Deciduous Decisions

In the plant world there are two types of trees: deciduous and evergreen. Deciduous trees give us spectacular displays of fall color before shedding their leaves. Evergreens provide a shadow of summer with a splash of green during the bleak winter days. Both types of trees use the leaves (broad leaf or needle leaf) for photosynthesis, but obviously the deciduous tree evolved to opt out of photosynthesis during winter while the evergreens evolved to work a longer season. Which tree has the competitive advantage until the spring greenup?

Life in the wild is all about two things: making babies and being energy efficient. Depending on the environment and situation, being deciduous or evergreen offers a competitive advantage by saving energy, but of course it also comes at a price.

Deciduous trees typically live in areas with temperature fluctuations. Here in the northeast, we have a nice mix of deciduous trees: maples, oaks, hickories, poplars, and more. We also have four distinct seasons. Winters can be snowy, and for a tree that spreads it branches quite a distance from its trunk, not having leaves to catch a heavy snowfall could be the difference between losing limbs or not. Evergreens compensate for snowfall by having a conical shape and shorter branches, with the longest at the bottom. The branch structure allows snow to fall to the next level of branches relatively quickly.

Summer deciduous

While the loss of leaves saves branches, it costs the tree energy. A tree must have enough energy stored up for next spring’s new leaves by fall. Because photosynthesis uses energy (much like chewing and digesting your food burns calories), deciduous trees evolved to shed leaves when there is less sunlight, not enough to be worth the energy expense to generate some more energy. While the deciduous trees are standing idly through the winter, evergreens take advantage of their ever green leaves (either needles or broad leaves in the tropics) and photosynthesize for a longer season or year-round in the tropics. They gain a little more energy that way, and we’ll see why next.

Late fall deciduous

Those expendable deciduous leaves are fairly flimsy compared to a pine needle or palm frond, which are built to last. Less energy is required to build a full set of maple leaves than pine needles. More of the maple leaf is dedicated to photosynthesis than a pine needle, which needs more compounds for structure and defense. Unit for unit, a maple leaf generates more energy than a pine needle. Evergreens, conifers especially, use that conical structure to capture more sunlight to maximize energy production.

Summer evergreen conifers

Deciduous trees thrive in nutrient-rich soil. If there are plenty of nutrients to absorb, they can afford to shed leaves. They often draw remaining nutrients from the leaves back into the trunk before shedding leaves. They even contribute to the nutrient cycle with their fallen decaying leaves. Evergreens have adapted to nutrient-poor soil. They keep their leaves because of a lack of available nutrients. If you look at how green and full of life the tropical rainforests and dense forests of the Pacific Northwest are, you may be shocked at how poor the soil actually is. The nutrients are usually absorbed right out of the dead material into the upper layer of soil and into the living trees.

Winter evergreen conifers

The different leaf styles also lead to different strategies for water conservation. When stressed due to dry conditions, deciduous trees will shed their leaves early to stop water loss. During photosynthesis, water is drawn from the roots to the leaves to make it happen, and the trees exhale water vapor. Evergreens keep their leaves, but they have a waxy cuticle on them that helps prevent water loss.

Hopefully you have a better understanding of why trees do what they do. With fall here and winter on the way I think we can appreciate both leaf styles for the splashes of color they give us. How is the leaf situation in your neighborhood?
This week's information comes from an article by Frances C Smith in the journal Maine Naturalist. 
Frances C Smith: Smith, F. (1993). Evergreen vs. Deciduous Woody Plants: Which Wins Where. Maine Naturalist, 1(4), 205-212. doi:10.2307/3858181 

Migration

The days are getting shorter and cooler. Leaves are starting to turn and fall. Winter is approaching, and many animals are have already begun their seasonal migration. While some hibernate to avoid unfavorable seasonal habitat conditions, others move temporarily to more suitable habitat.

Migrations occur across all different animal classes: birds do it, and so do mammals, fish, insects, reptiles, amphibians, and crustaceans. Even some people do it. Florida and Arizona get plenty of snowbirds from up north every winter. More traditionally, nomadic tribes still exist in Africa and Asia living as they have for centuries.

We’re an ecology blog, not an anthropology blog so let’s forget about nomads for a minute. Perhaps the most visible migrations here in America are those of birds and monarch butterflies. Birds migrate to and from pretty much everywhere. Some stay within North America when migrating while others fly from pole to pole. Others, of course, are somewhere in between.

We’ll use the Baltimore oriole as an example of avian migration. They arrive in the eastern US from Central and northern South America in April and May. This is their breeding ground. They begin nesting right away and eggs usually hatch in June. Southern migration begins as early as July and has peaked by September.

