Graduate Research Symposium (GCUA) (2010 - 2017) Graduate Research Symposium 2010

Apr 15th, 1:00 PM - 2:30 PM

Assessing invasive plant species as threats in Mojave Desert Assessing invasive plant species as threats in Mojave Desert

parks parks

Sara L. McPherson University of Nevada, Las Vegas

Donovan J. Craig University of Nevada, Las Vegas

Scott R. Abella University of Nevada, Las Vegas, scott.abella@unlv.edu

Follow this and additional works at: https://digitalscholarship.unlv.edu/grad_symposium

Part of the Desert Ecology Commons, Environmental Health and Protection Commons, Environmental

Monitoring Commons, and the Weed Science Commons

Repository Citation Repository Citation McPherson, Sara L.; Craig, Donovan J.; and Abella, Scott R., "Assessing invasive plant species as threats in Mojave Desert parks" (2010). Graduate Research Symposium (GCUA) (2010 - 2017). 12. https://digitalscholarship.unlv.edu/grad_symposium/2010/april15/12

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Assessing Invasive Plant Species as Threats in Mojave Desert ParksSara L. McPherson, Donovan J. Craig and Scott R. Abella

School of Environmental and Public Affairs, University of Nevada Las Vegas, NV.

Background & Approach

Abstract Preliminary Results Conclusion & Research

Literature Cited

Acknowledgements

Further InformationScott R. AbellaAssistant Research Professor (702) 895-5163scott.abella@unlv.edu

Donovan J. CraigResearch Assistant- JFSP and NPS I&M(702) 351-7572donovan.craig@unlv.edu

Sara L. McPhersonGraduate Student(702)771-7979beeninthegarden@yahoo.com

University of Nevada-Las VegasSchool of Environmental and Public Affairs

4505 S. Maryland Parkway, Las Vegas, NV 89154-2040

The invasion and persistence of exotic plant species threatens the natural features that national parks are designed to protect. For example, park managers have witnessed an increase in the frequency, extent and intensity of fires along with a reduction in native species richness and diversity. Many park managers are familiar with a suite of highly invasive plants, but lack a comprehensive and systematic way of prioritizing invasive plant species based on potential threats to the parks’ resources. We have entered into a collaborative project with the National Park Service’s Inventory and Monitoring program to develop an invasive plant early detection and monitoring protocol for the Mojave Desert Network (MOJN), which includes seven national park units. Our first step was to identify and prioritize invasive plants presently occurring or having the potential to invade each of the seven parks. To date, we have compiled a list of 350 species considered unnatural or weedy to the Mojave Desert region. From this comprehensive list, 154 were identified as having a medium or higher impact on the desert ecosystem. Since the MOJN hosts a wide variety of habitat types, our second step was to identify locations that are most vulnerable to invasion. We are currently synthesizing existing literature on species richness and elevation relationships, life-history and spatial distribution for these plants species.

PurposeThe overall purpose of this project is to develop a monitoring protocol that consistently and comparably describes how to collect, manage, analyze, and report invasive species data to assure the effectiveness of the invasive species monitoring programs and reduce costs. More specifically to (1) prioritize targeted species, synthesize the life-history and spatial distribution throughout the MOJN parks and (2) synthesize published literature on the relationship between native and exotic species richness and elevation.

350 total species (park documented or known importance to Mojave region- not truly an absolute number more exotics occur in region)•46 are native to United States, but considered weeds or have been introduced beyond their normal range•304 truly exotic to United States•233 have been documented in MOJN parks (Figure 2 and 3)•Out of the entire 350 species, there are 60 taxonomic families (Figure 4)•154 have been identified as medium or higher impact to park resources

The Mojave Network includes seven National Park Service units (Figure 1) spanning in elevation from the lowest point (-86 m) in North America (Badwater in Death Valley National Park) to a high of 3,981 m (Wheeler Peak in Great Basin National Park). Therefore, a broad perspective and general principles are needed that relate exotic species invasions to native communities, environmental gradients, and disturbance. We have specifically focused on two questions: (1) How strong is the relationship of exotic and native species richness in un-manipulated communities? (2) Does the propensity for exotic species invasions vary along environmental landscape gradients? Answering these questions involved compiling results from studies that have compared exotic and native species richness among discrete habitat types or along continuous gradients in native richness (Table 1). Question 1, for example, was addressed by conducting an advanced literature search in six databases: Science Direct, Agricola, Scopus, Academic Search Premier, Jstor, Web of Knowledge and http://scholar.google.com/ We specifically searched all years for articles that had ‘exotic and richness’ in the title and were in English. There were a total of 35 initial articles and 708 published articles after cross referencing and eliminating duplicates. These articles are currently being screened based upon two criteria: (1) Must be in an un-manipulated community (2) Have reported on quantitative relationships of native and exotic plant species richness or diversity

