Natural climatic variability, including episodic droughts, has long been known to trigger accelerated tree mortality in forests worldwide, including in the Southwest U.S. Scientific understanding of the process drivers and spatial patterns of tree mortality is surprisingly limited, constraining our ability to model forest responses to projected climate changes. The onset of regional drought since the late 1990s has resulted in extensive die-off episodes of multiple tree species across millions of acres in the Southwest, fostering substantial collaborative tree mortality research in this region. Ongoing tree mortality research in northern New Mexico includes: reconstruction of historic forest dieback patterns; monitoring of forest and woodland demographies (tree mortality and regeneration); experimental determination of physiological thresholds of drought- and heat-induced tree mortality; relationships between tree growth, drought stress, insects/diseases, and mortality; remote-sensing of landscape-scale patterns of forest stress and die-off; documentation of regional, national, and global patterns of forest die-off; and efforts to improve models of tree mortality processe
Multi-scale predictions of massive conifer mortality due to chronic temperature rise
Larger trees suffer most during drought in forests worldwide
On underestimation of global vulnerability to tree mortality and forest die-off from hotter drought in the Anthropocene
Patterns and causes of observed piñon pine mortality in the southwestern United States
Projected future changes in vegetation in western North America in the 21st century
Watering the forest for the trees: An emerging priority for managing water in forest landscapes
Quantifying tree mortality in a mixed species woodland using multitemporal high spatial resolution satellite imagery
Temperature as a potent driver of regional forest drought stress and tree mortality
Statement of Dr. Craig D. Allen, U.S. Geological Survey, Department of the Interior, before the Committee on Energy and Natural Resources, U.S. Senate, 17 August 2012
Millennial precipitation reconstruction for the Jemez Mountains, New Mexico, reveals changing drought signal
Climate-induced tree mortality: Earth system consequences
A global overview of drought and heat-induced tree mortality reveals emerging climate change risks for forests
- Overview
Natural climatic variability, including episodic droughts, has long been known to trigger accelerated tree mortality in forests worldwide, including in the Southwest U.S. Scientific understanding of the process drivers and spatial patterns of tree mortality is surprisingly limited, constraining our ability to model forest responses to projected climate changes. The onset of regional drought since the late 1990s has resulted in extensive die-off episodes of multiple tree species across millions of acres in the Southwest, fostering substantial collaborative tree mortality research in this region. Ongoing tree mortality research in northern New Mexico includes: reconstruction of historic forest dieback patterns; monitoring of forest and woodland demographies (tree mortality and regeneration); experimental determination of physiological thresholds of drought- and heat-induced tree mortality; relationships between tree growth, drought stress, insects/diseases, and mortality; remote-sensing of landscape-scale patterns of forest stress and die-off; documentation of regional, national, and global patterns of forest die-off; and efforts to improve models of tree mortality processe
Dead ponderosa pine in Great Basin National Park, Nevada. Photo by Craig Allen, USGS, 2015. Public domain. Dead piñon (Pinus edulis), Bandelier National Monument, Jemez Mountains, NM. Trees that died in 2002-2003. Photo by Craig Allen, USGS, 2007. Public domain. In the summer of 2002, piñon pine (Pinus edulis) began dying en masse from drought stress and an associated bark beetle outbreak. Jemez Mouintains near Los Alamos, NM, October 2002. Credit: Craig Allen, USGS. Public domain. The same landscape as above: after the needles dropped, grey skeletons of piñon pine (Pinus edulis) remain, with surviving Jumiperus monosperma still green. Jemez Mountains, NM. May 2004. Photo by: Craig Allen, USGS. Public domain. Dead ponderosa pine (Pinus ponderosa), Jemez Mts, NM. November, 2013. Photo by: Craig Allen, USGS. Public domain. Dead ponderosa pines in the Jemez mountains, New Mexico. Photo by: Craig Allen, USGS. Public domain. Dead white fir (Abies concolor) and Douglas-fir (Pseudotsuga menziesii in the Upper Frijoles mountains, New Mexico, 2003. Photo by: Craig Allen, USGS. Public domain. Sequoia Nationall Park, mortality of multiple conifer species, particularly ponderosa pine (P. ponderosa), sugar pine (Pinus lambertiana), and white fir (Abies concolor). October 2015. Photo by: Craig Allen, USGS. Public domain. Dead ponderosa pine (P. ponderosa), Yosemite National Park. Nov. 2016. Photo by: Craig Allen, USGS. Public domain. Dead ponderosa pine (P. ponderosa) and sugar pine (P. lambertiana), Yosemite National Park. Photo by: Craig Allen, USGS. Public domain. - Publications
Filter Total Items: 22
Multi-scale predictions of massive conifer mortality due to chronic temperature rise
Global temperature rise and extremes accompanying drought threaten forests and their associated climatic feedbacks. Our ability to accurately simulate drought-induced forest impacts remains highly uncertain in part owing to our failure to integrate physiological measurements, regional-scale models, and dynamic global vegetation models (DGVMs). Here we show consistent predictions of widespread mortAuthorsNathan G. McDowell, A.P. Williams, C. Xu, W. T. Pockman, L. T. Dickman, Sanna Sevanto, R. Pangle, J. Limousin, J.J. Plaut, D.S. Mackay, J. Ogee, Jean-Christophe Domec, Craig D. Allen, Rosie A. Fisher, X. Jiang, J.D. Muss, D.D. Breshears, Sara A. Rauscher, C. KovenLarger trees suffer most during drought in forests worldwide
