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But inside the Manitou Experimental Forest, researchers are hard at work trying to discover how climate change is affecting this pristine environment, the process of regeneration after a fire, the population dynamics of flammulated owls, and ways to reduce the risk of catastrophic fire and insect attack in these forests.

Established in 1936 as part of the Forest Service's Rocky Mountain Research Station, the Manitou Experimental Forest, which lies about 28 miles northwest of Colorado Springs, Colo., in the South Platte River drainage, is one of 83 experimental forests and rangelands throughout the United States operated by the Agriculture Department.

Unlike other research components of USDA such as the Agricultural Research Service, the Forest Service's research divisions are not housed as separate agencies. While research at the experimental forests is often conducted in collaboration with other agencies, universities and nonprofits, Sam Foster, director of the Rocky Mountain Research Station, said the experimental forests focus on producing good science and being objective.

"One thing that we really try to do is maintain our independence," Foster said. "Otherwise, we're no use to anyone."

The latest research project to begin at the forest is known as the BEACHON project, which stands for Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O, Organics and Nitrogen. The project began July 21 and will last three to five years.

Researchers here are conducting studies on the roles of biogenic aerosols, nitrogen trace gases and oxidants in linking and regulating the carbon and water cycles. A major experimental focus is on the measurement, interpretation and modeling of surface fluxes of energy aerosols, carbon dioxide, water, and organic and nitrogen compounds.

Crystal Reed, a researcher with Texas A&M University, is looking at secondary organic aerosol production.

Atmospheric aerosols are small solid or liquid particles suspended in the atmosphere that can be classified as either primary or secondary based on their origin. Primary aerosol is directly emitted into the atmosphere, while secondary aerosol is formed through atmospheric chemical reactions. Secondary organic aerosol is produced by atmospheric oxidation of volatile organic compounds, emitted from both natural and anthropogenic sources.

"I'm looking at the effects of increasing pollution in environments such as this," Reed said. "In a pine forest like this, we tend to emit a lot of terpene gases, and these gases can be volatilized by different reactions in the environment and can condense on the surface of the particles as well as interact with the structure of the particle itself."

The monoterpenes, which are essentially hydrocarbons, are what you smell when you walk through a pine forest. When monoterpenes react in the atmosphere, they break down into condensable products that can condense onto existing tiny particles and cause them to grow or in some cases produce new particles.

For example, if someone built a power plant in the Pike National Forest, it would produce a lot of sulfate emissions and particles that are very harmful to human health. The gases emitted by the forest can then latch onto these particles, creating secondary organic particles that are even more detrimental to human health.

Using two atmospheric aerosol chambers that were designed at Texas A&M University and supported by Sandia National Laboratories in Albuquerque, N.M., Reed can inject particles into the top of the chamber. The inside of the chamber is exactly the same as the outside air.

"So I can inject these particles that are emitted from these power plants or repercussions of these particles, and I can track and see what happens," Reed said.

A novel approach to climate change research

Linda Joyce, research project leader at the experimental forest, said the research going on at BEACHON is important because not all of the effects of climate change can explain all the dynamics of the atmosphere when studying it from a physical standpoint. "They need to look at what's going on in the vegetation and the soil," she said.

"It turns out that plants emit these small particles, these volatile organic compounds. Those volatile organic compounds interact with other gases in the atmosphere, form ozone, cause pollution problems, and they also can affect the atmospheric processes like cloud formation. And that could have an impact then in terms of changing the way that climate works globally," she said.

Peter Harley, a scientist at the National Center for Atmospheric Research, based in Boulder, Colo., said BEACHON grew out of the need for more cross-disciplinary studies on climate change. In the past, it has been difficult to fund such projects, because most of the major funding agencies are compartmentalized into different specialties, such as biology, hydrology or atmospheric science. BEACHON is funded through the Institute for Integrative and Multidisciplinary Earth Studies, which, as its name suggests, aims to bridge the various earth science disciplines.

"This here is sort of the first attempt -- it's kind of a pilot study, preliminary study to see how this is going to work out," Harley said. "The idea here is basically, very fundamentally to look at interactions between the biosphere and the atmosphere -- in both directions."

Harley is overseeing a project by students from Colorado College in which clean air is emitted into a chamber containing pine needles. The students then measure what comes out the other side of the chamber to determine what the needles are emitting.

The BEACHON researchers are also erecting a 100-foot-tall tower -- expected to be completed by the end of the week -- to take measurements above the canopy of carbon dioxide, water, ozone, aerosols and a variety of other trace gases.

