Download Factors Influencing Infiltration and Sediment Productionof Semiarid

WATER RESOURCES RESEARCH
VOL. II, NO.6
DECEMBER 1975
Factors Influencing Infiltration and Sediment Production of
Semiarid Rangelands in Nevada
W. H.
BLACKBURN
Range Science Department. Texas A & M University. College Station. Texas
77843
Simulated rainfall was used to study infiltration rates and sediment production of28 plant communities
and soils of five watershed areas in central and eastern Nevada. Two antecedent moisture conditions were
used: soil initially air dry and initially at field capacity. InfiltratIOn rates and sediment production of the
various soils are largely controlled by extent and surface morphology of dune interspace soils. Vesicular
horizons are unstable in dune interspace surface soils. These horizons seldom occur in coppice dunes or in
well-aggregated dune interspace soils. Infiltration rate is negatively related, and sediment production
positively related to the occurrence and morphology of vesicular horizons. More sediment is produced
from soils with antecedent moisture initially at field capacity than from'initially dry soil because of the
instability of vesicular horizons when the soils were saturated.
High-intensity summer thunderstorms in the Great Basin
account for most of the runoff and sediment production from
rangelands. Runoff is the major force initiating soil movement
and transporting sediment. In order to manage rangeland
watersheds effectively, factors influencing infiltration and
sediment production need to be understood.
Infiltration and erosion on rangelands have been studied for
some time. Review of the literature includes Chapline [1929],
Forsling [1932], U.S. Department of Agriculture [1940],
Harper [1953], Gifford [1968], and Branson et al. [1972].
However, for Nevada rangeland there is practically no informatIOn on infiltration and sediment production or on the influence of dune interspace areas and associated vesicular horizons on infiltration and sediment production. The objective of
this study was to determine which ground cover and soil parameters most influence infiltration and sediment production.
METHODS
Twenty-eight study sites were selected within five watersheds
(Table I). Nine sites were located in the Duckwater Watershed, six sites in the Coils Creek Watershed, six sites in the
Steptoe Watershed, and seven sites in the Pine and Mathews
Canyon Watersheds. The watersheds were sampled at the following times: Duckwater and Steptoe, June I-July 15; Coils
Creek and Pine and Mathews Canyon, July 16-September I.
Study sites were selected for their accessibility, repetition
over large areas in the Great Basin, and vegetation and soil
properties. Each site was located on a typical area with a
different plant community and/or soil. Coppice dune is the
area of accum ulation of litter and soil under shrubs and bunch
grasses.
The infiltrometer and methods of application are described
by Blackburn et al. [1974].
In the Great Basin, summer thunderstorms usually occur
on dry soil, although some occur on soil that is at or near field
capacity. An application rate of 3 in./h for a duration of onehalf hour was applied to two antecedent moisture conditions,
soil surface horizon initially air dry and soil surface horizon
initially at field capacity. Basically, infiltration was defined for
any point in time as the difference between total water applied
and total runoff. Two types of runoff plots were used, i.e., 3 X
3 ft and variable. Regular plots were situated so the same mean
Copyright © 1975 by the American Geophysical Union.
percent coppice dune that occurred on the site also occurred in
the plot. Variable plots were located to contain approximately
100% dune interspace area or coppice dune area. Variable
plots were used only on sites that had obvious dune interspace
and coppice differences. Each treatment was replicated 6 or 8
times.
Sediment production was determined from a 30-fluid-oz
runoff sample and other sediment trapped in the collection
apparatus. Suspended sediment was allowed to settle in the
laboratory and the water drained off. Samples were ovendried, weighed, and converted to sediment in pounds per acre.
Plant cover and composition, litter, rock (1-2 in. and >2 in.
in largest dimension), and bare ground on each plot were
measured with a point frame [Levy and Madden. 1933].
Coppice dunes w~thin the plots were measured in two directions, and the ellipse formula used to compute cover. Dune interspace areas were computed as the complement of coppice
dune.
A soil profile description was made at each study site according to the procedures outlined by U.S. Department of
Agriculture [1951, 1960]. Family-level identifications were
made in accordance with the Soil Conservation Service [U.S.
Department of Agriculture. 1960, 1970]. The surface horizon
(from the surface to some diagnostic subsurface horizon) was
rated from I to 5 on the basis of structure and vesicular pores
(Table 2). Likewise, each soil was classified as to hydrologic
group [U.S. Department of Agriculture. 1964].
Bulk density and initial soil moisture content were determined by using the Troxler surface moisture-density gage.
Bulk density was determined for surface 2-, 4-, and 6-in.
depths of dune interspace areas and coppice dunes. Soil
moisture before the dry infiltration test was taken concurrent
with bulk density readings. To prevent plot disturbance, these
readings were taken on areas adjacent to plots. In order to obtain soil moisture before the wet run an additional plot was
sprinkled, covered with polyethylene plastic, and left for 24
hours before the moisture reading was taken. Particle size distribution of soil from each horizon, including surface dune interspace areas and coppice dunes, was measured by the
hydrometer method [Bouyoucos. 1962]. Organic carbon content of soil from each horizon including surface dune interspace areas and coppice dunes was determined by a hightemperature induction furnace [Black. 1965].
