Ice is Magic

published Feb 5, 2020 in the York Weekly, Portsmouth Herald and Foster’s Daily and online at seacoastonline.com

I spent almost the entire first semester last year having my freshmen STEM class run experiments about ice. Every morning, when I walk my dog, we follow a path along the river and observe the ice, marvel at the huge slabs of ice that are carried downstream and stacked like pancakes in some places, crunch our way over the paper-thin ice that coated the hummocks of the floodplain after the last brief thaw, watch dangling orbs of ice form in the waterfall that spills down to feed the river. I, like so many others, am obsessed with ice.

If you think about it, ice formation on a pond or lake is fairly straightforward. As the water gets colder, it gets denser and starts to sink. Liquid water reaches its maximum density at 4 °C (39.2 °F), after that it continues to get colder and freeze solid, but as it freezes, it becomes less dense and floats to the surface and we end up with ice-covered lakes.

Ice slabs pile up in Little River

At first, the ice is paper-thin, fragile sheets that crumble in your hand. As winter’s cold progresses, the ice gets thicker and thicker as more ice is added from the bottom. As long as the pond or lake is deep enough, there should always be at least some liquid water underneath the ice. This is very helpful to the animals that live in the pond or lake. They can survive in the liquid water near the bottom until the spring thaw.

Now, think about a river or stream in which the water is constantly moving. All of that turbulence makes it difficult for a nice sheet of ice to form. On cold winter nights, the surface water of a river cools, crystals of ice form and start to grow. The constant water movement keeps the crystals from growing together into a solid sheet, instead you get a slushy mixture of water and ice called frazil ice. You can see this floating on the top of a river in early winter, or instead of floating on top, because the crystals are so small, they can easily be carried by the turbulence down to the bottom of the river.

Ice slab close-up with river behind it

As temperatures continue to drop, the frazil ice can start to join together at the surface and form round plates of ice with upturned edges (from the plates bumping together). This is called pancake ice. Or, what was more common on my river, ice will start to form along the edges of the river. Ice forms more easily along the edges because there is typically less water movement and the temperature of the shallow water on the edge cools faster. This is called border or shore ice. Border ice will generally enlarge toward the middle of the river until the ice from both sides meet.

Border ice forms along a small stream

Another interesting way a river can freeze is when the frazil ice that is transported to the bottom of the river attaches to the streambed and builds from the bottom up. This is called anchor ice. Anchor ice can grow very rapidly and block the flow of a river or stream causing local flooding. If there is particularly low flow of water along the bottom, an enormous amount of anchor ice can build up. This can be extremely harmful to aquatic life because the anchor ice can physically lift up parts of the streambed and move it downstream, movement akin to the action of a bulldozer, killing small fish and aquatic invertebrates (like dragonfly or caddisfly larvae) that live in the streambed, or freezing fish eggs that were waiting for spring to hatch.

I thought I first fell in love with ice in some dramatic location, perhaps when I crossed Lake Champlain on the ferry one cold winter’s night and watched the prow cut through the ice and listened to it grind against the hull of the boat, or when I was travelling as a National Geographic Grosvenor Teacher Fellow in the Arctic Ocean and witnessed firsthand the ethereal beauty of icebergs and the vast expanses of pack ice in the polar sea. But watching the beautiful, ever-mutable ice along my little river this winter has made me realize that I’ve loved ice since I was a kid watching icicles dangle from the gutters of my house, that no matter where you find it, ice is magic.

Join the soft-shell clam recruitment network

published January 29, 2020 in The York Weekly, Portsmouth Herald and Foster’s Daily and online at seacoastonline.com titled ‘Nature News’

Clam recruitment boxes will be placed on clam flats in Wells Maine this spring Brian Beal photo

Dr. Brian Beal, Director of Research for the University of Maine at Machais Downeast Institute (DEI)-the easternmost marine research laboratory in the entire United States – gave a talk a week or so ago up in Wells about a research project that will start this spring all along the coast of Maine. The main focuses of the DEI all have to do with shellfish, primarily clams.