"There's some biology -- the emissions side of things, what are they emitting, what controls the emissions, how do they change over time, what's the effect of temperature and drought and ozone events and things like that -- and then there's a lot of atmospheric chemistry involved because we need to understand how these terpenes react in the atmosphere to produce these condensable particles, which go on to the aerosols," Harley said.

Globally, the formation of secondary organic aerosols from biogenic precursors surpasses that from anthropogenic sources. These organic particles have important effects on climate through their direct interactions with radiation, as well as their ability to modulate cloud properties and precipitation.

These processes exert a substantial feedback upon the earth through links to the terrestrial carbon and water cycles. For example, precipitation regulates plant growth and thus emissions or organic compounds, which are also influenced by changes in radiation.

The importance of aerosols in the hydrological cycle of the West

Biogenic volatile organic compounds are precursors to secondary organic aerosol formation and are widely known to affect tropospheric ozone formation. Biogenic VOCs also likely influence cloud cover and possibly precipitation, thereby playing a role in regulating the radiation balance and the hydrologic cycle.

In spite of their recognized importance, biogenic VOCs are still poorly understood. Direct measurements of hydrogen oxide reactivity in forests suggests that there is a significant source of biogenic VOCs that has not been identified yet.

Emission and transport of biogenic VOCs is directly linked to canopy conditions and the response of the canopy systems to environmental stresses.

Improved understanding of biogenic secondary aerosol formation, the roles that biogenic aerosols play in cloud formation, and possible feedbacks from clouds and precipitation is especially crucial in the dry ecosystems of the western United States. A recent study suggests that the Earth's changing climate has led to reduced water availability in the West during the last half century and will continue to do so in the future. Given the region's growing population, scientists believe that understanding the role of aerosols in the hydrological cycle of the West will be increasingly important.

"The relationship that we're positing here is that emissions from forests lead to particle production or growth, in some cases leading to growth in numbers and size of CCN [cloud condensation nuclei] particles, which affects cloud processes, affects not only precipitation potentially but also the radiative properties of clouds, whether they absorb more or less solar radiation, which has an impact on the climate in general," Harley said.

The clouds can absorb more or less radiation, depending on the nature of the particles. "Soot, which is black, tends to absorb radiation and heat the atmosphere locally, whereas if they're light-reflective particles, they reflect the radiation and have a cooling effect in the atmosphere," Harley said.

"When we talk about CO2, for example, acting as a greenhouse gas, there it's actually absorbing longer wave radiation as it's reflected from the surface and preventing it from getting back out. Whether the clouds act the same way, I honestly don't know," Harley added.

Ponderosa pine regeneration

Other research at the Manitou Experimental Forest includes a long-term project on ponderosa pine seed production and regeneration establishment.

"People were interested in finding out a little bit more information about how often seeds were produced and then how successful seedlings were once the seeds were produced," Joyce said.

The researchers, led by Forest Service Research Silviculturist Wayne Shepperd, started the research project in 1981. They used two standard silvicultural techniques -- a "shelterwood" cut and a "seedtree" cut. Fewer trees were left on site with a seedtree cut than with a shelterwood cut. Then the researchers went in and planted seedlings or left the sites in their natural condition. Some sites were also scarified with a tractor-mounted rototiller to help the seedlings get established.

They found that seedfall is dependent upon the density of overstory trees and varies considerably from year to year and that seedfall years producing fewer than 200,000 seeds per hectare had few viable seeds. The researchers also found that about half of the seedfall is consumed by animals, regardless of the total seed production, so even in good seedfall years, 14 percent of ponderosa pine seeds are available to germinate.

"The bottom line essentially was that seed production here in this part of the Rockies is episodic," Joyce said. "In contrast to up in the Black Hills, where ponderosa pine grows like weeds up there, we don't have that often of a combination of good climate and seed years to get seeds to produce and then seedlings to get established. And so, if you wanted a forest quickly, you should plant."

The project was in its 21st year when the 137,000-acre Hayman Fire hit in 2002, burning the seedlings and trees. Since the researchers already had a lot of long-term information on the plots in the study, they decided to look at fire recovery. The study looked at fire intensity across the plots and how the forest responded to the fires.

"What was interesting about those results was that the scarification treatment had a big influence on the understory that came back along with the trees, and you could still see that influence on the recovery of the understory vegetation after the fire," Joyce said.

The fire also took out a 1982 ponderosa pine spacing study, where seedlings were planted at different spacings and monitored for growth. The fire killed virtually all the trees in the study.