Each study site was classified as to its physiographic place-
929
\C)
.....
o
TABLE I.
Location
Elevation
30 airline mi south and
east of Eureka, mostly in
White Pine County,
Nevada. Site, 100 mi'
[Blackburn et al., 1968].
Highest peak is around
7300 ft and the basin outlet is 4800 ft.
Description of Study Sites
Climate
Geology and Soils
Dominant Vegetation
Duckwater Watershed
Annual precipitation 7.8-13.7 in.,
mostly as snow. Temperature at the lower
elevations ranges from a low of - 34 ° F
to a high of99°F, with a mean annual
temperature of 43° F.
Volcanics and sedimentaries, i.e., tuff,
basalt, andesites and limestone. Aridisols
and Entisols, i.e., Torrifluvents,
Durorthids, Haplargids, Durargids,
and Natragids.
Black sagebrush· (A rtemisia nova), big sagebrush
(Artemisia triden/ata), shadscale (Atriplex conferti/olia), winter fat (Eurotia lanata), green
rabbit brush (Chrysothamnus viscidiflorus),
Utah juniper (Juniperus osteosperma), single
leaf pinyon (Pinus monophylla).
t:I:l
,....
;l>
(l
:>:
til
c:
;>;
"
Coils Creek Watershed
32 airline mi northwest
Highest peak is around
of Eureka in Eureka
8400 ft and the basin outCounty, Nevada. Site, 48 let is 6500 ft.
mi' [Blackburn et ai,
1969a].
24 airline mi southeast
of Ely in White Pine
County, Nevada. Site, 45
mi' [Heinze et al.,
1966].
Highest peak is around
9081 ft and the basin
outlet is 7100 ft.
Annual precipitation 8.8-14.8 in.,
mostly as snow. Temperature ranges
from a low of - 26° F to a high of
110°F, with a mean annual temperature
of47°F.
Volcanics and sedimentaTles, i.e.,
basalt, shale, sandstone and limestone.
Entisols and Aridisols or Mollisols, i.e.,
Torriorthents, Camborthids,
Haplustolls, Haploxerolls, Durixerolls,
and Argixerolls.
Steptoe Watershed
Annual precipitation is 12 in., mostly as
Limestone. Aridisols or Mollisols, i.e.,
snow. Temperature ranges from a low of Camborthids, Haplargids, Durargids,
-26°F to a high of9r F, with a mean
and Argixerolls.
annual temperature of44°F.
Low sagebrush (A rtemisia arbuscula), big
sagebrush, snow berry (Symphoricarpos
longiflorus), Utah juniper, single leaf pinyon,
Sandberg bluegrass (Poa secunda), bluebunch
wheatgrass (Agropyron spicatum), woolly
wyethia (Wyethia mol/is), squirreltail (Sitanion
hys/rix), arrowleafbalsamroot (Balsamorhiza
sagil/a/a), diffused phlox (Phlox dijJusa).
Highest peak is around
6700 ft and the basin
outlets are approximately
5600 ft.
Annual precipitation 11.9-21.8 in.,
mostly as snow during winter or rain in
late summer. Temperature of the basins
ranges from a low of OaF to a high of
101 0 F, with a mean annual temperature
of50°F.
Volcanics and old lake bed sediments,
i.e., andesite, tuff, ignibrite, tuffaceous
clay, sand, and silt. Aridisols of
Mollisols with a few Entisols, i.e.,
Torriorthents, Durargids, Haplargids,
Argixerolls, and Haploxerolls.
-i
"-i
;l>
oZ
;l>
Z
"
'"
"3:
en
'"-iZ
Big sagebrush, bitter brush (Purshia /riden/ata),
Utah juniper, single leaf pinyon, bluebunch
wheatgrass, crested wheatgrass (Agropyron
desertorum).
Pine and Mathews Canyon Watersheds
18 airline mi southeast
of Caliente in Lincoln
County, Nevada. Site,
66 mi' [Blackburn et al.,
1969b].
Z
:!l
,....
Big sagebrush, black sagebrush, rubber rabbitbrush
(Chrysothamnus nauseosus), serviceberry
(Amelanchier alni/olia), Utah juniper, single
leaf pinyon, intermediate wheatgrass
(Agropyron intermedium), squirreltail.
'"1:1
"o
"
c:
~
oz
931
BLACKBURN: INFILTRATION AND SEDIMENT PRODUCTION
TABLE 2.
Rating
Soil Surface Horizon Morphological Rating
ment, i.e., mountain, smooth or dissected alluvial fan, or
floodplain. Percent slope was obtained from an Abney level,
and aspect from an 8-point compass. Surface roughness of
each plot was determined with a microrelief meter as described by Kincaid and Williams [1966].
