Plant Community Succession on Drying Lakes in the Yukon Flats, Alaska

Plant succession is often studied by observing how plant communities colonize the landscape and subsequently change over time. In the Yukon Flats National Wildlife Refuge, Alaska, time-series imagery has shown reductions in the total surface area and number of closed-basin lakes. We investigated how changes in lake area over time relate to colonization and succession on lake basins by terrestrial plant communities in the Yukon Flats. However, the potential successional pathway is unclear and lake area reductions could follow a hydrosere succession model, a meso- or xerosere succession model, or a secondary succession model. Furthermore, we expect specific suites of plants species and edaphic factors to be associated with each of the models of succession. The objectives of this study are:

• Describe the plant communities and environmental variables to determine pathways of vegetation change;
• Investigate how rapidly plant communities are recruiting into lake margins.

Fourteen lakes were selected based on decreasing lake area between the years 1985 and 2009. Plant functional group abundance and soil moisture were sampled along a toposequence from the existing lake edge to the historic lake edge. A gradient of soil moisture was identified that decreases with increasing distance from the current lake edge. Vegetation types were identified from differences in dominant functional group abundances along the soil moisture gradient: wetland graminoid > mesic graminoid > tall shrub > forest, with sharp transitions between types. Plant species cover and soils were described in each type. Preliminary results indicate a relationship between soil moisture and vegetation; as the soil decreases in moisture, there are significant shifts in vegetation type. The most notable differences in soil moisture are between graminoid and woody vegetation types which could mean that soil moisture may be decreased by the colonization of functional types with high demand for water resources. Thus, driving changes in soil moisture regimes as they colonize the lake margins. Further analyses will investigate plant species composition among lakes and vegetation types and changes associated with shrinking lakes over time using remote sensing techniques. This study will provide information on changes in vegetation due to shrinking lakes and how this may influence wildlife habitats and human subsistence users.