Friday, September 25, 2015

Autumn Apples

Golden sunshine and a bluebird sky arched above as we meandered down a lonely backroad. I was paying attention to driving, but my passenger was focused on something else. “Apples!” he exclaimed suddenly, as we cruised past a few trees in the road ditch. He’s always on the lookout for apples. We turned around and pulled off the shoulder, then rummaged around in the car for bags. Soon we were clambering down the bank.

The first tree we came to had small, yellow apples. One bite was all I needed. The tart, dry flesh was impossible to swallow. We moved on to the next tree. Plucking a deep red apple, I discovered that it had a large brown spot on the far side. A tentative bite revealed mushy, sweet innards. “Might be good for sauce,” I mused. Every fruit we picked had a brown bruise, though.

Looking back toward the first tree I noticed a third trunk, its branches so intertwined the others that we hadn’t noticed it at first. The large, yellow-green apples were burnished with red, and they dangled invitingly among deep green leaves. One bite was all I needed. Crisp flesh fairly jumped through my teeth, and a tart zing added interest to the sweetness. Now this was an apple. We quickly filled our bags.

Arriving home, we discovered the driveway full of an entirely different type of apple. Small, brown, dried-out spheres lay among the fallen oak leaves. If you could make ping pong balls out of brown paper bags, this is what you’d get. Not very appetizing, but then that’s not their goal, and their purpose has already been fulfilled.

Oak apples are not a fruit at all. They are galls – the nurseries for tiny wasp larvae. Earlier this summer, a woman pulled a similar gall out of her pocket so I could identify the outbreak at her home. The color drained from her face when I mentioned wasps, and I could see through her panicked expression that she was imagining a swarm of yellow jackets ambushing her yard. Luckily, the wasps that create these galls are the small, non-stinging kind, and she has nothing to worry about.

While oak apples won’t make good applesauce, they do provide food for thought. Oak apple gall wasps (there are several different species) have a complicated, double life cycle, known as the “alternation of generations.”

The brown, papery galls now on my driveway once protected growing and pupating wasp larvae high in the branches of an oak tree. Male and female adult wasps exited the galls this summer. The wasps mated, and then the females burrowed into the ground where they laid their eggs on the roots of oak trees. The larvae from those eggs will feed on the roots of the oaks for more than a year before they pupate. They emerge as generation of female-only, wingless wasps. This underground segment of the life cycle, from egg to larvae to pupa to wingless female adult, takes over a year. The offspring of the galls I found this fall won’t surface until May of 2017.

As the ground warms in spring, the wingless females will emerge and crawl up a nearby oak tree. In this asexual generation there is no need to mate. The females will inject eggs into expanding leaf buds. The small, round, larvae of the next generation include both males and females who chew into the leaf stems. Chemicals in their saliva stimulate the leaf tissue to swell. The galls continue to expand as the leaves and larvae grow, providing both food and shelter to the developing wasp.

These larvae pupate in late summer, and emerge as small, dark, male and female wasps to begin the cycle again. Once empty, the galls drop to the ground and dry out.

Just like the true apples we picked along the road, galls come in a diversity of colors and textures. There are over 50 species of wasps that produce oak apple galls in North America, and each wasp’s gall is slightly different. Most fall into two general groups – galls that have an airy web of fibers radiating from the central larval capsule, and galls that have juicy, spongy, fruit-like tissue. All galls made by Cynipid wasps would taste terrible, though, since they concentrate bitter tannic acid from the oak as a defense against fungi and bacteria.

The tart zing in my apples will also keep bacteria at bay – and taste great – once I preserve them as sauce. Oh autumn, you are the apple of my eye!

Photo by Steven Katovich, USDA Forest Service

Friday, September 18, 2015

Boundary Waters

Walking down to the lake one last time before heading to the tent, I couldn’t resist turning off my headlamp and looking up at the stars one last time, too. Here, in the Boundary Waters Canoe Area Wilderness of northern Minnesota, we are many miles from any significant light pollution. The dry, breezy September day had cleared humidity from the sky, too, resulting in a brilliant celestial show. Even familiar constellations were almost lost in the lavish abundance of light.

