13,000 years of fire history derived from soil charcoal in a British Columbia coastal temperate rain forest

Abstract

Little is known regarding the fire history of high‐latitude coastal temperate rain forests in the Pacific Northwest (PNW) of North America. While reconstructing historical fire regimes typically requires dendrochronological records from fire‐scarred trees or stratigraphically preserved lake sediment data, this type of information is virtually non‐existent in this region. To describe the long‐term fire history of a site on the central coast of British Columbia, Canada, we radiocarbon‐dated 52 pieces of charcoal. Charcoal ages ranged from 12,670 to 70 yr BP. Fires occurred regularly since 12,670 yr BP, with the exception of a distinct fire‐free period at 7500–5500 yr BP. Time since fire (TSF) estimates from soil charcoal and fire‐scarred trees ranged from 12,670 to 100 yr BP (median = 327 yr), and 70% of the sites examined had burned within the past 1000 yr. An increase in fire frequency in the late Holocene is consistent with the widely held hypothesis that anthropogenic fires were common across the PNW. We evaluate TSF distributions and discuss the difficulties in assigning actual fire dates from charcoal fragments with large inbuilt ages in a coastal temperate rain forest setting. We determine that a comprehensive approach using soil charcoal and fire scar analyses is necessary to reconstruct general trends in fire activity throughout the Holocene in this region.

Seven hundred years of human-driven and climate-influenced fire activity in a British Columbia coastal temperate rainforest

“…For example, in our analyses, we found that fire events were not spatially biased to expected locations such as south-facing aspects [42], steep slopes [20] or rocky outcrops at middle and high elevations [19], but were strongly associated with the locations of former habitation sites (figure 3). We also found no difference in the frequency of fire events across the four vegetation types despite dissimilarities in fuel load, fuel availability and potential flammability (electronic supplementary material, figure 4) [21]. Although the effects of topography and vegetation on fire frequency were not readily apparent, the variables aspect and bog forest vegetation type were included in our final model selection (based on weighted probabilities) along with distance to former habitation site (table 1 b ).…”

“…Blanket bogs are nutrient-poor, sparsely forested wetland areas that contain small amounts of shore pine and yellow-cedar [33]. Zonal and bog forest vegetation types have closed canopies with larger diameter and more vertical fuel structures that are blanketed by thick moss compared with bog woodland and blanket bog vegetation types, which are more open, drier and contain finer, more flammable fuel assemblages [14,21]. Elevations in the study area range from sea level to 150 m, and the geological substrate is homogeneous quartz diorite and granodiorite [36].…”

A global hotspot for dissolved organic carbon in hypermaritime watersheds of coastal British Columbia

“…When compared to watersheds of similar size, DOC yields from Calvert and Hecate island watersheds are some of the highest observed (see reviews in Hope et al, 1994;Alvarez-Cobelas et al, 2012), including DOC yields from many tropical rivers, despite the fact that tropical rivers have been shown to export very high DOC (e.g., Autuna River, Venezuela, DOC yield: 56 946 kg C km −2 yr −1 ; Castillo et al, 2004) and are often regarded as having disproportionately high carbon export compared to temperate and Arctic rivers (Aitkenhead and McDowell, 2000;Borges et al, 2015). Our estimates of DOC yield are comparable to, or higher than, previous estimates from high-latitude catchments of similar size that receive high amounts of precipitation and contain extensive organic soils and wetlands (e.g., Naiman, 1982 (DOC yield: 48 380 kg C km −2 yr −1 ); Brooks et al, 1999 (DOC yield: 20 300 kg C km −2 yr −1 ); Ågren et al, 2007 (DOC yield: 32 043 kg C km −2 yr −1 )).…”

Indigenous peoples’ habitation history drives present‐day forest biodiversity in British Columbia's coastal temperate rainforest

“…Forests in this region have been shaped by an extensive anthropogenic fire history (Hoffman, Gavin, Lertzman, Smith, & Starzomski, ; Hoffman, Gavin, & Starzomski, ; Hoffman, Lertzman, & Starzomski, ) and despite the habitation sites being abandoned for over 125 years, the productivity of modern forests growing on habitation sites shows the enhanced productivity (Trant et al., ). Little is known, however, about how these long‐term human modifications have influenced understory vegetation.…”