As a girl raised among the dense rainforests of the Pacific Northwest, crowded with ferns, rhododendrons, and dripping with primordial mosses, my first glimpse of a Northern Arizona forest was a little disconcerting. Frankly, there just wasn't that much to it. From the roadside, all you see is a carpet of grass, lanky tree trunks spaced unsociably apart, and not much else. I was sure this was a sign of something amiss, but later learned this is just what a good stand of ponderosa pine should look like. The way the ponderosa pine has evolved to survive the complex environment of the Southwest's high country was counterintuitive to the Europeans who settled here, too, and those now responsible for our forests' health are just beginning to understand the dynamic give-and take among the trees, the animals and the elements.
The dignified, hardy ponderosa pine has long been a symbol of the wild American West, and the tree has done particularly well for itself in Arizona. They're found throughout the West from Canada to Mexico, but the stand stretching from Flagstaff along the Mogollon rim to the White Mountains is reportedly the largest continuous stand on the continent. The region's mild wet winters, and pattern of precipitation and dry spells throughout the year make it prime ponderosa habitat.
They're easy to identify, with reddish-brown bark marked by long, mostly vertical black fissures. They produce elegant long needles several inches long and compact pinecones that are a dietary staple among forest birds and mammals. Seedlings can send down deep taproots quickly to soak up as much moisture as possible in this arid region, and mature trees that live atop rock with deep fissures can send their roots down the cracks as far as 40 feet.
Walk through a stand around Flagstaff, or maybe on Mingus Mountain in the heat of the summer, and the air will be heavy with the vanilla-pine-incense scent of the bark. Summer is also a critical time of year for the survival of a healthy stand. Monsoon season brings moisture, but it also brings lightning storms that can spark forest fires, which are actually beneficial events in the forests' own natural maintenance cycle.
Before people began tinkering with the system, a typical low-density forest of big mature pines, spaced widely apart, with grasses underneath created the conditions for frequent but low-intensity surface fires. These fires, which came along every couple of years in some areas, would burn up the grasses, ponderosa seedlings and any other competing trees, leaving the big trees maybe a little scarred, but largely unharmed, and free of any competition for nutrients below. When European settlers introduced grazing cattle which cleared out the grasses, and fire suppression which allowed more seedlings and competing foliage to mature, the balance was disturbed. The taller saplings and denser undergrowth create a "fuel-ladder" that carries fire straight up into the canopy, increasing the intensity and destruction of the burn.
