United States

Department of

Agriculture

Forest Service

Southern

Research Station

General Technical

Report SRS-15

An Old-Growth Definition

for Western Juniper Woodlands:

Texas Ashe Juniper Dominated

or Codominated Communities

David D. Diamond

A Section of the Old-Growth Definition Series
The Author:

David D. Diamond, Director, Missouri Resource

Assessment Partnership, Environmental Technology

Center, 4200 New Haven Rd., Columbia, MO 65201.

Preface

Old growth is widely acknowledged today as an essential part of managed forests, particularly on public lands. However, this

concept is relatively new, evolving since the 1970's when a grassroots movement in the Pacific Northwest began in earnest to

define old growth. In response to changes in public attitude, the U.S. Department of Agriculture, Forest Service, began

reevaluating its policy regarding old-growth forests in the 1980's. Indeed, the ecological significance of old growth and its

contribution to biodiversity were apparent. It was also evident that definitions were needed to adequately assess and manage

the old-growth resource. However, definitions of old growth varied widely among scientists. To address this discrepancy and

other old-growth issues, the National Old-Growth Task Group was formed in 1988. At the recommendation of this

committee, old growth was officially recognized as a distinct resource by the Forest Service, greatly enhancing its status in

forest management planning. The committee devised “The Generic Definition and Description of Old-Growth Forests” to

serve as a basis for further work and to ensure uniformity among Forest Service Stations and Regions. Emphasis was placed

on the quantification of old-growth attributes.

At the urging of the Chief of the Forest Service, all Forest Service Stations and Regions began developing old-growth

definitions for specific forest types. Because the Southern and Eastern Regions share many forest communities (together they

encompass the entire Eastern United States), their efforts were combined, and a cooperative agreement was established with

The Nature Conservancy for technical support. The resulting project represents the first large-scale effort to define old growth

for all forests in the Eastern United States. This project helped bring the old-growth issue to public attention in the East.

Definitions will first be developed for broad forest types and based mainly on published information and so must be viewed

accordingly. Refinements will be made by the Forest Service as new information becomes available. This document represents

1 of 35 forest types for which old-growth definitions will be drafted.

In preparing individual old-growth definitions, authors followed National Old-Growth Task Group guidelines, which differ

from the standard General Technical Report format in two ways—the abstract (missing in this report) and the literature

citations (listed in Southern Journal of Applied Forestry style). Allowing for these deviations will ensure consistency across

organizational and geographic boundaries.

September 1997

Southern Research Station

P.O. Box 2680
Asheville, NC 28802
1

 Literature search and preliminary description.

An Old-Growth Definition for Western

Juniper Woodlands: Texas Ashe Juniper

Dominated or Codominated Communities1

David D. Diamond

Description

Prominent juniper species that dominate or codominate

woodlands or shrub lands of the American Southwest

include Rocky Mountain juniper (Juniperus scopulorum

Sarg.), Pinchot juniper (J. pinchottii Sudw.), oneseed

juniper [J. monosperma (Engelm.) Sarg.], alligator juniper 

( J. deppeana Steud.), Utah juniper [J. osteosperma (Torr.)

Little], and Ashe (mountain-cedar, Mexican) juniper (J.

ashei Buchholz) (nomenclature follows Correll and

Johnston 1970). Among these, Ashe juniper is nearly

restricted in the United States to the Edwards Plateau and

Lampasas Cut-Plain of Texas, with outlier populations over

limestone in Oklahoma and Arkansas (see illustrations of

natural regions in Diamond et al. 1987, Riskind and

Diamond 1988). As classified by the Society of American

Foresters (SAF), this is an eastern forest cover type 66,

southern region, Ashe juniper-redberry juniper (J.

Erythrocarpa Cory) (Eyre 1980). I will not consider the

SAF western cover types, Rocky Mountain juniper or

pinyon (Pinus edulis Engelm.)-juniper, here. Also,

although Pinchot juniper does grow in mixed stands with

Ashe juniper and oaks (Quercus sp.) on the western

Edwards Plateau, it is not a significant component in

woodlands discussed here; this species may grow with oaks

and Ashe juniper to form open woodlands in the far

western Edwards Plateau, but such communities have not

been described in the literature.

