Whittaker - Vegetation of the Great Smoky Mountains

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Vegetation of the Great Smoky Mountains

R. H. Whittaker

Ecological Monographs, Vol. 26, No. 1. (Jan., 1956), pp. 1-80.

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2/81

VEGETATION OF THE GREAT SJlOKY l l lOUSTAINS1

R

WHITTAKER

Biology Department . Brooklyn Col lege. Brooklyn

10

X

. Y

T A B L E

O F

C O N T E S T S

P A G E

In t roduct ion

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1

N a t u r e o f t h e S t u d y

. . . . . . . . . . . . . . . . . . . . . . . . . . 1

Li tera ture on Area . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 2

Geology and Climate . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Methods

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Field Transec ts and Tre e Classes . . . . . . . . . . . . . .

4

Si te -Samples and Compos i t e Transec t s

. . . . . . . . . . 6

Dis t r ibu t ions o f Spec ies a long the Mois ture

Gradien t . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8

T r en d s i n R e l a t i o n t o t h e M o i st u re G r a d ien t . . . . . .

10

Growth-Forms

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Coverages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Diversities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

10

Sizes and Numbe rs of S tems o f T rees . . . . . . . . . .

11

S e l f - M a i n t en a n ce o f S t a n d s . . . . . . . . . . . . . . . . . . . . 11

High-Elevat ion Deciduous Fores ts . . . . . . . . . . . . . . . . 13

Dis t r ibu t ions o f Spec ies in Rela t ion to E levat ion . . .

X es i c S i t e s

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Submes ic S i t es . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Subxer ic S i t es . . . . . . . . . . . . . . . . . . . . . . . . .

Xer ic S i t es

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Trends in Rela t ion to E levat ion . . . . . . . . . . . . . . . .

Growth-Forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Tree S ta tures and S t ra ta l Coverages . . . . . . . . . . . . .

Divers i ty and Environmental Favorableness

. . .

Spruce-Fir Fores ts . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Stratal Dis tr ibut ions . . . . . . . . . . . . . . . . . . . . . . . . . .

T r en d s

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Relat ions o f Species to Union s and Associat ions . . . .

C o n t i n u i t y o f V eg e t a t i o n T yp es . . . . . . . . . . . . . . . .

Nature of Species Group ings . . . . . . . . . . . . . . .

Dominance in Rela t ion to Comm uni ty Compos i t ion

Summ ary o f D ist r ibu t ional Groupings . . . . . . . . . . . .

I 1

D I S C U S S I O N : OFN I N T E R P R E P A T I O N

\ T F X 3 ~ ~ ~ ~ ~ . . . . . . . . . . . . . . . . . . . . .

ATTERNING

~

Dis t r ibu tions o f Spec ies and the S tu dy o f Genecology

T he Assoc ia t ion-Uni t The ory and Indiv idual is t i c

Hypothes i s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

T h e Dis tr ibu t ional Bas i s o f Communi ty .Types

. . . . . .

Gradat ion and the Grouping o f Spec ies . . . . . . . . .

I . G R A D I E N T A N A L Y S I S

I N T R O D U C T I O N

NATURE

O F

T H E

S T U D Y

T h e Great

Snloky

Mountains of Tennessee

and

N o r t h C a r o l in a s u p p o r t v e g e t a ti o n w h i c h i s p a r ti c u-

' 1 ~ ''''

i n s ~ e c i e s n d v a ri ed in c o m m u n i t y t y p e s

I n t h e s u mm e r o f 1947 f ield w o rk \&*as carr ied o u t

Based on a thesis Whittaker

1 9 4 8 ;

a contr~bution rom

the Department of Zoology. University of Illinois . LTrbana.

and

the Biology Department. Brooklyn College

Zonat ion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

34

Ecotones

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

36

Climax Pat terns and Their Comparison . . . . . . . . . . . . 37

Considerat ions o f Logic and Zlethod . . . . . . . . . . . . . . 40

Conclus ion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

43

111

\ T E G ~ ~ 4 T 1 0 ~ T H E I R I S T R I B U T I O N A LY P E SA X D

R E L A T I O N S. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

43

Bases o f Recogniz ing and Descr ibing Ty pe s

. . . . . . . .

43

V eg e t a t i o n T yp es o f t h e G r ea t S m o ky M o u n t a i n s

. . .

45

1

Cove Hardwoods Fores t . . . . . . . . . . . . . . . . . . . . . 45

Mixed Mesophyt ic i n the Smokies and

Cumberlands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

2. Eastern Hemlock Fores t . . . . . . . . . . . . . . . . . . . . . 48

3

Gray Beech Fores t

. . . . . . . . . . . . . . . . . . . . . . . . . 48

4 Red Oak-P ignut H ickory Fores t . . . . . . . . . . . . . . 49

5

Chestnut Oak-Chestnut Fores t . . . . . . . . . . . . . . . . 49

6. Ches tnut Oak -Ches tnut Heath . . . . . . . . . . . . . . . 50

7

. Red Oa k-Chestnu t Forest . . . . . . . . . . . . . . . . . . . . .51

8

.

Whi te Oak-Ches tnut Fores t

. . . . . . . . . . . . . . . . . .

Pine S ta nds and Thei r Nain tenance

. . . . . . . . . . . . .

9. Virg in ia P ine Forest . . . . . . . . . . . . . . . . . . . . . . . .

10. P i t ch P i n e H ea t h . . . . . . . . . . . . . . . . . . . . .

11

.

T a b l e V o u n t a i n P i n e H e a t h

. . . . . . . . . . . . . . . .

12. Grassy Bald . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

The Southern Appalachian Subalp ine

Fores t Center . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13. Red Spruce Forest . . . . . . . . . . . . . . . . . . . . . . . . .

14 Fraser Fir Fores t . . . . . . . . . . . . . . . . . . . . . . . . . .

15. H ea t h B a l d . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Th e Balds as Topographic C l imaxes?

. . . . . . . . . . . .

Distributional Relations . . . . . . . . . . . . . . . . . . . . . . .

T h e X o s a i c C h a rt

. . . . . . . . . . . . . . . . . . . . . . . . . . . .

Dis t r ibu tions o f Ty pes . . . . . . . . . . . . . . . . . . . . .

Distr ibut ion of f lubalpine Fore s ts

. . . . . . . . . . . . . .

Rela t ion of the Vege ta t ion Pat tern to Those

o f O t her V o u n t a i n R a n g es . . . . . . . . . . . . . . . . .

Suncnca~.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

LI TE RA TU RECIT ED

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

A P P E N D I X E S

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

A

. Popula t ion Char t s for Major Tree Spec ies

. . . . . .

Kote on Supplementary Publ ica t ion o f Appendixes

B and . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

f o r a s t u d y o f t h i s v e g e t a ti o n . T h e w o r k w a s o r ig i-

n a l l y i n te n d e d t o p ro v id e i n f o r m a t i o n o n t h e v e g e -

t a t i o n f o r t h e s a k e o f i t s o w n i n t e r e s t a n d a s a b a s is

f o r s t u d i es i n a n i m a l e c o lo g y ( W h i t t a k e r

1 9 5 2 )

.

A

m a j o r p u r p o s e o f b o t h th i s a n d t h e pr e ce d in g s t u d y .

h ou -e ve r. u -a s u s e o f t h e c o m p l e x p a t t e r n o f n a t u r a l

communities

in

the Great Smoky

Mountains

f o r

re-

search

into

t h e t h e o r y

comlnunity u n i t s o r a s so -

.

F~~

t h i s purpose. t h e

approachto

vegeta-

t a t io n w a s ba se d o n s a m p l i n g w i t h o u t r e g a rd t o a p -

p a r e n t a s s o c ia t i o ns a n d a n a l y s i s o f t h e s a m p l e s i n


3/81

relation to environmental gradients. I t was felt that

relative validity of vegetation types should emerge

from data impartially obtained, and that the rela-

tions of types to one another should be revealed in

the study of their populations in relation to environ-

mental gradients. The work thus depart s from the

traditional approach of studying intuitively recog-

nized types or associations; it is an experiment in

population analysis of a whole vegetation pat tern .

The first part of the monograph describes results

of the analysis in terms of relations of species popu-

lations to one another and environmental gradients,

and trends in community composition and structure

along environmental gradients. The second par t in-

terprets the vegetation as a complex pattern, within

which vegetation types may be understood through

the distributional relations of species populations.

The third part presents a more conventional de-

scription of vegetation types and considers the re-

lations of these to topography. The study as a whole

thus seeks to analyze, interpret, and describe the

complex vegetational mantle of the Great Smoky

Mountains.

LITER TURE O N RE

A series of studies by Cain deal with vegetation of

the Smokies-the heath balds (1930b), subalpine

forests (1935), and cove hardwoods (1943), floristic

affinities (1930a), soil reaction (1931), Raunkiae r

life-forms (194 5), and bryophyte unions (Cain

Sharp 1938). A number of vegetation types were

described by Cain

e t

al (1937). The grassy balds

were reported on by Camp (1931, 1936) and Wells

(1936a, 1936b, 1937); the subalpine forests were

recently described by Oosting Billings (1951) and

the beech gaps by Russell (1953). These papers and

the description in Braun (1950) are the extent of the

literature dealing specifically with the vegetation of

the Smokies. Other studies include descript ions of

Southern Appalachian vegetation types, among then1

Harshberger's report (1903) and book (19 11) , Wells

(1924) and the forestry reports of the l essage fr o m

the Pres ident

(Ayres Ashe 1902), Reed (1905),

Holmes (1911), Ashe (1922), and Frothingham

et

al (1926). Of studies in nearby areas Braun's papers

on the Cumberland Mountains-Pine Mountain

(1935b), Black Mountain (194 0a), and the Cumber-

lands (1942, 1940b)-and material in the book on

the eastern forests (1950) were most valuable for the

related vegetation of the Smokies. Other Appalachian

and eastern studies-Harshberger (1905) and Heim-

burger (1934) on the Adirondacks, Core (1929) on

Spruce Mountain, Davis (1930) on the Black hIoun-

tains, Conard (1935) on Long Island, Raup (1938)

on the Black Rock Forest, Oosting Billings (1939)

on Ravenel's Woods, Oosting (1942) on the Pied-

mont, and, particularly, Brown (1941) on Roan

Mountain-contributed

conlparative information. A

bibliography of other paper s dealing with the Smokies

is given by Mason Avery (1931) . Taxonomic ref -

erences for the area are Small (193 3), Shanks

Sha rp (1947), Gleason (1952), and Fernald (1950).

