Author Archives: rgarwin

Searching for Squirrels, Finding the Night

Written by Rachel Garwin

A week ago, I joined my friend Teage (a Field Naturalist alum) and a group of his UVM students on an “owl prowl,” Teage’s own euphonic term for a night hike.  We gathered at the edge of Centennial Woods, where gauzy tufts of white pines and bare hardwood twigs strained the clear moonlight.  A wall of darkness met our eye-level gaze, while the raspy sounds of drying beech leaves in the understory added to a sense of disquiet.  The primary goal for the evening was to listen for flying squirrels and call them in.  Before we entered the darkness, however, we observed a requisite pre-night-hike ritual.

Since leaving a well-lit environment too soon for the darkened woods might lead to undesirable confrontations with tree trunks and branches, Teage informed us about night vision while our eyes adjusted.  Human eyes require 20-30 minutes to become accustomed to low light conditions.  Coincidentally, it finally gets dark about 30 minutes after the sun first sets.  The students oohed appreciatively at the revealed secret of the universe.

I considered Teage’s implication, reflecting on whether twilight length was consistent enough to provide a uniform selective pressure.  The period between sunset and full dark (termed “Civil Twilight”) varies with latitude and season, as it reflects the time the sun takes to drop 6° below the horizon.  On the same night, civil twilight in Burlington, VT, lasted 9 minutes longer than in Bogota, Colombia, a city near the equator.  Atmospheric conditions and local weather can also affect our perception of available light from the setting sun, which increases variability.  Pole-to-pole variation aside, the length of civil twilight appears consistent enough at low and middle latitudes to suggest the plausibility of the relationship (though it does not prove it).  What mechanisms would select for correctly timed physiological processes?  Perhaps some hairy, fanged predator was involved?

Suddenly, I heard Teage ask, “Rachel, do you have anything to add before we head into the woods?”

Bits and pieces of the night hikes I used to lead rushed to mind.  Out of the torrent, what would be most relevant to this group of students?  Our pupils dilate to accept more light, just like a camera aperture changes size.  Our eyes comprise not only lenses (e.g., the cornea) that focus light, but also a receptor structure (the retina), which translates received light into neural signals our brains can understand.  The retina, in turn, is made of two types of cells: rods and cones.  Rods are far more abundant (about 17 for every cone cell); however, the cones are concentrated in the center of the retina.  Responsible for receiving color and fine resolution, cone cells are better suited for working in high-light environments.  Rod cells cannot understand color, but they register exceptionally more light than cone cells.  The operational ranges of the two cells overlap to some degree; in true twilight, both cells help parse the dim picture before us.

Instead of a long-winded physiology lesson, I settled on a practical and safety-oriented piece of advice.  “If you’re having trouble finding the trail in the dark, try using your peripheral vision.  Your rod cells—the receptor cells that are really good at picking up light—are arranged on the periphery of your retina, so that part of your eye sees better in low light conditions.”  With that, we were off.

As the trail contoured the side of a hill, I followed it with my feet as much as with my eyes.  Hard packed dirt spotted with only a few fallen leaves firmly resisted my feet, whereas my wandering steps sunk into noisy leaf litter.  After a few quiet minutes, we angled from the trail and picked our way down the gentle slope.  Looking out of the bottom of my eyes—as if I wore tiny slivers of half-moon spectacles—proved the best technique for avoiding the tangle of hardy ferns and woody shrubs.  Teage motioned for us to stop; this would be our first attempt to call the flying squirrels.

I listened intently.  Wind gusted through the upper boughs of white pines and red maples.  Still-hanging, papery beech leaves rubbed together, sending bursts of unwarranted excitement running through my mind.  Sirens howled close-by.  One of Teage’s students fired up the iPod, and high-pitched “chip chip chip” alarm calls radiated into the night to serve as bait.  I cupped my hands around my ears to exclude the droning car engines circling the outskirts of the woods.  Still nothing.  Perhaps the squirrels’ huge eyes, dominated by rod cells, picked us out as we muddled through their habitat.

I relaxed my eyes and marveled at the increased input from my peripheral vision.  Intermediate wood ferns stood distinct from the ground; before, they had dissolved into the dimness.  It seemed we had been away from bright light long enough for rhodopsin, a photopigment in the rod cells, to build up.  Rhodopsin and other photopigments in the cone cells help increase light sensitivity within the receptor cells, though at different rates and degrees. Cone cells, which never develop the light sensitivity attained by rod cells, take only 5-7 minutes.  Rod cells, however, may need over 30-45 minutes to achieve full light sensitivity.  In the presence of too much light, these photosensitive compounds break down; enough time in dark conditions is thus needed for photopigments to build up to a functional level.