Brian was down in Wells explaining why large wooden boxes would be appearing on some clam flats in Maine, from Wells north to Sipayik, this spring and summer. The boxes are part of a study aimed at understanding how best to protect young soft-shell clams at a critical time in their development-when they are transiting from a water-born planktonic life to settling into the mud and sand flats and growing into delicious steamers. 

The clam recruitment boxes appear to provide a safe place for juvenile planktonic clams to settle Brian Beal Photo

Protecting soft shell clams from what? Primarily the invasive European green crab (Carcinus maenas).  Green crabs were introduced to New England back in the early 1800s by travelling in the ballast of ships carrying cargo from Europe to the United States.  Since then they have travelled up the East Coast, decimating the soft shell clam industry and have more recently (the late 1980s) reached the West Coast where they are wreaking similar havoc from San Francisco up to Seattle.  One reason green crabs are such a problem is that, unlike our native crabs, green crabs can swim out onto the mudflats to hunt. Our native rock and Jonah crabs don’t do this-they can’t swim and can’t get out and back to the mud flats as the tides ebb and flow..  Adult green crabs swim out to the mud flats at high tide, grab the soft-shell clam siphons (the fleshy clam ‘necks’), pull them out and eat them. Our soft-shell clams have adapted to this by digging deeper into the mud so that they can escape. However, a probably bigger problem is that young green crabs  (-perhaps a couple millimeters in size) also settle on the mudflats and prey upon anything smaller than themselves-juicy morsels like young soft-shell clams. 

To understand how the recruitment boxes work you have to know a little bit about a clam’s life cycle.  Before I joined the Wells Clam Conservation Commission almost a decade ago, I hadn’t understood how complex that life cycle is and how threatened it is by the invasive green crab. 

The life of a soft-shell clam (Mya arenaria) begins on a warm spring day when both male and female clams release their sperm and eggs into the water, if the two should meet-fertilization occurs.  This is called broadcast spawning and time is everything. The young that develop from this union are planktonic, they don’t look much like adult clams, instead they look like tiny blobs with tufts of fine cilia that they use to swim through the water.  These larval forms are called trocophore larvae that then mature into veliger larvae. The veligers look like a shell-less swimming clam. These baby clams come to intertidal flats via the water column. They swim for 2-3 weeks depending on seawater temperature and location along the coast, and then settle to the flats.  They are about the size of a grain of sand. This is when they are most vulnerable to predation. Here is where the recruitment boxes come in.  

Recently settled clams are at most danger from juvenile green crabs Brian Beal photos

Recruitment boxes are large wooden boxes with mesh on both the top and bottom.  Planktonic clams that settle into these boxes appear able to have much higher survival rates than those settling on the unprotected mud or sand flat.  

Mesh on both top and bottom of the boxes protects young clams from many predators Brian Beal photo

Why put out recruitment boxes? Soft-shell clam landings across Maine have declined by 45% since 2001, and few seem to be aware of this. An interesting tie-in with climate change appears to be that warmer sea surface temperatures (as we have been seeing in the Gulf of Maine) encourage explosive growth of green crabs.  Brian’s project aims to increase public awareness of what is occurring within this iconic fishery and create a statewide data set for fisheries managers in the Department of Marine Resources, and for other fisheries scientists, to better understand factors that affect the health and well-being of the soft-shell clam fishery.  

Whether you live in Maine or New Hampshire, if you want to get involved in this ‘recruitment network’ contact Brian at the Downeast Institute.  Dr Beal is looking forward to working with clammers, clam conservation committees, elected officials, schools and students in each community to learn about the early life-history of clams and what may be regulating or controlling their numbers.  Ultimately, he would like to create a network where the coastal communities that are part of this first trial are a subset of a larger group of communities all doing similar work that may play an important role in how soft-shell clams are managed.

In winter’s cold, the subnivean zone is abuzz

Published January 21 2020 The York Weekly, Portsmouth Herald and Foster’s Daily and at seacoastonline.com Titled ‘Nature News’

The subnivean zone lies between the snow and the earth.

