Abstract: It is increasingly recognized that many ecosystems were part of coupled human-natural systems for centuries to millennia. Fire was a keystone ecosystem process in the western United States prior to fire regime disruption circa 1900 CE that was driven by widespread social and land use changes associated with westward expansion (e.g., domestic livestock grazing, logging, decreased Indigenous burning, and active fire suppression). The upper Rio Grande Basin of New Mexico was under Spanish rule beginning in circa 1600 CE until a social upheaval led by local Indigenous groups in 1680 CE – the Pueblo Revolt – transformed life and land use in the region. A second major social transformation was the establishment of Land Grants following Spanish re-occupation and the Mexican conquest. Land grants were established over multiple centuries in specific mapped areas that exist today. We used tree-ring fire-scars to reconstruct fire history in two landscapes in northern New Mexico and tested for fire regime changes in the 17th – 19th century associated with the Pueblo Revolt and Land Grant establishment. We hypothesize that the social transformations and associated land use changes would decrease fire occurrence by 1) increasing domestic livestock grazing that removed sufficient amounts of grass (fuel) to prevent fire spread, or 2) decreasing Indigenous burning. The Rio Grande del Norte study area is immediately adjacent to the location where the Pueblo Revolt was initiated at Taos Pueblo in 1680 and the Tierra Amarilla study area is one of the largest Land Grants in New Mexico, established in 1832, and is still a stronghold for traditional sheep grazing. Fire was historically frequent in both study areas but declined significantly after the social changes; fires stopped in Tierra Amarilla after the Land Grant was established and fires stopped or significantly decreased in the Rio Grande del Norte after the Pueblo Revolt. Our results support the long-standing linkages between social and natural systems that provide lessons for managing ecosystems today in light of past and current human influences.
