Recent regional tree die-off events appear to have been triggered by a combination of drought and heat – referred to as ‘global-change-type drought’. To complement experiments focused on resolving mechanisms of drought-induced tree mortality, an evaluation of how patterns of tree die-off relate to highly spatially variable precipitation is needed.
Here, we explore precipitation relationships with a die-off event of pinyon pine (Pinus edulis Engelm.) in southwestern North America during the 2002–2003 global-change-type drought. Pinyon die-off and its relationship with precipitation was quantified spatially along a precipitation gradient in north-central New Mexico with standard field plot measurements of die-off combined with canopy cover derived from normalized burn ratio (NBR) from Landsat imagery.
Pinyon die-off patterns revealed threshold responses to precipitation (cumulative 2002–2003) and vapor pressure deficit (VPD), with little to no mortality (< 10%) above 600mm and below warm season VPD of c. 1.7 kPa.
Our results refine how precipitation patterns within a region influence pinyon die-off, revealing a precipitation and VPD threshold for tree mortality and its uncertainty band where other factors probably come into play – a response type that influences stand demography and landscape heterogeneity and is of general interest, yet has not been documented.
Clifford M.J., Royer P.D., Cobb N.S., Breshears D.D., and Ford P.L. (2013): Precipitation thresholds and drought-induced tree die-off: insights from patterns of Pinus edulis mortality along an environmental stress gradient. New Phytologist 200(2): 413-421. DOI: 10.1111/nph.12362
This Paper/Book acknowledges NSF CZO grant support.