ITTAKER

Ecological Monographs

Vol. 26 No. 1

While at the University of Illinois, the author was

aided by the suggestions and criticisms of S. C. Ken-

deigh and A.

G

Vestal. The pa rk naturalist of the

Great Smokies, Arthur Stupka, gave the author the

cooperation and benefit of broad knowledge of the

mountains which he extends to students in the area.

Help with the identification of plant specimens \&*as

given by Stupka and by A. J Sharp and R.

E

Shanks, m*ho checked all determinations Responsi-

bility for statements of distribut ion, based on field

deteriiiinations, remains with the author. A number

of people have read part or all of the manuscript

and offered comments on it:

E L. Braun, H. E.

Brewer, H . K . Buechner, TIT. H . Camp, A Cronquist,

R. Daubenmire, F E Egler, H. A. Gleason,

A

R.

Kruckeberg, H

L

Mason, R. E Shanks, A.

F

Sharp,

and A. Stupka. The author is especially indebted to

mT.

H. Camp for his suggestions and for information

which permitted interpretation of genetic and dis-

tributional phenomena. Cost of publ icat~on of the

tables and charts has been met in part by a grant-in-

aid from the Society of the Sigma Xi.

GEOLOGY ND CLI X TE

The Great Smoky hlountains are part of the Blue

Ridge Province, a systein of mountains of great an-

tiquity. This pa rt of the Southern Appalachians

comprises two major ranges, the Blue Ridge proper

and the Cnaka blountains, along with their con-

necting cross-ranges (Fennem an 1938). The two

main ranges lie parallel, from northeast to ~outhwest,

with the 17nakas, of which the Smokies are part, to

the north. The drainage, north from the dlvide of

the Blue Ridge, is northwest into the Great Valley of

the Tennessee R i ~ e r , nd rivers flowng from the

Blue Ridge to the Great Valley through the ITnakas

cut the latter into

a series of segments divided by

deep gorges. The Great Smoky Mountains are the

largest and highest of these segments, between the

Little Tennessee and Big Pigeon Rivers.

The crest of the Great Smoky hlountains forms

the state border of Tennessee and North Carolina, 25-

50 miles southwest of the city of Knoxville in the

Great Valley. The range has the appearance of a

long, sinuous ridge connecting irregularly spaced

domes, with secondary ridges and hills spreading on

each side (Fig. 1 . The mountains are stream-eroded

to physiographic maturity; in form they are sub-

dued (Fenneman 1938) though rugged. Many of the

summits and ridges are rounded, and almost all the

mountain surface is covered by a mantle of soil and

vegetation. The resistant rocks have maintained high

relief in spit e of age. Sixteen peaks have elevations

above 6000 f t (1830 m) and the highest sunl n~i ts ise

more than 5000 f t above the valleys a few miles to

the north. Valleys are cut deep into the mountain

mass, with steep slopes and narrow flats. The slopes

for111 most of the area of the mountains; it has been

estimated tha t less than 10 of the surface has less

than 10 degrees of slope (Message from the Presi-

dent 1902).


4/81

anuary

1956 VEGETATION

MOUNTAINS

F THE GREATSMOKY

FIG 1 Matu re, forest-covered topog raphy of the

from Frye Mountain near Bryson City, North Carolina

tanooga, Tenn.

Most of the rocks of the mountains belong to the

Ocoee series Saf for d 1869, Stose Stose 1944, 1949,

Ki ng 1 949) of complexly folded, metamorphic sedii

mentary rocks which are resistant to erosion and

fairl y uniform in their reaction to it . Deposited in

Cambrian or late pre-Cambrian time Ke ith 1902,

Stose Stose 1949, Ki ng 19 49) ) hey were first folded

into mountains in the Appalachian Revolution of

the late Paleozoic. The mo untain s were raised

fur ther in the Cre taceous and have s ince tha t t ime

been through three cycles of erosion, the Schooley,

Ha r r i sburg , a nd p re sen t Wright 1931) . While some

higher ridges of the Smokies may remain from the

Schooley cycle of the earlier Tert iary W illis 1889,

Ki ng Stu pk a 195 0)) i t is probable tha t throughout

this the area was one of hills or low mountains Fe n-

neman 1938, Wright 1942, Braun 1950) . Afte r a

second elevation, probably in the Miocene, the moun-

tains persisted through the shorter Harrisburg cycle,

the peneplane of which may be suggested by some of

the lower ridges K in g

Stupka 1950) . The moun-

tains were again raised at the end of the Tertiary.

During the Pleistocene the Smokies were well south

of the ice sheets and possessed no glaciers; but there

are indications that climatic cooling produced a tim-

ber line on the higher summits Ki ng Stu pk a 195 0) ,

displacing forest vegetation toward lower elevations.

I t is believed, from distribu tional evidence discussed

later P ar t 111) that high-elevation forests were dis-

placed u pw ard 1000 to 1300 ft above present levels

during the warm dry period following glaciation.

Great Sm oky Mo untains , a view of the sou theast slope

.

Reproduced by permission of

W

M. Cline Co., Chat-

The southern mountains have played a great part

in the vegetational history of the Ea st Br au n 1938,

1941, 195 0). While other are as have been glaciated,

submerged, and exposed to great climatic change

Ferna ld 1931)) the Sou thern Appalachians have

offered

a

sanc tuary for many spec ies of plants and

animals. The Blue Ridge System has been con-

t inuously occupied by p lants and animals for pe rhaps

200 million years Ca in

t

a l . 1937) . During the

early Tertiary the higher elevations of the Smokies

and Blue Ridge probably supported tempera te for-

ests ancestral to those now in the area while sub-

tropical floras prevailed at sea level Ca in 19 43 ).

I t is in the Blue Ridge Province and other a reas

where the Schooley peneplane was never perfected

that most typical mixed mesophytic forests, most

closely related to the Arctotertiary forests, have sur-

vived Brau n 1950 5 0 5 ) . Du ring the cl imatic changes

to which eastern vegetation was subjected, the topog-

raphy of the Southern Appalachians offered varied

conditions of moisture and elevation in which species

of diverse climatic adaptations might survive while

sometimes destroyed elsewhere.

I t might be expected that age and maturity of the

mountains would be reflected in maturity of their

pla nt cover, as well as in antiquity of some of the

flora. Pr im ary succession is nearly completed in the

Smokies ; i t is perhaps in progress on a few peaks

and ridges, but almost all the vegetation is either

topographic climax or secondary. One of the majo r

for rs t t rees , the ches tnut Cas tanea dent a ta ) , wae


5/81


6/81

January 1956

VEGETATION

THE

GR

F

stems nere the usual sample for each of

7

to 1 0

stations. Along with the tree count the undergrowth

was recorded by a coverage estimate for each stratum

and a list of major and minor species. An example,

one of six such transects made, will show the method

and its relation to the composite transects.

On the Bullhead Trail to Mt. Le Conte, seven

sample counts nere made at intervals of 5 m from

the valley bottom to the southwest-facing slope, all

a t elevations of 3100 ft . I n the tables an additional

sample from a deep valley forest was added to the

beginning of the series, since the small valley of the

transect did not represent the extreme of mesic con-

ditions. Percentages of stand for the tree3 and oc-

currences of shrubs and herbs were arranged for the

8 stations as in Table 1 . I n analyzing transects with

relatively small samples, simple tallying of numbers

of stems fo r each species was preferred to basal-area

computation. Canopy dominance was determined

separately from larger samples.

Individual species of trees are well scattered along

the gradient, but certain loose groupings of species

may be suggested. Some species have their maximum

abundance in the deep-valley cove forest, station K

of the transect. or are abundant there and have their

TABLE

1

Bullhead field transect of moisture gradient.

Along trail from Cherokee Orchard to Mt. Le Conte, in

a small dry valley at

3100

ft and out onto adjacent

southwest slope. Trees

by

percentages of stand from

1-in. class up.

Tree species K I I1 111 IV

V

VI VII

Tsuga canadensis..

. . . . . . . . .

Halesia monlieola . . . . .

Aesculus octandra. . . . . . . . . . .

dce r saccharum . . . . . . . . . . . .

Tili o heferophylla. . . . . . . . .

Fagun grandifolio. . . . . . . .

Betula allegheniensis.

. . . . . . .

Liriodendron tulipifma. . . . . .

Magnolta acuminata . . . . . . . .

Ilez opaco . . . . . . . . . . . . .

Carye cordiformis . . . . . . . . .

Frazrnus amencana

. . . . . . . .

Cladrastts lulea

. . . . . . .

Magnolio f.asert . . . . . . . .

Acer rubrum. . . . . . . . .

Qtrncus borealis v. moz mu

Carya globra.

. . . . . . . . . .

Oslrya virginlona

. . . . . . .

