Kirk C. McDaniel

Assessing the Economic, Environmental, and Societal Losses from Invasive Plants on Rangeland and Wildlands1

Abstract A literature review was conducted to summarize information on environmental, economic, and societal losses caused by 16 key invasive plants on rangeland and wildlands in the United States. Results of the literature review indicated that scope of published information ranged from narrow to comprehensive. Extensive quantitative information is published about environmental impacts caused by leafy spurge, downy brome, saltcedar, purple loosestrife, and several knapweeds or starthistle. For other species, quantitative information was limited and references to impacts were mainly anecdotal or observational. The economic impacts of most species were poorly documented. Comprehensive economic analyses conducted on either a state or regional basis were published about leafy spurge, saltcedar, and the knapweeds. Agricultural costs including loss of grazing value were quantified for several additional species, but environmental and societal costs were not included in the analyses. Additional research is needed to quantify economic and environmental losses of invasive nonnative plants on rangeland and wildland sites. Nomenclature: Downy brome, Bromus tectorum L. #3 BROTE; leafy spurge, Euphorbia esula L. # EPHES; purple loosestrife, Lythrum salicaria L. # LYTSA; saltcedar or tamarisk, Tamarix spp., # TAASS; yellow starthistle, Centaurea solstitialis L. # CENSO. Additional index words: Exotic plants, invasive plant impacts, noxious weed impacts.

Broom snakeweed control with fire on New Mexico blue grama rangeland

Multiple fires conducted in spring (March-April) and summer (June-July) on blue grama (Bouteloua gracilis [H.B. K. Lag.]) grassland near Corona, N.M. were used to relate broom snakeweed (Gutierrezia sarothrae [Pursh] Britt &Rusby) control to pre-burn vegetation, weather, and fire conditions. Spring fires moved faster and burned cooler than summer fires as indicated by measurements from thermocouples giving the fires rate of spread, temperature, and heat. In spring, broom snakeweed was in the bud stage with little green foliage and fires provided less average crown destruction (8%) and shrub mortality (65%) compared to summer fires (66% crown destruction, 92% mortality) when the shrub was growing actively. Air temperature and total fuel biomass positively influenced fire temperatures, and duration of heat above 60 degrees C resulting in high broom snakeweed mortality. Conversely, as relative humidity, wind speed, and fuel moisture increased, fire heat decreased, resulting in less broom snakeweed mortality. Attempts to conduct spring or summer fires over a 6-year period in central New Mexico were complicated and often unsuccessful because of unsuitable weather and fuel conditions. We concluded ideal weather conditions must converge before, during, and after a prescribed burning event in order to maximize broom snakeweed control and forage growth on these grasslands.

Overstory-understory relationships for broom snakeweed-blue grama grasslands.

Data collected over a 11-year period at 2 study areas near Vaughn and Roswell, N.M. were used to define equations that relate grass biomass to the amount of broom snakeweed (Gutierrezia sarothrae [Pursh] Britt. & Rusby) occupying blue grama (Bouteloua gracilis [H.B.K. Lag]) rangeland over time. A 5 parameter sigmoidal growth equation and a negative exponential equation best expressed the relationship between understory grass biomass and overstory broom snakeweed biomass. Explanatory variables included realized precipitation during the second April to June) and third (July to September) quarters, which coincides primarily with warm-season grass growth. Minimum suppression of grass biomass occurred with complete elimination of broom snakeweed, suggesting control strategies with high overstory mortality will likely be most beneficial to understory production.

Grass response following thinning of broom snakeweed.

