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Freshwater Ecology Lab at The Evergreen State College


Salmon carcasses influence diverse leaf litter decomposition - Welles Bretherton (Evergreen undergraduate) took the lead on a study examining the interaction between salmon carcass presence and leaf litter species diversity (Bretherton et al. 2011). His interesting results in the Canadian Journal of Fisheries and Aquatic Sciences show the presence of salmon carcasses influences how different leaf species interact in mixtures.

A more recent study shows that mixtures of litter from several Populus genotypes interact in novel ways with salmon carcasses. LeRoy et al. (2016) shows that fungal biomass is much higher on litter mixtures, and even more so when salmon carcasses are present.

Rapid stream development in 35 years since Mt St Helens eruption- In collaboration with Shannon Claeson (USFS), we have surveyed four newly formed streams on the Pumice Plain post-eruption. We have found that algal community structure differs widely among streams and could signal divergent evolutionary trajectories.

Influence of major dam removal on in-river litter processing- In collaboration with Sarah Morley (NOAA Fisheries) and Jeff Duda (USGS), we installed over 300 leaf litter bags in the Elwha watershed to explore the influence of the historic dam removals on this crucial ecosystem function.

Fungal endophyte influences leaf litter decomposition - Undergraduates Kate Halstead and Margaret Pryor both contributed to this paper in Freshwater Biology which shows the presence of a fungal endophyte significantly slows leaf litter decomposition (LeRoy et al. 2011). This fungal endophyte infects about 70% of all bigleaf maple leaves and could be affecting decomposition across large spatial scales. New research on this topic includes microbial metagenomics data for both litter colonizing fungi and bacteria!

Plant genes link forests and streams - Using Populus (cottonwood or poplar) as a model system, we examined the effects of hybridization between species on aquatic decomposition and macroinvertebrate community structure (LeRoy et al. 2006).

At a finer level, we have compared decomposition rates, macroinvertebrate colonization and fungal biomass on different Populus genotypes in the stream (LeRoy et al. 2007). Other studies have shown that plant genes interact with environmental factors to influence litter quality and in-stream decomposition for aspen (LeRoy et al. 2012). A largescale mesocosm study showed that tree genes can influence whole-pond communities (Crutsinger et al. 2014). A very recent article shows that tree genetics strongly influences tree productivity, but that intraspecific richness is not a strong driver (Fischer et al. 2016). Many reviews on genes-to-ecosystems topics highlight the strong organizing power of genes (Whitham et al. 2006, Schweitzer et al. 2008, Bailey et al. 2009).

Species diversity and aquatic ecosystem function - In one early study using native riparian trees in the southwestern U.S. (Fraxinus pennsylvanica, Quercus gambelii, Alnus oblongifolia, Populus fremontii and Platanus wrightii) we examined the effects of leaf litter diversity on aquatic decomposition and macroinvertebrate community structure (LeRoy & Marks 2006). We have since been working with a variety of collaborators to examine biodiversity and ecosystem function (B-EF) relationships in brown food webs in streams. A meta-analysis in Ecology shows that synergistic (faster than expected) decomposition is more common (Lecerf et al. 2011). Another paper in Regulated Rivers highlights opportunities for future research in aquatic B-EF studies (Kominoski et al. 2010).

Ecosystem influences of genetic modifications in poplars - Petter Axelsson and Joakim Hjalten at the Swedish University of Agricultural Sciences took the lead in investigating the effects of genetically modified lignin pathways in Populus tremula x Populus alba hybrids. We found that certain modifications can be transferred across ecosystem boundaries to influence stream ecosystems. In particular, litter decomposition was influenced by lignin-modification (Axelsson et al. 2010), aquatic insects are influenced by Bt-toxin modifications (Axelsson et al. 2011), and leaf damage was higher for wild plants compared to Bt-toxin modified aspen (Axelsson et al. 2012).

Endangered species recovery and science outreach in prisons - Since 2008 we have been rearing WA State endangered Oregon Spotted Frog, Federally endangered Taylor's Checkerspot butterfly and rare and endangered prairie plants in prison through the Sustainability in Prisons Project - a partnership between The Evergreen State College and the WA Dept. of Corrections. See a recent article in Science about our outreach (LeRoy et al. 2015).