SURFACE RELEASED STRAIN (SRS) AND WOOD ANATOMY OF YOUNG FALCATARIA FALCATA TREES PLANTED IN AGUSAN DEL NORTE, PHILIPPINES

This study was conducted to assess the variation in surface released strain (SRS), fiber length (FL) and diameter (FD), and vessel length (VL) and diameter (VD) of 3-6-year-old leaning and straight Falcataria falcata (L) Greuter & R. Rankin trees. This pioneering study on F. falcata growth strain in the Philippines aimed to determine the influence of growth orientation on SRS and wood anatomy, which affect mechanical properties and defect formation. Surface released strain varied significantly, with the highest SRS values recorded on the east, upper side of the lean in leaning trees. Meanwhile, FL and FD at the four cardinal points (north, south, east, and west) were not significantly different on leaning and straight trees. For leaning trees, VL from the west side of the tree stem was significantly lower (p = 0.009) than that in the other three cardinal directions. Mean FL (± standard deviation) was significantly higher in leaning trees (1.103 ± 0.007, p = 0.012) than in straight trees (0.989 ± 0.012 mm). The mean FD of straight trees was significantly higher than that of leaning trees (0.029 ± 0.0006 mm and 0.020 ± 0.0002 mm, respectively, p = 0.0004). The length of vessels measured from the north, south, east, and west sides of straight trees were not significantly different (p = 0.399). There was no significant difference in VD measured in the four cardinal directions of leaning and straight trees. Correlation analysis revealed a weak positive correlation between SRS and all anatomical properties except VD.