Baltimore oriole (NPS)

Monarch butterflies journey to Mexico in a multi-generational migration. Northern monarchs go south to the oyamel fir trees in the mountains of central Mexico. Millions of them cover the trees. After winter, they head north again, laying eggs on milkweed plants. Caterpillars hatch in a few days and eat the plants before forming a chrysalis. A new butterfly emerges and continues the northward journey, stopping at milkweed to lay eggs and start the hatching and migrating process over again. The northernmost monarchs are able to return to Mexico in a single journey.

Monarch butterfly

The pronghorn in Wyoming migrates vertically. It moves from summer grounds in Grand Teton National Park about 150 miles south to lower elevation in the sagebrush habitats of the Green River area. This is North America’s longest mammal migration.

Pronghorn

Not all migration is seasonal. Zooplankton in the ocean migrate vertically through the water column on a daily basis. At night the move toward the surface, and by sunrise they are headed back to the briny deep. While a journey of hundreds or thousands of feet might not seem like much to you, keep in mind that these tiny critters probably can’t see as far as the other end of a yardstick.

Zooplankton (Nature International Journal of Science)

Fall migration is happening now. Who is moving through your neck of the woods?

This week's information comes from:

Journey North (Baltimore oriole)

National Geographic (monarch butterfly)

Wildlife Conservation Society (pronghorn)

Nature International Journal of Science (zooplankton)

Species of the Month

This month’s species of the month is a useful tree that provides sweets in the spring, shade in the summer, aesthetic enjoyment in the fall, and many manufactured products. The sugar maple is an important part of the natural world as well as an ornamental plant in cities and towns. Within the next few weeks they’ll be changing from verdant green to an explosion of color.

Sugar maple in its summer finest (The Spruce)

Scientific name: Acer saccharum

Kingdom: Plantae (plants)

Class: Magnoliopsida (dicots)

Order: Sapindales (flowering plants)

Range: Eastern US and Canada

Habitat: Moderately wet forest, occasionally drier slopes

Lifespan: 500 years

Diet: Water and sunlight

Predators: Deer, moose, snowshoe hares, squirrels, porcupines, humans

Conservation Status: No special protection

Sugar maple leaves (USDA)

Other Information: Sugar maple is the only tree suitable for the production of maple syrup. Nine or ten gallons of tree sap boiled down yields about a gallon of maple syrup. Deer, moose, and snowshoe hares browse the maple, while porcupines eat the bark. Squirrels, including the flying variety, eat seeds and buds. Many different songbirds build nests in the branches, while woodpeckers will nest in cavities. Bees will visit the flowers for pollen, even though pollen is spread by the wind. Aside from syrup, humans use sugar maple for wood. Furniture, flooring, and bowling pins are among the many maple products on the market. Leaves change color in fall before dropping. Colors vary by region but can be red, orange, or yellow. Some trees will have any combination of those colors rather than turning to just one. Leaf peeping in New England is a major tourism draw. You may recognize the sugar maple from the Canadian flag. Sugar maple seeds are in the fruit, which you probably played with as a kid. It's the little helicopters or you can make a mustache out of it. Information this week is from USDA. 

Sugar maple fruit (USDA)

Fall colors on display (Bartlett Tree Experts)

Geysers and Dolls

Geysers are a rare manifestation of the powerful volcanic forces that originate deep within Earth’s mantle. While volcanoes are widespread, geysers are more limited in where they can be found. There are about a thousand worldwide, with the highest concentration- roughly half- found in Yellowstone National Park.

Geyser at Yellowstone's Fountain Paint Pot

A volcano is sort of an opening to the mantle. Molten rock (magma) from the mantle is forced up to the surface by pressure periodically. Magma is also the driving force behind a geyser. Surface water trickles down through the soil and rock and collects in deep underground hot spots. Magma beneath the hot spot is what makes the spot hot. It superheats the water that collects there. Steam, heat, and pressure force the water back to the surface. After blasting to the surface, the water and steam continue surging up into the air. You’ve just witnessed a geyser erupting. The water falls back to the ground and percolates into the soil, starting the process over again. Most geysers erupt randomly, but a few run on a fairly predictable schedule. Most famous is Old Faithful, which erupts every 50 to 100 minutes, depending on local water conditions.

Geyser erupting at Yellowstone

Not all groundwater is forced to the surface so violently. Many times is flows gently as either a hot spring or the hotter boiling spring. If it is sufficiently dirty, you’ll see a bubbling mud pot. Sometimes only steam, not liquid water, hisses from the ground as a fumarole. Yellowstone has all of these geothermal features. Yellowstone is considered an active volcano, with the last eruption occurring about 600,000 years ago. Like the Hawaiian Islands, it sits over leaking magma in the middle of a tectonic plate. 

Fountain Paint Pot, a mud pot

Boiling spring at Yellowstone

Fumarole at Yellowstone

Dragon's Mouth hot spring at Yellowstone

Did you know? Some of Yellowstone's boiling springs are home to bacteria known as extremophiles that are adapted to live in extreme conditions. This week’s information comes from National Geographic and USGS.