Pinus elliottii, commonly known as slash pine, is a conifer tree native to the Southeastern United States. Slash pine is named after the "slashes" – swampy ground overgrown with trees and bushes – that constitute its habitat. Other common names include swamp pine, yellow slash pine, and southern Florida pine.
It may be distinguished from the related loblolly pine (P. taeda) by the somewhat longer, glossier needles and larger red-brown cones, and from longleaf pine (P. palustris) by the shorter, more slender needles and smaller cones with less broad scales.
Two varieties of P. elliotii are described, but recent genetic studies have indicated that the varieties may not be more closely related to each other than they are to other pines in the Southeast. If this is the case, reclassifying these varieties as separate species would be warranted. P. elliottii can hybridize with P. taeda, sand pine (Pinus clausa), and P. palustris.
thumb|Pinus elliottii cones
The two commonly accepted varieties are the following:
- P. e. var. elliottii (typical slash pine) ranges from South Carolina to Louisiana, and south to central Florida. Its leaves occur in bundles, fascicles of twos and threes, mostly threes, and the cones are larger, .
- P. e. var. densa (South Florida slash pine, Dade County pine) is found in the pine rocklands of southern Florida and the Florida Keys, including the Everglades. Leaves are nearly all in bundles of two, with longer needles. The cones are smaller, , the wood is denser, and the tree has a thicker taproot.
Range and habitat
Communities dominated by slash pine are termed "slash pine forests". Slash pine is predominately found in Florida and Georgia, and extends from South Carolina west to southeastern Louisiana, and south to the Florida Keys. It is common in East Texas, where it was first planted at the E.O. Siecke State Forest in 1926. The natural habitat is sandy subtropical maritime forests and wet flatwoods. When European settlers arrived in the New World, they brought new diseases that severely diminished the Native American populations. Over time, with the lack of consistent burning, much of the open land of the South reverted to forest land. Despite many reports from the U.S. Forest Service about the benefits fire has on forage production, pine regeneration, control of tree pathogens, and reducing risks of wildfires, controlled burning did not begin to regain traction until the 1950s and 1960s.
thumb|334x334px|Controlled burn in a slash pine forest
Uses
Without regular fire intervals in slash pine forests, the ecosystem can change over time. For example, in the northern range for slash pine, forests can convert from mesic flatwoods to denser mixed-hardwood canopies with trees such as oaks, hickory, and southern magnolia. In South Florida, the pine rocklands can convert to a rockland hammock dominated by woody shrubs and invasive plants. Invasive species are a major management issue in the South. Many pine trees and native plants are adapted to fire, meaning they require fire disturbance to open their pine cones, germinate seeds, and cue other metabolic processes. Fire can be a good management strategy for invasive species because many invasive plants are not adapted to fire. Therefore, fire can eliminate the parental plant or reduce seed viability. Controlled burning is also used to help reduce pathogen load in an ecosystem. For example, fire can eliminate pest populations or resting fungal spores that could infect new seedlings. Low-intensity burns can also clear space in the understory and provide nutrient pulses that benefit the understory vegetation.
Fire is also used to prevent "fuel" buildup, the highly flammable plants such as grasses and scrub under the canopy that could burn easily in a wildfire. Most prescribed burn intervals are about every 2–5 years, which allows the ecosystem to regenerate after the burn. Much of the South Florida pine rockland ecosystem is highly fragmented and has not been burned because of the proximity to buildings.
thumb|Example of fusiform rust symptoms on pine tree bark
Rust pathogens are difficult to manage because of their complicated reproductive lifecycles. C. querecuum f. sp. fusiforme is heteroecious, requiring two different plant hosts for reproduction, and is macrocyclic, meaning it contains all five spore stages typical for rust infections: basidiospores, teliospores, urediniospores, aeciospores, and spermatia. Oak trees are the secondary host for this pathogen. The primary inocula on pine are basidiospores, which infect the pine needles between March and May. The basidiospores germinate and grow into the stems of the tree where the fungus can overwinter for 4–6 months in the wood. In the fall, the spermatia form and fertilize the aeciospores in the following spring. The aceiospores are released from the pine and are the primary inocula that infect the oak trees in the following growing season. Aceiospores grow through the oak leaves producing urediniospores on the underside of the oak leaves. These urediniospores can reproduce clonally, asexually, and can continue to infect oak plants as a secondary inoculum. Within two weeks of the primary urediniospore inoculation on the oak tree, teliospores are formed which germinate into basidiospores that infect the pine trees and complete the life rust cycle. Symptoms on the pine include gall formation, stem swelling, cankers, bushiness, and dieback. These site preps, while desired, cause increased rapid growth of pines. When this happens the outer layer of bark is thin enough for fusiform rust to infect and often it will be the main stem. When loblolly pine reach around the age of eight years old you can use more fertilization and forest prescriptions because at this time fusiform rust is not as likely to infect the main stem. Due to oaks being the alternate host for fusiform rust, where it lives out three of its spore lifecycles, it is a good idea to remove any hardwoods that are adjacent to your loblolly stand. Many reports describe the pathogen as endemic to Florida, likely because the disease was introduced a long time therefore the population has become more diverse. By 1974, over half of the slash pine population in Florida was infected with Fusarium circinatum disease. In areas where the pathogen is newly introduced, the fungal population is mostly clonal, because fewer mating types are present within the population,
Uses
This tree is widely grown in tree plantations. It is also used in horticulture. It is hardy to USDA zones 7a-11.
See also
- Southern yellow pine