Complete removal of broom snakeweed resulted in perennial grass production 833% of that on untreated rangeland after one growing season, and 712% and 300% the second and third year, on a pasture heavily grazed and in poor range condition. On a moderately grazed pasture in good range condition, grass standing crop increased 42% the first year, 81% the second, and 25% the third compared to untreated rangeland. Perennial grass production on the heavily grazed pasture was far below that on the moderately grazed pasture at the start of the study (40 vs 454 kg/ha). After 3 years, with complete broom snakeweed removal and no grazing, perennial grass production was comparable on the pastures once heavily and moderately grazed (1014 vs 939 kg/ha, respectively). Broom snakeweed (Xanthocephalum sarothrae) is a serious perennial weed problem on rangeland in New Mexico. The problem is two-pronged in that, under some conditions, broom snakeweed is poisonous, causing abortion in cattle (Sperry and Robinson 1963), and the weed competes with more valuable forage plants (Ueckert 1979). Platt (1959) estimated that species of the genus Gutierrezia (since treated as Xanthocephalum, Correll and Johnson 1970) occurred on more than 350 million ha of rangeland in the United States. Broomr snakeweed is native on about 60% of New Mexico rangelands. Broom snakeweed populations have increased and subsequently decreased in a cyclic pattern at the Fort Stanton Experimental Ranch in New Mexico following droughts in 1970-71, 1974, and 1976 (Pieper and Donart 1973). Above-average fall, winter, and spring precipitation following drought years appears to be related to the establishment of broom snakeweed on the blue grama (Bouteloua gracilis) range. Since some studies (Jameson 1970, Vallentine 1971) and observations indicate that broom snakeweed populations are cyclic, it seems logical to assume that these plants are fairly short lived. Dittberner (1971) analyzed permanent quadrat records from the Jornada Experimental Range in southern New Mexico collected over a 53-year period and found the average life span of all age classes of snakeweed to be about 2.5 years. Dittberner determined that nearly 70% of the broom snakeweed seedlings die in the first year. Plants living beyond the first year were found to have an average life span of about 4 years. Longevity of the oldest plants ranged up to 15 years. Mature broom snakeweed begins its seasonal growth in late winter to early spring in the Southwest (Ragsdale 1969). Dormant buds, developed in a band above and below the root crown, initiate growth earlier than associated grasses. Because of the competitive advantage from this early growth, there is evidence that production of perennial grasses is decreased where broom snakeweed densities are high. Ueckert (1979) reported herbage production on short grass range to be severely reduced under a dense stand of broom snakeweed. When Ueckert reduced broom snakeweed by 25 and Authors are assistant professor, professor, and professor, Department of Animal and Range Sciences, New Mexico State University, Las Cruces. This report was submitted as Journal Article 793, Agricultural Experiment Station, New Mexico State University, Las Cruces 88003. Manuscript received July 27, 1980. 50%, there was no effect on grass production. However, when all broom snakeweed plants were removed, grass production increased 107%. Broom snakeweed apparently undergoes intraspecific competition as well as interspecific competition with other species (Ueckert 1979). The degree of competition appears dependent upon the population density and the competitive ability of associated species. The objective of this study was to investigate the response of associated species to the removal of broom snakeweed competition. Study Area and Procedures The study was conducted on the Fort Stanton Experimental Ranch 6 km east of Capitan, New Mexico. Average annual precipitation is about 39 cm, with over 60% falling from June through September. Open grasslands on mesas and plateaus are dominated by blue grama. Woodlands occupy steep slopes and rugged hills and are dominated by pinyon and juniper (Pinus edulis and Juniperus monosperma) and wavy-leaf oak (Quercus undulata). Elevation on the ranch varies between 1950 and 2250 m. Two locations selected in 1977 on the Fort Stanton Station represented areas under different grazing intensities and range condition. One area was located in a pasture continuously grazed year-long since 1969 at a heavy stocking rate (18.9 ha/AU). This pasture was considered to be in poor range condition. The second location was in a moderately grazed pasture (23 ha/AU) in good range condition that had also been grazed since 1969. The soil at both locations is from the Dioxice loam series, which is classified as a fine loamy mixed mesic aridic calciustoll. ln May 1977 fences were constructed to exclude grazing from a 0. 1-ha area in each of the two pastures. The fenced areas encompassed a relatively homogeneous stand of I-year-old broom snakeweed plants. Broom snakeweed density was determined by counting all plants within 9 m2 plots, calculating a mean for the exclosure, then uniformly thinning the plants to a desired level by clipping at ground level. Broom snakeweed was reduced by 0, 25, 50, 75, or 100% of the mean density in the heavily grazed pasture, and by 0, 33, 50, 67, and 100% in the moderately grazed pasture. Treatments were replicated four times in a randomized complete block design at each location. Basal cover and standing crop of grasses and forbs were determined annually in the fall at each location. Basal cover was determined by randomly placing a 1 0-point frame along 15 line transects in each plot and recording basal hits for broom snakeweed, forbs and perennial grasses. Herbage standing crop was determined for each species by clipping four 0.25 m2 quadrats in each plot at the end of the growing season. New areas were clipped each season during the 3-year study. All clipped vegetation was separated by species in the field and later oven-dried at 600 C for 72 hrs before weighing. Basal cover and standing crop data were analyzed by analysis of variance. Duncans multiple range tests were used to separate differences among means where appropriate. JOURNAL OF RANGE MANAGEMENT 35(2), March 1982 219 This content downloaded from 207.46.13.129 on Mon, 27 Jun 2016 05:35:25 UTC All use subject to http://about.jstor.org/terms Table 1. Mean density (plants/rM2) of broom snakeweed after thinning plants in May 1977. Natural mortality further reduced the density of plants in 1978 and 1979. Mean density on 10/77 Reduction Mean density on 10/78 Change Mean density on 10/79 Change Heavily grazed pasture 0 100 0.2 1.0 0.4 2.0 6.2 75 4.3 -30.4 0.2 -96.4 12.6 50 7.9 -37.2 1.8 -85.8 18.8 25 8.6 -54.4 0.8 -95.9 25.0 0 9.0 -64.0 1.2 -95.1

Revegetation Strategies After Saltcedar (Tamarix spp.) Control in Headwater, Transitional, and Depositional Watershed Areas 1