The flying squirrels proved reticent, so we walked through the underbrush back to the trail.  The undergrads hesitated less between steps, and they seemed to run into fewer obstacles.  After walking a circuit across Centennial Brook and back along the lower slope on the other side, we paused to make their eyes’ night adaption more explicit.  Crouched beneath a closed hemlock canopy, we covered our left eyes and stared at the flame of Teage’s lighter with our right ones.  I smiled, startled by the pervasiveness of the “Pirate Patch” myth.  As lore would have it, pirates did not wear eye patches to cover gaping eye sockets.  Instead, they kept one eye in darkness to allow them to see below and above deck without needing time for rhodopsin to develop.  While no historical evidence supports this story, the folks at MythBusters put their weight behind its plausibility and likely had a role in its propagation.

Teage flicked off the lighter, and we switched our “eye patch” to the light-blinded eye.  Most students commented they could see more precisely with their night-adapted eye than with the light-blinded one.  Removing my hand, I winked back and forth at the hemlock boughs above.  Sure enough, my left eye discerned individual twigs against the dark sky; my right eye saw only fuzzy dimness.  While not proof that Blackbeard covered one eye so he could rush up to a darkened deck from a lamp-lit cabin, our experience supported the possibility.

We emerged from beneath the dense hemlock canopy onto a grassy hillside, where moon-cast shadows danced at our sides.  No longer relying on peripheral vision, the students carelessly walked down the trail towards home.  I smiled.  An hour ago, they had hung together timidly in similar light levels, still uncomfortable with moderate darkness.  Now they practically ran.  While the flying squirrels had remained elusive, the students found something more powerful: the ability to stride confidently through the night.

Will You Need a Warmer Hat This Winter?

by Carly Brown

A few weeks ago I tied my laces, donned my hat, and set off for a long run down Spear Street, from Burlington to Charlotte and back again. Partway through my run I saw it crossing the road without any signs of hurry, proudly displaying its black and rusty fur: the woolly bear (Pyrrharctia isabella). I immediately looked up to check for oncoming traffic, then dodged out into the road, lunged, and swiped the fuzzy caterpillar. Without breaking stride I carefully set it on the roadside it was moseying to. Some feet down the road I repeated my behavior. My mind clicked back to middle school when I learned that a long rusty stripe means a mild winter. Is that true? And what are woolly bears when they are not cute, furry, caterpillars? Never mind what passing cars must think about my woolly bear lunge.

Wolly bear (Pyrrharctia isabella) caterpillar

Wolly bear caterpillar (courtesy IronChris, http://en.wikipedia.org/wiki/File:IC_Pyrrharctia_isabella_caterpillar.JPG)

The woolly bears that we see in the fall will overwinter as caterpillars under plant debris in the cold snow environment. In order to survive the winter chill, the caterpillars produce a substance, called a cryoprotectant, which acts much like antifreeze. When spring begins to show its face, the caterpillars emerge from the leaf litter, begin to eat new plant growth, and then form a pupa to eventually emerge as the Isabella tiger. This moth is a relatively nondescript yellow-brown moth with several darker spots on its wings. Woolly bears have two generations per year. This means that the newly emerged moth lays its eggs, which hatch to complete the cycle through woolly bear and moth in the summer. The eggs that these new moths lay will hatch into the woolly bears that overwinter.

Isabella tiger moth (Pyrrhartia isabella)

The Isabella tiger moth (Pyrrhartia isabella) (courtesy Steve Jurvetson; http://flickr.com/photos/44124348109@N01/501714313)

Do these fuzzy caterpillars tell us something about the winter to come? The legend is that the longer the rusty brown stripe on a woolly bear, the milder the winter. Conversely, a narrow rusty band predicts a harsher winter. There have been a few attempts to correlate the size of the stripe with winter conditions. One of the most well known studies was by biologist Charles Corran in the 1940s. For the first few years of his study, the prediction of the woolly bear was correct, but there was more than enough evidence to disprove the common myth in the years to follow. Some suggest that the length of the rusty stripe may actually tell us something about the harshness of the winter and spring that occurred the year before.

I know deep down that the woolly bear myth is just that—a myth. That doesn’t stop me from doing a few extra lunges to save a woolly bear or two and check out the length of the rusty stripe. Curious about what this winter will bring? I suggest that you join me in the woolly bear lunge.

