My name is Drew Peltier, and I am a Postdoctoral Researcher at Northern Arizona University.
I study tree growth and physiological responses to drought and climate change.
My research: Trees are uniquely long lived, and so their responses to the environment integrate climate across multiple time scales. Thus, the study of tree physiology requires an integration of approaches across scales, both spatial and temporal. My work addresses fundamental questions about the impacts of climate change and drought on tree physiology. And I am part of a growing field linking dendroecology to physiology, changing the way in which we think about tree growth responses to drought. My research 1) quantifies global change impacts upon the memory of tree growth, such as growth legacies of past drought, and 2) investigates the physiological mechanisms of those impacts.
1Drought legacies and climatic memory in tree growth. While we often assume growth-climate relationships to be time-invariant, my work has uniquely contributed to quantifying drought legacies—slow recoveries of growth sensitivities following drought—sometimes longer than 5 years. Recent papers have quantified the impact of La Niña events (ENSO cold-phase), compounded drought (multiple drought years in a row), and the broader implications of temporal variability in tree growth-climate sensitivity (described below).
Tree growth sensitivity to climate is temporally variable. And we can think about that in multiple ways.
Despite long discussion of these dynamics in the dendrochronology literature, we often assume tree growth responses to climate drivers are “stationary” through time (a).
In fact, we know from the drought legacy literature that tree growth sensitivities to climate are temporarily perturbed by disturbances like an extreme drought year (b).
However, tree growth sensitivities are likely emergent from the suite of physiological traits of individuals and populations (c). I am interested in the physiological mechanisms for this temporal variability.
Past work looked at the periodic perturbations to tree growth sensitivity imposed by La Niña (ENSO cold-phase) droughts.
In three species (Pinus edulis, Pinus ponderosa, Pseudotsuga menziesii), trees experience regular legacies from La Niña. These legacies are largest in the heart of the North American Monsoon region (blue shading, left).
Trees in the NAM region are highly dependent on summer monsoon precipitation to “rescue” them from these winter droughts. More here.
We know climate change is increasing drought frequency. How does this shortening return interval impact tree recovery?
In a recent study, I synthesized responses of ponderosa pine at 219 sites over the last century, representing more than 500k ring widths and 8,000 drought or drought recovery years.
“Triple-droughts” and “double-droughts” are worse than a single drought year. That is, trees experience greater growth reductions and legacies. But, different populations responded very differently!
And, way down in the weeds, how we account for memory really influences what we attribute to the disruptive impacts of drought vs. what may just be lagged responses of trees to past climate conditions. More here!
2NSC cycling under drought. So what types of dynamics alter tree growth responses to climate under drought? Non-structural carbohydrates and their cycling are a major mechanism I am exploring. In my present role I am leveraging a set of rainfall exclusion plots out at the Sevilleta LTER in Piñon pine. Piñon (P. edulis) is a foundation tree species in the southwestern US experiencing ongoing mortality from climate change drought. I am seeking to understand how lethal drought in this species may influence the remobilization and use of very old nonstructural carbohydrates (NSC). This work is using 0%, 45%, and 90% drought treatments in mature piñon at the Sevilleta LTER.
“White rings,” – typically an indicator of severe carbon limitation in forested ecosystems experiencing periodic defoliation by insects – shown here in a tree experiencing 10 years of 45% rainfall exclusion (left of image).
D14C of NSC shows these trees have exhausted their oldest NSC reserves sometime in the past 10 years.
Combined evidence from leaf level gas exchange, bole respiration rates, canopy and bole NSC concentrations, NSC D14C (age), leaf phenology, chlorophyll fluorescence, and tree rings, suggests tree NSC pools change slowly in response to drought. But long term drought induces severe carbon limitation, despite acclimation of leaf level photosynthetic rates (Amax) and reduction of bole respiration rates. We note that carbon limitation effects on defensive chemistry and heartwood investment remain poorly known. Defensive chemistry is a key focus of other researchers involved with this study, namely Amy Trowbridge and her lab group.
Future work within this study is exploring the terminal dynamics of NSC age and concentrations as trees die from bark beetle attack.
(Right) Tree killed in a Piñon ips beetle outbreak in 2020 at the Sevilleta LTER.
Past work has explored the role of NSC in drought legacies from the 2012 drought in a network of 22 forested sites (piñon, juniper, and aspen) across the Southwest.
We sampled three tree species to understand how non-structural carbohydrate (NSC) concentrations respond to moisture stress.
Responses differed broadly across species and seasons in ways that sometimes reflected hydraulic strategy (e.g. isohydry). Dynamics in all three species suggested sink limitation was common, but respiratory depletion, and osmoregulation were important too.
Those NSC concentrations also had real consequences for tree recovery from the 2012 drought.
The climate memory length for both aspen (green) and piñon (black) was strongly related to sugar concentrations (top).
Moreover, NSC concentrations were also strongly related to the magnitude of drought legacies (bottom).
