Species diversity and aquatic ecosystem function – 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. We are expanding on this work to look at the implications of riparian species diversity across different bioregions of the lower 48.
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.
Genotypic variation and aquatic ecosystem function – At a finer level, we have compared decomposition rates, macroinvertebrate colonization and fungal biomass on different Populus genotypes in the stream. The majority of this work has been done in the Southwest, and we are interested in expanding this research into ecosystems that have higher species diversity.
Salmon carcass influence on diverse leaf litter decomposition – Welles Bretherton’s work examined the interaction between salmon carcass presence and leaf litter diversity. He has interesting results that show the presence of salmon influences how different leaf species interact in mixture (poster presentation at ESA in August, 2009, see pubs).
Fungal endophyte infection decelerates leaf litter decomposition – Katherine Halstead (Evergreen undergraduate) has undertaken an experiment investigating the influence of the fungal endophyte Rhytisma punctatum on big leaf maple (Acer macrophyllum) decomposition. Initial results show a significant deceleration of leaf litter decomposition when the fungal pathogen is present.
Salmon carcass influences on genotype-specific leaf litter decomposition – Mara Denny (Evergreen undergraduate) has undertaken an experiment on the Elwha River in collaboration with NOAA fisheries looking at how salmon carcass presence interacts with the genetic influence of leaf litter on stream function.
Geographic-genetic surveys & GM-poplars – We have undertaken efforts to explore the genetic variation in various species of Populus. We are interested in comparing this natural variation to the novel variation in genetically modified cottonwoods.
Effects of terrestrial herbivores on aquatic ecosystems and communities – A galling aphid (Pemphigus betae) on cottonwood leaves induces phytochemical changes in litter quality. These changes have been shown to retard decomposition terrestrially, and we show a similar effect aquatically. In addition, the induced condensed tannins in galled leaves lead to a decrease in fungal biomass and a change in macroinvertebrate community structure.
Community and Ecosystem Genetics – A review of major advances in the fields of community and ecosystem genetics in the journal Nature Reviews Genetics.
Community Evolution – An NSF Frontiers in Biological Research (FIBR) grant was awarded to our research group to study the potential for community evolution in riparian communities dominated by foundations species of cottonwoods. We are in the second year for funding (2004-2009), and have published over 20 papers as part of this research program. Collaborating institutions on this project include: Northern Arizona University, University of Wisconsin-Madison, University of Tasmania, Oak Ridge National Laboratories and the University of Alberta.
Cottonwood Ecology Group – In collaboration with the Cottonwood Ecology Group, the Bureau of Reclamation and the Utah Dept. of Natural Resources, we have restored over 60 acres of riparian habitat in Arizona and Utah. The restoration plantings are genetically diverse, and function as large-scale experiments in community and ecosystem genetics.
Trophic dynamics in lakes with the Tahoe-Baikal Institute – As part of a collaborative project with the Tahoe-Baikal Institute, UC Davis and the University of Nevada-Reno, we have investigated trophic dynamics in large lakes and the introduction of exotic fish species.