Adrian Das
Biography
I am an Ecologist with the U.S. Geological Survey's Western Ecological Research Center, stationed at Sequoia and Kings Canyon National Parks. I study tree dynamics with a particular focus on tree mortality processes. My work is aimed at improving our understanding of western forests and increasing our capacity to assess how they will be affected by a changing climate.
RESEARCH INTERESTS
- Forest ecology
- Forest dynamics
- Tree mortality
- Tree growth
- Climatic change
EDUCATION
PhD from University of California at Berkeley, Forest Ecology 2007
BS from University of Michigan, Chemistry and Cellular Molecular Biology, 1995
Science and Products
Forest health and drought response
Forests provide society with economically important and often irreplaceable goods and services, such as wood products, carbon sequestration, clean water, biodiversity, and recreational opportunities. Yet hotter droughts (droughts in which unusually high temperatures exacerbate the effects of low precipitation) are projected to increase in frequency and intensity in coming decades, potentially...
Post-Fire Conifer Regeneration Under a Warming Climate: Will Severe Fire Be a Catalyst for Forest Loss?
The Southwest U.S. is experiencing hotter droughts, which are contributing to more frequent, severe wildfires. These droughts also stress vegetation, which can make it more difficult for forests to recover after fire. Forest regeneration in burned areas may be limited because seeds have to travel long distances to recolonize, and when they do arrive, conditions are often unfavorably hot and...
Fighting Drought with Fire: A Comparison of Burned and Unburned Forests in Drought-Impacted Areas of the Southwest
Drought is one of the biggest threats facing our forests today. In the western U.S., severe drought and rising temperatures have caused increased tree mortality and complete forest diebacks. Forests are changing rapidly, and while land managers are working to develop long-term climate change adaptation plans, they require tools that can enhance forest resistance to drought now. To address this...
Characterizing a link in the terrestrial carbon cycle: a global overview of individual tree mass growth
Forests sequester the majority of the terrestrial biosphere’s carbon and are key components of the global carbon cycle, potentially contributing substantial feedbacks to ongoing climatic changes. It is therefore remarkable that no consensus yet exists about the fundamental nature of tree mass growth (and thus carbon sequestration rate). Specifically, does tree mass growth rate increase,...
Mortality predispositions of conifers across western USA
Conifer mortality rates are increasing in western North America, but the physiological mechanisms underlying this trend are not well understood.We examined tree‐ring‐based radial growth along with stable carbon (C) and oxygen (O) isotope composition (δ13C and δ18O, respectively) of dying and surviving conifers at eight old‐growth forest sites...
Wang, Wenzhi; English, Nathan B.; Grossiord, Charlotte; Gessler, Arthur; Das, Adrian; Stephenson, Nathan L.; Baisan, Christopher H.; Allen, Craig D.; McDowell, Nate G. Height-related changes in forest composition, not tree vulnerability, explain increasing mortality with height during an extreme drought
Recently, Stovall et al.1 (hereafter SSY) showed that during an extreme drought, remotely sensed mortality of tall trees was more than double that of short trees. They interpreted this to be a consequence of inherently greater hydraulic vulnerability of tall trees, and suggested that tall-tree vulnerability should thus generalize more broadly....
Stephenson, Nathan L.; Das, Adrian The Fire and Tree Mortality Database, for empirical modeling of individual tree mortality after fire
Wildland fires have a multitude of ecological effects in forests, woodlands, and savannas across the globe. A major focus of past research has been on tree mortality from fire, as trees provide a vast range of biological services. We assembled a database of individual-tree records from prescribed fires and wildfires in the United States. The Fire...
Cansler, C. Alina; Hood, Sharon M.; Varner, J. Morgan; van Mantgem, Phillip J.; Agne, Michelle C.; Andrus, Robert A.; Ayres, Matthew P.; Ayres, Bruce D.; Bakker, Jonathan D.; Battaglia, Michael A.; Bentz, Barbara J.; Breece, Carolyn R.; Brown, James K.; Cluck, Daniel R.; Coleman, Tom W.; Corace, R. Gregory; Covington, W. Wallace; Cram, Douglas S.; Cronan, James B.; Crouse, Joseph E.; Das, Adrian; Davis, Ryan S.; Dickinson, Darci M.; Fitzgerald, Stephen A; Fule, Peter Z.; Ganio, Lisa M.; Grayson, Lindsay M.; Halpern, Charles B.; Hanula, Jim L.; Harvey, Brian J.; Hiers, J. Kevin; Huffman, David W.; Keifer, MaryBeth; Keyser, Tara L.; Kobziar, Leda N.; Kolb, Thomas E.; Kolden, Crystal A.; Kopper, Karen E.; Kreitler, Jason R.; Kreye, Jesse K.; Latimer, Andrew M.; Lerch, Andrew P.; Lombardero, Maria J.; McDaniel, Virginia L.; McHugh, Charles W.; McMillin, Joel D.; Moghaddas, Jason J.; O'Brien, Joseph J.; Perrakis, Daniel D. B.; Peterson, David W.; Pritchard, Susan J.; Progar, Robert A.; Raffa, Kenneth F.; Reinhardt, Elizabeth D.; Restaino, Joseph C.; Roccaforte, John P.; Rogers, Brendan M.; Ryan, Kevin C.; Safford, Hugh D.; Santoro, Alyson E.; Shearman, Timothy M.; Shumate, Alice M.; Sieg, Carolyn H.; Smith, Sheri L.; Smith, Rebecca J.; Stephenson, Nathan L.; Stuever, Mary; Stevens, Jens; Stoddard, Michael T.; Thies, Walter G.; Vaillant, Nicole M.; Weiss, Shelby A.; Westlind, Douglas J.; Woolley, Travis J; Wright, Micah Charles Coming to terms with the new normal: Forest health in the Sierra Nevada
The vast conifer forests of California’s Sierra Nevada range inspire awe and create lasting memories. The size and longevity of these trees make them seem both otherworldly and everlasting. Indeed, their grandeur is such that visitors may not appreciate how these forests are connected to the larger landscape, and so there is little understanding...
