Case Studies of Invasive Plant Impacts (unintentional, “assisted invasion”)

1. LOCAL FLORA – Lecture 12 Dr. Donald P. Althoff Case Studies of Invasive Plant Impacts (unintentional, “assisted invasion”) Bison and the “Iron Bison” LEC 11

2. Introduced Bison Aiding Dispersal of Exotic Plants • ______________is a major process that can that can influence any extension of the distribution of a plant (native or non-native) a) ensure the “next” plant can land “some” distance from the parent plant b) that next place where it lands might be favorable with respect to growing conditions c) multiple seeds with multiple introductions or re-introductions

3. Case Study: Introduced Bison on Santa Catalina Island, CA Constible, J.M., R. A. Sweitzer, D.H. Van Vuren, P.T. Schuyler, and D.A. Kemp. 2005. Dispersal of non-native plants by introduced bison in an island ecosystem. Biological Invasions 7:699-709

4. Santa Catalina Island is about 25 miles (40 km) west of Los Angeles, California Island is 74 mi2 (=194 km2 = _______ Acres) Has Mediterranean climate, having moderate temperatures throughout the year, most rainfall is November - April

5. 3 major upland habitat types: • Coastal sage scrub • Grassland (dominated by non-native annual grasses • and forbs • Island chaparral (dominated by evergreen and • drought-resistent shrub and “short” trees

6. History of the Island • Many of the plants (annual grasses and forbs) on the island are of ________________ origin • Santa Catalina Island Conservancy (SCIC) owns approximately 88% of the island—mostly the interior portions. SCIC mission is to conserve native biotic and abiotic resources and restore ecosystem functioning including ___________ of invasive species believed to have significant negative impacts • Between 1924-1935, 25 bison introduced to island. Prior to this, no large grazing animals on the island. Approximately _____ of island “available to bison to graze/roam.

7. More on the bison herd…. • Herd is culled every 1-2 years since 1993 to maintain it at 185-250 animals • Removal (i.e., eradication) of the herd has been “delayed” and/or not attempted because of a) _________ importance to island residents b) _________importance to island residents • As of 2003, SCIC plan has been to maintain herd at 150 animals by periodic removals and contraceptive program

8. Bison have significant potential to disperse non-native plants: 1) 2)

9. The spreading by hair clumps is aided by _______ (dusting sites), which can both retain moisture because of the depression made in the ground over time, “release” of soil that can become part of matted hair still clinging to the bison, and provide ____________ sites (i.e., exposed sites) for seed germination and minimal competition

10. Bison can disperse seeds two ways: • _________________ – ingestion and later excretion of seeds (i.e., fecal pats). Process fairly well documented….more so cattle, which pass large numbers of viable seeds contributing to recruitment of native and non-native plant populations • ________________ – attachment of seeds to the body of the animal. Thought to be less common mechanism of seed dispersal

11. Epizoochory considerations…. • Bison have thick, curly hair…ideally suited for adhesion of barbed, hooked, or viscous fruits. On the island, with Mediterranean climate, almost constant shedding. Therefore, great potential for year-round dispersal • Bison constant use of wallows leading to deposition and germination of non-native seeds

12. Methods included… • Collected 1) clumps of hair shaved from bison (from forelocks…an area that tends to be permanent and accumulate seeds over time when animals are foraging, loafing, and wallowing)-- during yearly roundup and 2) clumps dislodged by wallowing at active wallowing sites • Samples “processed” further to determine species (if possible), abundance, and germination rates (i.e., seed viability)

13. Methods…con’t • Germination trials took place in wire cage protected soils (using Santa Catalina Island soils). Cages prevented access by vertebrates as these were “outside” trials • Also, collected some fresh fecal pats (i.e., dung). Air-dried them, then spread them over bermiculite, and then watered as the same schedule as for the hair clump seed samples to evaluate germination rates

14. Results (2000-2002) • 2,552 seeds extracted from bison hair clumps obtained by shaving • 1,612 seeds extracted from bison hair clumps collected at wallows • Despite similarity in number of plant species (native vs non-native)…. …there were _______________ non-native seeds in hair clumps than native seeds!!!!

