1 Report to the Stapledon Memorial Trust September 2012 Species composition and abundance on acid- soil grasslands in the Peak District, and a collection of leaf traits, known to correlate with how plants acquire and utilize resources, of grasses and forbs considered to be now globally distributed species Dr. Jennifer Firn Queensland University of Technology, Science and Engineering Faculty, School of Earth, Enviromental and Biological Science, GPO Box 2434, Brisbane, QLD 4001 Australia jennifer.firn@qut.edu.au Host organization contact: Dr. Carly Stevens, Lecturer in Ecosystem Services University of Lancaster, Lancaster University, LA1 4YQ c.stevens@lancaster.ac.uk Period of fellowship: 26 May 2012 to 14 July 2012 The main purpose of project supported by this fellowship was to measure species composition and abundance at 20 acid soil grasslands across the Peak District, and to collect leaf traits, known to correlate with how plants acquire and utilize resources from a list of 26 grasses and forbs considered to be now globally distributed species (Table 1 and Figure 2 below). Research Report Introduction Invasive exotic plants threaten human health, native biodiversity, and vital ecosystem functions such as primary production, watershed protection and nutrient cycling (Vitousek et al. 1996; Mack et al. 2000; Simberloff et al. 2005). Despite worldwide concern and countless hypotheses proposed to explain invasion, we know little about how or why some plant species become invasive when introduced into a new habitat. For these reasons, the prolific spread and subsequent dominance of exotic species is considered a global epidemic (Millennium Ecosystem Assessment 2005), with ecosystems increasing in similarity across continents (Blackburn et al. 2001; Winter et al. 2009; Firn et al. 2011). As invasive exotic plants have come to dominate large tracts of land, it is widely assumed that they are more abundant at sites in introduced (away) versus native (home) ranges (Hierro et al. 2005). This abundance assumption is based on unsubstantiated hypotheses that ecological or evolutionary dynamics of populations change during the invasion process, and these changes confer an advantage to non- native species in their new ranges
2 (Mitchell et al. 2006). Research efforts have focused on identifying mechanisms that facilitate the success of invasive exotic plants (Shea & Chesson 2002; Levine et al. 2003; Mitchell et al. 2006), but generalizable explanations remain elusive, likely because few studies measure the abundance or traits of invasive plants at both home and away sites, and most centre on individual species as a model system. Recently, I led the first study from a global collaboration called the Nutrient Network to test the abundance assumption about the spread of introduced herbaceous plants in grasslands (Firn et al. 2011). We field- tested 26 plant species commonly found in grasslands in both their native and introduced habitats in 39 locations on four continents. We found that the abundance of a plant in its native habitat in most cases could predict its abundance in an introduced site. The most significant result of the study was that plant species also tended to group together in both their native and introduced areas. We found sites in the United Kingdom and New Zealand shared up to 15 species, creating similar communities in each country. A major limitation to this study was that although the sites were selected by chance without consideration for the species present and their relative abundances, we only sampled three sites in the United Kingdom, 9 sites in New Zealand and 2 in temperate Australia. In order to understand how wide- spread the homogenisation of grasslands is and to develop a better understanding of the mechanisms responsible, we need to sample more sites across regions. In this project, in collaboration with Dr. Stevens, we are extending these initial analyses by measuring species composition and abundance at 20 UK grassland sites to test whether grasslands are indeed increasing in similarity across or homogenizing across these countries. I will sample an equivalent number of sites in New Zealand and the temperate zone of Australia. a) b) Fig. 1: Two of the 20 grassland sites I samples, a) Edale and b) Ramshaw Rocks. The Ramshaw Rocks photo was taken on just one of only four sunny days during my six week stay in the UK. In addition to measuring species composition and abundance at these sites, we also measured several leaf traits known to correlate with how plants acquire and utilise resources, i.e. specific leaf area, leaf nitrogen content and leaf phosphorus content.
