Luc Lagarde, 2012

Thesis:

Invasive <em>Spartina densiflora</em> Brongn. Reduces primary productivity in a northern California salt marsh

Luc's research explored the impact of the invasive dense-flowered cordgrass (Spartina densiflora) on the primary productivity of a Humboldt Bay (California) salt marsh using above and belowground biomass measurements coupled with paired closed-chamber carbon dioxide flux measurements. Although samples dominated by S. densiflora displayed higher aboveground net primary productivity compared to samples dominated by native vegetation, samples dominated by S. densiflora also displayed lower belowground net primary productivity, net primary productivity, and net ecosystem exchange measurements compared to samples dominated by native vegetation; therefore, S. densiflora colonization reduced primary productivity. In plots dominated by S. densiflora, less benthic macroalgae was present and less photosynthetically active radiation reached the substratum. Therefore, increased shading of the sediment surface in plots dominated by S. densiflora contributed to lower net ecosystem exchange measurements. Luc's research contributed to understanding the impact of S. densiflora on the primary productivity of Humboldt Bay salt marsh ecosystems.