Balsam fir tree canopy in Newfoundland, Canada

Italics indicate students or post-docs working in the lab.


Souza, L.F.T., Hirmas, D.R., Sullivan, P.L., Reuman, D.C., Kirk, M.F., Li, L., Ajami, H., Wen, H., Sarto, M.V.M., Loecke, T.D., Rudick, A.K., Rice, C.W., Billings, S.A. 2023. Root distributions, precipitation, and soil structure converge to govern soil organic carbon depth distributions. Geoderma 10.1016/j.geoderma.2023.116569.

Koop, A.N., Hirmas, D.R., Billings, S.A., Li, L., Cueva, A., Zhang, X., Wen, H., Nemes, A., Souza, L.F.T., Ajami, H., Flores, A.N., Rudick, A.K., Guthrie, A., Klamm, L.M., Unruh, M., Sullivan, P.L. 2023. Is macroporosity controlled by complexed clay and soil organic carbon? Geoderma 10.1016.j.geoderma.2023.116565.

Hauser, E., Chorover, J., Cook, C.W., Markewitz, D., Rasmussen, C., Richter, D.D., Billings, S.A. 2023. Integrating decadal and century-scale root development with longer-term soil development to understand terrestrial nutrient cycling. Geoderma 10.1016/j.geoderma.2023.116520.


Hauser, E., Sullivan, P.L., Flores, A.N., Hirmas, D., Billings, S.A. 2022. Global-scale shifts in rooting depths due to Anthropocene land cover changes pose unexamined consequences for critical zone functioning. Earth’s Future 10.1029/2022EF002897.

Wen, H., Sullivan, P.L., Billings, S.A., Ajami, H., Cueva, A., Flores, A., Hirmas, D.R., Koop, A.N., Murenbeeld, K., Zhang, X., Li, L. 2022. From soils to streams: Connecting terrestrial carbon transformation, chemical weathering, and solute export across hydrological regimes. Water Resources Research, 58, e2022WR032314 doi:10.1029/2022WR032314.

Sullivan, P.L., Billings, S.A., Hirmas, D, Li, L., Zhang, X., Zigler, S., Murenbeeld, K., Ajami, H., Guthrie, A., Singa, K., Gimenez, D., Duro, A., Moreno, V., Flores, A., Cueva, A., Koop, A., Aronson, E., Barnard, H., Banwart, S., Keen, R., Nemes, A., Nikolaidis, N., Nippert, J., Richter, D., Robinson, D.A., Sadayappan, K., Souza, L.F.T. de, Unruh, M., Wen, H. 2022. Embracing the dynamic nature of soil structure: A paradigm illuminating the role of life in critical zones of the Anthropocene. Earth-Science Reviews 10.1016/jearscirev.2021.103873

Bowering, K.L., Edwards, K.A., Wiersma, Y.F., Billings, S.A., Warren, J., Skinner, A., Ziegler, S.E. 2022. Dissolved organic carbon mobilization across a climate transect of mesic boreal forests is explained by air temperature and snowpack duration. Ecosystems 10.1007/s10021-022-00741-0.

Lorenz, K.E., Billings, S.A., Jungkunst, H.F. 2022. Soil organic carbon stabilization in forest subsoils: Directions for the research community. Journal of Plant Nutrition and Soil Science 10.1002/jpln.202200090 (editorial).

Billings, S.A., Sullivan, P.L. 2022. Working across scales to project soil biogeochemical responses to climate. In: Yang, Y., Keiluweit, M., Senesi, N., Xing, B., eds. Multi-Scale Biogeochemical Processes in Soil Ecosystems: Critical Reactions and Resilience to Climate Changes, Vol. 5 in IUPAC Series on Biophysico-Chemical Processes in Environmental Systems, Wiley.


de Souza, L.F.T., Billings, S.A. 2021. Temperature and pH mediate stoichiometric constraints of organically derived soil nutrients. Global Change Biology 10.1111/gcb.15985.

