Acknowledgement
We thank Takashi Saitoh, Osamu Kishida, and Shiro Tsuyuzaki for their
helpful and insightful comments on the manuscript. We also thank Rei
Sakai, Michio Ishihara, Yoshiaki Takahashi, Masayuki Watarai, Wataru
Mamiya, Toru Miyazaki, and members of Uryu Experimental Forest, Hokkaido
University, for their field assistance. This research was supported by
JSPS KAKENHI Grant Numbers 16J03194 to SK, 16H06179 to SU, and 19H02974
to SU.