Wildflower is published quarterly by the Wildflower Center. Its content is national in scope with articles about the conservation and use of native plants as well as news from the Wildflower Center. A subscription is provided to Wildflower Center members as a benefit of membership.
Conifers Call - Winter 2011
Cone-bearing trees are winter's foundation
By Gail Folkins, Lindsay Patterson and Bibi Wein
"You can live for years next door to a big pine tree, honored to have so venerable a neighbor, even when it sheds needles all over your flowers or wakes you, dropping big cones onto your deck at still of night."
— DENISE LEVERTOV
BEHOLD THE SEASON WHEN OUR AFFECTION for pine trees and other conifers soars to new heights. Indeed, conifers are the backbone of the winter landscape and a seasonal source of joy and inspiration. Their evergreen loyalty serves our souls on the drabbest of days, and scavenging for cones – a delight in any season – is all the more fun in winter.
We asked three authors to discuss some beloved conifers across the country and threats that stand in their way.
In autumn, Eastern hemlock cones are small and pale green at first before turning red-brown in late autumn. Photo by Bob Fisher.
The Forest's Ballerina
By Bibi Wein
I CAN SEE EASTERN HEMLOCKS through every window of my Adirondack log cabin. They share this mixed northern forest with many other beautiful trees, but it's a hemlock that always draws my eye – perhaps because some part of it seems always in motion. The Eastern hemlock (Tsuga canadensis) is the ballerina of the forest. There is nothing rigid about this species but its deeply furrowed gray-brown trunk. Even the terminal shoot doesn't point skyward but bends always, away from the direction of prevailing winds. The feathery twiglets and soft needles wave in a breath of air, droop with raindrops, rise to beckon or point as they dry. Long limbs dance in a breeze, swoop and sway in a bluster, wear snowfall like a regal cloak. A heavy snow bends the lower branches to the ground, where they often remain until spring. These lower limbs shelter many animals year-round. If you're caught in the woods in a storm and need to seek shelter under a tree, a medium-sized hemlock is an excellent choice.
Among the most shade-tolerant and long-lived tree species in eastern North America, the Eastern hemlock has a lifespan that can exceed 800 years, during which it can reach a height of 150 feet, though 75 to 100 feet is more typical. The fossil record suggests its presence in ancient forests of North America as well as Europe.
In our own history, the hemlock had its greatest impact in the settling of the northeastern forest in the mid-19th century, when whole communities were carved from the wilderness to support the tanning industry. Tannins are widespread in the plant kingdom, and hemlock bark has been a historically important commercial source.
Comfortable in a variety of habitats from rocky slopes and ridges to stream banks and moist woodlands, from northeastern Canada through Georgia and west to Minnesota, the Eastern hemlock is at its grandest in the cool ravines where it is often the dominant species. Descend even a few steps into a hemlock ravine on a hot day and, whether you've come from a blistering parking lot or a pleasant forest trail, you'll be plummeted into a cool microclimate where time seems to stand still. The sun scarcely pierces the dark canopy, and mists may rise from an ice-cold stream where aquatic life flourishes in rich variety.
In some instances, Eastern hemlocks reach 150 feet and live for more than 800 years. Photo by Bob Fisher.
Delaware Water Gap National Recreation Area and the Great Smoky Mountains National Park are among the homes of such ravines. But check before you go, because Eastern hemlocks are under siege. A tiny aphid-like insect native to Japan threatens to eradicate the species through much of its range. The hemlock woolly adelgid (Adelges tsugae) arrived in the Northeast in the early 1950s, probably on Japanese ornamentals. With no natural enemies, it is spreading at an alarming rate – reliably stopped only by cold temperatures. Infestations, easily recognizable by the appearance of tiny white "cotton balls" at the base of the needles, have been found in at least 17 states. In Shenandoah National Park, up to 80 percent of the hemlocks have died. At least half a dozen studies introducing various species of predatory beetles are underway, and some show preliminary success. But if winters continue to warm, the hemlock killer's range will spread.
Apart from the incalculable aesthetic loss, the loss to wildlife will be staggering. More than 120 vertebrate species and nearly 90 species of birds – among them the black-throated green warbler, Blackburnian warbler and Acadian flycatcher – find shelter in the embrace of its pendulous branches and food in the woody rosettes of its thumbnail-sized cones. In winter, a mature hemlock in the yard is as good as a birdfeeder to attract chickadees and nuthatches.
Bibi Wein is the author of the award-winning memoir "The Way Home: A Wilderness Odyssey" (Tupelo Press). Continuing her exploration of the importance of wild places in our lives, she currently is working on a sequel. She divides her time between Manhattan and the Adirondack Mountains in upstate New York.
A savanna made up of loblolly pine and native grasses. Photo by Andy and Sally Wasowski.
Can Pine Trees Beat the Heat?
By Lindsay Patterson
THIS PAST SUMMER WAS A RECORD-BREAKER for Texas. In Austin, I woke up every morning to hot sun and no rain. I watched my garden shrivel and the leaves on trees go limp. About 40 days into our unhappy streak of over-100-degree temperatures, friends started talking about moving to cooler climates. Just when we thought we were out of it, wildfires burned 34,000 acres of the dry landscape in Bastrop County, just east of Austin. Unfortunately, this summer might be a trend toward a new normal, rather than an anomaly. Climate models predict that Texas is going to continue to get hotter and drier over the next 20 years. Many species might not be able to adapt quickly enough to survive.