Billings, S.A., Lajtha, K., Malhotra, A., Berhe, A.A., de Graaff, M.-A., Earl, S., Fraterrigo, J., Georgiou, K., Grandy, S., Hobbie, S.E., Moore, J.A.M., Nadelhoffer, K., Pierson, D., Rasmussen, C., Silver, W.L., Sulman, B.N., Weintraub, S., Wieder, W. 2021. Soil organic carbon is not just for soil scientists: Measurement recommendations for diverse practitioners. Ecological Applications e02290.

Podrebarac, F., Billings, S.A., Edwards, K.A., Laganiere, J., Norwood, M.J., Ziegler, S.E. 2021. Soil profile connectivity can impact microbial substrate use, affecting how soil CO2 effluxes are controlled by temperature. Biogeosciences 18:4755-4772, 10.5194/bg-18-4755.

2019 to 2020:

Dove, N.C., Arogyaswamy, K., Billings, S.A., Bothoff, J.K., Carey, C.J., Cisco, C., DeForest, J.L., Fairbanks, D., Fierer, N., Gallery, R.E., Kaye, J.P., Lohse, K.A., Maltz, M.R., Mayora, E., Pett-Ridge, J., Yang, W.H., Hart, S.C., Aronson, E.L. 2020. Continental-scale patterns of extracellular enzyme activity in the subsoil: an overlooked reservoir of microbial activity. Environmental Research Letters 15:1040a1.

Wen, H., Sullivan, P., Macpherson, G.L., Billings, S.A., Li, L. 2020. Deepening roots can enhance carbonate weathering. Biogeosciences 18:55-75.

Kohl, L., Myers-Pigg, A., Edwards, K.A., Billings, S.A., Warren, J., Podrebarac, F.A., Ziegler, S.E. 2020. Microbial inputs at the litter layer translate climate into altered organic matter properties. Global Change Biology doi:10.1111/gcb.15420.

Wieder, W.R., Pierson, D., Earl, S., Lajtha, K., Baer, S., Ballantyne, F., Berhe, A.A., Billings, S.A., Brigham, L.M., Chacon, S.S., Fraterrigo, J., Frey, S.D., Georgiou, K., de Graaff M.-A., Grandy, A.S., Hartman, M.D., Hobbie, S.E., Johnson, C., Kaye, J., Kyker-Snowman, E., Litvak, M.E., Mack, M.C., Malhotra, A., Moore, J.A.M., Nadelhoffer, K., Rasmussen, C., Silver, W.L., Sulman, B.N., Walker, X., Weintraub, S. 2020. SoDaH: the Soils Data Harmonization database, an open-source synthesis of soil data from research networks, version 1.0. Earth System Science Data doi:10.5194/essd-2020-195.

Billings, S.A., de Souza, L.F.T. 2020. Earth harbours ancient carbon. Nature Geoscience 13:5260528.

Lohse, K.A., Billings, S.A., DiBiase, R.A., Kumar, P., Berhe, A.A., Kaye, J. 2020. Soil signals tell of landscape disturbances. Eos 101, doi:10.1029/2020EO148736.

Buckeridge, K.M., Edwards, K.A., Min, K., Ziegler, S.E., Billings, S.A. 2020. Short- and long-term temperature responses of soil denitrifier net N2O efflux rates, inter-profile N2O dynamics, and microbial genetic potentials. Soil, doi:10.5194/soil-6-399-2020.

Dodds, W.K., Zeglin, L.H., Ramos, R.J., Platt, T.G., Pandey, A., Michaels, T., Masigol, M., Klompen, A.M.L., Kelly, M.C., Jumpponen, A., Hauser, E., Hansen, P.M., Greer, M.J., Fattahi, N., Delavaux, C.S., Connell, R.K., Billings, S.A., Bever, J.D., Barua, N., Agusto, F.B. Connections and feedback: Aquatic, plant, and soil microbiomes in heterogeneous and changing environments. Bioscience 70:548-562.

Richter, D.deB., Billings, S.A. 2020. Ansichten der Calzone: Views of the Calhoun Critical Zone Observatory. In: Latour, B., Weibel, P. Critical Zones: The Science and Politics of Landing on Earth. MIT Press.

Hauser, E., Richter, D.D., Markewitz, D., Brecheisen, Z., Billings, S.A. 2020. Persistent anthropogenic legacies structure depth dependence of regenerating rooting systems and their functions. Biogeochemistry doi:10.1007/s10533-020-00641-2.