Curious Chipmunks

by Nancy Olmstead

Crouching chipmunk

A curious chipmunk (photo courtesy of Gilles Gonthier, http://flickr.com/photos/46788399@N00/291562671)

A month ago I was walking in the woods and it seemed like I couldn’t go more than a few feet without disturbing another chipmunk.  The little brown stripe-y streaks were running all over the place, stopping to chirp and chatter at me as I passed.  Don’t worry, buddy, I don’t want your nuts.

We’re having a mast year in the northeast.  The oaks, beeches, and other masting trees are making a bumper crop of seed, which chipmunks eat and store by the cheekful.  This probably explains the superabundance of chipmunks.  The eastern chipmunk, Tamias striatus, can tell when the fall harvest is going to be good.  So they go all out making babies over the summer.  Some of the animals I’m seeing now are probably this year’s offspring, rushing to find, secure, and fill their burrows before settling down for their long winter rest.

Eastern chipmunk with full cheek pouches

Eastern Chipmunk with cheeks filled of food supply, Cap Tourmente National Wildlife Area, Quebec, Canada (image courtesy of Cephas, http://commons.wikimedia.org/wiki/File:Tamias_striatus_CT.jpg)

Scientists have also studied this phenomenon in red squirrels, and chipmunks may be similar.  After all, chipmunks are a kind of squirrel.  They belong to the family Sciuridae, the sciurid rodents, which includes chipmunks, ground squirrels (e.g., prairie dogs), marmots (e.g., woodchuck), and tree squirrels (e.g., gray and red squirrels and flying squirrels).  Red squirrels are also known to anticipate high seed crops and reproduce accordingly.  Females may even have a second litter in the summer that precedes a big fall.

But how do chipmunks and red squirrels know that it’s going to be a good year?  The jury is still out on that question.  It’s hard to measure what individual animals are using as a cue to guide their reproductive “decisions.”  (And by using the word “decisions,” I don’t mean to imply that chipmunks and squirrels have consciousness, just an instinct to reproduce when certain cues are present.)

Scientists involved in these studies have suggested that the visual stimulus of an abundance of flowers may clue the squirrels in, but that explanation is less convincing for chipmunks, who spend more time on the forest floor than up in the tallest trees.  Chipmunks may be able to smell the upcoming bounty by homing in on the subtle scent of all those beech, oak, and maple flowers.  However they do it, it’s pretty cool.

Natural Destinations: Dead Creek Wildlife Management Area

by Cathy Bell

(originally posted on vtdigger.org)

Every autumn, thousands of snow geese take a break from their 5,000 mile southbound migration to rest and feed at Dead Creek Wildlife Management Area in Addison, Vermont.  Journeying from their breeding grounds on the Arctic tundra to their winter range in the mid-Atlantic and southeastern states, the snow geese are but fleeting visitors to the Green Mountain State, descending on our cornfields from October into early November.

The bright white feathers of a snow goose’s body contrast with tips of the wings, which look as though they have been dipped in paint of the richest black.  Young birds are brushed with gray on their backs, giving them a dirty appearance.  Here and there among the flocks are dark gray individuals with white faces.  These steely-looking birds, commonly known as “blue geese,” are the same species as the white ones.  Snow geese of either coloration are far prettier, to my eye, than our resident Canada geese.  Getting to see these visitors from the north is a seasonal treat.

Snow geese

Snow geese at Dead Creek

Hoping to find some snow geese, I went to Dead Creek on Saturday, October 30.  The day started out sunny but clouded up as the big Halloween nor’easter worked its way towards New England.  Driving down Route 22A from the north, I made a right turn onto Route 17.  I had gone less than a mile from Addison Four Corners when I saw a wheeling flock of waterfowl.  Backlit, the winged forms did not reveal any details of their plumage, but the size and flight pattern didn’t seem quite right for Canada geese.  Even as I thought to myself that I must be in the right place, I saw a turnoff on the south side of the road.  I pulled off the highway, shut off the ignition, and hopped out of the car, binoculars in hand.  Looking to the south, I felt my jaw drop in wonder.

About 800 geese were in a field very close by, in easy sight of a viewing platform with interpretive signs.  Hundreds more were in a distant depression.  From the knot of people with binoculars and spotting scopes a quarter mile to the west, I guessed there was another—possibly even bigger—group of geese over there too.  Aerial photo counts that weekend documented more than 4,600 geese in the area, but few people braved the chill wind of the gray afternoon to witness the impressive spectacle.

