Professor Stephen C. Sillett

Current research

Understanding Elder Redwoods— This study combines terrestrial and airborne laser scanning with ground-based measurements to inventory all Sequoia sempervirens > 200 Mg biomass in Redwood National and State Parks, improving how forest biomass and canopy structure are quantified and developing a botanical archive useful for conservation. We document the natural progress of Sequoia decline from peak biomass through structural collapse to understand the full arc of life for the species. A very small subset of trees are measured intensively to identify the most important factors limiting accumulation of arboreal biodiversity. Tree-ring samples collected during measurements are crossdated and curated by Allyson L. Carroll (allyson.carroll@gmail.com) and used to quantify tree ages and elucidate fire history.

Extended sampling to help CalFire manage Sequoia resources— This study compares Sequoia performance characteristics (size, biomass production, growth efficiency) in three State Forests (Jackson, Soquel, Las Posadas) to similar forests across the species range. New tools and workflows are being developed to extract tree structure variables from high-resolution laser scanning for quantifying forest biomass and identifying potential elder trees. This work will improve allometric estimation of tree biomass and productivity and promote conservation of Sequoia resources in forests managed by CalFire.

Publications(reverse chronological order)

Carroll, A.L., S.C. Sillett. 2024. Updated dendrochronology and axial variation of climatic sensitivity in Sequoiadendron giganteum. Trees, https://doi.org/10.1007/s00468-024-02517-6

Sillett, S.C., M.E. Graham, J.P. Montague, M.E. Antoine, G.W. Koch. 2024. Ground-based calibration for remote sensing of biomass in the tallest forests. Forest Ecology and Management 561: 121879.

Carroll, A.L., S.C. Sillett. 2023. Overcoming crossdating challenges to generate ring-width chronologies for Sequoia sempervirens across its native range. Dendrochronologia 78: 126063.

Sillett, S.C., M.E. Antoine, A.L. Carroll, M.E. Graham, A.R.O. Chin, R. Van Pelt. 2022. Rangewide climatic sensitivities and non-timber values of tall Sequoia sempervirens forests. Forest Ecology and Management 526: 120573.

Antoine, M.E., S.C. Sillett. 2022. Intentional forests: growing hope for the future. International Dendrology Society Yearbook 2021, pp. 55-67.

Chin, A.R.O., P. Guzmán-Delgado, S.C. Sillett, L.P. Kerhoulas, A.R. Ambrose, A.R. McElrone, M.A. Zwieniecki. 2022. Tracheid buckling buys time, foliar water uptake pays it back: coordination of leaf structure and function in tall redwood trees. Plant, Cell & Environment 45: 2607-2616.

Chin, A.R.O., P. Guzmán-Delgado, S.C. Sillett, J. Orozco, R.D. Kramer, L.P. Kerhoulas, Z.J. Moore, M. Reed, M. Zwieniecki. 2022. Shoot dimorphism enables Sequoia sempervirens to separate requirements for foliar water uptake and photosynthesis. American Journal of Botany 109: 564-579.

Sillett, S.C., R.D. Kramer, R. Van Pelt, A.L. Carroll, J. Campbell-Spickler, M.E. Antoine. 2021. Comparative development of the four tallest conifer species. Forest Ecology and Management 480: 118688.

Kramer, R.D., S.C. Sillett, V.R. Kane, J.F. Franklin. 2020. Disturbance and species composition drive canopy structure and distribution of large trees in Olympic rainforests, USA. Landscape Ecology 35: 1107–1125.

Sillett, S.C., R. Van Pelt, A.L. Carroll, J. Campbell-Spickler, M.E. Antoine. 2020. Aboveground biomass dynamics and growth efficiency of Sequoia sempervirens. Forest Ecology and Management 458: 117740.

Iberle, B.G., R. Van Pelt, S.C. Sillett. 2020. Development of mature second-growth Sequoia sempervirens forests. Forest Ecology and Management 459: 117816.

Chin, A.R.O., S.C. Sillett. 2019. Within-crown plasticity in leaf traits among the tallest conifers. American Journal of Botany 106: 1–13.

