Bibliographic Metadata :
Climatic influences on fire regimes in the northern Sierra Nevada mountains, Lake Tahoe Basin, Nevad
Title
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Climatic influences on fire regimes in the northern Sierra Nevada mountains, Lake Tahoe Basin, Nevada, USA
Secondary Title
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Journal of Biogeography
Authors
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Taylor, A. H.; Beaty, R. M.
Place Published
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Publish Date
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2/22/2005 12:00:00 AM
Year
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2005
Publisher
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Journal of Biogeography
Source
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Wiley InterScience
ISSN/ISBN
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Issue
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3
Keywords
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Tahoe, fire, tree rings, Jeffrey pine, climate, EPOCH analysis, 2009-symposium
Text
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32
Pages
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425-438
Abstract
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The goal of this study was to understand better the role of interannual and interdecadal climatic variation on local pre-EuroAmerican settlement fire regimes in fire-prone Jeffrey pine (Pinus jeffreyi Grev. & Balf.) dominated forests in the northern Sierra Nevada Mountains. Location Our study was conducted in a 6000-ha area of contiguous mixed Jeffrey pine-white fir (Abies concolor Gordon & Glend.) forest on the western slope of the Carson Range on the eastern shore of Lake Tahoe, Nevada. Methods Pre-EuroAmerican settlement fire regimes (i.e. frequency, return interval, extent, season) were reconstructed in eight contiguous watersheds for a 200-year period (1650-1850) from fire scars preserved in the annual growth rings of nineteenth century cut stumps and recently dead pre-settlement Jeffrey pine trees. Superposed epoch analysis (SEA) and correlation analysis were used to examine relationships between tree ring-based reconstructions of the Palmer Drought Severity Index (PDSI), Southern Oscillation Index (SOI), Pacific Decadal Oscillation (PDO) and pre-EuroAmerican fire regimes in order to assess the influence of drought and equatorial and north Pacific teleconnections on fire occurrence and fire extent. Results For the entire period of record (1650-1850), wet conditions were characteristic of years without fires. In contrast, fire years were associated with drought. Drought intensity also influenced fire extent and the most widespread fires occurred in the driest years. Years with widespread fires were also preceded by wet conditions 3 years before the fire. Widespread fires were also associated with phase changes of the PDO, with the most widespread burns occurring when the phase changed from warm (positive) to cold (negative) conditions. Annual SOI and fire frequency or extent were not associated in our study. At decadal time scales, burning was more widespread during decades that were dryer and characterized by La Nina and negative PDO conditions. Interannual and interdecadal fire-climate relationships were not stable over time. From 1700 to 1775 there was no interannual relationship between drought, PDO, and fire frequency or extent. However, from 1775 to 1850, widespread fires were associated with dry years preceded by wet years. This period also had the strongest association between fire extent and the PDO. In contrast, fire-climate associations at interdecadal time scales were stronger in the earlier period than in the later period. The change from strong interdecadal to strong interannual climate influence was associated with a breakdown in decadal scale constructive relationships between PDO and SOI. Main conclusions Climate strongly influenced pre-settlement pine forest fire regimes in northern Sierra Nevada. Both interannual and interdecadal climatic variation regulated conditions conducive to fire activity, and longer term changes in fire frequency and extent correspond with climate-mediated changes observed in both the northern and southern hemispheres. The sensitivity of fire regimes to shifts in modes of climatic variability suggests that climate was a key regulator of pine forest ecosystem structure and dynamics before EuroAmerican settlement. An understanding of pre-EuroAmerican fire-climate relationships may provide useful insights into how fire activity in contemporary forests may respond to future climatic variation.
Notes
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Fire regime High fire years were drought years preceeded by wetter than normal years. This phenomenon is common to ponderosa pine forests of the American Southwest and Mexico, but not typical for wetter forests of the Pacific Northwest. No connection to ENSO (El Nino/La Nina, tropical ocean) phenonemon was detected, but a connection to the PDO (longer-term cycle, North Pacific ocean) was detected. "Widespread burning occurred in years preceded by significantly positive PDO conditions (warm phase) followed by strongly negative ones (cold phase). The fire-PDO pattern in the northern Sierra Nevada is similar to the fire-ENSO switching pattern documented in SW and RM pine forests, but phase switching of the PDO is less frequent because it varies over longer (decadal) time scales." Fires were more common before 1775 than afterwards. After 1775, fire frequency "was confined mainly to dry years preceded by wet years that appears to be driven by phase changes from a warm to a cool PDO, but the relationship between fire extent and moisture was not consistent over decades." These understandings may help to predict fire dynamics due to future climate change, although authors caution that many factors have changed since the historic record (including changes in CO2 levels, increased availability of fuels due to fire suppression.). Date of Input: 2/27/2008 Priority: Normal Web: http://www.blackwell-synergy.com/doi/abs/10.1111/j.1365-2699.2004.01208.x
Reference Type
Journal Article