As I watched, I began to notice something else obscuring the stars. Just above the tree line, a gauzy haze had materialized. It swept around to the north, and dimmed a swath of the sky. I was puzzling at such a peculiar intrusion of clouds, when suddenly the haze developed two vertical bars. These weren’t clouds—they were northern lights!

Snapping my headlamp back on for expediency, I hurried back up the toe of granite toward our cluster of tents. John was already on his way down. “Northern lights!” I exclaimed as we passed. I shook Brenda and JoAnn’s tent gently, “The northern lights are out!” Ed was still reclining next to a few glowing embers in the fire grate. I could hear my dad rustling around in our tent, and see Jane’s light bobbing in hers. “Northern lights!”

One by one, our crew on the Natural History Paddle in the Boundary Waters picked their way down the campsite’s classic lakeside rock outcrop, and came to sit and stand at the water’s edge. Silently, we watched as the arc of greenish-white light rose and lowered, then split into two layers like a double rainbow. Dim vertical bars came and went almost imperceptibly. There were no wild dances, no flashing colors, just a demure display of physics above a gathering of new friends.

Before scientists discovered that solar winds cause the Aurora, many cultures created beautiful and fascinating stories to explain this mysterious phenomenon. Norse mythology tells of mounted warriors with light reflecting off their armor, and the massive ice of glaciers releasing stored energy. Chinese mythology imagines dragons’ fiery breath flashing across the sky. Others believe in spirits of ancestors dancing overhead, and reflections off ice at the North Pole.

In just the past 50 years, science has told us that the northern lights, or Aurora Borealis, are produced through an interaction between the Sun, the Earth’s magnetic field, and gasses in our atmosphere.

It begins with a coronal mass ejection (CME). The Sun ejects a stream of material, called solar wind. If it is aimed toward Earth, then the solar takes between one and four days to arrive at Earth. Once it arrives, the Earth’s magnetic field channels most of the electrically charged particles in the solar wind safely around the Earth.

Only where the magnetic field dives downward – near the North and South Poles – do the particles get close. Here, 50-200 miles up in our atmosphere, the electrons and other charged particles in the solar wind bump into oxygen and nitrogen molecules. Oxygen and nitrogen have their own electrons, which can gain or lose energy. So, when electrons from a solar wind bump into and transfer energy to oxygen and nitrogen, it boosts their electrons into a higher energy state. These “excited” electrons are unstable.

As an excited electron relaxes back to a more stable energy level, it releases energy in the form of a photon of light.  The size of the energy change determines the color of the light. As we relaxed back into a more stable energy level after the excitement of the day, perhaps we glowed a little bit, too.

Of course, none of us were thinking about the physics of our experience as we stretched our stiff legs and wiggled cold fingers. We were admiring the stars (still reflected in the rippling lake), anticipating the warmth of fluffy sleeping bags, and exhaling gratitude. Watching northern lights from a slab of bedrock in the Boundary Waters, canoes tucked safely into the trees nearby…is there any better way to spend an evening?

“I wondered…if anything—even knowing the physical truth—could ever change the beauty of what I had seen, the sense of unreality.  Indian warriors, exploding atoms, beds of radium--what difference did it make? What counted was the sense of the north they gave me, the fact that they typified the loneliness, the stark beauty of frozen muskegs, lakes, and forests. Those northern lights were part of me and I of them.” 
-- Sigurd Olson

The Aurora-watching rock was great for sunrise fishing, too. Photo by Larry Stone

Friday, September 11, 2015

Isle Royale: How did orchids get here?

“Rattlesnake!” I cried out as I stopped abruptly and shifted my pack so I could look down at the ground. Excitement (not fear) was surely evident in my voice, but not many people would recognize the source of that excitement. No snake, but several whorls of grayish-green leaves with white markings hid within the leaf litter along the Minong Ridge Trail on Isle Royale. The checkboard pattern that adorns the leaves is said to look like a rattlesnake’s mottled camouflage, while the broadly oval leaves are similar in shape to plantain leaves (a common plant of yards and disturbed areas). Together, these features resulted in the name “rattlesnake plantain orchid” for this beautiful little plant.

