COLLEGE STATION — Enjoying a forest’s fall colors may seem like a simple pleasure, but knowing why they are so pleasurable and how to keep them that way is another matter.
Yet, it’s a matter of no little importance in the United States, where forest managers must balance the needs of recreational users with timber producers and consumers, says Dr. James Gramann of the Texas Agricultural Experiment Station.
Gramann, a station researcher and Texas A&M University professor of recreation, park and tourism sciences, and Wiijoo Yhang, a South Korean doctoral candidate, recently completed a pioneering study in color as it relates to forest management. One result of their work has been Yhang’s doctoral dissertation, which examined the effects of color on perceptions of scenic beauty in the Ouachita National Forest in Arkansas.
“The U.S. Forest Service has been under tremendous pressure in Arkansas to reduce clear cutting and grow a type of forest with more mixed hardwoods and pine — the type of forest that has more color,” said Gramann. “There have been plenty of studies on scenic beauty, but this is the first time that someone has looked at color.”
“With this kind of research, you can recommend what needs to be done on the ground to maximize color. In that sense, it’s a very applied effort.”
Gramann said the study ended up being good news for the Ouachita National Forest, because its findings supported the forest’s main management goal: learning how to grow and perpetuate a mixed pine-hardwood forest while also maintaining commercial supplies of timber. Pure pine forests are more desirable from a timber production standpoint.
One implication of the study is that in outdoor recreation sites and other visually sensitive areas, such as highway corridors, it could be beneficial to manage forests to have more mixed pine and hardwoods.
Gramann had conducted studies in the past dealing with the number of oaks and other East Texas hardwoods as they related to scenic beauty. For this study, he and Yhang focused on color, important because of its potential economic impact on tourism in the Ouachita mountains, where many visitors come to view foliage in the spring and fall.
“This gives us a chance to look, over a fairly long period of time, at how forests regenerate and how they impact scenery in a controlled situation,” Gramann said.
The researchers took color slides of 20 experimental plots in different landforms (including varying slopes and positioning on ridges) and different seasons. The plots also differed in the proportion of hardwoods they retained after harvesting for timber.
Harvesting left each plot with 60 square feet of pine, with pine measured at the base of each tree. One of four different proportions of hardwood were in each plot: 30 square feet per acre, 15 square feet per acre in a grouped arrangement, 15 square feet per acre in a scattered arrangment, or no hardwoods.
Students in four Texas A&M classes rated a total of 340 slides on a 10-point scale, with raw ratings transformed into what were called scenic beauty estimations. Three trained judges separately rated each slide for the visibility of green, yellow, blue and brown, and these ratings were transformed into “color visibility estimations.”
An equation relating the two found that greater green visibility was associated with higher beauty evaluations, while more brown was associated with lower beauty evaluations. Yellow enhanced beauty ratings, while blue detracted from the ratings.
“The impacts of green and brown on scenic beauty were consistent with biophilia and biophobia hypotheses,” Gramann said. “These predict that, because of evolutionary processes, humans will be attracted to natural landscapes containing mostly green vegetation because these promise food, water and other basic survival needs.
“However, they will be repelled from scenes containing mostly brown vegetation because such scenes do not signify fulfillment of basic needs.”
The degree of harvesting did not affect green or brown visibility, but plots with more hardwoods did increase yellow visibility — and thus beauty ratings — in the fall. Plots with fewer hardwoods also tended to have more blue visible because of less screening of the sky by forest canopy, and those plots tended to have lower ratings.
The findings regarding yellow and blue were inconsistent with the researchers’ initial hypotheses. They had expected yellow to decrease beauty ratings and blue to increase them, based on the biophilia/biophobia hypotheses and other studies of color preference.
However, Gramann said, predictions regarding the effects of blue and yellow were based on laboratory studies, which apparently do not apply to human response to color in natural environments. He added that scenic beauty ratings were likely far more impacted by hardwood removal and greater amounts of downed woody material in the slides with greater blue. More yellow slides were associated with fall and changing colors of leaves, which are considered a strong attraction for people in many regions, Gramann said.
The study also leaves other intriguing questions, Gramann said. For instance, forest type may also be an important factor in perceived scenic beauty.
“Models developed in ponderosa pine forests in northern Arizona have been found to be less effective at predicting beauty ratings for a similar forest in Colorado,” Gramann said. “It could be that our study’s model has geographic and ecological limits.”
More studies like the Ouachita effort, using other areas and perhaps focusing on a broader range of colors, could provide useful data to researchers, he said.