The frequency of severe droughts is increasing in many regions around the world as a result of climate change. Droughts alter the structure and function of forests. Site- and region-specific studies suggest that large trees, which play keystone roles in forests and can be disproportionately important to ecosystem carbon storage and hydrology, exhibit greater sensitivity to drought than small treesAuthorsAmy C. Bennett, Nathan G. McDowell, Craig D. Allen, Kristina J. Anderson-TeixeiraOn underestimation of global vulnerability to tree mortality and forest die-off from hotter drought in the Anthropocene
Patterns, mechanisms, projections, and consequences of tree mortality and associated broad-scale forest die-off due to drought accompanied by warmer temperatures—“hotter drought”, an emerging characteristic of the Anthropocene—are the focus of rapidly expanding literature. Despite recent observational, experimental, and modeling studies suggesting increased vulnerability of trees to hotter droughtAuthorsCraig D. Allen, David D. Breshears, Nathan G. McDowellPatterns and causes of observed piñon pine mortality in the southwestern United States
Recently, widespread piñon pine die-off occurred in the southwestern United States. Here we synthesize observational studies of this event and compare findings to expected relationships with biotic and abiotic factors. Agreement exists on the occurrence of drought, presence of bark beetles and increased mortality of larger trees. However, studies disagree about the influences of stem density, elevAuthorsArjan J.H. Meddens, Jeff H. Hicke, Alison K. Macalady, P.C. Buotte, T.R. Cowles, Craig D. AllenProjected future changes in vegetation in western North America in the 21st century
Rapid and broad-scale forest mortality associated with recent droughts, rising temperature, and insect outbreaks has been observed over western North America (NA). Climate models project additional future warming and increasing drought and water stress for this region. To assess future potential changes in vegetation distributions in western NA, the Community Earth System Model (CESM) coupled withAuthorsJiang Xiaoyan, Sara A. Rauscher, Todd D. Ringler, David M. Lawrence, A. Park Williams, Craig D. Allen, Allison L. Steiner, D. Michael Cai, Nate G. McDowellWatering the forest for the trees: An emerging priority for managing water in forest landscapes
Widespread threats to forests resulting from drought stress are prompting a re-evaluation of priorities for water management on forest lands. In contrast to the widely held view that forest management should emphasize providing water for downstream uses, we argue that maintaining forest health in the context of a changing climate may require focusing on the forests themselves and on strategies toAuthorsGordon E. Grant, Christina L. Tague, Craig D. AllenQuantifying tree mortality in a mixed species woodland using multitemporal high spatial resolution satellite imagery
Widespread tree mortality events have recently been observed in several biomes. To effectively quantify the severity and extent of these events, tools that allow for rapid assessment at the landscape scale are required. Past studies using high spatial resolution satellite imagery have primarily focused on detecting green, red, and gray tree canopies during and shortly after tree damage or mortalitAuthorsSteven R. Garrity, Craig D. Allen, Steven P. Brumby, Chandana Gangodagamage, Nate G. McDowell, D. Michael CaiTemperature as a potent driver of regional forest drought stress and tree mortality
s the climate changes, drought may reduce tree productivity and survival across many forest ecosystems; however, the relative influence of specific climate parameters on forest decline is poorly understood. We derive a forest drought-stress index (FDSI) for the southwestern United States using a comprehensive tree-ring data set representing AD 1000-2007. The FDSI is approximately equally influenceAuthorsA. Park Williams, Craig D. Allen, Alison K. Macalady, Daniel Griffin, Connie A. Woodhouse, David M. Meko, Thomas W. Swetnam, Sara A. Rauscher, Richard Seager, Henri D. Grissino-Mayer, Jeffrey S. Dean, Edward R. Cook, Chandana Gangodagamage, Michael Cai, Nathan G. McDowellStatement of Dr. Craig D. Allen, U.S. Geological Survey, Department of the Interior, before the Committee on Energy and Natural Resources, U.S. Senate, 17 August 2012
No abstract available.AuthorsCraig D. AllenMillennial precipitation reconstruction for the Jemez Mountains, New Mexico, reveals changing drought signal
Drought is a recurring phenomenon in the American Southwest. Since the frequency and severity of hydrologic droughts and other hydroclimatic events are of critical importance to the ecology and rapidly growing human population of this region, knowledge of long-term natural hydroclimatic variability is valuable for resource managers and policy-makers. An October–June precipitation reconstruction foAuthorsRamzi Touchan, Connie A. Woodhouse, David M. Meko, Craig D. AllenClimate-induced tree mortality: Earth system consequences
One of the greatest uncertainties in global environmental change is predicting changes in feedbacks between the biosphere and the Earth system. Terrestrial ecosystems and, in particular, forests exert strong controls on the global carbon cycle and influence regional hydrology and climatology directly through water and surface energy budgets [Bonan, 2008; Chapin et al., 2008].According to new reseaAuthorsHenry D. Adams, Alison K. Macalady, David D. Breshears, Craig D. Allen, Nathan L. Stephenson, Scott Saleska, Travis E. Huxman, Nathan G. McDowellA global overview of drought and heat-induced tree mortality reveals emerging climate change risks for forests
Greenhouse gas emissions have significantly altered global climate, and will continue to do so in the future. Increases in the frequency, duration, and/or severity of drought and heat stress associated with climate change could fundamentally alter the composition, structure, and biogeography of forests in many regions. Of particular concern are potential increases in tree mortality associated withAuthorsCraig D. Allen, A.K. Macalady, H. Chenchouni, D. Bachelet, N. McDowell, Michel Vennetier, T. Kitzberger, A. Rigling, D.D. Breshears, E. H. (T.) Hogg, P. Gonzalez, R. Fensham, Z. Zhang, J. Castro, N. Demidova, J.-H. Lim, G. Allard, S. W. Running, A. Semerci, N. Cobb