Single and repeated burning effects on New Mexico blue grama range

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Single and Repeated Burning Effects
on New Mexico Blue Grama Range
Bulletin 800
Kirk C. McDaniel1, Christian A. Ebel2, L. Allen Torell3, and Dawn M. VanLeeuwen4
Agricultural Experiment Station • College of Agricultural, Consumer and Environmental Sciences
Department of
Animal and Range Sciences
SUMMARY
Research from 1990 to 2006 investigated prescribed fire and herbicide applications for control of broom snake­weed (Gutierrezia sarothrae (Pursh) Britt. & Rusby) on blue grama (Bouteloua gracilis [Kunth in H.B.K.] Lag.ex Griffiths) rangeland near Corona, New Mexico. From 1990 through 1993 when broom snakeweed populations averaged >2 plants/m², herbicide (picloram) treatments eliminated most broom snakeweed and increased grass yield about 42% relative to untreated areas. Prescribed fires during this period also eliminated most broom snakeweed, but grass yield did not increase relative to untreated areas. Later repeat fires conducted at intervals <5 years in length resulted in a 25% decline in grass yield relative to untreated rangeland when averaged over the entire study. Fires repeated at >6 years intervals generally did not retard grass yield except when drought condi­tions occurred the first growing season after burning. At the study’s end, burning treatments resulted in higher bareground cover (average interspace area, 23 cm) and less linear grass cover (27%) compared to herbicide-treated and untreated areas (average 16 cm and 36.5%, respectively). This gave the visual appearance of grass cover as being relatively clumpy and less uniform on burned areas compared to a more uniform and continu­ous grass cover appearance on herbicide-treated and untreated experimental areas. Of the minor grass species studied, only galleta (Pleuraphis jamesii Torrey) seemed to benefit from frequent fire—its linear basal cover nearly doubled relative to untreated areas at the study’s end. Conversely, blue grama linear basal cover was about 9% less on burned areas compared to on nonburned grass­lands. Winterfat (Krascheninnikovia lanata (Pursh) A. D. J. Meeuse & Smit) populations were sustained after most single fires, but repeated burns at <5 year intervals reduced this shrub’s abundance and cover. Our study agrees with others that have shown an increase in grass yield following removal of snakeweed with herbicide spraying. However, we did not note a similar beneficial increase in grass yield after burning. Use of prescribed fire on blue grama range in central New Mexico should be viewed as a control alternative for removing broom snakeweed, but not as management practice for increas­ing forage production.
INTRODUCTION
In New Mexico, blue-grama–dominated grasslands are
often referred to as shortgrass prairie (Allred, 1996),
short-grass-steppe (Lauenroth and Mitchunas, 1992), plains-mesa grassland (Dick-Peddie et al., 1993) or simply, blue grama range (Pieper et al., 1971). In this region, blue grama is widespread across many plant communities and in certain areas comprises >90% of the grass composition (Donart, 1989). Blue grama’s ability to withstand grazing and survive drought, along with its widespread distribution, makes it one of the most important forage species on the prairies east of the Rocky Mountains in the United States.
Broom snakeweed sometimes encroaches to unde­sirable levels on blue grama range, but the shrub can be controlled by herbicide spraying or prescribed fire (Gesink et al., 1973; Pieper et al., 1973; McDaniel et al., 2000). During the mid-1980s, broom snakeweed was exceptionally common on blue grama range in
1Professor, Department of Animal and Range Sciences, MSC 3I, New Mexico State University, P.O. Box 30003, Las Cruces, NM 88003. Phone (575) 646-1191, Fax 646-5441; E-mail: kmcdanie@nmsu.edu.
2Range Specialist, USDA-NRCS, Many, LA, and former research assistant, Department of Animal and Range Sciences, New Mexico State University, Las Cruces.
3Professor, Department of Agricultural Economics and Agricultural Business, New Mexico State University, Las Cruces.
4Professor, Department of Agricultural and Extension Education, New Mexico State University, Las Cruces.