This winter has been troublesome; a few weeks ago it was so cold my pipes froze, then it we climbed to unseasonably warm temperatures, then some more snow, and now, very cold again-my pipes continue to freeze. One thing that makes me happy is that we have a nice layer of snow on the ground, insulation that is is vital to the survival of many of the plants and small mammals, even microscopic life forms, that are essential parts of our Northern ecosystem. So, for many, the recent snow was welcome relief from the cold.

While the surface seems empty, underneath, at the interface between ground and snow, a veritable city is rising. Old leaves and branches hold the snow up, creating an open space. The ground also radiates heat, warming the overlying snow, which instead of melting sublimates (when a solid turns into a gas without first becoming a liquid) directly into water vapor. Both of these processes leave a space between the snow and the ground, called the subnivean zone.

The word “subnivean” comes from the Latin for under (sub) the snow (nivean) and is a scientific term referring to the open passageways that form under deep snow.

Six or more inches of snow are all that are needed to trap the earth’s heat and allow a subnivean zone to form. This zone remains humid because of the transformation of snow into moist water vapor and is capped by a layer of ice that acts as an insulating roof. The temperature of the subnivean zone is generally a constant 32 degrees, protecting species that would otherwise freeze.

The most common inhabitants of the subnivean are mice and voles — they make tunnels under the snow connecting sleeping areas and sources of food. Red squirrels also burrow into the subnivean to stash food. Entrance holes to these networks allow carbon dioxide to escape. Carbon dioxide is released when these animals breathe and by the ground itself. Without the entrance holes to serve as ventilation shafts, carbon dioxide could build up to lethal levels.

While the subnivean zone provides protection for mice and voles, it is also the hunting ground for the short-tailed weasel (or ermine), a weasel that, except for its black-tipped tail, turns snowy white in the winter. This small weasel, just the right size to live and hunt in the tunnels under the snow, is a major predator upon small rodents.

All you need is about 6 inches of snow to allow the subnivean space to form

Recent research has unearthed a whole new category of inhabitants of the subnivean zone — microbes that are proving to be important players in the cycling of both nitrogen and carbon dioxide between the earth and the atmosphere. A deep snowpack with an active subnivean zone appears to encourage a healthy microbial population that, through respiration, releases significant amounts of carbon dioxide into the atmosphere. Studies suggest that as much as half of the carbon taken up by plants in the summer is released back into the atmosphere by microbes in winter (Paul Brooks, University of Colorado Boulder). At the same time these microbes, by processing and storing nitrogen, fertilize the soil as the snow melts.

Without a healthy snowpack, without these snowpack microbes, plants don’t do as well come spring. While these microbes may be releasing a lot of carbon into the atmosphere during the winter, they are also necessary for healthy plant growth — plants that will absorb carbon dioxide throughout the growing season.

For all these reasons, it seems to me, a nice deep snow, serving as an insulating blanket on the earth, is a welcome part of our northern winter.

Nature News: New England forests will have to evolve with climate

published January 15 2020 in the York Weekly, Foster’s Daily and the Portsmouth Herald and on seacoastonline.com

Dryad emerging from an old dead tree. Dryads protect and die with their trees. I wonder what they are thinking as our forests succumb to climate change-who do they go after? All of us who use fossil fuels?

This past weekend was unseasonably warm. Record-breaking in fact, for New England, with temperatures a good 7 or 8 degrees warmer than past records.

It seemed like everyone was out taking advantage of the balmy weather to take a walk in the woods. I headed up a side trail on Blue Job Mountain and while working my way up a slushy streambank looked across a clearing and saw something I had never seen before. There, in an old broken-off tree stump was a figure, made of wood, that looked to be climbing out of the tree.

The tree must have been felled relatively recently because the wood was still a bright orange-brown, a splash of color surrounded by the snow-covered pines and oaks. It looked raw and newly exposed. Sunlight hadn’t gotten to it yet (ultraviolet rays break down the cellulose in wood, bleaching out the color, giving it a silvery gray sheen). This figure that I, rationally, knew was just a random carving of the wood into human form, looked back at me. I knew it was just wood, but it still was magical. I could see how people from many different backgrounds, from all over the world, have believed that there are spirits that inhabit trees, so for a moment I believed a wood spirit was looking back at me.

