Friday, February 13, 2015

A Naturalist's Thoughts on Invasive Species

Invasive species are defined as exotics that were brought or accidentally introduced to an ecosystem and wreak havoc on it because they have no native predators. Think kudzu in the American South.

A healthy ecosystem has checks and balances to keep each species in line. Visualize a very simple food cycle - let's say trees, white-tailed deer, black bear. Trees sprout and grow but the stand can't get too thick because of deer browsing the seedlings. The deer population is held in check by the bears. And the bears eat the berries on the trees and poop out the seeds, allowing new trees to grow.

Now, this is highly oversimplified, but you can see what I mean about checks and balances. You throw something non-native in the mix and the whole cycle suffers.

But it occurred to me yesterday that native species can become invasive. In reality, the simple food web that I described above doesn't work all that well where I live. Black bears (and other top predators) are rare and the white-tailed deer population has exploded. The understory of the forest here has almost no seedlings because the deer browse everything, leaving no baby trees to replace the ones that are sick or dying. 

In my opinion, white-tailed deer in the mid-Atlantic are an invasive species. Now, the very definition of an invasive species, at this point, implies that a species is non-native. But I would argue that when a native species population explodes out of control with nothing to check it, it's invasive too.

Interesting point of fact: not all exotics are invasive. Some, like the honeybee in the United States, were imported here and the local ecosystem adapted to them - and depend on them - over time.

 Honeybee on lavender
Photo credit: Ryan Wick, via Flickr (cc by 2.0)

Friday, February 6, 2015

A Naturalist's Thoughts on Winter Weather

February in the Mid-Atlantic can bring a wide range of weather - anything from sunny and balmy to freezing cold and snowy. This variability contributes to a wide range of winter precipitation. A wintry mix is a combination of rain, snow, freezing rain, and sleet.

Rain is liquid precipitation. The diameter of the droplets determines whether you have fog, mist, drizzle, light rain, moderate rain, heavy rain, excessive rain, or a cloudburst. Cloudburst droplets, although small at 2.85 mm in diameter, are over 200 times larger than fog droplets. (I wrote a previous post on this topic called How Big Are Raindrops?).

Snow consists of ice particles frozen into complex, six-sided patterns. Non-branching ice crystals - or diamond dust - form in the shapes of needles, columns, or plates.

Little Brother was very little when I took this photo of him playing in the snow.
He was very proud of his snowman!

Freezing Rain occurs when the atmosphere is warm enough for rain, but ground temperatures are 32 degrees F or lower. The rain freezes instantly when it hits the ground, coating everything in a layer of ice. Freezing drizzle is similar, but the individual drops of water are smaller. Freezing fog occurs when ice crystals are suspended in fog.

 I took this picture after an ice storm last winter. The rain froze the instant it hit the tree branches.

Sleet forms when snow melts in the atmosphere and then refreezes before it hits the ground. Sleet does not stick to objects the way freezing rain does.

This article (sans photographs) was first posted at the Audubon Naturalist Society. Come visit Woodend!

Friday, January 30, 2015

A Naturalist's Thoughts on Winter Nature Walks

In the northern hemisphere, the season of winter - with its freezing temperatures, muddy trails, and a dearth of wildlife - can be a difficult time to appreciate nature. Unlike the frenetic activity that occurs each spring, winter can seem downright boring by comparison. But if you take the time to experience nature in winter, you will find it a rewarding experience. Here are some tips for your next nature walk:  

Silence your phone. In this age of constant communication, it is hard to let go and experience the moment. Allow yourself some time to simply be in nature, without expecting anything from yourself or your surroundings.

Use your four senses. At first, you may notice human activities like helicopters buzzing overhead or cars idling in the parking lot. But the longer you listen, sounds of nature will capture your fancy: birdsong, leaves crackling under the weight of a squirrel, a light breeze through tree branches. Take a closer look at the downed trees, the dried grasses in the meadow, or the animal tracks in the mud or snow. Touch tree bark and the hulls of seed pods. Inhale deeply and smell the unique scents of nature. But please don't taste anything during a nature walk unless you are certain of what it is!

Savor your visit. Capture your moments of awareness by jotting them down in a nature journal, taking a photograph, or writing a poem or essay about your experiences.

This article was first posted at the Audubon Naturalist Society. Come visit Woodend!

