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NB66: “Not Burned Since 1966”

NB-66_1967

nterior view of NB66 from a ridge near the center, looking southeast early fall 1967.

Interior view of NB66 from the same location, looking southeast  late summer 2010.

nterior view of NB66 from the same location, looking southeast
late summer 2010.

Purpose of Study

In the 1960s, the thinking of the day about forest succession in the southeast was that upland pines were a transitional forest community and in the absence of fire would give way over time to distinctive hardwood elements. Succession would logically proceed towards some end point that was called “climax” where forest conditions would become very stable and be characterized by a specific suite of tree species. NB66 was seen as a means to test the prediction that succession of upland pine-dominated forest will proceed toward hammock vegetation dominated by southern magnolia (Magnolia grandiflora) and American beech (Fagus grandifolia) in the absence of fire. The stated purpose was, “To determine what happens during plant succession on upland sites, a 22-acre area was set aside…with the avowed purpose of protecting it from fire for over 100 years (Komarek 1977).” “The stand, called NB66, is to be kept fire-free indefinitely, starting in 1967, in order that vegetational changes in response to fire exclusion may be documented” (Clewell and Komarek 1975: I). To date, only very few M. grandiflora seedlings and F. grandifolia have been located on NB66.

Photo series: 1966-2007 on NB66 at plot marker A4.
1967

1967

1981

1981

2001

2001

2003

2003

2007

2007

NB66 is located on the north-central portion of Tall Timbers Research Station in section 15, T3N, R1E of the Tallahassee Meridian, between the Georgia-Florida line and County Road 12 to the south. (Clewell and Komarek 1975). It is roughly 8.6 ha (22.3 ac) in size and divided into a grid of 48-30×60 m units. Labeled concrete posts were established at each grid node. Additional wooden posts are regularly interspersed throughout the plot for mammal sampling.

NB66-layout-1966

For fire control plots, five (30 x 60 m; 0.18 ha) plots were established in the annually burned pineland immediately to the south of NB66; NC1, NC2, NC5-1, NC5-2, and NC7. These are currently burned on a two-year rotation and only limited work conducted in them.

Land Use History

“Increment borings of the larger pines on NB66 show that the present vegetation dates to the time when fields of the region [went] fallow shortly after the Civil War” (Clewell and Komarek 1975:7). We assume that most of the plot was under cultivation before the Civil War. “Many of the larger pines on NB66 were harvested in conjunction with the war effort in the early 1940s. Only trees of about 35 cm dbh were removed…” (Clewell and Komarek 1975:9). Some of the east end of the plot was in crops until 1957. A small field in the southeast corner was inadvertently harrowed in 1967.

Fire History

According to Leroy Collins, annual fires were set on NB66 since at least 1935. Traditionally, the pinelands were burned during late February and March, at the close of the hunting season. The final prescribed fire on NB66 was conducted on March 23, 1967. It was an exceptionally clean burn, in that “all leaf litter and low-growing vegetation was consumed” (Clewell and Komarek 1975:9).

Soils

“Soil samples were taken with an auger one meter to the southeast of each post, except at those posts numbers A1 through I1, where the sample was taken one meter to the southwest.” (Clewell and Komarek 1975:10). “The soil series predominating on NB66 is Ruston fine sandy loam.” (Clewell and Komarek 1975:14). Ph, percentage of organic matter, and amount of phosphorous and potassium were also determined. Some follow-up soil sampling has been accomplished by Dr. Kevin Robertson, Fire Ecologist.

Trees

Species identity and diameter at breast height of all trees > 5 cm were recorded on maps (Clewell and Komarek 1975:11). Snags, stumps, and logs were also located. Cores were taken from 50 pine trees. The oldest tree was a slash pine of 106 years, a seedling in 1861. It also had the largest diameter (77 cm) and greatest height (34 m) of the 50 pines sampled on this research area (Clewell and Komarek 1975:19). During 1977, Tobi (1977) resurveyed the trees based on the original maps.

In 2010, Dr. Clewell again censused the plots and found that the total basal area had increased from 12.6 m2/ha in 1966 to 24.2 m2/ha in 2010 (Table 1). An additional 13 species of trees are found there today that did not occur on the unit in 1966 (Table 2).

Table 1. Relative basal area change from 1966 to 2010 on NB66, Tall Timbers Research Station.
Data courtesy of Dr. Andre Clewell.

Species
1966
2010
Acer rubrum
0.0
0.1
Carya glabra
0.0
0.0
Carya tomentosa
0.0
0.2
Cornus florida
0.6
2.3
Diospyros virginiana
0.1
0.0
Ilex opaca
0.0
0.0
Liquidambar styraciflua
1.7
5.3
Malus angustifolius
0.0
0.1
Morus rubra
0.0
0.0
Nyssa sylvatica
0.3
0.3
Osmanthus americanus
0.0
0.0
Ostrya virginiana
0.0
0.0
Pinus echinata
37.8
26.1
Pinus elliotti
5.5
1.7
Pinus palustris
5.9
2.3
Pinus taeda
35.9
20.1
Prunus americana
0.0
0.0
Prunus serotina
0.7
9.8
Quercus alba
0.0
0.7
Quercus falcata
0.7
1.5
Quercus hemisphaerica
0.9
2.1
Quercus laurifolia
0.0
0.0
Quercus nigra
3.0
24.3
Quercus stellata
0.4
0.3
Quercus virginiana
6.4
2.5
Sassafras albidum
0.0
0.2
Vaccinium arboreum
0.0
0.0
Total
100.00
100.00
Dr. Andre Clewell shows the only American beech (Fagus grandifolius) to become established on NB66 to date.

