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Arroyo-Riparian Shrub Diversity Along a
Transition Zone Between the Sacramento
Mountains and Tularosa Basin, New Mexico
Joneen S. Cockman
Rex Pieper
Dennis Clason
The importance of arroyo-riparian or ephemeral drainages for birds has been well documented (Carothers and
others 1974; Carothers and Johnson 1975; Finch 1989;
Reichenbacker 1984). Floral structure variables such as
patchiness, volume, and foliage height diversity were found
to be not independent of one another (Anderson and Ohmart
1980). Instead, variable complexes were identified as well as
ties between bird use and time of year.
Abstract-Four arroyos were examined in the Sacramento Mountains of New Mexico to determine type differences and describe
vegetation diversity of the main channel relative to the surrounding
watershed. Arroyos were selected to represent foothills and a
submesa. Univariate analyses were conducted on shrub, half-shrub,
grass, and forb functional groups. Each group responded to different
effects depending on the response variable (cover, density, diversity). However, nonsignificant interactions were masked by the fact
that response variables (especially diversity) were comprised of
different species depending on the location of the arroyo in foothill
or submesa types. Obligate and exclusive species were identified.
Research Purpose _ _ _ _ _ __
At this time, environmental regulations do not protect
arroyo habitat. Data are needed to support management
decisions related to environmental quality.
Interest and concern for the protection of wetlands has
increased since the inception of the National Environmental
Policy Act (NEPA) of 1969. Four Federal agencies provide
regulating authority for wetlands. These are the U.S. Army
Corps of Engineers (USACE), the Environmental Protection
Agency (EPA), the U.S. Fish and Wildlife Service (USFWS),
and the Natural Resources Conservation Service (NRCS).
Each agency provides a different definition of a wetland
depending on the agency's function. However, all agencies
include in their definition three basic elements: hydrology,
vegetation, and soil characteristics (Mackenthun and
Bregman 1992).
The USEPA and USACE have adopted the definition of
wetland from the Clean Water Act Section 404 (Mackenthun
and Bregman 1992):
It has been suggested that arroyos in the southwestern
United States are of recent origin, and are a feature of
accelerated erosion on once-uniform grasslands and cienegas
(Cooke and Reeves 1976; Bryan 1925). Antevs (1952) borrowed the term "wadis" from Israeli and Egyptian literature
to describe ephemeral drainages that are not features of
man-caused erosion. These drainages are limited to the
headwaters of valleys, occur in moist areas, and are limited
in size. The typical drainage described by Antevs is 3.6
meters deep, 15 meters wide, and .8 km long. The drainages
of this study more closely resemble Antev's description of a
"wadis."
Classification ofriparian communities has been conducted
by Pase and Layser 1977; Freeman and Dick-Peddie 1970;
Anderson and Ohmart 1980). Apache plume (Fallugia
paradoxa) has been described as the most commonly found
riparian species in New Mexico, with more than 80% of the
arroyos in a southern New Mexico study containing this
shrub (Browning 1989). Littleleafsumac (Rhus microphylla)
and cutleafbricklebush (Brickellia laciniata) were listed as
close associates in areas of approximately 1,500 meters elevation. Burrobush (Hymenoclea monogyra) was listed as an
associated species in washes at lower elevations (Browning
1989). The four arroyos described in this report resemble
closely the Apache plume series described by Browning
(1989) and also contain Burrobush at lower elevations.
Those areas that are inundated or saturated by surface or
groundwater at a frequency and duration sufficient to support,
and that under normal circumstances do support, a prevalence
of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs and
similar areas.
It is important to note that this definition identifies
saturated soil conditions and a prevalence of vegetation
suited to saturated soils. The presence of indicator species
such as cattails that grow only in saturated conditions has
been used to identify wetlands.
Arroyos and wadis do not contain saturated soil conditions
and do not qualify as a wetland by the USEPA definition.
However, they do support plant species that will grow on no
other site. They also support a variety of wildlife species and
appear to be critical habitat.
However, little research has been done to quantify plant or
animal species occurring in the arroyos. Studies are needed
In: Barrow, Jerry R.; McArthur, E. Durant; Sosebee, Ronald E.; Tausch,
Robin J., comps. 1996. Proceedings: shrubland ecosystem dynamics in a
changing environment; 1995 May 23-25; Las Cruces, NM. Gen. Tech. Rep.
INT-GTR-338. Ogden, UT: U.S. Department of Agriculture, Forest Service,
Intermountain Research Station.
