I am a plant ecologist who works primarily on plant-animal interactions, usually at the intersection of population, community, and ecosystem ecology. While the questions and the systems I and members of my lab work on are diverse, our work usually involves both direct and indirect interactions between several species, and between those species and their physical environment. We combine field work with greenhouse experiments, historical datasets, and some modeling.

Current and Recent Research Themes:

Note: some projects include several of these themes.

Invasive plants in Interior Alaska

Non-native plant species have been expanding rapidly across the state of Alaska, likely aided by higher winter temperatures and long growing seasons, increased levels of human traffic, and more frequent and larger wildfires. Several projects evaluate the impacts of changes in abundance of introduced plant species on plant communities:

Are Alaskan Pollinators Abandoning Native Berries for an Exotic Clover? Implications for Invasive Plant Management on Fruit Production. In this project we evaluate whether and how the expansion of non-native Melilotus alba across the state of Alaska affects pollination and fruit set of two berry species: Vaccinium vitis-idaea (bog cranberry) and Vaccinium uliginosum (bog blueberry). This is a collaboration with Matt Carlson (UA Anchorage).

Non-native Melilotus alba (plant with white flowers) in recently burned forest (with grad student Katie Villano Spellman); tagging cranberries; a prolifically flowering cranberry; testing germination of non-natives in the soil from different habitats

What factors affect the success of invasive plants in natural environments? Recently burned forest is likely to be particularly susceptible to invasion, and forest fires are increasing in both frequency and extent. Projects associated with this question include:

§ Greenhouse experiments conducted by Katie Villano (former MS student) to evaluate soil and ground cover factors that best explained germination and growth of three introduced plant species, and by Luke Ponchione (former undergraduate student) to evaluate the role of moss species in facilitating or retarding the germination of introduced plant species.

§ A survey of burned habitat along four roads in interior Alaska to establish a baseline for the distribution and abundance of non-native plants. Click here to link to the technical report that resulted from this.

Climate change in northern environments: direct and indirect effects on plant communities

Arctic and subarctic communities are subjected to some of the fastest rates of climate change on the planet. To what extent are impacts on plant communities driven by direct effects (e.g., changes in temperature and precipitation) and to what extent are they driven by changes in interactions with other organisms, such as herbivores or pollinators? How important are changes in winter vs. summer conditions? Several projects fall under this theme:

· Cold Sick Plant Project: This is a collaboration between my lab and that of Bitty Roy (U. of Oregon). We are investigating changes in attack rates by plant herbivores and pathogens on understory species in boreal forest to answer the question: does environmental variation affect herbivores and pathogens primarily directly, or primarily through changes in plant qualities? See Mulder et al. 2008.

· Pathogens on alders: Jenny Rohrs-Richey (Ph.D. 2011) evaluated the role of drought stress in affecting the susceptibility of alder (Alnus fruticosa) to a canker (Valsa melanodiscus). For more, see Rohrs-Richey et al. 2011.

Working in the rain; Jenny Rorhs-Richey (PhD student) downloading dataloggers; a plant pathogen on cranberry; a leaf roller on alder; Christa at a site destroyed by a forest fire; habitat degradation from goose grubbing and flooding at La Pérouse Bay

Plant phenology, climate change, and geese in a subarctic saltmarsh: this is a new collaboration with R.F. Rockwell (American Museum of Natural History), and David Koons and Lise Aubry (Utah State). We are evaluating how different aspects of climate change affect plant phenology, whether we can predict how different plant species will respond, and how shifts in plant phenology will affect snow goose populations. See Hudson Bay Project for more information on this habitat.

Other publications on this theme include Wipf et al. 2006 and Rixen and Mulder 2009.

Impacts of seabirds on plant communities.

Seabird islands are islands that have high populations of seabirds. They are often remote and in many cases lack the predators found on the mainland or islands closer to the mainland. Seabird islands occur worldwide and they are of high conservation value because they often have very high levels of endemism and may serve as “safe havens” for species that are rare or no longer present on the mainland. However, many of the islands have been invaded by non-native predators such as rats, cats, and foxes, with devastating effects for native bird, reptile and mammal populations. Restoration of hundreds of islands has focused on the removal of these predators, but little attention has been paid to other aspects of restoration beyond monitoring seabird populations.

Aorangaia island (Poor Knights, New Zealand); moving carefully across burrow-riddled ground; close-up of seabird burrows; decomposing leaves marked while on the tree; graduate students Mel Durrett and Nikki Grant-Hoffman on New Zealand islands

SEAPRE (Seabird Islands and Introduced Predators: Impacts of Presence and Eradication on Island Function): I was the Principal Coordinator of this Research Coordination Network, which brought together people from across the world for cross-system comparisons and synthesis of the impacts of seabirds and introduced seabird predators on island ecology, with the further aim of improving restoration plans for islands on which these introduced predators have been or are being eradicated. The main product from this network was a book: Seabird Islands: Ecology, Invasion, and Restoration, published by Oxford University Press in 2011.

RASP (Rats and Islands Project). In this project, run in collaboration with Manaaki Whenua - Landcare Research and Department of Conservation (both of New Zealand) examined the effects of invasive rats on vegetation and soils, both directly (e.g. through changes in seed or seedling consumption) and indirectly (by reducing or eradicating seabird populations). For more details, see Fukami et al. 2006, Wardle et al. 2007, Mulder et al. 2009, Towns et al. 2009, Bellingham et al. 2010, Grant-Hoffman et al. 2010a, Grant-Hoffman et al. 2010b.

Additional information:

Members of the Mulder lab Publications Teaching Public Outreach Mulder c.v. (as pdf file)