Growth dynamics in wood formation of plantation-grown Swietenia macrophylla King and Carapa guianensis Aubl.

In the present study, the growth dynamics in wood formation of four to six-year-old plantation-grown Swietenia macrophylla King and Carapa guianensis Aubl. was investigated. As to study the influence of the plantation management on the cambial growth dynamics of the trees, the investigations were carried out in three different plantation systems ((I) monoculture system, (II) mixed culture system, (III) enrichment system). The anatomical structure of the cambial zone of nine Swietenia and six Carapa trees was investigated by means of light microscopy of small samples collected throughout the year with a borer (diameter 1.4 and 1.9 mm, respectively). Special attention was given to the formation of increment zones and the state of the cambium (period of cell division/ cambial dormancy). In addition, the growth dynamics in wood formation of ten Swietenia and ten Carapa trees was dated by the "pinning method" from April 1995 until March 1997 in monthly intervals. Due to anatomical characteristics of the wound reactions studied by light microscopy, accurate measurements were carried out for increment measurements 0.3 mm. The wood anatomical studies indicated that the formation of increment zones of Swietenia and Carapa are not annual and not correlated between individual trees. In the xylem of Swietenia and Carapa, two types of increment zones were found. In the inner part of the stem, a formation of vessel bands was observed, whereas in the outer part of the stem a distinct formation of parenchyma bands was found. From the study on the growth dynamics of the trees, it became obvious that the formation of parenchyma bands in the xylem of Swietenia in August/ September is correlated with the initiation of a cambial dormancy during the dry season. In contrast to that, no significant relationship was found between the rate of periclinal cell divisions of Carapa and the seasonal variation of the soil water supply. Furthermore, a reduced increment of Swietenia in the plantation systems II and III compared to system I was found, due to a low rate of periclinal cell divisions and a reduced period of cambial activity. Only slight differences in growth increment were found for Carapa grown in system I, II, and III. From these findings, it was concluded that Carapa guianensis Aubl. is more adapted to sustainable growth throughout the year and under various site conditions compared to Swietenia macrophylla King.