Adaptability and Growth of a Fast-Growing Neolamarckia cadamba (Roxb.) Bosser Clone in the South Subtropical Region of China

The present study investigated the adaptability and growth of a fast-growing clone (BN1) of N. cadamba planted as short-rotation plantation species in the south subtropical region of China, using 17 sampled sites representing different environments, planting models and ages, and local weather station temperature records. BN1’s growth characteristics were further compared with the most productive eucalypts planted nearby. The survival of BN1 seedlings raised and transplanted with tissue-culture micro-cuttings was >94.0% in the 1st year, and the percentage of the effective trees with diameter at breast height ( Dbh ) ≥ 8 cm was >71.0% over 30-month old. Most of the sampled sites and trees were susceptible to low-temperature or frost injury in the 1st winter, with average damage index ( Id ) ranging from 0.1 to 2.6. Some sites/trees were infected by caterpillar or borer pests, but the damage was neglectable. The injured trees quickly sprouted out leading shoots and recovered their growing vigor from low temperature or insect damage. Temperature factors were closely related to Id (P °C) with risk of significant frost damage on BN1 trees; one site (No. 9) was not suitable with frequent and heavy cold damage ( Id =2.6 ). BN1 grew extremely fast, with average diameter at breast height ( Dbh ) ranging from 14.5 - 20.3 cm and average tree height ( Ht ) from 12.3 - 16.0 m at 54-month old, and Dbh from 17.8 - 22.7 cm and from 14.4 - 15.9 m at 66-month old, over different sites/soils and planting models. Peak for both Dbh and Ht appeared in the 2nd year, but after 6-year old for average individual tree volume ( Vt ). BN1 was faster in Dbh at most sites but slower in Ht at all sites than eucalypts compared. Some sampled sites of BN1 performed similarly as or obviously better than most productive eucalypts in stock volume (Vs). With properly planting density, tending and rotation, BN1 could be expected to outperform fast-growing eucalypts in terms of Dbh , Vt and Vs, and to produce all diameter grades of timbers if the rotation age is extended beyond 8 to 9 years. Discussion was also given to potential silvicultural models, risks and limitations of planting BN1 and other superior N. cadamba varieties.