TY - JOUR
T1 - Roles of thinning intensity in hardwood recruitment and diversity in a conifer, Criptomeria japonica plantation
T2 - A 5-year demographic study
AU - Seiwa, Kenji
AU - Etoh, Yukino
AU - Hisita, Masahiro
AU - Masaka, Kazuhiko
AU - Imaji, Aya
AU - Ueno, Naoto
AU - Hasegawa, Yoichi
AU - Konno, Miki
AU - Kanno, Hiroshi
AU - Kimura, Megumi
N1 - Funding Information:
We thank the following individuals for their help with field observations: H. Yusa, N. Igarashi, T. Umezu, K. Kanou, N. Numano, M. Kanno, A. Matsuo, and students of Yamagata University. This work was supported by a Grant from the Ministry of Education, Science, and Culture of Japan (No. 20380084 ).
PY - 2012/4/1
Y1 - 2012/4/1
N2 - To evaluate the role of thinning intensity in increasing hardwood diversity in managed coniferous forests, we investigated the effects of environmental changes caused by thinning on the seedling demography (i.e. seedling emergence, survival, and growth) of hardwood species for 5. years after thinning in 67% thinned (Intensive), 33% thinned (Weak), and unthinned treatments (Control) in a Cryptomeria japonica plantation in northern Japan. Intensive thinning strongly increased light and soil temperature but reduced litter accumulation, thus facilitating seed germination, seedling emergence, and seedling survival of primarily early- and mid-successional species compared to late-successional species. As a result, more early- and mid-successional species were observed in Intensive compared to Weak and Control, whereas the number of late-successional species did not differ among thinning intensities. Thus, the number of species was greatest in Intensive but lowest in Control throughout the 5. years. However, Shannon's diversity index (H'.) did not strongly differ among thinning intensities, largely due to the predominance of the mid-successional species Cornus controversa, particularly in Intensive. In Control and Weak, both seedling survival and height were often greater for advance regeneration than for seedlings newly emerged in the year following thinning, whereas neither variable differed between advance regeneration and seedlings newly emerged in Intensive, mainly due to selective predation of advance regeneration by mammalian herbivores. These results suggest that the future composition of hardwoods can be roughly predicted by the composition of advance regeneration in Weak but by the composition of both advance regeneration and seedlings newly emerged in Intensive. When comparing large individuals (height >1.5. m), the number of species was greatest in Intensive in 2008, 5. years post-thinning, primarily due to rapid vertical growth regardless of successional status. These results suggest that within a C. japonica plantation, a canopy-level mixed conifer-hardwood forest would be more probable and occur more rapidly in Intensive compared to Weak. In Weak, enhanced species diversity would likely be restricted to the understorey layer because of the slower growth rate and lower survival rate of hardwood seedlings caused by the more rapid deterioration of favourable environmental conditions.
AB - To evaluate the role of thinning intensity in increasing hardwood diversity in managed coniferous forests, we investigated the effects of environmental changes caused by thinning on the seedling demography (i.e. seedling emergence, survival, and growth) of hardwood species for 5. years after thinning in 67% thinned (Intensive), 33% thinned (Weak), and unthinned treatments (Control) in a Cryptomeria japonica plantation in northern Japan. Intensive thinning strongly increased light and soil temperature but reduced litter accumulation, thus facilitating seed germination, seedling emergence, and seedling survival of primarily early- and mid-successional species compared to late-successional species. As a result, more early- and mid-successional species were observed in Intensive compared to Weak and Control, whereas the number of late-successional species did not differ among thinning intensities. Thus, the number of species was greatest in Intensive but lowest in Control throughout the 5. years. However, Shannon's diversity index (H'.) did not strongly differ among thinning intensities, largely due to the predominance of the mid-successional species Cornus controversa, particularly in Intensive. In Control and Weak, both seedling survival and height were often greater for advance regeneration than for seedlings newly emerged in the year following thinning, whereas neither variable differed between advance regeneration and seedlings newly emerged in Intensive, mainly due to selective predation of advance regeneration by mammalian herbivores. These results suggest that the future composition of hardwoods can be roughly predicted by the composition of advance regeneration in Weak but by the composition of both advance regeneration and seedlings newly emerged in Intensive. When comparing large individuals (height >1.5. m), the number of species was greatest in Intensive in 2008, 5. years post-thinning, primarily due to rapid vertical growth regardless of successional status. These results suggest that within a C. japonica plantation, a canopy-level mixed conifer-hardwood forest would be more probable and occur more rapidly in Intensive compared to Weak. In Weak, enhanced species diversity would likely be restricted to the understorey layer because of the slower growth rate and lower survival rate of hardwood seedlings caused by the more rapid deterioration of favourable environmental conditions.
KW - Advance regeneration
KW - Seed germination
KW - Seedling emergence
KW - Seedling growth
KW - Seedling survival
KW - Successional status
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U2 - 10.1016/j.foreco.2011.12.014
DO - 10.1016/j.foreco.2011.12.014
M3 - Article
AN - SCOPUS:84856492021
VL - 269
SP - 177
EP - 187
JO - Forest Ecology and Management
JF - Forest Ecology and Management
SN - 0378-1127
ER -