Replacing Lehmann Lovegrass with
Native Grasses
S. H. Biedenbender
B. A. Roundy
L. Abbott
establishment of Lehmann lovegrass and seven seeded
native grasses to assess the potential of canopy manipulation for re-establishment of native grasses in existing
stands of Lehmann lovegrass.
The study was conducted on the Santa Rita Experimental Range in southeastern Arizona. The research plots
are located on an alluvial fan at an elevation of about
1075 m. The vegetation type is Chihuahuan desert shrub
dominated by an overstory of mesquite (Prosopis juliflora
var. velutina) and an understory of Lehmann lovegrass.
Lehmann lovegrass and seven native warm-season perennial grasses were seeded: cane beardgrass (Bothriochloa
barbinodis), sideoats grama (Bouteloua curtipendula), Arizona cottontop (Digitaria californica), plains lovegrass
(Eragrostis intermedia), green sprangletop (Leptochloa dubia), bush muhly (Muhlenbergia porteri), and plains
bristlegrass (Setaria leucopila and S. macrostachya).
These species are adapted to the environmental conditions on the Santa Rita Experimental Range and are
present as individuals in Lehmann lovegrass stands or in
areas which have not been seeded with or invaded by
Lehmann lovegrass.
Abstract—This study determined the effects of Lehmann lovegrass (Eragrostis lehmanniana) stand manipulations on establishment of Lehmann lovegrass and seven native grasses. Grasses
were sown in June and again in August into stands of Lehmann
lovegrass that had been left intact, burned, sprayed with herbicide and left standing, or sprayed and mowed. In 1992 the Junesown mow treatment and in 1993 the August-sown burn treatment produced the most native grass seedling establishment for
cane beardgrass (Bothriochloa barbinodis) and green sprangletop (Leptochloa dubia), respectively. Summer rainfall was most
frequent in July in 1992 and most frequent in August in 1993.
Lehmann lovegrass seedling density from sown seeds and from
the residual seedbank was highest for the burn treatment.
Lehmann lovegrass (Eragrostis lehmanniana) was introduced from Africa during the 1930’s to revegetate degraded Arizona rangelands (Cable 1971; Jordan 1981; Cox
and others 1987). It has great value for erosion control,
particularly in areas with altered site potential which are
no longer capable of supporting native species. It also
provides nutritious and palatable forage for livestock production. However, managers of wildlife sanctuaries, nature preserves, and wilderness areas are interested in
controlling the spread of Lehmann lovegrass and restoring native grasses. Lehmann lovegrass spreads aggressively beyond the boundaries of seeded stands and can invade and displace native grasses (Kincaid 197l; Cable
1971; Anable and others 1992; McClaran and Anable 1992).
Where exotic grasses dominate, the biodiversity of plant
and animal communities may be decreased (Bock and others 1986). In addition Lehmann lovegrass has the potential to alter fire regimes by producing much more aboveground biomass than native grasses (Cox and others 1990).
Fire enhances its germination, putting a cycle in motion
which can perpetuate Lehmann lovegrass (Ruyle and others 1988; Sumrall and others 1991; Anable and others
1992). The purpose of this study was to determine the effects of Lehmann lovegrass canopy manipulations on the
Methods
The Lehmann lovegrass stand was manipulated using
four different treatments applied on three blocks in a
randomized complete block design. For the burn treatment, Lehmann lovegrass stands were burned to remove
the mature canopy and kill adult plants prior to seeding.
For the mow treatment Lehmann lovegrass canopies were
sprayed with glyphosate in spring and mowed prior to
seeding into the mulch. For the dead standing treatment,
Lehmann lovegrass was sprayed with glyphosate and the
species seeded into the standing dead canopy. For the
control treatment, species were seeded directly into intact
stands of Lehmann lovegrass. These manipulations affected the seedbed environment by altering light, temperature, and moisture relations. Lehmann lovegrass seed
germination is enhanced by red light and fluctuating diurnal temperatures (Roundy and others 1992). For these
reasons the mow and dead standing treatments were expected to suppress the expression of the Lehmann lovegrass seedbank. Lehmann lovegrass germination from
the seedbank increases after fire (Ruyle and others 1988;
Sumrall and others 1991). Native grasses may require
longer periods of available soil moisture than Lehmann
lovegrass in order to establish, conditions which could be
provided by the mow or dead standing treatments.