Joneen S. Cockman and Rex Pieper are Research Assistant and Professor
of Range Science, Department of Animal and Range Sciences; Dennis Clason
is Professor, Department of Experimental Statistics, New Mexico State
University, Las Cruces, NM 88003.
230
to test if the arroyo does support unique species or a higher
diversity compared to the adjacent watershed.
The purpose of this research is to describe and quantify
vegetation along ephemeral drainages in the Sacramento
Mountains of southern New Mexico. The study will provide
baseline data to facilitate management decisions pertaining
to NEPA compliance. The focus of the study is to test for
vegetation differences between foothill and submesa arroyos. It also examines the main channel relative to adjacent
vegetation types, and adds to our knowledge of these important habitats in the Southwest.
The annual average rainfall for the area is about 30 cm.
However, there is a rain shadow between the submesa and
foothill. No rain gauge data are available to quantify the
difference between sites. However, a difference in vegetation between the sites suggests that the foothill area receives
much greater rainfall. Also, many people who have worked
in the area and have observed the weather pattern agree
that thunderstorms build up over the Sacramento Mountains and flow south over the foothills. They have observed
torrential rainfall in the foothills while the submesa area
receives little or no rainfall. This pattern appears to be a
frequent occurrence.
Soils of the area are dominated by rock outcrop and
limestone hills. Gravelly alluvium is prevalent on the lower
slopes. Narrow bands of alluvial soil line the arroyos. Of
particular interest is a major separation in soil classification
between the foothill and submesa areas. The submesa is
mapped in southern desert soils while the foothill is mapped
in soils from the neighboring mesic region. This is a transition zone between the true desert soils and cooler plains
soils.
Study Area _ _ _ _ _ _ _ __
The study area contains four arroyos particular to the
research and one major drainage that connects the four
(fig. 1). The area occupies approximately 13,000 hectares
and is used jointly by the Bureau of Land Management as a
grazing allotment and a wilderness study area. It is also
designated military ground, identified as McGregor Range,
a portion of the Fort Bliss military establishment.
Located at the southern tip of the Sacramento Mountains,
the area is approximately 16 air km northeast from the
village of Orogrande, NM, and 112 km northeast from
EI Paso, TX. Elevation ranges from 1,200 meters to 1,600
meters. Two of the arroyos (Indy and Carly) are located in a
foothill area. The headwaters of these arroyos originate at
approximately 1,800 meters, and the tailwaters drain into
Culp Canyon at approximately 1,670 meters. The other two
arroyos (Alien Temple and Four Bucks) are located on a
submesa. Their headwater originates at the j unction ofCulp
Canyon at approximately 1,500 meters, and they drain into
the Tularosa Basin at approximately 1,370 meters.
Methods _ _ _ _ _ _ _ _ __
Site Selection
Field reconnaissance using soil maps and aerial photos was
conducted prior to selecting study sites. Two similar arroyos
(Indy and Carly) were selected in a foothill area (fig. 1). Two
more (Alien Temple and Four Bucks) were selected within a
submesa area. The submesa is positioned between an upper
mesa with sharp vertical boundary and the Tularosa Basin.
The land is hummocky and slopes gently between the mesa
and basin. The foothill arroyos flow into a major drainage
(Culp Canyon), and the submesa arroyos originate from
Culp Canyon. The foothill arroyos are about 2.4 km in
length. They range from 3-15 meters wide. The submesa
arroyos are approximately 11 km long, and range from 2-30
meters wide. All arroyos range from 0.5-3 meters deep.
Sample locations were selected along each arroyo at headwater, midwater, and tailwater locations (upper, middle,
and lower elevations) (fig. 2). An attempt was made to
identify all vascular plant species in the study area. Plants
too immature to identify were catalogued, and phenology
was recorded. These plants were collected again when mature specimens were available. Vouchers were collected
from as many species as possible to aid in accurate identification. This paper provides results pertaining to two shrubby
functional groups, half-shrubs and shrubs. The half-shrub
group contains cacti because cacti were infrequent and low
in number in the study area. This was done to follow their
presence rather than delete them from analyses. Similarly,
the large shrub group includes trees because trees were
infrequent in the study area.
Figure 1-Location of arroyos in a 13,000 ha BLM
grazing allotment. Indy and Carly arroyos are located in
a foothill area. The headwater portions of these arroyos
originate at approximately 1,800 meters and drain into
Culp Canyon at about 1,670 meters. The headwaters
of Four Bucks and Alien Temple arroyos originate in
Culp Canyon at about 1,500 meters. They drain into the
Tularosa Basin at about 1,370 meters. They are located on a submesa. Sample locations are marked on
each arroyo at lower, middle, and upper elevations.
