James Sowerwine
Graduate student, Department of Biological Sciences,University of Alaska, Anchorage
Email: james.sowerwine at gmail dot com.
Current research:
I am currently investigating the effects of the invading biennial legume Melilotus alba (white sweet clover; though the plant actually falls in the pea family) on the native Alaskan willow Salix alaxensis var. longistylis (felt leaf willow) and other plants, with implication for population maintenance for moose in South-Central and Interior Alaska.
Feral populations of Melilotus alba were introduced at least 75 years ago to Alaska via the USDA and Canadian Agricultural Research Station networks. Probable locations of introduction included the Delta Junction ARS station near Fairbanks, the Palmer ARS station north of Anchorage, and a defunct site adjacent to the remote Stikine watershed in British Colombia. All introductions would have been made via experiments conducted to locate a cold tolerant green forage plant, and subsequent plantings by regional farmers. Plants have spread via Alaskan road and river networks in the intervening years, and appear to be expanding in range at a much faster rate in response to recent warmer, damper fall seasons. Similiar patterns have been observed in the Yukon Territory, Canada, to the east of Alaska.
Melilotus alba is found primarily on roadsides, exposed gravel and cobble bars in rivers, and in other disturbed areas. Current distributions suggest that there is a high probability of the species becoming established within all river drainage in South-Central and Interior Alaska in future decades, where the plant can persist in disturbed habitats created by seasonal flooding. Melilotus alba does not appear to survive in competition with second-tier colonizers such as alders. Despite this reassuring note, potential exists for M. alba to alter native communities during the first years of succession, or in other less obvious ways. To evaluate the disruptive potential posed by this invader, I am investigating the effects of M. alba on native Alaskan species. In particular, I am interested in learning more about effects of competition on native seedlings, and effects M. alba may have on prominent native riverine species such as willow. Unforeseen effects, such as changes in chemical composition in native plants in response to the presence of a novel invader, would alter the forage quality of these species and potentially negatively impact native browsers such as moose. Initial evidence suggests that populations of boreal browsers such as moose are controlled by the availability of winter forage; a decrease in forage quality in native willow has the potential to decrease the size of populations of moose in Alaska.
I have set up several long-term experiments to better evaluate these questions. My experiments seek to:
1. Evaluate the disruptive effects of M. alba on cold-region adapted native seedlings. To this end, I have selected the native bunchgrass Festuca rubra spp. rubra (arctic red fescue) to grow in a two-plant competition experiment. 1000 experimental plots of different densities and mixtures will be started from seed and grown through the seedling life-stage to assess inter-specific competition at this critical life-stage. Previous work by Blaine Spellman at the University of Alaska, Fairbanks has shown a decrease in recruitment and survival of native seedlings grown in the field with M. alba, suggesting the need for further work to evaluate the extent of interference by M. alba on other native plants.
2. Evaluate relative differences across spatially isolated populations of M. alba collected from five different locations in Alaska. Population locations sampled include the (1) The Stikine River delta in central South-East Alaska, (2) The lower Matanuska River delta in South-Central Alaska, (3) The Nenana river at Healy, Alaska (4) From within the city of Fairbanks, Alaska and (5) From a post-fire site adjacent to the Dalton Highway in the Ray River Valley. If introductions were made separately (and / or with different agricultural cultivars), populations may display different competitive abilities and subsequently have different disruptive effects.
3. Evaluate the causal effects of M. alba on the biochemistry of a common native willow species. Willow cuttings will be grown from 2007 to 2008, then out-planted during summer 2008 together with M. alba seeds and roots (M. alba lives for two years, sprouting from roots during it's second summer of growth). Experimental willows will be analyzed following the end of the summer with the following test:
a. Stable isotope analysis, to investigate whether M. alba directly alters native willow biochemistry
b. Total phenolics analysis, to investigate whether M. alba indirectly alters native willow biochemistry
c. ASE tannin analysis, to investigate whether M. alba alters a common and important control of animal forage quality.
With these results, I expect to be able to make a qualitative prediction about the potential for M. alba to impact Alaskan moose populations in South-Central and Interior Alaska. I will also learn more about M. alba's impacts on native seedling communites.
Acknowledgements:
The AK EPSCoR program has provided a one year fellowship in support of this work. The UAA engineering department has lent use of vital greenhouse space, and Jeff Conn, Katie Villiano, and the kind staff at the University of Fairbanks Agricultural Extension Service have provided seed collections.
Links:
The University of Alaska, Anchorage Department of Biological Sciences
Last updated 12/20/2007