Ashe juniper communities are most common in the

southern and eastern Edwards Plateau (Balcones

Canyonlands, Texas hill country) and the Lampasas CutPlain to the north. Both regions are underlain by

Cretaceous limestones, but these are of various types that

weather to form different soils and a wide variety of

different abiotic site potentials for any given geomorphic

position. Thus, site potentials are not only controlled by

slope and exposure, but also may vary across flat uplands,

across gentle slopes, etc., due to subtle differences in

substrate. Climate also varies across the range of Ashe

juniper community types, with annual precipitation ranging

from 20 inches [50 centimeters (cm)] in the west to 34

inches (86 cm) in the east and average January low

temperatures from 37 EF (2.8 EC) in the south to 30 EF (-l.l

EC) in the north. Superimposed on these climatic,

topographic, and edaphic variables are variations in land

use; together these account for the communities on the

contemporary landscape.

Extent of the Original Woodlands

Often-repeated dogma indicates that Ashe juniper has

increased in importance in former grasslands (Amos and

Gehlbach 1988), but the real extent of this increase and its

impact on contemporary woodland and forest distribution

and composition are unclear. Following are some accounts

of the perception of the expansion or contraction of Ashe

juniper communities and a discussion of the composition of

woodlands and forests on uplands and on slopes and creek

bottoms.

Ashe juniper is seen as economically undesirable on

rangeland, and many of the early accounts of its increase

may be traced to human impressions, range science

literature, or other sources primarily interested in

addressing the use of natural resources to generate

economic income (Bray 1904, Beuchner 1944, Huss 1954,

Harris 1958, Smeins 1980, Fuhlendorf 1992). Many of

these sources, however, indicate the presence of a variety of

natural juniper codominated communities, a decrease in

"virgin cedar (old-growth Ashe juniper)" communities, and

the use of juniper and other species for wood products. For

example, Huss (1954) wrote of the use of juniper for posts

and of accounts of the shipment of three trains per week out

of Real County on which " . . . it was not uncommon for a

single train to have a load of 40,000 posts." Contrary to

showing a dramatic increase in juniper woodlands, he
2

wrote, "It is difficult to believe that such timber once

existed in the valley of the Nueces." As evidence that it did,

he noted that one unusual 23,000-acre ranch in Edwards

County still had virgin cedar and calculated its worth at

over $1 million. Beuchner (1944) mapped all of Kerr

County as some type of woodland and 24 percent as cedar

brakes (dense forests dominated by Ashe juniper) and states

that, " . . . a large part of the area now designated as cedar

brakes was originally covered with cedar when white man

made his first appearance . . . ."

As further evidence of the existence of extensive forests on

the Edwards Plateau, Bray (1904) wrote that, "A large part

of the support of the Hill Country population comes from

the sale of wood for fuel," and that, "Cedar is handled at all

points within hauling distance of brakes; but cedar timber

large enough to furnish ties and poles is becoming scarce,

except in remote districts." The following excerpt from

Bray also provides additional insight into the historical

extent of juniper codominated woodlands in the Edwards

Plateau: “With the exception of cedar, the hill country

timber finds a market chiefly as fuel, of which enormous

quantities are consumed, both in stoves and grates and in

the furnaces of lime and brick kilns, gin engines, etc.

Cedar likewise is extensively consumed as fuel and in

charcoal burning, but its great value lies in its yield of

railway ties, poles, posts, sills, and innumerable other

articles which utilize its great durability.”

Pulich (1976), Clark (1985), Weniger (1988), Wahl et al.

(1990), and Keddy-Hector (1992) all document or suggest a

decline in woodlands on the Edwards Plateau. Weniger

wrote that the Edwards Plateau was about half wooded and

half open at the time of European settlement, based on

analysis of survey notes from more than 6,500 witness

trees. Rates of loss range from 20 percent of the "virgin

cedar" from 1962 to 1974, based on Soil Conservation

Service records (Pulich 1976), to 30 percent of all

woodland lost in urbanizing counties from 1974 to 1990,

based on remote sensing data (Keddy-Hector 1992). Most

of this loss was due to land clearing for agriculture and

urbanization.

Old-growth Ashe juniper stands are difficult to find in the

contemporary landscape and may not even be easily

recognizable; certainly, examples of all variants of different

community types with Ashe juniper as a dominant or

codominant do not exist. No accounts were found that

specifically document old-growth stands. I have visited

more than 100 sites that support Ashe juniper woodlands

or forests, and have tentatively identified only 1 as old

growth, and even it had small patches of disturbance (i.e.,

stumps from the removal of individual trees, apparently for

posts). The reasons for disturbance presumably include the

high value of Ashe juniper for timber products and, later,

cedar oil, the extensive clearing of timbered land for use by

domestic livestock, and the less extensive destruction of

woodlands by urban growth.

