Earth’s vast forests provide human communities with irreplaceable goods and services such as carbon sequestration, hydrologic regulation, clean water, biodiversity, critical wildlife habitat, wood products, and recreational and spiritual opportunities. An overarching goal of Dr. Nathan Stephenson's research is to improve scientists' and land managers' ability to understand, forecast, and adapt to the effects of ongoing global changes – particularly changing climatic and disturbance regimes – on forests. Accordingly, most of his research falls in three broad, complementary themes: (1) improving mechanistic understanding of forest and carbon dynamics, (2) detection, attribution, and interpretation of forest changes, and (3) adaptations to rapid global changes. The last theme extends well beyond forests, to natural areas in general.
- Forest ecology
- Global change biology
- Climate change
- Fire ecology
- Natural areas management
- Ph.D., Ecology and Systematics, Cornell University, 1988
- B.S., Biological Sciences, University of California, Irvine, 1979
Science and Products
Improving estimates of tree mortality probability using potential growth rate
Tree growth rate is frequently used to estimate mortality probability. Yet, growth metrics can vary in form, and the justification for using one over another is rarely clear. We tested whether a growth index (GI) that scales the realized diameter growth rate against the potential diameter growth rate (PDGR) would give better estimates of mortality...Das, Adrian J.; Stephenson, Nathan L.
Making the transition to the third era of natural resources management
We are entering the third era of National Park Service (NPS) natural resources management— an era defined by rapid and unprecedented global changes. This third era promises to overturn not only some of our most fundamental assumptions about parks and protected areas, but also many of the ideals we currently hold dear. A common initial...Stephenson, Nathan L.
Beyond reducing fire hazard: fuel treatment impacts on overstory tree survival
Fuel treatment implementation in dry forest types throughout the western United States is likely to increase in pace and scale in response to increasing incidence of large wildfires. While it is clear that properly implemented fuel treatments are effective at reducing hazardous fire potential, there are ancillary ecological effects that can impact...Collins, Brandon M.; Das, Adrian J.; Battles, John J.; Fry, Danny L.; Krasnow, Kevin D.; Stephens, Scott L.
Rate of tree carbon accumulation increases continuously with tree size
Forests are major components of the global carbon cycle, providing substantial feedback to atmospheric greenhouse gas concentrations. Our ability to understand and predict changes in the forest carbon cycle—particularly net primary productivity and carbon storage - increasingly relies on models that represent biological processes across several...Stephenson, N.L.; Das, A.J.; Condit, R.; Russo, S.E.; Baker, P.J.; Beckman, N.G.; Coomes, D.A.; Lines, E.R.; Morris, W.K.; Rüger, N.; Álvarez, E.; Blundo, C.; Bunyavejchewin, S.; Chuyong, G.; Davies, S.J.; Duque, Á.; Ewango, C.N.; Flores, O.; Franklin, J.F.; Grau, H.R.; Hao, Z.; Harmon, M.E.; Hubbell, S.P.; Kenfack, D.; Lin, Y.; Makana, J.-R.; Malizia, A.; Malizia, L.R.; Pabst, R.J.; Pongpattananurak, N.; Su, S.-H.; Sun, I-F.; Tan, S.; Thomas, D.; van Mantgem, P.J.; Wang, X.; Wiser, S.K.; Zavala, M.A.
Climatic correlates of tree mortality in water- and energy-limited forests
Recent increases in tree mortality rates across the western USA are correlated with increasing temperatures, but mechanisms remain unresolved. Specifically, increasing mortality could predominantly be a consequence of temperature-induced increases in either (1) drought stress, or (2) the effectiveness of tree-killing insects and pathogens. Using...Das, Adrian J.; Stephenson, Nathan L.; Flint, Alan; Das, Tapash; van Mantgem, Phillip J.
A natural resource condition assessment for Sequoia and Kings Canyon National Parks: Appendix 22: climatic change
Climate is a master controller of the structure, composition, and function of biotic communities, affecting them both directly, through physiological effects, and indirectly, by mediating biotic interactions and by influencing disturbance regimes. Sequoia and Kings Canyon National Park’s (SEKI’s) dramatic elevational changes in biotic...Das, Adrian J.; Stephenson, Nathan L.
A natural resource condition assessment for Sequoia and Kings Canyon National Parks: Appendix 11a: giant sequoias
For natural resource managers in the southern Sierra Nevada, giant sequoia requires very little introduction. It receives great attention as an icon of western forests and as a common namesake with the areas where it occurs. While it is a single component of a very complex system, its attention in this assessment and in general is well deserved...York, Robert A.; Stephenson, Nathan L.; Meyer, Marc; Hanna, Steve; Tadashi, Moody; Caprio, Anthony C.; Battles, John J.
Response of western mountain ecosystems to climatic variability and change: A collaborative research approach
No abstract available.Beever, Erik A.; Belant, Jerrold L.; Peterson, David L.; Allen, Craig D.; Baron, Jill S.; Fagre, Daniel B.; McKenzie, Donald; Stephenson, Nathan L.; Fountain, Andrew G.; Hicke, Jeffrey A.; Malanson, George P.; Ojima, Dennis S.; Tague, Christina L.; van Mantgem, Phillip J.
Causes and implications of the correlation between forest productivity and tree mortality rates
At global and regional scales, tree mortality rates are positively correlated with forest net primary productivity (NPP). Yet causes of the correlation are unknown, in spite of potentially profound implications for our understanding of environmental controls of forest structure and dynamics and, more generally, our understanding of broad-scale...Stephenson, Nathan L.; van Mantgem, Philip J.; Bunn, Andrew G.; Bruner, Howard; Harmon, Mark E.; O'Connell, Kari B.; Urban, Dean L.; Franklin, Jerry F.
Comment on "Changes in climatic water balance drive downhill shifts in plant species' optimum elevations"
Crimmins et al. (Reports, 21 January 2011, p. 324) attributed an apparent downward elevational shift of California plant species to a precipitation-induced decline in climatic water deficit. We show that the authors miscalculated deficit, that the apparent decline in species' elevations is likely a consequence of geographic biases, and that unlike...Stephenson, Nathan L.; Das, Adrian J.
Long-term effects of prescribed fire on mixed conifer forest structure in the Sierra Nevada, California
The capacity of prescribed fire to restore forest conditions is often judged by changes in forest structure within a few years following burning. However, prescribed fire might have longer-term effects on forest structure, potentially changing treatment assessments. We examined annual changes in forest structure in five 1 ha old-growth plots...van Mantgem, Phillip J.; Stephenson, Nathan L.; Knapp, Eric; Keeley, Jon E.
The contribution of competition to tree mortality in old-growth coniferous forests
Competition is a well-documented contributor to tree mortality in temperate forests, with numerous studies documenting a relationship between tree death and the competitive environment. Models frequently rely on competition as the only non-random mechanism affecting tree mortality. However, for mature forests, competition may cease to be the...Das, A.; Battles, J.; Stephenson, N.L.; van Mantgem, P.J.