Effects of slash chips placed around trees planted after whole-tree logging: movement and nutrient supply

Abstract

Whole-tree harvesting at clearcutting sites using cable yarding systems and processors disrupts the process of nutrient return via leafy and woody slash otherwise left on the forest floor. This study examined the effect of placing slash chips around trees planted in a clearcut area. Chips made from branches with needles (branch chips) and three types of wood scrap chips (wood chips) were prepared for the study. Changes in the thickness of slash chip layers and in the concentration and weight of decomposing chips were measured. The nutrient effect of applying chips to the soil was analyzed, and the effects of chip coverage on weed control were measured. The branch and 18-mm-thick wood chips were stable on slopes; 9- and 4-mm-thick wood chips readily shifted to the lower and outer positions in the plots. On branch chips and wood chips, the annual rate of decomposition (k) calculated by exponential model was 0.69–0.7 and 0.04–0.17/year, respectively. Branch chips provided more nutrients for decomposers, and were rapidly decomposed during the first month. Nevertheless, the nutrient effect on the soil could not be confirmed. Placing branch or wood chips around planted trees effectively eliminated the need for weeding for 1 year, but these light materials did not suppress shrub sprouting.