Patterns of invasion produce significant challenges for land managers that are concerned that natural landscapes may be presently or inevitably invaded (Stohlgren, 1999, Stohlgren, 2002). Internal feedbacks and spatial-autocorrelation effects may accelerate invasions (Bergelson, 1993) causing an arguably preventable decline in ecosystem diversity (Billings, 1990, Bock, 1986, D'Antonio, 1992). To hamper this fate, land managers have determined early detection is critical (Stohlgren, 1998) and additional research is needed to determine the long-term ramifications. However, early detection of nonnative species, control and restoration efforts are difficult because there is a need for sophisticated and intensive inventory and monitoring programs and spatial and ecosystem models (Chong, 2001).The projected monitoring program will have multiple applications: in a larger context it is an investment in the quality of human and environmental health of our nation. Specifically to the MOJN will aid in operational and managerial effectiveness: assisting park managers in developing a broad-based scientific understanding of the status and long-term trends such as composition, structure and function of park resources. Resource managers could utilize species-specific information to prioritize which species might be the most damaging to indigenous ecosystems and warrant the most attention for monitoring and control. Relationships between native and exotic species diversity could help understand which areas of the landscape are most prone to invasion by exotic species. Overall, it will support confident and effective decisions made in areas such as control and mitigation, research, and education.

The MOJN has funded this study through a cooperative agreement with UNLV. We would like to thank the National Park Service (NPS) for providing invasive species pictures. We would also like to acknowledge Marilyn Hanson for providing the buffelgrass photo. Additional thanks to the Mojave Network staff for producing the Mojave Desert Network map.

y = 5E-05x + 48.127R² = 0.6759

y = 8.8953ln(x) - 32.875R² = 0.8196

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Exotic Plant Richness by Park Area

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Exotic Plant Richness by Park Area

Asteraceae15%

Brassicaceae9%

Chenopodiaceae4%

Fabaceae6%

Poaceae25%Solanaceae

4%

Other37%

Taxonomic Breakdown of Exotic Plants Important to Mojave Desert Network

Abensperg-Traun. (1998). Exotic plant invasion and understory species richness: a comparison of two types of eucalypt woodland in agricultural Western Australia. Pacific Conservation Biology , 4, 21-32.Aguiar. (2001). Exotic and Native Vegetation Establishment Following Channelization of a Western Iberian River. Regul. Rivers: Res. Mgmt. , 17, 509-526.Aguiar, F. (2006). Patterns of exotic and native plant species richness and cover along a semi-arid Iberia river and across its floodplain. Plant Ecology , 184, 189-202.Austrheim, G. (2002). Plant Diversity Patterns in Semi-Natural Grasslands along Elevational Gradient in Southern Norway. Springer , 161, 193-205.Bergelson. (1993). Rates of weed spread in spatially heterogeneous environments. Ecology , 74, 999-1011.Billings. (1990). Bromus tectorum, a biotic cause of ecosystem impoverishment in the Great Basin. Ecology , 301-322.Bock. (1986). Ecological effects of planting African lovegrass in Arizona. National Geographics Research , 2, 456-463.Brown, R. (2003). Diversity and Invasibility of Southern Appalachian Communities. Ecological Society of America , 84 (1), 32-39.Carey, S. (2006). Effect of community assembly and primary succession on the species-area relationship in disturbed ecosystems. Ecography , 29, 866-872.Celesti-Grapow, L. (2006). Determinants of native and alien species richness in the urban flora of Rome. Diversity and Distribution , 12, 490-501.Chong. (2001). New approaches for sampling and modeling native and exotic plant species richness . Western North American Naturalist , 328-336.Cofer, S. (2008). Species richness and exotic species invasion in middle Tennessee cedar glades in relation to abiotic and biotic factors. Journal of the Torrey Botanical Society , 540-553.D'Antonio. (1992). Biological invasions of exotic grasses, the grass/fire cycle, and global change. Annual Review of Ecology and Systematic , 23, 63-87.Godfree, R. (2004). Ecological filtering of exotic plants in an Australian sub-alpine environment. Journal of Vegetation Science , 15, 227-236.Harrison, S. (2006). Invasion in a Diversity Hotspot: Exotic Cover and Native Richness in the Californian Serpentine Flora. Ecological Society of America , 87 (3), 695-703.Houlahan, J. (2004). Effect of Invasion Plant Species on Temperate Wetland Plant Diversity. Conservation Biology , 18 (4), 1132-1138.Lavoie, C. (2003). Exotic plant species of the St. Lawrence River wetlands: a spatial and historical analysis. Journal of Biogeography , 30, 537-549.Planty-Tabacchi, A.-M. (1996). Invasibility of Species-Rich Communities in Riparian Zones. Conservation Biology , 10 (2), 598-607.Ricotta, C. (2009). Patterns of native and exotic species richness in the urban flora of Brussels: rejecting the 'rich get richer' model. Springer .Safford, H. (2001). Grazing and Substrate Interact to Affect Native vs. Exotic Diversity in Roadside Grasslands. Ecological Applications , 11 (4).Sax, D. (2002). Native and naturalized plant diversity are positively correlated in scrub communities of California and Chile. Diversity and Distributions , 8, 193-210.Smith, M. (1999). Exotic plant species in a C4-dominated grassland: invasibility, disturbance, and community structure. Oecologia , 120, 605-612.Stohlgren, T. (2002). Assessing Vulnerability to Invasion by Non-Native Plant Species at Multiple Spatial Scales. Environmental Management , 29 (4), 566-577.Stohlgren, T. (1999). Exotic Plant Species Invade Hot Spots of Native Plant Diversity. Ecological Society of America , 25-46.Stohlgren, T. (1998). Riparian zones as havens for exotic plant species in the central grasslands. Plant Ecology , 138, 113-125.Stohlgren, T. (2003). The rich get richer: patterns of plant invasion in the United States. Front Ecol Environ , 1 (1), 11-14.Tsuyuzaki, S. (2002). Vegetation development patterns on skislopes in lowland Hokkaido, northern Japan. Biological Conservation , 239-246.Warner. (2003). The Criteria for Categorizing Invasive Non-Native Plants that Threaten Wildlands. California Exotic Pest Plant Council and Southwest Vegetation Management Association , 24.

