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Patrick J. Mulholland

Patrick J. Mulholland

Nutrient Biogeochemistry Group
Environmental Sciences Division
Oak Ridge National Laboratory
Oak Ridge, TN 37831-6036
Phone:  (865)574-7304
Fax:  (865)576-8543

mulhollandpj@ornl.gov

I am an aquatic ecologist in the Environmental Sciences Division of Oak Ridge National Laboratory in Oak Ridge, Tennessee. On this page you can find information about my educational background, research interests, current projects, recent publications, and useful web links.

Background/Education

  • Ph.D., Environmental Biology, Department of Environmental Sciences and Engineering, University of North Carolina, Chapel Hill, NC 1979.
  • M.S., Environmental Engineering, Cornell University, Ithaca, NY, 1975.
  • B.S., Civil and Environmental Engineering, Cornell University, Ithaca, NY, 1973.

Research Interests  [ Top ]

  • Ecology of streams (nutrient cycling, primary production, algal-herbivore interactions, carbon dynamics and energy flow)
  • Biogeochemistry and land/water interactions in forested catchments
  • Watershed hydrology
  • Wetland and riparian ecosystems
  • Climate change effects on freshwater ecosystems

Current Research Projects  [ Top ]

Lotic Intersite Nitrogen Experiment (LINX) II: tracer 15N-nitrate experiments in streams
I am leading an intersite study of uptake and retention of nitrate in stream ecosystems. This study involves 15N additions (as nitrate) to 9 streams in each of 8 different regions/biomes of the U.S. to identify rates and controls on nitrate dynamics in small streams. To determine the effect of human land use changes on stream nitrogen dynamics, the 15N addition experiments are being conducted in streams within agricultural, urban, and reference (native vegetation) in each region. The study also includes development of a mechanistic model of stream nitrogen dynamics based on the 15N experiment results, application of the model to predict nitrate transport and retention in a large river basin in each region, and test of the model results using synoptic sampling of streams and rivers within each river basin. This project is supported by funding from the National Science Foundation (Integrated Research Challenges in Environmental Biology program). Scientists from 13 different universities and research institutions are participating. For more information, see the LINX project web-site: http://www.biol.vt.edu/faculty/webster/linx/

Long-term measurements of watershed hydrology and biogeochemical cycling in Walker Branch Watershed
I am leader of a project for long-term monitoring of hydrologic and chemical inputs and outputs from a forested watershed. This project is focused on Walker Branch Watershed on the Department of Energy’s Oak Ridge Environmental Research Park and is designed to quantify the response of the forest ecosystem to changes in climate and atmospheric deposition. The project includes monitoring of precipitation volume (hourly) and chemistry (weekly, NADP network), stream discharge (15-minute), and stream water chemistry (weekly). In addition, the stream chemistry measurements are being used to develop and test a new approach for determining below-ground soil CO2 flux rates (respiration rates) at the scale of the entire watershed. This project is supported by the Department of Energy’s Program for Ecological Research. For more information see the Walker Branch Watershed project web-site: http://walkerbranch.ornl.gov/<

Effects of military training and land management activities on riparian ecosystems at Fort Benning, Georgia
I am leader of a project to identify the effects of military training and land management activities on riparian ecosystems at Fort Benning, Georgia. This project involves studies of vegetation and soil characteristics in ephemeral drainages and the chemistry, metabolism, and biological communities of receiving streams. These studies are being conducted in catchments encompassing a large gradient in disturbance severity. The project also has a second phase to evaluate the ecological effects of restoration approaches involving physical stabilization and re-vegetation of eroded ephemeral drainages and in-stream additions of woody debris. The project also involves scientists and students from the School of Forestry and the Department of Biology at Auburn University. The project is funded by the Strategic Environmental Research and Development Program (SERDP), sponsored jointly by the U.S. Department of Defense, Department of Energy, and Environmental Protection Agency.

