Submitted By: Allison Strauss, Annual Adventure Maven

See Part 1 here.

April 26, 2011

Ponderosa Pine Forests

Field Example: Black Forest, Colorado

“Of all the pines, this one gives forth the finest music to the winds.” 

—John Muir on Ponderosa Pines

Young ponderosas hugging at Section 16, Colorado Springs

Introduction to Ponderosa

“The range of ponderosa pine essentially defines the West. From Nebraska to California, and from Southern British Columbia to Northern Mexico, ponderosa pine is the dominant forest tree of the montane zone in Western North America.”

—Audrey Delella Benedict, The Naturalist’s Guide to the Southern Rockies

There are three kinds of ponderosa, the one in the Southern Rockies being the Rocky Mountain Ponderosa Pine.

Ponderosa is the Goldilocks tree. It likes a temperate climate—not too hot, not too cold, not too wet, not too dry.

Ponderosa Dispersion & Fire

Ponderosa ideally grow in clumps in open grassy areas. American pioneer accounts describe ponderosa forests as “park like” with grass “stirrup-high.”

Trees, like most large species, favor longevity over high reproduction. Ponderosa saplings therefore grow in the open grass, away from the clumps of their mothers, sparing the mature trees competition. Each clump of trees, therefore, is of one generation.

Clumping in the grassland keeps fires regular and low impact. Fire, like water, takes the most direct course, which in this case is through the open channels of grass. Most saplings burn, but those that make it to maturity are then out of harm’s way.

But Black Forest, like most ponderosa forests today, is not park-like. Europeans brought the practice of fire suppression to North America, and the U.S. Forest Service has followed in this tradition, putting out all fires, not distinguishing between emergencies and regular low-level ones. Without their population control mechanism (channels of grass), ponderosa forests have grown dense so now virtually all fires are emergencies.

Black Forest is in fact named for its density, displaying a random pattern of dispersion. The trees are all about the same age, probably around 100 years old, rather than there being clumps of different generations.

The European perspective sees forest fires as wasted lumber. Ponderosa pine is the second most harvested type of lumber in North America. (#1 is Douglas fir.) The irony is, now there’s nowhere for fires to go without burning these very trees.

This is further perpetuated by aggressive brush clearance, which has also taken a toll on wildflowers.

Ponderosa’s Best Friend

Underground truffles (fungi) are integral to ponderosa and other pines. They wrap around the tree roots, essentially becoming one with them. This combination is called Mycorrhiza (fungi-root). Mycorrhiza increase the tree’s intake of water and nutrients from the soil.

Being underground, untouched by the wind, truffles rely on animals for dispersion. Animals dig them up, eat them, and poop out the spores elsewhere.

Abert’s squirrels also eat ponderosa phloem (part of the trunk that transports sap), which they live off exclusively through the winter, making Abert’s squirrels an indicator species of ponderosa forest health.

Ponderosa’s Enemy

Dwarf mistletoe is a parasite to ponderosa. It can only produce 3-4% of its own energy, so it grows on tree branches, sucking out the carbohydrates (sugar) and water, the tree’s own food. This makes it hard for the tree to photosynthesize, and may render it barren.

Dwarf mistletoe disperses its seeds in summer, when the fruit explodes, shooting gooey seeds as far as 20 feet at up to 50 miles per hour!

Black Forest is highly infected with dwarf mistletoe.

Gamble’s Oak

There are also Gamble’s oak in Black Forest, the only oak native to Colorado. Like other oaks, Gamble’s mast. Masting species let seed heavily in some years, and little to none in others, but all members of a local population let the same amount at once. For example, one year, a population may drop all of its acorns, but then drop a few to none in the next three years. They’re “irregular and synchronous.”

Black Forest also has a ground cover of delightfully named kinnikinnick, which bears eat.

Submitted By: Allison Strauss, Annual Adventure Maven

Professor Marc Snyder left his one non-EV majors class for the last academic block of the year. By April, it was a pleasure to take general-requirement kids out to the woods every day and show them stuff.

In 2011, I was one of those general-requirement kids. The class was called Forest Ecology of the Colorado Front Range. That’s a colloquial term for the eastern edge of the Rockies where the state’s major cities are, including my school’s home of Colorado Springs. (Yes, Planned Parenthood-attack Colorado Springs. But sometimes known for Pikes Peak and the U.S. Olympic Training Center.)

Each morning, we piled into a van, and Marc would drive to a spot that exemplified whatever type of forest or ecological phenomenon he wanted to talk about that day. I’d jot down his commentary and sketch things in a small notebook that would inevitably get wet and crumpled.

In the evening, I’d convert my chicken-scratch to long form in a journal, then take notes on the night’s assigned reading, primarily from The Naturalist’s Guide to the Southern Rockies by Audrey Delella Benedict.

By the end of the course, my journal had become something of a guide book of its own, a layperson’s introduction to Forest Ecology of the Colorado Front Range. Now, with some editing and personal photographs, I’m sharing that guide here. Welcome to the first installment!

April 25, 2011

Forests by Altitude & Direction

The Southern Rockies Life Zone (where there are complete ecosystems) falls between the upper and lower Tree Lines. Trees only grow so far down a mountain because of draught, and so far up a mountain (approximately 11,500 feet) because of cold and wind. Different kinds of trees have their elevation preferences within the life zone, so the type of forest changes as one moves up a mountain. These forests distinguish different ecosystems.

North-facing slopes get less sun, meaning they’re cooler and hold snow longer. Higher elevation species, like spruce and fir, are more prominent on North-facing slopes, because the all-over climate is more like that normally just at high elevation. By the same token, South-facing slopes are the most temperate.

Ecosystem Participation

When a glacier melts, or a forest burns, or a quarry is a abandoned, the site becomes available for a new ecosystem. The order in which species appear there is called Succession.

First come the Colonizers. “Good colonizers exhibit rapid growth and a high tolerance for the sorts of environmental extremes associated with disturbed or newly exposed sites” (Benedict). Aspen and Lodgepole Pine are common colonizers.

Aspen at Crater Lake, with view of the Maroon Bells, Colorado

Most species are Generalists. They can adapt to and are therefore found in a broad range of ecosystems. Probably the Southern Rockies’ most successful generalists are the coyote and deer mouse.

Opposite of the Generalists are the Specialists. These species only live in specific conditions, like pika in high elevation talus, and Abert’s squirrel (Professor Marc Snyder’s specialty—I suspect he is one) in ponderosa forests.

Pika and Abert’s squirrel

Because of their sensitivity, specialist presence indicates the health of a given ecosystem. So specialists are also known as Indicator Species.

***

Much of this seemed obvious, things I had a sense of just by spending time in the environments described. Of course ecosystems change with altitude, for instance. But I hadn’t recognized that they do so in a consistent way from mountain to mountain. I’d imagined more of a patchwork where there were distinct horizontal bands. Having such realities parsed out and learning the vocabulary to sum them up gave form to my free-flowing observations from the trail. The overarching lesson for me was that very little in nature is arbitrary. The natural systems at work became all the more impressive.