EFFECT OF INITIAL SPACING ON GAS PERMEABILITY OF POPULUS NIGRA VAR. BETULIFOLIA

Initial spacing during planting affects growth rate of trees and consequently influences various properties of wood. Permeability is an important property of wood that determines many of its applications. The present study was therefore focused on the effect of initial spacing on gas permeability of Populus nigra var. betulifolia in connection with its vessel properties. Treatments included four initial spacings of the poplar cuttings at 3 × 4, 3 × 6.7, 3 × 8 and 3 × 10 m of 10-year-old poplar trees, intercropped with alfalfa. Specific gas permeability values were measured at breast height in longitudinal and radial directions. Maximum longitudinal permeability value was 1631.26 × 10-13 m-3 m-1 for the 3 × 10 m treatment where maximum vessel lumen diameter was found to be 67.09 μm. Minimum longitudinal permeability was in the 3 × 4 m treatment with a value of 1052.15 × 10-13 m3 m-1 where minimum vessel lumen diameter was observed (63.17 μm). Vessel lumen area decreased by 10.2% as the initial spacing increased from 3 × 4 to 3 × 10 m but a clear positive relation was still found between initial spacing and gas permeability. Therefore, it can be concluded that vessel lumen diameter was more influential in the determination of gas permeability than percentage of vessel lumen area. Jarak tanaman awal mempengaruhi kadar pertumbuhan pokok dan seterusnya mempengaruhi pelbagai ciri kayu. Kebolehtelapan merupakan ciri penting yang menentukan penggunaan kayu. Kajian ini bertumpu pada kesan jarak tanaman awal terhadap kebolehtelapan gas Populus nigra var. betulifolia dari segi ciri-ciri veselnya. Uji kaji melibatkan empat jarak tanaman awal keratan poplar iaitu 3 m × 4 m, 3 m × 6.7 m, 3 m × 8 m dan 3 m × 10 m bagi pokok poplar berusia 10 tahun yang diselingkan dengan alfalfa. Nilai kebolehtelapan gas spesifik pokok poplar disukat pada aras dada pada arah membujur dan arah jejari. Nilai kebolehtelapan membujur maksimum ialah 1631.26 × 10-13 m3 m-1 untuk jarak 3 m × 10 m yang turut menunjukkan diameter lumen vesel maksimum dengan nilai 67.09 μm. Kebolehtelapan membujur minimum dicerap pada jarak 3 m × 4 m dan nilainya ialah 1052.15 × 10-13 m3 m-1. Jarak ini juga mempamerkan diameter lumen vesel minimum iaitu 63.17 μm. Luas lumen vesel berkurangan sebanyak 10.2% apabila jarak awal meningkat dari 3 m × 4 m ke 3 m × 10 m. Namun hubungan positif yang jelas tetap wujud antara jarak tanaman awal dengan kebolehtelapan gas. Oleh itu, bolehlah disimpulkan bahawa diameter lumen