3 This project will address longstanding, fundamental questions in the spheres of invasion ecology and plant community ecology. Understanding whether exotic plants are more abundant and whether they grow differently at sites home and away in comparison to resident native species is essential information for: 1) conserving and restoring the most critically endangered biome in Australia and the world, 2) building community assembly rules that distinguish native and invaded communities, 3) analysing trait- based patterns in community assembly to identify processes that structure native versus exotic grasslands, e.g. niche differentiation or habitat filtering, and 4) addressing the controversial and high profile issue of the validity of the native/exotic species dichotomy, and 5) identifying tractable traits to improve the efficacy of biosecurity screening. Outline of Research Conducted Population size and community composition and structure home and away Aim 1: Quantify the abundance of 26 temperate grassland species (that vary in their invasiveness) at sites home and away to test the abundance assumption (population level); and, Aim 2: Analyse patterns of abundance in native and exotic ranges to test contrasting hypotheses of community assembly (community level), e.g. deterministic, stochastic and alternative stable states. Survey design To achieve aim 1 and 2, we measured species composition and abundance at 20 acid soil grassland sites in the Peak District, UK. Next year, I will sample 20 acid grasslands sites within the Banks Peninsular, New Zealand, an area heavily invaded with European herbaceous species. At each of the UK sites with measured a minimum of 5-1 m 2 plots, the number of plots sampled at each site depending on the overall size of the grassland. In each of plot, we recorded species identity and cover. Species cover was visually estimated using a modified Daubenmire method where areal cover is estimated to the nearest 1% (Daubenmire 1959). Outcomes We hypothesize species cover at home sites will be a strong predictor of their abundance away. This outcome will Table 1: List of 26 focal species also included in Firn et al (2011), * indicate species listed as invasive in Weber (2005) Invasive Plant species of the World, CABI Publishing, Oxforeshire, UK Species Life-form Life-history Achillea millefolium Forb Perennial *Agrostis capillaris *Agrostis stolonifera Alopecurus pratensis *Anthoxanthum odoratum *Arrhenatherum elatius Bellis perennis Forb Perennial Cerastium fontanum Forb Perennial *Cirsium arvense Forb Perennial *Cirsium vulgare Forb Annual/Biennial *Dactylis glomerata Festuca rubra *Hieracium pilosella Forb Perennial Holcus lanatus Lolium perenne Myosotis discolor Forb Annual Phleum pratense Plantago lanceolata Forb Perennial *Poa pratensis Poa trivialis Prunella vulgaris Forb Perennial Ranunculus repens Forb Perennial *Rumex acetosella Forb Perennial Taraxacum officinale Forb Perennial Trifolium pratense Forb Perennial Trifolium repens Forb Perennial advance theoretical knowledge by suggesting abundance is a conserved trait within a community. This finding would conform to predictions in the core- satellite population
4 hypothesis proposed by Hanski (1982) that core species are common wherever they occur and satellite species are rare wherever they occur. We also expect to find evidence of the deterministic hypothesis for explaining community assembly with similar species composition and abundance across countries. This outcome will also advance practical knowledge, as it is essential information for understanding and developing better control strategies for invasive plant species in grasslands, and for understanding how to restore ecosystems once degraded. Fig. 2: Eight of the focal species sampled from across the 20 sites in the Peak District. Stage 2: Plant traits home and away Aim 3: Evaluate evidence for several hypotheses proposed to explain introduced species success; and, Aim 4: Test Darwin s naturalisation hypothesis (species are more likely to invade communities that do not contain close relatives) (community level).
5 Trait collection At each site, we collected five young leaves from each of the focal species surveyed. We then measured leaf area using a flat bed scanner and the software ImageJ, dried the leaves and then measured the dry weight to calculate specific leaf area. Under a special quarantine permit, we posted the dried leaves to QUT where leaf nitrogen and phosphorus content analyses will be run. Environmental characteristics To measure abiotic characteristics at the sites, we bulk sampled soil from each plot and under a special quarantine permit shipped dried samples to Queensland University of Technology, Australia for soil nutrient analyses. We will also carefully investigate and record the history of disturbance and management regimes at each of the sites to develop an accurate record of cultivation and grazing history. These data will contribute to our understanding of the importance of the incidental opportunities hypothesis. Outcomes We hypothesize that the dominant species will display innate traits for fast growth, high phenotypic plasticity and qualities that allow them to succeed during and following human disturbances. Subordinate species are more likely to be influence by the abundance of the dominants and low abundant species developed traits, because of being released from enemies or evolution of increased competitive ability. This experimental design will also allow us to assess interactions between competition for resources and the enemy release hypothesis (Blumenthal 2005). Experience gained As an early career researcher the experience gained while conducting this project was invaluable. I built a strong working relationship with Dr. Carly Stevens and learned a tremendous amount from working with her and her students. Dr. Stevens and I have plans to apply for funding for additional projects to keep extending our investigations of herbaceous species with global ranges. I also had the opportunity to interact with the large and dynamic lab group of Prof. Richard Bardgett. I learned about new techniques in soil microbial analyses and about new research linking aboveground traits of plants to belowground interactions. I had a chance to meet with other leading researchers at the Lancaster Environment Centre, and I found these interactions inspiring. I also had the opportunity to sample in beautiful and iconic grasslands in the ecological literature that I had only read about, e.g. Mam Tor, Edale, Ramshaw and Longshaw. Visiting and working for days in these beautiful grasslands was inspiring. It also gave me a chance to really think about and better understand the British agricultural practices that have been introduced across continents and have dramatically altered natural landscapes. This helped me gain a better understanding of the historical linkages of the highly modified Australian landscape.
