Resilience of stand structure and tree species diversity in subtropical forest degraded by clear logging |
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| Authors: | Shinjiro Fujii Yasuhiro Kubota Tsutomu Enoki |
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| Institution: | (1) Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, Fukuoka 811-2415, Japan;(2) Laboratory of Ecology and Systematics, Faculty of Science, University of the Ryukyus, Nishihara Okinawa, 903-0213, Japan;(3) Faculty of Agriculture, Kyushu University, Fukuoka 811-2415, Japan |
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| Abstract: | Subtropical forests in the Ryukyu Islands have been degraded by silvicultural practices, and thus their structural attributes
are being shifted to other states dominated by a few tree species. This study clarified the mechanisms of the change, and
examined the effect of clear logging on the resilience of a subtropical forest. Sprouting regeneration and typhoon disturbance
were introduced into an individual-based model, SEIB-DGVM, for describing stand development and succession. The regeneration
dynamics from young secondary to old-growth stands were reproduced fairly well with the model. Sprouting recruitment produced
high stem density at the beginning of stand development, which caused a self-thinning trajectory following the −3/2 power
law. In the late development stage after 70 years, tree species diversity fluctuated because of the regenerative response
of sprouting species and the facilitatory effect of typhoon disturbance on the coexistence of subordinate species. The death
of canopy trees because of typhoon disturbances reduced the dominance of Castanopsis sieboldii, and depressed its dominance in the understory. Consequently, the understory species could establish by virtue of fallen
canopy trees, and tree species diversity increased at the stand level. Clear logging experiments in the model revealed that
species diversity deteriorated, especially in the stand dominated by sprouting species. Resilience of subtropical forests
was determined by initial species composition before clear logging. Our simulation results suggest that repeated logging drives
subtropical forests with high species diversity to a stand monopolized by C. sieboldii. |
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