Dating the origins of persistent oak shrubfields in northern New Mexico using soil charcoal and dendrochronology

Christopher I. Roos, Christopher H. Guiterman

Research output: Contribution to journalArticlepeer-review

Abstract

Megafires in dry conifer forests of the Southwest US are driving transitions to alternative vegetative states, including extensive shrubfields dominated by Gambel oak (Quercus gambelii). Recent tree-ring research on oak shrubfields that predate the 20th century suggests that these are not a seral stage of conifer succession but are enduring stable states that can persist for centuries. Here we combine soil charcoal radiocarbon dating with tree-ring evidence to refine the fire origin dates for three oak shrubfields (<300 ha) in the Jemez Mountains of northern New Mexico and test three hypotheses that shrubfields were established by tree-killing fires caused by (1) megadrought; (2) forest infilling associated with decadal-scale climate influences on fire spread; or (3) anthropogenic interruptions of fire spread. Integrated tree-ring and radiocarbon evidence indicate that one shrubfield established in 1664 CE, another in 1522 CE, and the third long predated the oldest tree-ring evidence, establishing sometime prior to 1500 CE. Although megadrought alone was insufficient to drive the transitions to shrub-dominated states, a combination of drought and anthropogenic impacts on fire spread may account for the origins of all three shrub patches. Our study shows that these shrubfields can persist >500 years, meaning modern forest-shrub conversion of patches as large as >10,000 ha will likely persist for centuries.

Original languageEnglish (US)
Pages (from-to)1212-1220
Number of pages9
JournalHolocene
Volume31
Issue number7
DOIs
StatePublished - Jul 2021

Keywords

  • alternative stable states
  • anthropogenic pyrodiversity
  • ponderosa pine

ASJC Scopus subject areas

  • Global and Planetary Change
  • Archaeology
  • Ecology
  • Earth-Surface Processes
  • Palaeontology

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