Found 813 Resources containing: Seasonal Changes
Flowering and fruiting phenologies of seasonal and aseasonal neotropical forests: the role of annual changes in irradiance
Yes, this is a metaphor—the sun doesn't experience a terrible snowy winter and then mere weeks later descend into a humid, sticky mess. But the sun does have weather, in the form of fluctuating magnetic fields. And, it turns out, there's seasonal variability in that weather, scientists at the National Center for Atmospheric Research announced this week.
Our star has an 11-year cycle, in which the hot soup of particles flowing within vary the magnetic field on the star's surface. That variability shows up in sunspots—regions that are thousands of degrees cooler and 1,500 to 30,000 miles wide—and can shoot streams of charged particles at us at millions of miles per hour. These solar storms cause auroras, and sometimes even blackouts. At the peak of the cycle, sunspots are common.
But solar flares and other ejection of gas and force often peak just after the sun the reaches its peak sun-spotty-ness. And, researchers say, a pattern of two-year variability might explain that lag.
The pattern, they think, is caused by changes in magnetic field bands in the star's northern and southern hemispheres. It's as though the sun has a dry season and a wet season, lead author Scott McIntosh explains in a statement. Except instead of rain, the sun has bursts of gas and particles, with energies totaling that of hundreds of millions of tons of TNT.
Gardens evoke deep memories. Many of us spent our formative years learning about flowers and vegetables at the knees of our grandparents. We may not remember all the plant names, but we remember how being out in the garden made us feel—the warmth of the sun, the coolness of the soil, the crunch of the mulch and the smell of the lilacs. Does that garden you experienced as a child still exist? Most likely, it does not. Or, if it does, it has changed substantially from the one you first knew.
“Gardens are ephemeral,” says Kate Fox, an education specialist with Smithsonian Gardens. “These places, even more so than buildings, are lost to time. Dating back to Thomas Jefferson, we are a country of gardeners and there is a lot to be learned about our history through gardens and our gardening stories.”
To capture those stories in essays, photos and videos, a new digital archive, Community of Gardens is open and ready for business. Inviting every one from master gardeners, landscapers, historians and weekend enthusiasts to browse the records of gardens on a map of the United States or to submit a personalized accounting about a community garden, a school garden, a memory of a past garden, or to detail the delights of a favorite heirloom plant.
“We are looking especially for the garden stories of everyday people, not just the big estates,” Fox explains. “We also want to find out how Americans feel about gardening right now and what role it plays in their lives.”
Image by Chewonki Foundation. A gathering takes refuge under a shady tree for some lemonade in a garden at the Chewonki Foundation in Wiscasset, Maine, in the 1950s. (original image)
Image by Jones Valley Teaching Farm. In Birmingham, Alabama, a group of students shell beans at the Jones Valley Teaching Farm. (original image)
Image by Paul Leverone. Fourth generation gardener Harry Leverone, age 8, proudly displays his head of broccoli that he harvested in Nellysford, Virginia. (original image)
Image by Paul Leverone. In his vegetable patch in Colonial Beach, Virginia, Harry Leverone, Sr, c. 1960 harvests his prized tomatoes. (original image)
Image by Susan Bell. A gardener's basket filled with the day's harvest (original image)
Image by Bridget Besaw. Late summer blooms in the Margaret Ellis Garden in Wiscasset, Maine. (original image)
Image by Archives of American Gardens, Garden Club of America Collection. A community garden project that began in the 1980s in the Norris Square neighborhood of Philadelphia is called Las Parcelas, or the parcels, meaning a collection of garden spaces, that also serves as a cultural heritage center, honoring the community's Puerto Rican residents. (original image)
“The historic material in our archives tends to be more of the higher socio-economic representation of gardens,” says Cindy Brown, also with Smithsonian Gardens. “The American story of gardens needs to tell the full story. We have all kinds of gardens in our country and we needed to think of a way to get the stories submitted so we decided to reach out online and through local schools.”