Kramer, R.D., S.C. Sillett, R. Van Pelt, J.F. Franklin. 2019. Neighborhood competition mediates crown development of Picea sitchensis in Olympic rainforests: implications for restoration management. Forest Ecology and Management 441: 127–143.

Sillett, S.C., Van Pelt, R., Carroll, A.L., Campbell-Spickler, J., Antoine, M.E., 2019. Structure and dynamics of forests dominated by Sequoiadendron giganteum. Forest Ecology and Management 448: 218–239.

Sillett, S.C., R. Van Pelt, A.L. Carroll, J. Campbell-Spickler, E.J. Coonen, B. Iberle. 2019. Allometric equations for Sequoia sempervirens in forests of different ages. Forest Ecology and Management 433: 349–363.

Kramer, R.D., S.C. Sillett, R. Van Pelt. 2018. Quantifying aboveground components of Picea sitchensis for allometric comparisons among tall conifers in North American rainforests. Forest Ecology and Management 430: 59–77.

Sillett, S.C., R. Van Pelt, J.A. Freund, J. Campbell-Spickler, A.L. Carroll, R.D. Kramer. 2018. Development and dominance of Douglas-fir in North American rainforests. Forest Ecology and Management 429: 93–114.

Sillett, S.C., M.E. Antoine, J. Campbell-Spickler, A.L. Carroll, E.J. Coonen, R.D. Kramer, K.H. Scarla. 2018. Manipulating tree crown structure to promote old-growth characteristics in second-growth redwood forest canopies. Forest Ecology and Management 417: 77–89.

Chin, A.R.O., S.C. Sillett. 2017. Leaf acclimation to light availability supports rapid growth in tall Picea sitchensis trees. Tree Physiology 37: 1352–1366.

Ishii, H.R., S.C. Sillett, A.L. Carroll. 2017. Crown dynamics and wood production of Douglas-fir trees in an old-growth forest. Forest Ecology and Management 384: 157–168.

Chin, A.R.O, S.C. Sillett. 2016. Phenotypic plasticity of leaves enhances water-stress tolerance and promotes hydraulic conductivity in a tall conifer. American Journal of Botany 103: 796–807.

Van Pelt, R., S.C. Sillett, W.A. Kruse, J.A. Freund, R.D. Kramer. 2016. Emergent crowns and light-use complementarity lead to global maximum biomass and leaf area in Sequoia sempervirens forests. Forest Ecology and Management 375: 279–308.

Coonen, E.J., S.C. Sillett. 2015. Separating effects of crown structure and competition for light on trunk growth of Sequoia sempervirens. Forest Ecology and Management 358: 26–40.

Sillett, S.C., R. Van Pelt, A.L. Carroll, R.D. Kramer, A.R. Ambrose, D. Trask. 2015. How do tree structure and old age affect growth potential of California redwoods? Ecological Monographs 85: 181–212.

Sillett, S.C., R. Van Pelt, R.D. Kramer, A.L. Carroll, G.W. Koch. 2015. Biomass and growth potential of Eucalyptus regnans up to 100 m tall. Forest Ecology and Management 348: 78–91.

Koch, G.W., S.C. Sillett, M.E. Antoine, C.B. Williams. 2015. Growth maximization trumps maintenance of leaf conductance in the tallest angiosperm. Oecologia 177: 321–331.

Kramer, R.D., S.C. Sillett, A.L. Carroll. 2014. Structural development of redwood branches and its effects on wood growth. Tree Physiology 34: 314–330.

Ishii, H., W. Azuma, K. Kuroda, S.C. Sillett. 2014. Pushing the limits to tree height: could foliar water storage compensate for hydraulic constraints in Sequoia sempervirens? Functional Ecology 28: 1087–1093.

Carroll, A.L., S.C. Sillett, R.D. Kramer. 2014. Millennium-scale crossdating and inter-annual climate sensitivities of standing California redwoods. PLOS ONE 9: 1–18.

Kennedy, J.-P., S.C. Sillett, J.M. Szewczak. 2014. Bat activity across the vertical gradient of an old-growth Sequoia sempervirens forest. Acta Chiropterologica 16: 53–63.

Sillett, S.C., R. Van Pelt, G.W. Koch, A.R. Ambrose, A.L. Carroll, B.M. Mifsud. 2010. Increasing wood production through old age in tall trees. Forest Ecology and Management 259: 976–994. 

