Wednesday, July 10, 2013

Ponderosa Production

Ponderosa pine immature male cones (c) John Ashley
Ponderosa pine male cones 
We could learn a thing or two about patience from our stately state tree. Ponderosa pines (Pinus ponderosa) often live to be more than 600 years old, which means that some of the rare, elder trees we admire today were a young 360+ years old when the U.S. was formed and 475+ when Montana became a state.

Ponderosa pines are monecious, meaning that each tree bears both male and female flowers. Middle-aged trees produce most of the seeds. They begin producing cones at age 7 and continue until they're about 350 years old, but the vast majority of viable seeds are produced by those trees that are 60-100 years old.

Here in the northwest, ponderosa pines only have a good cone crop every 4-5 years, and even less frequently west of the continental divide in Montana. A single cone can nurse 30-60 seeds, and more than 345,000 seeds per acre can reach the ground from a good crop. The highest production rates occur when a good cone crop is followed by a wet year.

This year's male cones are now spent, having produced yellow clouds of pollen between late May and late June. Now these reddish cones are starting to break apart and fall from the trees. This year's female cones will reach full size about this time next year. In 2014, the 2013 seed crop will ripen in late August, the cones will open in early September, and the mature seeds will be shed through October.

These are trees that need their "personal space" to sprout, and saplings grow most rapidly in locations where they are drenched in full sunlight. Because they're shade intolerant, ponderosa pines typically occupy the first zone above grasslands. But they're missing from the low-elevation areas in grassy southeastern Montana because a paucity of summertime rainfall prevents seedlings from developing.

The thick, fire-resistant bark of mature trees protects ponderosa pines from the frequent, low-intensity fires that naturally occur in grasslands. But our fire suppression efforts have allowed shade-tolerant trees - especially Douglas fir - to encroach and crowd out the fire-resistant ponderosas. It also provides "ladder fuels" that allow ground fires to climb up into the canopy, above the ponderosas' thickest bark and into the more flamable branches and needles.

In this way, trees that lived for centuries without our help are now dying much younger because of our efforts to "save" trees from fire. How long will it take before the general public understands and accepts that fire is a natural phenomenon? How do you teach the Smoky Bear generation a little patience and basic ecology? Our elder ponderosa pines can teach us both.

Ponderosa pine trees release a cloud of pollen (c) John Ashley
Ponderosa pine trees release a yellow cloud of pollen, on Wildhorse Island in Flathead Lake