Acer pensylwnvum . . . . . . .

Belula lenta . . . . . . . . . . . . .

Hamamelis mrginiona . . . . . . .

Cle lh~a c um im ta . . . . . . . . . .

Amelanchier arborea. . . . . . . .

Robrnio pseudoam .

. . . . . .

Castanea d enhta

( d e a d ) .

. . . . .

Quercus pr inus ..

. . . . . . . . . . .

Ozydendrum arboreum.. . . . . .

Nwxa xylwlico.

. . . . . . . . . . .

Sassafras altndum.

. . . . . . . .

Quercus coccineo.. . . . . . . . . .

Pinus pungena.

. . . . . . . . . . . .

Pinus r ig ido . .

. . . . . . . . .

Total stems. . . . . . . . . .

a

present at leea than

,575,

*Kalanu Flats, a cove forest

6 mi.

east of transect area, elevation 2800 ft.

maxima in the second or third stations. Bt the other

extreme are species which have their maxima in the

most xeric site, station VII, and do not extend to

sites less xeric than station VI. Between these ex-

treme groups there are a number of species with

their maximum populations in stations 111 to VI.

These might be grouped together; but they may also

be separated into two groups, one having maxima in

stations 111 and IV, extending on the mesic side to

station

I

or

I1

but not beyond V on the xeric side,

and the other having maxima in stations

V

and V I

and extending to the xeric extreme, but not beyond

I V on the mesic side. The four groups are used as

classes of trees along the moisture gradient. They

may be characterized as follows:

1

Mesics-Species with maxima in or near the

most mesic sites and with limited extent into more

xeric situations, occurring rarely in the part of the

gradient represented by oak-chestnut heath. These

species predominate in the cove forests.

2. Submesics-Species which have the ir maxima in

fai rly mesic sites, but a re uncommon or absent in

most mesic sites and do not extend to most xeric sites.

These species predominate in oak-hickory forests at

lower elevations and in red oak-chestnut forests a t

higher elevations.

3 . Subxerics--Species which have their maxima in

more xeric sites, but occur in most xeric sites only as

minor species and are absent from most mesic sites.

These species predominate in oak-chestnut heaths and

at higher elevations in white oak-chestnut forests.

4. Xerics-Species which have their maxima in

most xeric sites and have limited extent into less

xeric iit es , extending into the range of dominance of

the previous group and no further. These species

predominate in pine forests and pine heaths.

The same classes are recognized for shrub and

herb populations. Lists of species fo r each are given

in the Summary of Distributional Groupings.

The moisture gradient is one of g reat complexity;

along the gradient from stream-side to south-facing

slope and ridge many factors of soil moisture and

atmospheric humidity vary, along with exposure to

wind and insolation, and factors of temperature af-

fected by insolation and by patterns of air move-

ment. In relation to the primary gradients of en-

vironmental factors a sequence of vegetation types

and a catena of soils develop; and the composition

and physiognomy of vegetation and properties of

soils form other secondary gradients of environ-

mental factors affecting plants. The primary factors

are so modified by the presence of plant communities

that primary and secondary factors are not

really to be distinguished in their effects on plants.

At any point along the gradient the plant lives in

relation to an environmental complex of interrelated

factors of physical environment, soil, vegetation,

and animal communities; along the moisture gradi-

ent factors of each of these change. The gradi-

ent is thus a complex of factor gradients, or a gradi-

ent of environmental complexes, which, in distinc-


7/81

t ion f rom a f ac to r g r ad i cn t , may be t e rmed a

c o m -

p l e x - g r a d i e r ~ t

(Whi t t ake r 1954b) . The " e l eva t i on

grad ient" is l ikewise a complex-gradient , involving

many fac tors of phys ica l envi ronment , so i l s , and

na tu ra l communi t i e s o the r t han t empera tu re s and

growing seasons .

The complex-gradient f rom val ley bot toms to dry

slopes wil l be cal led the "moisture gradi ent ," bu t

wi th no a s sumpt ion t ha t mo i s tu r e f ac to r s d i r ec t l y

cont ro l the d is t r ibut ion of an y p la nt popula t ion a lon g

it . Jfeasurernents of all ' fac tor s of env ironm ent an d

determination of which may be most s ignif icant for

popula t ions of d i f fe rent p lant spec ies a re f a r beyond

the scope of the present work. F or the present s tud y

i t may suf f ice tha t a complex-gradient ex is t s , in re -

la t ion to which the d is t r ibut ions of p lant popula t ions

may be studied.

Such study is dependent on the defini t ion of rela-

t ive posi t ions along the grad ient . Since these could

not be de termined, f o r hundr eds of s i te -samples ,

by d i r ec t env i ronmen ta l measu remen t , app roaches

through the vegeta tion i t se l f were sought . Along the

gradient the four mois ture c lasses of t rees r i se and

fa l l in sequence , form ing a se t of cu rves f lowing

cont inuous ly in to one anothe r (Fi gs . 2 , 3 , 4 . I f , a s

is s h o ~ v ~ ly the t ransec ts , there i s progress ive sh i f t in

proport ions of t rees of different tolerances along the

gradient , then i t i s not unreasonable to tur n f r om

th i s f ac t t o i t s conve r se and r ega rd t he s ame p ropor -

t ions as express ions of pos i t ion a long the gradient .

I n the fo l lowing d iscussion, s tan ds an d s i tes wi ll be

termed

mesic , sz bmesic , subxer ic ,

a n d

xe r i c

according

to which of the moisture classes pred om inate i n stem

numbers.

SITE SAMPL ES AND COhlPOSITE TRANSECTS

The main re l iance in so lv ing the vegeta t ion pa t -

te rn was on the s i te -samples and the i r manipula t ion .

s i t e - s a m p l e

was a vegeta t ion sample f rom a re-

str icted si te of unifo rm physical habitat- the f loor of

a

valley, a s ingle hi l ls ide slope of the sam e direct ion

and inc l ina t ion, or the c res t of a r idge . I n order to

ob t a in an app rox ima te ly r andom coverage o f t he

whole vegeta tion pa t te rn , samples were take n f rom

the many t ra i l s a t a l l e leva t ions in the mounta ins .

The method was to move a long a t ra i l recording a

sample f rom each new s lope exposure , ins ide or out

of a valley, of sufficient extent to give a homogene-

ous sample. The si te-samples were in no case se-

lec ted to represent e i ther apparent vegeta t ion types

or the t rans i t ions be tween them.

The bulk of the si te-

s amples were ob t a ined f rom the moun ta ins su r round-

ing Greenbr i e r , Suga r l and , and Cades Coves i n t he

Ka t iona l Pa rk on t he Tennes see o r no r thwes t s i de

of the range .

A t each s i t e t he s ame da t a were r eco rded a s i n t he

t ransec t s ta t ions . Sample s ize var ied wi th the num-

her of t rees thought necessary to indica te s tand com-

posi t ion: f i f ty were suff icient in some stands with

one or two dominants , but most counts inc luded about

100, while 200 or 300 were tal l ied f o r some mixed

types . The dense smal l s tems of Rhod odendron


Vol.

26,

No.

th icke ts were not counted in fores t s where they oc-

curre d. T he 25,000 stems recorded in 300 si te-samples

were the to ta l sample ana lyzed for the vegeta t ion

pa t t e rn .

Exact lng phytosocio logica l ana lys is of the under-

g rawth mas no t an ob jec ti ve. I n fo rma t ion on sh rubs

is la rge ly l imi ted to presence and s t ra ta l dominance ,

t h a t

on

herbs to visible presence a t the t ime of sam -

pl ing . S t ra t a l coverages a re es t imates , in tended only

to permi t cornpar i sons be tween d i f ferent s tands in

t h e S m o k ie s. A t 1 5 s a m p le s t at io n s f o r a n o t h e r s t u d y

(W hi t t a ke r 195 2) l oca ti on and coverage of i nd iv idua l

p l an t s we re mapped i n quad ra t s 10m squa re .

The s i te -samples were ma nipu la ted in severa l ways .

By compar ing s e r i e s o f t hem f rom nor th and sou th

slopes or other exposures, the al terne effect on vege-

ta t ion could be de termined, a method found par t icu-

larly effect ive at high elevat ions where al terne effects

are more conspicuous in undergrowth than canopy.

G r o u p s o f s a m p le s f r o m s it es w ~ t h i m i la r m o l s tu r e

condit ions within l imited ranges of elevat ions were

compi led in to composi te s tand counts . These counts ,

u s ua ll y f o r a b o u t 1 0 0 0 st em s , c o m p e n s a t ~ d o r t h e

s lna l l s ize of the s i te -sample counts and were used

fo r t he cha rac te r i za ti on o f vege ta t ion t ypes ( P a r t

111 ) . Da t a f rom the s l te - samples were a r r an ged i n

mosaic form on a char t wi th e leva t ion and topo-

graphic s i tes as axes , to show dis t r ibut ion? of spec ies

2nd vege ta t ion t ypes i n r e l a ti on t o e l e v~ t io n and

t o p o gr a p h y ( P a r t 1 1 1 ) .

The site-samples were, f inal ly, arr ang ed in

c o m -

pos i t e t ranse c t s

in te rms of e leva t ion , or of topo-

grap hic s i te , or of mo is ture condi tions as indica ted

hy the vegeta tion i t se l f. F o r the e leva t ion t ransec ts

come means of c om pa rin g sta nd s of equivalent mois-

ture condit ions at different elevat ions was needed.

The si te-samples were consequently classif ied into

fo ur group s , according to which of the m ois ture

c las ies of t rees was predonl inant in a g iven sample .

TT1thin each of the four classes of s tands, the si te-

samples were grouped by 200- and 300-f t in te rva ls .

