lower in cleared than control plots and highest following a spring burn (piled: 61 cm; autumn burn: 66; chopped: 71; pulled off site: 71; piled and burned: 72; control: 75; spring burn: 90). In 1989, seven treatment plots (0.3-3.2 ha) were established in each of four sites: control (untreated); woody debris pulled off site (using a cable system); chopped (debris mechanically chopped); debris piled and burned; debris piled; spring burn (low intensity spring broadcast-burn); autumn burn (low-to-medium intensity autumn broadcast-burn). All plots were clearcut in 1988 and planted with Douglas-fir or lodgepole pine seedlings in 1990. The height of 100 seedlings in each plot was measured at the end of the first and fifth growing seasons.
A replicated, randomized, controlled study in 2001-2006 in temperate coniferous forest in Alberta, Canada (Landhäusser 2009) found that woody debris removal decreased the mortality of planted lodgepole pine Pinus contorta seedlings. Mortality of planted seedlings was lower in removal (3%) than control plots (11%). Twelve removal (woody debris removed in winter 2001) and 12 control (woody debris not removed) plots (30 × 30 m) were planted with lodgepole pine (2,000 seedlings/ha) in 2002. The mortality of 20 planted seedlings/plot was monitored in 2003-2006.
- Zabowski D., Java B., Scherer G., Everett R. & Ottmar R. (2000) Timber harvesting residue treatment: Part 1. Responses of conifer seedlings, soils and microclimate. Forest Ecology and Management, 126, 25-34
- Landhäusser S.M. (2009) Impact of slash removal, drag scarification, and mounding on lodgepole pine cone distribution and seedling regeneration after cut-to-length harvesting on high elevation sites. Forest ecology and management, 258, 43-49