A northern harrier, its white rump patch catching the watery light, startled the nearest geese into rising from where they rested and fed.  Within moments, the nervousness of a few waterfowl swept through the flock, and hundreds of birds were in the air, honking their discontent in a higher-pitched and more tremulous voice than that of the familiar Canada goose.

Though I looked carefully, I failed to find any Ross’s geese among the swirling clouds of white waterfowl.  Snow geese and Ross’s geese are two distinct species, though very similar in appearance; the rarer Ross’s is more diminutive in build and has a smaller bill.  I later read on the Vermont bird listserv that there were indeed two Ross’s geese at Dead Creek that afternoon, but they were the needles in the haystack of thousands of snow geese.

I may have lucked into witnessing the peak of this year’s snow goose migration, but there’s still time for you to see the spectacular waterfowl as they pass through Vermont.

At 2,858 acres, Dead Creek Wildlife Management Area is administered by Vermont Fish and Wildlife and includes extensive reaches of cattail marsh and stretches of open water.  The geese, however, are concentrated in upland agricultural fields.  The designated goose viewing area along Route 17 is the best place to see the birds, but a little farther south, Gage Road can provide good sightings as well.

Moreover, though the snow geese may be the star attraction, there is more here for inquisitive visitors to enjoy.  Northern shovelers and green-winged teal dabble in the shallow, ponded water of the fields, and once in a while a pectoral sandpiper passes by overhead.  A quarter mile west of the goose viewing turnoff, Route 17 crosses the still, murky waters of Dead Creek.  Mallards and black ducks ply the waters here.  Just over the bridge, a left turn takes you down a gravel road towards a hunters’ camping area.  Look along the reedy edges of the water for great blue herons and wood ducks.  Despite its name, Dead Creek is a lively place.

The creek flows northward, parallel to the southernmost portion of Lake Champlain.  Just seven miles north of where it flows under Route 17, the creek joins with Otter Creek and soon wends its way into the lake.  Its meandering path has been modified by the addition of dams, and today, the state actively manages water levels in the flooded impoundments.

The snow goose hunting season runs from October 1 – December 29 in the Lake Champlain waterfowl hunting zone, with a daily bag limit of 25 birds.  Portions of the Dead Creek Wildlife Management Area, including the upland areas south of Route 17 near the viewing area, are managed as a refuge where no hunting or other public access is permitted.

More information, including maps and directions, is available from Audubon Vermont and Vermont Fish and Wildlife.

Young Scientists Plot for Smart Urban Forestry

by Liz Brownlee

“Wait until you see the accuracy of our plot,” calls the lab team.

The four undergraduates burst with pride, oblivious to the prickling raspberries and thick brush that edge the Intervale forest.

They stop me midstride.  As their lab teacher, I’m fully equipped with aerial maps, GPS, first aid kit, phone, and extra rain gear.  I’m planning to cruise through this pasture towards the soybeans and into the swampy forest.  My goal is to check in with teams at twelve more study plots, spread over the 350 acres of forest and fields.

This lab project is a real, on-the-ground application of their natural resource training.  Most weeks these first-year students learn the basics of field work in big, broad fields (fisheries, stream ecology, forestry, etc.). The field data they record in their weekly labs is important: they use it to learn how to create papers, reports, and essays.

This week, though, the data is headed to city hall.  We’re studying the Burlington urban forest to help the city make informed decisions about valuing and managing the forest.

I need to check in with the next group. It’s incredibly important that the teams describe each plot with accuracy and efficiency.  I know that all the teams are anxious to prove their worth, to share their budding knowledge and field skills.  But this team’s stories cannot wait.

Elliot, a bright-eyed skier from Utah starts first.

The maple we used to mark our plot was so big, our measuring tape couldn’t reach around it, he says.

Aptly named and observant, Hunter chimes in.

There was a deer trail, but that’s it – otherwise it’s untouched.

Eric, a tattooed, intelligent former Marine, knows this isn’t entirely true.

How should we record the land use on this plot, Liz? This isn’t a park, and it’s on the farm but not cultivated land.

We brainstorm the forest’s values: recreation and flood control top the list.

I change my route, unable to leave the pull of their enthusiasm.  Elliot fires questions as we walk the farm’s puddle-filled gravel road.

We didn’t see any sign of invasive species like emerald ash borer – that’s good, right?  And the ground was covered in mud from the hurricane and the flood – do you think the forest will rebound before teams come next year?

