Wood properties in relation to foliar phenology of some planted tree species at Kirtipur, central Nepal

Wood water content (WWC), wood saturated water content (WSWC) and wood density (Dw) were measured in planted Pinus roxburghii (chir pine), Alnus nepalensis (alder) and Populus × euramericana (poplar) for one year from (March 2002 to February 2003) at monthly intervals. Phenological events were recorded by frequent visits during the same period. Chir pine and alder retained mature leaves during winter and early summer. Chir pine is unusual in having very short (only 13 months) leaf life span among the pines. With decreasing leaf life span, from chir pine (13 months), alder (10 months) to poplar (7 months), (Dw) wood density decreased, and wood water content (WWC) and wood saturated water content (WSWC) increased. All three species had their highest Dw in late October. Species with high Dw had low WSWC (R=0.91, p0.001). These three species were significantly different with respect to Dw. Both leaf production and leaf fall were more concentrated in poplar and chir pine than in alder. Prolonged leaf production in alder appears to be associated with its inherent behaviour as an early successional species, and a reduction in leaf area due to insect herbivory. Despite their unequal leaf life span, all species began new growth (bud break and leaf flushing) during the dry, hot summer season. Water stored in the stem and that conserved by reduction in transpirational loss due to leaf fall (in chir pine and alder) was available for leaf initial growth. It appears that climate data alone could not explain the water relations as well as phenology of these trees.