Recent Publications (last 10 years)  [ Top ]

  • Houser, J. N., P. J. Mulholland, and K. O. Maloney. 2006. Upland disturbance affects headwater stream nutrients and suspended sediments during baseflow and stormflow. Journal of Environmental Quality 35: 352-365.
  • Jardine, P. M., M. A. Mayes, P. J. Mulholland, P. J. Hanson, J. R. Tarver, R. J. Luxmoore, J. F. McCarthy, and G. V. Wilson. 2006. Vadose zone flow and transport of dissolved organic carbon at multiple scales in humid regimes. Vadose Zone Journal 5:140-152.
  • Steinman, A. D. and P. J. Mulholland. 2006. Phosphorus limitation, uptake, and turnover in benthic stream algae, Chapter 9. In: F. R. Hauer and G. A. Lamberti (eds), Methods in Stream Ecology, 2nd edition, Academic Press.
  • Fellows, C. S., H. M. Valett, C. N. Dahm, P. J. Mulholland, and S. A. Thomas. Coupling nutrient uptake and energy flow in headwater streams. Ecosystems (in press).
  • Mulholland, P. J., S. A. Thomas, H. M. Valett, J. R. Webster, and J. Beaulieu. Effects of light on nitrate uptake in small forested streams: diurnal and day-to-day variations. Journal of the North American Benthological Society (in press).
  • Roberts, B. J., P. J. Mulholland, and J. N. Houser. Effects of upland disturbance and in-stream restorations on hydrodynamics and ammonium uptake in headwater streams. Journal of the North American Benthological Society (in press).
  • Houser, J. N., P. J. Mulholland, and K. O. Maloney. 2005. Catchment disturbance and stream metabolism: patterns in stream respiration and gross primary production along a gradient of upland soil and vegetation disturbance. Journal of the North American Benthological Society 24(3): 538-552.
  • Maloney, K. O, P.J. Mulholland, and J.W. Feminella. 2005. The effects of catchment-scale military land use on stream physical and organic matter variables in small Southeastern Plains catchments (USA). Journal of Environmental Management 35:677-691.
  • Mulholland, P. J., J. N. Houser, and K. O. Maloney. 2005. Stream diurnal dissolved oxygen profiles as indicators of in-stream metabolism and disturbance effects: Fort Benning as a case study. Ecological Indicators 5:243-252.
  • Payn, R. A., J. R. Webster, P. J. Mulholland, H. M. Valett, and W. K. Dodds. 2005. Estimation of stream nutrient uptake from nutrient addition experiments. Limnology and Oceanography: Methods 3:174-182.
  • DeAngelis, D. L., and P. J. Mulholland. 2004. Dynamic consequences of allochthonous inutrient input to freshwater systems, pp. 12-24. In: Food Webs at the Landscape Level, G. A. Polis, M. E. Power, and G. R. Huxel (eds.), The University of Chicago Press, Chicago, IL.
  • Mulholland, P. J., H. M. Valett, J. R. Webster, S. A. Thomas, L. N. Cooper, S. K. Hamilton, and B. J. Peterson. 2004. Stream denitrification and total nitrate uptake rates measured using a field 15N isotope tracer approach. Limnology and Oceanography 49(3): 809-820.
  • Dale, V H., Mulholland, P., Olsen, L. M., Feminella, J., Maloney, K., White, D. C., Peacock, A., and Foster, T., “Selecting a Suite of Ecological Indicators for Resource Management,” Landscape Ecology and Wildlife Habitat Evaluation: Critical Information for Ecological Risk Assessment, Land-Use Management Activities and Biodiversity Enhancement Practices, ASTM STP 1458, L. A. Kapustka, H. Gilbraith, M. Luxon, and G. R. Biddinger, Eds., ASTM International, West Conshohocken, PA, 2004.
  • Mulholland, P. J. 2004. The importance of in-stream uptake for regulating stream concentrations and outputs of N and P from a forested watershed: evidence from long-term chemistry records for Walker Branch Watershed. Biogeochemistry 70: 403-426.
  • Thomas, S. A., H. M. Valett, J. R. Webster, and P. J. Mulholland. 2003. A regression approach to estimating reactive solute uptake in advective and transient storage zones of stream ecosystems. Advances in Water Resources 26:965-976.
  • Mulholland, P. J. 2003. Large scale patterns in DOC concentration, flux, and sources, pp. 139-159. In: S. Findlay and R. Sinsabaugh (ed.), Aquatic Ecosystems: Interactivity of Dissolved Organic Matter, Elsevier Science.
