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Forest Monitoring and Tree Ring Data to Inform Forest Management on the Navajo Nation

Enhanced Forest Monitoring with Tree Rings to Support Navajo Management of Forest Resources
Principal Investigator
Margaret K. Evans

Dates

Release Date
2019
Start Date
2020-03-15
End Date
2022-03-14

Summary

Healthy forests in the western United States provide multiple benefits to society, including harvestable timber, soil stabilization, and habitat for wildlife. On the Navajo Nation, over 5 million acres of forest provide wood that heats 50% of homes, building materials, summer forage for livestock, and drinking water. However, warming temperatures and changes in precipitation patterns can increase forests’ vulnerability to insect outbreaks and catastrophic wildfire. Forest managers, particularly those associated with tribal communities that depend on forests to maintain a subsistence lifestyle, need knowledge-based tools in order to reduce the impacts of climate change on forests. This project aims to study approximately 700,000 [...]

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Purpose

Forests provide multiple ecosystem services. Across the interior western U. S., warming temperatures cause drought stress to forests, greater vulnerability to insect outbreaks, and increased risk of fire. Forest managers have the difficult task of mitigating these stresses and maintaining the ecosystem services that forests provide. Forests of the Navajo Nation include ~600,000 acres of ponderosa pine and mixed-conifer forest. This working landscape supports Diné (Navajo) people, for example, by providing wood that is the primary source of heat for ~50% of homes, as well as poles for homes and other structures, summer forage for livestock, and drinking water. Navajo foresters are increasingly concerned about loss of forest driven by warming temperatures. The Navajo Forestry Department has a long history (dating to 1974) of monitoring their forests via a system of forest inventory plots. These monitoring plots have not been visited since 2004; they will be measured in 2019 and are not likely to be visited again for another 15 years. In this rare window of opportunity, we will augment the existing forest monitoring program by collecting tree-ring data in a subset of the forest inventory plots in 2019. Tree rings offer information on year-to-year variation in tree growth, including the response of trees of different sizes and species to drought conditions and forest stand density. Analysis of these tree-ring data will answer the question of how and why drought stress varies across the forests of the Navajo Nation, which can be then used to inform forest management aimed at increasing forest resistance and resilience to drought, for example, by thinning forest stands. The approach developed here, using representatively-sampled tree-ring data to evaluate climate stress and inform forest management, can be repeated across the Interior Western U. S. and elsewhere.

Project Extension

parts
typeTechnical Summary
valueForests of the Navajo Nation are experiencing warming temperatures that exacerbate drought stress, along with increased risk of bark beetle outbreaks and high-severity fire, the last resulting from high fuel loads associated with fire exclusion. Navajo foresters are increasingly concerned about loss of forest to these stressors, along with the loss of ecosystem services. Density reduction treatments and the use of surface fire in management are proven silvicultural strategies to reduce these vulnerabilities and increase forest resilience, but translating strategic directives into tactical (actionable) plans requires a local, forest-scale analysis to inform placement and specifics of treatments. In collaboration with Navajo foresters Alexious Becenti (Navajo Forestry Department, NFD) and Jamie Yazzie, we propose to catalyze this process by collecting local data, analyzing them, and deliberating on those results to support NFD prioritization and placement of treatments. Now is the time to do this work. The Navajo forest inventory plot network has not been measured in 15 years; it will be measured in the 2019 field season, and not again for another 15 years. Specifically, we will augment this planned forest monitoring by collecting ~1,000 increment cores in the Navajo forest inventory plot network, across a representative sample of forest types, stand densities, and canopy classes, adding annual-resolution information about how year-to-year climate (e.g., drought) variation affects tree growth. The proposed funding would support this tree ring sampling, conducted by a crew of two Navajo foresters led by Jaime Yazzie. The samples would then be crossdated and measured in the Dendro Lab at Utah State University under the supervision of coPI DeRose. Variation in tree-level basal area increments will be analyzed using multiple regression models, to evaluate the many and interacting factors (e.g., tree size and canopy position, species, stand density, biophysical variables) that influence tree growth and its drought sensitivity. This will generate a refined picture of how and why drought stress varies on the landscape – for example, how drought stress affects trees in different canopy classes, or is influenced by stand density – which can then be used to inform specific silvicultural practices aimed at climate adaptation. We plan for an in-person meeting at the Navajo Forestry Department Office in Ft. Defiance in the first quarter of project year two (September, 2020) to discuss results as they emerge and deliberate on silvicultural tactics. Deliverables will include the representative tree-ring collection, a final report delivered to the NFD summarizing the treatment options expected do the most good at the fastest pace, a short fact sheet with strong visuals that can be used by the NFD in chapter house meetings to discuss forest health and management, and the dissemination of results at the 2021 Intertribal Timber Symposium and Navajo Department of Natural Resources Summit by Jaime Yazzie. Finally, the tree-ring data and multiple regression analyses produced here can, in the future, serve as the basis for the development of a tree ring-based, climate-sensitive version of the Forest Vegetation Simulator, the growth and yield model used by foresters across the U. S. to project forest dynamics into the future and make decisions about forest treatments.
projectStatusIn Progress

Arizona (public domain)
Arizona (public domain)

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  • National and Regional Climate Adaptation Science Centers
  • Southwest CASC

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Type Scheme Key
RegistrationUUID NCCWSC ed401cb6-9b01-4f6e-91c2-edbde65a81ba
StampID NCCWSC SW19-MK1776

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