Over the next year, Brown and Fox will also be rolling out a project-based learning curriculum and toolkit to support teachers interested in getting their students out into their communities to collect stories about gardens “There are two parts,” says Fox of the project. “First, there is the preservation of stories that would otherwise be lost to time. The other side of it is that storytelling is a way to connect communities, and these conversations tend to encourage people to see the place where they live in a new way.”
Brown explains that the Smithsonian Gardens staff has been working hard to develop an education piece that teaches students how to do oral histories and interview people. “We also want students and families to be engaged in understanding how gardens really keep a community healthy,” she says. “Hopefully, this will open up the students’ eyes to new careers in horticulture as well.”
One Virginia gentleman has used the project to explore his ancestry. He was able to trace his garden story back to 19th-century Italian immigrant ancestors. “It started am amazing conversation within his family and he learned many new things,” said Fox.
“This is the first step in reaching a broader audience and engaging directly with them,” said Fox. “We are excited to see what kind of stories we’ll get.”
Here’s the call to action. Gardeners, put down your trowel and log in. Are there fading memories that percolated as you read this? Maybe there was a family member or friend that can help fill in some of those garden details that may otherwise be lost to time? When you are ready to share your story, please go online to Community of Gardens. I cannot wait to read them!
The predictability and scale of seasonal changes in a habitat help determine the distance migratory species move and whether the animals always travel together to the same place or independently to different locations.
The post Changes in vegetation determine how animals migrate, scientists find in new National Zoo study appeared first on Smithsonian Insider.
If you have seasonal allergies, you may have already suspected that allergy season is coming earlier, lasting longer and growing more severe in the last two decades. Now, there’s science to back up that hunch.
The upswing in allergens is a global phenomenon, reports Umair Irfan at Vox, with pollen counts increasing across the Northern Hemisphere in the last 20 years—an uptick likely fueled by climate change. And that’s a big deal; between 10 and 30 percent of the global population, including 50 million Americans, suffer from seasonal allergies.
In a new study published in the journal The Lancet Planetary Health, researchers analyzed pollen counts in 17 locations worldwide stretching back an average of 20 years. Of those locations, 12 saw significant increases in the pollen load over time. The international team hypothesizes that the upswing in pollen is related to changes in maximum and minimum temperatures caused by climate change.
The intensification of allergy season is one of the earliest and most visible public health impacts of climate change, Irfan reports. “It’s very strong. In fact, I think there’s irrefutable data,” Jeffrey Demain, director of the Allergy, Asthma, and Immunology Center of Alaska, not involved in the study, tells Vox’s Irfan. In Alaska, which is warming twice as fast as other parts of the globe, pollen is up as well as stings by insects.This figure shows how the length of ragweed pollen season changed at 11 locations in the central United States and Canada between 1995 and 2015. Red circles represent a longer pollen season; the blue circle represents a shorter season. Larger circles indicate larger changes. ( Ziska et al. / EPA Public Domain)
“It’s become the model of health impacts of climate change,” Demain says.
So why are pollen counts going off the charts? According to the Union of Concerned Scientists, there are three main reasons. First, rising CO2 levels truly do have a greenhouse effect, increasing the growth rate of many plants which leads to more pollen. Rising temperatures extend the growing season of pollen-producing plants. And longer spring seasons lengthen the pollen production of certain plants and allows more fungal spores to make it into the air.
Temperatures are expected to rise by 3-to-4 degrees Fahrenheit and carbon dioxide concentrations could reach 450 parts per million by 2050. Lewis Ziska, lead author of the study and a weed ecologist at the United States Department of Agriculture, under those conditions, some pollen producers will thrive. He predicts, for example, that ragweed, which is usually about five to six feet tall, could shoot up to ten, or even 20, feet tall in some cities, producing much larger amounts of pollen—a true nightmare for hay fever sufferers. In fact, Ziska tells Irfan that since pre-industrial times, the pollen productivity of ragweed has already doubled. And according to data from the Environmental Protection Agency, ragweed hangs around between 11 to 25 days longer than it did in 1995.