Soil Surface Horizon Morphological Description
Single-grain sandy texture or well-aggregated granular
structure without vesicular pores·
Granular or massive structure having few vesicular po rest
Massive or weak platy structure having common vesicular
pores
Moderate platy structure having common vesicular pores,
or massive structure having many vesicular pores, or
clayey and weakly structured
Strong platy structure baving many vesicular pores, or
clayey and massive
2
3
4
5
RESULTS AND DISCUSSION
Infiltration
The following discussion is based on regression equations
(Table 3) where the dependent variables are average infiltration rates by treatment at the end of 30 min. Dependent and
independent variables and the mean and standard deviation of
the variables appearing in the regression equations are given in
Table 4.
Duckwater Watershed. The regression equations for
this watershed are (I) and (2) in Table 3. Weighted percent silt
is the most important variable explaining variation in infiltration. Plant cover and dune interspace areas are least important, the other variables being intermediate in their importance.
·Structures are defined as being granular (approximately spherical
with no accommodation of faces to surrounding peds), platy (with
vertical dimension small with regard to horizontal dimensions and
faces accommodated with those of adjacent peds), or massive (no
aggregation ).
tIn classes of pore abundance the number of units per area of
surface was 1-3 for few pores, 4-14 for common pores, and more
than 14 for many pores. A unit is defined as a square inch for
fine, very fine, and micropores and as a square yard for medium and
coarse pores.
TABLE 3.
Equation
Number
Infiltration and Sediment Multiple-Regression Equations by Watershed and Treatment
Watershed
Antecedent
Moisture
Regression Equation
Coefficient of
Determination
R2
I nfl/lration
Duckwater
dry
Yl
2
Duckwater
field capacity
Y2
3
Coils Creek
dry
YI
4
Coils Creek
field capacity
Y2
5
Steptoe
dry
Y1
6
Steptoe
field capacity
Y2
7
Pine and Mathews Canyons
dry
Yl
8
Pine and Mathews Canyons
field capacity
Y2
9
Duckwater, Coils Creek,
Steptoe, Pine and Mathews
Canyons
Duckwater, Coils Creek,
Steptoe, Pine and Mathews
Canyons
dry
YI
field capacity
Y2
10
0.00470(X9) + 0.00738(XI3)
-0.128(XI8) - 0.033(X27) + O.l23(X36)
= 2.865 - 0.00994(X9) - 0.OO213(XI0)
+ 0.OO258(XI3) - 0.147(XI8) - 0.0341(X27)
+ 0.118(X36)
= 3.243 - 0.OOI21(X9) - 0.00835(XIO)
-0.144(XI8) - 0.OO304(X27)
= 3.386 - 0.OO230(X9) - 0.0144(XIO)
-0.170(XI8) - 0.OO913(X27)
= 1.948 + 0.951(X4) - 0.00367(XI0)
-0.116(XI8)
= -0.542 + 2.42(X4) - 0.011(X9) - 8.107(XIO)
- 0.251(XI8) + 0.192(X36)
= 3.987 - 0.00404(X9) - 0.OOI69(XI0)
+ 0.OO392(XI2) + 0.219(XI5) - 0.0457(X25)
= 2.863 - 0.0255(X7) - 0.OO582(X9)
- 0.00822(XIO) + 0.00390(XI3)
= 3.121 - 0.00593(XIO) - 0.163(XI8)
+ 0.175(X20) - 0.OO931(X30)
0.723
= 3.074 - 0.0119(XIO) - 0.176(XI8)
+ 0.184(X20) - 0.00958(X30)
0.630
= 2.808 -
0.748
0.719
0.812
0.310
0.605
0.661
0.799
0.505
Sediment
= 3.096 +
2.829(X4) + 1.274(X9)
- 0.413(XI8) - 2.109(X24) + 3.555(X27)
Y4 = 6.715 - 0.402(XI8) + 3.473(X27)
II
Duckwater
dry
12
Duckwater
field capacity
13
Coils Creek
dry
Y3
= 16.827 - 2.094(X4) + 0.000409(X9)
+ 0.OO75(XIO) - 0.37(X21) - 0.0874(X24)
14
Coils Creek
field capacity
Y4
= 9.415 -
15
Steptoe
dry
Y3
16
Steptoe
field capacity
Y4
17
Pine and Mathews Canyons
dry
Y3
18
Pine and Mathews Canyons
field capacity
Y4
Y3
- O.l35(X27)
1.266(X4) + 0.00783(XIO)
- 0.398(X21 ) - 0.020(X24)
= 6.222 - 1.636(XI0) - 1.012(XI2)
- 0.853(X21) + 0.074(X27)
= 4.535 - 2.954(X4) - 5.918(XI0)
- 2.519(XI2) - 1.214(X21) + 0.IOI(X24),
= 17.143 - 1.278(X4) - 0.506(XI8)
- 1.00(X21) - 0.100(X24) - 8.895(X27)
= 10.577 - 1.I09(X4) - 0.0098(X9)
+ 0.0042(XI0) - 0.537(XI8) - 0.064(X24)
+ 0.0489(X27)
0.258
0.256
0.267
0.376
0.203
0.416
0.235
0.241
BLACKBURN: INFILTRATION AND SEDIMENT PRODUCTION
932
TABLE 4. Mean Standard DeviatIOn and Units of Measure of the Independent Variables (X) and
Units of Measure on the Dependent Variables (Y) Appearing in Regression Equations by Watershed
Number
X4
X9
XIO
XI3
XI8
X24
X27
X36
X4
X9
XIO
XI8
X21
X24
X27
X4
X9
XIO
XI2
XI8
X21
X24
X27
X36
X4
X7
X9
XIO
XI2
XI3
XI5
XIS
X21
X24
X25
X27
