Editor-in-Chief for the Americas, TREES Structure and Function
Forest Sciences Centre 3041
2424 Main Mall
Vancouver, BC V6T 1Z4
work phone: 6048226023

Areas of research include:

  • Ecophysiology and stress physiology of trees and other plants
  • Use of stable isotopes in plant physiology and ecology
  • Phenotypic plasticity and resource allocation
  • Photosynthesis
  • Respiration (particularly alternative path respiration)
  • Water relations
  • Phenology
  • Forest regeneration and stock quality


Comparative physiology of plant adaptation: resource acquisition and constraints of growing season length in balsam poplar from temperate, boreal and arctic environments


Unit Associations

Department of Botany

Professional Affiliations

American Society of Plant Biologists ASPB
Canadian Botanical Association CBA
Canadian Society of Plant Biologists CSPB


UBC Killam Teaching Prize , 2005
David J. Gifford Award in Tree Physiology , 2012

Current Graduate Students

Estefania Milla, MSc
Anatomical basis of variation in mesophyll conductance of balsam poplar
Mina Momayyezi, PhD
Physiological basis of variation in mesophyll conductance of balsam poplar
Natalie Ryan, MSc
Uncoupling intrinsic growth potential and phenology in intra-specific hybrids of Populus balsamifera L.
Kirsten Dales, PhD
Shalom D AddoDanso, PhD
Productivity, carbon cycling and allocation in tropical primary and secondary forests in Ghana (co-supervised)

Post Doctoral Fellows and Research Assistants

Dr. Athena McKown
Dr. David Galvez

Current Courses

Winter 2016

FRST200 Forest Plant Biology I Sections

The structure, diversity and development of trees and other plants, with emphasis on the angiosperms.

Winter 2016

FRST516 Tree Physiology Sections

Growth and development of woody plants; physiological responses to abiotic and biotic environmental factors; consequences of silvicultural practices on physiological processes.