Richter, D.deB., Eppes, M.-C., Austin, J.C., Bacon, A.R., Billings, S.A., Brecheisen, Z., Ferguson, T.A., Markewitz, D., Pachon, J., Schroeder, P.A., Wade, A.M. 2020. Soil production and the soil geomorphology legacy of Grove Karl Gilbert. Soil Society of America Journal, doi:10.2136/sssaj2019.01.0021. 

Richter, D.deB., Billings, S.A., Waters, C. 2019. A pedology and pedostratigraphy for the Anthropocene. In Chapter 2, Stratigraphic signatures of the Anthropocene. Zalasiewicz, J., Waters, C., Williams, M., Summerhayes, C., eds. The Anthropocene as a Geological Time Unit, Cambridge University Press.

Brewer, T.E., Aronson, E.L., Arogyaswamy, K., Billings, S.A., Botthoff, J.K., Campbell, A.N., Dove, N.C., Fairbanks, D., Gallery, R.E., Hart, S.C., Kaye, J., King, G., Logan, G., Lohse, K.A., Maltz, M.R., Mayorga, E., O’Neill, C., Owens, S.M., Packman, A., Pett-Ridge, J., Plante, A.F., Richter, D.deB., Silver, W.L., Yang, W.H., Fierer, N. 2019. Ecological and genomic attributes of novel bacterial taxa that thrive in subsurface soil horizons. mBio 10, e01318-19.

Min, K., Buckeridge, K., Ziegler, S.E., Edwards, K.A., Bagchi, S., Billings, S.A. 2019. Temperature sensitivity of biomass-specific microbial exo-enzyme activities and CO2 efflux is resistant to change across short- and long-term timescales. Global Change Biology 25:1793-1807.

2017 to 2018:

Billings, S.A., Richter, D.deB., Ziegler, S.E., Prestegaard, K., Wade, A.M. 2018. Distinct contributions of eroding and depositional profiles to land-atmosphere CO2 exchange in two contrasting forests. Frontiers in Earth Science 7 doi: 10.3389/feart.2019.00036.

Philben, M., Butler, S., Billings, S.A., Benner, R., Edwards, K.A., Ziegler, S.E.  2018.  Biochemical and structural controls on the decomposition dynamics of boreal upland forest moss tissues.  Biogeosciences 15:6731-6746, doi: 10.5194/bg-15-6731-2018. 

Richter, D.D., Billings, S.A., et al. 2018.  Ideas and perspectives: Strengthening the biogeosciences in environmental research networks. Biogeosciences 15:4815-4832, doi: 10.5194/bg-15-4815-2018. 

Ballantyne, F., Billings, S.A.  2018.  Model formulation of microbial CO2 production and efficiency can significantly influence short and long term soil C projections.  The ISME Journal doi: 10.1038/s41396-018-0085-1.  

Billings, S.A., Hirmas, D., Sullivan, P.L., Lehmeier, C.A., Bagchi, S., Min, K., Brecheisen, Z., Hauser, E., Stair, R., Flournoy, R., Richter, D. deB.  2018.  Loss of deep roots limits biogenic agents of soil development that are only partially restored by decades of forest regeneration.  Elementa: Science of the Anthropocene 6:34, doi: 10.1525/elementa.287.   

Philben, M., Billings, S.A., Edwards, K.A., Podrebarac, F.A., van Biesen, G., Ziegler, S.E.  2018. Amino acid δ15N indicates lack of N isotope fractionation during soil organic nitrogen decomposition.  Biogeochemistry doi: 10.1007/s10533-018-0429-y.  

Sullivan, P.L., Wymore, A., McDowell, W. and 51 other contributors. 2017. New opportunities for Critical Zone science. Arlington VA NSF meeting for CZ Science White Booklet, U.S. NSF Critical Zone Observatories National Program.

Ziegler, S.E., Benner, R., Billings, S.A., Edwards, K.A., Philben, M., Zhu, X., Laganière, J. 2017. Climate warming can accelerate carbon fluxes without changing soil carbon stocks.  Frontiers in Earth Science 5:2 doi: 10.3389/feart.2017.00002. 