Scale: grids represent 1 mile x 1 mile.
Response Variables
Cover, density, and presence of all vascular plant species
were measured for the greater study. This paper is limited
to a discussion of diversity based on species richness which
is derived from presence data. Belts with six replicate
231
I
MlDW. TER PLOTS
Figure 2-Sample locations were selected along each
arroyo at headwater, midwater, and tailwater locations
corresponding to upper, middle, and lower elevations.
Alluvium, flank, and upland plots are paired by northwest
and southeast exposure. The main channel plots are
singular and contribute to an unbalanced treatmentstructure. Alluvium is missing at headwater locations, which
also contributes to an unbalanced treatment structure.
subplots were used to facilitate data gathering. Obligate
species are also discussed.
Table 1-Response of species richness to treatment effects.
Functional group
Effect
Analyzing an Unbalanced Treatment
Structure
Shrubs and trees
Elevation x position
OF = 5, error = 16
Elevation x position
OF =5, error = 16
Half-shrub and cacti
Two features of the experimental design are unbalanced
and required that separate tests be conducted to facilitate
one overall F -test in the analyses of variance. First, by
nature of the arroyos, alluvium positions are absent from
headwater zones (fig. 2). This required significance levels to
be extracted from a series ofthree tests: a test with the whole
arroyo, a test with no alluvium, and a test with no upper
elevation. Second, the main channel belts are singular in an
elevation zone where alluvium, flank, and upland belts are
paired by northwest and southeast exposure. So, two separate tests were run to facilitate this imbalance (1) the main
channel-v- northwest exposure and (2) the main channel-vsoutheast exposure. A total of six F -tests were conducted to
facilitate the unbalanced data.
0.0343 NW exposure
0.0056 SE exposure
0.0425 NW exposure
0.1813 SE exposure
elevation with an increase in species richness moving away
from the main channel. A similar response was seen for the
middle elevation positions. That is, species richness was
greater at the highest elevation in the main channel. It
decreased in the main channel with a decrease in elevation
'E
Q)
CIl
10
0..
8
~
CIl
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Analyses of Species Richness
Q)
c.
(f)
Univariate analyses were conducted using SAS General
Linear Models (GLM) procedure. Data were averaged across
species within a functional group. Appropriate error terms
were selected for nested and crossed sampling structure.
The analyses of variance for species richness is presented in
table 1.
12
0
ci
z
6
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r-
2 f--
f-
4
0
-
I-
r-
f-
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f-
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-
f-
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l-
I-
-
l-
I-
-
l-
f- . -
~
L-M L-A L-F L-U M-M M-A M-F M-U U-M U-F U-U
ELEVATION * POSITION
1_
NW-MC
!ill SE-MC
Figure 3-Half-shrubs and cacti were most sensitive to an elevation x position effect for species
richness. Elevation = lower (L). middle (M), and
upper (U). Position = main channel (M). alluvium
(A), flank (F), and upland (U). NW-MC = main
channel and poSitions with a northwest facing exposure. SE-MC = main channel and positions with a
southeast facing exposure. Standard error for all
treatments (NW-MC = 1.016, SE-MC =0.973).
Half-Shrubs and Cacti
Univariate analyses for the species richness ofhalf-shrubs
and cacti was most sensitive to an elevation x position effect
(northwest exposure Pr > F = 0.0425, southeast exposure Pr
> F =0.1813). The submesa and foothill types were averaged
in figure 3. The least species richness was seen at the lowest
232
i---
-
-r
1
along the drainage channel. However, species richness "increased while moving perpendicular away from the main
channel and ascending along the position gradient from
alluvium to flank to upland. This relationship was seen in
the lower and middle elevation zones. However, the upper
elevation zone showed a decrease in species richness moving
away from the main channel. Species richness ranged from
a low of 5.5 species per belt to a high of 11 species per belt.
Significant comparisons are presented in tables 2a and 2b.
per belt to 10.5 species per belt. The main channel position
produced the highest species richness of shrubs and trees
with each elevation zone. This increase is probably due to the
presence of true obligate riparian species as well as facultative species that also occur on other positions. Significant
comparisons are presented in tables 3a and 3b.
Obligate Species _ _ _ _ _ __
Obligate riparian and upper watershed species were identified in separate analyses for the foothill and submesa types
(table 4). In the foothill, species were combined from both
Indy and Carly arroyos. Data included all species recorded
in cover, density, and presence records. Data were sorted by
position across all elevation zones. Thus, the species list for
a position represents the full length of an arroyo from
headwater to tailwater. Submesa data were handled the
same way by combining observations from Alien Temple and
Four Bucks arroyos.