Upland Woodlands

On disturbed sites, young Ashe juniper sometimes forms

nearly pure stands or grows on repeatedly cleared

rangeland. However, from Bray (1904), Beuchner (1944),

Huss (1954), Wahl et al. (1990), and personal observation,

at least two upland site types support natural juniper-oak

woodlands. These include Bray's "hardscrabble" areas, with

exposed, massive, cracking limestone at the surface.

Hardscrabble areas sometimes occur within extensive

uplands and are also prominent near the lip of canyon rims,

usually extending no more than 100 feet [30 meters (m)]

away from the rim and often restricted to within 33 feet (10

m) of the rim. This substrate supports mainly evergreen or

mixed woodlands, including juniper-shin oak [Q. durandii

var. breviloba (Torr.) Palmer] in the east and central

Plateau, Vasey oak [Q. pungens var. vaseyana (Buckl.)

C.H. Muller] in the west, or juniper-plateau live oak [Q.

virginiana var. fusiformis (Small) Sarg.] communities

throughout. Canopy cover reaches about 90 percent and

height about 26 feet (8 m) in these communities. Lacey oak

(Q. glaucoides Mart. & Gal.) may also be an overstory

species in the south central and southwestern Edwards

Plateau, especially on flats just above canyon rims. Cedar

elm (Ulmus crassifolia Nutt.) and sugarberry (Celtis

laevigata Willd.) are also sometimes important. Common

understory shrubs include Texas persimmon (Diospyros

texana Scheele), mountain-laurel (Kalmia latifolia L.), and

eastern redbud (Cercis canadensis L.). Elbowbush

(Forestiera pubescens), sumacs (Rhus sp.), and agorita

(Berberis trifoliolata) may grow in openings, although

apparently none of these is especially shade tolerant.

A second type of upland woodland with Ashe juniper as a

component is described by Buechner (1944) and Huss

(1954), and from a single stand by Wahl et al. (1990). Soils

are described as red or reddish and may develop over

siliceous limestone or "flintrock" (Hill and Vaughn 1897)

or may represent ancient Pleistocene paleosols or "terra

rosa" as described by Young (1986). These two different

types of substrate may support slightly different types of

woodlands, but, in either case, apparently post oak (Q.

stellata Wangenh.) or blackjack oak (Q. marilandica

Muenchh.) or both, are among the overstory dominants. I

have also observed this type of community in which the

canopy was about 40 feet (12 m) and the community was

relatively open. Huss reported on an Ashe juniper-blackjack
3

oak community type on the “flintrock” divide of Real

County and noted that Lacey oak, bigleaf shin oak

(probably Q. sinuata), and Texas madrone (Arbutus texana

Buckl.) were important components. Beuchner reported

post oak, blackjack oak, and live oak as dominant in this

community type in Kerr County; post oak and Ashe juniper

dominated the stand sampled by Wahl et al.

Slope, Canyon, and Creekside Forests and Woodlands

Ashe juniper and deciduous species are seldom evenly

distributed within uniform woodlands on slopes or in

canyon systems. Rather, deciduous trees and shrubs often

form rather narrow, distinct, linear, horizontal bands from

perhaps 30 to 100 feet (9 to 30 m) wide, associated with

seepage zones near the tops of slopes, and sometimes at

intervals downslope, with wider, mostly evergreen Ashe

juniper bands interspersed up slope and downslope. This

type of banding is especially clear where massive, resistant

limestone forms a thin cap over less resistant materials as

in the vicinity of Post Oak Ridge north of Austin, TX,

where Edwards limestone caps give way to Glen Rose

limestone slopes. Indeed, landscape patterns (i.e., the

degree of incision of canyons, degree of canyon slope,

difference in elevation of plateau tops versus canyon

bottoms, etc.) depend on geologic substrate as well as

drainage patterns. The Balcones Canyonlands region

along the southern and western boundary of the Plateau

harbor some of the most spectacular ravines and the most

extensive slope forests. Slope exposure also influences

community structure, with south exposures more evergreen

and approaching the look of upland woodlands, but with

banding of deciduous trees sometimes still prominent.