In developing the invasive plant monitoring protocol, our first step was to compile a comprehensive list of exotic and invasive species known to occur within parks and those with a potential to invade parks. Many sources of information were consulted to compile this list, such as state noxious weed lists and park exotic plant inventories. A total of 350 species were compiled and from that list, a series of decisions were made to form a shorter "target" list of priority species. Decisions included state noxious status in states that encompass the Mojave Desert (AZ, CA, NV, and UT), and whether the species had been evaluated by the "Criteria for Categorizing Invasive Non-native Plants that Threaten Wildlands" (Warner et al. 2003). Once the list had been narrowed down by the decision tree, it included 154 species.

Author, Year Quantitative Relationship between Native and Exotic RichnessAbensperg, 1998

Cover of exotics was negatively correlated with total (native) plant species richness (r=0.70)(r=-0.87)Aguiar, 2006 On the floodplain scale, the species richness of native and exotic plants was positively and consistently

correlated (r=0.60, P<0.001). Celesti-Grapow, 2006

*strong positive relationship between the number of archaeophytes and that of native species (r2 = 0.23) *high explanatory power (r2 = 0.68)*significant relationships between neophytes and native species were all positive. *strongest to weakest effect: riverside habitats, parks, archaeological sites, recently developed areas *relationship was non-significant in woodlands, residential areas and historical centre. *grasslands, the effect of native species on neophytes was negative

Cofer, 2008 Exotic species richness was unrelated to native species richness when size of glades was statistically controlled (r=0.169-0.629)

Godfree, 2004 All plots, *no significant relationship (r = – 0.13), native and exotic species richness were weakly correlated

Harrison, 2006 Strongly and positively correlated (r =0.80). Exotic cover and total native herb richness were positively correlated not strongly (r =0.21). Exotic cover and endemic herb richness were negatively correlated (r =-0.48), as were exotic cover and rare herb richness (r =-0.38). The correlations between exotic richness and native richness were similar to those between exotic cover and native richness (r=0.12 for total, r=-0.50 for endemic, and r=-0.42 for rare herb richness). (r=0.21-0.80)

Houlahan, 2004 There was a *positive relationship between native (S) and (Se) exotic species richness (r =0.405), but no statistically significant relationship between (rare) Sr and (exotic) Se (r = 0.005).

Lavoie, 2003 Exotic species represented 6-44% of cover. From Lake St Louis to Lake St Pierre, there is a significant but *weak negative linear relationship (r2 0.075) between the number of native plant species per sampling station and the relative exotic cover. a strong significant quadratic relationship between diversity and exotic plant cover ( r2 =0.452).

P. -Tabacchi, 1996 Significant linear relationship between the total number of species and the number of alien species r=0.64

Safford, 2001 Total species richness (r2 = 0.66). Within serpentine soils, species richness increased weakly with relative grazing intensity (r2 = 0.21, P < 0.05). Proportion native species (r2 = 0.81).

Sax, 2002 Varied based upon elevation, fire and naturalization* Positive Relationship (r=0.14-0.86)Stohlgren, 1998 Positive correlation between nonnative species richness and foliar cover at the plot scale (r2= 0.77, P=0.001)

and vegetation-type scale (r =0.83, P=0.001).Stohlgren, 2002 There were significant positive relationships between the nonnative species richness and native species

richness. Foliar cover: strongly *positively correlated with the nonnative species richness at the plot scale (r=0.77) and vegetation-type scale (r=0.83)

Stohlgren, 2003 At a plot scale, strongly *positive, (r = 0.33). At the state scale, we found a positive, nearly significant correlation between native and non-native species richness (r = 0.28). Our findings strongly agree with global-scale results, which have reported even stronger positive relationships between native and non-native species richness in parks and natural areas (r = 0.83; Lonsdale 1999).

Overall Protocol Species Prioritization

Out of the 154 species of medium or higher priority to the parks: •12 are strictly aquatic species:

•11 true exotics, 1 noxious native •2 found in MOJN park(s) (LAME only) and 10 have not

•142 are terrestrial: •80 have been found in MOJN parks, 62 have not•10 are natives and 132 are true exotics

Park Area (ha)

Table 1

Figure 2

Figure 3

Figure 4

Figure 1.

Protocol Specific

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