Throughout my hike on Isle Royale, I continued to see clusters of the three different species of rattlesnake plantain orchid along the trail, as well as several other less distinctive orchids, already past flowering. The family Orchidaceae is one of the two most diverse plant families (Asteraceae is the other), and contains more than 22,000 species across the globe. The flowers range from extravagantly beautiful to dinky and unobtrusive. Many orchids have evolved highly specialized pollination systems. Some look just like female bees, and attract amorous male bees to do their cross-pollinating. Many have special landing pads on their petals, and distinctive scents wafting out to entice visitors.

What fascinates me the most, though, is what happens after an orchid is pollinated. The seeds that form are almost microscopic, and over a million of them can fit into the capsule that develops from a single flower. Being so tiny, they lack an endosperm. This little packet of starches, oils, and proteins usually gives seeds the energy they need to germinate, grow their first leaves and roots, and get along until they can sustain themselves. Corn, beans, and squash are great examples of seeds with large energy reserves, and their seeds sustain us, too.

Orchids have found another way.

In order for a dust-like orchid seed to germinate, it must first be infected by a specific fungus. Not all orchids form a symbiosis (a close living relationship between two species, whether or not they both benefit) with the same fungus, but each orchid has just one fungal species, or maybe a few, that will work for it. The fungal mycelia provide the seed with sugar and nutrients in place of the endosperm. It is unclear if the fungus receives anything in return. The seeds can’t germinate without their fungus, except in lab conditions with a source of sugar. Once colonized, a baby orchid plant, called a protocorm, grows, and eventually produces leaves and roots. Some orchids never produce leaves or chlorophyll at all, and live out their days entirely parasitic on a fungus.

Knowing these basics of orchid germination, the question I’d been asking everyone and everything on the island baffled me even more: “How did you get here!?” How could these tiny, fragile seeds make such a long and treacherous journey, 14 to 20 miles across the lake, and then just happen to land where their friendly fungal partner was already established?

My amazement only deepened when I used the latrine near our Rock Harbor campsite for the first time. The educational poster on the inside of the door bragged that Isle Royale is home to 32 species of orchids. Thirty-two times--at least--over just several thousand years, this amazing coincidence happened. Wow.

When I shared my amazement with a mycologist friend, though, he was less impressed. “It’s almost inevitable,” he shrugged. As it turns out, the numerous, minuscule seeds of orchids are well-adapted to wind dispersal – in much the same way that pine pollen drifts on the breeze. That’s how orchids colonize tree trunks in the rainforest. Likewise, fungal spores are often wind-dispersed, even over many miles, and the species of fungi that orchids parasitize are quite common.

A little more research revealed that Ontario –the province just upwind of Isle Royale – has over 50 species of orchids on its mainland. So maybe 32 species on Isle Royale isn’t that impressive after all.

With this new information, my amazement at the simple fact of orchids being on Isle Royale shifted to admiration for the adaptations that brought them to the island in the first place, and the intricacies of their symbiotic relationships. Perhaps my question “How did you get here?” should refer not to the island, but to this moment in time, and the state of exquisite adaptation housed in a ground-hugging, snake-skin patterned cluster of grayish-green leaves.

How quietly, and not with any assignment from us, or even a small hint of understanding, everything that needs to be done is done. – Mary Oliver, Luna

Named for their supposed resemblance to the pattern on a rattlesnake’s skin, rattlesnake plantain orchids are a delight to encounter on the trail. How did they get here? Through millennia of adaptation.Photo by Emily Stone. 

Friday, September 4, 2015

Isle Royale: How did you get here?

We heaved our backpacks, loaded with high-energy foods, waterproof tents and warm clothing, onto the ferry dock just as the gray dawn was beginning to break. Waves crashed around the Voyageur II, and gusts of damp wind threatened to steal our hats. The ferry captain came out to greet us, passenger list in hand. We collectively expected him to say something like “All aboard!” Instead, with a bemused smile, he projected his voice over the bluster to the waiting crowd and said “We’re not going.”

At first there was just stunned silence, with a few hesitant chuckles, since he looked like he might appreciate a good joke. But he wasn’t joking, and neither was Lake Superior. Eight-foot waves and 30 mph gusts across a 20 mile expanse of cold, open water are nothing to mess with. “This is your one chance for a refund,” he said, “otherwise be here by 4:45 a.m. tomorrow.”

So, for plan B we headed up to the Grand Portage National Monument Visitor Center. The park ranger at the front desk didn’t miss a beat when we told him of our delayed departure to Isle Royale. “Welcome to a long tradition of people waiting at Grand Portage for good enough weather to start a journey on Lake Superior.”