Ambrose, A.R., S.C. Sillett, G.W. Koch, R. Van Pelt, M.E. Antoine, T.E. Dawson. 2010. Effects of height on treetop transpiration and stomatal conductance in coast redwood (Sequoia sempervirens). Tree Physiology 30: 1260–1272.

Oldham, A.R., S.C. Sillett, A.M.F. Tomescu, G.W. Koch. 2010. The hydrostatic gradient, not light availability, drives height-related variation in Sequoia sempervirens leaf anatomy. American Journal of Botany 97: 1–12.

Enloe, H.A., S.A. Quideau, R.C. Graham, S.C. Sillett, S.-W. Oh, R.E. Wasylishen. 2010. Soil organic matter processes in old-growth redwood forest canopies. Soil Science Society of America Journal 74: 161–171.

Mullin, L.P., S.C. Sillett, G.W. Koch, K.P. Tu, M.E. Antoine. 2009. Physiological consequences of height-related variation in Sequoia sempervirens foliage. Tree Physiology 29: 999–1010.

Ambrose, A.R., S.C. Sillett, T.E. Dawson. 2009. Effects of tree height on branch hydraulics, leaf structure and gas exchange in California redwoods. Plant, Cell & Environment 32: 743–757.

Koch, G.W., S.C. Sillett. 2009. A response to: Limitations within “The Limits to Tree Height.” American Journal of Botany 96: 545–547.

Van Pelt, R., S.C. Sillett. 2008. Crown development throughout the lifespan of coastal Pseudotsuga menziesii, including a conceptual model for tall conifers. Ecological Monographs 78: 283–311.

Woolley, L.P., T.W. Henkel, S.C. Sillett. 2008. Reiteration in the monodominant tropical tree Dicymbe corymbosa and its potential adaptive significance. Biotropica 40: 32–43.

Ishii, H.T., G.M. Jennings, S.C. Sillett, G.W. Koch. 2008. Hydrostatic constraints on morphological exploitation of light in tall Sequoia sempervirens trees.  Oecologia 156: 751–763.

Sillett, S.C., R. Van Pelt. 2007. Trunk reiteration promotes epiphytes and water storage in an old-growth redwood forest canopy. Ecological Monographs 77: 335–359.

Williams, C.B., S.C. Sillett. 2007. Epiphyte communities on redwood (Sequoia sempervirens) in northwestern California, USA. Bryologist 110: 420–452.

Spickler, J.C., S.C. Sillett, S.B. Marks, H.H. Welsh Jr. 2006. Evidence of a new niche for a North American salamander: Aneides vagrans residing in the canopy of old-growth redwood forest. Herpetological Conservation and Biology 1: 16–27.

Enloe, H.A., R.C. Graham, S.C. Sillett. 2006. Arboreal histosols in old-growth redwood forest canopies, northern California. Soil Science Society of America Journal 70: 408–418.

Sillett, S.C., and M.E. Antoine. 2004. Lichens and bryophytes in forest canopies. Pages 151–174 in M.D. Lowman, H.B. Rinker (eds.), Forest Canopies, 2^nd Edition. Elsevier Academic Press.

Van Pelt, R., S.C. Sillett, N.M. Nadkarni. 2004. Quantifying and visualizing canopy structure in tall forests: methods and a case study. Pages 49–72 in M.D. Lowman and H.B. Rinker (eds.), Forest Canopies, 2^nd Edition. Elsevier Academic Press.

Koch, G.W., S.C. Sillett, G.M. Jennings, S.D. Davis. 2004. The limits to tree height. Nature 428: 851–854. 

Dial, R.J., S.C. Sillett, M.E. Antoine, J.C. Spickler. 2004. Methods for horizontal movement through forest canopies. Selbyana 25: 151–163.

Ellyson, W.J.T., S.C. Sillett. 2003. Epiphyte communities on Sitka spruce in an old-growth redwood forest. Bryologist 106: 197–211.