“The influence of climate change on plant behavior exacerbates or adds an additional factor to the number of people suffering from allergy and asthma,” Ziska tells the Union of Concerned Scientists.
Ragweed is not the only species of concern. Tree pollen, grass pollen and molds are all major allergy triggers, all of which are expected to double by 2040. This year is already off to a pretty apocalyptic start with images of dense pollen clouds over North Carolina making the rounds and Chicago bracing for a bad allergy season.
Korin Miller at Prevention says installing a new air filter, keeping houses clean, avoiding yard work on high-pollen days and taking over-the-counter allergy medication can keep people from experiencing allergy attacks. But for many sufferers the best strategy is getting immunotherapy shots, which eventually desensitize the immune system to allergens. And for needle-phobes, there’s good news. NPR reports that many allergists are prescribing immunotherapy tablets for people suffering from grass pollen, dust mite or ragweed allergies.
Sunday, June 21, marked the summer solstice for the northern hemisphere, colloquially known as the first day of summer. Many sun-worshipers will revel in the longer daylight hours and warmer temperatures. But even after 50 years of Eddie Cochran's “Summertime Blues”—and a few of Lana Del Rey's “Summertime Sadness”—some people may be surprised to learn that summer can cause seasonal depression.
While seasonal affective disorder (SAD) is common during the short, cold days of winter, perhaps one in ten SAD sufferers experiences his or her depression during the summer months.
“Both summer SAD and winter SAD people can experience the full range of symptoms of major depressive disorder—depressed mood, hopelessness and feelings of worthlessness and nihilism,” says Ian Cook, a professor of psychiatry and bioengineering and director of the UCLA Depression Research & Clinic Program.
Other symptoms are opposites, like the seasons themselves. Winter sufferers often feel sluggish, sleep more than usual and tend to overeat and gain weight. By contrast, summertime depression often brings insomnia, loss of appetite, weight loss and feelings of agitation or anxiety. Summertime SAD can also create an increased feeling of isolation. If misery loves company, SAD sufferers can find plenty of other people to commiserate with during the dreary winter months. But during summer, most everyone else seems to be having a great time.
It remains a puzzle why some people experience SAD during the months of fun in the sun. Some research suggests that it can be triggered by too much sun exposure or oppressive heat. Other scientists have theorized that allergies play a roll, or that people are responding to shifts in sleeping habits during summer's lighter nights and bright early mornings.
Unfortunately for those with the summertime blues, winter SAD and other dangers of winter darkness have received the lion's share of research attention. “Treatments for summer SAD do not have as much evidence as there is for winter SAD,” Cook says. One common winter therapy, use of light exposure to help compensate for dark days, isn't likely to help those who become depressed during the long, bright days of summer. "Most clinicians take it case-by-case and empirically develop a treatment plan for each individual with summer SAD,” Cook adds.
So why does anyone suffer from SAD at all? A recent brain study suggests that the season in which someone is born may have a lasting impact on whether they are affected by the disorder. Researchers at Vanderbilt University pinpointed the mid-brain region that may be a source of SAD—the dorsal raphe nucleus, where many of the neurons that control serotonin levels are located. Serotonin is a neurotransmitter that helps to regulate mood; high levels have been linked to feelings of well being, while lower levels are associated with depression.
The team then raised groups of mice during different “seasons”, as defined by light cycles in the lab. Summer mice received 16 hours of light and 8 hours of dark each day. Mice representing spring and fall births experienced 12 hours of light and dark each. A third group, the winter mice, endured 16 hours of dark and only 8 hours of light each day. The groups' environments were identical in all other respects.