Trees have lives that follow vastly different time scales from ours. They usually live much longer than we do and don’t move as we do. They are root-bound. They only move by reproducing, by sending their seeds out ahead of them into new territory. This warm weather was a reminder to me of their vulnerability. How is the rapid warming of our Earth going to affect the forests of New England?

A little over ten thousand years ago, the glaciers were receding and trees were re-colonizing New England. Slowly their seeds were carried or blown north and slowly they colonized the newly formed earth. This is a process called succession. When there is no dirt (as when glaciers had scoured all the dirt from the land), first lichens and mosses colonize bare rock, break into it and build soil. Then grasses and small plants move in, followed by shrubs, followed by fast-growing, light-loving trees, followed finally by the trees of a mature forest – the beech and maple, pine and oak of our temperate, deciduous forests.

Now, as conditions shift, as it warms, many of these trees need to move north or die. According to Mass Audubon’s “Effects of Climate Change on Woods & Forests,” a general rule of thumb is that “most tree species can colonize habitat beyond their existing range at a rate of 100 km in a 100 years (about 62 miles per 100 years). Some species will be able to move that fast, but warming temperatures will likely require forests to shift by 400 to 600 km (about 250 to 370 miles) by 2100, a rate faster than most species can tolerate.”

One of my favorite types of tree spirits are the Dryads. I first read about these as a child in the classic Bullfinch’s “Mythology.” According to Bullfinch, Dryads are nymphs or spirits, bound to particular trees, caretakers of the trees.

“Dryads or Hamadryads, were believed to perish with the trees which had been their abode and with which they had come into existence. It was therefore an impious act wantonly to destroy a tree.” I guess the caretaking days of my Dryad were over. Her tree had been felled by age or a wind storm. Perhaps that is why she was stepping out of the tree?

Susan Pike, a researcher and an environmental sciences and biology teacher at St. Thomas Aquinas High School, welcomes your ideas for future column topics. She may be reached at spike3116@gmail.com. Read more of her Nature News columns online.

Why do some trees get so tall?

published 12/31/2019 in the York Weekly, Foster’s Daily, the Portsmouth Herald and online on seacoastonline.com

I was just out visiting my son who lives on the coast of Northern California, the land of tall trees, the coast redwoods.  Coast redwoods (these are the state tree of California) are the tallest trees on Earth. I was thinking about our New England tall tree, the white pine (the state tree of Maine), and wondering whether they ever had a chance of growing as tall as the coast redwood.

Navarro River Redwood State Park near Mendocino California

There are a large number of factors that determine how and why a tree grows tall: genetics, environment, age.  The primary reason for a tree to grow as tall as it can is to beat surrounding trees to the sun. White pines and coast redwoods are great at this and will dominate a forest if they can get to the sun first.  White pines typically grow to about 150 feet tall (however pre-colonial white pines have been estimated to reach heights of at least 230 feet) while coast redwoods grow twice as tall-300 feet and taller (the tallest tree in the world is a 379 foot tall coast redwood named Hyperion).  How do they do it?

The two problems that have to be overcome to grow super tall are water and wind.  Coast redwoods tend to occupy sheltered valleys where they are protected from wind.  Like all trees they need to somehow distribute water to all parts of the tree. The long-held dogma of how this is accomplished is that groundwater enters the roots and is pulled upward through the tree by water evaporating from pores in the leaves.  Water is sticky, so as one water molecule evaporates from a pore in a leaf it pulls another water molecule up after it. The taller a tree grows the more difficult it is to get water up to the topmost leaves-gravity becomes a major drag. If those leaves can’t get enough water photosynthesis and growth start to slow.   

However this upward flow of water  isn’t the whole story. It turns out many trees can also absorb water into their leaves and move it downward towards the roots. There has to be water vapor in the atmosphere for this to be a useful adaptation.  Coast redwoods live in the fog belt, their needle-like leaves are almost constantly bathed in fog. Studies by the National Park Service found that some coast redwoods obtain 40% of their water from fog, not their roots!   And, according to a study on coast redwoods published in Functional Ecology (“Pushing the limits to tree height: could foliar water storage compensate for hydraulic constraints in Sequoia sempervirens?” published 2014 by H. Roaki et al) the pinnacle (topmost) leaves of the tallest growing coast redwoods stored water better than trees that didn’t grow as tall. So, tall-growing coast redwoods can take advantage of all that ambient water in the surrounding fog and both store and use it for growth.

