The future existence of the Whitebark Pine trees is in peril with beetle infestations and the outbreak of tree diseases causing mass deaths.
The Whitebark Pine tree found in mountains is integral to water resources and wildlife of the United States and Canada. However, the future existence of some of these trees is questionable owing to various circumstances. Firstly, according to a press release by the National Science Foundation (NSF), the population of some of these trees has decreased by 91 percent over the last decade. Moreover, severe beetle infestations have caused surviving trees to lose their ability to produce their usual abundant seeds.
Ecologist Joshua Rapp, affiliated with NSF's Harvard Forest Long-Term Ecological Research (LTER) site and lead author of the paper says that this reduction of seed production also leads to reduction of regeneration. These trees are known to produce a high number of seed cones every alternate year. Male pollen cones, female seed cones, wind and proximity are four factors that affect this variation. The air carries male pollen cones to fertilize female seed cones that are usually seen atop other nearby trees.
"In low-cone years, less pollen is released, reaching extremely few female cones," says Elizabeth Crone, senior ecologist at the NSF Harvard Forest LTER site and co-author of the paper. "But as more and more whitebark pines die, every year becomes a low-cone year."
Authors of the study also reveal that in some areas where the tree grows, the gene pool is also depleting, which means that it would become less viable over time.
"For decades, researchers have struggled to understand why many different organisms--trees, fish, corals, insects--from various habitats reproduce synchronously and at certain intervals," says Saran Twombly, program director in NSF's Division of Environmental Biology, which funded the research. "By combining field data on seed and pollen production for whitebark pines with models that simulates mature cone production, this study helps to answer that question for these pines."
For the study, researchers analyzed seven areas where whitebark pine grew and counted the scars left by pollen cones and seed cones. They found that the years when the number of seed cone production was higher, the number of pollen cones was also higher. This made the authors conclude that the success of seeds depended on the amount of pollen produced each year.
These trees act as a food source for many animals in the mountainous regions. The extinction of such trees could also affect the habitats of the region. For example, squirrels store thousands of seeds underground. A diminished number of seed cones have an effect on grizzly bears that regularly raid squirrel seed caches to prepare for winter hibernation.
