Williams Creek - USWCR001
Tepley, Alan, J.;Veblen,Thomas,T.

Dating method: crossdated

Sample storage location: University of Colorado at Boulder, Department of Geography, Biogeography Lab, Guggenheim Hall, Campus Box 260, Boulder, CO 80309-0260

Reference:
Tepley, Alan, J.;Veblen,Thomas,T. 2015. Spatiotemporal fire dynamics in mixed-conifer and aspen forests in the San Juan Mountains of southwestern Colorado, USA. Ecological Monographs. DOI 10.1890/14-1496.1. 

Abstract: 
Mixed-severity fire regimes may be the most extensive yet poorly understood fire regimes of western North America. Understanding their long-term spatiotemporal dynamics is central to debates regarding altered fire regimes and the need for restoration in the context of changing climate and nearly a century of active fire suppression. However, the complexity of fire patterns and forest stand and landscape structures characteristic of mixed-severity regimes poses a substantial challenge to understanding their long-term dynamics. In this study, we develop analysis methods aimed at understanding the fire-driven forest dynamics of mixed-severity systems and apply them in the San Juan Mountains of southwestern Colorado. We sampled fire scars, stand structure, and >4,300 tree ages across two 1,340-ha landscapes (Williams Creek and Squaretop Mountain) that span the environmental gradient of montane mixed-conifer and aspen forests. New approaches were applied to identify pulses of tree recruitment, evaluate climate and fire as potential drivers of synchronous recruitment pulses, and combine fire scar and recruitment data to reconstruct fires. The reconstructions provided detailed fire history for each stand, which in turn was used to develop a fire-severity metric, compare fire frequency and severity by forest type, and develop a simulation procedure to evaluate the degree to which tree regeneration depended on fire by species within each forest type. Twenty fires were reconstructed since 1685 at Williams Creek and 13 fires since 1748 at Squaretop Mountain. Patterns of fire severity varied within each fire and over successive events, including high-severity patches of 100s of ha in both study areas. Dry mixed-conifer forests experienced relatively short fire intervals (mean 21 years) and low fire severity, and regeneration of the main conifer species was largely dependent on open conditions sustained over successive fires. Moist mixed-conifer forests experienced longer fire intervals (mean 32 years) and a 3 broader range of severities, and fire-caused canopy openings were important for initiating pulses of tree recruitment. Most (83%) aspen stands included two or more post-fire cohorts. The methods presented here can be adapted to other mixed-severity systems to better understand their long-term spatial and temporal dynamics and develop restoration priorities. 

NOAA/IMPD web landing page for this fire history site is available at:
http://ncdc.noaa.gov/paleo/study/18896

NOAA/IMPD DIF metadata record for this fire history site is available at:
http://www1.ncdc.noaa.gov/pub/data/metadata/published/paleo/dif/xml/noaa-fire-18896.xml

FHX filename: uswcr001.txt

IMPD code: USWCR001

Name of site: Williams Creek

Site code: WCR

Contributors: Tepley, Alan, J.;Veblen,Thomas,T.

Latitude: 37.526443 (WGS84)

Longitude: -107.235773 (WGS84)

Mean elevation: 2698 (meters)

Country: United States

State: Colorado

Region: southwestern Colorado

First year: 1459 AD

Last year: 2013 AD

Species name: Pinus ponderosa [PIPO], Pseudotsuga menziesii [PSME], Abies concolor [ABCO], Populus tremuloides [PPTR]

Funding agency names and grant numbers: 
National Science Foundation Partnerships for International Research and Education (PIRE)[OISE-0966472]

Comments:
The fire-scar dataset was collected as part of a study using fire scars and forest stand- and age-structure data to reconstruct the fire history and fire-driven forest dynamics across the gradient from dry to moist mixed-conifer and aspen forests in the San Juan Mountains of southwestern Colorado. The Williams Creek study area is 1,330 ha located west of the Williams Creek Reservoir, approximately 33 km northwest of Pagosa Springs (within the Pagosa Ranger District of the San Juan National Forest). Sampling of forest stand- and age-structure data was conducted in 33 contiguous stands across the study area. Fire scars were collected by searching while hiking to and from each transect, searching the area around each transect, and by making additional trips at the end of the field season to help fill spatial gaps in the dataset. Scars were sampled preferentially from dead trees, but live trees were also sampled to better represent recent fires and to provide a fire record in stands where ponderosa pine was absent and scars were poorly preserved on dead stems of the more rapidly decaying species. Ponderosa pine accounts for 66% the samples. The remaining samples are from white fir (28%)  Douglas-fir (5%)  and aspen (1%)  The fire-scar data were analyzed along with the age-structure data to reconstruct the extent and severity of each major fire event since the late 17th century.  Lowest elevation: 2522 meters, Highest elevation: 3054 meters. Individual sample information is located at: http://www1.ncdc.noaa.gov/pub/data/paleo/firehistory/firescar/northamerica/supplemental/uswcr001-individual-sample-information.csv . Alan J. Tepley (Alan.Tepley@Colorado.edu or tepleya@gmail.com).

Fire History Graphs: Fire History Graphs illustrate specific years when fires occurred and how many trees were scarred. They are available in both PDF and PNG formats. The graphs consist of 2 parts, both of which show the X axis (time line) at the bottom with the earliest year of information on the left and the latest on the right. The Fire Index Plot is the topmost plot, and shows two variables: sample depth (the number of recording trees in each year) as a blue line along the left Y axis, compared with the percent trees scarred shown as gray bars along the right Y axis. Below, the Fire Chronology Plot consists of horizontal lines representing injuries by year on individual sampled trees. Symbols are overlain that denote the years containing the dendrochronologically-dated fire scars or injuries. The sample ID of each tree is displayed to the right of each line. The Composite Axis below represents the composite information from all individual series. The symbols used to represent the fire scars or injuries, and the filters used to determine the composite information, are shown in the legend. These graphs were created using the Fire History Analysis and Exploration System (FHAES). See http://www.fhaes.org for more information.