South Fork, Part 3

What happened at South Fork? Here’s what. Since time immemorial low-intensity fires have frequented the South Fork forest. I detected seven fires over a period of 250 years, from 400 years ago to 150 years ago. I probably failed to detect that many or more. It seems that, in the past, fire visited South Fork every 10 to 30 years, probably for centuries.

The frequent fires consumed the understories, probably grasses, small brush, and tree seedlings initiated by the prior fire. The frequent fires did not consume the large, thick-barked, wide-spaced trees. Perhaps one seedling per acre survived subsequent fires and eventually joined the scattered giants towering over prairie-like, frequently-incinerated, low-to-the-ground vegetation.

The last such fire occurred about 1840. Since then fire has been absent. No doubt every conifer species in the park-like overstory shed seed soon after (and frequently since) the last fire. Pine seedlings probably got established and started to grow first. Douglas-firs quickly followed. Grand fir seedlings probably also germinated within a few years of the last fire, but grand fir seedlings can remain tiny and nearly dormant for decades. Eventually, perhaps fifty years later, the grand fir seedlings started to grow. Few other species thrive in dense grand fir thickets, and the early post-fire pioneer pines and Douglas-firs got crowded out at South Fork.

Today the thicket of grand fir remains, together with the mixed-conifer trees of the older cohorts. The latter are dying, though. At South Fork large snags are as frequent as large living trees. Measurements were made on snags of all the cohorts. Evidence suggests that half the trees established prior to 1840 have died since, most within the last 50 years. In 1840 South Fork had about 15 trees per acre. Today half those trees are still alive, along with 1,000 resinous and decadent grand firs per acre. The absence of fire has turned South Fork from an open, grassy, park-like forest into a kindling pile of sick and dying trees.

So where did the fires go? Some people blame “fire suppression”, but that argument doesn’t comport with the facts. The US Forest Service wasn’t established until 1905. In the 1930’s the Tillamook (and other) Fires were fought by men on horseback. It wasn’t until after the Korean War that decent roads, bulldozers, helicopters, and retardant-dropping air tankers were added to fire-fighting arsenals. In other words, there was no significant, effective fire suppression at South Fork for at least 110 years following the last fire. If a fire started today at still remote South Fork, with its enormous fuel build-up, all the modern fire suppression technology in the world wouldn’t be able to put the fire out. No, I’m sorry, but the fire suppression hypothesis doesn’t wash.

If the natural fire frequency at South Fork was one every twenty years, then why has Mother Nature missed Her last eight appointments? Did lightning diminish recently; is lightning an endangered phenomenon about to go extinct? Noooo, obviously not.

What happened to the fires?