# **************************************************************** # ** Please acknowledge the contributors and the International ** # ** Multiproxy Paleofire Database when using these data. ** # **************************************************************** # # Site name: Archuleta Mesa Plot AA15 # Investigators: Peter M. Brown and Rosalind Wu # # Dating Method : Crossdated # Collectors : Peter M. Brown, Rosalind Wu # Species name : Pinus ponderosa, Juniperus scopulorum # Common name : ponderosa pine, Rocky Mountain juniper # Country : United States # State : Colorado # National Forest: San Juan National Forest # Ranger district: Pagosa # UTM easting : 0299134 (NAD83, 13) # UTM northing : 4116229 (NAD83, 13) # Elevation : 2249 m # Slope : 8 deg # Aspect : 232 deg # Sample Storage Location: Rocky Mountain Tree-Ring Research, Inc., # Ft. Collins, CO # # Fire scar data from this site are available in FHX2 format at: # ftp://ftp.ncdc.noaa.gov/pub/data/paleo/firehistory/firescar/northamerica/usach010.fhx # along with associated metadata at: # ftp://ftp.ncdc.noaa.gov/pub/data/paleo/firehistory/firescar/northamerica/usach010.txt # # Methods: See Brown and Wu 2005. Increment cores were removed from 10 cm # height above ground level on living trees and cross sections were cut # from logs and snags such that one surface was 10 cm above the estimated # root-shoot boundary. Sampled cores were no more than a field estimated # 10 yr from pith to minimize pith offset when assessing pith date. On # increment cores and cross sections that did not include pith but inside # ring curvature was visible, pith dates were estimated using overlaid # concentric circles of varying diameters that take into account both # average inside ring widths and an estimated distance to pith. Pith dates # at 10 cm height were corrected to germination dates by subtracting # 5 yr, the average time we estimated for seedlings to grow from germination # to 10 cm height (P. M. Brown, unpublished data). # # Reference: P.M. Brown & R. Wu. 2005. Climate and disturbance forcing of # episodic tree recruitment in a southwestern ponderosa pine landscape. # Ecology 86:3030-3038. # # Abstract: Strong but relatively short (annual to decadal length) climate # change can have broad-scale and long-lasting effects on forest communities. # Climate impacts forests through direct effects on tree demography (mortality # and overstory recruitment) and indirect effects on disturbance regimes. # Here, we compare multicentury chronologies of tree recruitment from a # 307-ha ponderosa pine forest in southwestern Colorado to reconstructions # of fire years, hydroclimate, and the El Nino-Southern Oscillation (ENSO). # Few trees predate a regional multiyear megadrought centered in the 1580s. A # prolonged pluvial in the early 1600s resulted in a pulse of tree recruitment # that corresponds to recruitment seen over much of the Southwest. Other cohorts # in the early 1700s and mid-1800s established during multidecadal fire- # quiescent periods. These periods correspond to shifts in ENSO that apparently # resulted in dampening of interannual wet/dry oscillations responsible for # fuel buildup and drying. Fires, mediated by stochastic climate variation, # acted as a density independent regulation on tree populations since # establishment was not limited by overstory tree density, but rather by # fire-caused mortality of seedlings and saplings during periods of more # frequent fires. Even-aged cohorts in ponderosa pine forests likely have # little if anything to do with episodic mortality caused by more severe # fires, but rather relate mainly to episodic recruitment opportunities. # Fire cessation after Euro-American settlement in the late 1800s resulted # in an increase in tree density and changes in forest composition, which # are major factors that have contributed to recent severe wildfires in other # Southwestern forests. Our results document clear linkages between synoptic # climate forcing, fires, and recruitment episodes, and highlight the # importance of regional historical processes on contemporary forest # composition and structure. # # Comments: The first 2 letters of the tree ID represents the species: PP=Pinus # ponderosa, JS=Juniperus scopulorum. # 1 Tree ID 2 Year 3 Feature PPAA151,1909,pith PPAA151,2002,bark PPAA152,1905,pith PPAA152,2002,bark PPAA153,1908,pith PPAA153,2002,bark PPAA154,1882,pith PPAA154,2002,bark PPAA155,1907,pith PPAA155,2002,bark PPAA156,1905,pith PPAA156,2002,bark PPAA157,1739,pith PPAA157,1980,bark PPAA158,1908,pith PPAA158,2002,bark PPAA159,1890,pith PPAA159,2002,bark JSAA1510,1924,pith JSAA1510,2002,bark PPAA1511,1620,pith PPAA1511,1833,last ring PPAA1513,1602,pith PPAA1513,1742,last ring JSAA1514,1928,pith JSAA1514,2002,bark PPAA1515,1599,earliest ring PPAA1515,1688,injury undetermined PPAA1515,1709,fire scar latter earlywood PPAA1515,1724,fire scar dormant postition PPAA1515,1749,last ring PPAA1516,1931,pith PPAA1516,2002,bark PPAA1517,1917,pith PPAA1517,2002,bark PPAA1518,1922,pith PPAA1518,2002,bark PPAA1519,1928,pith PPAA1519,2002,bark PPAA1520,1923,pith PPAA1520,2002,bark JSAA1521,1902,pith JSAA1521,2002,bark PPAA1522,1616,pith PPAA1522,1978,bark PPAA1523,1620,pith PPAA1523,1826,last ring JSAA1524,1904,pith JSAA1524,2002,bark PPAA1526,1485,pith PPAA1526,1505,fire scar latewood PPAA1526,1516,fire scar middle earlywood PPAA1526,1648,last ring JSAA1528,1898,pith JSAA1528,2002,bark PPAA1529,1726,pith PPAA1529,1851,fire scar latter earlywood PPAA1529,1861,fire scar undetermined PPAA1529,1894,last ring PPAA1530,1898,pith PPAA1530,2002,bark