F ou r compos it e t r ansec t s we re t hus a r r ang ed t o cove r

thc whole of the vegeta tion pa t te rn , showing the

change in leve ls of p lant popula t ions f rom low e le-

va t ions to h i& in each of the fou r classes of s tands

and si tes recognized.

A more sens i t ive indica t ion of re la t ive pos i t ions

a long t he mo i s tu r e g r ad i en t i s pos s ib l e t h rough the

use of

w e i g h t e d a v e r a g e s

as indica tor va lues (c f .

El lenberg 1948, 1950, 1952, Cur t i s McIntos h 1951,

w h i t t a k e r 1 9 5 4 b ) .

I n a g i ve n s t a n d t h e n u m b e r

of s tems in each moisture class is mult ipl ied by a

we igh t ( 0 fo r mesi cs , f o r submes ic s, 2 fo r sub -

xer ics , 3 f o r xer ics ) , a nd the to ta l of weig ~ted s tem

numbers i s d iv ided by the to ta l number of s tems.

Within elevat ion bel ts (1500-2500, 2500-3500, and

3500-4500 f t ) t ,he s i te-samples were ar ran ge d in se-

quence f rom most mes ic to most xer ic by these

we igh t ed ave rages , and were t hen g rouped fo r t abu -

l a t ion i n t, o 1 2 o r 1 3 s t eps a long t he g rad i en t . Th i s

method of , a r ra ngin g the t ransec ts involves an evi -


8/81

anuary,

1956 VEGETATION TIIE

~ ~ O U N T A I N SF GREAT

SMOKY

t l en t c i rcu la r i t y ; d i s t r ibu t ion of t ree spec ies i s s tud ied

in t e rms of prev ious ly de t ermined d i s t r ibu t iona l

c l asses of t hese sa i ii e t ree spec ies . The a pp ro ac h i s

based , however , on the objec t ive d a t a of t h e f ie ld

t r ansec t s ; and t he pa t t e rn s o f spec i e s d i s t r i bu t i ons

a re e i i en t i a l l y t he s am e i n t he f i e l d t r an sec t s and

composi t e t ransec t s .

O t he r com pos i te t r an se c t s w e re m ade fo r e l evat ions

nhove 4500 f t i n suba l p i ne o r sp ruce - f i r fo re s t s, a nd

i n h i gh -el eva t ion dec i duous fo re s t s ou t s i de t he r an ge

o f sp ruc e and f i r. I n t he se the s am p l e s w e re g roup ed

by t opog raph i c pos i t i on r a t he r t han by w e i gh t ed

ave rages . T he va r i ous com pos i t e t r an sec t s w e re de-

s i gned t o fo rm a g r i d cove r i ng t he w ho le o f t he yege -

t a t io n p a t t e r n o f t h e G r e a t S m o k y M o u n t a in s . T h e

fo l lowing sec t ions wi ll d i scuss d i s t r ibu t ions of p l a n t

popu l a t i ons and t r ends i n com m un i t y com pos i t i on

show n by these t ransec t s . The whole body of t ab l es

can not be publ i shed here . Two tab les hav e a l rea dy

b ee n p u b li sh e d ( W h i t t a k e r 1 9 5 1 ) , a n d t h e o t h e r

t a b le s f o r t r e e p o p u l a t i o n s a r e p r e s e nt e d h e r e ( w i t h

extens ion of e l eva t ion in t e rva l s f r om

200

t o 4 00 f t

i n t ab l e s 5 and

6 ) .

T he fu l l se t o f t ab l e s fo r t r e e

popu l a t i ons a nd unde rg row t h spec ie s a r e ava i lab l e

t o t hose de s i r i ng t hem ( see N o t e on S up p l en i en t a ry

P ub l i ca t i on )

TABLE2.

Composite transect of moisture gradient between

2500

f t a n d

3500

f t , dist r ibut ion of t rees along gradi -

en t. Transect along the moisture grad ient fr om mesic valley si tes ( Sta .

1 )

to xeric southwest slope si tes (Sta.

13),

based on 67 site counts including 6122 stems from elevations between

2500

and

3500

ft . All figures are percentages

of tota l stenis in stat io n fro m 1-in. diameter class up.

Tree species

1 1

Ac er sp i c a tum . . . . . . . . . . . . 4

Frax inus ame r ic ana . . . . . . . .

2

Tilia heterophylla

. . . . . . . . . . .

17

Aesculus octandra

. . . . . . . . . .

7

Fagus grandi fo l ia

. . . . . . . . . . 1

Acer saccharum . . . . . . . . . . . .

6

Magno lia ac um ina ta . . . . . . .

x

Zlex opaca . . . . . . . . . . . . . . . . . .

Prunus se ro t ina

. . . . . . . . . . . . .

T suga c anade mis

. . . . . . . . . .

25

Betula allegheniensis . . . . . . . .

26

Lir iodendron tu l ip i fera

. . . . . .

2

Halesia monticola . . . . . . . . . . 5

Magnolia fraseri

. . . . . . . . . .

2

Acer pensy lvanicum

. . . . . . . 1

Betula lenta

. . . . . . . . . . . . . 2

Ac e r rubrum . . . . . . . . . . .

x

I l ex mon ta na . . . . . . . . . . . . . . .

Querc us borealis

v.

m a x i m a

. . .

Co rnu s flflorida . . . . . . . . . . . . . .

Hamame l i s v i rg in iana

. . . . . . . . .

Ostrya virginiana . . . . . . . . . . . . .

Carya glahra . . . . . . . . . . . .

Clrthra acvminata

. . . . . . . . . . . .

Ara l ia sp inosa . . . . . . . . . . . . . .

Carya tomentosa . . . . . . . . . . . . .

Pyrular ia pubera

. . . . . . . . . . . .

Amelanchier arborea . . . . . . . . . .

Castanea dentata

(dead*).

. . . . . .

Robinia pseudoacacia . . . . . . . . .

Oxydendrum arboreum . . . . . . . .

Quercus pr inus . . . . . . . . . . . . . .

Sassafras a lbidum . . . . . . . . . . . .

Nyss a sy lvat ica

. . . . . . . . . . . . . .

Quercus velutina . . . . . . . . . . . . . .

Quercus alba

. . . . . . . . . . . . . . . .

Quercus coccinea

. . . . . . . . . . . . .

P i n u s r i g i d a

. . . . . . . . . . . . . . . .

P i n u s p u n g e m . . . . . . . . . . . . . .

Percents

y

classes

RIesic.

. . . . . . . . . . . . . . . . . . . .

97

Submesic

. . . . . . . . . . . . . . . . . .

3

Subxeric

. . . . . . . . . . . . . . . . . . . .

Xeric.

. . . . . . . . . . . . . . . . . . . .

4

ree s in s t a t i o n s . .

. . .

33;

Site-samples used. . . . . . . . . . .

STATION U M B E R

2 / 3 ) 4 / 5

6 1

7 8 1 9 ~ l O I l l I l 2 I 1 3

59;

671

41; 518

62; 35; 3 T 42:

43; 41;

554

5

x, Present below

5 7

*Dead ch estnut trees were counted in all stands.

Since the smaller stems had ceased to be identifiable as such in 1947,th e number of chestnuts in t he tables is smaller

than the number of living stems would have been (see size distributions in Appendix C .


9/81

R. H. WHITT KER

Ecological Monograph6

Vol. 2 6, No. 1

DISTRIBUTIONSF SPECIES

LOKG

THE quence of species populat ions along the moisture

MOISTUREGRADIENT

gradient is similar at all elevations below 4500 ft,

Distributions of tree populat ions along the mois-

but differs in deta il because of the varied relations of

ture gradient are shown in the three tables for dif-

species populations to elevation. From mesic sites to

ferent elevation belts (1500-2500 f t , Whi ttaker 1951, xeric, major tree species have their population

table 1 ; 2500-3500 and 3500-4500 ft , present work,

maxima in the sequence:

Aesculus oc ta l tdra*, T i l ia

tables 2 and 3). Almost all species show a rounded

he t e r ophy l l a , Be t u l a a l l eghen i ens i s

Britt.,

Hales ia

or bell-shaped curve of population distribution along

mont icola

(Rehd.) Sarg.,

Acer saccharurn , L i r ioden-

P o ~ u l ~ t i o nhe gradient (see Figs.

21

31 4) . curves

d r on tu l i pi fe r a, T s ug a ca na de m is , Q u e r c ~oreal is v.

for different species, including many of those in dif-

mazima( ~ ~ ~ ~ h . 1arya

glabra ,

ace,.

rubrum,

ferent

Car ya t om en t osa , Cas t a lz ea den t a ta , ue r c m prinus

centers for species and limits of their distributions

Nomenclature follows tha t of Fe rna ld

(1950)

except where

are well scattered along the gradient. The basic se-

.,thorities ar e given.

T BLE3. Composite transec t of moisture gradien t between 3500 an d 4500 ft , distri buti on of trees alon g gradi ent .

Transect along the moisture gradient from mesic valley sites (Sta.

1)

to xeric southwest slope sites (Sta. 12), based

on 46 site counts including 4906 stems from elevations between 3500 f t a nd 4500 ft .

All

figures are percentages of

total stems in station from 1-in.

diameter class up.

ST TION

NUMBER

Tree species

1 2 3 4 5 6 7 8 9 1 0 1 1 1 2

Fagus grandijolia. . . . . . . . . . . . . . . . . . 10 5

1

1

1

. . . .

. .

.

.

.

. . . .

Ilex opaca. . . . . . . . . . . . . . . . . . . . . . . . . .

1

. .

x

. . . . .