When the team recorded electrical activity in the animals' brains, they found that mice raised in summerlike conditions showed activity spikes consistent with serotonin secretion and elevated brain serotonin levels compared to their fall and winter counterparts—essentially, summer mice were happiest.
“The basic idea is that the enhanced activity of these neurons is a kind of antidepressant activity,” says Douglas McMahon, Vanderbilt’s Stevenson Chair in Biological Sciences, whose team reported their findings in May in Current Biology.
Brain changes due to seasonality were also reflected in mouse behaviors, the team found. Mice with brain chemistry consistent with that of a depressed human have been found to behave in certain ways. The forced swim test, for instance, is often employed to try out the effectiveness of antidepressant drugs. Scientists put mice into a pool of water and measure how much time they spend trying to escape versus just floating passively. Mice can float safely without much effort, but depressed mice, the theory holds, will more quickly lose hope of escape and simply float in despair. The Vanderbilt team ran this test with their mice, and the winter-born brood was quicker to float.
Similarly, an open field test determines how willing a mouse is to go out into the open. “You can imagine as a prey animal they are very cautious about that,” McMahon says. “But the mice born in summer were a bit bolder and less anxious, so they spent less time in closed areas or up against the wall,” he explains.
These birth season impacts lasted into adulthood for the mice, suggesting that the imprint of seasonal light on developing brains can stay with us even as we move around to different environments.
“We were able to show that their experience early on, even in what would be the equivalent of third trimester development in humans, sort of set the properties of the serotonin neurons, so that even six months later, and that's persisting into young adulthood for mice, they were still the same when we measured, even when we had moved them to live in a different seasonal photoperiod,” McMahon says.
He notes that researchers will still need to build evidence for this effect in humans. “In people, such an effect would have to persist for decades, and we don't know if it does,” he says. But other studies have also suggested that the season of our birth may make us more or less likely to suffer from various ailments—including depression. For example, earlier this month a Columbia University study compared 1,688 diseases with the birth dates of 1.7 million patients who had been treated at New York-Presbyterian Hospital/CUMC between 1985 and 2013. Among other ailments, several depression-related diagnoses were modulated by birth season, according to the study, with winter babies being more prone to suffer their effects.
“There could be lots of other seasonal variables other than light,” McMahon cautions. “But it's intriguing that at least in mice, our data shows a direct and lasting impact of the photoperiod on the neurons in the brain that are involved in producing serotonin and having an antidepressant role.”
Rudolph and his Arctic reindeer kin have evolved a neat trick to help them contend with dark, sunless winters and bright summers: their eyes change color. In the winter, their irises take on a frosty blue, while in the summer they adopt a golden hue. These colors each promote a different type of visual advantage, either allowing them to see through the darkness or to keep from squinting in the sunny glare.
The bit that actually changes colour is the tapetum lucidum or “cat’s eye”—a mirrored layer that sits behind the retina. It helps animals to see in dim conditions by reflecting any light that passes through the retina back onto it, allowing its light-detecting cells a second chance to intercept the stray photons. The tapetum is the reason why mammal eyes often glow yellow if you photograph them at night—you’re seeing the camera’s flash reflecting back at you.
Reindeer eyes, by default, are gold. But during the long winter, their pupils dilate for months on end, Yong explains. All of this effort takes a toll on the reindeers’ eyes, which begin to swell and in turn exert pressure on tapetum.
This layer is mostly made up a collagen, a protein whose long fibres are arranged in orderly rows. As the pressure inside the eye builds up, the fluid between the collagen fibres gets squeezed out, and they become more tightly packed. The spacing of these fibres affects the type of light they reflect. With the usual gaps between them, they reflect yellow wavelengths. When squeezed together, they reflect… blue wavelengths.
The wintery blue, Yong writes, is about 1,000 times more sensitive to light than the summery gold. The latter color, on the other hand, helps in the summer by bouncing the majority of light off of the animals’ eyes, effectively acting like a pair of natural sunglasses. So when the Christmas decorations are broken out this year, take a moment to check and see if Rudolph is anatomically correct—he should be sporting a pair of baby blues that time of year.