  • Webster, J. R., P. J. Mulholland, J. L. Tank, H. M. Valett, W. K. Dodds, B. J. Peterson, W. B. Bowden, C. N. Dahm, S. Findlay, S. V. Gregory, N. B. Grimm, S. K. Hamilton, S. L. Johnson, E. Marti, W. H. McDowell, J. L. Meyer, D. D. Morrall, S. A. Thomas, W. M. Wollheim. 2003. Factors affecting ammonium uptake in streams – an interbiome perspective. Freshwater Biology 48:1329-1352.
  • Jones, J. B., Jr., E. H. Stanley, and P. J. Mulholland. 2003. Long-term decline in carbon dioxide supersaturation in rivers across the contiguous United States. Geophysical Research Letters 30 (10):1495-1499.
  • Jones, J. B., E. H. Stanley, and P. J. Mulholland. 2003. Increased alkalinity in the Mississippi. Science 302:985 (letter).
  • Mulholland, P. J., J. L. Tank, J. R. Webster, W. B. Bowden, W. K. Dodds, S. V. Gregory, N. B. Grimm, S. K. Hamilton, S. L. Johnson, E. Marti, W. H. McDowell, J. Merriam, J. L. Meyer, B. J. Peterson, H. M. Valett, and W. M. Wollheim. 2002. Can uptake length in streams be determined by nutrient addition experiments? Results from an inter-biome comparison study. Journal of the North American Benthological Society 21: 544-560.
  • Findlay, S., J. Tank, S Dye, H. M. Valett, P. Mulholland, W. H. McDowell, S. Johnson, S. K. Hamilton, J. Edmonds, W. K. Dodds, W. B. Bowden. 2002. A cross-system comparison of bacterial and fungal biomass in detritus pools of headwater streams. Microbial Ecology 43:55-66.
  • Dodds, W. K., A. J. Lopez, W. B. Bowden, S. Gregory, N. B. Grimm, S. K. Hamilton, A. E. Hershey, E. Marti, W. H. McDowell, J. L. Meyer, D. Morrall, P. J. Mulholland, B. J. Peterson, J. L. Tank, H. M. Valett, J. R. Webster, and W. Wollheim. 2002. Nitrogen uptake as a function of concentration in streams. Journal of the North American Benthological Society 21:206-220.
  • Mulholland, P. J. 2002. Large scale patterns in DOC concentration, flux, and sources, Pages 139-159. In: S. Findlay (ed.), Dissolved Organic Carbon in Aquatic Ecosystems, Academic Press.
  • Mulholland, P. J., C. S. Fellows, J. L. Tank, N. B. Grimm, J. R. Webster, S. K. Hamilton, E. Marti, L. Ashkenas, W. B. Bowden, W. K. Dodds, W. H. McDowell, M. J. Paul, and B. J. Peterson. Inter-biome comparison of factors controlling stream metabolism. 2001. Freshwater Biology 46:1503-1517.
  • Sanzone, D. M., J. L. Tank, P. J. Mulholland, J. L. Meyer, and S. E. G. Findlay. 2001. Microbial incorporation of nitrogen in stream detritus. Hydrobiologia 464:27-35.
  • Martin, L. A., P. J. Mulholland, J. R. Webster, and H. M. Valett. 2001. Denitrification in sediments of headwater streams in the southern Appalachian Mountains, USA. Journal of the North American Benthological Society 20:505-519.
  • Wilson, K. B., P. J. Hanson, P. J. Mulholland, D. D. Baldocchi, and S. D. Wullschleger. 2001. A comparison of methods for determining forest evapotranspiration and its components across scales: sap-flow, soil water budget, eddy covariance and catchment water balance. Agricultural and Forest Meteorology 106:153-168.
  • Peterson, B. J., W. M. Wollheim, P. J. Mulholland, J. R. Webster, J. L. Meyer, J. L. Tank, E. Marti, W. B. Bowden, H. M. Valett, A. E. Hershey, W. H. McDowell, W. K. Dodds, S. K. Hamilton, S. Gregory, and D. J. Morrall. 2001. Control of nitrogen export from watersheds by headwater streams. Science 292:86-90.
  • Hill, W. R., P. J. Mulholland, and E. R. Marzolf. 2001. Stream ecosystem responses to forest leaf emergence in spring. Ecology 82:2306-2319.
  • Thomas, S.A., H.M. Valett, J.R.Webster, P.J. Mulholland, C.S. Fellows, C.N. Dahm, and C.G. Peterson. 2001. Nitrogen retention in headwater streamsthe influence of groundwater surface water interaction. In Optimizing Nitrogen Management in Food and Energy Production and Environmental ProtectionProceedings of the 2nd International Nitrogen Conference on Science and Policy. TheScientificWorld 1: 623-631.
  • Mulholland, P. J., J. L. Tank, D. M. Sanzone, W. M. Wollheim, B. J. Peterson, J. R. Webster, and J. L. Meyer. 2000. Food Web Relationships in a Forested Stream Determined by Natural Abundance and Experimental 15N-Tracer Studies. Journal of the North American Benthological Society 19:145-157.