In: Roundy, Bruce A.; McArthur, E. Durant; Haley, Jennifer S.; Mann,
David K., comps. 1995. Proceedings: wildland shrub and arid land
restoration symposium; 1993 October 19-21; Las Vegas, NV. Gen. Tech.
Rep. INT-GTR-315. Ogden, UT: U.S. Department of Agriculture, Forest
Service, Intermountain Research Station.
S. H. Biedenbender and L. Abbott are Graduate Students in the School
of Renewable Natural Resources, University of Arizona, Tucson, AZ 85721.
B. A. Roundy is Professor in the Dept. of Botany and Range Science,
Brigham Young University, Provo, UT 84602
52
The research plots were instrumented in order to relate
seedling establishment to environmental conditions. Meteorological variables included precipitation, relative humidity, wind speed, air temperature, and solar radiation.
Soil temperature at 1 cm soil depth was measured by thermocouple probes. Soil water tension was measured at 1-3,
6-8, and 12-14 cm by gypsum blocks. Hourly averages of
the variables were recorded by microloggers.
There were two planting dates, early June and early
August, and the experiment was repeated for 2 years.
June is the traditionally recommended seeding date for
southern Arizona, prior to the summer rains. However,
late summer rains might be more reliable than those occurring early in the summer. Some native grasses may
germinate rapidly in response to initial light rains and
then desiccate and die during ensuing dry periods. Lehmann lovegrass, on the other hand, tends to delay germination until moisture conditions are adequate for establishment (Abbott and others 1994). Seeds were sown in
10-meter rows at a depth of 0.6 cm and at a rate of 1 pure
live seed per cm of row.
for approximately 7 days, then increased for 7 days before
it rained again in late July (Figure 2). August-sown seeds
were planted into a moist seedbed created by rains at the
end of July and beginning of August. However, the seedbed dried out within 3 to 5 days and remained dry until
late August. Only a few seedlings established from the
August seeding.
Results
Rainfall patterns for the summer of 1992 were atypical
in that rainfall was relatively well distributed in July but
not in August (Figure 1). As a result, seedlings emerged
in July after the June seeding, but very few emerged after
the August seeding. There was little difference in soil water tension among treatments at 1-3 cm, just below the
sowing depth, although the burn treatment dried out somewhat more quickly than the other treatments (Figure 2).
At 6-8 and 12-14 cm soil depths, the mow and the dead
standing treatments retained moisture somewhat longer
than the burn and the control treatments (Figure 2).
June-sown seeds received initial rains in early July,
3 weeks after planting. Soil water tension remained low
Figure 1—Precipitation from July through August
1992 at the Santa Rita Experimental Range.
Figure 2—Soil water tension in 1992 at 1-3, 6-8,
and 12-14 cm soil depth in relation to various
Lehmann lovegrass canopy manipulations.
53
Figure 3—June 1992 sown native grass and
Lehmann lovegrass seedling densities at the end
of the summer growing season in relation to various Lehmann lovegrass canopy manipulations.
Bothriochloa barbinodis = BOBA; Bouteloua
curtipendula = BOCU; Digitaria californica =
DICA; Setaria leucopila = SELE; Leptochloa
dubia = LEDU; Eragrostis lehmanniana = ERLE.
Figure 5—June 1993 sown native grass seedling density at the end of the summer growing
season in relation to various Lehmann lovegrass canopy manipulations. Bothriochloa
barbinodis = BOBA; Bouteloua curtipendula =
BOCU; Digitaria californica = DICA; Eragrostis intermedia = ERIN; Leptochloa dubia =
LEDU; Setaria macrostachya = SELE.