XIO
XI8
X20
X30
Variable
Mean
Duckwater Watershed
soil bulk density in surface 0-4 in., dune
1.42
interspace
bare ground
32.82
dune interspace
62.63
plant cover
23.25
soil surface horizon morphological
3.04
rating, weIghted
sand fraction of soil surface horizon,
56.54
weighted
23.95
silt fraction in soil surface horizon,
weighted
4.21
depth of surface horizon, weighted
Coils Creek Watershed
soil bulk density in surface 0-4 in.,
1.35
dune interspace
22.41
bare ground
65.93
dune interspace
1.38
soil surface horizon morphological
rating, weighted
1.57
carbon, weighted
6.28
sand fraction in soil surface horizon,
weighted
27.14
silt fraction in soil surface horizon,
weighted
Steptoe Watershed
soil bulk density in surface 0-4 in.,
1.29
dune interspace
22.41
bare ground
65.93
dune interspace
53.99
litter
soil surface horizon morphological
1.38
rating, weighted
2.06
carbon, weighted
sand fraction in soil surface horizon,
51.20
weighted
silt fraction in soil surface horizon,
32.86
weighted
4.58
depth of surface horizon, weighted
Pine and Mathews Canyon Watersheds
1.57
soIl bulk density in surface 0-4 in.,
dune interspace
10.30
rock 0-2 in.)
37.01
bare ground
dune interspace
60.57
43.28
litter
plant cover
31.78
roughness factor
0.42
soil surface horizon morphological
2.09
rating, weigh ted
0.92
carbon, weighted
3S.33
sand fraction in soil surface horizon,
weighted
silt fraction in soil surface horizon,
33.95
coppice dune
silt fraction in soil surface horizon,
38.39
weighted
Watersheds Combined
60.41
dune interspace
2.56
soil surface horizon morphological
rating, weighted
US
carbon, dune interspace
21.74
clay fraction in soil surface horizon,
weighted
Standard
DeviatIOn
0.08
Unit of
Measure
Ib/ft'
19.45
33.02
22.06
1.25
percent
percent
percent
1-5
15.81
percent
9.01
percent
1.49
in.
0.15
Ib/ft'
13.67
26.17
0.65
percent
percent
1-5
0.51
3.94
percent
percent
8.12
percent
0.24
Ib/ft'
13.67
26.17
24.25
0.65
percent
percent
percent
1-5
0.64
8.61
percent
percent
8.59
percent
1.03
in.
0.39
Ib/ft'
4.63
27.20
38.11
38.35
24.96
0.27
1.16
percent
percent
percent
percent
percent
in.'
1-5
0.44
S.36
percent
percent
4.61
percent
5.52
percent
34.91
2.64
percent
1-5
2.27
8.67
percent
percent
All Watersheds
YI
mean infiltration rate after 30 min,
soil surface initially dry
in./h
933
BLACKBURN: INFILTRATION AND SEDIMENT PRODUCTION
TABLE 4.
Number
Y2
Y3
Y4
(continued)
Variable
mean infiltration rate after 30 min, soil
surface initially at field capacity
log total sediment production, soil
surface initially dry
log total sediment production, soil
surface initially at field capacity
Coils Creek Watershed. Bare ground, dune interspace,
weighted soil surface horizon morphological rating, and
weighted percent silt of the surface horizon are the important
variables in (2) and (3) (Table 3). Dune interspace, however, is
the most important variable. Weighted soil surface horizon
morphological rating and percent silt of the surface horizon
are intermediate in importance, and bare ground is the least
important variable.
Steptoe Watershed. In (5) and (6) (Table 3), bulk density, bare ground, dune interspace, weighted soil surface horizon morphological rating, and weighted depth of soil surface horizon are the important variables. Dune interspace and
weighted soil surface horizon morphological rating are the
most important variables in determining infiltration.
Pine and Mathews Canyon Watersheds. Pavement, bare
ground, dune interspace, litter, plant cover, roughness factor,
and silt of the coppice dune differ in importance with the
various treatments. In (7) (Table 3), silt of the surface horizon,
coppice dune, and litter are the most important. In (9), dune
interspace and pavement become the most important in determining infiltration.
Combined analysis. Data from the five watersheds were
combined in order to develop some uniform equations that
might be more generally applied (Table 3).
In both equations, weighted soil surface horizon morphological rating is the most important variable in determining infiltration; dune interspace, percent organic carbon,
and dune interspace are intermediate in importance, weighted
clay fraction in the soil surface horizon being least important.
