Simulating the heartwood formation process of Erythrophleum fordii in South China

We studied the formation of heartwood in Ery- throphleumfordii Oliv., an endangered rosewood species, by cross-section analysis on 52 stumps aged 28-57 years and arbitrarily sampled from natural forests in South China. Width and area of heartwood were positively correlated with age and xylem width （XW）, and were independent of annual radial growth. The proportions of heartwood and sapwood areas were equal at about 40 years. The heartwood formation pro- cess was simulated by linear regression of age and XW.

Heartwood variations in mid-aged plantations of Erythrophleum fordii

Erythrophleum fordii Oliv.(Caesalpiniaceae)is a rosewood species naturally distributed in southeast Asia and south China,and the heartwood is commonly used for high-quality crafts and furniture.While there are differences in heartwood development among single trees with distinct social status,the relationship between heartwood development and growth performance remains unclear.This information is essential to improve plantation management for high-yield heartwood production.Forty dominant,intermediate and suppressed trees were sampled from E.fordii plantations aged in 32-35 years in Pingxiang City,Guangxi,China.Stem analysis was carried out to determine horizontal and vertical variations of heartwood and sapwood.Number of annual rings,diameter and area of heartwood and sapwood as well as ratios of heartwood diameter and area at breast height were all significantly influenced by the social status of trees in stands(P<0.05).In these mid-aged plantations,E.fordii stems developed heartwood once the xylem diameter reached 5-10 cm,and then heartwood diameter and area increased with increasing xylem diameter.Heartwood ring numbers,diameter and area as well as their ratios decreased with increasing height,while sapwood ring numbers and diameter were relatively constant within the section where heartwood occurred.Heartwood and sapwood diameters were equal at heights of approximately 6-m for dominant,5-m for intermediate and 3-m for suppressed trees.Dominant trees differed considerably from intermediate and suppressed trees in heartwood volume,while heartwood volume ratios were all below 30%,and near 90%in the stem section below 8-m height regardless of social status.Relationship analysis showed that DBH was the most important factor influencing heartwood in even-aged stands.The findings provide evidence for crop tree selection,thinning regimes and reasonable management of plantations of E.fordii.