The team answers most of their questions before I can chime in, and I know that I’m no longer needed.  I head for the next site when Carly, another lab teacher with twenty more students, calls from the Old North End of Burlington.  We check in, cars honking in the background on her end.

Over two hundred UVM students are taking the pulse of the forest, from tree height and canopy dieback to ground cover and plant-able space. They’re studying over one hundred plots throughout the city, and all in just two weeks.  We’ll crunch the numbers with a program called iTree that’s being used worldwide.  The city will use the results to decide where and what to plant next, and how to properly value a forest that cools homes, mitigates pollution, and absorbs storm water runoff.

They’ve tracked changes in the forest’s health.  They’ve built confidence as budding natural resource scientists.  And next year, two hundred new students will do it all again.

Enough Pumpkins in the Patch?

by Cathy Bell

(originally posted on vtdigger.org)

Back in the middle of September, a headline caught my eye. “Northeast Faces Devastating Pumpkin Shortage,” I read, with a mixture of amusement and trepidation.

Devastating?  Really?  Pumpkins are cheery and plump and orange.  It’s tough for me to take them seriously enough to believe that anyone could possibly construe a shortage as devastating.  Even the name—pumpkin—is irresistibly rotund and bouncy-sounding.  Still, that headline got me a little worried.  I have a tradition of throwing a pumpkin-carving party the weekend before Halloween.  It’s always great fun to gather a group of friends together for a few hours of quality time with sharp knives and slimy pumpkin innards.  What if there weren’t enough pumpkins this year?

Fortunately for pumpkin seekers, it appears that the forecast Great Pumpkin Shortage isn’t so devastating after all.  If you drive through rural Vermont or stop by your local farmers’ market, you will see row upon row of happy-looking pumpkins offered up for sale.  So what’s the story?  Is there a pumpkin shortage or not?

To answer that question, I swung by my local farmers’ market in the Old North End of Burlington and checked in with Lauri Brewster of The Farm at Cold Spring in Milton.  “It’s regional,” said Brewster.  “Low-lying areas got hit hard.  But we have plenty of pumpkins.”

Not all growers were so fortunate.  Many suffered significant losses in the wake of Tropical Storm Irene.  Mark Winslow of Winslow Farms in Pittsford reported that floodwaters destroyed about half his pumpkin crop.  “Approximately 150 tons washed away.  That’s $40,000 in pumpkins.  Because of the loss, we are not able to deliver to our wholesale customers, though we still have an excellent crop for our farm stand.”

Montpelier’s Hunger Mountain Co-op has purchased Halloween pumpkins for over twenty years from a single grower, East Hardwick’s Riverside Farm, said produce manager Robert Kirigan.  This year, about a third of Riverside Farm’s pumpkin crop was lost, so “we are a little short,” Kirigan admitted.

Despite having fewer pumpkins to satisfy demand, prices don’t seem to be any higher than usual this year.  According to Kirigan, “Our pricing is the same as last year.  Although normally shortages would tend to push the price up, we and Riverside Farm decided not to raise our prices.  We wanted to encourage folks to buy real pumpkins, not plastic ones.  And for the sake of the Earth we want them to be organic, not grown with chemicals.  So holding the line on price seemed like the right thing to do.”

With fewer pumpkins around, some vendors turn to out-of-state growers to ensure fully-stocked shelves.  Burlington’s City Market, though, specializes in stocking Vermont pumpkins, produce stocker Kara Brown said.  “We buy them from about five different suppliers, some organic and some conventional.  They’ve all definitely had a tighter supply than last year.”

Dire warnings of a pumpkin shortage hit the media a few weeks after Hurricane Irene inundated the East Coast, with news outlets including the Washington Post, CBS News, and the Wall Street Journal posting stories about the potential for a paucity of pumpkins this fall.  Some pumpkin patches, like those of Winslow Farms, were destroyed outright by flooding.  Even if they weren’t carried away by high water, pumpkins that sat in standing water are illegal to sell—a problem encountered by growers in Burlington’s Intervale.

Irene brought a longer-term, more insidious threat, as well.  Lingering moisture in the fields created an ideal environment for the spread of a host of pumpkin diseases.  Plants may not have to suffer through sore throats or stopped-up sinuses, but they can be afflicted with a wide variety of conditions including wilts, rots, and blights.  Like us, they can succumb to onslaughts by bacteria, viruses, and fungi.