Many plant communities in the Great Basin are characterized by a shrub overstory and very sparse vegetation
between shrubs. According to Duley and Kelly [1939], infiltration rates of a site should be the same or very similar for
different rainfall intensities as long as the terminal infiltration
is exceeded. To demonstrate this, simulated rainfall was applied to dune interspace areas of the winter fat community at a
rate of 3, Ii, 0.97, 0.57, 0.44, and 0.22 in./h. It was not until
rainfall intensities of 0.57, 0.44, and 0.22 for air-dry soil and
0.22 for soil initially at field capacity occurred that infiltration
rates dropped below a fairly constant terminal rate. This was
not the case when coppice dunes and dune interspace areas
were included in the study plots. Infiltration rate for the 3-in./h
simulated rainfall was almost twice that of the li-in./h rainfall.
On variable plots coppice dunes displayed an exceedingly
high infiltration rate, i.e., sometimes 3-4 times greater than the
dune interspace areas and near or exceeding the application rate. Dune interspace areas exhibit a relative low infiltration rate (Figure 1). This relationship held true over a wide
variety of soils, except for a few Utah juniper coppice dunes
where hydrophobic soils were encountered.
Infiltration rates for shrub or grass (big sagebrush/crested
Unit of
Measure
Standard
Deviation
Mean
All Watersheds
(continued)
in./h
Ib/acre
Ib/acre
wheatgrass only) coppice dunes are significantly higher than
those for corresponding dune interspace areas. Highest infiltration rates are in big sagebrush/crested wheatgrass and
low sagebrush Sandberg bluegrass/squirreltail coppice dunes,
and lowest rates occur in big sagebrush and low
sagebrush/Sandberg bluegrass/squirreltail dune interspace
areas. The only grass coppice dune sampled (big
sagebrush/crested wheatgrass) had a significantly higher infiltration rate than its untreated big sagebrush coppice dune
counterpart (big sagebrush/rubber rabbitbrush) (Table 5).
Rate at which water will enter a soil landscape is governed
mainly by the extent and soil surface horizon morphology of
the dune interspace areas (Figure 2). The big sagebrush community, Duckwater Watershed, is used to demonstrate this soil
difference (Table 6). Dune interspace areas have a shallower
surface horizon, a lower percent carbon, a higher pH, a higher
bulk density, and a higher percent silt than the coppice dunes.
Soil structure in dune interspace areas is moderate to fine platy
as compared to weak fine granular in the coppice dunes. Dune
interspace areas also have larger and many more vesicular
pores in their surface horizon than the coppice dunes. These
conditions account for more than 3 times higher infiltration
rates on coppice dunes.
This relationship is further attested by personal observation
after a high-intensity thunderstorm at Duckwater Watershed,
July 22, 1970. This storm had an average intensity for the basin
of 1.2 in./h, mostly as hail and rain. However, intensities
within the watershed exceeded 4 in./h for short periods (John
Trimmer, personal communication from records of Bureau of
Land Management, Nevada State Office, Reno, Nevada,
\970). Runoff was large, causing major downstream damage
to the Duckwater Indian Reservation and to the watershed.
After the storm, moisture had penetrated more than 8 in. in
the coppice dunes and only 2 in. in dune interspace soil.
Vesicular horizon. Infiltration rates are negatively related
to vesicular horizons (Figure 3), and the strength of this
....
-....
...
.5
~ .... • .... - ....... • .. - - .. - - · - - - - - - . - - - - - ... - - ... _1.7
,.:
,.,.." ....
2
]co
~
~
..._,.,:....
.., ................., .............., ' ,
1
..!
-
5011 lur'.ca InltloUy .t "oW
c.~.dty
...... - .... 5011 turfoco Inltlolty II,,.
O~----~----~~----~----~~----~----~
o
10
15
::10
:u
30
Time (min)
FIg.
I.
Infiltration curves for the big sagebrush community,
Duckwater Watershed.
934
BLACKBURN: INFILTRATION AND SEDIMENT PRODUCTION
TABLE 5.
Mean Infiltration Rate (Inches per Hour) and Sediment Production (Pounds per Acre) for Coppice Dune and Dune Interspace
Areas of Six Plant Communities in Three Watersheds
Sediment Production
Infiltration Rate
Dry
Plant Comm unity and
Watershed·
Coppice
Big sagebrush/crested wheatgrass (M)
Big sagebrush/Sandberg
bluegrass/diffused phlox (C)
Big sagebrush (D)
Big sagebrush/bluebunch
wheatgrass/arrowleaf
balsam root (C)
Low sagebrush/Sandberg
bluegrass/squirreltail (C)
Big sagebrush/rubber
rabbitbrush (M)
Field Capacity
Interspace
Coppice
Interspace
Dry
Coppice
Field Capacity
Interspace
Coppice
Interspace
2.890
1.79bc
2.720
1.16cd
3000
5200
1200b
4800
2.870
1.56c
2.710b
0.84cd
10
4600
60b
6200
2.870
2.820
1.03
1.99b
2.600b
2.780
0.82cd
1.26bc
IOOob
20
200ab
3400
2200b
60b
3200b
6400
2.800
1.54c
2.840
0.65d
40b
3000
60b
6400
2.54
1.78bc
2.29b
0.71d
3600
3200
320ab
300ab
Means followed by the same letter are not significantly different (0.05) as determined by Duncan's multiple-range test. All comparisons
are made within the two columns under each antecedent moisture condition (dry or field capacity).
