The contribution of Indigenous stewardship to an historical mixed-severity fire regime in British Columbia, Canada

Indigenous land stewardship and mixed-severity fire regimes both promote landscape heterogeneity, and the relationship between them is an emerging area of research. In our study, we reconstructed the historical fire regime of Ne Sextsine, a 5900-ha dry, Douglas-fir-dominated forest in the traditional territory of the T’exelc (Williams Lake First Nation) in British Columbia, Canada. Between 1550 and 1982 CE, we found median fire intervals of 18 years at the plot-level and 4 years at the study site-level. Ne Sextsine was characterized by an historical mixed-severity fire regime, dominated by frequent, low-severity fires indicated by fire scars, with infrequent, mixed-severity fires indicated by cohorts. Differentiating low- from mixed-severity plots through time was key to understanding the drivers of the fire regime at Ne Sextsine. Low-severity plots were coincident with areas of highest use by the T’exelc, including winter village sites, summer fishing camps, and travel corridors. The high fire frequency in low-severity plots ceased in the 1870s, following the smallpox epidemic, the forced relocation of Indigenous peoples into small reserves, and the prohibition of Indigenous burning. In contrast, the mixed-severity plots were coincident with areas where forest resources, such as deer or certain berry species, were important. The high fire frequency in the mixed-severity plots continued until the 1920s when industrial-scale grazing and logging began, facilitated by the establishment of a nearby railway. T’exelc oral histories and archaeological evidence at Ne Sextsine speak to varied land stewardship, reflected in the spatiotemporal complexity of low- and mixed-severity fire plots. Across Ne Sextsine, 63% of cohorts established and persisted in the absence of fire after colonial impacts beginning in the 1860s, resulting in a dense, homogenous landscape that no longer supports T’exelc values and is more likely to burn at uncharacteristic high severities. This nuanced understanding of the Indigenous contribution to a mixed-severity fire regime is critical for advancing proactive fire mitigation that is eco-culturally relevant and guided by Indigenous expertise.