Deciduous trees also grow more abundantly in ravine

bottoms, ravine heads, or near streams, and composition

depends both on moisture regime and

landscape/disturbance variables.

Recognition of distinct community types is problematic in

many canyon systems. For example, a series of quadrants

could be placed within deciduous-tree-dominated bands to

define a deciduous forest or within mainly juniperdominated bands to define an evergreen woodland on the

same slope. Different authors have treated this variation

differently; also, some have reliably recognized disturbed

communities versus undisturbed stands while others

apparently have not. I have tried to account for this type of

variation in the following description of slope, canyon, and

streamside community types. The descriptions are based

primarily on data from Beuchner (1944), Huss (1954),

Blair (1965), Kroll (1980), Van Auken et al. (1981),

Gehlbach (1988), Riskind and Diamond (1988), Van

Auken (1988), and Wahl et al. (1990). See especially

chapters in Van Auken et al. (1979, 1980, 1981) and Amos

and Gehlbach (1988) and for quantitative data.

A generalized description of slope woodlands in the

Balcones Canyonlands would show Texas oak and Ashe

juniper among the canopy dominant in most stands. Cedar

elm is usually present in the canopy and is reported as a

dominant in some stands. Plateau live oak, black cherry

(Prunus serotina Ehrh.), Texas ash [Fraxinus texensis

(Gray) Sarg.], scalybark oak [Q. sinuata (Torr.) C.M.

Mull.] = shin oak = bigleaf shin oak = Durand oak (Q.

durandii Buckl.), sugarberry, and Arizona walnut

[Juglands major (Torr.) Heller] are often present in the

canopy, and may be among the dominants. Lacey oak is

important in the central and western sections. Chinkapin

oak (Q. muhlenbergii Engelm.), Carolina basswood (Tilia

caroliniana Mill.), and American elm (U. americana L.)

are sometimes components in wet canyons or in streamside

communities. These mesic forests may have a rather diverse

understory composed variously of Texas persimmon,

yaupon (Ilex vomitoria Ait.), American beautyberry

(Callicarpa americana L.), hoptree (Ptelea trifoliata L.),

Mexican-buckeye (Ungnadia speciosa Endl.), deciduous

holly (Ilex decidua Walt.), redbud, and roughleaf dogwood

(Cornus drummondii C.A. Meyer). Other understory

species may include rusty blackhaw (Viburnum rufidulum

Raf.), Carolina buckthorn (Rhamnus caroliniana Walt.),

red buckeye (A. pavia L.), Texas madrone, Lindheimer's

silktassel (Garrya lindheimeri Dougl. ex Lindl.), and

kidneywood (Eysenhardtia texana Scheele). In a few deep,

moist canyons, bigtooth maple (Acer grandidentatum Nutt.)

is among the dominants and may form stands in which it

comprises more than 70 percent of the relative cover as in

Lost Maples State Natural Area. In the south central and

southwest portions of the Edwards Plateau, isolated oakjuniper-pinyon and mainly evergreen woodlands grow on

uplands, but are best developed in shallow canyons and

canyon heads.

Table 1 summarizes communities and dynamics. Only Van

Auken et al. (1981), Gehlbach (1988), and Van Auken

(1988) have provided data on relatively mature stands,

although perhaps none of the stands sampled could be

characterized as old growth.

Old-Growth Definitions

Ashe juniper is a component of at least three different but

related community types, including (1) upland mainly

evergreen to mainly deciduous woodlands on fractured,

massive limestone in flat uplands and on canyon rims; (2) 
4

Table 1—Major pre-European woodland and forest community types of the Edwards Plateau with Ashe juniper as a

component

Landscape position, Characteristics of Fire frequency Relative diversity

Community type soils, and geology the community and type of woody species

Plateau live oak- Flat or rolling uplands; Open grassland or High; ground fires Low

Ashe juniper soils fairly deep and of savannah with with few crown fires

relatively uniform depth individuals or mottes

of oak; Ashe juniper

and other tree species

in mottes

Post oak/blackjack Flat or rolling uplands; Savannah to well- High to medium; Medium

oak-Ashe juniper soils over silica- developed woodland; few crown fires

containing limestone or Ashe juniper and other

composed of Pleistocene tree species in dense

terra rosa mottes or better

developed woodlands

Scalybark oak/Vasey Flat or rolling uplands Shrub land or woodland Medium to low; Medium to high

oak (west)-Ashe or canyon rims; soils depending on fire some crown fires

juniper over massive, fractured frequency; Ashe juniper

limestone and of increasing with time since

variable depth previous burn

Ashe juniper-Texas Slopes, canyons, Evergreen woodland (dry Low to very low; High

oak/deciduous creek sides exposures/dry slopes) to crown fires at low

tree species deciduous forest (wet return intervals

exposures, seeps, creek

sides; vegetation forming

horizontal bands)

mainly deciduous woodlands over either terra rosa or silicacontaining limestone on uplands; and (3) forests and

woodlands on slopes, in canyons, and along streams.