Riparian obligate species were identified by selecting
species that were found in the main channel or alluvium
positions but did not occur in other positions. The procedure
Shrubs and Trees
Analyses of species richness for shrubs and trees were
most sensitive to an elevation x position effect (northwest
exposure Pr > F = 0.0343, southeast exposure Pr > F =
0.0056). Differences between northwest and southeast exposure can be seen within elevation zones (fig. 4), suggesting
an elevation xexposure interaction. However, exposure data
are from separate tests, and comparisons between exposures are speculative. Significant changes in species richness across position can be seen within the lower and upper
elevation zones. Species richness ranged from 4.25 species
Table 2a-Significant comparisons for species richness of half-shrubs and cacti. Data are for the main
channel and positions on the northwest exposure.
L-MC
L-A
L-F
L-U
M-MC
M-A
M-F
M-U
U-MC
U-F
u-u
L-MC
L-A
L-F
L-U
M-MC
M-A
M-F
M-U
U-MC
U-F
U-U
H: LS mean (i) = LS mean (j).
Pr> T = 0.05.
Table 2~Significant comparisons for species richness of half-shrubs and cacti. Data are for the main
channel and positions on the southeast exposure.
L-MC
L-A
L-F
L-U
M-MC
L-MC
L-A
L-F
L-U
M-MC
M-A
M-F
M-U
U-MC
U-F
U-U
H: LS mean(i) = LS mean (j).
Pr > T =0.05.
233
M-A
M-F
M-U
U-MC
U-F
U-U
E
12.---------------------------------------~
recognizes the alluvium. position as an integral part of the
riparian channel. In the submesa type, it functions as a flood
plain for the collection of soil and debris from the main
channel during heavy rainfall events. In the foothill type, it
functions as a flood plain for the collection ofmaterial from the
main channel, and it collects runoff from lateral drainages.
Upper watershed obligate species were identified as those
species recorded on flank or upland positions but not recorded elsewhere.
~ 10+---------------------------
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6
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4
(5
ci
Z
2
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L-M L-A L-F L-U M-M M-A M-F M-U U-M U-F U-U
ELEVATION * POSITION
1_
NW-MC _
SE-MC
1
Shifting of Obligate Species Between
Types
Figure 4-Shrubs and trees were most sensitive to an
elevation x position effect for species richness. Elevation = lower (L), middle (M), and upper (U). Position =
main channel (M), alluvium (A), flank (F), and upland
(U). NW-MC = main channel and positions with a
northwest facing exposure. SE-MC = main channel
and positions with a southeast facing exposure. Standard error for all treatments (NW-MC = 0.764, SEMC = 0.714).
Some shifting of obligate species occurred between the
foothill and submesa types. For example, David's mint
(Salvia davidsonii) was a riparian obligate species in the
foothill type, but occurred as an upper watershed species in
the submesa type. Apache plume occurred as an obligate
riparian species in the submesa type, but was not obligate in
the foothill type because it occurred in the riparian zone as
well as the flanks and uplands. The foothill type is mesic
enough throughout the watershed to support it in many
Table 3s-Significant comparisons for species richness of shrubs and trees. Data are for the main
channel and positions on the northwest exposure.
L-MC
L-A
L-F
L-U
M-MC
M-A
M-F
M-U
U-MC
U-F
u-u
L-MC
L-A
L-F
L-U
M-MC
M-A
M-F
M-U
U-MC
U-F
U-U
H: LS mean(i)
Pr> T = 0.05.
=LS meanG).
Table 3b-Significant comparisons for species richness of shrubs and trees. Data are for the main
channel and positions on the southeast exposure.
L-MC
L-A
L-F
L-U
M-MC
L-MC
L-A
L-F
L-U
M-MC
M-A
M-F
M-U
U-MC
U-F
UU
H: LS mean(i)
Pr > T = 0.05.
= LS meanG).
234
M-A
M-F
M-U
U-MC
U-F
U-U
Table 4-Species obligate to the riparian zone or upper watershed.
Shrubs and trees
The test with all 4 arroyos produced among riparian
obligate species 47 forbs, 9 grasses, one half-shrub, 6 shrubs,
and one tree species. The same test produced among upper
watershed obligate species 6 cacti, 16 forbs, 3 grasses, 1 halfshrub, and 5 shrub species. These lists are larger than those
produced for either the foothill or submesa types alone. This
is a reflection in the shift in species composition between the
two arroyo types.