Friday, January 23, 2015

A Naturalist's Thoughts on Animal Tracks in Winter

Winter, in the northern hemisphere, can be a hard time of year to spot mammals. Many are hibernating now or have significantly slowed their activities due to the cold. But fresh snowfall can lead to animal tracks, which is a fun way to study animals in winter. The following animals (and their tracks) are commonly found in the mid-Atlantic region of the United States. My thanks to vastateparksstaff for posting - and sharing - these great pictures online via Flickr (cc by 2.0). Note the use of a ruler - it's really helpful when trying to gauge the size of a print.

 White-tailed deer tracks
White-tailed deer tracks sometimes look like little hearts!

 Eastern Gray Squirrel tracks
This squirrel was running so fast that its front feet appear behind its hind feet!

HM Winter Visitors
Raccoon tracks

The text of this entry was first posted at the Audubon Naturalist Society. Come visit Woodend!

Friday, January 16, 2015

A Naturalist's Thoughts on Tree Rings

A tree is a woody plant with a single trunk that branches out at the top. Trees are perennial, meaning that they can live for many years. Tree height varies widely across the planet. Some California redwoods are more than 350 feet high, while the world's shortest tree, Greenland's dwarf willow, grows to be less than two and a half inches.

What causes tree rings?

The outer bark of a tree trunk consists of dead tissue, while the inner parts of the trunk are alive. New yearly trunk growth is added on between the inner old wood and the bark outside. Individual rings form because tree cells grow differently from the beginning to the end of a growing season. Each tree ring consists of two layers. A light-colored layer is formed when the tree grows rapidly in the spring; slower growth in the late summer and early fall causes a second, darker layer to form. Tree rings are only found in temperate climates. Tropical trees grow year-round, so they do not form rings.

When you look at a cross-section of a cut tree trunk, inner rings are the oldest. The rings' shape and width can tell you about the tree's life. Scars in the rings are usually caused by fire; if growth is limited by rainfall, wetter years tend to yield thicker rings. Narrow rings indicate tree stress, perhaps from drought or pests.
Pacific Spirit
Photo credit: Lawrence Murray, via Flickr (cc by 2.0)

This information was first posted at the Audubon Naturalist Society. Come visit Woodend!

Friday, January 9, 2015

Become a Master Naturalist!

You'll never look at downed trees the same way again!  
Recently, I earned my certification as a Maryland Master Naturalist. As part of this program, I took 60 hours of classes and instruction covering the ecology, geology, flora, and fauna of the state of Maryland. In order to keep my certification, I have to volunteer 40 hours a year and take 8 hours of refresher classes yearly. One way that I have been volunteering is to write up a short flyer each month for the Audubon Naturalist Society to post at their trail heads on the Woodend Nature Center sanctuary. I've decided to share these naturalist thoughts here in this blog on select Fridays.

Nearly every state in the US has a Master Naturalist Program. If you like spending time in nature, I encourage you to look into the training. I think it's a great opportunity for those of us who enjoy time outdoors. Here are a few reasons why:

- Training costs are low when compared with earning a similar certificate or degree.

- You meet lots of great eco-minded folks.

- You develop a greater appreciation and understanding of natural spaces around you.

- You'll have something new to add to your resume.

I developed a new appreciation for fungi as a part of my training. I used to always think of fungi as a sort of weird exception to plants. Nope! Fungi are totally different than plants and animals and have completely different life cycles and evolutionary strategies. Thinking about fungi has fueled some of my creative writing. :)

Thursday, September 18, 2014

Worthwhile diversions

Last Sunday, I went for a walk around the lake with my oldest child. Lake is a generous term for the neighborhood retention pond, but it's been in place for over 30 years and local wildlife have taken to it. 

During our walk, we crossed a bridge over a meandering stream. My son hopped down to the creek bed and began exploring. 

My first thought was that we didn't have time for this - I needed to get home to make dinner. My second thought was that we probably weren't supposed to be off the beaten path. But my third thought was hey, I wonder what's down there?

So, we went creeking. Without a dip net, it was hard to discover what lurked beneath the rocks and muck. But we still managed to find water striders, several schools of minnows, and three crayfish.

All in all, it was a very worthwhile diversion. And a nice way to bond in nature with my teen-aged son.