Bankhead National Forest, AL   Jess Riddle
  Jan 01, 2006 09:18 PST 

A few weeks ago, Will Blozan and I visited two impressive hardwood
forests sites within the Bankhead National Forest (NF). Located in
northwestern Alabama, the Bankhead NF occupies approximately 180,000
acres of the Cumberland Plateau's southern end. Erosion of the
Plateau's sandstone and limestone by numerous small streams has left a
highly dissected landscape with broad, flat-topped ridges, and narrow,
cliff lined hollows or box canyons. Those canyons and their
associated waterfalls have made the Bankhead's Sipsey Wilderness one
of the best-known wilderness areas in the southeast. Fields, tree
plantations, and abandoned agricultural land occupy much of the
flatter surrounding landscape

(http://gorp.away.com/gorp/resource/us_national_forest/al_bankh.htm).

The canyons, with their cool moist microclimates, offer many organisms
a refuge from the region's hot summers. Eastern hemlock reaches the
southwestern limits of its range in the canyons, and the low wind
environment allows the usually uncommon bigleaf magnolia (Magnolia
macrophylla) to maintain the largest simple leaves in temperate North
America, frequently over two feet long. The overhangs and wet cliffs
at the top of the gorges also provide habitat for several rare
herbaceous species, and have sheltered humans for thousands of years.

flint_creek_sugarberry.jpg (70850 bytes) Flint Creek Sugarberry - photo by Will Blozan

We first visited West Flint Creek. One of the larger streams flowing
north out of the Bankhead NF, moderate slopes rather than shear cliffs
flank the watercourse although low bluffs of eroded limestone still
protrude from the lower slopes. Sandstone, which occasionally formed
smaller outcrops, supported much of the curving, generally northwest
facing, 200' high slope we roamed. The aptly named walking fern
(Asplenium rhizophyllum) clung to the sandstone boulders, and
overlooked allegheny spurge (Pachysandra procumbens), the site's
primary evergreen herbaceous species. Red buckeye (Aesculus pavia)
formed sometimes-extensive colonies in the understory under a largely
oak and hickory dominated canopy. Sweetgum, tuliptree, basswood,
florida maple (Acer barbatum), and locally beech also commonly reached
the canopy. Shagbark and pignut were the dominant hickories while
white was likely the most common oak.

A surprisingly broad floodplain with mature bottomland hardwoods also
bordered the stream. American bladdernut and river cane grew in
patches below tuliptree, sweetgum, sycamore, bitternut hickory,
sugarberry, and patches of cottonwood and loblolly pine. Sweetgum and
tuliptree appeared to achieve similar growth rates in the floodplain
as on the slope.

Species Cbh Height
Ash, Green 8'9.5" 119.3'
Basswood, White 5'7" 121.9'
Basswood, White 9'6.5" ~125'
Blackgum 6'0" 114.5'
Cherry, Black 5'5.5" 105.1'
Cottonwood 14'2" 124.7'
Cottonwood 8'11" 132.5'
Cottonwood 6'10" 133.8'
Cottonwood 10'10" 136.7'
Cucumbertree 5'2" 112.4'
Cucumbertree 7'11" 112.6'
Hickory, Bitternut 7'10" 114.0'
Hickory, Bitternut 6'3" 120.4'
Hickory, Bitternut 6'4" 126.9'
Hickory, Pignut 6'11.5" 133.2'
Hickory, Shagbark 6'5" 131.2'
Hickory, Shagbark 5'0" 133.0'
Hickory, Shagbark 6'10"         139.9'
Honeylocust 5'5" 97.1'
Honeylocust NA 102.0'
Hornbeam, American 3'5" 62.6'
Maple, Florida 6'6" 97.8'
Maple, Florida 4'10" 107.8'
Maple, Florida 3'8" 110.0'
Maple, Florida 5'5" 114.8'
Oak, Black 7'5" 118.3'
Oak, Chinquapin 4'3" 102.3'
Oak, Northern Red 8'4" 127.1'
Oak, Northern Red 7'7" 132.1'
Oak, Northern Red 10'4" 137.6'
Oak, Shumard 9'9" 125.5'
Oak, Shumard 6'7" 125.6'
Oak, Shumard 9'0' 128.3'
Oak, Shumard 6'4" 137.3'
Oak, Shumard 7'9.5" 137.3'
Oak, Water 6'0" 120.8'
Oak, White 12'2" 124.8'
Oak, White 7'5" 128.3'
Pine, Loblolly 8'2" 142.8'
Pine, Shortleaf NA 118.1'
Redcedar, Eastern NA 96.3'
Sugarberry 129 97.9'
Sugarberry 7'3" 117.4'
Sweetgum 7'2" 133.0'
Sweetgum 5'7" 136.7'
Sycamore 7'3" 120.6'
Sycamore 5'2" 134.6'
Tuliptree NA 128.6'
Tuliptree 7'3" 136.4'
Tuliptree NA 138.1'
Tuliptree 7'0" 138.7'
Tuliptree NA 139.7'
Tuliptree 7'7.5" 139.9'
Tuliptree NA 144.7'
Walnut, Black 7'3" 113.7'
Walnut, Black 6'4" 117.1'
Walnut, Black 5'8" 118.4'