Axelson, Jodi; Battles, John J.; Das, Adrian J.; van Mantgem, Phillip J. The influence of pre-fire growth patterns on post-fire tree mortality for common conifers in western U.S. parks
Fire severity in forests is often defined in terms of post-fire tree mortality, yet the influences on tree mortality following fire are not fully understood. For trees that are not killed immediately by severe fire injury, pre-fire growth may partially predict post-fire mortality probabilities for conifers of the western U.S. Here, we consider the...
van Mantgem, Phillip; Falk, Donald A.; Williams, Emma C.; Das, Adrian J.; Stephenson, Nathan L. Tree mortality in blue oak woodland during extreme drought in Sequoia National Park, California
Blue oak woodlands in California have been a focus of conservation concern for many years. Numerous studies have found that existing seedling and sapling numbers are inadequate to sustain current populations, and recent work has suggested that blue oak woodlands might be particularly vulnerable to a warming climate. California has recently...
Das, Adrian J.; Ampersee, Nicholas J.; Pfaff, Anne Hopkins; Stephenson, Nathan L.; Swiecki, Tedmund J; Bernhardt, Elizabeth A; Haggerty, Patricia; Nydick, Koren R. Size matters, but not consistently
E. Pennisi (“Forest giants are the trees most at risk,” News, 6 September, p. 962) interprets presentations of three studies as suggesting that “for trees, size is not strength, and forest giants are disproportionately vulnerable.” However, this conclusion is not well supported. The observation that lightning is a major cause of large-tree...
Stephenson, Nathan L.; Das, Adrian J. Negative impacts of summer heat on Sierra Nevada tree seedlings
Understanding the response of forests to climate change is important for predicting changes in biodiversity and ecosystem services, including carbon storage. Seedlings represent a key demographic stage in these responses, because seedling establishment is necessary for population persistence and spread, and because the conditions allowing...
Moran, Emily V; Das, Adrian J.; Keeley, Jon; Stephenson, Nathan L. Which trees die during drought? The key role of insect host-tree selection
1. During drought, the tree subpopulations (such as size or vigor classes) that suffer disproportionate mortality can be conceptually arrayed along a continuum defined by the actions of biotic agents, particularly insects. At one extreme, stress dominates: insects are absent or simply kill the most physiologically stressed trees. At the...
Stephenson, Nathan L.; Das, Adrian J.; Ampersee, Nicholas J.; Bulaon, Beverly M; Yee, Julie L. Early-warning signals of individual tree mortality based on annual radial growth
Tree mortality is a key driver of forest dynamics and its occurrence is projected to increase in the future due to climate change. Despite recent advances in our understanding of the physiological mechanisms leading to death, we still lack robust indicators of mortality risk that could be applied at the individual tree scale. Here, we build on a...
Cailleret, Maxime; Dakos, Vasilis; Jansen, Steven; Robert, Elisabeth M. R.; Aakala, Tuomas; Amoroso, Mariano M.; Antos, Joe A.; Bigler, Christof; Bugmann, Harald; Caccianaga, Marco; Camarero, Jesus-Julio; Cherubini, Paolo; Coyea, Marie R.; Cufar, Katarina; Das, Adrian J.; Davi, Hendrik; Gea-Izquierdo, Guillermo; Gillner, Sten; Haavik, Laurel J.; Hartmann, Henrik; Heres, Ana-Maria; Hultine, Kevin R.; Janda, Pavel; Kane, Jeffrey M.; Kharuk, Viachelsav I.; Kitzberger, Thomas; Klein, Tamir; Levanic, Tom; Linares, Juan-Carlos; Lombardi, Fabio; Makinen, Harri; Mészáros, Ilona; Metsaranta, Juha M.; Oberhuber, Walter; Papadopoulos, Andreas; Petritan, Any Mary; Rohner, Brigitte; Sanguesa-Barreda, Gabriel; Smith, Jeremy M.; Stan, Amanda B.; Stojanovic, Dejan B.; Suarez, Maria-Laura; Svoboda, Miroslav; Trotsiuk, Volodymyr; Villalba, Ricardo; Westwood, Alana R.; Wyckoff, Peter H.; Martinez-Vilalta, Jordi Pre‐fire drought and competition mediate post‐fire conifer mortality in western U.S. National Parks
Tree mortality is an important outcome of many forest fires. Extensive tree injuries from fire may lead directly to mortality, but environmental and biological stressors may also contribute to tree death. However, there is little evidence showing how the combined effects of two common stressors, drought and competition, influence post‐fire...
van Mantgem, Phillip J.; Falk, Donald A.; Williams, Emma C.; Das, Adrian J.; Stephenson, Nathan L. Leaf to landscape responses of giant sequoia to hotter drought: An introduction and synthesis for the special section
Hotter droughts are becoming more common as climate change progresses, and they may already have caused instances of forest dieback on all forested continents. Learning from hotter droughts, including where on the landscape forests are more or less vulnerable to these events, is critical to help resource managers proactively prepare for the future...
Nydick, Koren R.; Stephenson, Nathan L.; Ambrose, Anthony R.; Asner, Gregory P.; Baxter, Wendy L.; Das, Adrian J.; Dawson, Todd E.; Martin, Roberta E.; Paz-Kagan, Tarin
Investigating drivers of tree mortality in western forests
This article is part of the Spring 2017 issue of the Earth Science Matters Newsletter.