  • Jones, J. G., Jr. and P. J. Mulholland. 2000. Streams and Ground Waters. Academic Press, San Diego.
  • Mulholland, P. J., J. L. Tank, D. M. Sanzone, W. M. Wollheim, B. J. Peterson, J. R. Webster, and J. L. Meyer. 2000. Nitrogen Cycling in a Forest Stream Determined by a 15N Tracer Addition. Ecological Monographs 70(3): 471-493.
  • Tank, J. L., J. L. Meyer, D. M. Sanzone, P. J. Mulholland, J. R. Webster, B. J. Peterson, W. M. Wollheim, and N. E. Leonard. 2000. Analysis of nitrogen cycling in a forest stream during autumn using a 15N tracer addition. Limnology and Oceanography 45:1013-1029. ESD #5029.
  • Mulholland, P. J., J. L. Tank, D. M. Sanzone, J. R. Webster, W. Wollheim, B. J. Peterson, and J. L. Meyer. 2000. Ammonium and nitrate uptake lengths in a small forested stream determined by 15N tracer and short-term nutrient enrichment experiments. Verh. Internat. Verein Limnol. 27 :1320-1325.
  • Mulholland, P. J., and D. L. DeAngelis. 2000. Effect of surface/subsurface exchange on nutrient dynamics and nutrient spiraling in streams, pp. 149-166. In: J. B. Jones, Jr. and P. J. Mulholland (eds.), Streams and Ground Waters. Academic, San Diego, CA.
  • Rosemond, A. D., P. J. Mulholland, and S. H. Brawley. 2000. Seasonally shifting limitation of stream periphyton: response of algal populations and assemblage biomass and productivity to variation in light, nutrients, and herbivores. Canadian Journal of Fisheries and Aquatic Sciences 57:66-75.
  • Meyer, J. L., M. J. Sale, P. J. Mulholland, and N. L. Poff. 1999. Impacts of climate change on aquatic ecosystem functioning and health. Journal of the American Water Resources Association 35:1373-1386.
  • Hart, D. R., P. J. Mulholland, E. R. Marzolf, D. L. DeAngelis, and S. P. Hendricks. 1999. Relationships between hydraulic parameters in a small stream under varying flow and seasonal conditions. Hydrologic Processes 13:1497-1510.
  • Jones, J. G., Jr., and P. J. Mulholland. 1998. Influence of drainage basin topography and elevation on carbon dioxide and methane supersaturation of stream water. Biogeochemistry 40: 57-72.
  • Jones, J. G., Jr., and P. J. Mulholland. 1998. Carbon dioxide variation in a hardwood forest stream: an integrative measure of whole catchment ecosystem respiration. Ecosystems 1: 183-196.
  • Jones, J. G., Jr., and P. J. Mulholland. 1998. Methane input and evasion in a hardwood forest stream: effects of subsurface flow from shallow and deep pathways. Limnology and Oceanography 43: 1243-1250.
  • Mulholland, P. J., and M. J. Sale. 1998. Impacts of climate change on water resources: findings of the IPCC Regional Assessment of Vulnerability for North America. Water Resources Update, Universities Council on Water Resources, Issue No. 112, pages10-15, Summer 1998.
  • Mulholland, P. J., E. R. Marzolf, J. R. Webster, D. R. Hart, and S. P. Hendricks. 1997. Evidence that hyporheic zones increase heterotrophic metabolism and phosphorus uptake in forest streams. Limnol. Oceanogr. 42:443-451.
  • Mulholland, P. J., and W. R. Hill. 1997. Separating catchment flowpath and instream effects on stream nutrient and DOC concentrations: evidence from long-term data records. Water Resources Research 33:1297-1306.
  • Mulholland, P. J. 1997. Dissolved organic matter concentration and flux in streams. Journal of the North American Benthological Society 16: 131-141.
  • Mulholland, P. J. 1997. Organic matter dynamics in the West Fork of Walker Branch, Tennessee, USA. Journal of the North American Benthological Society 16:61-67.
  • Mulholland, P. J., G. R Best, C. C. Coutant, G. M. Hornberger, J. L. Meyer, P. J. Robinson, J. R. Stenberg, R. E. Turner, F. Vera-Herrera, and R. G. Wetzel. 1997. Effects of climate change on freshwaters of the Southeastern United States and the Gulf Coast of Mexico. Hydrologic Processes 11:949-970.

Current Professional Activities  [ Top ]

  • Associate Editor, JGR-Biogeosciences, American Geophysical Union

Other Useful Links  [ Top ]

April 2006

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