Reduced forest vulnerability due to management on the Hualapai Nation

Tribal nations in the US have worked to uphold their long history of managing forests in ways that reduce fuels, support ecosystem functioning, and enhance Indigenous livelihoods. Forests on the Hualapai Nation at the western end of the Grand Canyon have been actively managed for decades using fire and other treatments. We collected data on tree size and age structure, forest understory characteristics, and surface fuels to explore how the legacy of forest management, historical surface fire, and recent prescribed fire, have influenced the contemporary structure of the ponderosa pine-Gambel oak forest on the Hualapai tribal lands (hereafter Hualapai forest). Current overstory tree density (range: 361.1 to 1664.0 trees ha⁻¹) and basal area (16.0 to 29.8 m² ha⁻¹) place the Hualapai forest in an intermediate state among more open vs. denser southwestern forests, but additional characteristics set the Hualapai forest apart from others in the region. In particular, diameter distributions of live ponderosa pine in the Hualapai forest are dominated by mid-diameter trees (trees ∼18-33 cm dbh), while diameter distributions of live ponderosa pine on forest lands across Arizona indicate a higher number of small-diameter trees (trees <23 cm dbh) and a lower number of large-diameter trees. This finding of a relatively lower number of small-diameter trees, which serve as ladder fuels, in the Hualapai forest may indicate better protection against severe wildfire, although some individual sites might be at greater risk due to higher numbers of small live trees and snags, seedlings and saplings, along with higher levels of coarse woody debris. Beyond fire risk, the Hualapai forest is lacking in large live trees and snags that support cultural needs and sustain its ecological functioning. Current management approaches are helping support the recovery of large trees and snags. While the Hualapai forest is at risk due to its location at the lower elevational limit of ponderosa pine in the Southwest, the legacy of past management and prescribed fire has differentiated it from similar forests in the region. Continued management informed by Indigenous perspectives can best position the Hualapai forest to sustain its structure and function as climate warms as well as achieve socio-cultural and ecological outcomes most important to the people of the Hualapai Tribe.