Seedling density for the 1992 June planting measured
at the end of the growing season (Figure 3) showed significant treatment by species interactions (p < 0.05). Five
native species emerged. The mow treatment had greater
seedling density than the burn and control treatments for
cane beardgrass, Arizona cottontop, and plains bristlegrass. The dead standing treatment also had greater density than the burn and the control treatments for Arizona
cottontop. Lehmann lovegrass seedling density from sown
seeds and the residual seedbank was highest on the burn
treatment. Emergence of all species was limited on the
control treatment, where species were seeded into living
Lehmann lovegrass stands, even though soil water tension at 1-3 cm differed little from the other treatments.
Native seedling height for the June planting was also
measured at the end of the first growing season. Overall,
the tallest seedlings were found in the mow treatment,
but there was no statistical difference in seedling height
between the mow and the dead standing treatments.
There were no significant differences among the dead
standing, burn, and control treatments. Seedling heights
averaged 4.0, 12.9, 9.5, and 0.1 cm for the burn, mow, dead
standing, and control treatments, respectively.
In 1993 precipitation patterns were more typical (Figure 4). Seeds sown in early June received 13 mm of rain
on 1 July, then experienced 6 dry days followed by 8 more
days of rain, then 2 dry weeks. Few seedlings established
from the June planting and many seedlings which emerged
suffered mortality (Figure 5). Seeds sown in early August
received 7 days of rainfall, 4 dry days, then frequent and
consistent precipitation through the month of August.
Many seedlings emerged and survived from the August
planting (Figure 6). Soil water tension, like in 1992,
showed little difference between treatments at 1-3 cm except that the burn treatment dried out somewhat faster
than the other treatments (Figure 7). June-sown seeds
experienced alternating wet and dry conditions in early
July and a long dry period from mid-July to early August.
August-sown seeds also experienced alternating wet and
dry conditions, but the length of the periods between rains
was shorter.
For the June planting in 1993, there were no significant
treatment differences (p < 0.05) in seedling density for
cane beardgrass, sideoats grama, Arizona cottontop, and
plains lovegrass (Figure 5). Green sprangletop and plains
Figure 4—Precipitation from July through August
1993 at the Santa Rita Experimental Range.
54
had the highest establishment, and it performed best on
burn plots. These differences can be attributed to the different rainfall patterns seen in the 2 years. Neither plains
lovegrass nor bush muhly successfully established in either year. Sideoats grama showed no significant difference in establishment among treatments for 1992 and
Figure 6—August 1993 sown native grass
seedling density at the end of the summer
growing season in relation to various Lehmann
lovegrass canopy manipulations. Bothriochloa
barbinodis = BOBA; Bouteloua curtipendula =
BOCU; Digitaria californica = DICA; Eragrostis
intermedia = ERIN; Leptochloa dubia = LEDU;
Setaria macrostachya = SEMA.
bristlegrass had significantly greater establishment on
the burn treatment. However, the average density was
fewer than three seedlings per meter of row. For the
August planting (Figure 6), average seedling density was
10 times the magnitude of the June seeding. There were
no significant treatment differences for cane beardgrass
and plains lovegrass, but the burn treatment produced
significantly more sideoats grama, Arizona cottontop, and
green sprangletop seedlings. The control treatment had
the lowest seedling density, but it was only significantly
less than the mow and the dead standing treatments for
Arizona cottontop. However, the vigor of seedlings in the
control treatment was extremely low.
As expected, Lehmann lovegrass emerged in significantly greater numbers from the burn treatment, and
seedling emergence was suppressed by the mow, the dead
standing, and control treatments (Figure 8). Density of
mature Lehmann lovegrass plants was reduced by the
burn treatment, but lovegrass density on the mow and the
dead standing treatments was not significantly different
than the control treatment, indicating that the herbicide
application was not effective in killing mature Lehmann
lovegrass plants. Forbs were most numerous in the control treatment, followed by the burn treatment, and lowest
in the dead standing and mow treatments.
Conclusions
In terms of native species responses, there were significant species-by-treatment interactions. In 1992 cane
beardgrass had the highest seedling establishment and it
established best on mow plots. In 1993 green sprangletop
Figure 7—Soil water tension in 1993 at
1-3, 6-8, and 12-14 cm in relation to various
Lehmann lovegrass canopy manipulations.
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examination of climatic records for a region may reveal
patterns which could indicate optimum seeding dates for
maximizing the chances of revegetation success.