.

. . . .

. .

. .

. .

Picea Tubens. . . . . . . . . . . . . . . . . . . . . . . .

x . .

x

. . . .

. . .

. . . . . .

Cornus alternijolia. . . . . . . . . . . . . . . . .

1 1

. .

s

x

. . . .

. . . .

.

.

.

. .

Aesculusoctand~a. . . . . . . . . . . . . . . . .

8

9

2

6

1

. .

. .

. .

.

.

. .

. .

Tilia hete~ophylla.

. . . . . . . . . . . . . . . .

29

11

9

1

14 3 . .

. .

.

. .

. .

. .

Acer spicatum. . . . . . . . . . . . . . . . . . . . .

16

11

. .

17

1 . .

.

.

. .

.

.

.

. .

Acersaccharum . . . . . . . . . . . . . . . . . . . . 7

7

1 1 5

1

. .

. . . . .

. .

. .

Prunus se~otina. . . . . . . . . . . . . . . . . .

2

1

. .

1

x 2

. .

. . . .

. .

. .

. .

Fraxinus americana.. . . . . . . . . . . . . . .

1

1

. .

1

1 x

. .

.

. . . .

. .

Betula allegheniemis. . . . . . . . . . . . . . .

5 17 10 15

4

1 x

. .

. . . .

.

. .

Magnolia acuminala

. . . . . . . . . . . . . . . .

. . . .

x

. .

1

. .

. . . .

.

.

.

Magnolia jraseri.

. . . . . . . . . . . . . . . . . .

. . 20

4

1

. . 1 . . . . . .

.

.

.

Tsuga canadensis.. ............

20

22

34 62

18

x x

1

. .

. . . . . .

Halesia monticola.. . . . . . . . . . . . . . . . .

5 8 4

1 9 13 3

1

1

. .

. . .

Ilex montana..

. . . . . . . . . . . . . . . . . . .

1

x

. . 1

1

1

2

. .

.

. .

.

.

. .

Ace~pensylvanicum . . . . . . . . . . . . . . .

1 x 1

3

8 3

x 1

. .

. .

. .

.

.

Amelanchie~ aeciis. . . . . . . . . . . . . . . . . . .

x . . x

x

. . . . . . . . . . . . . .

Quercus borealis.

. . . . . . . . . . . . . . . . . . . .

1

. .

. .

2

40

10

4

15 11

2 1

Acer rubrum. . . . . . . . . . . . . . . . . . . . . . . .

1

. . . .

1

6 37

21 13

10

8

1

Prunus pensylvanica. . . . . . . . . . . . . . . . .

. .

2

. .

. . .

1 . .

. . . .

. . .

Betula lenta.. . . . . . . . . . . . . . . . . . . . . . .

.

.

1 4 4 1 2 2 . .

. .

. .

. .

Clethra acuminata..

. . . . . . . . . . . . . . . . . .

. . . .

1

x

. . . .

.

. . . .

.

. .

Hamamelis vi~giniana

. . . . . . . . . . . . . . .

. . . . . .

2

5

17 7 1 . .

2

. .

Cornus jiorida. . . . . . . . . . . . . . . . . . . . . . .

. . . .

. .

1

. .

x 4

. . . .

. .

. .

Li~iodendron ulipijera. . . . . . . . . . . . . . .

. . . . . .

2

. . . .

1

x

. . .

Rhododendron calendulaceum

. . . . . . . . . .

. .

.

. .

.

. .

1

. .

1 4

. .

.

.

. .

C a ~ y alabra . . . . . . . . . . . . . . . . . . . . . . . .

. . . .

.

.

. . 4

x 2

6 5

. . .

Ca~yaomentosa.. . . . . . . . . . . . . . . . . . . .

. . . . . .

. .

. .

. .

2

. .

. . . .

.

.

Carya ovalis.. . . . . . . . . . . . . . . . . . . . . . . .

. . . .

. .

. . . . .-

x

. . . .

. .

Nyssa sylvatica.

. . . . . . . . . . . . . . . . . . . . .

.

.

1

. .

. . . .

2

4

1

2

7

. .

Oxydend~umarboreum.. . . . . . . . . . . . . . .

. .

x

1

. .

1 3

8 1 4 1 6

1 1

Cmtanea dentata (dead).

. . . . . . . . . . . . .

. . . . . .

2

5

7 9 10

12

1

. .

Sassaj~as lbidum... . . . . . . . . . . . . . . . . .

. . . . .

. .

1 1 1 1 4 x . .

Quercus alba. . . . . . . . . . . . . . . . . . . . . . .

. . . . .

.

. .

2

1 8

24

10

x

. .

Rolrinia pseudoacacia.

. . . . . . . . . . . . . . . .

. . . . . .

. . 4 5 1 3 8 3 x

Quercus prinus. . . . . . . . . . . . . . . . . . . . . .

. . . . . .

. . 3 4 15

4

16

11

1

Quercus velutina. . . . . . . . . . . . . . . . . . . . .

.

. .

.

. .

. .

. . x x l l . .

. .

Quercus coccinea..

. . . . . . . . . . . . . . . . . . .

. . . . . .

. . . .

1

. .

. . . .

.

.

1

Pinus rigida.

. . . . . . . . . . . . . . . . . . . . . . .

. . . . . .

. .

. .

. .

7

1 1

11

46

Pinus pungem. . . . . . . . . . . . . . . . . . . . . .

. .

. .

. . . .

. .

. .

1

4

54

49

Percents by classes

hfesic . . . . . . . . . . . . . . . . . . . . . . . . . . .

98

98 95

90

78 22

5

3

1

. .

. . . .

Submesic . . . . . . . . . . . . . . . . . . . . . . . . .

2 2 4

9

19 62 70

44

39 26

12 2

Subxeric . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . 1

1

2

16 23

46

58

69

23 2

Xeric.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. .

.

. .

. . . .

1

7 2

5

65

96

Treesinstations

. . . . . . . . . . . . . . . . . .

377

597 520

232

449

594

472 266 369 378

297 355

Site-samples used. . . . . . . . . . . . . . . . . .

1

7

4

4

4

4

4 4

3 4

4

x

Present

below .5 .


10/81

F I G . 2.

Transect of the moisture gradient, 1500 2500

ft . Topcurves for tree classes: a, mesic; b, submesic.

c

subxeric; d,

xeric. Middle-curves f o r t ree

a

~ ~al legheniensis; ~

b,

cornus

c uercus for*;

prinus

d, Pinus virginiana,

Bottom-curres for

under.

growth coverages a, herbs

;

b, shrubs.

Q uercus a l ba , Q . ve lu t ina , Q coccinea,

and

Panus

v i rg i n i ana , P . pungens ,

and

P . r i g i da .

Comparable data on population levels are not

available for shrubs and herbs, but these appear to

be distributed in the same manner as the trees. Spe-

cies populations overlap widely along the gradient,

and centers and limits of distribution are scattered

along the whole of the gradient.

Anlong the shrubs

R h o d o d e n d r o n m a x i m u m

is the

most important specic3s in mesic sites, but it is a

major species in submesic sites also and occurs in

subxeric and some xeric ones.

H y d r a n g e a a r b o -

rescens is the only other shrub species very widely

distributed through mesic and submesic forests.

Lezicothoe ed i torum

occurs only locally in mesic for-

ests; other mesic shrub species are restricted to low

elevations or high ones. I n submesic sites a number

of deciduous species make up the shrub stratum along

with the evergreen ericads

R h o d o d e n d r o n m a s i m u m

and

K al m i a l a t i f o l i a .

Among the major species of

submesic shrubs some

V i b u r n u m a c e r i fo l iu m , C a l y -

can t hus f e r t i l l s , P yru l ar i a pubera )

extend more

widely into mesic sites, but these and others

G a y -

lussac ia urs ina

(M. A. Curt is) T. G.,

C l e t hra acu -

m i n a t a , R h o d o d e n d r o n c a le n d u la c e u m , S m i l a s r o t u n d i -

f o l i a )

extend varying distances into subxeric and

xeric sites. I n subxeric sites and some xeric ones,

Kalmia la t i fo l ia

is the principal shrub species.

L y -

o n ia l i g u s t r i m , S m i l a x g la u ca ,

and the widespread

species V a c c i n i u m c o n s ta b l ae i A. Gray may best be

grouped with it in a subxeric class. Several shrub

species

V a c c i n i u m v a ci ll an s, V . h i r s u t u m

Buckl.,

V .

s tamineum, Gaylussac ia baccata , P ier i s j l or ibunda,

Z l ex m on t ana

v.

beadlei

(Ashe) Fern.) are centered

in xeric sites and extend varying distances into sub-

xeric and snbmesic ones.

A

number of herb species are centered in mesic

forests and dominate the herb stratum there; major

IG

3.

Transect of the moisture gradient,

2500 3500

f t .

for

tree ,%lasses: , mesic; b, submesic;

c, subxeric; d, xeric. Middle-curves for tree species:

a,

Ha esi m ont t coza ;

b,

A c e r r u b l u m ;

c,

Quercus cot

Ctnea

d,

Pinus rigida.

Bottom-curves for undergrowth

coverages: a, herbs; b, shrubs.

species include

Dryopteras sp inulosa

v.

i n t e rm ed i a ,

d t h y r t t t n ~ t hel ypt e raoades , C au l op l ry ll um t hal ic -

t ro i des , C i m ica fuga racem osa , E up a t or i um rug osu m ,

Lrrpor tea canade ns i s , Imp at i e ns pallada,

and

A s t e r

di rar i ca tus .