15. Bison wallows found in all major habitat types. Wallows distributed throughout most the range of bison on the island (see “dots” above)…but most were ___________________________________________ ___________________________________________

16. Results…con’t • Two of the most common non-native forbs (common horehound = CH & rough cocklebur = RC) found in hair clumps are thought to only get to novel (i.e., new) habitats by ________________. The viability of these two forb species seeds was ____ (CH) & _____ (RC) in shaved hair clumps and _____ (both CH & RC) from wallow hair clump samples • Majority of plants that germinated from wallows hair clump trails were _________

17. Conclusions • Bison weren’t the only “agent” of dispersal (i.e., humans, native field mice, introducd rats, and introduced mule deer), but the combined effects of a) long distance movements by bison & b) disturbance by bison (i.e., wallowing) resulted in a “significant ______________ _____________________ seed dispersal of non-native plant on SCI” • Most of the non-native plants seeds “tranported” are annualshitting __________

18. Conclusions..con’t • Bison hair clumps appear to transfer (transport) more of these seeds that have high rates of germination than fecal pats • Nonetheless, fecal pats have the ability to retain some seeds that will germinate making the _______________ dispersal mechanisms nearly as important as the hair clumps because the fecal pats are so widely distributed on the island— _____________ than the wallows. This includes __________, ____________________________other areas not conducive to wallowing

19. Management Considerations • _______ herd size (or eliminate) on the island • _______ the size of the range for the bison on the island (still allows for tourism viewing) • Relevance to land managers elsewhere: transporting stock from natural or semi-natural foraging grounds (i.e., winter or summer rangelands) can clearly facilitate dispersal of non-native plant seeds. Moving herds in this way can reduce the effectiveness of chemical and mechanical treatments…because of ____________________!!!

21. THE IRON BISON IMPACT:Fragmentation: At-risk landscapes due to invasive plants species

22. “micro” Fragmentation • Power-line right-of-ways • Phone cables • Gas pipelines • Rural water lines • Wind turbine installation and service road network

24. Invasibility of Plant Communities: TWO MAJOR “OPPOSING” THEORIES • Elton (1958) • May (1973) and Huston & DeAngelis (1994)

25. Elton (1958) 1 Exotic species might more easily invade areas of ____ species diversity because areas of high species diversity should use limiting resources more completely…thereby preventing invasion by exotic species

26. May (1973) Huston & DeAngelis (1994) 2 Highly DIVERSE plant communities are intrinsically ________ with some species dropping in and out routinely

27. Stohlgren et al. 1998 At small scales (micro-level), invasive species CAN get established at low cover, bare ground sites--- ex. __________________ Invasive species CAN get established at highly diverse sites because not all resources are used up— ex. __________________ 1 2

28. LCTA at Fort Riley(now RTLA) • Program started in 1989 • Permanent plots established for monitoring trends in vegetation, small mammal, and bird communities • Summarized dataset for 1994-2001 (8 years)

34. Sericea Lespedeza • Chinese lespedeza = Chinese bush-clover • Introduced in U.S. in 1896 for erosion control, hay production, and wildlife cover • Introduced in SE Kansas during 1930s as cover for strip-mined lands; around state and federal reservoirs from 1940s-1970s AND in 1950s as part of soil bank program. • 1 July 2000 declared “state wide noxious weed “ in Kansas.

35. Sericea Lespedeza…con’t • Drought tolerant • __________________________________ • Few natural predators/herbivores • Prolific seed producers—_______ seeds per stem not rare. Result: 1-2 million seeds per acre can be produced • Seeds may be viable up to ________ in the soil

36. IOC = 0.42 Introduced

37. MPRC 100,000 acres IMPACT ZONE

38. Year-New Plots-Areas 01 1995 – 4 - 3 00 01 1996 – 5 - 2 00 1997 – 1 - 0 1998 – 2 - 2 98 99 1999 – 5 - 2 96 00 00 2000 – 7 - 3 98 99 95 2001 – 2 - 2 95 00 00 99 96 96 95 95 00 99 96 99 97 96 Sericea lespedeza

39. IOC = 0.42

42. Year-New Plots-Areas 1995 – 2 - 2 1996 – 4 - 2 99 1997 – 1 - 0 98 1998 – 7 - 5 1999 – 5 - 0 98 97 95 2000 – 2 - 0 96 99 2001 – 0 - 0 98 98 96 98 00 00 99 98 99 Johnson grass 98 96 96 99 95

43. Key Points: Fragmentation • It can be at a very __________ scale • Invasive plants (exotics) can easily acquire ______ or _________ to disperse to favorable, recently “_____” ____________ landscapes • High diversity of surrounding “native” plant communities (riparian zones) can be _______ AND ______________ for exotics in grassland ecosystems • ________________ sites in upland areas are very vulnerable to invasions by exotics • On Fort Riley, wheeled and tracked vehicles probably spread seeds—especially when training exercises took place ______________________—with clumps of soil transported from area to area

44. For the prairie ecosystem…. • Climax vegetation type is _____________ vegetation (predominately grass and forbs) • ________________, in “large patches” (assume something > 1-2 m2) not a “good” thing. The more slope, the more rainfall, the more “traffic” the greater the likelihood of invading species becoming established and greater degree of soil erosion