Education
Postdoc, 2001, Stanford University
Ph.D. 2000, Cornell University
M.S. 1994, University of Washington
B.S. 1990, University of Pennsylvania
Specialty
Forest biogeochemistry and ecosystem studies, watershed science, riparian forests, global change, nutrient cycling, forest soil fertility, stable isotopes
A complete list of publications is available on Steve's google scholar page.
Biological nitrogen fixation (BNF) is a critical biogeochemical process that converts inert atmospheric N2 gas into biologically usable forms of the essential nutrient nitrogen. A variety of free-living and symbiotic organisms carry out BNF, and in most regions worldwide, BNF is the largest source of nitrogen that fuels terrestrial ecosystems. As a result, BNF has far reaching effects on...
Research in our laboratory centers on the ecology and biogeochemistry of forest ecosystems, as well as grassland and riparian systems. We examine how factors such as natural and human disturbances, climate and climate change, succession, and soil fertility shape ecosystem biogeochemistry - and the reciprocal effect of biogeochemical cycles on these and other factors.
Riparian vegetation is an often ignored yet critical source of nutrition for riparian food webs. Many food webs are supported at their base by the breakdown and incorporation of leaf litter into fungi, insects, etc. In headwater streams, riparian leaf litter inputs provide essential subsidies that fuel in-stream productivity, in addition to subsidizing food chains of terrestrial riparian...
This research theme facilitates the sound management and restoration of Pacific Northwest Douglas-fir forests, as well as to refine broader-scale predictions of how temperate forests will function in an increasingly nitrogen-rich world.
This research theme examines the impacts of prescribed fire on plant productivity, soil physical, chemical, and biological characteristics, and nutrient leaching. Results from this research will enable improved decision-making of how to manage fire-prone forests to maintain long-term forest fertility and productivity, especially across wide climate gradients characteristic of the Pacific...
This research theme coalesces studies of old-growth temperate forests in several major thematic areas including landscape and ecosystem controls on watershed nutrient export, wildfire disturbance legacies on biogeochemical cycling, and the imprint of tree species on soil nutrients in old-growth forests.
This research theme advance fundamental understanding of climate-biogeochemistry interactions, with wide applicability to virtually all terrestrial ecosystems.
Nitrogen deposition is altering forest dynamics, terrestrial carbon storage, and biodiversity. However, our ability to forecast how different tree species will respond to N deposition, especially key response thresholds, is limited by a lack of synthesis across spatial scales and research approaches. To develop our best understanding of N deposition impact on tree growth and survival, we will...
Coastal margins are important areas of materials flux that link terrestrial and marine ecosystems. Consequently, climate-mediated changes to coastal terrestrial ecosystems and hydrologic regimes have high potential to influence nearshore ocean chemistry and food web dynamics. Research from tightly coupled, high-flux coastal ecosystems can advance...
Bidlack, Allison L.; Bisbing, Sarah; Buma, Brian; Diefenderfer, Heida; Fellman, Jason; Floyd, William; Giesbrecht, Ian; Lally, Amritpal; Lertzman, Ken; Perakis, Steven; Butman, David; D'Amore, David; Fleming, Sean W.; Hood, Eran W.; Hunt, Brianna K.; Kiffney, Peter; McNicol, Gavin; Menounos, Brian; Tank, Suzanne E. Symbiotic nitrogen- (N) fixing trees can influence multiple biogeochemical cycles by fixing atmospheric N, which drives net primary productivity and soil carbon (C) and N accumulation, as well as by mobilizing soil phosphorus (P) and other nutrients to support growth and metabolism. The soil micronutrient molybdenum (Mo) is essential to N-fixation...
Dynarski, Katherine A; Pett-Ridge, Julie C.; Perakis, Steven PremiseDetermining which traits characterize strategies of coexisting species is important to developing trait‐based models of plant communities. First, global dimensions may not exist locally. Second, the degree to which traits and trait spectra constitute independent dimensions of functional variation at various scales continues to be refined....
Burton, Julia I.; Perakis, Steven; Brooks, J. Renee; Puettmann, Klaus J. Quantifying human impacts on the nitrogen (N) cycle and investigating natural ecosystem N cycling depend on the magnitude of inputs from natural biological nitrogen fixation (BNF). Here, we present two bottom‐up approaches to quantify tree‐based symbiotic BNF based on forest inventory data across the coterminous United States and SE Alaska. For...
Staccone, Anika; Liao, Wenying; Perakis, Steven; Compton, Jana; Clark, Christopher L.; Menge, Duncan Fire activity is changing dramatically across the globe, with uncertain effects on ecosystem processes, especially below‐ground. Fire‐driven losses of soil carbon (C) are often assumed to occur primarily in the upper soil layers because the repeated combustion of above‐ground biomass limits organic matter inputs into surface soil. However, C...
Pellegrini, Adam; McLauchlan, Kendra K; Hobbie, Sarah E; Mack, Michelle C.; Marcotte, Abbey L; Nelson, David M.; Perakis, Steven; Reich, Peter B.; Whittinghill, Kyle Pacific salmon acquire most of their biomass in the ocean before returning to spawn and die in coastal streams and lakes, thus providing subsidies of marine‐derived nitrogen (MDN) to freshwater and terrestrial ecosystems. Recent declines in salmon abundance have raised questions of whether managers should mitigate for losses of salmon MDN...
