RESPONSE OF UNMANAGED ACACIA MANGIUM PLANTATIONS TO DELAYED THINNING IN NORTH-EAST THAILAND

The effects of delayed thinning on the survival and growth of residual trees in 14-year-old unmanaged Acacia mangium stands in north-eastern Thailand were studied for 8.3 years. Two types of row-thinning were used: alternate-row thinning and every-third-row thinning plus selective thinning of the re...

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Bibliographic Details
Published in:Journal of tropical forest science 2009-07, Vol.21 (3), p.223-234
Main Authors: Kamo, K, Vacharangkura, T, Tiyanon, S, Viriyabuncha, C, Thaingam, R, Sakai, M
Format: Article
Language:English
Subjects:
Forest stands
Forestry research
Mortality
Pine trees
Plant thinning
Plantation forestry
Plantations
Trees
Tropical forestry
Tropical forests
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Summary:The effects of delayed thinning on the survival and growth of residual trees in 14-year-old unmanaged Acacia mangium stands in north-eastern Thailand were studied for 8.3 years. Two types of row-thinning were used: alternate-row thinning and every-third-row thinning plus selective thinning of the remaining two rows. Both types reduced mortality of residual trees to less than 26% of that in the unthinned stand. Both types also increased stand and individual stem volume compared with the unthinned stand. The stimulation of volume increment occurred with 1.2 years of thinning but lasted for only about 3 years. Trees of all sizes responded, although increased volume increment was greatest for larger trees. During the 8.3 years, alternate-row and third-row plus low thinning increased total stand volume increment by 5.8 and 4.2 times above that of the unthinned stand. Both thinning regimes also promoted greater production of merchantable wood volume. Of the two thinning methods, alternate-row thinning was superior to third-row plus low thinning in terms of total stand volume increment and merchantable volume production. Our results indicated that previously unmanaged stands of A. mangium were still capable of responding to thinning with increased volume growth even when the treatment was delayed 10 years, beyond the time normally recommended for the species. Dirian Acacia mangium tak terurus berusia 14 tahun di timur laut negara Thai dikaji selama 8.3 tahun. Kajian tertumpu kepada kesan penjarangan tertunda terhadap kemandirian dan pertumbuhan pokok-pokok yang tinggal. Dua jenis penjarangan digunakan: penjarangan baris selang dan penjarangan baris ketiga + penjarangan terpilih pada dua baris yang lain. Kedua-dua jenis penjarangan mengurangkan kematian pokok yang tinggal kepada kurang daripada 26% nilai dirian yang tidak dijarangkan. Tambahan isi padu berlaku 1.2 tahun selepas penjarangan tetapi cuma selama 3 tahun sahaja. Pokok pelbagai saiz menunjukkan tambahan isi padu tetapi tambahannya lebih tinggi dalam pokok besar. Selama 8.3 tahun, jumlah pertambahan isi padu dirian bagi penjarangan baris selang dan penjarangan baris ketiga + pokok-pokok kelas kecil masing-masing 5.8 kali dan 4.2 kali lebih tinggi daripada isi padu dirian tak dijarang. Kedua-dua jenis penjarangan menghasilkan isi padu kayu niaga yang lebih tinggi. Penjarangan baris selang lebih baik daripada penjarangan baris ketiga + pokok-pokok kelas kecil dari segi tambahan jumlah isi padu dirian dan p
ISSN:0128-1283
2521-9847