These extend varying distances into sub-

mesic forests. Other species which are important in

mesic sites

S m i l a n n a r a c e m o s a , P o l y g o n a t u m

spp.,

Desnlodanm nudaf lorztm, Polystachum acrost ichoides)

are major herb species also in submesic sites.

The

latter have been grouped with those mcre clearly

centergd in submesic sites A u r e o l a r i a l a e v i g a t a

(Raf.) Raf.,

Prenan thes t r i fo l io la ta , Medeola v i r -

g i n i ana , D ryop t e r i s noveboracensi s , V er a t r um parr i-

f iorum

Michx.) into a submesic class. A number of

these species extend widely into subxeric sites, where

they are joined by others

C a m p a n u l a d i v a r i c a t a ,

C h i m a p h i l a m a c u l a t a )

of more limited extent into

submesic sites.

G a l a s a p h y l l a ,

the most important

subxeric herb species, is widely distributed from sub-

mesic sites to most xeric ones. Other herb species are

centered in xeric sites; most of these

P t e r i d i u m

aqzl i l inum

v.

l a t i u scu l um , Tephros i a v i rg i n i ana , B ap-

t i s ia t i nc to r i a , G au l t he r i a p rocum bens ) extend widely

into subxeric sites, and some of them

E p i g a e a r e p -

e n s , P a n i c u m

sp.,

C o r e o p s i s m a j o r , A n d r o p o g o n s c o -

p a r i u s )

extend into submesic sites, in part of their

elevation range, a t least. More complete lists of herb

and shrub species assigned to moisture classes are

given in the Summary of Distributional Groupings.

There is no point along the gradient at which

either floristic composition or dominance changes

abruptl y in any stratum. Rather than this, the

rounded and tapered distributions of species popula-

tions, the scattering of their distributional centers

and limits along the gradient, and their broad over-

lap with one another imply gradual and progressive

change in relative importance of species and in total

floristic composition from one extreme of the gradi-

ent to the other.


11/81

FIG.

4.

Transect of the moisture gradient, 3500-4500

f

t

Top-curves for tree classes a, mesic;

b

submesic;

c, subxeric; d, xeric. Note expansion of mesic stands,

compared with Figs. 2 and 3 Middle--curves for tree

species: a, Tilia heterophylla; b, Halesia mnt ico la (both

the preceding are bimodal, with populations on each

side of the mode of Tsuga)

c, Tsuga canadensis; d,

Querms alba; e, Pinus pungens. Bottom-curves for

undergrowth coverages: a, herbs; b, shrubs.

Various trends in community composition and

structure can be followed from one extreme of the

moisture grad ient to the other. These trends, com-

parable to those already studied in foliage insect

communities (Whittaker 19.52), are in most cases

continuous through whatever community-types or

associations may be recognized.

GROWTH - F O RMS

Four growth-forms of trees are recognized in the

Smokies (see Pa rt 111) pines, abietines (Tsziga

canadensis), oaks, and other deciduous trees. A con-

tinuous shift in proportions of these appears along

the moisture gradient (Whitt aker 1953 :49 ). De-

ciduous trees other than oaks predominate in mesic

sites, oaks in intermediate sites, and pines in xeric

sites. Toward higher elevations a belt in which

Tsuga canadensis is dominant is interposed between

the first two of these. The pa tte rn of growth-form

composition, and the predominance of the semi-sclero-

phyllous, deciduous oak grouping in intermediate

sites, is the same whether or not Castanea dentata ,

Fagus grandzfolia, and the ericaceous tree Oxyden-

drzcm arboreum are grouped with the oaks. Among

the shrubs a comparable shift in growth-form com-

position appears, involving deciduous and evergreen,

ericaceous and non-ericaceous species. Deciduous

non-ericaceous species predominate in mesic sites,

with some exceptions; but deciduous species decline

in importance along the gradient as evergreen eri-

cads increase to become strongly predominant in sub-

xeric sites. Toward the xeric extreme, evergreen

ericads decline and deciduous ericads (Vaccinioideae

or Vacciniaceae) increase to dominate the shrub

stratum in most xeric pine heaths.

HITTAKER


Vol. 26 No.

Herb species are less easily classified, but trends in

importance map be observed among the more numer-

ous growth-forms which might be recognized. Fer ns

with delicate foliage (Dryopteris and Athyrium) are

centered in mesic sites and decline in importance

through submesic into subxeric ones. A group of

herbs of moderate stature with broad, thin leaves and

a characteristic spreading or umbrella-shaped growth-

form (Caulophyllum, Cimicifuga, Actaea, Impatiens,

Trillium, Laportea, Osmorhiza, Thalictrum, Eupa-

torium rugosum, Aster divaricatus) prevail along

with ferns in mesic sites and are of decreasing im-

portance toward more xeric ones. Other herb form s

-rosette plants (Goodyera pubescens, Verat rum

parviflorum, Viola hastata) and those with leaves

spaced along the qtem (Aureolaria, Solidago, Smila-

cina, Vvularia, Melampyrum, Coreopsis)-are more

important in submesic and subxeric sites; and foliage

of herbs in these sites is, on the whole, tougher than

that of the delicate-leaved mesic herbs.

Species of

these groups occur also in xeric sites, but

a

variety

of other herb types prevail there: grasses (Andro-

pogon, Pan icum), ground heaths Gaultheria,

Epigaea), legumes (Baptisia, Tephrosia), a tough-

leaved fern (Pteridium), and a club-moss (Lycopo-

dium obscurum). Of these the grasses are the major

herb growth-form in xeric sites at lower elevations;

and the ground heaths are the major herb growth-

form in subxeric sites and in xeric ones at higher

elerations.

COVERAGES

I n general, tree coverage and density of the canopy

decrease along the moisture gradient from cove for-

ests into pine forests; light penetration to lower

strata consequently increases along the gradient

(TIThittaker1952). Estimated tree coverages increase,

however, from subxeric sites (oak-chestnut heath)

into xeric ones; the very low canopy coverage in oak-

chestnut heath is in part a consequence of death of

the chestnuts. Shrub coverage in general increases

along the gradient toward more xeric sites (Figs. 2,

3, 4 ) . This trend is modified, however, by the pres-

ence of a secondary maximum of shru b coverage in

hemlock fores ts in-mesic sites, and by a final decrease

of s hrub coverage in most xeric sites. He rb coverage

in general decreases along the gradient from mesic to

xeric sites. This trend also is modified in two re-

spects-by very low coverages in hemlock stands, and

by a final increase of herb coverage from subxeric

sites into xeric ones. Maximum herb coverages occur

in mesic deciduous forests, where moisture conditions

are most favorable, and in xeric pine forests, where

light penetration to the herb level is greatest. He rb

and shrub coverages show a clear inverse relation

within the set of transects for elevations below 4400

f t in the Great Smoky Mountains (Figs . 2 3, 4) .

D IVERS I T I E S

Diversity of the tree stratum can best be ap-

proached through the alplta values of Fisher (Fisher

r t al. 1943 Williams 1947, 19.50 Whi ttaker 1952).


12/81

January 9 5 6

VEGETATION THE GRE

F

These values provide a measurement of richness in

species which is, within limits, independent of

sample size. I n Fig. 5 alpha values fo r composite

stand counts are plotted on the vegetation pattern for

the Smokies developed in Part

111 At all elevations

highest diversity values are in intermediate sites-in

the cove forest transition below 3000 f t and oak-

chestnut forests above 3000 ft . The hemlock stands,

which provide exceptions to all the trends discussed,

are less diverse than the more and less mesic stands

on each side of them. I n general, however, species

diversity of the tree stratum rises along the gradient

from one minimum in most mesic sites to a maximum

in submesic sites and declines to a second minimum in

xeric sites.

FIG 5 Pa t te rn of t re e species d iversi ties (alpha d i-

ve r s ity va lues , f o r a l l t r ee s t em s in the compos i te s t a nd

counts of A ppendix C .

Alpha values cannot be computed for the under-

growth data available. Analysis of the transects

through average numbers of species listed per sample

provides a more limited indication of diversity trends

in the herb and shrub strata . F or shrubs the average

numbers of species recorded in mesic, submesic, sub-

xeric, and xeric stands are : 5.2, 7.6, 6.2, 6.6. A sub-

mesic maximum corresponding to that for trees is

thus suggested; but the shrub stratum in xeric sites

may be more diverse than that in

subxeric ones, often

strongly dominated by Kalmia latifolia. Correspond-

ing average numbers of herb species ar e : 19.1, 10.6,

7.1, 8.6. The herb stratum is thus richest in species,

as well as of highest coverage, in mesic sites and

shows a secondary maximum of both diversity and

coverage in xeric sites.

SIZES 4 N D

XI-MDERS

O F

STEMS

O F

TREES

Stature and stem diameter of canopy trees in gen-

eral decrease along the moisture gradient . I n mesic

sites canopy trees are more than 100 f t high and 3-4

f t or more in diameter, in xeric sites they ar e mostly

50-75 f t high and 1.0 to l..5 f t in diameter The num-

ber of tree stems per unit area In general increases

along the gradient (c f. Ilvessalo 1921, Lutz 1932 ),

in inverse relation to tree stature. The cove forests

have mostly between 7.50 and 1000 stems per hectare

from the 1-in. class up (except in stands of higher

elevations where there are many small stems of Acer

spicatum) the more xeric stands have mostly 2000

to 2500 stems per hectare. I n pa rt the increase in

stem numbers toward xeric sites reflects the smaller

sta ture and denser growth of canopy trees; but the

numerous small stems in more xeric sites are pre-

dominantly made up of small-tree species. These

small-tree species (Carpinus carol~nlana,Magnolia

trzpetnla, Ostrya vi rg~n lana , Il ez opaca; Cornzis

jlortdn, Betzcla lenta, Acer r~lbr~lm,Hamamelis vlr-

giniamn, Cletltra aczcminata, Acer pensylvaniczcm;

Robinia pseudoacacia, Oxydendr~lmarboreum, Sassa-

fras albiclzcm; Q~lerczcsmarilandica) are relatively un-

important in most mesic sites ( as low as 1-2 of

stems in some cove forests) and most xeric sites

(10 -15 ). I n submesic and subxeric stands of lower

and middle elevations, however, the small-tree species

comprise around 50 of stem numbers.