Selected Publications

Kalcsits, LA, & RD Guy (2016). Variation in fluxes estimated from nitrogen isotope discrimination correspond with independent measures of nitrogen flux in Populus balsamifera L. Plant Cell Environ 39:310-319
Milla-Moreno, EA, AD McKown, RD Guy & RY Soolanayakanahally (2016). Leaf mass area predicts palisade structural properties linked to mesophyll conductance in balsam poplar (Populus balsamifera L.) Botany 94:225-239
Porth, I., Klápště, J., McKown, A.D., La Mantia, J. Guy, R. D., Ingvarsson, P.K., Hamelin, R., Mansfield, S.D., Ehlting, J., Douglas, C.J., El-Kassaby, Y.A. (2015). Evolutionary quantitative genomics of Populus trichocarpa PLOS Genetics 10(11): e0142864.
Soolanayakanahally, RY, RD Guy, NR Street, KM Robinson, SN Silim, BR Albrectsen & S Jansson (2015). Comparative physiology of allopatric Populus species: geographic clines in photosynthesis, height growth, and carbon isotope discrimination in common gardens Front Plant Sci 6:528
Kalcsits, LA, X Min & RD Guy (2015). Interspecific variation in leaf-root differences in nitrogen isotope composition among three tree species grown with either nitrate or ammonium Trees Struct Funct 29:1069-1078
Geraldes, A, CA Hefer, A Capron, N Kolosova, F Martinez-Nuñez, RY Soolanayakanahally, B Stanton, R Shuren, RD Guy, SD Mansfield, CJ Douglas & QCB Cronk (2015). Recent Y chromosome divergence despite ancient origin of dioecy in poplars (Populus) Molecular Ecology 24(13):3243-3256. doi: 10.1111/mec.13126
McKown, AD, RD Guy, L Quamme, J Klápště, J La Mantia, CP Constabel, YA El-Kassaby, RD Hamelin, M Zifkin & MS Azam (2014). Association genetics, geography and ecophysiology link stomatal patterning in Populus trichocarpa with carbon gain and disease resistance trade-offs Molecular Ecology 23:5771-5790
Geraldes, A, N Farzaneh, CJ Grassa, AD McKown, RD Guy, SD Mansfield, CJ Douglas & QCB Cronk (2014). Landscape genomics of Populus trichocarpa: the role of hybridization, limited gene flow and natural selection in shaping patterns of population structure Evolution 68:3260-3280
Barchet, G.L.H., R. Dauwe, R.D. Guy, W. Schroeder, R. Soolanayakanahally, M.M. Campbell & S.D. Mansfield (2014). Investigating the drought stress response of hybrid poplar genotypes by metabolite profiling Tree Physiol 34:1203-1219
Kalcsits, L.A., H.A. Buschhaus & R.D. Guy (2014). Nitrogen isotope discrimination as an integrated measure of nitrogen fluxes, assimilation and allocation in plants Physiol Plant 151:293-304
Pointeau, V.M., & R.D. Guy (2014). Comparative resource-use efficiencies and growth of Populus trichocarpa and Populus balsamifera under glasshouse conditions Botany 92:443-451
McKown, A.D., J. Klápště, R.D. Guy, A. Geraldes, I. Porth, J. Hannemann, M. Friedmann, W. Muchero, G.A. Tuskan, J. Ehlting, Q.C.B. Cronk, Y.A. El-Kassaby, S.D. Mansfield and C.J. Douglas. (2014). Genome-wide association implicates numerous genes underlying ecological trait variation in natural populations of Populus trichocarpa New Phytol 203:535-553
Guy, R.D. (2014). The early bud gets to warm New Phytol 202:7-9
McKown, A.D., R.D. Guy, J. Klápšte, A. Geraldes, M. Friedmann, Q.C.B. Cronk, Y.A. El-Kassaby, S.D. Mansfield and C.J. Douglas. (2014). Geographical and environmental gradients shape phenotypic trait variation and genetic structure in Populus trichocarpa New Phytologist 201:1263-1276.
Porth, I., J. Klápšte, A.D. McKown, J. LaMantia, R.C. Hamelin, O. Skyba, F. Unda, M.C. Friedmann, Q.C.B. Cronk, J. Ethling, R.D. Guy, S.D. Mansfield, Y.A. El-Kassaby and C.J. Douglas. (2014). Extensive functional pleiotropy of REVOLUTA substantiated through forward genetics Plant Physiology 164:548-554.
La Mantia, J., J. Klápšte, Y.A. El-Kassaby, S. Azam, R.D. Guy, C.J. Douglas, S.D. Mansfield, and R. Hamelin (2013). Association analysis identifies Melampsora x columbiana poplar leaf rust resistance SNPs PLoS ONE 8:e78423
Porth, .I, J. Klapšte, O. Skyba, A. Geraldes, J. Hannemann, A.D. McKown, R.D. Guy, S.P. DiFazio, W. Muchero, P. Ranjan, G.A. Tuskan, M.C. Friedmann, J. Ehlting, Q.C.B. Cronk, Y.A. El-Kassaby, C.J. Douglas & S.D. Mansfield (2013). Genome-wide association mapping for wood characteristics in Populus identifies an array of candidate SNPs New Phytol 200:710-726
Soolanayakanahally, RY., R.D. Guy, S.N. Silim & M. Song (2013). Timing of photoperiodic competency causes phenological mismatch in balsam poplar (Populus balsamifera L.). Plant Cell Environ 36:116-127