* The letters C, D, and M represent, respectively, Coils Creek, Duckwater, and Mathews Canyon.
relationship is dependent on vesicular horizon morphology.
Sudicial vesicular horizons develop in arid and semiarid
areas of sparse vegetation cover. Yolk and Geyger [1970]
observed in many warm-arid areas of the earth that there are
patches free of vegetation distributed in a mosaiclike pattern,
although the precipitation is sufficient for plant growth. These
'scalded areas' are not necessarily caused by overgrazing or
soil salinity. They made extensive observations in southern
Spain, Morocco, and southwest Africa and found near the
soil surface a structure formation that they designated as
'foam structure' (vesicular porosity).
Miller [1971] studied vesicular pore formation under furrow
irrigation in Washington and speculated that a platy structure
develops first. Then, with continued wetting and drying, the
pores between platelets became spherical and the spheres
Fig. 2.
became larger. He also noted that all of the soil exhibited considerable swelling and shrinking with wetting and drying. The
bulk density of the surface decreased with a number of wetting
cycles. Miller concluded that soils involved in vesicular pore
formation are very unstable when they are nearly saturated
and the air pressure is sufficient to form the cavity between
platelets into a sphere, thus achieving the smallest surface area
per unit volume. More air is entrapped in the soil with each
wetting and drying cycle. Then in wet, fluid soil, small vesicles
merge into larger ones because the surface area per unit
volume decreases as they enlarge. Vesicles remain air-filled
during water application. This horizon develops in surface 2 or
3 in. of the soil. Soils involved in vesicular development are
classified as Aridisols, Torrifluvents or Torriorthents. They
have low organic matter and high percent silt-sized particles.
Soil profile showing coppice dune and dune interspace soil surface horizon.
BLACKBURN: INFILTRATION AND SEDIMENT PRODUCTION
TABLE 6. Soil Surface Horizon Parameters and Infiltration Rates
for Coppice Dune and Dune Interspace Areas of the Big Sagebrush
Community, Duckwater Watershed
Parameter
Dune Interspace
2
Depth, in.
Carbon, %
0.5
pH
7.7
Bulk density, Ib/ftS
Silt, %
Structure
Pores
0.12
26
Infiltration rate, in./h
medium fine platy
. many very fine and
fine vesicular
0.74
Coppice Dune
5
1.0
7.4
0.10
18
weak fine granular
few fine vesicular
and interstitial
2.54
These vesicular horizons are poorly aggregated and very unstable when they are nearly saturated.
Organic matter. Organic matter in the soil is the major
cause of aggregation. It not only binds soil particles into aggregates but lightens and expands the soil, thus increasing the
porosity and decreasing vesicular horizon formation. Infiltration is positively related to organic matter except for a few
juniper coppice dunes where hydrophobic soils occur.
Bulk density. Coppice dunes consistently have a lower
bulk density than dune interspace soils. However, dune interspace soils with vesicular porosity exhibit a lower bulk density
than dune interspace soils without vesicular porosity. Infiltration rates of soils without vesicular horizons decrease as bulk
density increases. On soils with a vesicular horizon, infiltration
rates decrease as bulk density decreases.
Texture. Silt and clay-sized particles are negatively correlated with infiltration rates. Sand-sized particles are
positively related to infiltration. Generally, the coarser the surface texture, the higher the infiltration rate. Of the three particle sizes, percent silt of the soil surface horizon has the
strongest influence on infiltration because of vesicular horizon
formation in: soils high in silt.
Surface horizon depth. Thick surface horizons are found in
highly productive soils and in coppice dunes; i.e., coppice
Fig. 3.
935
dunes are 1-4 in. thicker than interspace soils. Infiltration rates
increase as the surface horizon increases in thickness.
Moisture. Infiltration rate was lower on soils that were
initially at field capacity than on those that were initially dry.
The higher the initial moisture content, the more micropores
that are filled and the lower the infiltration rate. Infiltration
rates are usually negatively related to antecedent moisture content.
Plant and litter cover. Plant and litter cover are both
positively correlated with infiltration; however, their influence
is not as strong as has been shown in other studies [Dortignac
and Love, 1966; Rauzi et al., 1968; M eeuwig, 1970]. In this
study, vesicular horizon and dune interspace areas were more
important in explaining infiltration than plant and litter cover
probably because of the sparse cover of vegetation in the interspace areas and the kind of soils.
Rock. Study sites were characterized by a very low cover
of large rocks (>2 in. in largest diameter); thus rock showed a
poor correlation with infiltration. However, as small rocks (1-2
in. in largest diameter) increased on the sites, infiltration rates
decreased. This latter relationship is explained by the large
percent of small rocks associated on the surface of soils with
vesicular horizons.