“It may be difficult to imagine,” write Purdue University plant pathologists Richard Latin and Karen Rane in their Identification and Management of Pumpkin Diseases, “but we receive more requests for information on pumpkin diseases and pumpkin disease control than on any other vegetable crop.”

Why pumpkins?  The answer lies in what they are and how they grow.  Pumpkins, of course, are squash.  To a botanist, they’re members of the cucurbit family, related to cucumbers and watermelons.  Most members of this plant family are vines, and pumpkins are no exception; they grow by sprawling across the ground.  Their vines can lengthen by as much as six inches a day during peak growing season.  This rapid growth means that pumpkin plants need rich soil and plenty of water.

The challenge is that too much water creates ideal conditions for pathogens that cause rot and decay. Particularly problematic are puddles that persist on the ground in the pumpkin patch.  You probably know how disappointing it is to find a pumpkin that looks perfect from the top, but that has a big soft spot on the underside, sometimes with visible white mold.  This is Phytophthora blight.  The name is a mouthful, but it’s telling: “phyto” means plant in ancient Greek, and “phthora” means ruin or decay—so you can think of Phytophthora as the Plant Destroyer.  There dozens of different kinds of Phytophthora; one, Phytophthora infestans, caused the Irish Potato Famine.

The species that infects pumpkins is called Phytophthora capsici, and it’s a tricky thing to fight.  It used to be considered a fungus, but it has a few strange traits which have led taxonomists to reclassify it as an oomycete, in a different kingdom of life altogether.  Like fungi, it spreads by producing spores.  One kind, called an oospore, is round and thick-walled; it’s built to last and can persist in the soil for years.  But Phytophthora’s other spore type, known as a zoospore or swimmer, is the fascinating one.  Each swimmer sports two little whiplike tails that it uses to propel itself through water.  The existence of these swimmers means that Phytophthora is more closely related to diatoms and marine plankton than it is to fungi.

There are other diseases that infect pumpkins, too, and many of them thrive when there’s a lot of late-season moisture, as there was this year.  In fact, the susceptibility of pumpkins to disease, combined with strongly-seasonal demand (pumpkins are worth a whole lot less if they go to market on November 1), sets them up as a crop that has potential for shortages.  Luckily, weather that creates ideal conditions for disease is usually localized.  In any given year, there’s probably some region of the country that has a pumpkin production problem … but there are plenty of other pumpkins in the patch, if you’re willing to go a little farther afield.

That’s good news for those of us who are shopping for pumpkins, but small consolation for farmers who suffered losses during Tropical Storm Irene.  “I just wish there was a real insurance program for specialty crops,” said Winslow.  “We do not use the government program because our past experience is that it is completely inadequate.”

Rock: The Best Thing about Vermont

by Becky Cushing

I’m not a geologist, but recently I learned a thing or two about Vermont bedrock that bumps it above maple syrup or cheese on Vermont’s “Best of” List.

By nature, I ask a lot of questions: What trees are those? How deep is this soil? What bird lives in that nest? Turns out, a lot of the answers are directly or indirectly related to the kind of rock below. And in Vermont, those are calcium-rich rocks—which create an alluring hotspot for many cool, rare or economically important plants.

Picture Vermont 500 million years ago, covered by a vast ocean full of planktonic organisms—a primordial soup. Over time, generations of these tiny organisms died and their bodies drifted to the seafloor laying down sediment full of calcium. When the land shifted and the ocean receded, these compressed sediments formed the basis for the calcareous bedrock of today’s Champlain Valley, mostly dolostone.

So what’s the deal with calcium? Plants need it for metabolism and structure, just like we do. It also helps to raise the pH of the soil (thus lowering the acidity). The chemistry gets a little complicated—but find enlightenment (like I did) in a bottle of Tums. Calcium carbonate, well-known for soothing heartburn, also neutralizes acidity in soil making it more alkaline. Who cares? Bacteria, for starters. And those rascals are necessary for making nitrogen available to plants. In fact, under acidic conditions many nutrients give plants the cold shoulder—instead they’re hooking up with each other or leaching out of plants’ reach. Where dolostone (or limestone) is close to the surface (thanks to several glaciations and years of other erosive processes) these nutrients are more willing.

Farmers have known this forever and call neutral or alkaline soils “sweet.” Plant biologists know it too. I’m embarrassed to admit it took nearly a semester of botany for me to pick up on the pattern of our field trip locations—calcareous bedrock stared me straight in the eye.