Generalized characteristics of these community types in

terms of tree size and density for old-growth conditions

follow. These, however, are based on the data available,

and at best are hypothetical extrapolations, because few

authors have described mature, let alone old-growth stands.

Upland Hardscrabble

Live oak and Ashe juniper were and are growing under less

disturbed conditions, often the leading dominant of

woodlands or mottes (clumps) on relatively deep,

continuous soil of flat uplands on much of the Plateau,

whereas scalybark oak and Ashe juniper dominated

hardscrabble areas (Bray 1904, Beuchner 1944, Van Auken

et al. 1981, Gehlbach 1988, Van Auken 1988). Scalybark

oak, and perhaps Texas oak, apparently sometimes formed

dense "shinneries" (Bray 1904) in which multiple-stemmed

individuals formed low canopies in response to fire; Bray

reports that these shinneries contained a mixture of species,

including live oak, sugarberry, and sumac. Post oak and

blackjack oak may also grow in these hardscrabble areas.

The live oak-juniper woodlands may indeed represent

former climax savannahs or grasslands and the shin oakjuniper climax woodlands. The mature canopy height of

these communities is about 26 to 30 feet (8 to 9 m) (Kroll

1980, Wahl et al. 1990). Canopy closure in mature stands

reaches about 90 percent and basal area about 40 to 50 feet2

per acre [40 to 50 m2 per hectare (ha)] (Van Auken 1988).

Number of trees over 1.2 inches (3 cm) diameter at breast

height (d.b.h.) ranged from 1,155 to 1,465 per acre (2,841

to 3,605 per ha) (Van Auken 1988). The average d.b.h. of
5

mature canopy trees reported by Gehlbach for scarp edges

was 13 inches (34 cm) for scalybark oak, 14 inches (36 cm)

for cedar elm, and 16 inches (41 cm) for plateau live oak.

Harris (1958) reported that "little leaf shin oak" (probably

Q. vaseyana) on the west central Edwards Plateau reached

6.5 inches (16 cm) d.b.h. and 76 years old on upland sites.

Ashe juniper in Real County was 70 to 100 years old at 5 to

6 inches (13 to 15 cm) d.b.h. and reached 10.5 inches (27

cm) d.b.h. and 172 years old (Huss 1954). However, few or

no "virgin cedar brakes" were found in Real County. Kroll

(1980) found Ashe junipers as large as 16 inches (40 cm)

d.b.h. and more than 100 years old.

Only one stand of this community type was apparently old

growth among dozens I visited. Ashe juniper was the

leading dominant occupying more than 80 percent of the

relative canopy cover, which reached 26 to 30 feet (8 to 9

m). The d.b.h. of large canopy trees was estimated at more

than 18 inches (45 cm), but many smaller individuals

reached the canopy. Canopy trees were flat-topped (less

mature junipers have pointed tops with easily identifiable

apical growing points) and total canopy cover was

estimated about 80 percent. Scalybark oak, Texas oak, and

live oak were also in the canopy and the understory

contained a few tall, spindly Texas persimmons. The aspect

was open under the canopy, with few low branches; this

contrasts with younger stands of juniper, which are often

nearly impenetrable due to low branching of junipers or

dense growth of many individual stems. Recruitment was

mainly seedling Ashe juniper, but there were almost no

sapling trees. Numerous large, downed junipers occurred

(probably as many as 10 percent of the number of live trees

standing) and I saw one standing dead tree. Despite this, I

could detect no old light gaps, which suggests that the

death of individual junipers, whose canopies are small,

does not dramatically affect forest dynamics. The ground

layer was lush; apparently enough diffuse light penetrated

the canopy to support grass.

