Associate Professor

Kevin Anchukaitis

Contact
Email:
kanchukaitis@email.arizona.edu
Phone:
520 626-8054
Room:
ENR2 S514
Other Room:
Bannister 419
Webpage:

Dendroclimatology, drought, volcanic eruptions, climate field reconstructions, stable isotope dendroclimatology, tropical dendrochronology, proxy systems modeling. 

Don Falk

Contact
Email:
dafalk@u.arizona.edu
Phone:
+1 (520) 626-7201
Room:
BioSci East 207
Webpage:

School of Natural Resources

Dr. Falk’s work focuses on three general areas: fire regimes, disturbance interactions and fire-climate relationships, and restoration ecology. Most fieldwork is conducted in western North America, including ongoing programs in New Mexico and Arizona. New initiatives include fire history and fire-climate analysis in the North American Great Basin and the Sierra Madre of Mexico.

One set of questions addressed in Falk’s lab revolves around the mathematical foundations of fire regime reconstruction and the development of analytical tools for fire history. A central case concerns the existence of scaling relationships in fire regimes, a problem not previously studied systematically. We also work on probability models for surface fire regimes and mathematical theory for sample size analysis in fire history.

A second emerging area of interest is fire-climate relationships. Collaborating with Dr. Swetnam, we use multivariate methods to understand persistent cross-scale patterns of synchrony in fire regimes of the western US. Collaborators include Rocky Mountain Tree-Ring Research, the US Forest Service Fire Sciences Laboratory, and Northern Arizona University. A new project funded by the Joint Fire Science Program links fire history, fire behavior, and land management practices in forest-grassland ecotones of the Valles Caldera National Preserve (VCNP), New Mexico. This project will attempt to reconstruct the ecotonal fire regime using remnant tree-ring evidence, and to infer spatial patterns of fire spread and climate regulation. The USGS Jemez Mountains Field Station is a central collaborator. In 2006 we initiated a program of fire history and climate work in the North American Great Basin, the largest area of the western United States lacking a basic network of fire history sites; the region is also located pivotally with respect to the “dipole” of the El Niño Southern Oscillation (ENSO) teleconnection in North America. We are beginning fieldwork in 2007, with collaborators in the Bureau of Land Management and US Forest Service.

The Falk lab collaborates with Dr. Ann Lynch, US Forest Service, Rocky Mountain Research Station (RMRS), to study disturbance interactions in the Pinaleño Mountains, Arizona, one of the highest “sky island” ranges, supporting high-elevation spruce-fir forests as well as extensive areas of mixed-conifer and other forest types. Our work combines reconstruction of historical fires, insect outbreaks, tree demography, and the role of climate variability in regulating short- and long-term forest dynamics.

In restoration ecology, a key project was a book addressing the theoretical basis for the science of restoration ecology. Falk collaborated with Joy Zedler (University of Wisconsin), Margaret Palmer (University of Maryland), and more than 20 colleagues to assemble the first book on this subject. Foundations of Restoration Ecology was published by Island Press in 2006.

In the field, the Falk group has been working on forest and fire regime restoration at Monument Canyon, New Mexico since 2003. We have established a plot-based program of annual monitoring of tree condition, understory diversity, and other variables. 230 ha were thinned in 2005-6 following a “process-centered restoration” model designed collaboratively with the Santa Fe National Forest (SFNF). We are also continuing a longitudinal study of old-tree responses to drought and competition in collaboration with the USGS Jemez Mountains Field Station, and a study of ecophysiological response of old trees to competition and release in collaboration with Los Alamos National Laboratory. A new restoration project linking forest thinning, fire behavior models, ecophysiology, and restoration of the fire regime is beginning in the Sangre de Cristo Mountains, New Mexico. This project, also with the SFNF, will use strategically-placed thinning treatments (“SPLATS”) followed by reintroduction of fire. Our lab’s role includes monitoring of treatment effects on old trees, as well as expanded fire history and post-treatment responses.

Katie Hirschboeck

Contact
Email:
katie@ltrr.arizona.edu
Phone:
+1 (520) 621-6466
Room:
Bannister 319
Webpage:

A unifying theme in Dr. Katie Hirschboeck’s research is the linkage between atmospheric circulation, along with its associated weather and climate mechanisms, and variability in extreme events. Her investigations have progressed from the theoretical examination of the patterns that produce extreme flood events in statistical time series, to analyses of the synoptic circulation patterns that produce frost rings and drought signals in tree-ring records, to new stakeholder-driven research on synchronous high and low extreme streamflow episodes detected from tree-ring reconstructions (in collaboration with Dave Meko) Hirschboeck’s tree-ring related research is based on synoptic dendroclimatology, an approach that links tree ring variations to weather events and atmospheric circulation patterns. Research questions that she has been addressing over the past decade include:

  1. What role does large-scale atmospheric circulation and its attendant weather events play in local and regional tree-growth responses as revealed in tree-ring records? and
  2. How can a mechanistic link between circulation and tree rings be used to improve the understanding of past climatic variability from a process-based perspective? She uses a variety of techniques, such as manual and automated synoptic circulation typing, the integration of atmospheric sounding data into traditional dendroclimatic analyses, and various statistical approaches, to advance a more process-based understanding and interpretation of tree-ring reconstructions of both climatic and hydrologic variables.
    Hirschboeck’s flood-climate research centers on flood hydroclimatology, the analysis of observed floods and paleofloods in the context of their history of variation over time and the meteorological processes that produce them. Research questions being addressed include:
  3. How can an understanding of the atmospheric and hydrologic mechanisms that produce floods and droughts in the observed and paleo- records be used to assess the nonstationarity of hydrologic time series and the reliability of flood estimates and drought probabilities?
  4. How are anomalous atmospheric circulation patterns and persistence linked to clustering of major flood or low flow events in time and space? and
  5. Can knowledge of circulation patterns and hydrologic processes examined over long climatological time scales improve meteorological flood forecasting?