2015 to 2016:

Min, K., Lehmeier, C.A., Ballantyne IV, F., Billings, S.A. 2016. Carbon availability modifies temperature responses of heterotrophic microbial respiration, carbon uptake affinity, and stable carbon isotope discrimination. Frontiers in Microbiology 7:2083. doi: 10.3389/fmicb.2016.02083.

Billings, S.A., Min, K., Ballantyne IV, F., Chen, Y., Sellers, M. 2016. Aging exo-enzymes can create temporally shifting, temperature-dependent resource landscapes for microbes. Biogeochemistry DOI 10.1007/s10533-016-0273-x.

Lehmeier, C.A., Ballantyne IV, F., Min, K., Billings, S.A.  2016.  Temperature-mediated changes in microbial carbon use efficiency and 13C discrimination.  Biogeosciences 13:3319-3329. 

Dialynas, Y.G., Bastola, S., Bras, R.L., Billings, S.A., Markewitz, D., Richter, D. deB.  2016.  Topographic variability and the influence of soil erosion on the carbon cycle.  Global Biogeochemical Cycles 30, doi:10.1002/2015GB005302. 

Billings, S.A., Boone, A.S., Stephen, F.M.  2016.  Tree-ring δ13C and δ18O, leaf δ13C and wood and leaf N status demonstrate tree growth strategies and predict susceptibility to disturbance.  Tree Physiology doi:10.1093/treephys/tpw010. 

Billings, S.A., Glaser, S.M., Boone, A.S., Stephen, F.M.  2016.  Nonlinear tree growth dynamics predict resilience to disturbance.  Ecosphere doi:10.1890/ES15-00176.1.

Huang, Z., Liu, B., Davis, M., Sardans, J., Penuelas, J., Billings, S.A.  2015.  Long-term nitrogen deposition linked to reduced water use efficiency in forests with low phosphorus availability.  New Phytologist doi: 10.1111/nph.13785.

Podrebarac, F.A., Laganière, J., Billings, S.A., Edwards, K.A., Ziegler, S.E.  2015.  Soils isolated during incubation underestimate temperature sensitivity of respiration and its response to climate history.  Soil Biology  Biochemistry 93:60-68.

Haavik, L.J., Billings, S.A., Guldin, J.M., Stephen, F.M.  2015. Emergent insects, pathogens and drought shape changing patterns in oak decline in North America and Europe.  Forest Ecology and Management 354:190-205.

Kohl, L., Laganière, J., Edwards, K.A., Billings, S.A., Morrill, P., Van Biesen, G., Ziegler, S.E. 2015. Distinct fungal and bacterial δ13C signatures as potential drivers of increasing δ13C of soil organic matter with depth.  Biogeochemistry doi: 10.1007/s10533-015-0107-2.

Billings, S.A., Tiemann, L.K., Ballantyne, F., Lehmeier C.A., Min, K. 2015.  Investigating microbial transformations of soil organic matter: synthesizing knowledge from disparate fields to guide new experimentation.  Soil 1:313-330. 

Laganière, J., Podrebarac, F., Billings, S.A., Edwards, K.A., Ziegler, S.E. 2015. A warmer climate reduces the bioreactivity of isolated boreal forest soil horizons without increasing the temperature sensitivity of respiratory CO2 loss. Soil Biology and Biochemistry 84:177-188. 

Richter, D. deB., Billings, S.A. 2015.  ‘One physical system’: Tansley’s ecosystem as Earth’s critical zone.  New Phytologist Tansley Review, doi: 10.1111/nph.13338. 

Billings, S.A., Schlesinger, W. 2015. Letter to the Editor on ‘Pyrogenic organic matter production from wildfires: a missing sink in the global carbon cycle.’ Global Change Biology doi: 10.1111/gcb.12836. 


Billings, S.A., Tiemann, L.K. 2014. Warming-induced enhancement of soil N2O efflux linked to distinct response times of genes driving N2O production and consumption. Biogeochemistry doi 10.1007/s10533-014-9973-2. 

