Timber harvesting residue treatment. Part II. Understory vegetation response

Remove woody debris after timber harvest

A replicated, controlled study in 1988-1991 in temperate coniferous forest in Washington State, USA (Scherer et al. 2000) found that different woody debris removal treatments had mixed effects on understory vegetation cover but not on species richness. At one site, vegetation cover was higher in control than other treatments (chopped: 1.8%; spring burn: 2.5%; pulled off site: 4.2%; control: 7.1%). At a second site, cover was higher in control, pulled off and autumn burn treatments (2.9, 1.2 and 1.2% respectively) than spring burn and chopped treatments (0.2% in both). At the other two sites it was similar among treatments (chopped: 2.7-2.8%; spring burn: 2.9-5.7%; autumn burn: 3.8-4.7%; pulled off: 1.2-5.7%; control: 2.1-2.2%). The number of species/m² was similar among treatments at all four sites (chopped: 7-26; spring burn: 7-22; autumn burn: 8-20; pulled off: 5-20; control: 10-18). In 1989, five treatment plots (0.25-3.2 ha) were established in each of four sites: control (untreated); pulled off (woody debris pulled off the site); chopped (debris chopped); spring burn (low intensity burn); autumn burn (low to medium intensity). All plots were clearcut in 1988. Data were collected in 1991 in 15 quadrats (1 m²) in each treatment plot.