Heartwood-Sapwood-Bark profiles and association studies in Pterocarpus marsupium Roxb., a vulnerable antidiabetic forestry species of sub- tropical forest

Pterocarpus marsupium Roxb. is a multipurpose forestry species of the sub-tropical region of the Indian subcontinent and its heartwood is known for excellent antidiabetic properties. However, due to unsustainable extraction, its populations are dwindling in natural ranges. In the present investigation, we studied the variations of heartwood and related characters in populations sampled from central India. For this, we sampled populations from different sites falling in mixed and sal forest of the central Indian state of Madhya Pradesh. Adaptive cluster sampling was followed for selection of study sites. Wood core samples were extracted at breast height using a Haglof three-thread increment borer. For each core, we measured bark thickness, sapwood thickness, heartwood diameter (cm), bark (%), sapwood (%), heartwood (%), sapwood area, heartwood area, sapwood area to heartwood area ratio and cross-sectional area. The analysis revealed that bark thickness ranged from 1.0 - 3.6 cm with an average of 2.21 cm; sapwood thickness from 2.0 - 12.0 cm with an average of 6.16 cm; heartwood diameter from 7.29 - 102.19 cm with an average of 36.77 cm. Bark, sapwood and heartwood percentages at breast height ranged from 1.37-31.9%, 1.96-45.97%, 39.23-96.68% with a mean value of 6.34%, 17.80% and 75.86%, respectively. Sapwood area, heartwood area and cross section area at breast height was also estimated and these parameters ranged from 39.76-1043 cm2, 41.68-8197.6 cm2 and 161.2-9476.5 cm2, respectively. Despite its vulnerable status, P. marsupium populations recorded high variations for heartwood and related parameters. Correlation and path coefficient analysis revealed that bark (%), sapwood (%) and cross-sectional area are the most significant characters having a bearing on the heartwood percentage and could be utilised for selection, improvement and exploitation of heartwood.