Trends in stand composition have been much af-

fected by death of the chestnuts (Castanea dentata).

In many submesic and subxeric stands chestnut

formed 30-60 of the canopy stems, and death of the

chestnuts both removed many of the larqest stems

from the stand and permitted heavy reproduction of

other species. Effects of death of the chestnuts are

most evident in chestnut oak-chestnut forests, in

which maxirriunl numbers of tree stenis per unit area

now occur, and in which 70 of the s t e r ~ ~ sn sollie

stands are now of the sniall-tree species.

Trends in tree sizes are illustrated in a family of

curves (F ig . 6) , in which steepness of slope reflects

normal survival of small trees into larger size classes.

The more xeric the site, the steeper the curve and

the smaller the proportion of growth and survival

into larger size classes. The oak-chestnut curve is

altered by death of the chestnuts and increased re-

production of other species; the dotted curve is an

interpolation of what might be expected otherwise.

The hemlock forests are exceptional, for large sizes

are even more heavily represented than in cove hard-

woods forests. Fi g. 7 indicates the effect of the same

gradient on growth and survival in the populations of

red maples (Acer rubrum).

Curves such as those illustrated in Figs. 6 and 7

ore expressions of the dynamics of stands, the man-

ner in which the tree population is maintaining it-


13/81

HITTAKER


Vol.

26 No.

1

FIG.

6.

Stem number-diameter curves for tree stands

at middle elevations.

self o r failing to do so (Paczoski 1928, Meyer

Stevenson 1943). Meyer Stevenson (1943) have

indicated a relatively simvle relation of diameter and

.

stem number, which plots as a straight line on a log

and linear graph like those of Figs. 6

7.

Such a

plot implies that growth rate and survival rate are

largely constant with age; variation of growth rate

with age introduces into log-linear plots the curva-

ture to be observed in Figs.

6

7.

A curve following

the stand data more closely has been developed. As-

suming x = arw to be a fit for the stem number-age

relation, and

w

= ( y d ) C reasonable approxima-

tion for the age-diameter relation, then the stem

number-diameter relation becomes x

=

ar(y

I n this is the number of stems in a diameter class,

a

is the number of stems in the initial class,

r

is the

survival ratio between successive classes,

y

is the

middle diameter of the class, and d and c are con-

stants relating diameter to age. (A n alternative,

purely empirical form which is less difficult to apply

is the series a, ar, ar (r -b ), ar (r -b ) (r-2b) . . .

,

in which

b

is arbitrarily introduced to help the curve

fit.)

The value of such curves is in the possibility of

recognizing the self-maintaining, climax condition

they describe. Many all-age and probably climax

stands which have been analyzed show the basic form

illustrated. I t is also true tha t the continuous repro-

F IG 7

Stem number-diameter curves for

Boer ru

r m in different sites.

duction and replacement which these curves imply

is by no means the only way climax stands can main-

tain themselves (Jones 1945, Whit taker 1953). Cyclic

reproduction seems to occur in the Smokies pine

stands ( Pa rt 111). Other coniferous stands are stag-

nant in the sense that stems are concentrated in

large r size-classes, with inadequate numbers of smaller

stems to replace them if a constant survival ratio

is assumed. Some of the stands more strongly domi-

nated by

Tsuga canadens i s

are of this form (cf.

Meyer Stevenson 1943), as ar e some of those of

the spruce-fir forests, especially the high-elevation

stands of

Abies fraseri .

I t seems likely that repro-

duction in these stands is periodic, partial or com-

plete destruction of the canopy permitting its re-

placement at irregular intervals, rather than con-

tinuously. If such limitations are kept in mind, hon -

ever, analysis of all-age stand composition may con-

tribute to the difficult problems of climax identifi-

cation.

The basic similarity of the curves for different

parts of the gradient may be observed in Fig. 6

Curves for individual tree species differ widely in

slope from those fo r whole stands, but Fig. (and

the stand data for other species, Appendix C) indi-

cate the same basic similarity. Ap ar t from certain

distortions of the curves clearly produced by death

of the chestnuts, there is no evidence that any of


14/81

13

anuary, 1956 VEGETATION

TFIE

GREATS M O K YF MOUNTAINS

these undisturbed stands are changing toward other

types. All, from cove forest to pine forest, have the

self-maintaining properties of climax stands, so far

as can be determined. Evidence of convergence to-

ward a single climatic climax type is thus lacking.

I n the southwestern Smokies, outside the range of

spruce-fir forests, deciduous forest types extend to

the highest peaks (around

5500

ft or

1680

m). In

order to study the distributions of p lant s in these

deciduous forests above

4500

f t, a transect by site

was arranged for 37 site-samples. The most mesic

sites available at these elevations are gaps and con-

cave slopes of north and northeast exposure, where

forests of

Fagzcs gralzdifolia

mixed with other mesic

trees occur. The south, southwest, and west exposures

TABLE

4.

High-elevation deciduous forests, transect

of exposure gradient by topographic sites for Eastern

Forest System types above

4500

ft. Distributions of

trees by percentages of stems in stand.

Steps in gradi-

ent:

1

beech-mixed forests in sheltered north slopes;

2, gray beech forests in sheltered south slopes;

3,

red

oak-chestnut forests, open slopes;

4,

white oak-chestnut

forests, open south slopes;

5

grassy balds on exposed

peaks.

Acer spicatum. . . . . . . . . . . . . 14

Aesculus octandra.

. . . . . . . . . .

11

Betula allegheniensis.

. . . . . . .

10

Acer pemylvanicum. . . . . . . . . . 1

Acer saccharum.

. . . . . . . . . . . .

1

Tili a heterophylla.

. . . . . . . . . .

x

Sorbus americana. . . . . . . . . . .

x

Cornus alternifolia. . . . . . . . . . . x

Fraxinus americana.

. . . . . . . .

x

Amelanchier laevis . . . . . . . . . . .

4

Fagus gandifolia. . . . . . . . . . . 50

Zlez montana. . . . . . . . . . . . . . . . .

Prunus serotina.. . . . . .

Halesia monticola. . . . . . . . . . . 2

Quercus borealis..

2

Tsuga canadensis.. . . . . . . . . . . 1

Acer rubrum..

. . . . . . . . . . . . . .

2

Hamam elis wirginiana.. . . . . . . . .

Betula lenta. . . . . . . . . . . . . . . . .

Vaccinium constablaei. . . . . . . . . .

Rhododendron calendulaceum.

Magnolia fraseri. . . . . . . . . . . . . .

Magnolia acuminata.. . . . . . . . . .

Ozydendrum arboreum.

Castanea dentata

(dead).:

1

Sassafras albidum. . . . . . . . . . . . .

Quercus alba..

. . . . . . . . . . . . . . . .

Robinia pseudoacacia. . . . . . . . . .

Nyssa sylvatica.

. . . . . . . . . . . . . .

Quercu.7 velutina. . . . . . . . . . . . . . .

Prunus pemylvanicn.. . . . . . . . . .

Pinus pungem.

. . . . . . . . . . . . . . .

Pinus rigida.

. . . . . . . . . . . . . . . . .

Pinus strobus..

. . . . . . . . . . . . . . .

Liriodendron tulipifera .,

. , . . . . .

Total stems. . . . . . . . . . . . . . . .

Site-samples used.

. . . . . . . . . .

x present below

0.5%.

- seedling^ recorded.

are more xeric; and these may be grouped into three

stages: sheltered south slopes and south-facing sides

of gaps, supporting beech forests; more xeric open

slopes supporting red oak-chestnut forests, and most

xeric open south- and southwest-facing slopes, sup-

porting red and white oak-chestnut or white oak-

chestnut. Some most exposed summits of peaks,

fi-

nally, are covered by grassy balds. Distributions of

tree species may be observed along this five-stage

transect (Table

4

; distributions of shrub and herb

species are not published here (see Note on Supple-

mentary Publication).

Relations of tree species to the moisture gradient

are in general the same at high elevations as at low

ones. Hales ia mont ico la , however, which is a highly

mesic canopy tree at lower elevations is a submesic

small-tree species at these highest elevations ; this

species comprises two population-types with separate

distributional centers (see Part

I1

and Appendix

A) .

V i b u r n u m a l n i f o l i u m , C o r n u s a l te r n if o li a , and H y -

drangea arborescens are major shrub species at the

mesic extreme, V a c c i n i u m c o n s t a b l a e i and R h o d o -

d e n d r o n c a l e n d u la c e u m in the oak-chestnut forests.

V a c c in i u m c o n sta b la e i

spans the whole of the gradi-

ent from north-slope beech stands to grassy balds, as

do the less frequent species

R ib e s r o tu 7 td i f o l i u m

and

R h o d o d e n d r o n c a ta wb ie n s e . Those shrub species

( K a l m ia l at i f o li a , L y o n ia l i g u s tr i n a , G a y lu s s a c ia ba c-

c a t a, V a c c i n i u m va c il la n s, V . h i r s u t u m ) which are

most abundant in the forest-heath types at lower ele-

vations are limited to the oak-chestnut forests and

grassy balds in the transect.