Future work: What is the age of NSC used to recover from severe disturbance? In old growth coast redwoods burned in the CZU Lightning Complex (2020) at Big Basin Redwoods State Park, I am part of a project that aims to answer this very question. By quantifying the age of carbon (with D14C) in epicormic sprouts, we are quantifying the age of the carbon these giants are drawing upon to rebuild their canopies.
Future work: Drought mortality events are expanding in the western US and impacting previously considered stress-tolerant Cupressaceae. I am combining eco-physiological monitoring at sites around the Flagstaff area, as well as tree-ring work to understand how long-term climate change drought stress is leading to enhanced mortality in Colorado Plateau dominant Juniperus spp. and the neotropical arizona cypress (Hesperocyparis arizonica).
- Yocom, L, K Ogle, DMP Peltier, P Szejner, Y Liu, RK Monson. Tree growth response to climate varies across a monsoon precipitation gradient. Oecologia: Accepted 2/22/22.
- MarquésL., K. Ogle, DMP Peltier, J.J. Camarero. 2022. Altered climate memory characterizes tree growth during forest dieback.. Agricultural and Forest Meteorology: 314, 108787.
- Peltier, DMP, P. Nguyen*, M. Bangs*, M. Wilson*, L. Gear*, J. Guo, K. Samuels-Crow, L. Yocom, Y. Liu, M.K. Fell, D. Auty, W.R.L. Anderegg, G.W. Koch, M. Litvak, J. Shaw, K. Ogle. Temperature memory and non-structural carbohydrates mediate legacies of a hot drought in trees across the southwestern US. Tree Physiology: 42 (1), 71-85. Link.
- MarquésL., DMP Peltier, J.J. Camarero, M.A. Zavala, J. Madrigal-González, G. Sangüesa-Barreda, and K. Ogle. Recovering ecological memory from tree ring data to disentangle the influences of climate and management in mixed silver-fir forests from the Pyrenees. Ecosystems 25: 215–235. Link.
- Peltier, DMP, P. Nguyen*, M. Bangs*, M. Wilson*, L. Gear*, J. Guo, K. Samuels-Crow, L. Yocom, Y. Liu, M.K. Fell, D. Auty, W.R.L. Anderegg, G.W. Koch, M. Litvak, J. Shaw, K. Ogle. 2020. Temporal controls on crown non-structural carbohydrates in southwestern US tree species. Tree Physiology 41: 388-402. Link.
- Peltier, DMP, and K. Ogle. 2020. Tree growth sensitivity to climate is temporally variable. Ecology Letters 23: 1561–1572. Link.
- Peltier, DMP, and K. Ogle. 2019. Legacies of more frequent drought in ponderosa pine across the western United States. Global Change Biology 25: 3803-3816. Link.
- Ogle, K., DMP Peltier, M. Fell, J. Guo, H. Kropp, and J.J. Barber. 2019. Should we be concerned about multiple comparisons in hierarchical Bayesian models? Methods in Ecology and Evolution 10: 553-564. Link.
- Peltier, DMP, and K. Ogle. 2019. Legacies of La Niña: North American monsoon can rescue trees from winter drought. Global Change Biology 25: 121-133. Link.
- Peltier, DMP, J.J. Barber, and K. Ogle. 2018. Quantifying antecedent climatic drivers of tree growth in the Southwestern US. Journal of Ecology 106: 613-624. Link.
- Ryan, E. M., K. Ogle, DMP Peltier, A. P. Walker, M. G. De Kauwe, B. E. Medlyn, D. G. Williams, W. Parton, S. Asao, B. Guenet, and others. 2017. Gross primary production responses to warming, elevated CO2, and irrigation: quantifying the drivers of ecosystem physiology in a semiarid grassland. Global Change Biology 23: 3092–3106. Link.
- Peltier, DMP, M. Fell, and K. Ogle 2016. Legacy effects of drought in the southwestern United States: A multi-species synthesis. Ecological Monographs 86: 312-326. Link.
- Peltier, DMP, I. Ibáñez. 2015. Patterns and variability in seedling carbon assimilation: implications for tree recruitment under climate change. Tree Physiology 35: 71–85. Link.
- Ibáñez, I., D.S. Katz, DMP Peltier, S.M. Wolf, and B.T. Connor-Barrie. 2014. Assessing the integrated effects of landscape fragmentation on plants and plant communities: the challenge of multiprocess–multiresponse dynamics. Journal of Ecology 102: 882–895. Link.
- Czaun, M., A. Goeppert, R. B. May, D. Peltier, H. Zhang, G.K. Surya Prakash, and G. A. Olah. 2013. Organoamines grafted on nano-sized silica for carbon dioxide capture. Journal of CO2 Utilization 1: 1-7.
I have given a tree ring class for a couple of years with the Highlands Center for Natural History in Prescott, AZ.
I also have been working with the Grand Canyon Trust to provide hands on field classes in tree rings. We core trees and talk about climate change on the Colorado Plateau.
I am also an avid rock climber, and serve as a board member of the Northern Arizona Climber’s Coalition focused on anchor replacement initiatives in Northern Arizona. NAZCC.org.