Abstract
P. elliottii var. elliottii is an important timber species native to the lower coastal plain within the southeastern USA. Because of its rapid early growth and its production of highly valuable wood products, it has been widely introduced into other countries. As an exotic, it is used in Africa, especially in southern Africa, and in Australia and South America for various products ranging from lumber to pulpwood. In Brazil, it makes an important contribution to the resin production industry. The preferred method of regenerating P. elliottii is by clearcutting followed by chemical or mechanical site preparation, then direct seeding or planting of nursery stock. Although natural regeneration by seedtree, shelterwood, or group selection is an option, availability of genetically superior stock usually makes planting the favoured method of regeneration. Rotation lengths vary according to product objective. The optimum pulpwood rotation is about 25 years. In unthinned plantations, this age increases to 30 from 23 years as density increases and site index declines. South Florida slash pine (P. elliottii var. densa) is characterized by a grasslike, almost stemless stage, that lasts for 2 to 6 years. Variety densa has a small range, a less desirable tree form than var. elliottii, and is more difficult to regenerate. P. elliottii is particularly susceptible to fusiform rust (caused by Cronartium fusiforme) and is frequently attacked by the southern pine bark beetle (Dendroctonus frontalis). The best protection against insect attack is to maintain vigorous, healthy stands through good forest management. The wood is used for a wide variety of products. Markets and size and quality of the material determine whether it is used for sawlogs, veneer logs, poles, pilings, posts, pulpwood, particle board, or chip-n-saw logs. The straightness of the bole makes P. elliottii particularly suited for poles, pilings, and solid-wood products. Although it may often grow more slowly than P. patula and P. taeda, it can produce higher pulpwood yields due to its higher wood density. P. elliottii yields the best quality and highest quantity of commercial turpentine of all American pitch pines (Streets, 1962). However, this use has declined significantly as other sources of resins have become more readily available.
Growth, morphological traits and mycorrhizal colonization of fine roots respond differently to nitrogen addition in a slash pine plantation in subtropical China