More from Smithsonian.com:
Darker days have arrived across the Northern Hemisphere and, for many people, so has seasonal depression. For years patients have turned to light therapy, regular exposure to artificial light that's meant to mimic the longer days of milder seasons.
But now a multi-year study suggests that specialized talk therapy sessions may actually have longer-lasting benefits than light exposure for treating seasonal affective disorder, or SAD.
Cognitive-behavioral therapy (CBT) is a type of talk therapy that's been used to fight other types of depression for decades. Sessions involve working with a professional therapist to learn methods of thinking, speaking and acting that eliminate negative thoughts and replace isolating behaviors with more positive activities to banish the blues.
Quite a bit of scientific literature indicates that over the long run, psychotherapies and particularly CBT can produce a better outcome than other treatments for depression. But CBT has only recently been applied to SAD, so its benefits in this realm were unclear.
The National Institute of Mental Health funded a large-scale study to explore CBT and light therapy effectiveness over time. One hundred seventy-seven SAD patients were randomly assigned treatment with either six weeks of light therapy or six weeks of CBT therapy.
In the CBT sessions, therapists introduced cognitive skills to identify and challenge negative thoughts associated with SAD, like the expectation that the upcoming winter means loneliness and gloom. Behavioral skills then helped patients find fun activities, schedule them and actually do them to counteract the seasonal “hibernation” that can fuel depression.
Led by Kelly Rohan of the University of Vermont, the study at first found that improvement was comparable during an initial six-week treatment period, whether patients used a light box for half an hour upon waking each day or attended a 90-minute group CBT session twice a week.
The following September, participants were encouraged to either resume light therapy or use the skills they learned in CBT on their own. The team conducted in-person follow-ups during that winter and, again, no difference was apparent in the effectiveness of the two treatments.
But during another follow-up two winters later, nearly half of the light therapy subjects reported recurring depression, while only 27 percent of the CBT group did. The light therapy group also suffered worse depressive symptoms than those who'd used CBT.
It turns out that only 30 percent of the study participants were still using light therapy by the second winter follow-up, the team reports in the American Journal of Psychiatry. The study authors think the difference might be due to the burden of upkeep—over enough time, patients have to work harder to maintain their light therapy schedules than they do keeping up with their CBT skills.
Psychological and behavioral factors produce long-term benefits in all kinds of other medical conditions as well, notes Michael Young of Illinois Institute of Technology, who is also past president of the Society for Light Treatment and Biological Rhythms.
“So in that sense, this study is not so strange in the context of depression treatment studies in general,” he says. “If you think about heart disease, everybody knows you need to take your medicine, eat better and get some exercise. But what makes most of the difference in outcomes is not getting that prescription. It's helping people do the right things. And that has to do with how they think about it and the behavioral strategies they use."
According to Young, both treatment options likely address the biological basis for SAD, just in different ways. Drops in sunlight can alter the brain's balance of serotonin and melatonin, chemicals that help govern sleep patterns and mood. Replacing some of that lost light with special lamps can fool the brain into restoring normal rhythms.
While CBT is unlikely to have this exact type of impact on the brain, changing people's behavior can affect their physical systems, too.
“Even our genes don't operate in a vacuum. There's often an interaction of genes and behavior or environment," Young says. "So the idea that getting people up and doing more things, and increasing positive experiences that you tend to avoid when depressed by staying in and feeling helpless and hopeless, those things have effects on biology as well as psychology.”
Treating any kind of depression, though, is about figuring out what works best for each patient, he says. Some people may benefit more from CBT or from light therapy, and others may prefer a mix of these and other treatments.
“They can all produce the same kinds of beneficial outcomes,” he notes. “And that's what we really care about with our patients.”
Mark Cohen, guitar and vocals.
Recorded in March, 1979.