Sillett, S.C., M.G. Bailey. 2003. Effects of tree crown structure on biomass of the epiphytic fern Polypodium scouleri in redwood forests. American Journal of Botany 90: 255–261

Sillett, S.C., R. Van Pelt. 2001. A redwood tree whose crown may be the most complex on Earth. Pages 11–18 in M. Labrecque (ed.), L’Arbre 2000. Isabelle Quentin, Montréal, Québec.

Sillett, S.C., R. Van Pelt. 2000. A redwood tree whose crown is a forest canopy. Northwest Science 74: 34–43.

Sillett, S.C., T.R. Rambo. 2000. Vertical distribution of dominant epiphytes in Douglas-fir forests of the central Oregon Cascades. Northwest Science 74: 44–49.

Sillett, S.C., B. McCune, J.E. Peck, T.R. Rambo. 2000. Four years of epiphyte colonization in Douglas-fir forest canopies. Bryologist 103: 661–669.

Sillett, S.C., B. McCune, J.E. Peck, T.R. Rambo, A. Ruchty. 2000. Dispersal limitations of epiphytic lichens result in species dependent on old-growth forests. Ecological Applications 10: 789–799.

Sawyer, J.O., S.C. Sillett, J.H. Popenoe, A. LaBanca, T. Sholars, D.L. Largent, F.Euphrat, R.F. Noss, R. Van Pelt. 2000. Characteristics of redwood forests. Pages 39–79 in R.F. Noss (ed.), The Redwood Forest: History, Ecology, and Conservation of the Coast Redwoods. Island Press, Covelo, CA.

Sawyer, J.O., S.C. Sillett, W.J. Libby, T.E. Dawson, J.H. Popenoe, D.L. Largent, R. Van Pelt, S.D. Veirs Jr., R.F. Noss, D.A. Thornburgh, P.D. Tredici. 2000. Redwood trees, communities, and ecosystems: a closer look. Pages 81–118 in R.F. Noss (ed.), The Redwood Forest: History, Ecology, and Conservation of the Coast Redwoods. Island Press, Covelo, CA.

Sillett, S.C. 1999. Tree crown structure and vascular epiphyte distribution in Sequoia sempervirens rain forest canopies. Selbyana 20: 76–97.

Sillett, S.C., M.N. Goslin. 1999. Distribution of epiphytic macrolichens in relation to remnant trees in a Douglas-fir forest. Canadian Journal of Forest Research 29: 1204–1215.

Sillett, S.C., T. Goward. 1998. Ecology and conservation of Pseudocyphellaria rainierensis, a Pacific Northwest endemic lichen. Pages 377–388 in M.G. Glenn, R.C. Harris, R. Dirig, M. S. Cole (eds.), Lichenographia Thomsoniana. Mycotaxon Ltd., Ithaca, NY.

Sillett, S.C., B. McCune. 1998. Survival and growth of cyanolichen transplants in Douglas-fir forest canopies. Bryologist 101: 20–31.

Sillett, S.C. 1997. Distribution and ecology of Pseudocyphellaria rainierensis, an epiphytic cyanolichen endemic to the Pacific Northwest. Pages 254–260 in T.N. Kaye, A. Liston, R.M. Love, D.L. Luoma, R.J. Meinke, M.V. Wilson (eds.), Conservation and Management of Native Plants and Fungi. Native Plant Society of Oregon, Corvallis, OR.

Sillett, S.C., P.N. Neitlich. 1996. Emerging themes in epiphyte research in westside forests with special reference to cyanolichens. Northwest Science 70: 54–60.

McCune, B., C.C. Derr, P.S. Muir, A.S. Shirazi, S.C. Sillett, W.J. Daly. 1996. Lichen pendants for transplant and growth experiments. Lichenologist 28: 161–169.

Sillett, S.C. 1995. Branch epiphyte assemblages in the forest interior and on the clearcut edge of a 700-year-old forest canopy in western Oregon. Bryologist 98: 301–312.

Sillett, S.C., S.R. Gradstein, D. Griffin III. 1995. Bryophyte diversity of Ficus tree crowns from cloud forest and pasture in Costa Rica. Bryologist 98: 251–260.

Sillett, S.C. 1994. Growth rates of two epiphytic cyanolichen species at the edge and in the interior of a 700-year-old Douglas-fir forest in the western Cascades of Oregon. Bryologist 97: 321–324.