But there is one native species that's so important it has a team of university scientists working to make sure it stays in Texas. That lucky tree is the loblolly pine (Pinus taeda). This pine grows throughout the southeast part of the state and has huge economic value in Texas. Today, the species covers proportionately more of Texas than it did 100 years ago. In the late 19th century, industrialists cut down huge swaths of loblolly, longleaf and shortleaf pine forests. When the forests were replanted in the 1930s, loblolly pine was favored over its native cousins because it grows fast, straight and tall within the first 15 years of its life. Now there are a $19 billion industry and thousands of jobs riding on its survival.
That's why scientists at Texas A&M University are studying how the species will be impacted by climate change – and how humans can help it adapt. "Rather than 60 days of 95-plus-degree weather, it might be 80 days of 95-plus temperatures," says Jason Vogel, Ph.D., an assistant professor of ecosystem management at Texas A&M who is working on the research project. Loblolly pines can deal with high temperatures, he explained, but a lack of moisture can either kill them or slow their growth.
Professor Jianbang Gan, Ph.D., is studying the risks and consequences of climate change for loblolly pines. He says that among the biggest challenges on the horizon for the tree are more-frequent wildfires – like the fires that spread through loblolly pine forests in Bastrop – and insect infestations. A healthy loblolly pine forest can reduce fire risk and fend off pests. But when it is already struggling, its defenses are down. "Trees are like humans," Gan says. "When you have stress, it is easier to get sick." That means scientists have to figure out which trees won't get sick.
Loblolly pine is being studied for how it can adapt to warmer temperatures and drier conditions. iStock Photo by Karl Kehm.
Tom Byram, Ph.D., is part of a team of geneticists on the project. "We are going to have to evaluate and select for disease resistance, insect resistance and drought tolerance," he says. Byram explained that the species contains a huge range of genetic variability, much of which is preserved in natural forests. His team is trying to identify molecular markers, or fragments of DNA that can be associated with the desired traits. In other words, once scientists know what high drought tolerance and insect resistance looks like inside a tree's genetic code, it will be easier to select trees better suited to a tougher climate. "Hopefully, what we'll get out of this are better-adapted, more vigorous trees," says Byram. And hopefully, the loblolly pine will continue to thrive in Texas.
Lindsay Patterson is an Austin-based science writer and gardener. She blogs about science at lindsayjpatterson.com and contributes to various publications and radio programs, including The Texas Observer, "Studio 360" hosted by Kurt Andersen and KUT News.
Douglas fir trees at Squak Mountain State Park in Washington. Photo by Janet Horton.
Comeback Kids in Second-Growth Forests
By Gail Folkins
SECOND-GROWTH FORESTS WRAP the hillsides of two regions I call home – the Pacific Northwest and the Southwest. The conifers of these diverse areas, from the Douglas fir (Pseudotsuga menziesii) of western Washington to the Ashe juniper (Juniperus ashei) of Central Texas, play a vital role in second-growth forest landscapes.
Providing ample shade for a summertime walk, Douglas fir and western red cedar (Thuja plicata) layer the mountaintop on Squak Mountain in Washington State. These conifers, with the exception of a few old-growth stumps, comprise new growth following the logging and coal mining that took place in this region around the turn of the century. Although this particular second-generation forest is preserved, Douglas fir of the region is prized for lumber. At the same time, forests both old and emerging offer vital habitat for plants and wildlife.
The Oregon Forest Resources Institute defines old-growth forest by characteristics – for instance, forest canopy and fallen logs – rather than by physical age alone. Second-growth forests regenerate following a disturbance in the older growth, whether man-made causes such as logging or natural events such as wildfires. These forests often lack the complexity in canopy and ground cover to offer the plant and wildlife habitat of a mature, old-growth forest. Given time and forest management, however, conifers adopt old-growth properties of appropriate spacing, varied height and ground decay, spurring native plant life.
During a recent visit to Squak Mountain, part of the way up we spot a coyote at the edge of the trees. A Western hemlock (Tsuga heterophylla) downed in a windstorm a few years ago is crumbled into mulch from ample rains. I sample huckleberries (Vaccinium spp.) from a tree stump, along with the salmonberry (Rubus spectabilis) growing alongside the road in tart orange clumps, fruits of this evolving forest already evident.
About 2,000 miles to the southwest, during a walk through a Central Texas forest, a tangerine sunset colors the horizon. Our guide at Wild Basin Wilderness Preserve, west of downtown Austin, points to a second-generation grove of Ashe juniper trees. The area's shrubby juniper, called cedar in Texas, is home to the black-capped vireo, an endangered bird species. The goldencheeked warbler, also endangered and nesting only in Texas, favors older, taller stands of juniper, a conifer often misunderstood to be non-native.
LEFT Needles of Western red cedar, in the same park. Photo by Janet Horton. RIGHT Ashe juniper at Wild Basin Wilderness Preserve in Austin. Photos by Steven Schwatzman.
The clearing of the area's original forest landscape for lumber and firewood, which included taller stands of red oak (Quercus buckleyi) and juniper, helped create this misperception, explains Monica Swartz, Wild Basin director. "Because our grandparents' memory of the forest was no trees, some people think they have to remove all junipers."
Left to their own devices or through selective thinning, these second-growth conifers eventually become larger trees, creating healthier soil for native plant species such as cedar sage (Salvia roemeriana). The regeneration process to create original forest characteristics of shade and ground-layer decay can take hundreds of years, although management can hasten the process; Wild Basin plans for the fall include thinning brush and restoring degraded soil to help improve habitat for endangered songbirds.
Gail Folkins often writes about her roots in the American West. Her essay "A Palouse Horse" was included in "The Best American Essays 2010." She also has written a book titled "Texas Dance Halls: A Two-Step Circuit."