Bare ground. Infiltration rates were strongly negatively correlated with bare ground. This is consistent with findings of
Duley and Domingo [1949], Branson and Owen [1970], and
many others.
Slope. Percent slope shows a positive correlation with infiltration rates and indicates that as slope increases, so does infiltration rate. Actually in this study, slope had very little influence on infiltration rates. Most study sites were
characterized by very gentle slopes except in the mountains
where sites on steeper slopes have high infiltration rates. The
correlation, then, is due to different soils and not to slope.
Surface roughness. Surface roughness shows a weak
positive correlation with infiltration and indicates that an irregular surface may increase infiltration rates slightly. This
poor correlation is probably due to the fairly level relief of the
study area.
Vesicular horizon showing platy structure and vesicular porosity; scale division is 0.04 in.
936
BLACKBURN:
I NFILTRATION
Sediment Production
The following discussion is based on multiple regression
equations (Table 3) where the dependent variables are common logarithms of sediment production at the end of 30 min.
The mean and standard deviation of the independent variables
in the regression equations are given in Table 4. Equations
developed from data where the soils were initially at field
capacity usually had the lowest standard error of estimate and
the highest R2 values.
Runoff, as the only independent variable, is highly correlated with sediment production. However, when runoff was
included in the multiple-regression equations, it failed to improve the standard error of estimates or R2 values. The reason
for this relationship is that the same factors often influence infiltration and sediment production. Thus runoff does not appear in regression equations.
Duckwater Watershed. Bulk density, bare ground, soil surface horizon morphological rating, weighted sand, and
weighted silt fraction of the surface horizon are the important
variables explaining the variation in sediment production in
(II) and (12) (Table 3). Soil surface horizon morphological
rating is the most important variable explaining sediment
production, and weighted silt fraction the least important.
Coils Creek Watershed. Bulk density, bare ground, dune
interspace, weighted organic carbon, weighted sand, and
weighted silt fraction of the soil surface horizon are the important variables (Table 3). Dune interspace is the most important
variable in determining sediment production, and weighted
sand fraction the least important.
Steptoe Watershed. Bulk density, dune interspace, litter,
weighted organic carbon, weighted sand, and weighted silt
fraction of the surface horizon are the most important
variables in (15) and (16) (Table 3). Weighted organic carbon
and weighted silt fraction in surface horizon are the most important variables explaining the variation in sediment production, and dune interspace and litter the least important.
Pine and Mathews Canyon Watersheds. Bulk density, bare
ground, dune interspace, soil surface horizon morphological
rating, weighted sand, and weighted silt fraction of the surface
horizon are the important variables for these watersheds. Bulk
density and soil surface horizon morphological rating are the
most important variables explaining sediment production, and
dune interspace and weighted silt fraction of the surface
horizon the least important.
Combined analysis. Because of the high standard error of
estimates and low R2 values for the combined data analyses the
equations are not presented.
Sediment is usually considerably higher from dune interspace areas than from coppice dunes. This relationship held
true except for the big sagebrush/rubber rabbitbrush community. Sediment produced from dune interspace areas of the
three communities sampled at. Coils Creek Watershed is
significantly higher than it is from corresponding coppice
dunes (Table 5). Variations in sediment production from coppice dunes and dune interspace areas range from none to as
much as 46 times more sediment from big sagebrush/Sandberg
bluegrass/diffused phlox community dune interspace areas
than from their corresponding coppice dunes. As dune interspace areas increase, sediment production increases. Similar
relationships also are observed for percent bare ground and
percen t sil t.
Significantly more sediment is produced from soils initially
at field capacity than from those initially dry because of the in-
AND SEDIMENT PRODUCTION
stability of the surface horizon when it is saturated. The soil
surface reaches saturation quicker on the wet test; thus there is
a longer time to erode the dispersed soil particl.es. In this way,
initial moisture content shows a positive correfation with sediment. This relationship is most marked for soils with a
vesicular surface horizon.
As organic matter, sand-sized particles, coppice dunes, and
litter increase on the study sites, sediment production
decreases. Plant cover was poorly correlated with sediment
production and does not appear in regression equations.
Roughness factor is slightly negatively correlated with sediment production. As bulk density ofthe surface 4 in. increases,
sediment production usually increases except on sites with
vesicular horizons where bulk density is negatively related to
sediment production.
The large variation in sediment production can be explained
by the gentle slopes which allow detached and suspended soil
particles to settle out in the small depressions before they reach
the collection trough and the location of coppice dunes and
dune interspace areas. Coppice dunes have a lower rate of sediment production than dune interspace areas. Thus the amount
of coppice dune in the plot, if not constant, would influence
sediment production. Likewise, suspended sediment was seen
to settle out along the coppice dune edge. This effect was
magnified the closer the coppice dune was to the collection
trough.
