For the new study, Redmond revisited nine pinyon pine study sites scattered throughout New Mexico and Oklahoma that had been studied previously in 1978 by Forcella. Both Forcella and Redmond were able to document pinyon pine masting years by counting small, concave blemishes known as "abscission scars" on individual tree branches that appeared after the cones have been dropped, she said.
Since each year in the life of a pinyon pine tree is marked by a "whorl" -- a single circle of branches extending around a tree trunk -- the researchers were able to bracket pinyon pine reproductive activity in the nine study areas for the 1969-1978 decade and 2003-2012 decade, which were then compared.
Pinyon pines take three growing seasons, or about 26 months, to produce mature cones from the time of cone initiation. Low elevation conifers including pinyon pines grow in water-limited environments and have been shown to have higher cone output during cool and/or wet summers, said Redmond. In addition to the climate-warming trend under way in the Southwest, the 2002-03 drought caused significant mortality in pinyon pine forests, Redmond said.
"Miranda's ideas and accompanying results will be of value to ecologists and land managers in the deserts of the Southwest and beyond," said Forcella, now a research agronomist in the USDA's Agricultural Research Service. "The work is evidence that the University of Colorado continues to cultivate a cadre of high-caliber graduate students for which it rightfully can take tremendous pride."
Pinyon nuts, the Southwest's only commercial source of edible pine seeds today, were dietary staples of indigenous Americans going back millennia.
|Contact: Miranda Richmond|
University of Colorado at Boulder