Olson, M.S., N. Levsen, R.Y. Soolanayakanahally, R.D. Guy, W.R. Schroeder, S.R. Keller & P. Tiffin (2013). The adaptive potential of Populus balsamifera L. to phenology requirements in a warmer global climate Molecular Ecology 22:1214–1230
Geraldes, A., S.P. DiFazio, G.T. Slavov, P. Ranjan, W. Muchero, J. Hannemann, L.E. Gunter, A. Wymore, C. Grassa, N. Farzaneh, I. Porth, A.D. McKown, O. Skyba, E. Li, M. Fujita, J. Klápšte, J. Martin, W. Schackwitz, C. Pennacchio, D.niel Rokhsar, M.C. Friedmann, G.O. Wasteneys, R.D. Guy, Y.A. El-Kassaby, S.D. Mansfield, Q.C.B. Cronk, J. Ehlting, C.J. Douglas, and G.A. Tuskan. (2013). A 34K SNP genotyping array for Populus trichocarpa: Design, application to the study of natural populations and transferability to other Populus species. Molecular Ecology Resources. 13:306–323.
McKown, A.D., R.D. Guy, M.S. Azam, E.C. Drewes & L. Quamme (2013). Seasonality and phenology alter functional leaf traits Oecologia 172:653–665
Kalcsits, L.A., & R.D. Guy (2013). Whole plant and organ level nitrogen isotope discrimination indicates modification of partitioning of assimilation, fluxes and allocation of nitrogen in knockout lines of Arabidopsis thaliana Physiol Plant 149:249-259
Kalcsits, L.A., & R.D. Guy (2013). Quantifying remobilization of pre-existing nitrogen from cuttings to developing roots, stems and leaves of woody plants using 15N at natural abundance Plant Methods 9:27
Hember, R.A., Kurz, W.A., Metsaranta, J.M., Black, T.A., Guy, R.D., Coops, N.C. (2012). Accelerating regrowth of temperate-maritime forests due to enivronmental change Global Change Biology 18(6):2026-2040
Yousry A. El-Kassaby, Jaroslav Klápšte and Robert D. Guy (2012). Breeding without Breeding: selection using the genomic best linear unbiased predictor method (GBLUP) -New Forests 43:631-637.
Keller SR, Soolanayakanahally RY, Guy RD, Olson MS, Tiffin P (2011). Climate-driven adaptive divergence in ecophysiology and phenology during the post-glacial expansion of balsam poplar, Populus balsamifera L. American Journal of Botany 98:99–108
Dordel, J., Simard, S.W., Bauhus, J., Guy, R.D., Prescott, C., Seely, B., Pojas, L.J. (2011). Effects of nurse-crop species and density on nutrient and water availability to underplanted T. ciliata in north-eastern Argentina Canadian Journal of Forest Research 41:1754-1768.
Kranabetter JM, Simard SW, Coates KD, Guy R. (2010). Species patterns in foliar nitrogen concentration, nitrogen content and 13C abundance for understory saplings across light gradients Plant Soil 327:389-401
Teste FP, Simard SW, Durall DM, Guy R, Berch SM (2010). Net carbon transfer occurs under soil disturbance between Pseudotsuga menziesii var. glauca seedlings in the field Journal of Ecology, 98: 429-439
Hember RA, Coops NC, Black TA, RD Guy (2010). Simulating gross primary production across a chronosequence of coastal Douglas-fir forest stands with a production efficiency model Agricultural and Forest Meteorology 150: 238-253
Walia, A, RD Guy, B White (2010). Carbon isotope discrimination in western hemlock and its relationship to mineral nutrition and growth. Tree Physiol 30:728-740
Soolanayakanahally, RY, RD Guy, SN Silim, E Drewes (2009). Enhanced assimilation rate and water use efficiency with latitude through increased photosynthetic capacity and internal conductance in balsam poplar (Populus balsamifera L.). Plant Cell Environ 32:1821–1832
Teste FP, Simard SW, Durall DM, Guy RD, Jones MD, Schoonmaker AL (2009). Access to mycorrhizal networks and tree roots: importance for seedling survival & resource transfer Ecology, 90: 2808-2822
Coleman, H.D., Samuels, A.L., Guy, R. Mansfield, S.D. (2008). Perturbed lignification impacts tree growth in hybrid poplar – a function of sink strength, vascular integrity and photosynthetic assimilation. Plant Physiology. 148:1229-1237.
Hilker, T., N.C. Coops, M.A. Wulder, T.A. Black, and R.D. Guy. (2008). The use of remote sensing in light use efficiency based models of gross primary production: A review of current status and future requirements Science of the Total Environment. 404, 411-423
Schoonmaker, A.L., Teste, F.P., Simard, S.W., Guy, R.D. (2007). Tree proximity, soil pathways and common mycorrhizal networks: their influence on utilization of redistributed water by understory seedlings Oecologia 154:455-466
Jemma L Gornall and Robert D Guy (2007). Geographic variation in ecophysiological traits of black cottonwood (Populus trichocarpa) Can. J. Bot. 85: 1202-1213
