Sprouting capacity of Quercus serrata Thunb. and Quercus acutissima Carruth. after cutting canopy trees in an abandoned coppice forest

Rejuvenation by sprouting is a possible solution to prevent abandoned coppice forests in Japan from outbreaks of oak wilt disease. Applying this approach requires examining the sprouting capacity of large-sized oak trees. Therefore, the present study investigated the effects of stump size, sprout characteristics (emerging time and origin position), and environmental factors (slope, convexity, soil moisture, soil net nitrogen mineralization rate (Net-NMR) and canopy closure) on sprout regeneration of the two widely distributed oaks in Japan, Quercus serrata and Quercus acutissima, in the first growing season after cutting. In November 2013, a study plot (40 × 90 m) was set, and canopy trees within the plot and edge areas were cut. We recorded sprout emergence, sprout origin position, sprout survival, and length from May to October 2014. Our data indicated that both species (ca. 60 years old) have not yet lost their ability of sprouting. In Q. acutissima, the sprouting probability increased with light availability and was higher in concave area, and its number of living sprouts was positively related to stump diameter. In Q. serrata, the number of living sprouts increased with light availability. Sprouts emerged earlier and/or originated from the lower part of stump exhibited a higher survival probability. Emerging time substantially influenced sprout growth pattern and its effect followed a similar tendency in both species. Our results evidence that the ability of sprouting and the number of living sprouts might not be reduced in large-sized trees, and the increasing of light availability could promote sprout regeneration.