Department of Biology

Program

Evolution, Ecology & Behavior

Research Area

Ecology

Education

Ph.D., Cornell University, 2005
Postdoctoral Fellow, Duke University, 2005-2008

Research Description

My research broadly seeks to quantify and better understand how plants and soil microbes influence energy flow and nutrient cycling in terrestrial ecosystems in the wake of human-accelerated environmental change.  Of particular interest is the degree to which plant-microbial interactions in soils influence feedbacks to regional and global change through their effects on ecosystem carbon storage and nitrogen and phosphorus retention. I use a complimentary suite of approaches that integrate field observations with novel techniques (e.g. stable and radioactive isotopes) and controlled environmental systems (e.g. growth chambers, FACE sites) to address questions that intersect plant physiological ecology and soil microbial ecology in an ecosystem context. 

There are three broad themes to my research:

Coupling of plant and microbial productivity.  In terrestrial ecosystems, plants and soil microbes are highly interdependent as plants rely on microbes to transform nutrients to an “available” form, and microbes rely on plants to provide reduced C for metabolism.  Despite the apparent simplicity of the interaction, there are significant gaps in our understanding of factors that mediate the coupling of carbon and nutrient cycles.  It is often assumed leaf litter quality controls nutrients availability in soils.  However, plants also release appreciable amounts of carbon from roots, and these inputs may have a disproportionate effect on nutrient availability in the zone of soil adjacent to roots (i.e. the rhizosphere).  A theme of my research is to better understand the role of roots in influencing the coupling of plant and microbial productivity through their effects on nutrient cycling.  

Species effects on nutrient cycling.  A fundamental question in ecology is the role of species in influencing ecosystem processes.  This question has become increasingly important given the loss of species, increases in non-indigenous species, and predicted shifts in the distribution and abundance of species owing to global climate change.  In forests, most research has focused on tree species effects on ecosystem processes through differences in aboveground traits, with little consideration of species differences in nutrient acquisition strategies.  My research seeks to improve upon our understanding of species effects on nutrient cycling by examining differences in nutrient acquisition strategies among tree species, with a focus on root-induced alterations of rhizosphere bacteria and fungi.  Some key questions include:

Plant-soil-microbial feedbacks to global change.  Interactions between plants, soils, and microbes mediate the flow of energy and nutrients through ecosystems with the potential to feed-back to primary production through effects on carbon sequestration in biomass and soils.  This has led to speculation that terrestrial ecosystems – particularly forests – may mitigate elevated levels of atmospheric CO2 through increases in productivity.  However, the persistence of forests as carbon sinks over the long-term will likely depend on the degree to which trees increase access to soil nutrients.  A broad theme of my research is to quantify the degree to which plant-soil-microbial interactions mediate ecosystem-responses to global environmental change.

Select Publications

Phillips, R.P., E.S. Bernhardt and W.H. Schlesinger. 2009. Elevated CO2 increases root exudation from loblolly pine (Pinus taeda L.) seedlings as an N-mediated response. Tree Physiology 29:1513-1523

Kiser, M.R., Reid, C.D. Crowell, A.S., Phillips, R.P., and C.R. Howell. 2008. Exploring the transport of plant metabolites using positron emitting radiotracers. HFSP Journal 2: 189-204.

Phillips, R.P., Erlitz, Y., Bier, R., and E.S. Bernhardt. 2008. A new approach for capturing soluble root exudates in forest soils. Functional Ecology 22: 990-999

Shen, W., Jenerette, G.D., Hui, D., Phillips, R.P. and H. Ren. 2008. Effects of changing precipitation regimes on dryland soil respiration and C pool dynamics at rainfall event, seasonal and interannual scales. Journal of Geophysical Research – Biogeosciences 113, G03024, doi:10.1029/2008JG000685

Phillips, R.P. and T.J. Fahey. 2008. Fertilization suppresses rhizosphere effects in northern hardwood forest soils. Soil Science Society of America Journal 72: 453-461

Phillips, R.P.  2007.  Towards a rhizo-centric view of plant-microbial feedbacks under elevated atmospheric CO2.  New Phytologist 173: 664-667

Phillips, R.P. and T.J. Fahey.  2007.  Fertilization effects on fine root biomass, rhizosphere microbes and respiratory fluxes in hardwood forest soils.  New Phytologist 176: 655-664

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