What Tools are Successful for Rehabilitating Rangelands Affected by Invasive Species Monocultures? Mariel Boldis - University of Nevada Reno, Undergraduate in Rangeland Management
W
hether in your backyard, the ranch you call home, or the public lands you recreate on, non-native plant species invasions challenge the way you do your business or spend time outdoors with family and friends. Non-native plant species have a way of challenging our efforts to restore degraded lands by modifying ecosystem interactions, fi re cycle regimes, carbon and nutrient sequestration, and the hydrology of permanent and ephemeral streams. Many times, invasive species increase in density due to a combination of external influences which may include seasonal timing of precipitation, change in grazing patterns, accidental or purposeful introduction of non-native species, change in wildfi re frequency, and short term climatic shifts.
So what makes invasive species so successful? According to the U.S. Fish and Wildlife Service, there are about 4,300 invasive plant species in the U. S. These species share similar characteristics that allow them to be successful by having: 1. High growth rates 2. Short reproductive life cycles 3. High seed production 4. Efficient dispersal methods 5. High tolerance to climatic variability. The rate and timing of phenology between invasives and non-invasives are keys to their success when monopolizing an area. Monocultures impact our rangelands by decreasing biodiversity, decreasing habitat stability, negatively impacting the livestock industry, and depleting resources that provide ecosystem goods and services to rural and urban communities.
Invasive species and their economic implications The Weed Science Society of America (WSSA) came out with the results of a crop-loss study in 2016 that reported 43 billion dollars in annual losses due to uncontrolled invasive plant species. A case study in Nevada of the impact of non-native invasive plants on wildlife loss related to recreation use values were estimated to be 5 to 17 million 24 November/December 2017
dollars in losses per year, which were predicted to increase to 34 million dollars per year as future expansion of invasive plants continues. In 2000, a study published in BioScience estimated control costs of invasive plants in the U.S. to be roughly 9.7 billion dollars. In 2008, invasive plants cost California alone, 82 million dollars with actual impacts reaching into the billions for crop and ranching activities. Although the costs to Figure 1: Recorded Observations of Invasive Species across the United States treat invasive plant monocultures are high, especially when coupled with herbicide delaying treatment will only increase initial costs of treatment. Conversely, broadcast seeding was eradication, and invasive plant species will continue identified to be the least effective re-vegetation to expand further than before. Figure 1 provides a effort in two separate studies with about 0.5%visual of recorded observations across the United 2.3% germination rates. In another study, States of the invasive species included in this review perennial bunchgrass cover increased 5-10 fold which will only increase in numbers if we fail to while suppressing exotic grass cover 5-fold. provide proper treatment. 2. Fall Drill Seeding of Native Perennial With a variety of methods available to manage Grasses and Forbs (phenology indicating invasive monocultures, mitigating impacts on nonearly germination) target species, impacts on human health, and success Competitive interactions between native and of at least >50% success rates must be considered. invasive species promotes natural selection With so much information and research out there, to take place to select for traits that are able how do we decide what are the best and most effective to compete with invasives; thus, providing treatments for managing invasive monocultures? select native species the ability to reduce the abundance of invasive monocultures. 3. Mowing + Pre and Post Herbicide Treatment Most Effective Treatments: >50% + Outplanting of Introduced Perennial Monoculture Eradication Grasses Of all the introduced perennial grasses, Myoporum was most effective in suppressing In no particular order, the following lists the 6 invasive monocultures. Outplanting of most effective treatments based on greater than 50% Cordia species had the greatest density of success rate recorded within each study. Note: The native vegetation and came in second with treatments listed with herbicide varied in type of suppression of the same invasive monoculture. herbicide used and were followed by a fallow period which varied from study to study. 4. Herbicide Only Herbicide was effective at eradicating 1. Herbicide + Tilling + Fall Drill Seeding of monocultures initially, and a single study Introduced Perennial Grasses indicated Imazapic as the best herbicide for Tilling followed by drill seeding provided 50% increasing native forb cover. Treatment is more emergence than all other techniques The Progressive Rancher
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