Acknowledgment. This study was a cooperative project between
the Burea.u of Land Management and Nevada Agricultural Experiment Station, Journal Series 268. The financial support of the bureau
is acknowledged.
REFERENCES
Black, C. A. (Ed.), Methods of Soil Analysis, Amer. Soc. Agron. Ser.
9, 1572 pp., American Society of Agronomy, Madison, Wis.,
1965.
Blackburn, W. H., P. T. Tueller, and R. E. Eckert, Jr., Vegetation
and soils of the Duckwater Watershed, Rep. R-40, 80 pp., Coli. of
Agr., Univ. of Nev., Reno, 1968.
Blackburn, W. H., R. E. Eckert, Jr., and P. T. Tueller, Vegetation
and soils of the Coils Creek Watershed, Rep. R-48, 80 pp., Coli.
of Agr., Univ. of Nev., Reno 1969a.
Blackburn, W. H., P. T. Tueller, and R. E. Eckert, Jr., Vegetation
and soils of the Pine and Mathews Canyon Watersheds, Rep. 46,
109 pp., Coli. of Agr., Univ. of Nev., Reno, 1969b.
Blackburn, W. H., R. O. Meeuwig, and C. M. Skau, A mobile infiltrometer for use on rangelands, J. Range Manage., 27,
322-323, 1974.
Bouyoucos, G. J., Hydrometer method improved for making particle size analysis of soil, Agron. J., 54,464-465, 1962.
Branson, F. A., and J. B. Owen, Plant cover, runoff, and sedimet
yield relationships on Mancos Shale in western Colorado, Water
Resour. Res., 6,783-790, 1970.
Branson, F. A., G. F. Gifford, and .J. R. Owen, Rangeland hydrology, Range Sci. Ser. 1, 84 pp., Soc. for Range Manage.,
Denver, Colo., 1972.
Chapline, W. R., Erosion on rangelands, A mer. Soc. Agr. J., 21,
423-429, 1929.
Dortignac, E. J., and L. D. Love, Infiltration studies on ponderosa
pine ranges of Colorado, U.S. Forest Servo Rocky Mt. Forest
Range Exp. Sta. Pap. 59, 1-34, 1961.
Duley, F. L., and C. E. Domingo, Effect of grass on intake of water,
Neb. Agr. Exp. Sta. Res. Bull., 159, 1-15, 1949.
Duley, F. L., and L. L. Kelley, Effect of soil type, slope and surface
conditions on intake of water, Neb. Agr. Exp. Sta. Res. Bull., 112,
1-16,1939.
Forsling, C. L., Erosion on uncultivated lands in the intermountain region, Sci. Monogr., 34,311-321, 1932.
Giffo};d, G. F., Rangeland watershed management-A review,
Nev. Agr. Exp. Sta. Pap. R-52, I-50, 1968.
BLACKBURN'
I NFILTRATION
Harper, V.L., Watershed management-Forest and range aspects
in the United States, Unasylva, 3, 105-114, 1953.
Heinze, D. H., R. E. Eckert, Jr., and P. T. Tueller, The vegetation
and soils of the Steptoe Watershed, 40 pp., Coll. of Agr., Univ. of
Nev., Reno, 1966.
\
Kincaid, D. R., and G. Williams, Rainfall effects on soil surface
characteristics following range improvement treatments, J.
Range Manage., 19,346-351, 1966.
Levy, E. B., and E. A. Madden, The point method of pasture
analysis, N. Z. J. Agr., 46, 267-279, 1933.
Meeuwig, R. 0., Infiltration and soil erosion as influenced by
vegetation and soil in northern Utah, J. Range Manage., 23,
185-188, 1970.
Miller, D. E., Formation of vesicular structure in soil, Soil Sci. Soc.
Amer. Proc., 35,635-637, 1971.
Rauzi, F., C. L. Fly, and E. J. Dyksterhuis, Water intake on midcontinental rangelands as influenced by soil and plant cover,
U.S. Dep. Agr. Tech. Bull., 1390, 1-58, 1968.
U.S. Department of Agriculture, Influence of vegetation and
AND SEDIMENT PRODUCTION
937
watershed treatments on runoff, silting and stream flow, U.S.
Dep. Agr. Misc. Publ. 397, 1-80, 1940.
U.S. Department of Agriculture, Soil Survey Manual, Handb. 18,
503 pp., Washington, D. C., 1951.
U.S. Department of Agriculture, A Comprehensive System, The
Seventh Approximation, 265 pp., Washington, D. C., 1970.
U.S. Department of Agriculture, Hydrology, Part 1, Watershed
Planning, Washington, D. C., 1964.
U.S. Department of Agriculture, Soil Taxonomy of the National
Cooperatwe Satl Survey, 265 pp., Washington, D. C., 1960.
Volk, O. H., and E. Geyger, 'Schaumboden' als Ursache der
Vegetationslosigkeit in ariden Gebieten ('Foam' soils as the
cause of absence of vegetation in arid lands), Z. Geomorphol.,
14, 79-95, 1970.
(Received August 10, 1973;
revised June 24, 1975;
accepted July 23, 1975,)