It is interesting to note certain characteristics of individual obligate species relative to the overall vegetation
story. The main channel position is filled with woody vegetation. Yet, the only obligate riparian half-shrub is burrobush.
Similarly, the submesa type uplands are dominated by halfshrubs, but no obligate half-shrubs were recorded there.
No obligate cacti were recorded for the riparian corridor.
Most cacti in the study area occupy rocky habitat in upland
positions. Trees were scattered and infrequent in the study
area. Most occurr~nces were in the foothill type. Sugar
hackberry (Celtis laevigata) was the only obligate ripanan
tree. However alligator juniper (Juniperus deppeana), oneseed juniper (J. monogyra), pinyon pine (Pinus edulis), and
oak (Quercus spp.) occurred infrequently in the foothill type.
Obligate riparian shrubs for the whole study area are
limited to Guadalupe brickellia (Brickellia brachyphylla),
cutleaf brickelbush, desert willow (Chilopsis linearis), smooth
mountain mahogany (Cercocarpus montanus var. glaber),
Mexican silktassel (Garrya ovata subsp. goldmanii), and
hybrid sumac (Rhus trilobata xmicrophylla). The first three
shrubs are completely senescent and easily recognizable as
riparian species. The latter three species may not be obligate
riparian species in all habitats. Three species of mountain
mahogany are recognized in the Trans Pecos region (Powell
1988). Two of the three species occur in this study. Shaggy
mountain mahogany (C. m. var .paucidentatus) occurs throughout the foothill type. Smooth mountain mahogany has a treelike growth form in the main channel where it occurs
infrequently. But, it has been reported to grow in upland
positions in Brewster County Texas (Powell 1988). Mahogany are important browse plants. They are senescent but
lose their leaves slowly. Mexican silktassel is evergreen. It
is known to grow in upland positions where there is ample
water concentrated by runoff such as in the Organ Mountains. Little leaf sumac and large leaf sumac both occurred
throughout the study area. It appears that it could be
capable of growing in other positions. Sumac are also important browse plants. Like mahogany, they are senescent but
lose their leaves slowly. Because of the features of the latter
three species, their identification as true obligate riparian
species is questionable.
Half-shrubs and cacti
Foothill riparian species
Brickellia brachyphylla
Brickellia laciniata**
Cercocarpus montanus var. glaber
Condalia ericoides *
Garrya ovata subsp. goldmanii
Rhus trilobata x microphylla
Celtis laevigata var. reticulata**
None
Foothill upper watershed species
Brickellia petrophila
Fouquieria splendens *
Isocoma wrightii
Mimosa borealis
Yucca torreyi *
Coryphantha strobiliformis
Coryphantha vivipara**
Echinocereus spp.
Echinocereus Lloydii
Choisya dumosa
Submesa riparian species
Brickellia laciniata**
Chilopsis linearis
Fallugia paradoxa *
Celtis laevigata var. reticulata**
Hymenoclea monogyra
Submesa upper watershed species
Baccharis pteronioides *
Ceanothus greggii
Chrysothamnus pulchellus *
Conda/ia ericoides *
Oasylirion spp. *
Coldenia greggii
Coryphantha macromeris
Coryphantha vivipara**
Mammillaria lasiacantha
*Lost as an obligate species when analyses combines foothill and submesa
arroyo types.
"'Also occurs in submesalfoothill arroyos.
locations. David's mint was well represented on the foothill
main channel. However, its occurrence in the submesa type
was infrequent, and it probably occupies a mesic microsite.
Shifting of obligate species probably occurs as elevation
descends to other type locations. For example, neither little
leaf sumac or large leaf sumac (Rhus trilobata) were identified as obligate riparian or obligate upper watershed species.
(One exception occurred where a peculiar specimen thought
to be a hybrid of the two shrubs occupied the main channel.)
Both the foothill and submesa types are mesic enough
throughout the watershed to support these shrubs in most
positions. However, this might change if the arroyos positioned at lower elevations in the desert floor of the Tularosa
Basin were examined. Both sumacs probably occur as obligate riparian species on the desert floor.
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Browning, John M. 1989. Classification of Riparian Plant Communities in New Mexico. Unpublished Master's Thesis. New Mexico
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Obligate species were identified in a separate analyses
that combined all four arroyos. The procedure follows that
described above. A few species that were obligate in separate
submesa and foothill analyses were no longer obligate when
all four arroyos were combined (table 4).
235
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236