Feddern, Megan; Holtgrieve, Gordon W.; Perakis, Steven; Hart, Julia A.; Ro, Hyejoo; Quinn, Tom Atmospheric deposition of nitrogen (N) influences forest demographics and carbon (C) uptake through multiple mechanisms that vary among tree species. Prior studies have estimated the effects of atmospheric N deposition on temperate forests by leveraging forest inventory measurements across regional gradients in deposition. However, in the United...
Horn, Kevin J; Thomas, R Quinn; Clark, Christopher M.; Pardo, Linda H; Fenn, Mark E.; Lawrence, Gregory B.; Perakis, Steven; Smithwick, Erica A.H.; Baldwin, Doug; Braun, Sabine; Nordin, Annika; Perry, Charles H.; Phelan, Jennifer N; Schaberg, Paul G.; St Clair, Samuel B; Warby, Richard; Watmough, Shaun A. Organic matter is of emerging interest as a control on molybdenum (Mo) biogeochemistry, and information on isotope fractionation during adsorption to organic matter can improve interpretations of Mo isotope variations in natural settings. Molybdenum isotope fractionation was investigated during adsorption onto insolubilized humic acid (IHA), a...
King, Elizabeth K.; Perakis, Steven; Pett-Ridge, Julie C. Forests cover 30% of the terrestrial Earth surface and are a major component of the global carbon (C) cycle. Humans have doubled the amount of global reactive nitrogen (N), increasing deposition of N onto forests worldwide. However, other global changes—especially climate change and elevated atmospheric carbon dioxide concentrations—are increasing...
McLauchlan, Kendra K.; Gerhart, Laci M.; Battles, John J.; Craine, Joseph M.; Elmore, Andrew J.; Higuera, Phil E.; Mack, Michelle M; McNeil, Brendan E.; Nelson, David M.; Pederson, Neil; Perakis, Steven Trait-based models of ecological communities typically assume intraspecific variation in functional traits is not important, though such variation can change species trait rankings along gradients in resources and environmental conditions, and thus influence community structure and function.We examined the degree of intraspecific relative to...
Burton, Julia I.; Perakis, Steven; McKenzie, Sean C.; Lawrence, Caitlin E.; Puettmann, Klaus J. Multiple nutrient cycles regulate biological nitrogen (N) fixation in forests, yet long-term feedbacks between N-fixation and coupled element cycles remain largely unexplored. We examined soil nutrients and heterotrophic N-fixation across a gradient of 24 temperate conifer forests shaped by legacies of symbiotic N-fixing trees. We observed...
Perakis, Steven; Pett-Ridge, Julie C.; Catricala, Christina E. We review the mechanisms of deleterious nitrogen (N) deposition impacts on temperate forests, with a particular focus on trees and lichens. Elevated anthropogenic N deposition to forests has varied effects on individual organisms depending on characteristics both of the N inputs (form, timing, amount) and of the organisms (ecology, physiology)...
Carter, Therese S.; Clark, Christopher L.; Fenn, Mark E.; Jovan, Sarah E.; Perakis, Steven; Riddell, Jennifer; Schaberg, Paul G.; Greaver, Tara; Hastings, Meredith
There is a black box hidden beneath the forests of the Pacific Northwest, guarding the secrets to why the trees grow so large! The black box is soil, which harbors immense biological diversity and controls the release of water and nutrients that support the life above ground. Join us as Sue Powell interviews USGS ecologist Steve Perakis and discusses his research about the
Biological nitrogen fixation is a large source of nitrogen to soils and watersheds, and fuels carbon uptake in terrestrial ecosystems worldwide.
Coastal margins at the interface between land and ocean are important areas of materials flux – such as carbon and nutrients transported in river discharge – that link terrestrial and marine ecosystems. Climate is central to these fluxes, which in turn influence nearshore ocean chemistry and food web dynamics.
Symbiotic nitrogen-fixing trees enhance forest fertility by increasing nitrogen and organic matter in soil.
Plant traits, such as leaf size and rooting depth, can affect plant performance and hence, how plants might respond to environmental change. Plant traits can be integrated, or correlated, with a particular functional plant response, such as how plants use water efficiently. Alternatively, plants can differentiate along multiple trait dimensions.
Symbiotic nitrogen-fixing trees influence soil fertility and provide a large background source of nitrogen in watersheds.
Fire activity is changing worldwide, with unclear effects on ecosystem carbon storage. Fire effects on carbon storage are better known for vegetation than for soil, and fire effects on deep soil carbon are especially uncertain.
Pacific salmon transport large amounts of marine nutrients to freshwater and forest ecosystems when they migrate from the ocean, spawn, and die.
There is scientific controversy about whether nitrogen deposition increases forest carbon sequestration. All tree species do not exhibit the same response to nitrogen and responses may be complicated by interactions with biotic and other abiotic factors such as sulfur deposition.