Pharis R.P., Russell, J. H., Guy, R. D., Mansfield, S. D., Zhang, R. and Kurepin, L.V. (2007). Enhanced flowering & early progeny testing – Two important tools in tree improvement -A New Era for the Conservation and Utilization of Forest Genetic Resources. Forest Seed Research Ctr, Suanbo, Korea Forest Research Institute, Suwon, Korea. pp 114-140.
Pharis, R.P., Guy, R.D., Mansfield, S. D., Zhang, R., Kurepin, l. V., Fung, L. and Hurst, S. (2006). Retrospective tests – Methods for identifying “inherently” rapid stem gowth capacity for poplar and other forest tree plantations -Proceedings Paper In: Proceedings of the 50th Anniversary of Korea Forest Genetics Researches, pp 93-108. Korea Forest Research Institute, Suwon, Korea, 168 pp.
Baleshta, K.E., S.W. Simard, R.D. Guy and C.P. Chanway (2005). Reducing paper birch density increases Douglas-fir growth and Armillaria root disease incidence in southern interior British Columbia Forest Ecology and Management, 208: 1-13.
Pritchard, E.S., and R.D. Guy (2005). Nitrogen isotope discrimination in white spruce fed with low concentrations of ammonium and nitrate. Trees 19:89-98
Guy, R.D., and G.C. Vanlerberghe (2005). Partitioning of respiratory electrons in the dark in leaves of transgenic tobacco with modified levels of alternative oxidase Physiol Plant 125:171-180
Yu, F-Y, and RD Guy. (2004). Variable chlorophyll fluorescence in response to water plus heat stress treatments in three coniferous tree seedlings. J For Res 15:24-28
Yu, F-Y, X-Z Xu, and RD Guy. (2004). Effects of water plus heat stress on gas exchange and water use efficiency in four species of coniferous seedlings. Scientia Silvae Sinicae 40:38-44
Yu, F-Y, X-Z Xu, and RD Guy. (2004). Effects of water and heat stress on the needle sugar content of four coniferous tree seedlings. J Nanjing Forestry University (Natural Sciences Edition) 28:1-5
Yu, F-Y, X-Z Xu, and RD Guy. (2003). Effects of water and heat stress on the seedling height growth and biomass of five trees. J Nanjing Forestry University (Natural Sciences Edition) 27:10-14
Guy, R.D., and J. Krakowski (2003). Fall colours – Nature’s canvas is a silk parasol Davidsonia 14:111-120
Hoberg, G, R Guy, S Hinch, RA Kozak, P McFarlane and SB Watts (2003). Image and Enrolments Forum 10(6):22-23.
Guy, R.D. and D.L. Holowachuk. (2001). Population differences in stable carbon isotope ratio of Pinus contorta Dougl. ex Loud.: Relationship to environment, climate of origin and growth potential. Can. J. Bot. 79:274-283.
Silim, S.N., R.D. Guy, T.B. Patterson, and N.J. Livingston. (2001). Plasticity in water-use efficiency of Picea sitchensis, P. glauca and their natural hybrids. Oecologia 128:317-325.
Dang, Q.L., T.B. Patterson and R.D. Guy. (2000). Ecophysiological response to interacting effects of drought and nitrogen, and reversibility of drought effect in peatland and upland boreal spruce. -Pp. 187-203 in S.G. Conrad (ed.), Disturbance in Boreal Forest Ecosystems: Human Impacts and Natural Processes. Proc. International Boreal Forest Research Assoc. Ann. Meet., Duluth, MN. USDA Forest Service, General Technical Report NC-209.
Min, X., M.Y. Siddiqi, R.D. Guy, A.D.M. Glass, and H.J. Kronzucker. (2000). A comparative kinetic analysis of nitrate and ammonium influx in two early successional tree species of temperate and boreal forest ecosystems. Plant Cell Environ. 23:321-328.
Benowicz, A., R.D. Guy and Y.A. El-Kassaby. (2000). Geographic pattern of genetic variation in photosynthetic capacity and growth in two hardwood species from British Columbia. Oecologia 123:168-174.
Livingston, N.J., R.D. Guy, Z.J. Sun, and G.J. Ethier. (1999). The effects of nitrogen stress on the stable carbon isotope composition, productivity and water use efficiency of white spruce (Picea glauca (Moench) Voss) seedlings. Plant Cell Environ. 22:281-289.
Min, X., M.Y. Siddiqi, R.D. Guy, A.D.M. Glass, and H.J. Kronzucker. (1999). A comparative study of fluxes and compartmentation of nitrate and ammonium in early successional tree species. Plant Cell Environ. 22:821-830.
Fielding, A.S., D.H. Turpin, R.D. Guy, S.E. Calvert, D. Crawford and P.J. Harrison. (1998). Influence of the carbon concentrating mechanism on carbon stable isotope fractionation by the marine diatom Thalassiosira pseudonana. Can. J. Bot. 76:1098-1103.
