Abstract:

Variations in amount and ring number of sapwood and heartwood were analyzed by using 350 benzidine-stained wood disks from 40 sampled trees of four Pinus tabulaeformis stands in limestone area of Taihang Mountain，varying in age and density. At the within tree level heartwood radius and sapwood width have no significant difference among four stem orientations (P>0.05). Sapwood width remained relatively constant along the tree stems from 0.50～1.00 m above the stem bases to 2.46～3.22 m below treetops，heartwood radius，heartwood area and sapwood area decreased with tree height，their longitudinal variations were well explained by stem cross-section diameter. At the individual tree level sapwood and heartwood amount varied greatly，and correlated best to DBH among selected tree variables. At the stand level sapwood and heartwood amount had significant difference (P<0.05)，their variation patterns were same as the stand age and stand growth level. The heartwood initiation cambial age was 13 years，number of heartwood rings increased with cambial age，the latter can account for 97.9% of variation of the former. Heartwood formation expressed as the number of new heartwood rings formed each year was found to increase from 0.5 rings per year at a cambial age of 40 years to 0.7 rings per year at a cambial age of 60 years. These results imply that it seems feasible to predict sapwood and heartwood amount and heartwood ring number by using inventory factors.

Key words: Pinus tablaeformis, heartwood amount, sapwood amount, number of heartwood rings, variation