Abstract The exotic saltcedar occupies headwater, transitional, and depositional watershed portions, and revegetation strategies can be quite different depending on these locations. Regardless of specific socioeconomic or biological needs (or both), sites must often be revegetated after control to avoid reinfestation or invasion by other exotic species. Where natural riparian hydrologic processes continue to function, natural regeneration can be used as an effective restoration mechanism. However, in altered river systems, harsh environmental site characteristics may occur that severely limit revegetation potential after control, particularly in depositional areas. Because of high costs associated with saltcedar control, revegetation, and follow-up management, specific treatment areas should be evaluated and prioritized based on revegetation potential. Specific consideration should be given to the establishment of sustainable plant communities for long-term exclusion of saltcedar and other exotics. Nomenclature: Saltcedar, Tamarix ramosissima Ledeb. #3 TAARA. Additional index words: Acroptilon repens, Baccharis glutinosa, Distichlis spicata (L.) DISSP, Elaeagnus angustifoiia, ELGAN, imazapyr, Lepidium latifolium, perennial pepperweed, Populus deltoides, riparian restoration, Russian-olive, Salix exicjua, Salix gooddingii, saltgrass, triclopyr.

Broom snakeweed establishment following fire and herbicide treatments.

Broom snakeweed (Gutierrezia sarothrae [Pursh] Britt &Rusby) propagation was monitored from 1990 through 1998 following burning and herbicide control practices conducted on blue grama (Bouteloua gracilis [H. B. K. Lag.]) grasslands near Corona, N.M. Broom snakeweed usually germinated in April, May, or June (83% of 394 total) and mostly in 1991 and 1992 (81% of total) when spring moisture was sufficient. The majority of broom snakeweed seedlings (52% of total) emerged the first or second year after summer burning, especially in areas where grass yield and cover declined and bare ground exposure increased as a result of intense fires. Spring fires caused less damage to blue grama than summer fires, and the number of broom snakeweed seedlings produced (18% of total) was similar to non-treated rangeland (22% of total), but lower than numbers on areas burned in the summer. Grass yield and cover increased within a year of herbicide spraying and treated plots had significantly (P < 0.05) fewer broom snakeweed seedlings (8% of total) than burned and non-treated areas. DOI:10.2458/azu_jrm_v53i2_mcdaniel

Estimating Grass Yield on Blue Grama Range From Seasonal Rainfall and Soil Moisture Measurements

Abstract To estimate annual forage production from moisture conditions it is important to consider the timing and seasonality of precipitation events as well as the past history of storm events. In this study we examined this relationship using 16 yr of annual measurements of herbaceous standing crop recorded at two study sites located on the Corona Range and Livestock Research Center in central New Mexico. Our hypothesis was that end-of-season herbaceous standing crop estimations could be improved using measured soil moisture instead of seasonal accumulations of rainfall as traditionally used for yield prediction. Daily recorded and simulated soil moisture levels were used to estimate the number of days over the growing season when soil moisture by volume was at low (< 20%), intermediate (20% to 30%), or high (≥ 30%) levels. Defining regression equations to include either simulated or probe-recorded measures of soil moisture improved the adjusted R2 of the regression models from 46% for the rainfall model to over 60% for various soil moisture models. Key variables for explaining annual variation in herbaceous production included seasonal moisture conditions, the amount of broom snakeweed (Gutierrezia sarothrae [Pursh] Britt. & Rusby) present on the area, and the degree days of temperature accumulated over the growing season. Diurnal daily temperatures near historical averages were most advantageous for forage production. Simulated soil moisture data improved predictive grass yield estimates to a level equivalent to using onsite moisture probes to categorize daily moisture conditions. Potential exists to better predict forage conditions based on forecast information that uses soil moisture data instead of the traditional input of seasonal rainfall totals.

Perceptions and economic losses from locoweed in northeastern New Mexico.

Livestock producers and others knowledgeable about the locoweed problem in northeastern New Mexico were surveyed to obtain the production information needed to estimate economic losses from locoweed (Oxytropis/Astragalus) poisoning. A partial budgeting approach was used to estimate economic losses based on animal performance differences with increasing levels of poisoning. With current production costs and 1990-96 average beef prices, annual locoweed poisoning losses were estimated to be

Solutions to Locoweed Poisoning in New Mexico and the Western United States: Collaborative research between New Mexico State University and the USDA–Agricultural Research Service Poisonous Plant Lab

75 head-1 for moderately poisoned animals, and

Wyoming big sagebrush control with metsulfuron and 2,4-D in northern New Mexico.

282 head-1 for severely poisoned animals. The most common locoweed management strategy used by northeastern New Mexico ranchers was to move animals observed eating locoweed into locoweed-free areas. Rehabilitation of these animals for an extended period before sale was found to decrease economic loss relative to immediate sale. Moderately and severely poisoned animals that are rehabilitated were estimated to gain 14% and 29% less than non-intoxicated animals. Other management options including chemical locoweed control, fencing, and locoweed aversion were found to be economically justified when relatively high locoweed infestations are anticipated. DOI:10.2458/azu_jrm_v53i4_torell