"That wiped out the whole study," Joyce said.

But the work on the Manitou Experimental Forest, including the fuel treatments and a timber sale, also helped to stop the Hayman fire.

"It kept the fire on the ground, and it enabled the fire crews ... to get out in front of the fire and build line and stop that fire," Steve Tapia, resident manager at the forest, said. "A lot of the fire managers attribute that success to that action."

"Had it ... gotten to the other side of the drainage going up the steep hills and gone to the top of the ridge, then we would've had long-range spotting into the Air Force Academy and in the forest that you see from the interstate looking back this way," Rocky Mountain Research Station spokesman Dave Tippets said. "That was kind of the exciting climax of the Hayman fire right here at Manitou."

Concern over invasives

Many scientists have done work on the Hayman fire itself, focused on the recovery. The work so far has shown that it is too early to tell what the likelihood of survival of seedlings will be, Joyce said.

Other studies have focused on the role of invasive species after the fire. Speaking of research showing a dramatic increase in the number of invasive species in the burned area, Tippets said, "There's a new seed source for new invasive species in the burned area, but they're not aggressively invading the burned area yet."

Because of the risk of invasive species taking over the burned areas, Forest Service officials have dedicated their resources to curbing the invasion of non-native species in the Hayman burn area, Tapia said.

"In our weed treatments that we do annually, the Hayman became the No. 1 priority," Tapia said. "We spent a lot more time treating invasive species in Hayman fire than in other locations, where we also have invasives. But we knew the propensity for the weeds to spread in the Hayman fire, so we directed resources more toward the Hayman than in other areas."

Ecosystem management

The Manitou Experimental Forest is also unique in that about 6,000 acres of private inholdings lie within the forest, including a major housing subdivision.

"It's interesting and unusual in that it has a subdivision inside of it, so it's a perfect example of what they call 'wildland-urban interface,' where you're dealing with a managed landscape and then folks living within it," Joyce said.

The forest consists of a series of small drainages that are populated with a structurally diverse ponderosa pine stand that has developed after logging that occurred during the late 1800s. Small portions of the site were harvested in the late 1940s as part of the early watershed experiments at the forest, but the rest of the forest has remained undisturbed by humans during the 20th century.

Researchers have done a number of silvicultural treatments on the forest to reduce fuel loads and have other plans for additional fuel treatments, Joyce said. Researchers have also done some experiments looking at the effects of prescribed burns on the forest.

"The results seem to indicate that it does alter the soil structure in terms of the heat-holding capacity of the soil," Joyce said.

Another project is looking at the consequences of chipping the material and leaving it on-site. "If we chip material for fuel treatments and leave it on site, that's a huge pulse of carbon, and it's not really clear what the long-term consequences of that are to ecosystems," Joyce said.

Unlike at other experimental forests, there have not been any challenges from local residents about planned fuel treatments in the area, Joyce said.

Tapia, who has been at the Manitou forest for 13 years, said he had anticipated complaints from residents of the 738-acre Ridgewood subdivision, which lies inside the forest, over the chipping study. "I expected an outburst, but there was no outburst," he said.

In fact, Richard Oakes, administrator of the Manitou Experimental Forest, noted that property owners in the Ridgewood subdivision have gotten together and completed a fire protection plan. "They are really scared up there, and they're trying to thin it out," Oakes said.

Joyce noted that during the Hayman fire, the county fire department had determined that it would not be able to protect any of the homes in the subdivision. "If the fire had gone across the road, it would've been pretty catastrophic for this part of the subdivision," Joyce said.

Flammulated owls

One of the forest's other main research projects is focused on the flammulated owl, the second-smallest owl in the world at just about 6 inches tall. The flammulated owl is also the most migratory owl in North America and is believed to winter as far south as Central America.

Brian Linkhart, a biology professor at Colorado College, started studying the flammulated owls on the Manitou Experimental Forest in 1981. "Before this study began, almost nothing was known about this owl species in the 100 years that it was known to occupy forests in the western United States, simply because it was viewed as a very difficult species to study and difficult to learn about," Linkhart said.

Among the difficulties facing researchers are the owl's small size and the fact that it is nocturnal, secretive, only vocalizes during certain portions of the breeding season and has a quiet call. "That quiet call -- hoo, hoo -- has been heard in the past, but usually it really takes trained ears to be able to hear it any distance at all, and quite frequently, when I take people out for the first time, they may not hear it until their ears are trained to that particular sound," Linkhart said.