Upland Flintrock or Terra Rosa Soils

Over upland flintrock (siliceous limestone) or terra rosa

soils, Ashe juniper occurs mixed with post oak and

blackjack oak. Fire may have historically diminished the

dominance of Ashe juniper. Buechner (1944) reported

blackjack oak, live oak, and post oak in over 90 percent of

the 5-acre stands of this community type sampled in Kerr

County (number sampled not reported); canopy coverage

was highest for blackjack oak and intermediate for post oak

and live oak. Ashe juniper was present in 70 to 90 percent

of the stands but provided less than 1 percent of the canopy

coverage in 75 percent of those in which it occurred. Wahl

et al. (1990) found post oak dominating one stand with a

density of 180 trees per acre (73 trees per ha) and a mean

height of 26 feet (7.9 m). Ashe juniper was the next most

important species with a mean of 393 trees per acre (159

trees per ha) and a mean height of 17 feet (5.3 m). Total

canopy cover of the stand at 16 feet (5 m) was 21 percent.

The tallest post oaks were over 45 feet (12 m), whereas the

tallest junipers were over 26 feet (8 m); this corresponds to

observations of similar stands. My vision of this type of

community in an old-growth stand is that of an open

woodland with 40 to 60 percent canopy at about 45 feet (12

m) with scattered post oak and blackjack oak along with

dense mottes of these species in which Ashe juniper is a

component.

Slope, Canyon, and Creekside Communities

Van Auken (1988) reported north slope communities with

a total basal area of 168 ft2 per acre (38.6 m2 per ha) and

total tree density of 729 per acre (1,851 per ha). Gehlbach

(1988) reported mean d.b.h. of canopy trees on slopes and

floodplains in the range of 15 to 17 inches (38 to 44 cm)

for Texas oak, Texas ash, sugarberry, cedar elm, and

scalybark oak. Various sources report average canopy

height to be 39 to 49 feet (12 to 15 m). An unusual stand

dominated by bigtooth maple, Texas oak, and Lacey oak,

sampled by Wahl et al. (1990), contained canopy trees 33

to 46 feet (10 to 14 m) tall and a total canopy cover of 145

percent, due to overlapping layers of tree canopy. My vision

of an old-growth slope community includes a diverse,

essentially interlocking canopy of mainly deciduous trees

and Ashe juniper at about 49 feet (15 m) tall and a diverse

understory of mainly deciduous shrubs. However, junipers

and deciduous species are usually not evenly intermixed but

form distinct patches or bands. 

Forest Dynamics and Ecosystem Function

Fire greatly helped control the distribution of vegetation on

the Edwards Plateau prior to European settlement. Smeins

(1980) and Fonteyn et al. (1988) concluded that frequent

fires, set by lightning or Native Americans, were so

common on the Plateau that flats and rolling hills,

especially outside of the hill country, were maintained as

open grassland. Effects of fire on the Plateau are

summarized by Amos and Gehlbach (1988):

Indeed, fire may have been the single most important,

non-edaphic factor controlling patterns of vegetation.

The historic Plateau was likely a mosaic of woodland

along the rocky scarps and in canyons (fires
6

infrequent), forest along the creeks and rivers (also

infrequent fire), and grassland in the uplands where

comparatively deep soil and fire were more frequent.

Occasional trees, especially plateau live oaks, grew on

the uplands, root- and stump-sprouted into clumps

(mottes) due to fire and perhaps browsing disturbance

and fostered the establishment of commensals like

Ashe juniper and Texas persimmon because of the

cool, moist, fire-resistant carpet of thick oak leaves.

Wells (1965) concluded that extensive scarp woodlands in

the Great Plains are a result of the protection from fire.

Similarly, the natural woodlands of the Edwards Plateau

may likewise have been the result of protection of canyons

and scarps from fire. Thus, mesic woodlands and forests

codominated by juniper could have been protected from fire

and maintained in canyons. Hardscrabble areas in the

uplands, with massive limestone exposed at the surface,

may also have prevented accumulation of fine fuel and

prevented frequent fires. In fact, some hardscrabble areas

are raised slightly above the surrounding flat uplands

[perhaps 3 feet (1 m) on Post Oak Ridge north of Austin,

TX] and, hence, not only act as scarps but actually are low

scarps. But were fires frequent enough in these flat or

rolling areas to exclude Ashe juniper, which is not resistant

to fire? In some areas probably so, in others probably not.

