Flowers Grow in Openings in Ponderosa Pine Forests: Bees Like Flowers; Thinning Good for Biodiversity

This is an interesting and pretty comprehensive story from the Colorado Sun. Kind of a bee-centric take on desirable vegetation structures. Ecology is a funny thing in that there are all kinds of ecologists interested in all kinds of critters who may not prefer the same kinds of vegetation. So what is the “ecological work” that needs to be done- and what variety of ecologist decides?

The more-than-decadelong effort to thin Front Range forests to reduce fire danger has brought more bees, more flowers and increased resilience to climate change, new research shows.

The raw number and the diversity of bees and plants exploded a few years after ponderosa pine forests were restored to a “pre-European” state, researchers from Colorado State and Utah State universities found.

“We found that if you cut trees and open up the canopy, between three and 10 years later, you see a pretty good response,” said Seth Davis, associate professor of forest and rangeland stewardship at Colorado State University and co-author of a study recently published in “Ecological Applications.”

“Forest restoration and forest thinning is one of the ways that we can conserve our native communities.”

I like that reporter William Allstetter provided the historical context for how these particular forests came to be.

For thousands of years, natural fires have been an integral part of healthy forest ecosystems in the West. Small fires that clear out underbrush every five to 30 years as well as more devastating fires that can raze the forest to the ground every 50 to 100 or more years clear the way for new growth. Native Americans were known to set small fires to clear out undergrowth for better hunting and regeneration of valuable plants, but did not cause major changes in the ecosystem. Then, beginning in 1859, Euro-Americans flooded into Colorado seeking gold and silver.

I’m not sure that’s accurate; not sure that we can know whether larger pre-European fires were set intentionally. Larger fires did occur.

“Suddenly, in a span of decades, the Colorado Rockies were engulfed by this new, highly unpredictable world of commodity capitalism, of smelters and railroad investment, of boomtowns and sudden busts, of landscape changes so fundamental that they dwarfed the modest human impacts made over the prior 10 centuries,” historical geographer William Wyckoff wrote in his book “Creating Colorado.”

Vast swaths of the Front Range forests were cleared to obtain wood for mining, construction and railroads. Extensive fires also surged across the landscape, fueled by accidental and intentional fires.

To combat the rampant and unregulated logging of these forests, the federal government in the early years of the 20th century created the White River, Pike, and Arapaho and Roosevelt national forests along the Front Range and high into the Rockies. At about the same time, firefighters began trying to suppress all fires.

As a result, over the past century, dense forests with thick undergrowth have grown up across the Front Range and the entire West. Many of the plants that thrived in the pre-European forests disappeared from the now shady forest floor. And with them went many of the animals that ate and pollinated them. You end up with a rather homogeneous landscape that doesn’t have a lot of flowers in it,” Davis said. “You end up with a situation where you can’t have a lot of native bees there.”

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They found an impressively richer, more dense and resilient web of life. While the bee population roughly doubled, the number of interactions between bees and plants rose eightfold and there were five times as many unique connections between specific bee species and plant species.

The researchers illustrated the interactions in a diagram, which visually depicts a richer, more complex web of life.

“Yeah, it’s kind of mind-blowing,” Davis said. “You just see there’s just far more diversity or more complexity.

“You get the idea that if you lost one or two of the flowers or one or two of the bees out of this system, the whole network doesn’t just collapse and fall apart. Whereas on these control plots, if you remove one or two things, you just got a lot more vulnerable ecosystem.”

“This paper is a strong piece of evidence for the ecosystem benefits of forest thinning in areas where fire has been suppressed and the canopy is overgrown,” said Amy Yarger, director of horticulture at the Butterfly Pavilion. She was not involved in the research. “With climate change and biodiversity loss posing existential threats, mindful forest management is key for conservation and for preserving our way of life in Colorado.”

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“Here are some really key species for supporting a lot of biodiversity of pollinators, which in turn supports biodiversity of plants,” said Julian Resasco, assistant professor of ecology and evolutionary biology at the University of Colorado. “Things that maintain the integrity and the diversity of these ecosystems make them more robust to other threats, like climate change.”

The researchers recommended that forest managers seed ponderosa pine forests with these plants to promote a robust pollinator network. They also could be good plants for people to plant in their gardens. “These are good choices for planting because they’re going to support the bee-flower interaction network,” Davis said.

He believes the environmental benefits extend beyond bees and plants. “We’re sort of measuring one little component of the overall food web here,” Davis said. “By bolstering their abundances, you’re also bolstering the abundances of things which prey upon them, like predators, which could be birds and other animals.” Another study from 2020 suggests that the thinned forests also benefited bird populations.

Not every scientific paper reminds me of an old pop song.. birds, bees, flowers, trees, this paper has it all.