Dr. Andre Clewell shows the only American beech (Fagus grandifolius) to become established on NB66 to date.

Table 2. Native trees found in 2010 that were not present in 1966. Data courtesy of Dr. Andre Clewell.

Species Numbers Found
Ilex opaca common, even aged
Ostrya virginiana colony
Magnolia grandiflora ca. 25, even aged
Acer saccharum floridanum 1
Carpinus caroliniana 1
Fagus grandifolius 1
Fraxinus americana several
Morus rubra 1
Osmanthus americanus several
Prunus americanus 1
Quercus laurifolia several
Quercus michauxii 1
Celtis occidentalis 1in upland

Groundcover Vegetation

“Vascular plants were collected at frequent intervals throughout the growing seasons of 1966 and 1967 on NB66 and in 1968 in the control plots.” (Clewell and Komarek 1975:10). Data on non-arboreal vascular plants were collected in 89, meter-square quadrats taken at random in June 1966. In November 1966 an additional 171 quadrats were taken (Clewell and Komarek 1975:13). A total of 213 species of vascular plants were identified from NB66 and the five control plots in 1966 (Table 3) (Clewell and Komarek 1975:16). In 2010 the numbers had declined to 126 and of those five were alien species (Tables 3 and 4). Species composition had also changed with an additional 21 species showing up by 2010 that were not present in 1966 (Table 5).

Table 3. Number of species by life form found on NB66 in 1966 and in 2010. Data courtesy of Dr. Andre Clewell.

Lifeform 1966 2010
Trees 20 37
Shrubs 14 16
WoodyVines 10 11
Herbs 169 62
Total 213 126

Table 4. Number of alien species found in 2010. Data courtesy of Dr. Andre Clewell.

Scientific Name Common Name
Dioscorea sp. wild yam
Elaeagnus pungens silver thorn
Ligustrum chinensis Chinese privet
Lygodium japonicum climbing-fern
Nandina domestica Nandina

Table 5. Number of native plants found in 2010 that were not present in 1966.

Data courtesy of Dr. Andre Clewell.

Shrubs

Aralia spinosa

Ilex vomitoria

Sebastiana fruticosa

Viburnum rufidulum

Woody Vines

Ampelopsis arborea

Smilax laurifolia

Thelypteris dentata

Grasses

Chasmanthium sessiliflorum

Oplismenus setarius

Composite

Aster lateriflorus

Legumes

Desmodium floridanum

Desmodium glabellum

Desmodium nudiflorum

Ferns

Asplenium platyneuron

Botrychium biternatum

Other Forbs

Aristolochia serpentaria

Galium hispidulum

Matalea gonocarpa

Mitchella repens

Scutellaria latteriflora

Sanicula canadensis

Birds

The breeding bird community composition has changed dramatically since 1967. Pinewoods specialists, such as red-cockaded woodpecker and Bachman’s sparrow, disappeared within the first 15 years after fire exclusion (Engstrom et at. 1984). Species typically associated with more mesic conditions (e.g., wood thrush, northern parula, and hooded warbler) all were present within 15 years after fire exclusion (Engstrom et at. 1984; Landers and Crawford 1987). The birds have been sampled intermittently over the 30 years since the project was initiated. Birds were last sampled in 1996, and will be re-sampled on subsequent, 5-year intervals.

Mammals

Changes in the mammal community composition were as dramatic as those seen in the avian community. Species typical of open pinewoods (e.g., cotton rat) disappeared and species associated with mesic conditions (e.g., wood rat) appeared within 15 years of fire exclusion (Baker, unpublished data; Landers and Crawford 1987). The mammals have been sampled intermittently over the 30 years since the project was initiated. Mammals were last sampled in 2002, and will be re-sampled at irregular intervals.

Literature on NB66

  • Baker, W.W. 1967-1986. Bird and mammal data. Unpublished.
  • Clewell, A. F. 2012. Forest succession after 43 years without disturbance on ex-arable land, northern Florida. Castanea: in press
  • Clewell, A. F. and R. Komarek. Unpublished manuscript, November 1975. NB66: the initiation of the long-term experiment in forest succession. (TTRS Publications file cabinet).
  • Engstrom, R. T., R. L. Crawford, and W. W. Baker. 1984. Breeding bird populations in relation to changing forest structure following fire exclusion: a 15-year study. Wilson Bulletin 96(3):437-450.
  • Komarek, E.V., Sr. 1977. A quest for ecological understanding: the Secretary’s review, March 15, 1958-June 30, 1975. Misc. Publ. No. 5, Tall Timbers Research Station. Pp. 45-46.
  • Landers, J. L., and R. L. Crawford. 1987. NB66: a study of habitat relations of nongame birds and mammals in seres of oldfield pinewoods following fire exclusion. Final Project Report. Project Number GFC-84-004. Florida Game and Fresh Water Fish Commission, Division of Wildlife, Nongame Wildlife Section.
  • Tobi, E. R. 1977. Vegetational changes on formerly annually burned secondary pine-oak woods after ten fire-free years. M.S. Thesis, Florida State University, Tallahassee, FL.