2011-05-31

How Lodgepole Pines Protect Their Kind Against Fire, Mountain Pine Beetles Infestation

As mountain pine beetles march across the forests of western North America, these insects may kill millions of pine trees during a single outbreak. A rise in overall temperatures over the past several years has increased the range of mountain pine beetles, resulting in an epidemic and possibly making this mountain pine beetle infestation the largest forest-insect blight to occur in North America.

Dr. Francois Teste and colleagues from the University of Alberta in Canada have been investigating the effect of mountain pine beetle outbreaks on lodgepole pines in British Columbia. Teste and colleagues have discovered that seeds from cones on the forest floor may provide a viable seed bank for lodgepole pine regeneration following forest destruction by mountain pine beetles. Their research is published in a recent issue of the American Journal of Botany.

Lodgepole pines, a variety of the pine species Pinus contorta, are a serotinous species -- the seeds are only released from the cones in response to specific environmental conditions, in this case fire, rather than at the time of seed maturation. The seed bank of lodgepole pines is found in closed cones, which generally are located in the canopy. Following a mountain pine beetle outbreak, dead trees with canopy cones may remain standing for 10 to 15 years. However, scientists have observed a considerable increase in closed cones on the forest floor due to an increase in branch breakage after tree death. The viability of these canopy and forest-floor seeds and the likelihood that they will be able to contribute to forest regeneration has not been known.