The voyageurs who rendezvoused here every summer through the height of the fur trade era called Lake Superior “The Lady.” And this Lady makes her own rules. Icy water, big winds, and craggy rocks don’t make for safe or easy travel. Gardens of shipwrecks can attest to that. But rising out of the crystal clear water, 14 to 20 miles from shore, is a bit of an anomaly. Isle Royale, a 45 mile long and 9 mile wide bedrock island, is teeming with life that somehow made the treacherous journey.

The next morning, with the rough, rolling, cold, wet ferry ride behind us, we disembarked gratefully at the Windigo dock on the southwest corner of the island, joining the many lives already there. After cooking oatmeal in the campground, we hoisted our packs and started off down the trail.

Before long we met several pairs of hikers just ending their trips. We asked about their route on the island, their hometown, and which ferry they took. In essence, we asked “How did you get here?” Mostly they used the water route, but one couple arrived by air in a float plane. Historically, making winter crossings by dogsled was also common. Isle Royale is not an easy place to get to, or to get around, and yet life surrounded us on all sides. Soon I started asking “How did you get here?” to everything we saw.

While relatively few humans arrive on the island by air, many of the island’s wild residents and visitors arrived that way. The haunting wails of loons drifted up from every lake we passed. Chickadees chattered above us as we hiked, while flocks of cedar waxwings played follow-the-leader between berry-laden mountain ash trees. It’s not hard to imagine how the birds got here, or how the seeds of their favorite fruits got here either.

Fruit-bearing shrubs like chokecherry, mountain ash, and serviceberry are often pioneering species, since their seeds are air-dropped in a packet of fertilizer. The vibrant, red fruits of thimbleberry caught our attention, too, and supplemented our quick breakfast. Slowing down to pick berries left us open to attack, though, from the delicate mosquitoes who once made the dangerous crossing, too.

While the whine of mosquitoes was pleasantly rare, red squirrels scolded us incessantly. A water route seems like the only plausible explanation for the squirrels’ presence. Did the first squirrel on the island drift here on a fallen tree or raft of vegetation? What a frightening ride without a motor, rudder, rain gear, warm sweater, or pack full of food! How many attempted journeys failed – with no refund!? Now the red squirrels have been here so long – separated from the mainland population by that arduous journey – that they are considered their own subspecies: Tamiasciurus hudsonicus regalis.

Not just a scolding, but a crashing in the brush caught our attention. Through the dense spruce trunks we caught a glimpse of the hulking silhouette of a cow moose as she vanished into woods.  Moose are thought to have swum here from Canada around 1900 during a time of overpopulation on the mainland. And they didn’t have a bowl of warm oatmeal to greet them at the end. The trees they browse were here already, though, having colonized the island (by air or water?) starting shortly after the glaciers retreated 11,000 years ago.

Having sighted one of the iconic species of Isle Royale, we were now on the lookout for the other: wolves. Large, hairy scat on the trail signaled their presence, as did a few big, four-toed tracks among the boot prints on muddy trails. With only two or three wolves left on the island, that is more sign than I’d dared to hope for. Wolves likely crossed the ice bridge in the winter of 1948-49, and they helped stabilize the moose population for many years. Now wolves are suffering from inbreeding – one liability of living on an island – and the Park Service is exploring management options for both wolves and moose.

Air, water, ice. It is almost easier to imagine how the 1.1 billion year-old bedrock of this island came to be than to imagine how such a diversity of seemingly fragile organisms came to colonize it. Perhaps most telling is that not everything did make it. Bears, raccoons, skunks, porcupines, cottontails, and snapping turtles are notably absent. For humans, too, Isle Royale National Park is one of the least-visited parks in the country, and one of the most costly to visit (measured in time, money, and the discomfort of seasickness). Perhaps I’m biased, but I think that makes the creatures who do get there a little more special.

The cold, clear waters of Lake Superior separate Isle Royale and all its life from their counterparts on the mainland. The Lake makes the Island.

Red squirrels are one of the few small mammals that were able to make the treacherous crossing on Lake Superior and get to Isle Royale. By their incessant scolding, you’d think that they now own the place! Photo by Larry Stone.