The ecological legacy of Indian burning practices in southwestern Oregon
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AbstractGraduation date: 2006
Two research questions are posed: (1) How have ecosystem conditions changed through time in southwestern Oregon? (2) How have culture-driven and climate-driven processes contributed to ecosystem change in southwestern Oregon? A brief introduction to the Little River study area is followed by a cultural and ecological history of the watershed. Historical, ecological and archaeological data are used to describe shifts in landscape structure, stand structure and fire behavior. Changes in corridor/patch/matrix relationships, increases in stand densities, and changes in stand age and species structure are documented, and changes in fire dynamics from frequent to infrequent, and small to large are corroborated with descriptive statistics from the nearby 2002 Umpqua Fires. Hypotheses are then proposed to test the relative influence of humans vs. climate on landscape change during Aboriginal (<1820) vs. Euroagrarian (1850-1950) cultural phases. While precipitation shows no correlation with fire frequency or tree recruitment before 1820, significant associations are observed from 1850 to 1950. Moreover, a significant correlation exists between fire frequency and subsequent tree recruitment after 1850, but is not observed during aboriginal times. This suggests that indigenous management fires may have obscured precipitation influences that become apparent only after 1850. In order to test spatial hypotheses concerning the associations between indigenous humans and the landscape, archaeological sites were digitized into a GIS, and ergonomic pathways were modeled between them. These maps are then compared to historically fire-maintained upland meadows interpreted from 1946 aerial photos. A significant spatial correlation was found between archaeological sites and historic meadows, and a highly significant spatial correlation was found between modeled travel networks and historic meadows. The close spatial association between cultural features and fire-maintained habitats again suggests active landscape management by local Indians. These associations are corroborated with historical records. After summarizing the shifts in ecological conditions and describing current conditions, I argue that while restoring the landscape to aboriginal conditions is no longer possible, emulating those conditions within the framework of the Little River Adaptive Management Area Plan can improve the resilience and productivity of the Little River watershed.