Trail Guide to NATL’s Upland Pine Nature Trail
(advanced version, 20 July 2007)
Controlled burns: Since the start of restoration, in 1995, NATL’s public-area upland pine has been burned seven times. The most recent burn was in March 2007.
Caution: If you wander from the trail through the partially restored upland pine, you will encounter many unfriendly plants. Most of these have thorns (catbrier, blackberry, Devil’s walking stick, Hercules club) but some have nettles (tread-softly) or toxins (poison oak).
Points of interest: Along this trail are 25 numbered points of interest that are explained below. Each is marked with a white plastic stake with two green bands at top. The uppermost green band bears a number keyed to the numbered explanations on this sheet. [All other stakes, white plastic or otherwise, are for other purposes!]
UP 1. Unrestored and partially restored upland pine. The trail that goes west from here (toward 34th Street) serves as a fire lane and divides what was once a continuous upland pine ecosystem into two blocks. The restoration of the block to the south began in 1995; the block to the north will not be restored. The woods north and south of the trail were the same in 1995. How do they differ now?
UP 2. Grass stage longleaf pines [two; marked with fire-orange flags]. The bud of the seedling longleaf pine remains in the ground for 4 to 8 years, or even longer, with only the long needles showing--resembling a clump of grass. In a fire the needles may burn but the bud survives and puts forth new leaves (as the flagged ones have). Longleaf pines can survive a fire as early as the year after germination. Other pines take much longer to become fire tolerant, or never do.
UP 3. Rocket stage longleaf pine [marked with a fire-orange flag]. After 4 or more years in the grass stage, young longleaf pines, like this one, shoot upward propelling the terminal bud out of reach of most fires on a stem that is thick enough to survive the heat. In June 2005, here and at 47 other cleared locations, six longleaf pines were transplanted in a rough circle and their positions marked with white stakes. These “restoration islands” were designed to make it easy to monitor the transplanted pines. In July 2006, 8 plugs of wiregrass (such as the two marked with pink flags) were planted in each island.
UP 4. Mature longleaf pines and a few loblollies. Longleaf pine is the only local species of pine that can tolerate the frequent fires characteristic of upland pine ecosystems. On the other hand, loblolly pine, which is characteristic of old fields and of windfalls in hammocks, is the least fire-tolerant of the local pines. Nonetheless, during the decades that NATL’s upland pine ecosystem went unburned, some loblollies became established and grew to a fire-tolerant size. To the west and on the trail behind you the two large pines bearing one yellow band are longleafs; the two marked with two bands are loblollies. Longleaf pines differ from loblolly pines in having longer needles, fewer and bigger cones, and thicker terminal branches. Using those characteristics can you identify the other mature pines to the west and north of you?
[Hint: All but five are longleafs.]
UP 5. Southern red oak. This oak can be recognized by the distinctive “inverted-bell” shape of the bases of its leaves and by the leaves being dark-green and shiny above and pale and pubescent below. In pre-settlement north Florida, southern red oak and mockernut hickory [one is labeled farther down the trail] were the hardwoods most characteristic of the transitions between upland pine and mesic hammock ecosystems. In these transitions fire occurred often enough to exclude other hammock hardwoods but fire-free periods were occasionally long enough to allow these two species to reach sizes that could survive low-intensity fires.
UP 6. Sapling longleaf pine. This tree was among 52 transplanted in 2004 when they were 4 to 6 ft tall. Only 24 survive; the others succumbed to attacks of pine sawflies, scale insects, and unknown causes. You have already passed four survivors (one was more than 10 ft tall) and
looking south, you can see at least three others. [These were planted to partially fill the age gap in developing longleaf pines caused by a 25-year shutdown in natural regeneration of longleaf pines--caused by lack of burning.]
UP 7. Turkey oak [10 ft from trail]. After the merchantable longleaf pines were cut from this area in ca. 1940 and further fires were prevented, turkey oaks thrived and grew into an understory. However, laurel oaks soon overgrew the turkey oaks, which mostly perished from the shading. This tree (marked with yellow tape) nearly died but recovered when the laurel oaks were removed. The leaves of turkey oak resemble the sun leaves of southern red oak but are light green and shiny above and below.
UP 8. Tread-softly (Cnidoscolus stimulosus) [marked with white flags]. DO NOT TOUCH. This white-flowered plant, also called “stinging nettle,” has venomous hairs. When these are grasped or brushed against, they cause a severe burning sensation lasting as long as an hour, sometimes followed by numbness.
UP 9. Narrow-leaf ironweed (Vernonia angustifolia). This summer-blooming perennial shares its showy purple flowers with other ironweeds, from which is can be distinguished by its narrow leaves. Native to the southeastern United States, it is advertised on the Web by a nursery in California nursery for use in landscaping “sunny areas with moderate to little water.”
UP 10. Photo-station. In 1997 and 2007, at this and similar stations throughout NATL, pictures of the vegetation were taken to the north, east, south, and west. The photos in the upland pine ecosystem document the dramatic changes that have occurred during restoration and can be viewed on the Web at http://natl.ifas.ufl.edu/gridphotos.htm. For this station (“E4”) you will find photos taken in 2004 as well as 1997 and 2007.
[The photo-stations are the intersections of lines that define 50x50 meter squares throughout NATL (50m=164ft). There are 77 photo-stations in NATL-west.]