References
Abbott, L.; Roundy, B. A.; Biedenbender, S. H. 1994. Seed
fate of warm-season grasses. In: Proceedings: Wildland
shrub and arid land restoration symposium; 1993 Oct.
19-21; Las Vegas, NV. Gen. Tech. Rep. INT-GTR-315.
Ogden, UT: U.S. Department of Agriculture, Intermountain Research Station: 37-43.
Anable, M. E.; McClaran, M. P.; Ruyle, G. B. 1992. Spread
of introduced Lehmann lovegrass (Eragrostis lehmanniana Nees) in southern Arizona, USA. Biological Conservation 61:181-188.
Bock, C. E.; Bock, J. H.; Jepson, K. L.; Ortego, J. C. 1986.
Ecological effects of planting African lovegrasses in
Arizona. National Geographic Research 2:456-463.
Cable, D. R. 1971. Lehmann lovegrass on the Santa Rita
Experimental Range, l937-1968. Journal of Range Management 24(1):17-21.
Cox, J. R.; Martin, M. H.; Ibarra-F, F. A.; Folurie, J. H.;
Rethman, N. G.; Wilcox, D. G. 1987. Effects of climate
and soils on the distribution of four African grasses. In:
Seed and seedbed ecology of rangeland plants symposium: proceedings; April 21-23; Tucson, AZ. USDA-ARS.
p. 225-241.
Cox, J. R.; Ruyle, G. B.; Roundy, B. A.; 1990. Lehmann
lovegrass in southeastern Arizona: biomass production
and disappearance. Journal of Range Management
43(4):367-372.
Jordan, G. L. 1981. Range seeding and brush management on Arizona rangelands. Arizona Agriculture Extension Bulletin T-81121: 63-73.
Kincaid, D. R.; Holt, G. A.; Dalton, P. D.; Tixier, J. S.
1959. The spread of Lehmann lovegrass as affected
by mesquite and native perennial grasses. Ecology
40(4):738-742.
McClaran, M. P.; Anable, M. E. 1992. Spread of introduced
Lehmann lovegrass along a grazing intensity gradient.
Journal of Applied Ecology 29:92-98.
Roundy, B. A.; Taylorson, R. B.; Sumrall, L. B. 1992.
Germination responses of Lehmann lovegrass to light.
Journal of Range Management 45:81-84.
Ruyle, G. B.; Roundy, B. A.; Cox, J. R. 1988. Effects of
burning on germinability of Lehmann lovegrass. Journal of Range Management 41(5):404-406.
Sumrall, L. B.; Roundy, B. A.; Cox, J. R.; Winkel, V. K.
1991. Influence of canopy removal by burning or clipping on emergence of Eragrostis lehmanniana seedlings. International Journal of Wildland Fire 1(1):35-40.
Figure 8—Juvenile and mature Lehmann lovegrass (ERLE) and forb seedling densities on
August 1993 plots at the end of the summer
growing season in relation to various Lehmann
lovegrass canopy manipulations.
1993. Arizona cottontop established better on the mow
and dead standing treatments than the burn and control
treatments in 1992, but showed no significant difference
among treatments in 1993. In 1992 plains bristlegrass
did not establish on the control treatment and showed
no significant differences among the other treatments; in
1993 it established significantly better on the burn treatment than on the others.
In 1992 the mow treatment and in 1993 the burn treatment had the best overall native seedling establishment.
Lehmann lovegrass seedling emergence was suppressed
by the mow and dead standing treatments and enhanced
by the burn treatment. The control treatment had the
lowest establishment overall for seedlings of all species.
Because Lehmann lovegrass has tremendous seedling
establishment potential from seedbanks, controlling and
replacing Lehmann lovegrass will probably require a twostep plan. The first step would be a treatment to force the
expression of the seedbank, such as burning, then a followup treatment to kill juveniles and surviving adult lovegrass plants, such as an herbicide treatment, prior to
seeding the desired species.
Ultimately, precipitation patterns and amounts are the
most important factors in determining seedling establishment for revegetation in semi-arid climates. Precipitation
is variable and unpredictable from year to year. However,
56