Min, K., Lehmeier, C.A., Ballantyne, F., Tatarko, A., Billings, S.A. 2014. Differential effects of pH on temperature sensitivity of organic carbon and nitrogen decay. Soil Biology and Biochemistry 76:193-200. 

Richter, D.deB, Bacon, A.R., Billings, S.A., Binkley, D., Buford, M., Callaham, M.A., Curry, A.E., Fimmen, R.L., Grandy, A.S., Heine, P.R., Hofmockel, M., Jackson, J.A., Lemaster, E., Li, J.W., Markewitz, D., Mobley, M.L., Morrison, M.W., Strickland, M.S., Waldrop, T., and Wells, C.G. 2014. Evolution of Soil, Ecosystem, and Critical Zone Research at the Calhoun Experimental Forest, in Hayes, D.C., Stout, S., Hoover, A., and Crawford, R. Research for the Long-Term: The interplay of societal need and research on USDA Forest Service Experimental Forests and Ranges. Springer Verlag, NY. 

2012 to 2013:

Greenfield, L.G., Gregorich, E.G., van Kessel, C., Baldock, J.A., Beare, M.H., Billings, S.A., Clinton, P.W., Condron, L.M., Hill, S., Hopkins, D.W., Janzen, H.H. 2013. Acid hydrolysis to define a biologically-resistant pool is compromised by carbon loss and transformation. Soil Biology and Biochemistry 64:122-126. 

Ziegler, S.E., Billings, S.A., Lane, C.S., Li, J., Fogel, M.L. 2013. Warming alters routing of labile and slower-turnover carbon through distinct microbial groups in boreal forest organic soils.Soil Biology and Biochemistry 60:23-32.  

Lehmeier, C.A., Min, K., Niehues, N.D., Ballantyne IV, F., Billings, S.A. 2013. Temperature-mediated changes of exoenzyme-substrate reaction rates and their consequences for the carbon to nitrogen flow ratio of liberated resources. Soil Biology and Biochemistry. 57:374-382 

Billings, S.A., Ballantyne IV, F. 2013. How interactions between microbial resource demands, soil organic matter stoichiometry, and substrate reactivity determine the direction and magnitude of soil respiratory responses to warming. Global Change Biology doi:10.1111/gcb.12029. 

Li, J., Ziegler, S.E., Lane, C.S., Billings, S.A. 2013. Legacies of native climate regime govern responses of boreal soil microbes to litter stoichiometry and temperature. Soil Biology and Biochemistry 66:204-213. 

Billings, S.A., Ziegler, S.E., Schlesinger, W.H., Benner, R., Richter, D.deB. 2012. Predicting carbon cycle feedbacks to climate: Integrating the right tools for the job. Eos, 93:188-189.

Li, J., Ziegler, S.E., Lane, C., Billings, S.A. 2012. Warming-enhanced preferential mineralization of humified boreal forest soil organic matter: Interpretation of soil profiles along a climate transect using laboratory incubations. Journal of Geophysical Research – Biogeosciences, Vol. 117, G02008, 13pp.

Tiemann, L.K.Billings, S.A. 2012. Tracking C and N flows through microbial biomass with increased soil moisture variability. Soil Biology and Biochemistry 49:11-22. 

Grandy, A.S., Fraterrigo, J.M., Billings, S.A. 2012. Soil ecosystem resilience and recovery, in Wall, D.H., Bardgett, R.D., Behan-Pelletier, V., Herrick, J.E., Jones, H., Ritz, K., Six, J., Strong, D.R., and van der Putten, W.H. Soil Ecology and Ecosystem Services.Oxford University Press, UK.

2009 to 2011:

Richter, D.deB., with 32 co-authors. 2011. (Invited) Human-soil relations are changing rapidly: Proposals from SSSA’s cross-divisional soil change working group. Soil Science Society of America Journal 75:1-6. 

Billings, S.A., Phillips, N. 2011. (Invited) Forest biogeochemistry and drought. In: Levia, D.F., Carlyle-Moses, D.E. and Tanaka, T. (Eds.), Forest Hydrology and Biogeochemistry: Synthesis of Past Research and Future Directions. Ecological Studies Series, No. 216, Springer-Verlag, Heidelberg, Germany, pp. 581-597. 