The dynamics no doubt were controlled by

geologic/edaphic variables, such as (1) the size of the

hardscrabble area; (2) the degree of exposure of rock or

thin soil; (3) the water and nutrient relations of the soil

and, hence, its ability to support trees; and (4) the lay of the

land (i.e., distance to the nearest fire break in the form of a

scarp or stream and its relation to prevailing winds, etc.).

Certainly, juniper is favored on the modern landscape not

only by the absence of fire but also by its rapid seed

dispersal and low palatability to browsers. However, even

today in areas of continuous soils on the flat central and

western Edwards Plateau, junipers are not as abundant as

in areas of shallow or discontinuous soils. In fact, many

areas approach the motte-like appearance described by

Amos and Gehlbach (1988) where, except for the existence

of junipers in mottes, the landscape has few junipers.

Therefore, it is not hard to imagine how frequent fire could

have excluded junipers from openings between live oakAshe juniper mottes on deeper or more continuous uplands

(Smeins 1980).

Bray (1904) provides some clues to the timing and nature

of large-scale community dynamics when he describes

shinneries, which covered upland hardscrabble, as being

composed of a mixture of species, some of which are not

fire tolerant. Also, he notes that fire was so frequent in

cedar (Ashe juniper) that "It is probable that during the

past twenty-five years far more cedar timber has been

burned than has been marketed, and vastly greater areas

denuded by fire than by the axe." He goes on to state that

cedar generally replaces itself on these burned areas.

However, he quotes one "reliable" source as saying "When

the (cedar) brakes are burnt out they never recover, but very

soon grow up with different kinds of brush . . . . Some of

my own cedar was burned about five years ago, and the

ground is now covered with shin oak and Spanish oak

sprouts."

Obviously, the oaks were a part of the "cedar brake" before

it burned. Could this have been the formation of a new

shinnery and might that area, if not burned for decades,

have been reinvaded by juniper to form a cedar brake and

perhaps then burned again to reform a shinnery? This type

of decades-long dynamic is likely for upland woodlands of

the Edwards Plateau. For example, Huss (1954) described

the interaction of grazing by domestic livestock and fire

and concluded that a juniper-oak community will succeed

after burning to a new juniper-oak community within 60

years under various grazing regimes, although the

abundance of secondary species can be controlled by

grazing pressure. Presumably a canopy fire could restart the

process at any stage, but would become more likely as the

canopy of Ashe juniper closed.

The existence of blackjack oak and post oak communities

containing Ashe juniper on uplands is probably explained

by edaphic factors interacting with fire. Both of these oak

species are known in Texas on deep, slightly acid soils of

the Post Oak Savannah and Cross-Timbers. The terra rosa

and siliceous flintrock soils on which post oak and

blackjack oak communities grow best have slightly lower

pH values (often below 7.0), a different nutrient content,

and perhaps better moisture relations than do most

"typical" limestone-derived soils. Both blackjack oak and

post oak are fire tolerant and, thus, in pre-European

settlement times may have grown as scattered individuals

or may have formed mottes or rather extensive, diverse,

deciduous woodlands or forests, depending on subtle

differences in substrate, fire history, and landscape

position.

Drought also greatly influences woodlands on the Edwards

Plateau. The drought of the fifties killed many oaks and

junipers. Harris (1958) wrote "During the periods of

detailed study in 1952 and 1953 the extended drought had

not hindered littleleaf shin oak (probably Quercus

vaseyana), although many plants of live oak, Spanish (=
7

Texas) oak, and large areas of cedar were dead from the

drought . . . . In August 1957, after extended drought from

1951 through 1956, it was noted that many littleleaf shin

oak mottes were dead."

Standing dead junipers can still be seen on the western

Edwards Plateau. Young (1956) likewise noted changes in

vegetation due to the drought of the early 1950's and

chronicled the death of many woody plants on the Sonora

Research Station in the west central Plateau.

Other than the obvious impracticality of allowing hot

wildfires to burn in an urbanizing region, or at least of

controlling large enough areas to make such a strategy

practical and the inability to control drought cycles, the

primary controllable influence on the current woodlands is

browsing. Van Auken (1993) and a host of others (Amos

and Gehlbach 1988) have noted that browsing by domestic

livestock and white-tailed deer may reduce recruitment of

palatable woody species such as Texas oak. Establishment

of these species may have in the past responded to fire or

drought cycles, and may have in the past 100 years

responded to rapid human clearing of patches of from a few

to hundreds of acres for range improvement or the

harvesting of wood products. Certainly, browsing by

confined domestic livestock and introduced feral species

and the control of hot wildfires may change community

composition over time. However, the type and extent of

these possible changes is not certain. For example, the

establishment of only a few trees may ensure their

representation in old-growth communities, especially if

these species have large, spreading canopies. Palatable

species, such as Texas oak, cedar elm, and sugarberry, are

still major components of mature woodlands and forests

despite a 100-plus-year history of human settlement, land

clearing, and grazing of domestic livestock. Thus, the

effects of overbrowsing and control of wildfire could be less

dire for these species than it might appear.