Rucker Index 137.2'

Tuliptree 144.7'
Loblolly Pine 142.8'
Shagbark Hickory 139.9'
Northern Red Oak 137.6'
Shumard Oak 137.3'
Sweetgum 136.7'
Cottonwood 136.7'
Sycamore 134.6'
Pignut Hickory 133.2'
White Oak 128.3'

For all of those species, ENTS had no height records for Alabama, or
only had records from the preceding day. The blackgum height is
comparable to other heights in the region. 

flint_creek_ottonwood.jpg (68193 bytes) Flint Creek Cottonwood - photo by Will Blozan

The Cottonwood is now the
tallest known in the east by 0.7'. Cottonwoods growing in
approximately 100 year-old forests in the southeastern piedmont
consistently reach 133 to 137'; similar heights have also been found
in Missouri, Michigan and New York. The shagbark hickories are about
10' short of the greatest height they are known to reach, but all of
the sites with taller individuals have more topographical relief and
shelter from winds. ENTS has a paucity of data on honeylocust, but
this tree is similar in height to honeylocusts recently measured in
Tennessee. The florida maples at this site shatter the previous ENTS
height record of 94.4'. The shumard oaks approach the tallest ENTS
has thus far documented, and all taller individuals have grown on
floodplain sites. The redcedar also easily surpasses the previous
eastern height record, an 89.7' tree in Tennessee. The tree grows on
a small limestone bench near the creek. The calcium rich substrate,
low statured forest immediately upslope, and the reliable water supply
offered by the location seem nearly ideal for the species. The
sugarberry was also a new eastern height record at the time it was
measured. The range of heights in the Rucker Index is remarkably
small, and suggests the tallest species do not have height-based
niches at the site.

indian_omb_hollow_rock_shelter.jpg (60260 bytes)

Indian Tomb Hollow shelter - photo by Will Blozan

 indian_tomb_hollow_rock_shelter2.jpg (66592 bytes)


With the light already waning, we left West Flint Creek and headed for
the forests of Indian Tomb Hollow. A long, bumpy, dirt road; a low
gap; and a surprisingly gentle slope permitted access to the hollow.
Opposite the gap, sandstone cliffs, perhaps 60 feet high, clearly
demarcated the far side of the hollow. Mountain laurel, big leaf
snowbell (Styrax grandifolia) and chestnut oak grew at the foot of the
cliff. White oaks, chestnut oaks, northern red oaks, hickories and
beech constituted much of the overstory, and patches of bigleaf
magnolia grew prominently in the midstory. Moving up the hollow, the
stream forked repeatedly, and continuous cliffs loomed along both
sides. After two months of drought, only a trickle of water flowed
over the shelf-like overhang at the top of the canyon. However, the
influences of the greater water availability and maximized sheltering
clearly contributed to the occurrence of the tallest forest at that
location.

tall_chestnut_oak_ith.jpg (63448 bytes) Tall Chestnut Oak, Indian Tomb Hollow - 
photo by Will Blozan

Species Cbh Height
Cucumbertree 8'9" 115.2'
Magnolia, Bigleaf 4'0" 83.3'
Magnolia, Bigleaf 3'1" 83.8'
Maple, Florida 8'7" 96.4'
Oak, Chestnut 7'11" 136.5'
Oak, Chestnut 7'5" 141.8'
Oak, Swamp Chestnut8'7" 119.5'
Oak, White NA 129.9'
Sassafras 2'8" 87.5'

The bigleaf magnolias approach the heights ENTS has found for the
species in Georgia. The box canyons hold great promise for many more
large and tall bigleaf magnolias. 

florida_maple_indian_tomb_hollow.jpg (73879 bytes) Florida Maple, Indian Tomb Hollow 
- photo by Will Blozan

The florida maple is a semi-open
grown specimen on an adjacent slope outside the canyon. The chestnut
oaks grow adjacent to the large overhang at the upper end of the
hollow. They benefit from local maxima of both sheltering and water
supply. The physiological effects of that environment might be seen
in that the height of their branching coincides with the top of the
cliffs. The taller of the two comes within two feet of the greatest
height ENTS has found for this heavily sampled species.

We would like to thank Dr. Larry Brasher for his efforts in organizing
the trip and aid with species identification and Lamar Marshall, head
of the environmental group Wild Alabama, for his excellent guidance
through the sites. Within the past few years, Wild Alabama identified
these areas of unusually mature hardwood forest and took some
preliminary core samples.

Jess Riddle & Will Blozan