Environmental change in Garry oak (Quercus garryana) ecosystems: the evolution of an eco-cultural landscape

Marlow G Pellatt,Ze’Ev Gedalof

doi:10.1007/s10531-014-0703-9

Marlow G Pellatt, Ze’Ev Gedalof

Open Access

https://doi.org/10.1007/s10531-014-0703-9

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Abstract

Globally, colonialism resulted in the suppression of aboriginal land manage- ment practices, abetted by the concept of terra nullius, ''belonging to no one''; the belief that aboriginal people had little influence on or ownership of the land. Until recently, this ideology was entrenched in resource management and policy. Traditional ecological knowledge, historical ecology, archaeology, and palaeoecological research have shown these assumptions to be wrong. In this paper we take a multidisciplinary approach (bio- geography, paleoecology, dendrochronology, and bioclimatic envelope modeling) to better understand the role of climate and fire in the formation of eco-cultural landscapes. We synthesize results from pollen and charcoal analysis in Garry oak ecosystems that indicate there were continuous and frequent prescribed burning events, with more severe fires occurring every 26-41 years in southwest British Columbia throughout the Anthropocene (*last 250 years) that substantially altered forest structure and composition. These results are consistent with stand age reconstructions in BC and Washington with Garry oak establishment beginning *1850 AD, corresponding with modern fire exclusion, aboriginal population decline, and end of the Little Ice Age. Douglas-fir recruitment has been con- tinuous since *1900, with succession of oak woodland to closed conifer forest at most sites. These findings indicate that the structure of many Garry oak ecosystems have been profoundly influenced by eco-cultural practices. Overwhelming evidence indicates that in many cases these ecosystems are dependent on prescribed fire for their open structure. In

Highlights

Understanding the complex nature of Garry oak ecosystems and threats facing their continued existence has been the topic of many recovery actions throughout the Pacific Northwest of North America and has resulted in a number of papers at the technical and peer-reviewed level (Pellatt et al 2007 ; Dunwiddie et al 2011; Devine et al 2013; McCune et al 2013)
Dunwiddie and Bakker (2011) identified habitat loss and fragmentation, successional transition from open to forested conditions, and invasive species as the greatest threats to Garry oak ecosystems. They felt that the future challenges to be tackled by the management and scientific community include the reestablishment of prescribed burning, aboriginal plant harvest techniques (i.e., Camas bulbs), the need for climate change models that addressed Garry oak ecosystem adaptation at a scale relevant to land managers, and the selection of sites for restoration based on knowledge of their natural range of variability while being cognisant of the emergence of novel ecosystems
The role of climate change on these ecosystems has been examined (Bachelet et al 2011; Pellatt et al 2012), highlighting the importance of securing habitat that will be suitable for Garry oak ecosystems in the future if they are to persist amongst a populated, fragmented landscape, but it may be that more interventionist measures will be required to assist with Garry oak ecosystem migration

Summary

Introduction

Understanding the complex nature of Garry oak (aka Oregon white oak; Quercus garryana) ecosystems and threats facing their continued existence has been the topic of many recovery actions throughout the Pacific Northwest of North America and has resulted in a number of papers at the technical and peer-reviewed level (Pellatt et al 2007 ; Dunwiddie et al 2011; Devine et al 2013; McCune et al 2013). We synthesize results from pollen and charcoal analysis in Garry oak ecosystems that indicate there were continuous and frequent prescribed burning events, with more severe fires occurring every 26–41 years in southwest British Columbia throughout the Anthropocene (*last 250 years) that substantially altered forest structure and composition.

Results

Conclusion