Conservation of Ashe juniper and related woodlands and

forests of the Edwards Plateau is of high concern,

according to Diamond et al. (1987) and the Texas Natural

Heritage Program (TNHP)2. While not imminently

imperiled, these communities are threatened by expanding

urbanization and agriculture, especially land clearing for

range improvement. Of 80 sites supporting variations of

Ashe juniper codominated communities in the TNHP

database, only 6 are listed as excellent or good to excellent

quality (i.e., old growth).

Conserving the biodiversity within the major variants of

Ashe juniper dominated or codominated woodlands would

require managing representative examples of each major

topographic and edaphic type (upland hardscrabble, upland

terra rosa or flintrock, and slope/canyon/creekside) within

different regions of the Edwards Plateau. Carefully located

preserves might capture all three habitats within a single

30,000-acre (1,181-ha) area, although the immediate

practicality of acquiring land from willing sellers or

easements from private landowners so that such an area

could be managed as a unit is questionable. The

management strategies for such an area might include

removing domestic livestock and reducing deer and feral

ungulates, prescribed burning, and restoring heavily

impacted woodlands to reduce fragmentation where forests

have been cleared in the past. Recalling the importance of

hot as well as cool fires in pre-European settlement times,

an area large enough to allow such a burn policy would be

practical only for a very large preserve, especially

considering the likelihood of special management

requirements for rare species.

The Edwards Plateau, in general, and especially the

Balcones Canyonlands or hill country, have long been

recognized as important centers of endemism and

biological diversity for both plants and animals (Blair

1950, Amos and Rowell 1988). Ashe juniper codominated

woodlands are the defining component of this region.

Several rare or endemic endangered species are indigenous

to these woodlands, including the golden-cheeked warbler

(Dendroica chrysoparia) and the black-capped vireo (Vireo

atricapillus). These species are currently in the center of a

controversy over the effects of the Endangered Species Act

on private property rights in central Texas. Attempts to

conserve juniper woodlands and forests in this region

would need to address the habitat requirements of these

species.

Representative Old-Growth Stands

Representative old-growth forests on the Edwards Plateau,

southern Great Plains occur at the following locations:

C Balcones Canyonlands National Wildlife Refuge, Travis

and Williamson Counties

C Bull Creek Drainage, Travis County

C Emmous Retreat, Travis County

C Guadalupe River State Park/Honey Creek State Natural

Area, Comal County
8

C Fort Hood, Bell and Coryell Counties

C Garner State Park, Uvalde County

C Lost Maples State Natural Area, Bandera County

C Mother Neff State Park, Coryell County

C Pedernales Falls State Park, Blanco County

Consult TNHP database for locations of these and other

examples of Ashe juniper-oak series woodlands and forests.

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9

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Diamond, David D. 1997. An old-growth definition for western juniper woodlands: Texas

Ashe juniper dominated or codominated communities. Gen. Tech. Rep. SRS-15. Asheville,

NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 10 p.

Ashe juniper dominated or codominated woodlands are extensive within the Edwards Plateau

in Texas. Almost all contemporary woodlands are the result of various disturbances, especially

grazing and fire suppression. Old-growth examples are rare. Several different geomorphic

situations once supported natural Ashe juniper communities with different dynamics and

composition. These included mesic slopes and canyon systems, shallow-soiled uplands

(hardscrabble), and deeper-soiled uplands. The most extensive and most diverse woodlands

were in canyon systems, where Ashe juniper shared dominance with a diversity of oaks and

other broad-leaved trees. Drier upland woodlands were less diverse, with live oak, shin oak,

and Vasey oak variously important. Ashe juniper woodlands harbor a diverse biota, including

rare and endemic species, and, thus, preservation of representative old-growth examples is an

important conservation concern.

Keywords: Ashe juniper, Edwards Plateau, hill country, vegetation.
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