Tiemann, L.K.Billings, S.A. 2011. Changes in variability of soil moisture alter microbial community C and N resource use. Soil Biology and Biochemistry 43:1837-1847. 

Drake, J., Gallet-Budynek, A. Hofmockel, K. Bernhardt, E. Billings, S.A., Jackson, R. Johnsen, K., Lichter, J., Phillips, R., McCarthy, H., Moore, D., McCormack, M.L. Palmroth, S. Oren, R., Pippen, J., Pritchard, S., Treseder, K., Schlesinger, W., DeLucia, E., Finzi, A. 2011. Increases in the flux of carbon belowground stimulate nitrogen uptake and sustain the long-term enhancement of forest productivity under elevated CO2Ecology Letters 14:349-357, doi: 10.111/j.1461-0248.2011.01593.x. 

Tiemann, L.K.Billings, S.A. 2011. Indirect effects of nitrogen amendments on organic substrate quality increase enzymatic activity driving decomposition in a mesic grassland.Ecosystems 14:234-247, doi:1-.1007/s10021-010-9406-6. 

Ziegler, S.E., Billings, S.A. 2011. Soil nitrogen status as a regulator of carbon substrate flows through microbial communities with elevated CO2Journal of Geophysical Research Biogeosciences 116, G01011, doi:10.1029/2010JG001434. 

Grandy, A.S., Billings, S.A., Richter, de B.D. 2010. Saving our soils. Frontiers in Ecology and the Environment 8(4):171. 

Billings, S.A., Buddemeier, R.W., Richter, de B.D., van Oost, K., Bohling, G. 2010. A simple method for estimating the influence of eroding soil profiles on atmospheric CO2Global Biogeochemical Cycles Vol. 24, GB2001,doi:10.1029/2009GB003560. 

Billings, S.A., Lichter, J., Ziegler, S.E., Hungate, B.A., Richter, de B.D. 2010. A call to investigate drivers of soil organic matter retention vs. mineralization in a high CO2 world. Soil Biology and Biochemistry 42:665-668. 

Smith, V., Sturm, B.S.M., deNoyelles, F.J., Billings, S.A. 2010. The ecology of algal biodiesel production. Trends in Ecology and Evolution, Vol 25,5:301-309. 

Goedhart, C.M., Pataki, D.E., Billings, S.A. 2010. Seasonal variations in plant nitrogen relations and photosynthesis along a grassland to shrubland gradient in Owens Valley, California. Plant and Soil 327:213-223. 

York, H.A., Billings, S.A. 2009. Stable-isotope analysis of diet in the short-tailed fruit bats (Chiroptera: Phyllostomidae: Carollia). Journal of Mammalogy 90:1469-1477. 

2006 to 2008:

Billings, S.A. 2008. (Invited) Biogeochemistry: Nitrous oxide in flux. Nature 456:888.

Lichter, J., Billings, S.A., Ziegler, S.E., Gaindh, D., Ryals, R., Finzi, A.C., Jackson, R.B., Stemmler, E.A., Schlesinger, W.H. 2008. Soil carbon sequestration in a pine forest after nine years of atmospheric CO2 enrichment. Global Change Biology 14:2910-2922. [Selected as a research highlight by Nature Reports Climate Change 3:2.] 

Pataki, D.E., Billings, S.A., Naumburg, E., Goedhart, C.M. 2008. Water sources and nitrogen relations of grasses and shrubs in phreatophytic communities of the Great Basin Desert.Journal of Arid Environments 72:1581-1593. 

Billings, S.A., Richter, D. 2008. The science of global soil change: Networking for our future.Eos: Transactions of the American Geophysical Union 89:151. 

Richter, D., Billings, S.A. 2008. Strengthening the world’s long-term soil research base.International Union of Soil Scientists Bulletin 112:10-12. 

Tiemann, L.Billings, S.A. 2008. Carbon controls on nitrous oxide production with changes in substrate availability in a North American grassland. Soil Science 17:332-341. 

Bijoor, N.S., Czimczik, C., Pataki, D., Billings, S.A. 2008. The effects of temperature and fertilization on nitrogen cycling and community composition of an urban lawn. Global Change Biology 14:2119-2131. [Selected as a research highlight by Nature 454:670.] 