UP 11. Paleleaf woodland sunflower (Helianthus strumosus) [many plants 10 ft or more from trail]. This tall perennial herb with its intense yellow flowers is another native plant that is attractive enough and hardy enough to be sold for use in landscaping.
UP 12. Wiregrass clumps [marked with pink flags]. The large clump was planted as a plug in 1997; the two smaller ones were planted as plugs in 2004. During the March 2007 burn, the large clump was protected from the fire to allow trail-users to see unburned wiregrass. The other two clumps have re-grown but you can still see burnt stubs at the base of the near one.
UP 13. Sensitive briar (Schrankia microphylla) [marked with white flags]. When the fine, bipinnate leaves of this plant are touched, the rows of leaflets on either side of their attachments close like a hinge. Sensitive briar has spherical pink or lavender flower heads and hooked prickles along its stems and leaf axes.
UP 14. Naturally germinated longleaf seedlings [marked with fire-orange flags]. During the winter of 2005-06, longleaf pines in NATL produced an unusually large seed crop. Tens of thousands of the seeds landed on soil bared by burning and germinated naturally. A majority of the seedlings perished during the spring 2006 drought, and the controlled burn of March 2007 followed by the worst drought in many years killed most of the remaining ones. Nonetheless, more than a hundred survivors, such as these, have been located and flagged, and their fate is being followed to document what promises to be the first natural recruitment of longleafs in NATL in decades. [In this, and the remaining restoration islands on this trail, pink flags mark wiregrass slips, planted in 1997, 2006, and 2007, and white PVC stakes mark longleaf pines transplanted in 2005.]
UP 15. Vase vine (Clematis reticulata). This attractive vine has urn-shaped, pale-lavender-to-greenish flowers that convert into loose, spherical clusters of achenes. Each achene has one seed and a curling, plumose tail about 2 inches long.
UP 16. Loblolly and longleaf seedlings. In this restoration island, unlike the others you have passed, all pine seedlings near the trail were protected from fire during the March 2007 burn. This allowed seedlings of loblolly pine [green flags] to survive and improved the survival of longleaf seedlings [fire-orange flags]. What differences between the seedlings of the two species do you notice? Why would the loblolly seedlings have perished in the fire had they not been protected from it? Why would many of the longleaf seedlings have survived?
UP 17. Wild potato vine (Ipomoea pandurata). This species has heart-shaped leaves and big white flowers with lavender-to-purple centers. It belongs to the same genus as morning glories and the sweet potato. Like the sweet potato, it produces large edible roots. When roasted, the roots are said to taste like sweet potato but with some bitterness.
UP 18. Bristly greenbrier (Smilax tamnoides). The tough vines of this and other species of greenbrier (Smilax spp.) have sharp, cutting spines that demand respect when breaking a new trail through the undergrowth. [The common names of two other NATL species tell the tale: saw greenbrier and cat greenbrier.]
UP 19. Recently cut sweetgum (Liquidambar styraciflua). Soon after restoration began in 1996, most of the hardwoods that had invaded NATL’s upland pine during its more than 50 years of fire exclusion were cut. Most of those that were missed, such as this 35-year-old sweetgum (then 24), are now being removed.
UP 20. Wildlife. Animals characteristic of upland pine include squirrel tree frog, gopher tortoise, eastern fence lizard, loggerhead shrike, red-cockaded woodpecker, and fox squirrel. All but the last two occur in NATL. [You may see one or more squirrel tree frogs, if you look into the open ends of these stakes made from PVC pipe. If that fails, look into other stakes as you proceed.]
UP 21. Fire lane. You are about to cross a fire lane that was last tilled in January to prepare for a controlled burn. Circumstances for such a burn did not prove favorable until March. [Fire lanes must already be in place to obtain a permit for a controlled burn.] [The natural boundary between hammock (broadleaved forest) and upland pine is farther east.]
UP 22. Unrestored upland pine. You are now in an area that was formerly upland pine but, in order to demonstrate the effects of permanent fire exclusion, will not be restored. Note how large two of the laurel oaks (trees with blue bands) have become and how mature longleafs pines (trees with yellow bands) rise above them--demonstrating that the area was once favorable to longleaf reproduction. [The healed wound around the trunk of the large laurel oak to the west is from an attempt to kill it by girdling, prior to the exclusion of this area from the upland pine restoration.]
UP 23. Hurricane downed longleaf pine. Hurricanes Frances and Jeanne, in September 2004, felled this tree. About 65 annual growth rings can be counted in the cut end of the trunk about 7 ft from the base of the downed tree. This suggests that the tree was a sapling of about 7 ft in1939, approximately when the large longleafs in the area were last cut for timber.
UP 24. Evidence of 1996 fire. As part of the tract originally designated for restoration to upland pine, this area was burned in April 1996, killing many small laurel oaks and damaging larger ones. Shortly afterwards it was converted to a no-burn area (UP 22). Some effects of the 1996 fire are still evident: First note the fire scar, now 11 years old, at the base of the laurel oak marked with one blue band. Now note the remains of a smaller laurel oak, marked with two blue bands, that was killed but lives on in the form of two root shoots. Finally, note the four small trees marked with blue flagging that are the thriving root shoots of a long-gone, fire-killed laurel oak. Laurel oaks are fire-susceptible but have their ways of fighting back.
UP 25. End of Upland Pine Nature Trail. The start of the Hammock Nature Trail is 15 feet to the right. The start of the Upland Pine and Old-Field trails is about 500 ft due north (via the trail in front of you).