6 Plans for follow up There are a number of activities that I will follow- up in the coming year: Conduct a similar survey of 20 acid soil grasslands within the Banks Peninsular New Zealand. If I procure additional funding I also plan to sample within Switzerland and Australia; If unsuccessful with this further grant application I will use the data collected in the UK as pilot data and re- submit the application. Finish soil and leaf tissue nutrient analyses on the UK samples collected. Analyse data collected with the aim of producing a publication in collaboration with Dr Stevens. References Blackburn T.M., Gaston K.J. & Duncan R.P. (2001). Population density and geographical range size in the introduced and native passerine faunas of New Zealand. Diversity and Distributions, 7, 108-121. Blumenthal D. (2005). Interrelated causes of plant invasion. Science, 310, 243-244. Daubenmire R. (1959). A canopy- coverage method of vegetation analysis. Northwest Science, 33, 43-64. Firn J., Moore J.L., MacDougall A.S., Borer E.T., Seabloom E.W., HilleRisLambers J., Harpole W.S., Cleland E.E., Brown C.S., Knops J.M.H., Prober S.M., Pyke D.A., Farrell K.A., Bakker J.D., O'Halloran L.R., Adler P.B., Collins S.L., D'Antonio C.M., Crawley M.J., Wolkovich E.M., La Pierre K.J., Melbourne B.A., Hautier Y., Morgan J.M., Leakey A.D.B., Kay A., McCulley R., Davies K.F., Stevens C.J., Chu C.- J., Holl K.D., Klein J.A., Fay P.A., Hagenah N., Kirkman K.P. & Buckley Y.M. (2011). Abundance of introduced species at home predicts abundance away in herbaceous communities. Ecology Letters, 14, 274-281. Hanski I. (1982). Dynamics of regional distribution: the core and satelite species hypothesis. Oikos, 38, 210-221. Hierro J.L., Maron J.L. & Callaway R.M. (2005). A biogeographical approach to plant invasions: the importance of studying exotics in their introduced and native range. Journal of Ecology, 93, 5-15. Levine J.M., Vila M., D'Antonio C.M., Dukes J.S., Grigulis K. & Lavorel S. (2003). Mechanisms underlying the impacts of exotic plant invasions. Proceedings of the Royal Society B: Biological Sciences, 270, 775-781. Mack R.N., Simberloff D., Lonsdale W.M., Evans H., Clout M. & Bazzaz F.A. (2000). Biotic invasions: causes, epidemiology, global consequences, and control. Ecological Applications, 10, 689-710. Millennium Ecosystem Assessment (2005). Ecosystems and Human Well- being: Biodiversity Synthesis. United Nations. Mitchell C.E., Agrawal A.A., Bever J.D., Gilbert G.S., Hufbauer R.A., Klironomos J.N., Maron J.L., Morris W.F., Parker I.M., Power A.G., Seabloom E.W., Torchin M.E. & Vazquez D.P. (2006). Biotic interaction and plant invasions. Ecology Letters, 9, 726-740. Shea K. & Chesson P. (2002). Community ecology theory as a framework for biological invasions. Trends in Ecology & Evolution, 17, 170-176. Simberloff D., Parker I.M. & Windle P.N. (2005). Introduced species policy, management, and future research needs. Frontiers in Ecology and the Environment, 3, 12-20. Vitousek P.M., D'Antonio C.M., Loope L.L. & Westbrooks R. (1996). Biological invasions as global environmental change. American Scientist, 84, 468-479. Winter M., Schweiger O., Klotz S., Nentwig W., Andriopoulos P., Arianoutsou M., Basnou C., Delipetrou P., Didziulis V., Hejda M., Hulme P.E., Lambdom P.W., Pergl J., Pysek P., Roy D.B. & Kuhn I. (2009). Plant extinctions and introductions lead to phylogenetic and taxonomic homogenization of the European flora. Proceedings of the National Academy of Science, 106, 21721-21725.