The flammulated owl is primarily found in mature pine forests and feeds mainly on small moths. It is listed as a "sensitive species" by multiple regions of the Forest Service and as a "vulnerable species" by the Canadian government.

"They're cavity-nesting owls -- they nest only in abandoned woodpecker holes," Linkhart said. "We call these secondary cavity nesters. Essentially, without these cavities, they couldn't nest and they would go extinct."

Linkhart's research has found that there are about 2.5 owlets per brood, roughly 83 percent of the males return on an annual basis to their breeding grounds in the Manitou Experimental Forest, and the owls live upward of 14 years.

"This has some very important conservation implications," Linkhart said. "As you might imagine, an animal with a low reproductive rate would be least capable of its populations being able to recover quickly following some environmental perturbation."

Linkhart's study has also found that female owls are not nearly as faithful to their breeding sites as males. Males almost always return to their territories every year, but females tend to switch to territories that have more mature ponderosa pines and produce more owlets.

Having a long-term data set has been essential to uncovering such patterns, Linkhart said. "If you look at any two or three or four years of this data set that's gone on for 28 years now, these patterns don't jump out. In fact, it's probably in part because the family sizes are so small, none of these patterns emerge until you start using longer term data sets -- 10, 15 and especially over 28 years."

Linkhart has also been looking at recolonization by flammulated owls into the forests burned by the Hayman Fire and how successful these owls are in nesting the patches of forest that remain. The study targeted areas that burned at a low intensity or remain unburned.

About five to eight males have returned each year since the fire. There do not appear to be lower brood rates for the Hayman areas, but the return rate -- the rate at which banded individuals return to breeding territories -- in the Hayman area is less than half the rate that males return in the unburned forest in the experimental forest. Although there is no way of knowing for sure whether the owls that don't return to their sites perish or simply go to other breeding areas, Linkhart said the males' strong fidelity to their breeding territories suggests that many of these birds probably are not surviving.

"If this pattern is maintained, that would be suggestive of the fact that perhaps the Hayman fire, for whatever reason, is not going to provide long-term habitat for these owls, if the males cannot survive or are energetically weakened by attempting to raise families there," Linkhart said.

In light of the Hayman fire and similar fires throughout the West, there is a great deal of interest, especially in forests that have an urban interface, in thinning to reduce the risk of catastrophic fire. But not much is known about how such widespread thinning efforts might affect the vertebrate species of the forest, Linkhart said.

Linkhart believes forest thinning might be beneficial to the owls, if it is directed at the young, dense trees only. If it occurs in such a way that older, overstory trees are also removed, it could be detrimental to the owls, he said.

The Colorado College professor just started research this summer to examine this question, selecting sites in the Pike National Forest that are planned for thinning in 2010 and 2011. He plans to identify all the owl territories in the areas that are going to be thinned, track the reproduction for at least two years, and then collect post-treatment data on the reproduction and survival of the owls.

The long-term data that Linkhart has collected has also been helpful in looking at the effects of climate change on the owls. "There have been very few studies, certainly in North America, that have looked at the effect of climate change on raptors, and this potentially is an important group of birds to be able to look at because they operate at the top of food chains and food webs, and one would expect that there very well may be trickle-up effects that would affect raptors that may not necessarily be visible at lower levels in the food chain," Linkhart said.

So far, the research has shown that short-distance migrants -- for example, birds that migrate from the northern to the southern United States in the winter -- are nesting earlier each year, up to 18 days earlier over the last 20 or 30 years, to a greater extent than long-distance migrants, such as the flammulated owl, which are nesting about a week earlier. One reason for this may be that short-distance migrants may be more clued in to climatic changes to time their migration, while long-distance migrants may only use the length of days to determine their migration, Linkhart said.

Linkhart's research on the owls has shown that the onset of incubation has advanced nearly eight days from 1981 to 2006. If that pattern continues, the onset of incubation could move over a month in a century.

The earlier incubation is correlated with rising temperatures in the spring. Since the study began, the mean maximum temperature in May has risen 3.5 degrees Celsius.

Linkhart has not detected effects on the success of the owls' breeding yet, but he is concerned that there may be some threshold where the owls advance their breeding cycle to some point and then the family sizes and the number of owls fledged per nest starts to drop off. "If there is such a threshold event, that certainly would be very concerning and one which I'll be watching closely here for the next several years," Linkhart said.

"When we see the effects show up in owl populations, then it's an indicator that all is not right in the environment and is at least starting to affect the very system of which humans are a part of, as well," Linkhart said.

Gable is an independent energy and environmental writer in Woodland Park, Colo.

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