New Mexico Dendroecology Lab

Ellis Margolis cross dates an old piece of ponderosa pine from the Tesuque watershed outside of Santa Fe, New Mexico. Collin Haffey, USGS Public domain.

We conduct interdisciplinary landscape-scale ecological research that focuses on the effects of climate variability on forest ecology, fire ecology, and ecohydrology. Much of the research is applied and therefore designed to inform forest, fire, and ecohydrology resource management (e.g., Santa Fe Fireshed Collaboration Restoration Initiative). We use dendrochronology as a primary research tool, which involves dendrochronological cross-dating of tree-ring samples, including fire scars and tree ring-width series.

Current research projects include:

1) Tree-ring reconstructions of fire history in the Taos Valley Watersheds, 2) Tree-ring reconstructions of fire history in the Santa Fe Fireshed, 3) The largest mountain-range fire scar network in North America: fire regime reconstruction in the Jemez Mountains, 4) Dual-season climate reconstructions and fire-climate relationships in the southwestern United States, 5) Fire history, old-growth forests, and climate change on the Navajo Nation, 6) 'burnr' A dendroecology package in R, 7) Fire regimes and persistence of oak shrubfields in the Jemez Mountains, 8) Cambial phenology of ponderosa pine: combining dendrobands and cellular analysis, 9) Age structure and spatial patterns of ponderosa pine in the Gila Wilderness, and 10) Culturally modified trees in northern New Mexico.

Research project descriptions:

1. Tree-ring reconstructions of fire history of the Taos Valley Watersheds

Working with a collaborative group of stakeholders, we are developing new fire history records from tree rings to inform forest and fire management decisions in three critical watershed in the Sangre de Cristo Mountains near Taos, New Mexico.  Limited data exists on fire and ecosystem response to fire and climate variability in these watersheds, although the ecosystem services they provide are critical to the local communities, including Taos Pueblo.  Tree rings provide centuries-long records to understand the interactions between ecosystems, fire, and climate.

An old limber pine log from the Rio Hondo drainage near Taos Ski Valley, with six fire scars – five of which pre-date 1500 CE. Photo by Lane Johnson, USGS. Public domain.

2. Tree-ring reconstructions of fire history in the Santa Fe Fireshed

Working with a collaborative group of stakeholders, we are developing new fire history records from tree rings to inform forest and fire management decisions in critical watersheds in the southern Sangre de Cristo Mountains near Santa Fe, New Mexico.  The watersheds provide many ecosystem services (e.g., water supply for the City of Santa Fe), and high-severity fires threaten the ecological and social values of the forests.  A long-standing science-management partnership in the region works to use science to guide local forest, fire and watershed management.

Tree-ring fire history reconstructions for mixed conifer forests in the Greater Santa Fe Fireshed, New Mexico.  Frequent low-severity fires, with limited, patchy high-severity fire, burned for centuries prior to human-caused fire exclusion in the mid- to late-1800s. Illustration by: Ellis Margolis, USGS. Public domain.

3. The largest mountain-range fire scar network in North America: fire regime reconstruction in the Jemez Mountains

Over 30 years of tree-ring fire history research in the Jemez Mountains, New Mexico has built the largest tree-ring fire scar network for a single mountain range in North America (1,343 trees and 9,014 fire scars - and counting). We are expanding the network using a spatially systematic sampling approach with a main goal of reconstructing area burned since 1600 CE over a 300,000 acre area. These reconstructions will allow us to place recent “large” fires (e.g., 150,000 acre Las Conchas fire) in a historical context and ultimately can inform long-term carbon fluxes related to fire and climate.

The tree-ring fire scar network in the Jemez Mountains covering >300,000 acres.  Colored symbols represent individual fire-scarred trees from different collections over 30 years. Public domain.

The large spatial foot print of fire in the Jemez Mountains in the year 1729, as recorded by tree-ring fire scars. The circles are individual trees that were scarred in 1729, with the colors indicating the fire-scar position, or fire seasonality. The predominance of early season scars indicates a spring/early-summer fire.  The grey x's indicate trees that were not scarred. The histogram in the upper right indicates the relative elevation of the fire-scarred trees. Photo by Ellis Margolis, USGS. (Public domain.)

4. Dual-season climate reconstructions and fire-climate relationships in the southwestern United States

Working in collaboration with Connie Woodhouse and Tom Swetnam from the University of Arizona on an NSF Macrosystems project, we are quantifying the effects of winter and summer (monsoon) moisture on fire occurrence and fire seasonality in two regions of the Southwest - the Jemez Mountains of northern New Mexico and the Sky Islands of southern Arizona.  Variability in winter moisture is a primary driver of large spring and early-summer fire occurrence, but weak or failed monsoons in the past (e.g., 1752) enabled large fires to burn in the mid to late summer.  Large mid-summer fires are unprecedented in the last century in the Southwest.  In addition, we found that extended droughts historically did not promote continued fire occurrence, due to fuel limitations.  This suggests that although fuels are not currently limiting for fire occurrence in dry conifer forests (due to a century of fire suppression), these forests will likely return to being fuel limited in future decades.

Prior wet conditions followed by drought in the cool- and monsoon-seasons affect fire occurrence and fire seasonality (e.g., D = Spring dormant fires, A = Fall latewood fires) in the Jemez Mountains (1599 – 1899). Ellis Margolis, USGS. Public domain.

Abundant old trees on the Navajo Nation provide centuries-long records to study ecosystem responses to disturbances and climate variability. Photo by Ellis Margolis, USGS. (Public domain.)

5. Fire history, old-growth forests, and climate change on the Navajo Nation

Working in collaboration with Chris Guiterman (University of Arizona), Navajo Forestry, and the BIA, we are using tree rings to identify and assess the vulnerabilities of Navajo forests to climate change. Across several projects in ponderosa pine and dry mixed conifer forests, we are (1) reconstructing historic fire regimes, looking for human and climate drivers of fire activity and assessing current conditions, (2) measuring forest growth and climate sensitivity from a large set of increment core collections, and (3) evaluating patterns of tree recruitment, growth, and mortality in old-growth stands.

History of tree-rings in New Mexico

Florence Hawley Ellis was one of the first students of A.E. Douglass, the founder of dendrochronology, at the University of Arizona in the early 1900s. After finishing her Ph.D., she became a professor of Anthropology at the University of New Mexico, Albuquerque, where she had a long and distinguished career (1934 – 1971). She contributed important work on the history of Chetro Ketl at Chaco Canyon, using newly developed dendroarchaeological techniques to determine the exact year structures were built over 1000 years ago. In addition, she was one of the pioneers of dendrochronology in the eastern U.S., where she tested whether new tree species were suitable for tree-ring dating and dendroarchaeological analyses of cultural sites of eastern Native American cultures. 

This project is in cooperation with Lane Johnson of the National Park Service 

Read more about the Florence Hawley Ellis Papers

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