Maidenhair Fern

Maidenhair fern near Gleason Brook (photo courtesy of Ryan Morra)

For instance, check out the Long Trail near Gleason Brook in Bolton, VT. If you park in the lot off of Duxbury Rd. and hike up a quarter mile or so, you will start to see telltale plants of calcium-enriched soils like maidenhair fern, wood nettle, blue cohosh, plantain-leaved sedge and white baneberry (doll’s eyes). Sugar maple, white ash, basswood and hophornbeam dominate the tree canopy while striped maples sit eagerly in the understory. Stay on the trail to find the dense patch of pale touch-me- not, an irregular pale yellow flower, at the base of a steep slope on the south side of the trail. Here the downward movement of soil and nutrients from the upper slope along with the exposed calcareous bedrock create a double whammy of plant nutrient bliss. Scientists describe this type of vegetative community as a Rich Northern Hardwood Forest—sounds fancy but Vermonters are spoiled with this natural community-type in ample abundance.

Wood Nettle

Wood nettle near Gleason Brook (photo courtesy of Ryan Morra)

Vermont’s best-kept secret, dolostone, has broader implications than satisfying curious botanizers. Conservation planners, for instance, can use geologic surveys to identify potential priority areas for rare plants among Vermont’s varying bedrock landscape. If you travel a few miles farther on the Long Trail up toward the summit of Camel’s Hump your heartburn might return—the rock transitions to more resistant igneous and metamorphic rocks resembling the bedrock geology of our neighbors to the east in “The Granite State.” At the summit’s rare (seemingly masochistic) alpine plants thrive under harsh, acidic conditions—yet another botanical treat thanks to the state’s multifarious geologic past. Motley geology begets vegetative diversity.

So, next time you douse your pancakes with maple syrupy goodness, take a moment to thank the nutrient-rich soil conditions integral to the Sugar maple-dominated forest community of Vermont.

And remember the best—and oldest—thing about Vermont is the rock.

 

 

Winding Through the Path of Least Resistance

by Ryan Morra

“Slow down, you’re moving too fast, you’ve got to make the moment last.” Simon and Garfunkel phrased it well. If you look at aerial photographs of the Winooski or Lamoille Rivers in northern Vermont, you’ll notice how dramatically the rivers snake through Champlain Valley with one horseshoe-shaped bend after the next.

The Winooski River

The Winooski River flowing through Burlington and Colchester, VT

The Lamoille River

The Lamoille River flowing through Farifax, VT

Launch your canoe into these rivers and you will come face to face with the phenomenon known in the scientific community as fluvial geomorphology. This phrase has become increasingly familiar to the public in the aftermath of Tropical Storm Irene, where fluvial geomorphologists have been called upon to explain the widespread flooding experienced across the state. But what exactly does fluvial geomorphology mean? It refers to the ability of flowing water (fluvial) to shape (-morpho-) the earth (geo-). To be precise, it is the study of all that (-logy).

Half Moon Cove

Half Moon Cove in Colchester, VT

An easily observable way that rivers shape the earth around it is the formation of the horseshoe-shaped meanders, called oxbows, seen in the Champlain Valley. More curious are the crescent-shaped lakes alongside the river, the most dramatic example of which is Half Moon Cove in Colchester. If your instincts tell you that this U-shaped lake may have once been a part of the Winooski River, you are correct. How it formed river can be explained by first thinking about the path of least resistance for a river.

Paddling down the final stretch of the Winooski in a canoe is a dramatically different experience than trying to navigate the steeper rivers found in the mountains. In the Green Mountains, the steep slope causes the water to flow fast and cut out a straight channel on its way down to Lake Champlain, and there is little need to propel yourself along (adrenaline junkies will still find cause to do so, however). Once the Winooski reaches the Champlain Valley, it begins to follow a far more convoluted path, and it is hard to go anywhere in your canoe without paddling.

The soils in the valley are soft clays, silts, and sands that provide little resistance to the now slow-moving river, so the river will bend around at even the slightest obstacle. Once a meander has developed, a feedback process begins that causes further erosion and meandering. Along the outer edge of a curve, the water moves faster than the water on the inside of the curve, since the water must travel a greater distance in the same amount of time. The water erodes the banks along the fast-moving outer edge of the curve, and deposits the silt and sand along the slow-moving inner bends.

If you want to land your canoe during your trip, you will have greater success along these inner bends, where gradually rising sandbars have been built up through this deposition process. Trying to exit on the outside curve of a river bend will prove far more precarious, as the streambank drops of sharply into the river! As the river cuts away at its own banks, it can eventually cut through the remaining bit of land at between the two river bends, and the channel straightens.