Min, X., M.Y. Siddiqi, R.D. Guy, A.D.M. Glass and H.J. Kronzucker. (1998). Induction of nitrate uptake and nitrate reductase activity in trembling aspen and lodgepole pine. Plant Cell Environ. 21:1039-1046.
Silim, S.N., and R.D. Guy. (1998). Influence of thawing duration on performance of conifer seedlings. Pp. 155-162 in Kooistra, C.M. (ed.), Proceedings of the 1995, 1996, and 1997 Annual Meetings of the Forest Nursery Association of British Columbia. FNABC, Vernon, B.C.
Guy, RD, & A Benowicz (1998). Can afforestation contribute to a reduction in Canada’s net CO2 emissions? Report to the Canadian Pulp & Paper Association. 17 p.
Patterson, T.B., R.D. Guy and Q.L. Dang. (1997). Whole-plant nitrogen- and water-relations traits, and their associated trade-offs, in adjacent muskeg and upland boreal spruce species. Oecologia 110:160-168.
Ribas-Carbo, M., L. Giles, R.D. Guy, S.A. Robinson, J.N. Siedow and J.A. Berry. (1997). O2 isotope fractionation technique for studies on plant mitochondrial respiration. Mini-review. International Cyber Conference on Analytical BioSciences, Hiroshima, Japan. Trends in Analytical Life Sciences vol.1 issue No. 24 (electronic publication)
Brown, K.R., W.A. Thompson, E.L. Camm, B.J. Hawkins and R.D. Guy. (1996). Effects of N addition rates on the productivity of Picea sitchensis, Thuja plicata, and Tsuga heterophylla seedlings. II. Photosynthesis, 13C discrimination and N partitioning in foliage. Trees 10:198-205.
Camm, E, RD Guy, DS Kubien, D Goetze, S Silim & PJ Burton (1995). Physiological recovery of freezer-stored white and Engelmann spruce seedlings planted following different thawing regimes. New Forests 10:57-77
Dang, QL, CY Xie, C Ying & RD Guy (1994). Genetic variation of ecophysiological traits in red alder (Alnus rubra Bong.) Can J For Res 24:2150-2156
Chomba, BC, RD Guy & HG Weger (1993). Carbohydrate reserve accumulation and depletion in cold-stored Engelmann spruce (Picea engelmannii Parry) and the effects of pre-storage CO2 enrichment Tree Physiol 13:351-364
Weger, HG, SN Silim & RD Guy (1993). Photosynthetic acclimation to low temperature by western red cedar seedlings Plant Cell Environ 16:711-717
Guy, RD, ML Fogel & JA Berry (1993). Photosynthetic fractionation of the stable isotopes of oxygen and carbon Plant Physiol 101:37-47
Guy, RD, JA Berry, ML Fogel, DH Turpin & HG Weger (1992). Fractionation of the stable isotopes of oxygen during respiration by plants – the basis of a new technique to estimate partitioning to the alternative path SPB Academic Publishing, The Hague Molecular, Biochemical and Physiological Aspects of Plant Respiration. pp 443-453
Weger, HG, GC Vanlerberghe, RD Guy & DH Turpin (1992). Respiratory carbon flow to nitrogen assimilation SPB Academic Publishing, The Hague Molecular, Biochemical and Physiological Aspects of Plant Respiration. pp 149-165
Weger, HG, & RD Guy (1991). Cytochrome and alternative pathway respiration in white spruce (Picea glauca [Moench] Voss) roots. Effects of growth and measurement temperature Physiol Plant 83:675-681
Turpin, DH, GC Vanlerberghe, AM Amory & RD Guy (1991). The inorganic carbon requirements for nitrogen assimilation Can J Bot 69:1139-1145
Weger, HG, AR Chadderton, M Lin, RD Guy & DH Turpin (1990). Cytochrome and alternative pathway respiration during transient ammonium assimilation by N-limited Chlamydomonas reinhardtii Plant Physiol 94:1131-1136
Weger, HG, RD Guy & DH Turpin (1990). Cytochrome and alternative pathway respiration in green algae. Measurements using inhibitors and 18O2 discrimination Plant Physiol 93:356-360
Warne, P, RD Guy, L Rollins & DM Reid (1990). The effects of sodium sulphate and sodium chloride on growth, morphology, photosynthesis and water use efficiency of Chenopodium rubrum Can J Bot 68:999-1006
Guy, RD, GC Vanlerberghe & DH Turpin (1989). The significance of phosphoenolpyruvate carboxylase during ammonium assimilation. Carbon isotope discrimination in photosynthesis and respiration by the N-limited green alga Selenastrum minutum Plant Physiol 89:1150-1157
Guy, RD, JA Berry, ML Fogel & TC Hoering (1989). Differential fractionation of oxygen isotopes by cyanide-resistant and cyanide-sensitive respiration in plants Planta 177:483-491
Guy, RD, PG Warne & DM Reid (1989). Stable carbon isotope ratio as an index of water-use efficiency in C3 halophytes – Possible relationship to strategies for osmotic adjustment Springer-Verlag, NY Stable Isotopes in Ecological Research. pp 55-75