Paul Sheppard

Contact
Email:
sheppard@ltrr.arizona.edu
Phone:
+1 (520) 621-6474
Room:
Bannister 407
Webpage:

Dr. Sheppard uses tree rings to reconstruct environmental conditions of the past and/or to monitor modern-day environmental change:

Volcanic Effects:

The dating of Sunset Crater of northern Arizona, long thought to have erupted in A.D. 1064, is being re-examined. This research began by focusing on a more recent cinder cone, Parícutin of central Mexico, where results suggest dendrochemical increases in sulfur and phosphorus during the eruption. With modern calibration now established, dendrochronological attention is turning to Sunset Crater itself. A substantially different date of eruption of Sunset Crater would be a truly important contribution to Southwest archaeology. Initial results are promising, and we are hopeful that additional funding will be generated through archaeology, volcanology, and geosciences granting programs.

Childhood Leukemia:

The existence of multiple, concurrent clusters of childhood leukemia (e.g., Fallon, Nevada; Sierra Vista, Arizona; and Calvine-Florin, California) is a unique research opportunity: Is there any environmental issue held in common by these places that might be linkable to leukemia? Trees associated with the clusters have been sampled and measured in order to monitor temporal changes in urban settings. Dendrochemistry of trees in Fallon indicates that tungsten increased there in the mid 1990s, about the time of onset of the cluster of childhood leukemia in Fallon. This research has included other data types, including soil, inhalable dust, and even lichens. Results from all data types confirm that airborne tungsten is high in Fallon relative to that of other Nevada towns or the outlying desert in general.

General Pollution Studies:

Understanding the ramifications of the anthropogenic doubling of fixed nitrogen in the atmosphere is considered one of the great research challenges of ecology. Fieldwork has been initiated in the mountains of southern California to investigate the effects of changing nitrogen availability on tree growth. These mountains are in the air pollution plume of greater Los Angeles, and as such they receive enhanced quantities of fixed nitrogen. Long-term ring-width patterns might demonstrate tree responses to this extra nitrogen. Soil nitrogen should also be a key variable in this research. Tree and soil samples have been collected across microsites in an effort to associate tree vigor with soil nutrient availability. This sampling scheme is relatively unusual for dendrochronology, but it incorporates basic fundamentals of tree and site selection as well as of soil formation factors.

Image Analysis Innovations:

The practical and expedient use of image analysis in dendroclimatology of conifer species has been a long-standing goal. Recent efforts have been made to solve sample preparation issues of heartwood discoloration. Once quantitative image analysis of conifers is fully operational, it will be applied to strategic sites in the American Southwest, where summer rainfall is important for many stakeholders.

Ron Towner

Contact
Email:
rtowner@ltrr.arizona.edu
Phone:
+1 (520) 621-6465
Room:
Bannister 306
Webpage:

Dr. Towner is the Agnese and Emil W. Haury Endowed Chair in Archaeological Dendrochronology.

Dr. Towner’s research over the past decade has revolved around three major issues: human/environment interactions, dendroarchaeological method and theory, and expansion of archaeological dendrochronology nationally and internationally. These areas have been addressed using grant-funded projects, collaborative efforts with federal, state, tribal, and private entities, and by involving students directly in the research.

Dendroarchaeology is uniquely situated to examine human/environment interaction at fine temporal and spatial scales. By precisely dating archaeological sites and retrodicting climate parameters, Towner has examined cultural responses to both low- and high-frequency climatic variation and avoided the typical environmental determinist explanations that have been discredited in the past. One of his specific research areas has been on the Early Navajo and their adaptation to the fluctuating climate and very unstable social environment of the protohistoric period on the Colorado Plateau.

Dendroarchaeological method and theory is critical to understanding past human/environment interaction. An important aspect of Towner’s research has been to examine and promote understanding of the arboreal archaeological record across cultures using a landscape-scale approach. Although necessarily
temporally limited by tree age, such an approach provides abundant data relevant to the illumination of cross-cultural technological, social, and ecological transformations. Another role of dendroarchaeological method and theory is the calibration of other chronometric techniques. Towner is currently involved in research that will have significant impacts on radiocarbon dating in the Intermountain West and elsewhere.

Finally, one of Dr. Towner’s major goals has been to expand dendroarchaeology beyond the U.S. Southwest. Preliminary efforts, some successful and some that require additional effort, have been made in northern Sonora and Chihuahua, Mexico, coastal Peru, the Texas Hill country, the central Rockies, and northeastern Utah. Although some of these efforts have not yet yielded chronometric data, all have significantly contributed toward a fuller understanding of past wood use practices and cultural adaptations to different environments.

Valerie Trouet

Contact
Email:
trouet@ltrr.arizona.edu
Phone:
+1 (520) 626-8004
Room:
Bannister 320
Webpage:
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