A r o n ia m e la n o c a r p a

(Michx.) Ell. and V i b u r n u m c a s s i n o i d e s , species

which occur in the heath balds, were recorded in the

transect only from the grassy balds.

At the mesic extreme, species of the mesic and high-

elevation mesic herb groupings dominate the herb

stratum; some of these species extend into south-

slope beech stands and red oak-chestnut s~ands.

Ca r e s a e s t i v a l i s is strongly dominant in south-slope

beech stands and extends into both more mesic north-

slope beech stands and less mesic red oak-chestnut

forests.

A t h y r i u m J i l i x - f e m i n a

v.

asplel t io ides

is a

major herb species of these high-elevation forests and

extends along the gradient from not-th-slope beech

stands to white oak-chestnut, as does M e d e o la v i r -

g in ia n a . E p ig a e a r e p e n s , G a la x a p h y l l a , P e d ic u la r i s

c a l z a d e n s i s , P t e r id iu m a q u i l i n u m v. l a t i u s c u l u m , and

Ca m p a n u la d i v a r i c a ta ,

species of more xeric forest

types a t lower elevations, ar e limited to the oak-chest-

nut s tands in the high-elevation transect. Ecotypic

populations of some forest herb species

( A n g e l i c a t r i -

q u in a ta , S t e ll a r ia p u b e r a , R u d b e c k ia lm n ia t a , P r e -

n a n th e s a l t i s s im a , H o u s to n ia s e r p y l l i f o l i a , G e n t ia n a

d e c o r a )

occur in the grassy balds with a variety of

other species (see Part 111).

Carex aes t iva l i s

and

other species centered in the south-slope beech stands

and red oak-chestnut forests above

4500

f t have been

grouped in a high-elevation submesic herb union.

Stratal trends are less clear-cut in these forests

than in those of lower elevations. Tree-stratum di-


15/81

E c o l o g i c a l M o n o g r a p h s

V o l .

26,

N o . 1

versity decreases from north-slope beech stands into

T LE . Composite elevation transect in mesic sites,

south-slope ones, increases from these to a maximum

distribution of trees. All figures are percentages of total

in red oak-chestnut forests, and decreases again into

white oak-chestnut. Coverage of the shrub stratu m

Station I*

decreases from north-slope into south-slope beech

Elevation,hundredfeet. 6

)

stands, increases through red oak-chestnut to white

Tree species

oak-chestnut stands and the forest-edge of grassy

Fagus grand tfolia..

. . . .

6

balds, and is low in the grassy balds. He rb coverage

Tsuga mnadensis. .

. . .

12

Halesia mont~cola . . . . . .

3

increases from the north-slope to the south-slope

Prazznus amerimna..

. .

x

beech stands, is lower in the oak-chestnut forests, and

Till o heterophylla..

. . . . .

6

is near

100%

in the grassy balds.

As in forests of

Lzriodendron tuli pifer a. .

1

lower elevations, herb and shrub

coverages are in-

Aesculus octandra

. . . . .

4

Betula ollegheniensis.

. . .

1

versely related. Deciduous trees other than oaks de-

l c e r sae c hrum .

. . . . . . .

4

erease from mesic sites into submesic and subxeric

Magnolza fra seri. . . . . . . 2

ones, where oaks predominate; evergreen tree species

Magnolia tripetola .. . . . 1

are almost absent from these forests. I n the shrub

Magnolia acuminata. . . . . .

Carptnus carolzniana.. 10

stems in station from I-in. diameter class up.

5

20

24

28 32

36

40 44

1

7 8

.

x 1 2 ' 6 1 6

14

23 10

8

8

5

12 13

18 30 4

1

2 2 1 6 1 1

3 15

15 20 22

4

2 4 1 x x . .

4 2

5 4 1 1 1 4

5

16 11

8

10

4

2 1 2

5 1 2

4

3 5 2 x . .

x

1 . . . . . . . .

1 . . x

1

1

. .

. . . . . . . . . .

x

3

. . . . . . .

. . . .

1 x

x

.

.

4

. . . . .

.

~ 1 4 1 7 3

. . . . .

x

1

1

. . . . . .

1

. . . . . . . . .

1

13 2

. .

x

. .

3 2 1 1 2 5

1 x 1

. . . : . .

2 3 5 2 x 2

6 2 6 2 1 2

1 0 3 2 1 2 1

. . x x

2

x

5 1 1

. . . .

X . . X . . . . . .

. . . . . . . . . .

3 1 1 . . x .

X

. . . . . . . .

2 . . 1 3 1 1

. . . . . . . . . . . .

4 1

x . . x .

X

. . . . . . . .

. . . . . . . . .

1 x x

. . . . . .

48

52 56

1

10

I

0

. . . . . . . . . . . . . .

stratum non-ericaceous, deciduous shrubs prevail in

lnesic sites; but deciduous ericads (Rhododendron

calendulaceum and Vaccinium constablaei) prevail

in the oak-chestnut forests.

DISTRIBUTIONSSPECIES TO ELEVATIONF IN RELATION

MESIC

SITES

Progressive change in composition of cove forests

is indicated in the elevation transect of mesic sites

(Table 5, Fig.

8 ) .

Species distributions show a

rounded or bell-shaped form in most cases, overlap

broadly, and have their centers and limits scattered

along the gradient. Most major tree species occur

throughout the elevations represented in the transect,

but the sequence of their population centers from

lolv elevations to high is : Fagus grandifolia ("white"

population see Part 11 , Liriodendron tulipifera,

15

2d00

2&0 3 b

35b

4d00 45b

5000

EL EVA T ION IN F EE T

FIG. 8. Elevation transect in mesic sites, smoothed

curves for tree species: a, Liriodendron tulipifera ; b,

Tsuga canadensis c. Halesia monticola d, Tilia hetero-

p h y l l a ; e, Acer saccharum; f , Acer spicatum; g, Car-

pinus caroliniana h, Betula allegheniensis; i, Aesct~lus

octandra; j, B'raAinus americana; k, white, 1, red, and

m, gray populations of Fagus grandifolia (based on

data for 200-foot intervals).

I le z opc a

. . . . . .

1

Carua eordifmmu

. . . . .

2

Cladrastis lu teo.

. . . . . . . .

Acer spimtum.

. . . . . . . . . . .

Prunus se~ottna

. . .

Amelanchter laenis.

. . . .

Cmnus al lernifo lb. .

. . .

C m n u s f l m i d o . .

. . . . . . . .

14

Quercus bmealts &

v .

mazima

. . . . . . . .

3

Amelanchter arborea.

x

BeluIa lenlc

. . . . . . . . .

8

Acei pensgdnanicum. . . . 1

Acer rubrum . . . . . .

12

Ilez montona. . . . . . . . . . x

Carua glabra..

. . . . . . . . .

2

Carua lomento sa.. . . . . . . . .

Carua ooalts. . . . . . . . . x

Q u e r u s p r i n w .

. . . . . .

2

Nussa sulwrlim

. . . . . . .

1

Casfunea denlato (dead). 1

Que rc us a l h . .

. . . . . . . .

1

Oz~ae ndrum rbm e um . . 2

Pinus s f robus . . . . . . . .

x

S as sa fr as a b d u m . . . . . . x

Robinia pseudoacucia

. . . . .

Total stems. .

. . . . . . . . R

841 518 639 793 429 358 468 646 360 406

S i t e . ~ m ~ l ~ u ~ e d . . 2 5 5 2. . I

I

I I I I I I I I I I

*Stations grouped

t

400-it. intervals (1450-1800 it.. 1850-2200 it., etc.)

x. Present below 0.5%.

Betula allegheniensis, Halesia monticola, Acer sac-

charztm, Tilia heterophylla, Aesculus octandra, and

Faglis grandifolia ("red" and ((gray" populations).

The decline towad higher elevations of Tsuga cana-

densis and Magnolia fraseri does not reflect their

true distributions (cf. Appendix A) , for toward

higher elevations these species are increasingly segre-

gated into hemlock stands which were not included in

the transect. The most significant change in composi-

tion of stands occurs at 45 f t ; a t this elevation

there is a relatively abrupt shift of dominance from

other cove-forest species to gray beech (Fagus

grandifol ia). Some small-tree populations (Acer

spicatctm and Amelnnchier laez'is) are centered near

45 f t along with Aesculzis octandra and one popu-

lation of yellow birches (Betula allegheniensis or B.

Ititen). Trees and shrubs centered in the transition

from core forests to gray beech and spruce-fir forests

Sorbus america na. . . . . . . . . .


16/81

January. 1956 VEGET TION

THE

GREAT

SMOKY I5

F MOUNTAINS

fo r m the ecotona l -mes ic un ion l i s ted in the Sum -

ma ry o f Dis t r ibu t iona l Group ings .

Among the mes ic sh rubs two spec ies ( E u o n y m u s

a m er i ca n u s

a n d

L i n d e r a b e n z o i n )

a r e r e s t r i c t e d t o

lowest e levat ions; cer ta in others (C o rn u s a l t e rn i fo l i a

a n d

V i b u r n u m a l n if o li u m )

a r e c e n t e r e d a r o u n d

4500

f t a n d f o r m p a r t o f t h e e co to n al -m e si c g r o u p i n g .

R h o d o d e n d r o n m a x i m u m a n d Leucotho6 ed i torum

o c c u r a t a l l e l e v a t i o n s u p t o a b o u t 4500 f t ; H y -

drangea arborescens

occurs f rom some of the lowest

elevat ions to the highest recorded in mesic deciduous

f o r e s t s

( 5 5 0 0

f t ) . X o r e l a t i v e l y a b r

Whittaker - Vegetation of the Great Smoky Mountains

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