Another factor in height is age-it takes time to acquire all of that biomass.  White pines easily live a couple hundred years-the oldest known specimens are over 400 years old.  Coast redwoods, on the other hand, are among the oldest living things on Earth-they can live for more than 2,000 years (the oldest living coast redwood is 2,200 years old).   Hyperion, the tallest tree on Earth, a baby by coast redwood standards at somewhere between 600 and 800 years old has still had a remarkably long life.

Redwood stumps provide nutrients for new growth. Here some sorrel grows at the base of a stump

So, while our East Coast white pines probably couldn’t ever grow as tall as coast redwoods, -conditions and adaptations aren’t quite right-one similarity between these two species is how it feels to walk into a white pine or a coast redwood forest.  There is a cathedral like quality to these forests, they are quiet and dark. The filtered sunlight adds to their majesty, illuminating the mist in much the same way that light falls through the stained glass of a human-made cathedral and illuminates the dust motes floating through the air.   These forests we walk through today are largely young trees. Just imagine the grandeur of a pre-colonial forest, fully mature white pines or coast redwoods reaching towards the stars.

Chickadee-dee-dees!

published Dec 25, 2019 the York Weekly, Portsmouth Herald, Foster’s Daily and seacoastonline.com

I think if you ask any New Englander to name the top three birds at their feeder, the chickadee would be on everyone’s list. I also think that of any of the common bird calls in our forest, the chickadee’s is the one most of us could easily identify. These tiny, round birds with a black cap and bib that contrasts with its white cheeks are found all over the northern parts of the United States and up into the middle of Canada.

black-capped chickadee

When not living in the suburbs you can find them in deciduous and mixed forest, almost any kind of open woodlands, as well as thickets. When we clear forests for agriculture or development, we are increasing the amount of forest edge – a habitat type that chickadees love (unlike something like an ovenbird that requires deep woods for nesting).

The black-capped chickadee (Poecile atricapillus) is one of seven species of chickadees found in the United States. They all have similar body shapes with sometimes subtle differences in color or streaking on their heads. For example, the boreal chickadee (the other New England chickadee) has a brown cap and cinnamon flanks and a more northerly range, preferring the boreal forests of Canada and the mountains of New England.

Chickadees probably do so well with humans due to their flexibility and curiosity. They are highly social birds that are quick to explore new environments and take advantage of resources (they will usually be the first bird to use a new feeder). According to the Cornell Lab of Ornithology, one study found that “every autumn black-capped chickadees allow brain neurons containing old information to die, replacing them with new neurons so they can adapt to changes in their social flocks and environment even with their tiny brains.” They really do have tiny brains, which makes their ability to memorize that much more remarkable. They often hide food for later use and can remember thousands of hiding places!

Try listening to their calls. They actually have a very complex language, much more than the obvious chickadee-dee-dee. They can communicate information about other flocks, predators and foraging information. For example, they add ”-dees” to their chickadee call to indicate higher threat levels.

From the number that show up at my feeder every day one, wouldn’t know that we are in the middle of a mass extinction of birds. A recent Science Magazine article recently reported that there has been a 29% decline in birds in the United States over the past 50 years (that’s almost 3 billion fewer birds on the North American continent today compared to 1970!). While chickadees aren’t considered endangered, or even threatened at this point, their distribution is expected to shift and their numbers decline due to ongoing climate change. A 2017 report by Massachusetts Audubon predicted that by 2050 the black-capped chickadee population is likely to disappear from coastal areas of Massachusetts and decline substantially throughout southern New England as rising temperatures push their range to the north.

For now, if you want to attract chickadees to your backyard, provide feeders (they are one of the easiest birds to attract to a feeder), black-oil sunflower seeds and suet will do the trick, and some standing dead trees for cavity nesting sites (they also like nest boxes).