Billings, S.A., Ziegler, S.E. 2008. Altered patterns of soil carbon substrate usage and heterotrophic respiration in a pine forest with elevated CO2 and N fertilization. Global Change Biology 14:1025-1036. 

Haavik, L., Stephen, F., Fierke, M., Salisbury, V., Leavitt, S., Billings, S.A. 2008. Dendrochronological parameters of northern red oak (Quercus rubra L. (Fagaceae)) infested with red oak borer (Enapholodes rufulus (Haldeman) (Coleoptera: Cerambycidae)). Forest Ecology and Management 255:1501-1509. 

Billings, S.A., Gaydess, E. 2008. Soil nitrogen and carbon dynamics in a fragmented landscape experiencing forest succession. Landscape Ecology 23:581-593. 

Schaeffer, S.M., Billings, S.A., Evans, R.D. 2007. Laboratory incubations reveal potential responses of soil nitrogen cycling to changes in soil C and N availability in Mojave Desert soils exposed to elevated atmospheric CO2Global Change Biology 13: 854-865, DOI 10.111/j.1365-2486.2007.01324.x 

Billings, S.A. 2006. Soil organic matter dynamics and land use change at a grassland/ forest ecotone. Soil Biology and Biochemistry 38: 2934-2943. 

Billings, S.A., Richter, D.D. 2006. Changes in stable isotopic signatures of soil nitrogen and carbon during forty years of forest development. Oecologia 148: 325-333, DOI 10.1007/s00442-006-0366-7. 

Billings, S.A., Brewer, C.M., Foster, B. 2006. Incorporation of plant residues into soil organic matter fractions with grassland management practices in the North American Midwest.Ecosystems 9: DOI: 10.1007/s10021-006-0080-7.

2003 to 2005:

Billings, S.A., Ziegler S. 2005. Linking microbial activity and soil organic matter transformations in forest soils under elevated CO2. Global Change Biology 11:203-212. 

Billings, S.A., Schaeffer, S.M., Evans, R.D. 2004. Response of soil microbial activity and N mineralization to elevated CO2 in Mojave Desert soils. Global Biogeochemical Cycles18:GB1011, doi:10,1029/2003GB002137. 

Billings, S.A., Zitzer, S., Weatherley, H., Schaeffer, S.M., Charlet, T., Arnone, J., Evans, R.D. 2003. Effects of elevated CO2 on green tissue and litter quality in an intact Mojave Desert ecosystem. Global Change Biology 5:729-735. 

Billings, S.A., Schaeffer, S.M., Evans, R.D. 2003. Nitrogen fixation by biological soil crusts and free-living bacteria in an intact Mojave Desert ecosystem with elevated CO2 and added soil carbon. Soil Biology and Biochemistry 35:643-649. 

Schaeffer, S.M., Billings, S.A., Evans, R.D. 2003. Responses of nitrogen dynamics in an intact Mojave Desert ecosystem to manipulations in soil carbon and nitrogen availability.Oecologia 134:547-553. 

1998 to 2002:

Billings, S.A., Schaeffer, S.M., Zitzer, S., Evans, R.D. 2002. Trace N gas losses and N mineralization in an intact Mojave Desert ecosystem with elevated CO2. Soil Biology and Biochemistry 34:1777-1784. 

Billings, S.A., Schaeffer, S.M., Zitzer, S., Charlet, T., Smith, S.D., Evans, R.D. 2002. Alterations of nitrogen dynamics under elevated CO2 in an intact Mojave Desert ecosystem: evidence from d15N. Oecologia 131:463-467. 

Yarie, J., Billings, S.A. 2002. Carbon balance of the taiga forest within Alaska: present and future. Canadian Journal of Forest Research 32:757-767. 

Billings, S.A., Richter, D., Yarie, J. 2000. Sensitivity of soil methane fluxes to an altered precipitation regime in boreal forest soils. Soil Biology and Biochemistry 32:1431-1441. 

Billings, S.A., Richter, D., Yarie, J. 1998. Soil carbon dioxide fluxes and profile concentrations in two boreal forests. Canadian Journal of Forest Research 28:1773-1783.