Meander Process

How a meander becomes an oxbow lake (source: http://www.geocaching.com/seek/cache_details.aspx?guid=a2541785-59cc-492b-aefb-06ce29e973c6)

Major floods like those experienced after Tropical Storm Irene are sometimes the catalyst for this final step. While we may continue to alter the flow of a river through creating new dams and reinforcing the banks below streamside roads, river waters will constantly look for their path of least resistance, and we may find that our interests are in conflict with the hydrologic forces facing us.  Next time you enjoy a float down the sinewy channels of the Winooski or Lamoille river, note where each bend and twist occurs. When you take your children and grandchildren out in the future, it may not be the same—fluvial geomorphology may have worked its magic.

Time Slips

By Danielle Owczarski

Crickets sound their high-pitched hum, blaring sirens swell and shrink, sweat percolates in overlapping areas, distant music floats through the moonlit breeze, insomnia returns, a kingfisher chatters along the lake shore, a main sail flaps in the breeze – all signifying the shift to summer in Burlington. Spring has its moments with its ephemeral blooms, but with summer, we shed the last layers of clothing. White skin peeks out no longer shy, soon many shades darker and prominently displayed. We relish the summer months without the taunting of spring’s undulating meteorological moods. Like our seasonal feathered friends, we break out into bold colors and partake in the ritualistic dance of the Burlington Jazz Festival and music on the waterfront. The neighborhood druids welcome the summer solstice by gathering around the Earth Clock in Oakledge Park, drumming in the sunlight’s energy.

Midsummer festivals, boldly celebrated in pre-Christian times and still today in many cultures under an altered guise, take place around the solstice. The Oxford English Dictionary states that summer has its origins in Old English as sumor, sumere, and somera among other variations first recognized in text c. 825, referring to its role as the warmest season of the year. And while summer more accurately applies to the astronomical solstice then to the actual beginning of the seasonal and climatic change, it is understood as a time of fertility, growth, and warmth. Bonfires and heavy drinking are the most common signifiers of midsummer revelries throughout the world, the celebration linked to the birth of John the Baptist, born six months prior to Jesus. However, stripped of its religious shroud, in the silence and beauty of the early morning, summer is the celebration of energy transformed into life.

Despite the simplicity of its title, summer is dynamic, generating an ever-changing understory and flow of biotic change. Those of us who work outside during this time of year follow the influx of hatching insects good and bad. Appearing first are the black flies, followed by the deer flies and mosquitoes. While the former two usually abide by shorter seasons, the mosquitoes continue hatching throughout the late summer months. Overshadowed by the annoying, small flying insects are those who act as predators keeping them at bay.

Dragonflies, unbeknownst to some, live most of their lives (up to four years) as armored nymphs in calm aquatic environments. The warm sun of early summer heats the waters, enticing the mature nymphs to the surface where they crawl out and clasp themselves to tall grasses, wood, and stone. Here they begin their hatch. Attached to a cattail leaf above the water, the nymph’s exoskeleton begins to dry and crack along the back where the dragonfly emerges, compressed and translucent, expanding into a world of bug feasts, avian maneuvers, sex, and egg laying. Their terrestrial phase occurs no longer than two months causing their numbers to dwindle by late summer.

Those of us working inside this time of year suffer through the mocking rays of light filtering through paned glass windows. The vigor of those coming in from outside tickles the nerves and draws conscious thought away from tasks and into daydreams of lake breezes on bare skin, lush winding hiking trails, and the transforming hues of clouds low on the horizon. For most of us trying to take advantage of the summer day, a strange phenomenon occurs, while the length of the day in relation to sunlight increases, time seems to move more quickly. Weekends fill with social obligations, and the list of things to do and places to visit become too numerous to accomplish. Summer spurs the endless chase of the elusive present moment.

In nature, as the season progresses, the once electrifying greens of spring begin to dull. Before we know it, tomatoes are ripening into deep reds and purples, and the goldenrods and asters are blooming. In town, the college students are moving into their dorms and young children board the yellow bus while we wait patiently in traffic. Some welcome the change with anticipation of harvest festivals, cider donuts, and corn mazes, while others feel depressed by the notion of winter’s encroaching darkness. Despite our resistance, the mayfly, stonefly, and caddisfly, each year during this time, hatch, lay their eggs, and die. The brook trout rise to eat, and a small red maple leaf flutters, dropping slowly to the water’s surface.