While chickadees are around all year, I think of them as winter birds. Watching them at my feeder as snow lightly falls is a wonderful way to welcome winter in New England.

Susan Pike, a researcher and an environmental sciences and biology teacher at St. Thomas Aquinas High School, welcomes your ideas for future column topics. She may be reached at spike3116@gmail.com. Read more of her Nature News columns online.

Red Crossbills in New England

published Dec 17 2019 The Portsmouth Herald/seacoastmedia.com

I have been watching the “winter” birds return to my feeder – juncos and titmice, downy and hairy woodpeckers, cardinals and nuthatches. A birding friend who lives in Colorado just posted some gorgeous photos of red crossbills in his hometown of Estes Park. He said he is seeing them everywhere. I have never seen a crossbill (a type of large finch) even though we have both red and white-winged crossbills in New England, particularly in the winter. The North American range of the red crossbills that my friend Scott Rashid, founder of the Colorado Avian Research and Rehabilitation Institute, photographed extends down into the mountainous spruce and pine forests of Central America, while the white-winged crossbill range is mostly in the boreal coniferous forests of the north.

Both of these crossbills could, I think, be mistaken for a house or purple finch by a birder of my caliber (poor). I wonder whether I have seen crossbills in my backyard, but assumed they were house finches? Crossbills are larger than house and purple finches and both the white-winged and the red crossbill are rosy red all over with dark wings whereas the house and purple finches are reddish mostly in front. I’m describing male coloration – the females of all these species are drab, with the finch females being brownish and the crossbill females being yellowish-green.

Crossbills have a really wonderful adaptation to their lives in coniferous forests. Their bills cross at the tip so that when their bill is closed the tip of the bottom bill protrudes up and the tip of the top bill protrudes down forcing the upper and lower parts to cross each other. According to the Cornell Laboratory of Ornithology, crossbills employ a special technique using these unique bills to get to their favorite food, pine seeds. “A bird’s biting muscles are stronger than the muscles used to open the bill, so the Red Crossbill places the tips of its slightly open bill under a cone scale and bites down. The crossed tips of the bill push the scale up, exposing the seed inside.” They then extract the seed using their tongue and bill together.

One fascinating fact about red crossbills that Scott shared with me was the wide variety in overall size and particularly in bill size among what is now considered the one species of red crossbill (Loxia curvirostra). For example, there are types of red crossbills that are smaller in size with smaller bills who specialize in the smaller pine cones of hemlock trees while larger billed types will specialize in larger pine cones. There are currently 11 different types of red crossbill recognized in North America.

Another cool fact about both red and white-winged crossbills is that they are opportunistic breeders. Because their diet is largely composed of pine seeds (white-winged crossbills can eat up to 3,000 conifer seeds in one day!), because they feed pine seeds to their young, and because pine trees produce cones at different times of the year, these birds can breed whenever the seed crop is largest. This might mean nesting in the depths of winter – something I wouldn’t expect to see, a nest with young or some fledglings hanging out on a snowy afternoon.

The best time to find crossbills around is in the winter as they wander about in search of food. According to the Cornell Lab, “Crossbills are nomadic, especially in winter, and in some years irrupt far south of their normal range. At these times, they may show up in evergreen forests, planted evergreens, or at bird feeders.” Sometimes cone crops will fail in their breeding ground and migrants will show up further south in search of food. Making sure to include a variety of native conifers in your backyard can help attract them. Cemeteries and parks with ornamental spruce and pine plantings are also a good place to look as they often attract crossbills in winter.

Everyone I know who is a “real” birder has seen crossbills in New England in winter, so my personal challenge is to try to join the ranks. To that end I’ll be paying a little more attention to anything that looks like a house finch and to any reddish-pinkish birds hanging out in my conifers and feeding from the pine cones dangling from the upper branches.

Susan Pike, a researcher and an environmental sciences and biology teacher at St. Thomas Aquinas High School, welcomes your ideas for future column topics. She may be reached at spike3116@gmail.com. Read more of her Nature News columns online.